Tropical eosinophilia

Tropical eosinophilia A human model of parasitic immunopathology, serum IgE levels before and after treatment Franklin A. Nevu, M.D., Allen P. Kopkrrn, Ph.D.,t Linda Gray, B.S., and 1. J. Danarc&

with observations

M.D., Gt&bmo M.D. Bet?ws&z,

on

PC&MO, .&fd.

The &verse olini.eal syrutromes characterized by a&hmatic symptoms, transient putmanary infllfrates, and eosinophilia have tended to obsczdre the SfMCific: @-%W&tion Of Serum IgE levels were detclmbed before of one s&b entity with @arid infections. and after therapy in a group of well-characterized patients with tropkd eos&ophiEia TOW mean serum IgE level in 14 cases before (TE), stndied earlier in Singapore. treatment with diethylcarbamazine wa8 d,S55 ng. per milliliter, with a trend bzlt statistically nonsign@cant deorease in levels to 600-1,000 ng. occzlrring 8 to 12 weeks after therapy. Leukocyte and eosinophil counts showed a rapid dabction after treatment, and although mean complement-fixing (CF) titers to Diro$larial antigen tended to deorease, they were not signijioantly redneed until 5 to 6 weeks. Tke h~istorioal development of evidence supporting the jiaarial etiology of TE was reviewed. @any tmsic questions engendered hy the ChiCd syndrome of tTopii%l eosinophilia make it an exoellent model for study of the immnnopathology of parasitic infections.

Considerable confusion continues to exist over the clinical entity referred to variously as tropical eosinophilia (TE) ,I, 2 eosinophilic lung (EL) ,a or pulmonary infiltrates with eosinophilia (PIE) .4 The confusion is twofold (1) as to what clinical features make up such an entity and (2) whether the entity is caused by a, single or by multiple etiologic agents. An additional source of perplexity stems from the paradoxical fact, that clinicians frequently employ the term tropiccd eosinophik in a loose sense; e.g., even modest degrees of eosinophilia in a.nyone with recent travel to the tropics, whereas parasitologists tend to apply the term in a more restricted sense to intense degrees of eosinophilia associated with parasitic infections. Considerable evidence that is summarized in the discussion has now accumulated, indicating that the full-Aedged syndrome of tropical eosinophilia is, indeed, a nosologic entity caused by filarial infections in which the host response prevents circulation of microfilariae. In fact, other names reflecting better understanding of the condition have been proposed, such as the term occ.ult f%~ia.Gs by Lie Kian Joe5 and more recently by Beaver,6 filartiia without micro~remin. Additional evidence supporting parasites, especially helminths, as the etiology for tropical eosinophilia has From Laboratories of Parasitic Diseases and Clinical Investigation of 1ustitut.e of Allergy and Infectious Diseasos, National Institutes of Health. Received for publication Feb. 28, 1975. Re rint requests to: Dr. F. A. Nova, Labortbtary of Parasitic? Diseases, NIATD, Bldg. 5, $0 om 114, National Institutes of Health, Bethesda, Md. 20014. tDr. Pacheeo, of the Laboratory of Par&tic Diseases, died in April, 1974. Vol. 55, No. 6, pp. 466-489

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been several reports of elevated serum IgE levels in patients with this disorder.?’ * In this paper observations are presented on serum IgE levels before and after treatment with diethylcarbamazine from a well-characterized group of patients with TE. The results of serial clinical laboratory data that helped establish the diagnoses by demonstrating responses to treatment are included. The development of knowledge and current concepts regarding TE are also briefly reviewed. MATERIALS AND METHODS Selection of patients Patients from whom sera were obtained were diagnosed and treated as eases of eosinophilic lung (tropical eosinophilia) in Singapore during 1961-1063 by Prof. T. J. Danaraj. We are indebted to Dr. Danaraj (currently Professor of Medicine, University of Malaya, Kuala Lumpur, Malaysia) for making the clinical material available to us. Criteria for diagnosis of TE or EL have been described in previous publications% 10 and included pulmonary symptoms for which no other cause could be determined in association with eosinophilia of >3,000 per cubic millimeter. Most cases had elevated levels of complement-fixing (CF) or indirect hemagglutinating (IHA) antibodies to antigens of adult Dirofilaria immitis, Ascaris, or hookworms, as has been reported previously. *I Repeated tests for circulating microfilariae in the TE patients were negative.

