Dr. Smith and colleagues presented their experience looking for cases of HIV superinfection in the cohort of HIV-positive patients that they followed after identification of primary infection.
The topic of superinfection is important for several reasons. First, it provides important insight into protective anti-HIV immunity. The issue is whether the innate anti-HIV immunity that evolves in an infected person can prevent infection with a second strain of HIV. That is important clinically since a few anecdotal reports have suggested that superinfection can lead to more rapid deterioration of a patient's immune status. It is also important from the public health perspective with implications for the potential efficacy of a vaccine to prevent infection.
Several definitions need to be clarified. Co-infection describes when someone is initially infected with two strains, while with superinfection a patient is infected with one strain and then with another strain. Superinfection has been observed in some chimpanzee models and has been inferred from recombination analysis but is still a rarely documented clinical event.
Smith reported the results of a retrospective analysis of trials of primary infection in a cohort of 78 men who have sex with men (MSM) during their first six months living with HIV infection. These men were not yet on antiretroviral therapy. Samples of virus underwent pol gene sequencing and if isolates didn't cluster then env sequencing was done.
Three cases of possible superinfection with another type B virus were identified and then confirmed by clonal sequencing of env and pol sequences. All three men had a change in the reverse transcriptase sequence that could impact drug sensitivity. When those three patients were evaluated six months after acquiring the second strain, a negative impact on the CD4 count and RNA level was seen.
The 5% rate of superinfection is about the same rate as at risk infection initial infection in high-risk populations in the U.S. The interpretation was that there was no protection afforded by the initial HIV infection against superinfection. Dr. Smith said that the lab approach may underestimate the true rate of superinfection due to sensitivity issues with the assays used. It seems to me that a group of MSM with fairly recent HIV infection may represent a group with a higher than average risk for acquiring additional HIV so that extrapolation to the general MSM population may overestimate the overall risk. Whatever the actual rate is, these data add to the literature about superinfection and support enhanced emphasis on harm reduction counseling. A question from the audience highlighted that of the three cases reported, two had been previously reported in other reports. Clearly the topic is of interest and more studies looking at the rate and impact of superinfection are needed.
Abstract: Incidence of HIV Superinfection Following Primary Infection (Oral 21)
Authored by: D. Smith, J. Wong, G. Hightower, K. Kolesch, C. Ignacio, E. Daar, D. Richman, S. Little
Affiliations: Univ. of California, San Diego, CA; Univ. of California, Los Angeles, CA; San Diego VA Healthcare Systems, La Jolla, CA