We’ve been told for a very long time that even if you’re HIV-positive, you can still get infected by other strains of HIV and get what is called “super-infection” with a less manageable form of HIV. No one ever provided much hard evidence for this and studies were few and far between. But we now have a new study, the best so far, that essentially debunks the notion of super-infection altogether. It was announced at the Bangkok conference and you can read the abstract here. Bottom line:
In a study of 33 HIV+ couples who engaged in frequent, unprotected sex, researchers at the Gladstone Institute of Virology and Immunology in San Francisco found no evidence of superinfection, the sequential acquisition of multiple HIV variants.
HIV is a highly mutable virus encompassing two quite different types around the world, HIV-1 and HIV-2. Within those types there are variations known as “subclades” that are typically subdivided further into genetically differentiated strains.
The epidemic in the U.S. consists almost entirely of a single subclade, HIV-1B, while HIV epidemics in other parts of the world involve a mix of subclades. In the study, researchers investigated potential superinfection involving variations within HIV-1B.
In 28 of the 33 couples, each participant was infected with a strain of HIV-1B that was genetically different than that of the person’s partner, and the 28 couples were particularly relevant for these preliminary results.
The study also examined thirty other men who had many sexual partners and unprotected intercourse, and found only one individual had “super-infection,” and he had only recently sero-converted. There may indeed be a window early in infection, when super-infection can occur. But after that … it appears you can’t get reinfected. This is important news for a couple of reasons: first, the HIV-positive men have clearly developed some kind of immune response to new viral strains. Could this be developed into a vaccine? Second, the finding opens up a new possibility for restraining the epidemic. It makes a lot of sense for people with HIV only to have sex with other people with HIV. If neither man can get reinfected, they can also dispense with condoms, a benefit that could encourage them to stay having sex within their own HIV-positive sub-population (or within a monogamous HIV-positive relationship). This has a name: sero-sorting. It’s already happening informally, and may be one reason why, despite lots of anecdotal evidence of more condom-less sex, we haven’t seen huge increases in infection rates. It may be that the pozzies are all having sex with each other. Long may they continue to do so.
The Dish 