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cyclophosphamide) in dogs
Br. uet. ]. (1990). 146, 249
IMMUNOCHEMOTHERAPY (THYMOSTIMULIN/CYCLOPHOSPHAMIDE) IN DOGS
J. A. MONTOYA, E. M. MARTfNEZ, M. RODRfGUEZ and S. PEREZ-CUADRADO· Dpto. de Patologia Animal, Facultad de Vetennana, 28040 Madrid, Spain; "Dpto. de Inmunopatologia, Instituto Oncoltfgico de Madrid, 28040 Madrid, Spain
SUMMARY This article demonstates the positive effect of thymostimulin (TP-l) on leucolymphopoiesis in dogs, based on its apparent ability to counteract the immunodepression induced by cyclophosphamide chemotherapy. Thymestimulin administered to healthy cyclophosphamide-treated dogs prevented the initial drop in the values of leucocytes and lymphocytes due to the chemotherapy and restored these values to the higher levels existing before the treatment. In a control group given a placebo instead of TP- 1, the immune depression provoked by cyclophosphamide was maintained during all the therapeutic cycles
INTRODUCTION Recent advances in biotherapy provide a new perspective on controlling malignant disease, either directly or indirectly, through immunological methods. The detection of tumour associated antigens (TAA) which differ, at least quantitively, from antigens present in normal tissues, provides a rational basis on which to establish classical selective immunotherapy and, on occasions, as in the case of tumour specific antigens (TSA), specific immunotherapy (Craig, Richardson & Rudd, 1986). During the evolution of a neoplastic disease, the body's natural defences, represented by T- and B-Iymphocytes, NK cells and macrophages, are normally lowered, while the activity of the suppressor cells and the blocking antibodies increase, facilitating the tumour's establishment and growth. Along with this imbalance in the tumour-host relationship, there is a secondary immunodeficiency due to conventional cancer treatment which may include surgery, radiotherapy and chemotherapy. The fourth mode of tumour therapy, immunomodulation, seeks to correct this immunological deterioration in the host's favour, providing it with an efficient tumour immunosurveillance capacity (Theilen & Madewell, 1987). Biotherapy based on the use of biological response modulators (BRM) seeks, by various means, to stimulate or restore the host's lowered immune response and increase the efficiency of the antitumour response's effector mechanism themselves (Jeglum, 1985).
250
BRITISH VETERINARY JOURNAL, 146, 3
Biotherapy can also be useful in treating bacterial or viral illnesses which lower the host's immune response as they evolve and which represent an important branch within veterinary medicine. Cyclophosphamide (Cy) is an alkylating, cytotoxic drug belonging to the nitrogen mustard group. Its effect is to break up DNA molecules or induce inappropriate crossingover, thereby interfering with replication and transcription. This anticancer agent is frequently used in cases of lymphoproliferative diseases and solid tumours, and brings about a serious myelodepression which is reflected in leucopenia, lymphopenia, thrombocytopenia and anaemia (Craig tJ al., 1986; Theilen & Madewell, 1987). Thymostimulin, a BRM pertaining to the thymic hormones and extracts group, obtained from calves' thymus glands, restores the body's immune response, as shown by the normalization of T-Iymphocyte activity, and for inducing the differentiation and maturation of the precursors of the immunocompetent cells. In certain cases, thymestimulin's effect on lymphopoiesis and T-cell activity has been shown to be sufficient to overcome the immunodepression induced by chemotherapy (Martelli & Velardi, 1982; Bernengo & Fra, 1983), thereby justifying its use in anticancer immunochemotherapy protocols. In this article, thymostimulin's immunorestoration capacity has been assessed, contrasting it with cyclophosphamide's immunodepressant effect in healthy dogs . Our aim was to reach clear conclusions which would allow us to employ this kind of treatment in animals with tumours, and to extrapolate the information thus obtained for use in human medicine.
