LACK DNA Vaccine Induces Immunity But Not Protection Against L. donovani.(Leishmania homolog of receptors for activated C kinase)

2001 SEP 19 - (NewsRx.com & NewsRx.net) --

by N.R. Saltmarsh, staff medical writer - A new vaccine is highly immunogenic against Leishmania donovani but cannot induce protection against visceral leishmaniasis (VL), report researchers in the United States.

"The acquisition of immunity following subclinical or resolved infection with the intracellular parasite L. donovani suggests that vaccination could prevent VL," said P.C. Melby and colleagues at the University of Texas Health Sciences Center, San Antonio.

The LACK (Leishmania homolog of receptors for activated C kinase) antigen has been immunopathogenic in murine models of L. major by redirecting the early T-cell response away from a pathogenic interleukin-4 (IL-4) response and toward a protective Th1 response, explained Melby and coworkers and thus was considered a vaccine candidate for leishmaniasis in humans.

The researchers studied the efficacy of Leishmania p36(LACK) antigen against VL because of the serious nature of this form of leishmaniasis and because it was unclear whether the LACK vaccine would be effective in a model where there was not a dominant pathogenic IL-4 response ("Leishmania donovani p36(LACK) DNA vaccine is highly immunogenic but not protective against experimental visceral leishmaniasis," Infection and Immunity, August 2001;69(8):4719-4725).

"We demonstrate here that although the LACK DNA vaccine induced a robust parasite-specific Th1 immune response (IFN-gamma but not IL-4 ...