A 65-kDa heat shock protein (HSP65) is present in mouse peritoneal macrophages that have been infected with a low-virulence Beverley strain of Toxoplasma gondii or immunized with Toxoplasma homogenate, as determined by electroblot assay using a monoclonal antibody specific for microbial HSP65. This HSP65 is, however, not expressed in the infection with the high-virulence RH strain of T. gondii. Furthermore, mice previously vaccinated with a sublethal dose of live Beverley strain bradyzoites of T. gondii, acquired resistance against infection with the virulent RH strain and they likewise expressed HSP65. Rats are genetically resistant against the infection even with high dose of RH strain, and HSP65 is also expressed in their peritoneal macrophages. These results suggest the important role played by HSP65 in developing effective defense reactions that include effective immune response against infection with T. gondii in vivo. We clarified that γδ T cells as well as CD⁴⁺ T cells play a crucial role in the expression of HSP65 in macrophages of animals which have acquired resistance against Toxoplasma infection. The expression mechanism(s) and the function of HSP65 are still unknown.

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A 2.5 yr. old child presented with hepatosplenomegaly and wart-like lesions on the forehead and foot. Leishmania parasites recovered from bone marrow aspirate and cutaneous lesions were dot-blotted on nitrocellulose and hybridized to whole kDNA. Hybridization to either Leishmania donovani or to Leishmania tropica kDNA was found to be species-specific, while Leishmania major probe showed extensive cross hybridization. The face lesion stock did not hybridize with either L. donovani or L. tropica probe and was identified by isoenzyme electrophoresis as L. major. The variable hybridization pattern obtained from the foot lesion stock suggest the presence of mixed infection. Cloning followed by isoenzyme electrophoresis revealed the presence of L. donovani and L. major clones. The visceral stock variable hybridization with L. donovani and L. tropica probes suggests the presence of these two species. Only L. tropica clones however, could be recovered as identified by isoenzyme electrophoresis. The results show the presence of simultaneous infection with three human Leishmania spp. in a case which was unresponsive to Pentostam therapy.

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Lactate-dehydrogenase isoenzymes in oocysts of Eimeria tenella and Eimeria stiedae were specified by disc electrophoresis and were further analyzed by isoelectric focusing in polyacrylamide gel. Two LDH isoenzymes were found in E. tenella and one in E. stiedae oocysts by disc electrophoresis. With isoelectric focusing, four isoenzymes were specified at different isoelectric points – PH 6.5 – 7.2 (E. tenella), and pH 5.7 – 6.8 (E. stiedae). The occurrence of species-specific LDH-electrophoretic isoenzymes in each species of Eimeria examined suggests the presence of two LDH genes in all members of Genus Eimeria.

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Pneumocystis carinii is a widespread opportunistic agent found in the lungs of mammals. This organism causes severe pneumonia in immunocompromised hosts. Antigenic genomic and karyotypic host-species related differences have been reported among P. carinii isolates. Nevertheless, it has not been proved if Pneumocystis from a given mammal can infect other host species. We have then attempted to infect P. carinii -free SCID mice with either mouse, rat or rabbit-derived P. carinii isolates by nasal instillation. Forty and 90 days post-inoculation, only SCID mice instillated with mouse-derived parasites developed P. carinii pneumonia (PCP). Our findings suggest that P. carinii exhibits strong host species specificity. Furthermore, cross infection experiments would be a useful tool in the identification of Pneumocystis species, and in the epidemiology of PCP.

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Mice chronically infected with toxoplasma gondii were treated with cyclophosphamide, obiopeptide-1 (Obi-1) and/or anti-CD4 monoclonal antibody to determine the effect of these immunosuppressive agents on the cysts in the brain. In the brain of non-treated, and infected cyclophosphamide-Obi-1 treated mice, with hematoxylin-eosin, and anti-Toxoplasma avidin-biotin-conjugate labelling techniques, large typically rounded tissue cysts were mostly detected, and sometimes with dividing microcysts. In contrast, brain tissue from cyclophosphamide only or anti-CD4 treated infected mice had multiple degenerate cysts of varied size in some brain regions, as well as clusters of microcysts, however, such change was more striking in the anti-CD4 treated group. Infected mice treated with a combination of cyclophosphamide and Obi-1 showed a significantly higher survival of 80％ compared to 20％ survival in mice treated with cyclophosphamide only. Percent neutrophilic leucocytes, monocytes and lymphocytes in mice treated with a combination of Obi-1 and anti-CD4, or Obi-1 and cyclophosphamide were higher compared to those groups treated with anti -CD4 antibody, or cyclophosphamide only. The increase in neutrophilic leucocyte and lymphocyte counts after a combined cyclophosphamide and Obi-1 treatment may, likewise, contribute to the induction of resistance in mice against T. gondii. Furthermore, these results seem to suggest that the reactivation or rupture of tissue cysts in mice chronically infected with T. gondii is not principally correlated with the death of cyclophosphamide treated mice.

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