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Observations on immunity in relapsing fever and trypanosomiasis
1i9 TRANSACTIONS TROPICAL Vol. xxx.
OF THE ROYAL SOCIETY OF MEDICINE AND HYGIENE. No. 2. July, 1936.
OBSERVATIONS
ON
IMMUNITY IN RELAPSING TRYPANOSOMIASIS.”
FEVER
AND
BY HELEN Assistazt
Lecturer,
RUSSELL, Department
M.D.,
F.R.C.P.
Bacteriology,
(EDIN.).
University
of
Edinburgh.
This communication is concerned with some aspects of immunity in relapsing fever and trypanosomiasis, two infections which are common in tropical Africa. Trypanosomiasis is a protozoa1 disease and relapsing fever appears to occupy an intermediate position between what are considered the realms of They are not infections which are usually bacteriology and protozoology. studied together but they have characteristics in common which are interesting. Thus both may be described clinically as long infections showing periodic *This Medicine
paper was read and Hygiene.
before May,
the Edinburgh 1936.
Branch
of
the
Roya!
Society
of
Tropical
180
IMMUNITY
IN RELAPSING FEVER AND TRYPANOSOMIASIS.
exacerbations : in both recovery is not accompanied by immunity to reinfection : and both are amenable to treatment with synthetic aromatic compounds, specially those of arsenic. From the serological standpoint the interest in the two infections is that in both there is evidence that the infecting parasite is able to readapt itself-or to vary serologically-several times in the body of one host without any loss of pathogenicity in the variants. It may be said, on the whole, that the animal body is incapable of ridding itself of an infection with a pathogenic trypanosome, although an antibody reaction is manifest and lysins of low titre to many serological variants of the trypanosome appear one after another in the host’s serum as the infection proceeds. In relapsing fever the animal host does usually rid itself of the infection, but only after lysins of relatively high titre for several serological variants of the spirochaete have developed one after the other. So far as I am aware it has not yet been shown that serological variation of this kind in one host is a characteristic of bacterial infections, although that may depend merely upon the limits of present-day technique. In the realm of virus disease there is even less evidence that the infecting agents can readapt themselves serologically and remain pathogenic in the course of one infection. I propose to give a short summary of the work which has been done on the serology of relapsing fever and trypanosomiasis, and then to return to the question of variation, for in protozoa1 and allied infections it appears likely that the intractable type of the infections depends upon the fact that the invading parasite is an entity which is as adaptable as the host’s body cells which attempt to destroy it. RELAPSING
FEVER.
In 1868 in Silesia OBERMEIER (1873) saw a spirochaete in the blood of patients suffering from relapsing fever, and five years later when he found it again in cases in Berlin he published the observation. This spirochaete, Treponema recurruztis, was the first micro-organism to be associated definitely with disease in man and it was naturally a great source of interest to the early immunologists. It remained a source of much interest until the beginning of this century, when the pure culture technique of bacteriology was becoming established. Thus METCHNIKOFF (1887), studying leucocytes at the crisis of an attack of relapsing fever, saw macrophages ingesting the spirochaetes and claimed it as proof of the cellular theory of immunity. Later, GABRITCHEWSY (1896), mixing immune relapsing fever serum with living spirochaetes saw the latter disappear into unrecognisable granules and claimed the lytic action of the immune serum as support for the theory of humoral immunity. In the beginning of this century these theories of immunity were reconciled by the work of ERHLICH and others, and the evolution of the aromatic arsenic compounds provided a cure for relapsing fever which was astonishingly efficient.
181
HELEN RUSSELL.
Further, the difficulty of growing pathogenic spirochaetes outside the body was not overcome, and the interest in relapsing fever waned as it was driven back in Europe before the advance of sanitation. During the War, and the post-war refugee period, interest in relapsing fever revived with its reappearance in many parts of Europe and interesting JAN& (1918) observed that the spirochaetes papers belong to this period. of an attack of relapsing fever differed serologically from those of the relapses. In 1925, in India, CUNNINGHAM (1925) sh owed that at each relapse in any one animal the spirochaete is of a new serological type : he also demonstrated the alternation of types which occurs when the infection is passed on at a relapse to a new animal. Since then little that is new has been contributed to the serological study of relapsing fever. The writer (RUSSELL, 1931), working in the Gold Coast with the local louse-borne relapsing fever and Cricetomys gambianus, the pouched bush rat, as an experimental animal, confirmed CUNNINGHAM'S results. It was concluded that T. recurrentis had the capacity of producing several serological variants in one host, each variant being equally pathogenic. The limited number of variants which is detected in any epidemic was explained by the alternation of variants which occurs when the parasite reaches a new host who is not already immune to any variant : this alternation tending to keep certain variants predominant. CHART I.
1879 March
N.P.
Hindoo
ward
attendant.
CASE OF RELAPSING
(From “Spirillum
Fever”
by VANDYKE
CARTER,
FEVER.
Med. Chir. Trans. London
Ixiii.)
Chart I is included here to remind the reader of the clinical course of relapsing fever. It appears at first sight an ideal disease in which to study immunity. The acute stage of fever with parasitaemia, the crisis associated with the disappearance of the circulating spirochaetes and the appearance of a high
I~MMUNITY
182
IN
RELAPSING
FEVER
AND
TRYPANOSOMIASIS.
titre antibody, the inevitable relapse or relapses are all so well defined as to be dramatic. Chart II gives the details of the ordinary course of the fever in a
n =
I
spirochaetes
zzz spirochaetes
present. numerous.
