In an attempt to elucidate the events leading to the development of post-treatment reactive encephalopathy in human African trypanosomiasis (HAT), a group of vervet monkeys (Cercopithecus aethiops) were experimentally infected with Trypanosoma rhodesiense. When terminally sick on day 42, they were treated with either diminazene aceturate (Berenil®), suramin or melarsoprol. Trypanosomes appeared in the cerebrospinal fluid (CSF) by day 14 of infection and increased in numbers with progress of the disease. However, only marginal increases in CSF total proteins and white cells occurred during the same period. Treatment with Berenil resulted in persistence and increase in numbers of CSF trypanosomes, a dramatic increase in proteins and white cells, culminating in clinical encephalitis. Suramin cleared CSF trypanosomes within 4 weeks, with marginal increase in proteins and white cells up to 8 weeks after treatment, followed thereafter by a gradual and prolonged fall to pre-infection levels. Melarsoprol eliminated trypanosomes from the CSF in less than a week but the white cell and protein levels increased for another 4 weeks before finally falling. The post-treatment increase in white cell numbers and total proteins was therefore dependent on the trypanocidal drug, and was highest and most prolonged when Berenil was used and lowest with suramin. The present studies demonstrate that trypanocidal treatment of infected animals is followed by a post-treatment reaction in the central nervous system, the severity of which is related to the drug used and the presence of trypanosomes in the CSF. The vervet monkey therefore appears to be a good model for studying the reaction in HAT.

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The antigenic relationship(s) amongst kinetoplastid flagellates viz. Leishmania donovani promastigotes, Bodo indica n. sp. and Herpetomonas indica n. sp. have been evaluated using immunoelectrophoresis, indirect fluorescent antibody test, enzyme-linked immunosorbent assay, sodium dodecyl sulphate-polyacrylamide gel electrophoresis and electroimmunotransfer blot assay. Antisera raised against the three organisms were tested with homologous and heterologous antigens. In all the assays, common antigens against three flagellates have been demonstrated against the homologous and heterologous antibodies. However, a more closer antigenic relationship between H. indica n. sp. and L. donovani antigens and antibodies was observed in all tests than B. indica n. sp. antigen and antibodies to H. indica n. sp. or L. donovani antigen and antibodies. These findings will be very useful in studies on phylogenetic relationship between Bodonina and Trypanosomatina of order Kinetoplastida.

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The antigenic component TLA-Ig8 purified from Toxoplasma gondii-lysate antigen (TLA-144) using anti-TLA-144 and anti-TLA-Ig8 monoclonal antibodies exhibited significant anti-tumor activity in methylcholanthrene tumor cell-bearing BALB/c mice. Binding activity of labelled TLA-Ig8 antigenic component to adherent cells was significantly higher relative to non-adherent cells, and reached a plateau approximately 30 minutes post-incubation. Binding reaching a saturation point early on facilitates the attachment of the antigen to the surface membrane receptor of adherent cells enhancing antigen processing through phagocytosis and thus inducing cytotoxic activity. Analysis of specific macrophage cell surface antigen revealed a molecule of molecular weight 80 kilodaltons. Our results suggest TLA-Ig8 antigenic component to be a tachyzoite surface antigen important in the induction of cytotoxic cell activity.

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The hemolytic activity of live Trichomonas vaginalis, Trichomonas gallinae, Tritrichomonas foetus, Tritrichomonas suis was described. The four isolates were tested against human erythrocytes. No hemolytic activity was detected by the isolates of genus Tritrichomonas. Whereas the strains of genus Trichomonas lysed all human blood groups. No hemolysin released by the parasites could be detected. Our preliminary results suggest that the hemolysis depends on the susceptibility of red cell membranes to destabilization and the intervention of cell surface receptors as a mechanism of the hemolytic activity. This mechanism could be subject to strain-genera-species specific variation of trichomonads. Although the hemolytic activity of T. vaginalis and T. gallinae is not due to a hemolysin or to a product of its metabolism. Pre-treatment of trichomonads with concanavalin A reduced levels of hemolysis by 40%.

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The role of T cells for the resolution of acute primary infection with Babesia microti was investigated in the present study. BALB/c mice exhibited a peak parasitemia of approximately 40％ of parasitemia and subsequently recovered naturally from their primary infection. Nude mice, however, could not resolve primary infection and developed persistent high parasitemia. Mice depleted of CD4^＋ T cells with monoclonal antibody (mAb) had high parasitemia and failed to control the infection. However, depletion of CD4^＋ T cells one week after infection did not affect the course of infection. Depletion of CD8⁺ T cells showed no apparent effect on the course of infection. High concentration of IFN-γ was demonstrated in the culture supernatant of spleen cells from untreated and anti-CD8 mAb treated mice, but not from anti-CD4 mAb treated mice. Mice treated with anti-IFN-γ mAb showed higher peak parasitemia and remained above 10％ of parasitemia until days 26 after infection. These results suggest that CD4^＋ T cells play an essential role in the resolution of B. microti acute primary infection and that IFN-γ produced by CD4^＋ T cells is partially responsible for control of early stage of acute infection with B. microti

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