Optimized immune response elicited by DNA vaccine expressing Pneumococcal surface protein A (PspA) is characterized by balanced IgG1:IgG2a ratio, IFN- and TNF- production

Centro de Biotecnologia, Instituto Butantan, São Paulo, SP, Brazil

^* To whom correspondence should be addressed. Email: enmiyaji{at}butantan.gov.br.

	Abstract

We have previously shown that DNA immunization with PspA (Pneumococcal surface protein A) is able to elicit protection comparable to that elicited by immunization with PspA protein (with alum as adjuvant) even though the antibody levels elicited by DNA immunization are lower than those elicited by immunization with the protein. This work aims at characterizing the ability of these sera to bind to the pneumococcal surface and mediate complement deposition using BALB/c wild-type and IL-4-knockout mice. We observed that higher anti-PspA levels correlated with intense antibody binding to the pneumococcal surface, while elevated complement deposition was observed with sera that presented balanced IgG1/IgG2a ratios, such as from DNA immunized mice. Furthermore, we demonstrate that IFN- and TNF- were strongly induced after intraperitoneal pneumococcal challenge only in mice immunized with DNA vaccine. We therefore postulate that although both DNA and recombinant protein immunization are able protect mice against intraperitoneal pneumococcal challenge, an optimized response would be achieved by using DNA vaccine and other strategies capable of inducing balanced Th1/Th2 responses.