A and B = type of spirochaete a, b and c = type of serum. t
=
day
on which
serum
tested.
series of C. gambianus ; and the disease in this rat is very similar to the human It shows the emergence of a new serological variant at each relapse, infection. and the appearance of a specific lysin for each variant in turn. If blood is passed to a new animal in the interval between attacks, and an infection is obtained in the new animal, the type of spirochaete is serologically the same as that which appears in the next relapse of the donor animal. That is what might be expected
HELEN
RUSSELL.
183
because some spirochaetes do survive in the intervals, although they are seldom seen in blood films, and those which survive must be new variants. Chart III shows the average titre of the lysin for the attack and first relapse spirochaetes Several of the rats of this group were re-examined in a series of C. gambianus.
I IN 40,960 I IN 20,480 I IN 10,240 I IN
5120
I IN
2,560
I IN
I,280
I IN
640
I IN
320
I IN
160
I IN
80
I IN
40
I IN
20
I IN
2
at intervals during the following years and it was found that after IS months to 2 years the lysin was sufficiently powerful to protect them from infection with the variants which had appeared in their original infections, but that they were susceptible to infection with any other variant. Chart IV demonstrates the alternation of variants which occurs when relapses are passed on to new animals. That is, that the relapse in the new animal is caused by spirochaetes serologically identical with the attack spirochaetes of the donor animal. This experiment was continued for 5 months before the seventh alternation was achieved, because the strain of relapsing fever available at that time had become weak and failed to relapse in many of the animals. The special interest in relapsing fever is in the ability of the spirochaete to readapt itself antigenically several times in one host without loss of pathoHowever, its possible variations in one host are limited because the genicity. D
184
IMMUNITY
IN
RELAPSING
FEVER CHART
Alternation A and B = type (m) Small black
of
of spirochaete. square = 1 day
AND
TRYPANOSOMIASIS.
IV.
types
of
passage.
when
spirochaetes
present
in blood.
infection does die out. That might be explained in one of two ways. The body of the host may produce gradually some antibody which is antagonistic to all spirochaetes, but there is no evidence of it so far as the ordinary laboratory technique can detect. On the other hand it is possible that a strain of spirochaete cannot readapt itself more than a few times to the changing serum of one host, and the process may be that of growing old in an ever changing environment.
HELEN RUSSELL.
185
TRYPANOSOMIASIS.
Trypanosomiasis came into the field of immunological study in the beginning of this century when bacteriological work was well established, and from the beginning it presented difficulties when compared with bacteriological work. No satisfactory method of growing pathogenic trypanosomes in vitro was or has been evolved, and there are difficulties in establishing and maintaining satisfactory strains in laboratory animals. The early workers appreciated that immunologically, trypanosomiasis constituted a more complicated problem than bacterial infections appeared to present at that date. FRANKE (1905) found that in monkeys infected with ma1 de caderas, trypanosomes were present in the circulation at the time when antibodies could be demonstrated, and he assumed that these trypanosomes were insensitive to antibodies. In the Nobel Lecture ERHLICH (1909) referred to this work and added the further observation of his school that many variants of trypanosomes could occur one after the other in one animal. The term “ serum-fast ” was applied to these relapse trypanosomes and it was assumed that they were variants whose avidity for certain chemical groupings had altered, as was known to occur in drug-fast variants of trypanosomes. RITZ (1916), from his work on experimental trypanosomiasis concluded that the capacity of trypanosomes to vary serologically was inexhaustible, and he used LEUPOLD (1928) found the term “ Rezidivstamme ” to describe the variants. that considerable variation appears even in the first relapses of animals identically infected with trypanosomes and inadequately treated. Trypanosomiasis, which is a slow disease in man, may be suitably studied in the rabbit in which the pathogenic strains run a chronic or subacute course. The parasitaemic rapidly fatal strains which develop in mice are less comparable with the disease in man. In the course of the infection in the rabbit trypanosomes are found from time to time in the circulation in small numbers and the skin symptoms and local oedemas progress slowly and certainly to a fatal end. During the last few days trypanosomes may be fairly numerous in the circulation. Chart V gives the details of an infection in two of a group of rabbits which the writer observed while working in the Liverpool School of Tropical Medicine in 1934. The rabbits were infected with a strain of T. rhodesiense and at weekly intervals mice were injected with blood from the rabbits ; at the same time each week some rabbit serum was stored in the ice chest in order that it could be It was found tested for lysins as soon as the mouse infections were positive.
186
IMMUNITY
IN
RELAPSING
FEVER
CHART
TITRE
OF TRYPANOCIDAL EACH
5 9 ‘i: s2 z ‘2 F q 3 B
T. rhodesiense Infecting Strain. -.--l_l------__ Before Infection 4th
2
‘;; E 2 c .i! “s g 5 n
IN
1
18
VARIAWTS
SEROLOGICAL
MICE
FROM
Day 10
TRYPANOSOMIASIS.
v.
FOR
ISOLATED
1 24
of 1
AND
DAY
I
Disease. 31
A.