MATERIALS AND METHODS Seven crossbred dogs of both sexes (five males and two females) were used. They ranged between 4 and 5 years of age and 25 and 30 kg in weight. The experimental method employed involved ' in-vivo' stimulation and ' in-vitro' evaluation of the results. The animals were divided in two experimental groups: group 1, the control or placebo group, consisted of three dogs (two males and one female), and the drug-testing group, group 2, consisting of four dogs (three males and one female). The chemoimmunomodulation protocol followed that used by Carda tJ al: (1986), and involved six consecutive 21-daylong therapeutic cycles. On the first day (day 0) of each cycle animals in both groups received a massive intravenous dose (15 mg/kg of body weight) of cyclophosphamide (Genoxal, Lab. Funk, S.A.). On the second, ninth and sixteenth days of each cycle the four dogs in the test group 2 were each given an intramuscular injection (0' 5 mg/kg of body weight) of thymostimulin (TP-1, Lab. Serono, S.A.), while each of the control dogs (group 1), received the same volume of isotonic saline solution (placebo) instead ofTP-1 (Table I). On three occasions during the 2 weeks prior to the start of the experiment venous blood was taken from the cephalic vein to permit a systematic study of the blood cells; sam ples for the same purpose were taken on days 0 (21), 2, 9 and 16 of each of the study's six treatment cycles. A Coulter'S plus' haematological cell counter was used to determine the number of erythrocytes, platelets and leucocytes present in whole blood collected in EDTA 2 and lymphocyte counts were made from flesh blood smears stained by the May-Grilnwald-Giemsa method. The STAT-1-30 A (hp)- 't ' statistic for two means was used to analyse the results.
IMMUNOCHEMOTHERAPY IN DOGS
251
Table I Therapeutics cycles (TP-l/Cy) Groups
Days 2
0
16
9
21 (0)
t
(control) 2 (test)
Cy
Placebo
Placebo
Placebo
Cy
Cy
TP·t
TP·t
TP-t
Cy
Cy, cyclophosphamide administered; TP-l, thymostimulinadministered.
RESULTS The total number of leucocytes and lymphocytes in each of the groups are summarized in Figs 1, 2 and 3. The results were recorded as the average number of leucocytes and lymphocytes in each treatment cycle in relation to the base level, which in tum was the average of the values calculated in all the dogs before the start of therapy (11'293 leucocytes/mrrr' (100%) and 1'832Iymphocytes/mm3 (100%). This 100% is represented in the figures as the baseline. The analysis of the results revealed important significant differences between test group 2 and placebo group 1. 160 140 ,!!
!..120
~
j ~ 100" ~
o &
~ Baseline
=c..._
80 60
To I
o Conlrol group1leucocyles • Test group 21eucocyles
I
I
2 3 4 Therapeutic cycles
I
I
5
6
Fig. 1. Relative mean valuesof the total number of leucocytes throughout the treatment. The relative mean values of the total number of leucocytes throughout the treatment (Fig. 1), showed an initial drop in both groups during the first cycle (90% in group 2 and 91% in group 1); the leucocyte model was almost identical in both groups as regards the magnitude of each fall after the initial dose of cyclophosphamide (secondary leucopenia subsequent to chemotherapy) during the first two treatment cycles. This initial leucopenia increased and persisted in placebo group 1 during the third and fourth cycles (values of 82% and 86%, respectively), while in the test group 2, treated with thyrnostimulin, the number of leucocytes reached normal levels in the third (98%) and fourth
252
BRITISH VETERINARY JOURNAL, 146, 3
(99%) cycles. During the fifth treatment cycle, both groups showed a transitory recovery in the number ofleucocytes, although the values were higher in test group 2 (120%) than in placebo group 1 (107%). Another drop in the leucocyte count occurred in the sixth and last cycle: the numbers in placebo group 1 fell below the base level (92%), while those of test group 2, treated with TP-l, were maintained at base level (100%). The lymphocyte count (Fig. 2) also showed an initial fall in both groups during the first cycle (89% in the placebo group 1 and 90% in the test group 2). The decrease became more apparent in the second cycle, both in the placebo and in the test group (77% and 82%, respectively). The values remained practically unchanged in placebo group 1 until the end of the study: 78% in the third cycle, 79% in the fourth, 82% in the fifth and 80% in the sixth and last cycle. In contrast, in the group treated with thymostimulin, there was a progressive rise in the average number of lymphocytes from the third cycle (96%) onwards, surpassing base level values in the last two cycles (111% and 112%, respectively). 160 140 ~
..
