The F1 and V subunit vaccine protects against plague in the absence of IL-4 driven immune responses

A subunit vaccine for plague utilising the F1 and V antigens of Yersinia pe stis has been shown to be highly protective in a mouse model. Protection ag ainst aerosol and parenteral infection has been found to correlate with the production of large amounts of IgG1. In this study the effect of a genetic mutation in the immune system on protection was studied. IL-4T mice which are unable to synthesize the Th2 cytokine IL-4, and so should have reduced IgG1 responses, were utilised to determine whether an immune system biased towards the Th1 axis could mount an effective response to the vaccine. Anti body isotype profiles generated in IL-4T mice differed from the intact pare nt C57 BL/6 strain, although total IgG levels were similar between the two strains. Immune cell and serum transfers from IL-4T and C57 BL/6 mice to na ive mu MT strain mice were performed and recipient mice challenged with vir ulent Y. pestis. mu MT were fully protected by passive transfer of antibody from either donor strain immunized with F1+V or with F1 only. However, pro tection was only partial in mu MT receiving IL-4T serum with specificity fo r the V antigen only. Actively immunized IL-4T mice mounted a vigorous resp onse to the vaccine and were resistant to challenge. These results suggest that even in an altered immune system the F1 and V subunit vaccine is capab le of eliciting a protective immune response.