B.
C.
D.
ON WHICH
50.29.
RABBIT
1
38
/
E.
i
45
1
54
Variants. None.
T. brucei.
T. equi?zw?l .
1 G.
0 --day
.3
2
ANTIBODY WAS
AND
----
0 __~----
--
24th ,, -___-----31st
))
38th
,,
1:64
1 : 64 -----w---Y---
45th
0
.-&-+------~___l___L_ I
I~-~-
0
1:64 ----______-~
0
0
,,
1:4 -....L--_---
-~____--54th
0
,,
I ---
80th ,sgth
--
0
,, ,,
Bayer,
250
mg.
per kilo
0 1
16 ,-:
___------Iy-I
I
1
I
l1:nl
that the rabbit serum removed each week contained lysins of low titre for the variant of trypanosome which had been isolated the week before but had no lytic effect on the variant which was present when it was withdrawn. It is likely that a week is not the best interval at which to attempt to isolate new variants, because in each of these two rabbits one attempt to obtain a variant in mice failed completely. There was also evidence, when the animals were very ill, that trypanosomes and some substance which destroyed them in vitro were present together in the serum. Chart VI (p. 188) re f ers to two other rabbits in which the lysin titre for the infecting variant of trypanosome only was recorded : it illustrates with
HELEN
CHART T. rhodesiense Infecting Strain. ___.~
18th ,, p_p-------’
A.
j
24
49.29.
of
Disease.
j
31
j
38
1
45
,
54
1 B. ---‘----ppp
C.
/ None.
1
E.
/
F.
’
G.
T. brucei.
T. equinum.
-I--
___----
-____
Tr. -----LI:64
; 1 : 64
--__ ~---
0 o
--
---~-,---I--
1 : 64 ______--~--___--1:64
1 38th ,, ____~-I_---__-~-_____________
0 ~
I 0
-I__ 0
0
I:4
45th ,, ____-__
--,--
--1 50 rnz. per
N.A.B.
54th ,, ~~----_______ ,,
18
RABBIT
0
24th ,, ~~,___-~~___---_-
80th
/
187
Variants. I_-_.
Before Infection --4th day -___~~-~ 10th ,, ~~---~-
V (coletimed). Day
10
RUSSELL.
I:161
1
1
/--kilo I
--
I 1: 16
--~___1: 16
----/_--:---
/ 1:16
Chart V how weak the lysin is, and shows incidentally that the commonly used drugs do not destroy the antigenic property of the trypanosomes. The technique used to detect lysins was that employed in the Liverpool School to assess the action of trypanocidal drugs, and consists in mixing a known number of living trypanosomes with the weakly immune serum and counting the survivors after some hours. It was found unnecessary to leave the mixtures for 24 hours which is the time chosen for reading the effect of drugs : the lytic antibody destroys the trypanosomes within 6 or 8 hours. Thus it appears that the course of an infection with a pathogenic trypanosome depends on the capacity of the trypanosome to vary serologically so often in the body of the host that it defeats the possible variations of t-he So the trypanosome strain is relatively immortal in its host’s defence. environment : many years ago LOEB (1913) said that the cancer cell had the same attribute.
185
IMMUNITY
IN
RELAPSING
FEVER
CHART
Rabbit
AND
TRYPANOSOMIASIS.
VI.
815.31
Rabbit
816.31.
__._ Day of Disease. 3efore
Titre
of
Infection
nfected
Lysin
for Variants
Infecting Trypanosome. not Studied.
0 T.
0 ___~
Thodesieme
lightly
T. rhodesiense -
4th
day
heavily ---
7th
>,
1:8 with 0.25 tryparper kilo 1 : 24
3th
,a
1 : 32
1 :32
lOth
,,
1 : 48
1 : 64
18th
,,
1 :32
1:
14th ,, -~-__--~___
1 : 32
1 : 12s+
.Ist
,,
1 :24
1 : 96
-8th
,,
1 : 16
1 : 64
Treated. grammes samide
Apparently
GENERAL
cured
1 : 12
1 } i
1 .32
I
64+
Died
CONSIDERATIONS.
We have seen therefore that there is evidence that the process of infection in relapsing fever and in trypanosomiasis is maintained by the periodic readaptation of an organism which has invaded the body. The process of resistance in the host, if investigated by ordinary methods for detecting antibodies, is marked by the development of lysins for each variant one after the other. In relapsing fever, which is a blood infection, the appearance of the variants of the spirochaete and the emergence of the corresponding antibody are very well defined and are associated with obvious clinical symptoms. Further, in relapsing fever, the number of spirochaetal variants which can appear in one host is limited. In trypanosomiasis, which is both a blood and a tissue infection, the variants of trypanosome appear one after the other without any great constitutional disturbance, and the number of variants which can appear in one host is limited apparently only by the death of the host. It is of interest to compare the serological variation of relapsing fever
HELEN RUSSELL.