-120 III
::>
~ 100t-.......::----------=---~L----Basehne
~
:2 eo ~
o Control\lroup1 lymphocytes • Test \Iroup2 lymphocytes
60
2
3
4
5
6
Therapeutic cycles
Fig. 2. Relative mean values of the total number of lymphocytes throughout the treatment.
160 r~
140
~ 120 ~
l/l
~
~
~~-
/~
/-~
o-....._,"--O-_---~
100 ~ /~ - ---------- ------- ~ --Baseline
eo
0::
o Lymphocytes test group 2/lymphocytes conlrol\lroup1 • Leucocytes tesl\lroup 2/ leucocytes controlgroup1
60
o
234
5
6
Therapeutic cycles
Fig. 3. Comparative study of the average leucocyte and lymphocyte values throughout the treatment.
IMMUNOCHEMOTHERAPY IN DOGS
253
The percentage ratio of leucocytes and lymphocytes in the two groups showed considerable differences between the groups throughout the study (Fig. 3). The ratio between the average number ofleucocytes in group 2 and the average number in placebo group 1 was noticeably higher than the base levels from the second cycle onward (103%); it reached peak value in the third cycle (120%), falling slightly afterwards and maintaining the difference in the fourth, fifth and sixth cycles (115%, 112% and 109%, respectively). The ratio of the average number of lymphocytes in test group 2 compared with the average number in placebo group 1 was even higher. A value of 124% in the third cycle was followed by greater values in each cycle, reaching 136% in the fifth and 141% in the sixth and last cycle. The difference between the average number oflymphocytes in both groups was statistically significant in the sixth cycle (ir20117 lymphocytes/rnm' (SE: ± 175); i t - 1°506lyrnphocytes/mrrr' (SE: ± 157); t-206; dj-26; P<0002).
DISCUSSION
The results revealed that both groups had a similar leucocyte model in relation to the secondary leucopenia due to treatment with cyclophosphamide. Nevertheless, in the untreated placebo group 1, the drop in the number of leucocytes was progressive until the fourth chemotherapeutic cycle, after which there was a slight natural leucocyte 'rebound', with values which slightly surpassed the base level in the fifth cycle (107%). The number fell again to below normal levels (92%) in the sixth cycle. On the other hand, after the initial leucocyte level drop experienced by both groups during the first and second cycles, the group 2 treated with cyclophosphamide and thymostimulin showed a progressive recovery until base level values were surpassed in the fifth cycle (120%). Lymphocyte numbers also revealed a similar significant drop in both groups after chemotherapy commenced. Nevertheless, as treatment continued the placebo group consistently showed lymphocyte values below base level while the test group, treated with cyclophosphamide as well as thymostimulin, displayed an increase in lymphocyte values. This increase was apparent from the second cycle onward, and rose progressively, reaching above normal levels in the fifth and sixth cycles. The differences between the two groups is shown more clearly when comparing the average leucocyte and lymphocyte values throughout the experiments. In the group treated with TP-1, the average leucocyte levels recover in the second cycle and continue during the rest of the experiment. The lymphocyte values of the test group recover from the first cycle on. From the start of therapy, this group showed noticeably higher lymphocyte counts than those of both groups prior to therapy. The peak was reached in the fifth and sixth cycles, when the ratio between the lymphocyte values of the cyclophosphamide and thymostimulin group (group 2) and those of the cyclophosphamide and placebo group (group 1) was 150%. The information demonstrated thymostimulin's efficiency as a modulating drug able to counteract the experimental leucolymphocytic myelosuppression due to the use of cyclophosphamide in healthy dogs, confirming in large measure the results obtained previously by other researchers such as Shoham et at. (1980) in human cancer, Martelly & Velardi (1982) in Hodgkin's disease and Bernengo & Fra (1983) in melanomas. Trials of its clinical value in dogs are indicated.
