April 11, 2012
HIV Superinfection Boosts Immune Response
(Ivanhoe Newswire) -- A new study suggests that women who have been infected by two variations of HIV may have a better chance of suppressing the virus then those only infected with one.
More than 1.1 million Americans are estimated to be living with HIV today, and every nine-and-a-half minutes someone in the U.S. becomes infected, according to the U.S. Department of Health and Human Services. An HIV vaccine is considered the best approach to long-term protection from HIV infection, but attempts to develop such a vaccine so far have met with limited success.
"We found that women who had been infected twice not only had more potent antibody responses, but some of these women had 'elite' antibody activity, meaning that they had a broad and potent ability to neutralize a wide variety of strains of HIV over a sustained period time," Julie Overbaugh, Ph.D., senior author, was quoted as saying. Approximately 1 percent of people with HIV are so-called "elite neutralizers" who are able to potently neutralize multiple subtypes of the virus.
"Individuals who become superinfected with a second virus from a different partner represent a unique opportunity for studying the antibody response and may provide insights into the process of developing broad neutralizing antibodies that could inform HIV-vaccine design, Overbaugh said.
Housing a combination of viral strains may be one way to promote a robust antibody response. The findings also suggest that being infected with two different HIV strains not only leads to a strong response, but also a more rapid response that is capable of recognizing many other HIV strains.
For the study researchers tracked the immune activity of 12 superinfected women from Mombasa, Kenya, over a five-year period and compared each to a control group of three infected women with one strain of HIV. Overbaugh and lead author Valerie Cortez, a doctoral student in her lab, analyzed the ability of antibodies present in superinfected and singly infected women to neutralize a spectrum of circulating HIV-1 variants. In doing so they were able to determine whether the presence of two viruses compared to one made a difference in immune response. The researchers controlled for variables such as antibody response prior to superinfection and biomarkers of immunity such as CD4+ T cell count and viral load.
Researchers found that superinfected women had, on average, 1.68 times more neutralizing antibodies than non-superinfected women, and they scored much higher in their ability to neutralize the virus. Superinfected women had 1.46 times greater potency than the singly infected women.
"The holy grail of an HIV vaccine is to elicit antibodies to the virus because antibodies have been shown to block virus infection. But there has been little progress in determining how to elicit such antibodies with a vaccine. The study of individuals HIV infected who have developed strong antibody responses to the virus may shed light on the best approach to design a vaccine that will induce an effective immune response," Overbaugh was quoted as saying.
SOURCE: PLoS Pathogens, March 29, 2012