189
spirochaetes and trypanosomes with the serological variation of bacteria. The work which has been published on bacterial variation within the last 15 years is immense and it is not within the scope of this paper to do more than to pick out a few of the observations in order to compare what is known of bacterial variation with the variation of spirochaetes and trypanosomes. In the Harben Lectures, ERHLICH commenting upon FRANKE'S description of the Rezidivstamme of trypanosomes remarked that the observation was probably of the greatest importance not only in bacteriology but also in all biology. It is not apparent that the variation of relapsing fever spirochaetes had been investigated by his school at that time, but the study of trypanosome variants was continued, as we have seen, by RITZ in 1916 and LEUPOLD in 1928. As we have seen also the serological variation of relapsing fever spirochaetes was reported by JANCS~ in 1918 and extensively worked out by CUNNINGHAM and his colleagues later. On the bacteriological side it may be said that the existence of bacterial variants was appreciated by PASTEURwho studied changes in virulence in anthrax and fowl cholera, but it was not until after the War that bacterial variation was appreciated in detail. In 1921 DE KRUIF (1921) demonstrated what he called the G and D types of Pasteurella lepiseptica. The D type of the bacillus was highly virulent and produced colonies which were culturally characteristic while the G type was comparatively harmless and showed other appearances on cultivation. About the same time ARKWRIGHT (1921) showed the variants of the coli-typhoid-dysentery group which he called rough and smooth because of the appearance of the colonies on culture medium, the change from the S to the R type being associated with a change in antigenic structure. Since this early work was published it has been shown that very many pathogenic organisms can undergo this type of variation, which is associated with a change in the appearance of growth in various culture media,, and with the loss of an antigenic constituent which determines pathogenicity. It has been found that the change from virulent or smooth to non-virulent or rough can be induced artificially in cultures. Adverse conditions of growth, such as changes of temperature and food supply, the presence of weak antiseptics or homologous immune serum, have all been shown to induce it in certain species. From the point of view of this paper the method of growing an organism in its own immune serum is the most interesting of the means by which serological variation has been induced. GRIFFITH (1923) demonstrated it in pneumococcus infection when he found that a pathogenic capsulated pneumococcus grown in homologous antiserum developed into a rough variant which had lost its type specific agglutinability and much of its pathogenicity. It appears that this variation is a little comparable with the variation which we have been considering in spirochaetes and trypanosomes for in both those infections the variant appears in the presence of homologous antibodies. However, the adaptability of the spirochaetes and trypanosomes is much greater than that of bacteria or cocci, for the variation occurs in viva and all the variants
190
IMMUNITY
IN
RELAPSING
FEVER
AND
TRYPANOSOMIASIS.
appear equally pathogenic and survive one after the other in the course of an infection in one host. So far as present-day knowledge goes we think of disease as caused by a great variety of small forms of life. At one end of the scale of living infective agents are the viruses, and the protozoa are at the other end, the bacteria are in an intermediate position, and any dividing lines which we may please to make are artificial but are an aid to memory. As the result of the serological work of the last half century it has become apparent that the degrees of immunity which the animal body can muster when invaded by these agents are very variable. On the whole, however, it appears that the smallest infective agents, the viruses, induce the most effective and long standing immunity, and they do not seem to be able to readapt themselves serologically in one host. The bacteria are less highly specific and induce less lasting immunity ; they vary serologically, but there is little experimental evidence that serological variation in one host is characteristic of bacterial disease, although the course of some prolonged bacterial infections suggests that variation in the presence of serum antibodies must occur. When we come to spirochaetes, taking relapsing fever as an example, the parasite can vary several times in presence of antibodies, and the appearance of immune bodies in the host is of less significance as evidence of immunity. In trypanosomiasis, an infection with a parasite enormously larger than a virus or bacterium, the infecting agent appears to be more adaptable than the host, and the detection of immune bodies loses the significance which is usually attached to it in the study of disease. To quote ERHLICH again, “ the struggle in disease lies between the adaptability of the parasite and that of the host, and the one whose adaptability is the highest remains the victor ” (Harben Lecture 2). ,Jn trypanosomiasis at least the adaptability of the parasite seems to be on a level with that of the host. REFERENCES.
J. A. (1921). J. Path. Bact., xxiv, 36. J. (1925). Trans. R. Sot. trop. Med. Hyg., xix, 11. H. (1921). g. exp. Med., xxxiii, 773. (1909). Beitriige ZUY Experimentellen Pathologie und Chemotherapie, Leipzig : Akademische Verlagsgesellschaft, m.b.H. FRANKE, E. (1905). Quoted by RITZ, H. (1916). Arch. Schiflsu. Tropenhyg., xx, 397. GABRITCHEWSKY, G. N. (1896). Ann. Inst. Pasteur, x, 630. GRIFFITH, F. (1923). Rep. Pub. Hlth. and Med. Sub., No. IS, 1, London: Ministry of Health. JANCS~, N. (1918). Zbl. Bakt. Orig., lxxxi, 457. LEUPOLD, F. (1928). 2. Hyg. InfektKr., cix, 144. LOEB, J. (1913). ArtificialParthenogenesis and Fertilisation. Chicago, U.S.A. : University of Chicago. METCHNIKOFF, E. (1887). Virchows Arch., cix, 176. OBERMEIER, 0. (1873). Cent. f. Med. Wiss., x, 145. RITZ, H. (1916). Arch. SchiIsu. Tropenhyg., xx, 397. RUSSELL, H. (1931). W. Afr. med. J., iv, 59. -. (1932). Ibid., vi, 1. ARKWRIGHT, CUNNINGHAM, DE KRUIF, P. EHRLICH, P.
