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Double HIV infection may provide key to vaccine

Robin Wulffson MD's picture
HIV, AIDS, vaccine, prevention, treatment, superinfection

Ever since HIV came to public attention several decades ago, scientists have been searching for an effective vaccine. New research might pave the way for an effective vaccine. Investigators with the Fred Hutchinson Cancer Research Center have found that women who have been infected with two different strains of HIV have more effective antibody responses than those who have only been infected once. This finding brings HV/AIDS research one step closer to developing an effective vaccine.

A double infection—an infection with more than one strain of a virus—is known as a superinfection. The researchers studied a group of women living with HIV in Mombasa, Kenya, for a period of five years. They followed the immune activity of 12 women who were superinfected and compared their results to a group of 36 singly-infected women. They also controlled for risk factors, which could have affected the results. They found that the women who had been infected with two different strains of the virus exhibited more effective antibody responses than women who had been infected once. Furthermore, the response of the superinfected women was found to stop replication of the virus.

“These results suggest that potentially having two different antigens is a better way to stimulate a good immune response than just one,” noted lead author Dr. Julie Overbaugh, a member of the Hutchinson Cancer Research Center’s Human Biology Division. She added, “So now the question is: What should be in a good vaccine? These women may be giving us clues…Now we really want to know why they had a better immune response. When you’re studying naturally infected populations, you can’t really demonstrate cause and effect. What we try to do is try to understand how this kind of response might have been generated. So we need to isolate [and study] the antibodies that these individuals generated.”

The researchers found that, on the average, the superinfected women had 1.68 times more neutralizing antibodies than the singly infected women; furthermore, their ability to neutralize the virus from spreading was 1.46 times higher.

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The researchers have some theories regarding how a superinfection stimulated more of an immune response. One is that the first virus attack stimulated a fair immune response; however, the second virus augmented that response. The other theory is that each virus provoked a different response to each virus and the combined effect added up to a greater response.

Most researchers feel that the development of a vaccine is the best method to control HIV/AIDS. The vaccine would potentially be developed in a similar manner to that of the influenza vaccine. This vaccine incorporates a number of different viral strains; when it is injected into the body, it stimulates a prompt and effective immune response. Thus, the HIV vaccine would be composed of multiple HIV strains.

According to the U.S. Department of Health and Human Services (HHS), more than 1.1 million Americans are infected with HIV, and a new infection occurs every 9.5 minutes. According to the Centers for Disease Control and Prevention, at the end of 2007 the estimated numbers of adults and adolescents living with AIDS were highest in the South and Northeast, and lowest in the Midwest. The states with the most AIDS diagnoses were found in the south; however, the cities with the most AIDS cases were spread across the nation. Blacks/African Americans accounted for the largest proportion of AIDS cases in all areas except the West where whites accounted for the highest number of cases.

Reference: Fred Hutchinson Cancer Research Center

See Also: UCLA researchers suggest new approach to control HIV epidemics