Epitope Plasmid DNA Vaccine Generates Cellular Immunity In Mice.(Brief Article)

2001 AUG 22 - (NewsRx.com & NewsRx.net) --

by N.R. Saltmarsh, staff medical writer - The ability of epitope plasmid DNAs to trigger only a specific cellular immune response instead of an antibody response may ultimately lead to their use in an effective tuberculosis vaccine, researchers in the Netherlands suggest.

"In this study, we constructed DNA vaccines encoding cytotoxic T lymphocytes (CTL) and T helper cell (Th) epitopes of the 38-kDa lipoglycoprotein of Mycobacterium tuberculosis and analyzed and compared their immunogenicities with that of pXJ38, a DNA vaccine encoding the entire 38-kDa protein," reported D.P. Fonseca and colleagues, pointing out that cell-mediated immunity is crucial for protection against TB.

The researchers constructed plasmid DNA vaccines encoding a CTL epitope, P3 (pP3), a Th epitope (vTh), or both the Th and the P3 epitopes (pThP3) and tested them in murine models.

"Our results confirmed that DNA immunization with pXJ38 induces strong CD8(+) CTL and Th1 responses (high gamma interferon [IFN-gamma], low interleukin-4 [IL-4])," they reported.

Coadministration of plasmid DNAs encoding a Th epitope with those encoding a CTL epitope (vTh+pP3) elicited antigen-specific CD8(+) CTL and Th1 responses, while in vitro stimulation with the recombinant 38-kDa protein led to secretion of high levels of IFN-gamma by spleen cells from all plasmid DNA-vaccinated mice, noted Fonseca and coworkers. The presence of small or undetectable amounts of IL-4 indicated the induction of a Th1-like response, they added.

On the other hand, antigen-specific immunoglobulin G2a was only detected in sera from mice immunized with the plasmid pXJ38 and not in mice immunized with the epitope-based DNA vaccines, ...