OF THE ROYAL SOCIETY OF MEDICINE AND HYGIENE. No. 2. July, 1936.
OBSERVATIONS
ON
IMMUNITY IN RELAPSING TRYPANOSOMIASIS.”
FEVER
AND
BY HELEN Assistazt
Lecturer,
RUSSELL, Department
M.D.,
F.R.C.P.
Bacteriology,
(EDIN.).
University
of
Edinburgh.
This communication is concerned with some aspects of immunity in relapsing fever and trypanosomiasis, two infections which are common in tropical Africa. Trypanosomiasis is a protozoa1 disease and relapsing fever appears to occupy an intermediate position between what are considered the realms of They are not infections which are usually bacteriology and protozoology. studied together but they have characteristics in common which are interesting. Thus both may be described clinically as long infections showing periodic *This Medicine
paper was read and Hygiene.
before May,
the Edinburgh 1936.
Branch
of
the
Roya!
Society
of
Tropical
180
IMMUNITY
IN RELAPSING FEVER AND TRYPANOSOMIASIS.
exacerbations : in both recovery is not accompanied by immunity to reinfection : and both are amenable to treatment with synthetic aromatic compounds, specially those of arsenic. From the serological standpoint the interest in the two infections is that in both there is evidence that the infecting parasite is able to readapt itself-or to vary serologically-several times in the body of one host without any loss of pathogenicity in the variants. It may be said, on the whole, that the animal body is incapable of ridding itself of an infection with a pathogenic trypanosome, although an antibody reaction is manifest and lysins of low titre to many serological variants of the trypanosome appear one after another in the host’s serum as the infection proceeds. In relapsing fever the animal host does usually rid itself of the infection, but only after lysins of relatively high titre for several serological variants of the spirochaete have developed one after the other. So far as I am aware it has not yet been shown that serological variation of this kind in one host is a characteristic of bacterial infections, although that may depend merely upon the limits of present-day technique. In the realm of virus disease there is even less evidence that the infecting agents can readapt themselves serologically and remain pathogenic in the course of one infection. I propose to give a short summary of the work which has been done on the serology of relapsing fever and trypanosomiasis, and then to return to the question of variation, for in protozoa1 and allied infections it appears likely that the intractable type of the infections depends upon the fact that the invading parasite is an entity which is as adaptable as the host’s body cells which attempt to destroy it. RELAPSING
FEVER.
In 1868 in Silesia OBERMEIER (1873) saw a spirochaete in the blood of patients suffering from relapsing fever, and five years later when he found it again in cases in Berlin he published the observation. This spirochaete, Treponema recurruztis, was the first micro-organism to be associated definitely with disease in man and it was naturally a great source of interest to the early immunologists. It remained a source of much interest until the beginning of this century, when the pure culture technique of bacteriology was becoming established. Thus METCHNIKOFF (1887), studying leucocytes at the crisis of an attack of relapsing fever, saw macrophages ingesting the spirochaetes and claimed it as proof of the cellular theory of immunity. Later, GABRITCHEWSY (1896), mixing immune relapsing fever serum with living spirochaetes saw the latter disappear into unrecognisable granules and claimed the lytic action of the immune serum as support for the theory of humoral immunity. In the beginning of this century these theories of immunity were reconciled by the work of ERHLICH and others, and the evolution of the aromatic arsenic compounds provided a cure for relapsing fever which was astonishingly efficient.
181
HELEN RUSSELL.
Further, the difficulty of growing pathogenic spirochaetes outside the body was not overcome, and the interest in relapsing fever waned as it was driven back in Europe before the advance of sanitation. During the War, and the post-war refugee period, interest in relapsing fever revived with its reappearance in many parts of Europe and interesting JAN& (1918) observed that the spirochaetes papers belong to this period. of an attack of relapsing fever differed serologically from those of the relapses. In 1925, in India, CUNNINGHAM (1925) sh owed that at each relapse in any one animal the spirochaete is of a new serological type : he also demonstrated the alternation of types which occurs when the infection is passed on at a relapse to a new animal. Since then little that is new has been contributed to the serological study of relapsing fever. The writer (RUSSELL, 1931), working in the Gold Coast with the local louse-borne relapsing fever and Cricetomys gambianus, the pouched bush rat, as an experimental animal, confirmed CUNNINGHAM'S results. It was concluded that T. recurrentis had the capacity of producing several serological variants in one host, each variant being equally pathogenic. The limited number of variants which is detected in any epidemic was explained by the alternation of variants which occurs when the parasite reaches a new host who is not already immune to any variant : this alternation tending to keep certain variants predominant. CHART I.
1879 March
N.P.
Hindoo
ward
attendant.
CASE OF RELAPSING
(From “Spirillum
Fever”
by VANDYKE
CARTER,
FEVER.
Med. Chir. Trans. London
Ixiii.)
Chart I is included here to remind the reader of the clinical course of relapsing fever. It appears at first sight an ideal disease in which to study immunity. The acute stage of fever with parasitaemia, the crisis associated with the disappearance of the circulating spirochaetes and the appearance of a high
I~MMUNITY
182
IN
RELAPSING
FEVER
AND
TRYPANOSOMIASIS.
titre antibody, the inevitable relapse or relapses are all so well defined as to be dramatic. Chart II gives the details of the ordinary course of the fever in a
n =
I
spirochaetes
zzz spirochaetes
present. numerous.
