Evaluation of the protective effect of a prime-boost strategy with plasmid DNA followed by recombinant adenovirus expressing BmAMA1 as vaccines against Babesia microti infection in hamster

Abstract

In the present study, we have investigated the protective effect of a heterologous prime-boost strategy with priming plasmid DNA followed by recombinant adenovirus, both expressing BmAMA1, against Babesia microti infection. Four groups consisting of 3 hamsters per group were immunized with pBmAMA1/Ad5BmAMA1, pNull/Ad5BmAMA1, pBmAMA1/Ad5Null and pNull/Ad5Null, followed by challenge infection with B . microti . Our results showed that hamsters immunized with plasmid and adenovirus expressing BmAMA1 developed a robust IgG and IgG2a antibody response against BmAMA1, suggesting the DNA vaccine or viral vector vaccine tend to induce a Th1-biased response. Compared to the control hamsters, the hamsters vaccinated either with the prime-boost strategy or one of the two “vaccines” exhibited no significant protection against B . microti challenge. Although a slight difference in terms of parasitemia and hematocrit values at days 14–16 post challenge infection was observed, no other statistical difference was detected. Our results indicate that the prime-boost vaccination strategy of injection of plasmid and adenovirus expressing BmAMA1 is not efficient in protecting against B . microti infection.

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