DNA vaccine with pneumococcal surface protein A elicits immune responses.

2003 AUG 6 - (NewsRx.com & NewsRx.net) -- A DNA vaccine containing pneumococcal surface protein A elicited protective humoral and cellular immune responses.

"Streptococcus pneumoniae is a major public health problem and new strategies for the development of cost-effective alternative vaccines are important. The use of protein antigens such as PspA (pneumococcal surface protein A) is a promising approach to increase coverage at reduced costs. We have previously described the induction of a strong antibody response by a DNA vaccine expressing a C-terminal fragment of PspA," scientists in Brazil report.

"Fusion of this fragment with the cytoplasmic variant of SV40 large T-antigen (CT-Ag) caused reduction in specific interferon-gamma produced by stimulated spleen cells," said Eliane N. Miyaji and colleagues at the Instituto Butantan in Sao Paulo. "In this work we show that the DNA vaccine expressing the C-terminal region of PspA elicits significant protection in mice against intraperitoneal challenge with a virulent strain of S. pneumoniae.

"Furthermore, fusion with CT-Ag completely abrogated the protection elicited by DNA immunization with this fragment. In this case, protection did not correlate with total anti-PspA antibody production nor with total IgG2a levels."

The investigators found, "The anti-PspA sera obtained from both constructs showed equivalent opsonic activity of pneumococci, indicating that the antibodies produced were functional. We could, though, observe a correlation ...