Serum collection,

storage,

and clinical

laboratory

tests

Serum samples were collected aseptically, mixed with Merthiolate to a final concentration of 1 :lO,OOO, and stored at -20” C. for not more than 1 or 2 weeks before use for CF tests. White blood counts and sedimentation rates were done by standard methods and eosinophil levels were determined by counting 200 white cells from stained thin blood smears and calculating absolute numbers from the per cent eosinophils x total white count. The CF tests for antibodies to an ethanol extract of adult Dirofilaria immitis were done by the Department of Pathology, General Hospital, Singapore, according to procedures described by Danaraj, da Silva, and Schacher.ie Mean CF titers were calculated and expressed as geometric means. In the lo- to 12-year interval between the time of collection of sera and their use for IgE determinations, sera were stored at -5” to -15” C.

Serum IgE determinations A radioimmunoassay procedure with commercially obtained reagents, the Phadebas IgE New Jersey), was used for determination test (Pharmacia Laboratories, Inc., Piscataway, of IgE levels. Serum samples were always diluted 1 to 10, and in some instances a higher dilution was prepared when unusually high IgE levels were encountered. A standard IgE preparation was always included with each test and IgE values in units per milliliter from the test were converted to nanograms per milliliter (units x 2.1) for presentation in the results. When multiple serum samples from the same individual were available, they were tested simultaneously for IgE levels. In those instances in which no end points were reached, maximum exact values were used in calculation of geometric mean IgE levels, such as 8,400 for > 8,400 nanograms per milliliter. As a result, the mean IgE levels presented somewhat underestimate true mean serum IgE levels. In the laboratory of one of the authors (A. K.) the normal mean -i 2 standard errors of serum IgE level is 180 + 28 ng. per milliliter.

RESULTS

Serum samples for IgE determinations were available pulmonary symptoms in 17 cases of tropical eosinophilia;

for 18 episodes of relapse occurred in

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Neva

WBC(O and Eoainophila ( 0 1 x 103/mm3

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40.

Sed. Rata mmlhr Dire-filarial CFTiter 5k-r--slO,OOO = lO,OCO~’ ” I. I Serum IgE nano-grams 1000 ; ’ ! per ml . lOO+30 I ,, I 4to-2 -1 Weeks Before

m

: . .

I 5 . . /

/ 1

Start of Diiybrbamazine -f-hwepy

I 2

.

3

I 4

/ 5 W&s

6 7 6 9 after Therapy Stanad

lOto

14to16

FIG. 1. Clinical laboratory values (ranges and means) in eosinophilic lung patients before and after diethylcarbamazine therapy. These are serial observations in 14 patients with 15 symptomatic episodes that were treated with diethylcarbamazine. For Dirofilarial CF titers and serum IgE levels, geometric means were calculated and are shown as horizontal bars. The CF titers are expressed as reciprocals of serum dilutions.

1 patient within 6 months after treatment. The IgE levels before treatment of these 18 episodes ranged from 357 to > 25,000 ng. per milliliter, with a geometric mean level of 3,115. Only 3 of the IgE serum values were less than 1,006 ng. per milliliter and the median level was between 2,500 and 4,600, Either serial or pre- and posttreatment serum samples were also available in 14 cases covering 15 symptomatic episodes to evaluate the effect of diethylcarbamazine treatment on IgE levels. The results, including CF antibody titers to Dirofilari.u. antigen as well as various other clinical laboratory determinations, are shown graphically in Fig. 1. %sage and duration of diethylcarbamazine therapy was 6 mg. per kilogram 3 times daily for 5 days. Earliest and most striking evidence of a response to treatment was reflected in the total white blood cell and eosinophil counts. Definite and roughly comparable reductions in both total leukocyte counts and eosinophils occurred within 1 week after diethylcarbamazine was started, and mean total white counts were within normal limits at 2 weeks after start of therapy. It is of interest that eosinophil counts still remained elevated in all cases as long as 10 to 16 weeks after therapy, with differentials generally in the range of 10 to 15 per cent. Serum IgE levels and CF antibody titers to Dirofilaria antigen also tended to come down after treatment, but in much less striking fashion than lenkooytes and eosinophils. The geometric mean levels for these two indicators at selected intervals before and after therapy, with statistical assessment of significance