BRITISH VETERINARY JOURNAL, 146, 3
254
ACKNOWLEDGEMENTS
The authors wish to thank the Fundacion Cientifica de la Asociacion Espanola contra el Cancer for its financial assistance and Laboratorios Serono, S.A. for their aid in this study. Part of the results of this study were reported in the XIII WSAVA World Congress in Barcelona, 1988.
REFERENCES BER;'I;ESGO, M. G. & FRA, P. (1983). Clinical Immunology andImmunopathology 28,311. CARDA, P., MONTOYA, A., BELLlOO, V., G UERRAS, C. & PEREZ-CUADRADO, S. (1986).
J. Abstract of the First Spanish Oncologic SOCIety Congress, 190. CRAIG, j. A, RICHARDSON, R. P. & RUDD, R. G. (1986). Veterinary Medicine 81, 226. JEGLlJM, K. A (1985). Vetennary Clinics North America. SmallAnimal Practice 15,817. MARTELLI, M. F. & VELARI>I, A (1982). Cancer 50, 490. SIIOHAM, j. , THEODOR, E., BRENNER, J. J ., GOLDMAN, B ., L USKY, A & CIIAITICIlICK, S. (1980). Immunotherapy 3, 173. THEILE !'> ,j. H. & rvlAIlEWELL, B. R . (1987). Veterinary Cancer Medicine, 2nd edn , pp. 183,219. Philadelphia: Lea and Febiger. (Acctpttdfor publlCDtion 7 July 1989)
ANNOUNCEMENT International Veterinary Acupuncture Congress
The 16th Annual International Congress on veterinary acupuncture will be held in Noordwijk in the Netherlands on September 13, 14 and 15. It is sponsored by the International Veterinary Acupuncture Society (LV.A.S.) and organized by the Dutch Veterinary Acupuncture Foundation (S.N.V.A.). The title of the congress will be ACUPUNCTURE AND NEUROBIOLOGY. Further information on the congress can be obtained from: Lies Schuilternaker, Esweg 19, 9471 BH Zuidlaren, The Netherlands. Tel: 05905·5762.
IMMUNOCHEMOTHERAPY (THYMOSTIMULIN/CYCLOPHOSPHAMIDE) IN DOGS
J. A. MONTOYA, E. M. MARTfNEZ, M. RODRfGUEZ and S. PEREZ-CUADRADO· Dpto. de Patologia Animal, Facultad de Vetennana, 28040 Madrid, Spain; "Dpto. de Inmunopatologia, Instituto Oncoltfgico de Madrid, 28040 Madrid, Spain
SUMMARY This article demonstates the positive effect of thymostimulin (TP-l) on leucolymphopoiesis in dogs, based on its apparent ability to counteract the immunodepression induced by cyclophosphamide chemotherapy. Thymestimulin administered to healthy cyclophosphamide-treated dogs prevented the initial drop in the values of leucocytes and lymphocytes due to the chemotherapy and restored these values to the higher levels existing before the treatment. In a control group given a placebo instead of TP- 1, the immune depression provoked by cyclophosphamide was maintained during all the therapeutic cycles
INTRODUCTION Recent advances in biotherapy provide a new perspective on controlling malignant disease, either directly or indirectly, through immunological methods. The detection of tumour associated antigens (TAA) which differ, at least quantitively, from antigens present in normal tissues, provides a rational basis on which to establish classical selective immunotherapy and, on occasions, as in the case of tumour specific antigens (TSA), specific immunotherapy (Craig, Richardson & Rudd, 1986). During the evolution of a neoplastic disease, the body's natural defences, represented by T- and B-Iymphocytes, NK cells and macrophages, are normally lowered, while the activity of the suppressor cells and the blocking antibodies increase, facilitating the tumour's establishment and growth. Along with this imbalance in the tumour-host relationship, there is a secondary immunodeficiency due to conventional cancer treatment which may include surgery, radiotherapy and chemotherapy. The fourth mode of tumour therapy, immunomodulation, seeks to correct this immunological deterioration in the host's favour, providing it with an efficient tumour immunosurveillance capacity (Theilen & Madewell, 1987). Biotherapy based on the use of biological response modulators (BRM) seeks, by various means, to stimulate or restore the host's lowered immune response and increase the efficiency of the antitumour response's effector mechanism themselves (Jeglum, 1985).
