Multivalent DNA vaccine induces protective immune responses and enhanced resistance against Cryptosporidium parvum infection.

The aim of this work was to evaluate efficiency as well as the type of immune response, Th1 or Th2, induced by multivalent DNA vaccinations in C57BL/6 interleukin-12p40 (IL-12p40) knockout (KO) mice. A recombinant pVAX-15-23 plasmid DNA was constructed by inserting surface glycoprotein (cp15- and p23)-encoding DNA into the pVAX1 expression vector. Various parameters including antibody and cytokine responses, proliferation assay and oocyst shedding were used to evaluate the type of immune response and the level of protection against challenge infection. Obtained results indicated that plasmid pVAX-15-23 induced strong protective immune response against C. parvum characterized by dominance of IgG2a, high level of INF-γ and lower level of the oocysts shedding after challenge infection. Moreover, co-immunization with the multivalent DNA and pMEM12R plasmid encoding IL-12 can further enhance these responses compared with the multivalent DNA alone. The obtained results suggest that multivalent pVAX-15-23 DNA vaccine may be a candidate as a generic approach to C. parvum immunization applicable to clinical practice.