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TABLE I. Serum

IgE and

before

diethylcarbamazine

and after

Dirofilarial

CF antibody

levels

in tropical

Time

Serum IgE (n&4

Serum CF

titer (reciprocal of dil.)

Mean No. of observations Range of observations P

eosinophilia

425

cases

therapy in weeks

relative

Before

Mean No. of observations Range of observations P*

eosinophilia

to therapy

After

1

2

4

5 to 6

Et09

2,355

2,120

2,324

4,021

644

979

10 357 to 15,540

8 200 to 10,080 >0.20

581goto 9,135 > 0.20

to 8,400 > 0.20

9 52 to 8,400 0.09

7 76 to 8,400 > 0.20

160

72

69

31

72

59

2::o 320

14 5 to 320 0.07

14 5 to 320 0.11

8 loto 80
20:o 320 0.10

9 loto 160 0.03

1,68i

lot0

12

*The probability that the posttreatment mean value did not differ from the pretreatment level, as determined by t test.

from pretreatment values, are presented in Table I. The slight drop in geometric mean CF antibody levels that occurred as early as 2 weeks after treatment was not statistically significant from the pretreatment level until 5 to 6 weeks and again 10 to 12 weeks after therapy. The reduction in geometric mean serum IgE level 8 to 9 weeks after start of treatment reached significance only at the 90 per cent level. DISCUSSION

Although there were scattered individual reports earlier,2 Frimodt-MGller and BartonI are generally credited with the first description in 1940 of the entity of hypereosinophilia, chronic cough, and miliary pulmonary infiltrates. Weingartenl sharpened the clinical description a few years later, first reported therapeutic response to arsenic, and applied the name tropical eosinophilia. In retrospect, however, a similar pathologic process resulting primarily in lymphadenopathy and hypereosinophilia with only occasional pulmonary manifestations was actually first recognized in Indonesia by Meyers and KouwenaaP in the late 1930’s. Moreover, these Dutch workers found microfilariae in the tissues affected by the intense eosinophilic reaction, and their observations were confirmed by others in Curacao of the Western hemisphere.14 GalliardX5 called attention to a mixed clinical picture of adenopathy, eosinophilia, and pulmonary symptoms in French military personnel repatriated from Southeast Asia. But it was not until 1962 that the eosinophilic adenopathy and presence of microfilariae in the tissues first noted by Dutch workers was linked to the pulmonary syndrome of tropical eosinophilia by Lie Kian Joe” and postulated to be different manifestations of the same basic process. Meanwhile, primary attention continued to be focused upon the asthmatic type clinical picture of tropical eosinophilia. A few cases were reported in