250
BRITISH VETERINARY JOURNAL, 146, 3
Biotherapy can also be useful in treating bacterial or viral illnesses which lower the host's immune response as they evolve and which represent an important branch within veterinary medicine. Cyclophosphamide (Cy) is an alkylating, cytotoxic drug belonging to the nitrogen mustard group. Its effect is to break up DNA molecules or induce inappropriate crossingover, thereby interfering with replication and transcription. This anticancer agent is frequently used in cases of lymphoproliferative diseases and solid tumours, and brings about a serious myelodepression which is reflected in leucopenia, lymphopenia, thrombocytopenia and anaemia (Craig tJ al., 1986; Theilen & Madewell, 1987). Thymostimulin, a BRM pertaining to the thymic hormones and extracts group, obtained from calves' thymus glands, restores the body's immune response, as shown by the normalization of T-Iymphocyte activity, and for inducing the differentiation and maturation of the precursors of the immunocompetent cells. In certain cases, thymestimulin's effect on lymphopoiesis and T-cell activity has been shown to be sufficient to overcome the immunodepression induced by chemotherapy (Martelli & Velardi, 1982; Bernengo & Fra, 1983), thereby justifying its use in anticancer immunochemotherapy protocols. In this article, thymostimulin's immunorestoration capacity has been assessed, contrasting it with cyclophosphamide's immunodepressant effect in healthy dogs . Our aim was to reach clear conclusions which would allow us to employ this kind of treatment in animals with tumours, and to extrapolate the information thus obtained for use in human medicine.
MATERIALS AND METHODS Seven crossbred dogs of both sexes (five males and two females) were used. They ranged between 4 and 5 years of age and 25 and 30 kg in weight. The experimental method employed involved ' in-vivo' stimulation and ' in-vitro' evaluation of the results. The animals were divided in two experimental groups: group 1, the control or placebo group, consisted of three dogs (two males and one female), and the drug-testing group, group 2, consisting of four dogs (three males and one female). The chemoimmunomodulation protocol followed that used by Carda tJ al: (1986), and involved six consecutive 21-daylong therapeutic cycles. On the first day (day 0) of each cycle animals in both groups received a massive intravenous dose (15 mg/kg of body weight) of cyclophosphamide (Genoxal, Lab. Funk, S.A.). On the second, ninth and sixteenth days of each cycle the four dogs in the test group 2 were each given an intramuscular injection (0' 5 mg/kg of body weight) of thymostimulin (TP-1, Lab. Serono, S.A.), while each of the control dogs (group 1), received the same volume of isotonic saline solution (placebo) instead ofTP-1 (Table I). On three occasions during the 2 weeks prior to the start of the experiment venous blood was taken from the cephalic vein to permit a systematic study of the blood cells; sam ples for the same purpose were taken on days 0 (21), 2, 9 and 16 of each of the study's six treatment cycles. A Coulter'S plus' haematological cell counter was used to determine the number of erythrocytes, platelets and leucocytes present in whole blood collected in EDTA 2 and lymphocyte counts were made from flesh blood smears stained by the May-Grilnwald-Giemsa method. The STAT-1-30 A (hp)- 't ' statistic for two means was used to analyse the results.
IMMUNOCHEMOTHERAPY IN DOGS
251
Table I Therapeutics cycles (TP-l/Cy) Groups
Days 2
0
16
9
21 (0)
t
(control) 2 (test)
Cy
Placebo
Placebo
Placebo
Cy
Cy
TP·t
TP·t
TP-t
Cy
Cy, cyclophosphamide administered; TP-l, thymostimulinadministered.