A and B = type of spirochaete a, b and c = type of serum. t
=
day
on which
serum
tested.
series of C. gambianus ; and the disease in this rat is very similar to the human It shows the emergence of a new serological variant at each relapse, infection. and the appearance of a specific lysin for each variant in turn. If blood is passed to a new animal in the interval between attacks, and an infection is obtained in the new animal, the type of spirochaete is serologically the same as that which appears in the next relapse of the donor animal. That is what might be expected
HELEN
RUSSELL.
183
because some spirochaetes do survive in the intervals, although they are seldom seen in blood films, and those which survive must be new variants. Chart III shows the average titre of the lysin for the attack and first relapse spirochaetes Several of the rats of this group were re-examined in a series of C. gambianus.
I IN 40,960 I IN 20,480 I IN 10,240 I IN
5120
I IN
2,560
I IN
I,280
I IN
640
I IN
320
I IN
160
I IN
80
I IN
40
I IN
20
I IN
2
at intervals during the following years and it was found that after IS months to 2 years the lysin was sufficiently powerful to protect them from infection with the variants which had appeared in their original infections, but that they were susceptible to infection with any other variant. Chart IV demonstrates the alternation of variants which occurs when relapses are passed on to new animals. That is, that the relapse in the new animal is caused by spirochaetes serologically identical with the attack spirochaetes of the donor animal. This experiment was continued for 5 months before the seventh alternation was achieved, because the strain of relapsing fever available at that time had become weak and failed to relapse in many of the animals. The special interest in relapsing fever is in the ability of the spirochaete to readapt itself antigenically several times in one host without loss of pathoHowever, its possible variations in one host are limited because the genicity. D
184
IMMUNITY
IN
RELAPSING
FEVER CHART
Alternation A and B = type (m) Small black
of
of spirochaete. square = 1 day
AND
TRYPANOSOMIASIS.
IV.
types
of
passage.
when
spirochaetes
present
in blood.
infection does die out. That might be explained in one of two ways. The body of the host may produce gradually some antibody which is antagonistic to all spirochaetes, but there is no evidence of it so far as the ordinary laboratory technique can detect. On the other hand it is possible that a strain of spirochaete cannot readapt itself more than a few times to the changing serum of one host, and the process may be that of growing old in an ever changing environment.
HELEN RUSSELL.
185
TRYPANOSOMIASIS.
Trypanosomiasis came into the field of immunological study in the beginning of this century when bacteriological work was well established, and from the beginning it presented difficulties when compared with bacteriological work. No satisfactory method of growing pathogenic trypanosomes in vitro was or has been evolved, and there are difficulties in establishing and maintaining satisfactory strains in laboratory animals. The early workers appreciated that immunologically, trypanosomiasis constituted a more complicated problem than bacterial infections appeared to present at that date. FRANKE (1905) found that in monkeys infected with ma1 de caderas, trypanosomes were present in the circulation at the time when antibodies could be demonstrated, and he assumed that these trypanosomes were insensitive to antibodies. In the Nobel Lecture ERHLICH (1909) referred to this work and added the further observation of his school that many variants of trypanosomes could occur one after the other in one animal. The term “ serum-fast ” was applied to these relapse trypanosomes and it was assumed that they were variants whose avidity for certain chemical groupings had altered, as was known to occur in drug-fast variants of trypanosomes. RITZ (1916), from his work on experimental trypanosomiasis concluded that the capacity of trypanosomes to vary serologically was inexhaustible, and he used LEUPOLD (1928) found the term “ Rezidivstamme ” to describe the variants. that considerable variation appears even in the first relapses of animals identically infected with trypanosomes and inadequately treated. Trypanosomiasis, which is a slow disease in man, may be suitably studied in the rabbit in which the pathogenic strains run a chronic or subacute course. The parasitaemic rapidly fatal strains which develop in mice are less comparable with the disease in man. In the course of the infection in the rabbit trypanosomes are found from time to time in the circulation in small numbers and the skin symptoms and local oedemas progress slowly and certainly to a fatal end. During the last few days trypanosomes may be fairly numerous in the circulation. Chart V gives the details of an infection in two of a group of rabbits which the writer observed while working in the Liverpool School of Tropical Medicine in 1934. The rabbits were infected with a strain of T. rhodesiense and at weekly intervals mice were injected with blood from the rabbits ; at the same time each week some rabbit serum was stored in the ice chest in order that it could be It was found tested for lysins as soon as the mouse infections were positive.
186
IMMUNITY
IN
RELAPSING
FEVER
CHART
TITRE
OF TRYPANOCIDAL EACH
5 9 ‘i: s2 z ‘2 F q 3 B
T. rhodesiense Infecting Strain. -.--l_l------__ Before Infection 4th
2
‘;; E 2 c .i! “s g 5 n
IN
1
18
VARIAWTS
SEROLOGICAL
MICE
FROM
Day 10
TRYPANOSOMIASIS.
v.
FOR
ISOLATED
1 24
of 1
AND
DAY
I
Disease. 31
A.
B.
C.
D.