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Irnited States military personnel who had exposure to filarial infections in the South Pacific during World War II.‘“-‘x But the relationship of TE to filariasis was not emphasized until the discovery by l)utchl” and Tntlian”’ workers that was effective in treatment of 1110 the antifilarial drug, diethylcarbamazine, pulmonary syndrome. This led to the development of more critical criteria foi the diagnosis of 1’11: by Danaraj” and consequently a better evaluation of tht’ efficacy of diethylcarbamazine in treatment of the syndrome. The new criteria for clinical diagnosis of tropical eosinophilia focused specifically upon presumed filarial etiology but with an altered host response in the syndrome by including tests for the presence of antibodies to filarial antigens and for the absence of microfllariac in the blood of suspected c,ases.‘” As the circumstantial evidence linking tropical eosinophilia to filarial infection accumulated, additional efforts wore made to demonstrate a more direct relationship and to develop experiment,al evidence to support the association. The possibility that ?‘I< might represent human infection with a nonhuman tllarial parasite seemed reasonable in view of what. was known of other larval helmint,hs of animals failing to complet,e their development in man and eliciting tissue reactions, including eosinophilia.“, x This hypothesis gained further support by Buckley’s”:’ demonstration that one of two volunteers Jevelopcd cosinophilia. and pulmonary symptoms after infection wit,h Brz~& @MZ~~$, an animal filarid. But the need to incriminate animal filarial infections as a muse of ‘FE seemed less compel1 ill, ~7when Webb, .Job, a.ntl C;ault? were able to demonstrate microfilariae compatible with those of the human Wuchereriu. lung, of patients with bnncrofti in surgical specimens of tissues, including typical Tl3 in India. Similar findings in several patients from Singapore were also reported several years later by I)anara,j and associates,“5 further supporting the concept that infections with human filarial parasites could be responsible for the syndrome. Experimental work in dogs by Won@” was reported that favored the emerging hypothesis that. human 1’13 resulted from an immunologic host response to fllarial infection that trapped microfilariae in tissues instead of permitt,ing them to circulate in the blood. She found that certain dogs that had been immunized with microfilariac later failed to circulate microfilariae when given by transfusion, whereas the microfilariae continued to circulate in control animals. This work has recently been repeated and confirmed.“7 This brief story of tropical cosinophilia is still incomplete wit,h respect to some important details. For example, the striking prcdilcction of certain ethnic or racial types to the pulmonary type of TW has not been explained. While trapping of microfilariac primarily in the lungs instead of in lymph nodes might superficially explain the pulmonary vs. lymphatic clinical varieties of TE, the reasons for this differential localization are not known. Also, it should be remembered that although TE is most commonly associated with filariasis, certain other parasitic infections may at times produce an idcnticd clinical syndrome,’ differing only in failure to respond t,o diethylcarbama&ne. The finding of elevated serum IgE levels in patients with tropical eosinophilin might be expected in view of t,he frequency of asthma in this disorder and because TE involves a parasitic infection. Ezeoke, f’erera, and IIobbs’ were

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the first to report quantitative estimates of serum IgE in cases of tropical eosinophilia from Ceylon and north India. These authors. tested two different methods of radioimmunoassay, including the commercial kit used in our study, and found extremely high levels in all of 13 patients, with values ranging from 7,500 to 56,000 IU per milliliter. It is difficult to compare results expressed in units vs. nanograms without additional comparative data, but the IgE levels of cases reported by Ezeoke, Perera, and Hobbs’ appear to be higher and more consistently elevated than in our group of patients. These differences might be explained by the fact that serum samples for our study were initially collected 10 to 12 years ago in Singapore and may not have been consistently stored at subfreezing temperatures. We recently encountered a &year-old Indian boy who had spent the first 31/ years of life in a filariasis-endemic area of north India and presented with a typical clinical picture of tropical eosinophilia including a white blood count of 70,000 with 77% eosinophils, and a serum IgE of 6,600 ng. per milliliter. In another recent report,s elevated serum IgE levels in patients with tropical eosinophilia were observed utilizing immunoelectrophoresis rather than quantitative determination of IgE. The full significance of elevated IgE levels in tropical eosinophilia must await a better understanding of IgE response to parasitic infections in general. The association of IgE elevation with parasitic infections almost always involves helminths and implies the presence of worms in the tissues rather than in the lumen of the bowe1.28-30There are virtually no data relating IgE response to different stages of parasite development during human infections. For example, how soon after infection do IgE levels begin to change, when are maximum levels reached, and what pattern of persistence do they exhibit, These relationships have not been determined, particularly in those instances in which tissue invasion by the worm occurs during only one part of the parasite life cycle, such as with Ascaris and hookworm infections. In those helminthic infections characterized by continued presence of worms in the tissues, there is no information on whether IgE levels remain stable or fluctuate. In certain experimental infections of animals a great deal of information is available not only of the chronological sequence of IgE response, but also regarding functional significance of IgE.31 Many of the reports associating serum IgE evaluation with a specific parasite in man have involved subjects in whom multiple parasitic infections are impossible to rule out without continued and serial observations. The phenomenon of potentiation of IgE response,31 i.e., stimulation of IgE synthesis by heterologous antigens, may also complicate interpretation of IgE levels. In spite of these gaps in knowledge, some general conclusions can be drawn and pertinent questions raised in considering the significance of IgE levels in patients with tropical eosinophilia. Clearly, the IgE response in this clinical syndrome is extraordinarily high, but it is still not clear whether some individuals with filariasis and patent microfilaremia also have elevated IgE levels. Some indication that this may be the case are the reports of Radermecker and assoeiates30 and Spitz and associates,32 which included filariasis eases among parasitic infections checked for IgE levels. In both instances several filariasis