RESULTS The total number of leucocytes and lymphocytes in each of the groups are summarized in Figs 1, 2 and 3. The results were recorded as the average number of leucocytes and lymphocytes in each treatment cycle in relation to the base level, which in tum was the average of the values calculated in all the dogs before the start of therapy (11'293 leucocytes/mrrr' (100%) and 1'832Iymphocytes/mm3 (100%). This 100% is represented in the figures as the baseline. The analysis of the results revealed important significant differences between test group 2 and placebo group 1. 160 140 ,!!
!..120
~
j ~ 100" ~
o &
~ Baseline
=c..._
80 60
To I
o Conlrol group1leucocyles • Test group 21eucocyles
I
I
2 3 4 Therapeutic cycles
I
I
5
6
Fig. 1. Relative mean valuesof the total number of leucocytes throughout the treatment. The relative mean values of the total number of leucocytes throughout the treatment (Fig. 1), showed an initial drop in both groups during the first cycle (90% in group 2 and 91% in group 1); the leucocyte model was almost identical in both groups as regards the magnitude of each fall after the initial dose of cyclophosphamide (secondary leucopenia subsequent to chemotherapy) during the first two treatment cycles. This initial leucopenia increased and persisted in placebo group 1 during the third and fourth cycles (values of 82% and 86%, respectively), while in the test group 2, treated with thyrnostimulin, the number of leucocytes reached normal levels in the third (98%) and fourth
252
BRITISH VETERINARY JOURNAL, 146, 3
(99%) cycles. During the fifth treatment cycle, both groups showed a transitory recovery in the number ofleucocytes, although the values were higher in test group 2 (120%) than in placebo group 1 (107%). Another drop in the leucocyte count occurred in the sixth and last cycle: the numbers in placebo group 1 fell below the base level (92%), while those of test group 2, treated with TP-l, were maintained at base level (100%). The lymphocyte count (Fig. 2) also showed an initial fall in both groups during the first cycle (89% in the placebo group 1 and 90% in the test group 2). The decrease became more apparent in the second cycle, both in the placebo and in the test group (77% and 82%, respectively). The values remained practically unchanged in placebo group 1 until the end of the study: 78% in the third cycle, 79% in the fourth, 82% in the fifth and 80% in the sixth and last cycle. In contrast, in the group treated with thymostimulin, there was a progressive rise in the average number of lymphocytes from the third cycle (96%) onwards, surpassing base level values in the last two cycles (111% and 112%, respectively). 160 140 ~
..
-120 III
::>
~ 100t-.......::----------=---~L----Basehne
~
:2 eo ~
o Control\lroup1 lymphocytes • Test \Iroup2 lymphocytes
60
2
3
4
5
6
Therapeutic cycles
Fig. 2. Relative mean values of the total number of lymphocytes throughout the treatment.
160 r~
140
~ 120 ~
l/l
~
~
~~-
/~
/-~
o-....._,"--O-_---~
100 ~ /~ - ---------- ------- ~ --Baseline
eo
0::
o Lymphocytes test group 2/lymphocytes conlrol\lroup1 • Leucocytes tesl\lroup 2/ leucocytes controlgroup1
60
o
234
5
6
Therapeutic cycles
Fig. 3. Comparative study of the average leucocyte and lymphocyte values throughout the treatment.
IMMUNOCHEMOTHERAPY IN DOGS
253
The percentage ratio of leucocytes and lymphocytes in the two groups showed considerable differences between the groups throughout the study (Fig. 3). The ratio between the average number ofleucocytes in group 2 and the average number in placebo group 1 was noticeably higher than the base levels from the second cycle onward (103%); it reached peak value in the third cycle (120%), falling slightly afterwards and maintaining the difference in the fourth, fifth and sixth cycles (115%, 112% and 109%, respectively). The ratio of the average number of lymphocytes in test group 2 compared with the average number in placebo group 1 was even higher. A value of 124% in the third cycle was followed by greater values in each cycle, reaching 136% in the fifth and 141% in the sixth and last cycle. The difference between the average number oflymphocytes in both groups was statistically significant in the sixth cycle (ir20117 lymphocytes/rnm' (SE: ± 175); i t - 1°506lyrnphocytes/mrrr' (SE: ± 157); t-206; dj-26; P<0002).