ON WHICH
50.29.
RABBIT
1
38
/
E.
i
45
1
54
Variants. None.
T. brucei.
T. equi?zw?l .
1 G.
0 --day
.3
2
ANTIBODY WAS
AND
----
0 __~----
--
24th ,, -___-----31st
))
38th
,,
1:64
1 : 64 -----w---Y---
45th
0
.-&-+------~___l___L_ I
I~-~-
0
1:64 ----______-~
0
0
,,
1:4 -....L--_---
-~____--54th
0
,,
I ---
80th ,sgth
--
0
,, ,,
Bayer,
250
mg.
per kilo
0 1
16 ,-:
___------Iy-I
I
1
I
l1:nl
that the rabbit serum removed each week contained lysins of low titre for the variant of trypanosome which had been isolated the week before but had no lytic effect on the variant which was present when it was withdrawn. It is likely that a week is not the best interval at which to attempt to isolate new variants, because in each of these two rabbits one attempt to obtain a variant in mice failed completely. There was also evidence, when the animals were very ill, that trypanosomes and some substance which destroyed them in vitro were present together in the serum. Chart VI (p. 188) re f ers to two other rabbits in which the lysin titre for the infecting variant of trypanosome only was recorded : it illustrates with
HELEN
CHART T. rhodesiense Infecting Strain. ___.~
18th ,, p_p-------’
A.
j
24
49.29.
of
Disease.
j
31
j
38
1
45
,
54
1 B. ---‘----ppp
C.
/ None.
1
E.
/
F.
’
G.
T. brucei.
T. equinum.
-I--
___----
-____
Tr. -----LI:64
; 1 : 64
--__ ~---
0 o
--
---~-,---I--
1 : 64 ______--~--___--1:64
1 38th ,, ____~-I_---__-~-_____________
0 ~
I 0
-I__ 0
0
I:4
45th ,, ____-__
--,--
--1 50 rnz. per
N.A.B.
54th ,, ~~----_______ ,,
18
RABBIT
0
24th ,, ~~,___-~~___---_-
80th
/
187
Variants. I_-_.
Before Infection --4th day -___~~-~ 10th ,, ~~---~-
V (coletimed). Day
10
RUSSELL.
I:161
1
1
/--kilo I
--
I 1: 16
--~___1: 16
----/_--:---
/ 1:16
Chart V how weak the lysin is, and shows incidentally that the commonly used drugs do not destroy the antigenic property of the trypanosomes. The technique used to detect lysins was that employed in the Liverpool School to assess the action of trypanocidal drugs, and consists in mixing a known number of living trypanosomes with the weakly immune serum and counting the survivors after some hours. It was found unnecessary to leave the mixtures for 24 hours which is the time chosen for reading the effect of drugs : the lytic antibody destroys the trypanosomes within 6 or 8 hours. Thus it appears that the course of an infection with a pathogenic trypanosome depends on the capacity of the trypanosome to vary serologically so often in the body of the host that it defeats the possible variations of t-he So the trypanosome strain is relatively immortal in its host’s defence. environment : many years ago LOEB (1913) said that the cancer cell had the same attribute.
185
IMMUNITY
IN
RELAPSING
FEVER
CHART
Rabbit
AND
TRYPANOSOMIASIS.
VI.
815.31
Rabbit
816.31.
__._ Day of Disease. 3efore
Titre
of
Infection
nfected
Lysin
for Variants
Infecting Trypanosome. not Studied.
0 T.
0 ___~
Thodesieme
lightly
T. rhodesiense -
4th
day
heavily ---
7th
>,
1:8 with 0.25 tryparper kilo 1 : 24
3th
,a
1 : 32
1 :32
lOth
,,
1 : 48
1 : 64
18th
,,
1 :32
1:
14th ,, -~-__--~___
1 : 32
1 : 12s+
.Ist
,,
1 :24
1 : 96
-8th
,,
1 : 16
1 : 64
Treated. grammes samide
Apparently
GENERAL
cured
1 : 12
1 } i
1 .32
I
64+
Died
CONSIDERATIONS.
We have seen therefore that there is evidence that the process of infection in relapsing fever and in trypanosomiasis is maintained by the periodic readaptation of an organism which has invaded the body. The process of resistance in the host, if investigated by ordinary methods for detecting antibodies, is marked by the development of lysins for each variant one after the other. In relapsing fever, which is a blood infection, the appearance of the variants of the spirochaete and the emergence of the corresponding antibody are very well defined and are associated with obvious clinical symptoms. Further, in relapsing fever, the number of spirochaetal variants which can appear in one host is limited. In trypanosomiasis, which is both a blood and a tissue infection, the variants of trypanosome appear one after the other without any great constitutional disturbance, and the number of variants which can appear in one host is limited apparently only by the death of the host. It is of interest to compare the serological variation of relapsing fever
HELEN RUSSELL.