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cases had TgE levels of 2,500 to 12,000 ng. per milliliter. Unfortunately, additional information as to degrees of microfilaremia, presence or absence of pulmonary symptoms, and eosinophilia was not included. Therefore, since microfilariae are presumably being produced both in the filariasis patient with microfilaremia and in the occult case with TE:, disposal of microfilariae (antigen) must differ in the two situations. Does .IgE, alone or in concert with other immune responses, play a functional role in trapping or sequestering microfilariae in the tissues, and why does this reaction occur only in a minority of individuals with filarial infection? The striking degrees of peripheral tosinophilia and leukocytosis are not readily explained by the action of known chemotactic factors resulting from Igli: activity. However, substances elaborated by mast cells and/or basophils that have been sensitized by TgE and then exposed to appropriate filarial antigens might explain the asthma and pulmonary eosino philic infiltration that occurs in TE patients. We are currently attempting to determine whether specific filarial antigens can be incriminated in tropical eosinophilia as assessed by histamine release upon exposure of Ieukocytcs passively sensitized with scra from TE patients. If the etiology and pathogenesis of TE can be further delineated, it, would undoubt,cdly contribute to an increased understanding of immunopathology in other parasitic infections its well. of Allergy and Infectious We thank David W. Alling, M.D., of the Institute National Institutes of Health, for his assistance in statistical analysis of data, Anastasia Stanley for retrieval of records and specimens.

Disexses, and ldiSS

RWRREMES 1 Weingarten, R. J.: Tropical eosinophilia, Lancet 1: 103, 1943. 2 Donohugh, D. L.: Tropical eosinophilia. An etiologic. inquiry, X. Engl. J. Med. 269: 1357, 1963. of eosinophilic lung (tropical cosinophilia) with diethyl3 Dansraj, 1’. J.: Treatment carbamazinr, I’roc. Alum. Assoc. Malaya 9: 172, 1956. 4 Patterson, R., Irons, J. S., Kelly, J. F., Mattson, .J. R., and Oh, S. H.: Pulmonary infiltrates with eosinophilia, J. ALLERGY CLIN. IMH~!XOL. 53: 245, 1974. 5 Lie Kidn Joe: Occult filariasis: Its relationship with tropical pulmonar,y eosinophilia, Am. J. Trop. Med. Hyg. 11: 646, 1962. 6 Deaver, Y. C.: Filariasis without microfilaremia, Am. .J. Trap. M~tl. Hyg. 19: 181, 1976. 7 ‘Ezoke, A., Porcra, A. I3. V., and IIobbs, J. It.: Serum IgE rblevation with tropical eosinophilia, Clin. Allergy. 3: 33, 1973. 8 Prakash, N.: Increased circulating IgK in tropical eosinophilia, J. ALLERGY CLIN. IMMl:NOL. 53: 189, 1974. 9 Danaraj, T. J.: Treatment of eosinophilic lung (tropical eosinophilia) with diethylcarbamazinc, Quart. J. Med. 27: 243, 1958. 10 Danaraj, T. J., da Silva, I,. S., and Schacher, J. P. : Serological diagnosis of cosinophilic lung (tropical eosinophilia) and its etiologieal implications, Am. J. Trap. Med. IIyg. 8: 151, 1959. 11 Pacheeo, G., and Danaraj, T. J.: Indirect henmgglutination with extracts of various helminths in eosinophilic lung (tropical eosinophilia), Am. J. Trap. Med. Hyg. 15: 355, 1966. 12 Primodt-Miiller, C,, and Barton, II. M. : Pseudo-tuberculoua condition associated with eosinophilia, lndian Med. Gaz. 75: 607, 1940. 13 Meyers, F. M., and Kouwenaar, \V.: Over hypereosinophilie en over oen merkwaurdigen vorm van filariasis, Geneesk. Tijdschr. ‘h’ed.-Ind. 79: 853, 1939.