DISCUSSION
The results revealed that both groups had a similar leucocyte model in relation to the secondary leucopenia due to treatment with cyclophosphamide. Nevertheless, in the untreated placebo group 1, the drop in the number of leucocytes was progressive until the fourth chemotherapeutic cycle, after which there was a slight natural leucocyte 'rebound', with values which slightly surpassed the base level in the fifth cycle (107%). The number fell again to below normal levels (92%) in the sixth cycle. On the other hand, after the initial leucocyte level drop experienced by both groups during the first and second cycles, the group 2 treated with cyclophosphamide and thymostimulin showed a progressive recovery until base level values were surpassed in the fifth cycle (120%). Lymphocyte numbers also revealed a similar significant drop in both groups after chemotherapy commenced. Nevertheless, as treatment continued the placebo group consistently showed lymphocyte values below base level while the test group, treated with cyclophosphamide as well as thymostimulin, displayed an increase in lymphocyte values. This increase was apparent from the second cycle onward, and rose progressively, reaching above normal levels in the fifth and sixth cycles. The differences between the two groups is shown more clearly when comparing the average leucocyte and lymphocyte values throughout the experiments. In the group treated with TP-1, the average leucocyte levels recover in the second cycle and continue during the rest of the experiment. The lymphocyte values of the test group recover from the first cycle on. From the start of therapy, this group showed noticeably higher lymphocyte counts than those of both groups prior to therapy. The peak was reached in the fifth and sixth cycles, when the ratio between the lymphocyte values of the cyclophosphamide and thymostimulin group (group 2) and those of the cyclophosphamide and placebo group (group 1) was 150%. The information demonstrated thymostimulin's efficiency as a modulating drug able to counteract the experimental leucolymphocytic myelosuppression due to the use of cyclophosphamide in healthy dogs, confirming in large measure the results obtained previously by other researchers such as Shoham et at. (1980) in human cancer, Martelly & Velardi (1982) in Hodgkin's disease and Bernengo & Fra (1983) in melanomas. Trials of its clinical value in dogs are indicated.
BRITISH VETERINARY JOURNAL, 146, 3
254
ACKNOWLEDGEMENTS
The authors wish to thank the Fundacion Cientifica de la Asociacion Espanola contra el Cancer for its financial assistance and Laboratorios Serono, S.A. for their aid in this study. Part of the results of this study were reported in the XIII WSAVA World Congress in Barcelona, 1988.
REFERENCES BER;'I;ESGO, M. G. & FRA, P. (1983). Clinical Immunology andImmunopathology 28,311. CARDA, P., MONTOYA, A., BELLlOO, V., G UERRAS, C. & PEREZ-CUADRADO, S. (1986).
J. Abstract of the First Spanish Oncologic SOCIety Congress, 190. CRAIG, j. A, RICHARDSON, R. P. & RUDD, R. G. (1986). Veterinary Medicine 81, 226. JEGLlJM, K. A (1985). Vetennary Clinics North America. SmallAnimal Practice 15,817. MARTELLI, M. F. & VELARI>I, A (1982). Cancer 50, 490. SIIOHAM, j. , THEODOR, E., BRENNER, J. J ., GOLDMAN, B ., L USKY, A & CIIAITICIlICK, S. (1980). Immunotherapy 3, 173. THEILE !'> ,j. H. & rvlAIlEWELL, B. R . (1987). Veterinary Cancer Medicine, 2nd edn , pp. 183,219. Philadelphia: Lea and Febiger. (Acctpttdfor publlCDtion 7 July 1989)
ANNOUNCEMENT International Veterinary Acupuncture Congress
The 16th Annual International Congress on veterinary acupuncture will be held in Noordwijk in the Netherlands on September 13, 14 and 15. It is sponsored by the International Veterinary Acupuncture Society (LV.A.S.) and organized by the Dutch Veterinary Acupuncture Foundation (S.N.V.A.). The title of the congress will be ACUPUNCTURE AND NEUROBIOLOGY. Further information on the congress can be obtained from: Lies Schuilternaker, Esweg 19, 9471 BH Zuidlaren, The Netherlands. Tel: 05905·5762.