Immunogenicity of toxoplasma gondii heat shock protein 70

Miller, Kate;Smith, Nicholas;Luton, Kim;Johnson, Alan

Abstract

Heat shock proteins (HSPs) are a group of proteins involved in maintaining cell homeostasis. Their synthesis is increased dramatically in response to stimuli such as temperature shifts, changes in concentrations of glucose and calcium and also in response to immune factors. HSP70 has been found to be strongly expressed in virulent strains of Toxoplasma gondii taken from immunocompetent mice but poorly expressed in avirulent strains taken from immunocompromised mice or virulent and avirulent strains cultivated in vitro. Hence, T. gondii HSP70 may help protect parasites against the host's immune response, allowing the virulent strains to persist as tachyzoites without the enforced encystation found in avirulent strains. This makes T. gondii HSP70 an attractive subunit candidate. To investigate the immunogenicity of this protein it was affinity purified from tachyzoites of the virulent RH strain and injected into BALB/c mice along with Freund's Complete Adjuvant (FCA). A booster shot with Freund's Incomplete Adjuvant (FIA) was given 4 weeks after the initial injection and blood was collected at 8 weeks. The RH strain HSP70 DNA was cloned as a GST fusion protein, expressed and also injected into BALB/c mice to see if the immune response generated by the recombinant protein matched that of the native protein. Antibody response was measured by ELISAs to detect IgGl, IgG2a, IgG2b and IgG3. An elevation of IgGl antibodies, but not other IgG subsets, was observed in the mice immunised with native or recombinant HSP70. This suggests that the immune response seen with the recombinant protein is similar to that seen with the native protein. However, the response to either protein was weak, suggesting that the T. gondii HSP70 may not be a particularly good immunogen.CopyrightÂ© 1999, The Research Center for Protozoan Molecular Immunology.

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Journal of Protozoology Research

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0917-4427

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National Research Center for Protozoan Diseases

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DOI

10.32268/jprotozoolres.9.4_113