Modified Vaccinia Virus Ankara Repeat Dosing May Limit Effectiveness.(Brief Article)

2001 OCT 10 - (NewsRx.com & NewsRx.net) --

by Michael Greer, senior medical writer - Multiple administration of some HIV vaccines may reduce their efficacy, researchers in Europe and the United States warn.

"A major aim in AIDS vaccine development is the definition of strategies to stimulate strong and durable cytotoxic T lymphocyte (CTL) responses," according to Sally Sharpe and colleagues at the Centre for Applied Microbiology and Research (CAMR) and the Institute of Molecular Medicine in the U.K., the Institute for Molecular Virology in Germany, and the United States National Institute of Allergy and Infectious Diseases in Rockville, Maryland.

Sharpe and coworkers found, however, that repeat dosing with a modified vaccinia virus Ankara (MVA)-based vaccine limited the durability of induced CTL activity.

Four macaques were given intramuscular injections of MVA vectors expressing a variety of genes from the simian version of HIV (SIV). After the first such injection, all four animals displayed CD8 cell immune activity specific to the SIV Nef protein, the researchers said. However, these CTL responses stopped in two macaques after further doses.

In another group of two macaques with Mamu A(*)01 major histocompatibility complex (MHC) class I expression, Nef- but not Gag-specific activity was again induced with MVA vectors transfected with nef and gag-pol DNA under P7.5, a moderate strength vaccinia virus promoter. Further ...