May 19, 2010
In a new preliminary study, researchers hypothesized that the emergence of HIV beginning in the 1950s could have an association with the gradual eradication of smallpox.
If the smallpox vaccine conferred partial protection against HIV infection, it could have kept HIV under control during the earliest outbreaks. As smallpox eradication was achieved, withdrawal of the vaccine might have allowed HIV to flourish, suggested Raymond S. Weinstein of George Mason University and colleagues.
To test the proposition, the team compared the HIV-1 susceptibility of peripheral blood mononuclear cells between subjects who were immunized with the vaccinia virus and those who were vaccine-naïve.
Among the laboratory blood samples of those who had been vaccinated against smallpox in the preceding three to six months, there was up to a five-fold reduction in CCR5-tropic, but not CXCR4-tropic, HIV-1 replication. "The addition of autologous serum to the cell cultures resulted in enhanced R5 HIV-1 replication in the cells from unvaccinated, but not vaccinated subjects," researchers found. "There were no significant differences in the concentrations of MIP-1alpha, MIP-1beta, and RANTES" between the groups.
"Since primary HIV-1 infections are caused almost exclusively by the CCR5-tropic HIV-1 strains, our results suggest that prior immunization with vaccinia virus might provide an individual with some degree of protection to subsequent HIV infection and/or progression," wrote Weinstein and colleagues. "The duration of such protection remains to be determined."
However, it is "far too soon to recommend the general use of vaccinia immunizations for fighting HIV," Weinstein noted.
The full study, "Significantly Reduced CCR5-Tropic HIV-1 Replication in vitro in Cells from Subjects Previously Immunized with Vaccinia Virus," was published in BMC Immunology (2010;doi:10.1186/1471-2172-11-23).