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14 Hartz, P. H., and van der Sar, A.: Tropical eosinophilia in filariasis. Occurrence of radiating processes about microfilariae, Am. J. Clin. Pathol. 18: 637, 1948. 15 Galliard, H.: Outbreak of filnriasis (W. ntalayi) among French and North African servicemen in North Vietnam, Bull. WHO 16: 601, 1957. 16 Hirst, W. R., and McCann, W. J. : Tropical eosinophilia; report of a case, Naval Med. Bull. 44: 1277, 1945. 17 Irwin, J. W.: Tropical eosinophilia, Ann. Intern. Med. 25: 329, 1946. 18 Levin, J. J.: Tropical eosinophilia (followed for seven years), Ann. Intern. Med. 44: 1264, 1956. 19 Wildervanek, A., Winckel, W. E. F., and Collier, W. A.: Tropical eosinophilia combined with histoplasmosis, Docum. Med. Geog. et Trop. 5: 67, 1953. 20 Ganatra, R. D., and Lewis, R. A.: Hetrazan in tropical eosinophilia, Ind. J. Med. Sci. 9: 672, 1955. 21 Beaver, P. C.: Parasitological review. Larva migrans, Exp. Parasitol. 5: 587, 1956. 22 Rosen, L., Chappell, R., Laqueur, G. L., Wallace, G. D., and Weinstein, P. P.: Eosinophilic meningoencephalitis caused by a metastrongylid lung-worm of rats, J. A. M. A. 179: 620, 1962. 23 Buckley, J. J. C.: Occult filarial infections of animal origin as a cause of tropical pulmonary eosinophilia, E. African Med. J. 35: 493, 1958. 24 Webb, J. K. G., Job, C. K., and Gault, E. W.: Tropical eosinophilia: Demonstration of microfilariae in lung, liver, and lymph nodes, Lancet 1: 835, 1960. 25 Danaraj, T. J., Pacheco, G., Shanmugaratnam, K., and Beaver, P. C.: The etiology and pathology of eosinophilic lung (tropical eosinophilia), Am. J. Trop. Med. Hyg. 15: 183, 1966. 26 Wong, M. M.: Studies on microfilaremia in dogs. II. Levels of microfilaremia in relation to immunologic responses of the host, Am. J. Trop. Med. Hyg. 13: 66, 1964. 27 Wong, M. M., Suter, P. F., Rhode, E. A., and Guest, M. F.: Dirofilariasis without circulating microfilariae: A problem in diagnosis, Am. Vet. Med. Assoc. 163: 133, 1973. levels in Ethiopian 28 Johansson, S. G. O., Mellbin, T., and Vahlquist, B.: Immunoglobulin preschool children with special reference to high concentrations of immunoglobulin E(TgND), Lancet 1: 1118, 1968. 29 Rosenberg, E. B., Whalen, G. E., Bennich, H., and Johansson, S. G.: Increased circulating IgE in a new parasitic disease-human intestinal capillariasis, N. Engl. J. Med. 283: 1148, 1970. 30 Radermecker, M., Bekhti, A., Poncelet, E., and Salmon, J.: Serum IgE levels in protozoa1 and helminthic infections, Int. Arch. Allergy Appl. Immunol. 47: 285, 1974. 31 Jarrett, E. E. E.: Keaginic antibodies and helminth infection, Vet. Rec. 93: 480, 1973. 32 Spitz, E., Gelfand, E. W., Sheffer, A. L., and Austen, K. F.: Serum IgE in clinical immunology and allergy, J. ALLERGYCLIN. IMMUNOL. 49: 337, 1972.