Plasmodium cynomolgi: the hsp 70 gene

Cellular and antibody responses to the Plasmodium falciparum heat shock protein Pf72/HSP70 during and after acute malaria in individuals from an endemic area of Brazil

Proliferative and antibody responses to three synthetic peptides corresponding to Pf72/ HSP70 were followed-up in acute malaria patients from an endemic area of Brazil. In vitro lymphocyte responsiveness to all peptides was relatively low and short-lived and there was a considerable variation in the frequency and magnitude of the individual lymphoproliferative response to the peptides at different periods after the onset of infection. Although 96% of the patients had IgG antibodies to crude Plasmodium falciparum asexual blood stage antigens, specific IgG antibody responses to the peptides varied from 12.5 to 40% according to the tested peptides. No significant difference was observed in the proliferative or antibody responses to the peptides between individuals that remained parasitemic after treatment and those that recovered from malaria infection. The different frequencies of proliferative responses in peripheral blood T cells on different occasions after the onset of their infection show that, in order to be informative, evaluation of the in vitro cellular immune response to peptides requires longitudinal studies in which each individual is tested repeatedly.

Bradyzoite development in Toxoplasma gondii and the hsp70 stress response

Toxoplasma gondii is a well-described ubiquitous Apicomplexan protozoan parasite that is an important opportunistic pathogen. The factors affecting the transition of tachyzoites to the latent bradyzoite stage remain to be defined. The induction of bradyzoite development in vitro has been linked to temperature, pH, mitochondrial inhibitors, sodium arsenite, and many of the other stressors associated with heat shock protein (hsp) induction. There is evidence for other organisms that hsps are developmentally regulated. Therefore, we examined whether hsp induction is an early event in bradyzoite differentiation. Extracellular and intracellular T. gondii cells, after exposure to pH 8.1 or 7.1, were analyzed for the expression of inducible hsp70 by using monoclonal antibody C92F3A-5 (specific to hsp70). Western blotting demonstrated that a 72-kDa protein reactive with C92F3A-5 (hsp70), which we believe is part of the hsp70 family, is induced during bradyzoite development. By immunofluorescence and immunoelectron microscopy, we were able to demonstrate that hsp70 staining colocalized to T. gondii expressing bradyzoite-specific antigens and the presence of hsp70 in bradyzoites isolated from mouse brain. Quercetin, a bioflavonoid which inhibits the synthesis of hsp90, hsp70, and hsp27, suppresses the induction of bradyzoite development in vitro. Reverse transcription-PCR with conserved hsp70 primers demonstrated an increase in hsp70 in T. gondii on exposure to conditions which induce bradyzoite formation. A T. gondii hsp70 was subsequently cloned and sequenced by using this amplified fragment. We believe our evidence suggests that hsps are important in the process of bradyzoite differentiation.

Demonstration of heat-shock protein 70 in the sporozoite stage of malaria parasites

Three monoclonal antibodies generated by immunization of mice with Plasmodium berghei-infected red blood cells were found to react with the 75-kDa heat-shock protein (HSP70) present in liver stages and erythrocytic forms of the parasites. These antibodies were shown to react with a recombinant protein encoding the carboxyl terminal half of PfHSP70 (aa 365-681). Differently from earlier results, we clearly demonstrated that HSP70 was also expressed in the sporozoite stage, using these monoclonal antibodies in an immunofluorescence and Western immunoblot assay. These monoclonal antibodies react not only with sporozoites of P. berghei, the parasites originally used for the immunization, but also with sporozoites of several other rodent and human plasmodial species. Passive transfer of these monoclonal antibodies into naive mice, simultaneously injected with sporozoites, failed to neutralize the infectivity of P. berghei sporozoites and to inhibit the development of liver stages of P. yoelii.