189
spirochaetes and trypanosomes with the serological variation of bacteria. The work which has been published on bacterial variation within the last 15 years is immense and it is not within the scope of this paper to do more than to pick out a few of the observations in order to compare what is known of bacterial variation with the variation of spirochaetes and trypanosomes. In the Harben Lectures, ERHLICH commenting upon FRANKE'S description of the Rezidivstamme of trypanosomes remarked that the observation was probably of the greatest importance not only in bacteriology but also in all biology. It is not apparent that the variation of relapsing fever spirochaetes had been investigated by his school at that time, but the study of trypanosome variants was continued, as we have seen, by RITZ in 1916 and LEUPOLD in 1928. As we have seen also the serological variation of relapsing fever spirochaetes was reported by JANCS~ in 1918 and extensively worked out by CUNNINGHAM and his colleagues later. On the bacteriological side it may be said that the existence of bacterial variants was appreciated by PASTEURwho studied changes in virulence in anthrax and fowl cholera, but it was not until after the War that bacterial variation was appreciated in detail. In 1921 DE KRUIF (1921) demonstrated what he called the G and D types of Pasteurella lepiseptica. The D type of the bacillus was highly virulent and produced colonies which were culturally characteristic while the G type was comparatively harmless and showed other appearances on cultivation. About the same time ARKWRIGHT (1921) showed the variants of the coli-typhoid-dysentery group which he called rough and smooth because of the appearance of the colonies on culture medium, the change from the S to the R type being associated with a change in antigenic structure. Since this early work was published it has been shown that very many pathogenic organisms can undergo this type of variation, which is associated with a change in the appearance of growth in various culture media,, and with the loss of an antigenic constituent which determines pathogenicity. It has been found that the change from virulent or smooth to non-virulent or rough can be induced artificially in cultures. Adverse conditions of growth, such as changes of temperature and food supply, the presence of weak antiseptics or homologous immune serum, have all been shown to induce it in certain species. From the point of view of this paper the method of growing an organism in its own immune serum is the most interesting of the means by which serological variation has been induced. GRIFFITH (1923) demonstrated it in pneumococcus infection when he found that a pathogenic capsulated pneumococcus grown in homologous antiserum developed into a rough variant which had lost its type specific agglutinability and much of its pathogenicity. It appears that this variation is a little comparable with the variation which we have been considering in spirochaetes and trypanosomes for in both those infections the variant appears in the presence of homologous antibodies. However, the adaptability of the spirochaetes and trypanosomes is much greater than that of bacteria or cocci, for the variation occurs in viva and all the variants
190
IMMUNITY
IN
RELAPSING
FEVER
AND
TRYPANOSOMIASIS.
appear equally pathogenic and survive one after the other in the course of an infection in one host. So far as present-day knowledge goes we think of disease as caused by a great variety of small forms of life. At one end of the scale of living infective agents are the viruses, and the protozoa are at the other end, the bacteria are in an intermediate position, and any dividing lines which we may please to make are artificial but are an aid to memory. As the result of the serological work of the last half century it has become apparent that the degrees of immunity which the animal body can muster when invaded by these agents are very variable. On the whole, however, it appears that the smallest infective agents, the viruses, induce the most effective and long standing immunity, and they do not seem to be able to readapt themselves serologically in one host. The bacteria are less highly specific and induce less lasting immunity ; they vary serologically, but there is little experimental evidence that serological variation in one host is characteristic of bacterial disease, although the course of some prolonged bacterial infections suggests that variation in the presence of serum antibodies must occur. When we come to spirochaetes, taking relapsing fever as an example, the parasite can vary several times in presence of antibodies, and the appearance of immune bodies in the host is of less significance as evidence of immunity. In trypanosomiasis, an infection with a parasite enormously larger than a virus or bacterium, the infecting agent appears to be more adaptable than the host, and the detection of immune bodies loses the significance which is usually attached to it in the study of disease. To quote ERHLICH again, “ the struggle in disease lies between the adaptability of the parasite and that of the host, and the one whose adaptability is the highest remains the victor ” (Harben Lecture 2). ,Jn trypanosomiasis at least the adaptability of the parasite seems to be on a level with that of the host. REFERENCES.
J. A. (1921). J. Path. Bact., xxiv, 36. J. (1925). Trans. R. Sot. trop. Med. Hyg., xix, 11. H. (1921). g. exp. Med., xxxiii, 773. (1909). Beitriige ZUY Experimentellen Pathologie und Chemotherapie, Leipzig : Akademische Verlagsgesellschaft, m.b.H. FRANKE, E. (1905). Quoted by RITZ, H. (1916). Arch. Schiflsu. Tropenhyg., xx, 397. GABRITCHEWSKY, G. N. (1896). Ann. Inst. Pasteur, x, 630. GRIFFITH, F. (1923). Rep. Pub. Hlth. and Med. Sub., No. IS, 1, London: Ministry of Health. JANCS~, N. (1918). Zbl. Bakt. Orig., lxxxi, 457. LEUPOLD, F. (1928). 2. Hyg. InfektKr., cix, 144. LOEB, J. (1913). ArtificialParthenogenesis and Fertilisation. Chicago, U.S.A. : University of Chicago. METCHNIKOFF, E. (1887). Virchows Arch., cix, 176. OBERMEIER, 0. (1873). Cent. f. Med. Wiss., x, 145. RITZ, H. (1916). Arch. SchiIsu. Tropenhyg., xx, 397. RUSSELL, H. (1931). W. Afr. med. J., iv, 59. -. (1932). Ibid., vi, 1. ARKWRIGHT, CUNNINGHAM, DE KRUIF, P. EHRLICH, P.