Absence of HIV-1 superinfection 1 year after infection between 1985 and 1997 coincides with a reduction in sexual risk behavior in the seroincident Amsterdam cohort of homosexual men.

BACKGROUND

Incidence rates of human immunodeficiency virus type 1 (HIV-1) superinfection differ among cohorts and, as yet, only 2 cohorts of homosexual men have been screened. Here, we investigated the incidence of HIV-1 superinfection during the first year after infection among homosexual participants in the Amsterdam Cohort Studies on HIV infection and AIDS who seroconverted between 1985 and 1997.

METHODS

We analyzed env C2-C4 diversity in the serum of therapy-naive participants, using a heteroduplex mobility assay; heteroduplexes were considered to be indicators of potential dual infections, in which case env C2-C4 polymerase chain reaction (PCR) products were cloned and sequenced. Sequences were subjected to phylogenetic analysis. Data on the sexual behavior of participants were collected from 1 year before seroconversion until the end of the investigated period.

RESULTS

For 89 seroconverters with a detectable viral load (>1000 copies/mL), env PCR products were generated from serum samples obtained at seroconversion and 1 year later. Heteroduplexes were observed in 68 of the 89 patients; among these 68 patients, a median of 9 molecular clones per time point was sequenced. Phylogenetic analysis did not reveal evidence for superinfection; 1 patient was HIV-1 coinfected. Shortly after diagnosis of HIV infection, the number of sex partners decreased, the frequency of anal intercourse declined, and condom use increased.

CONCLUSIONS

The incidence of HIV-1 superinfection soon after seroconversion in this cohort is low. Risk reduction shortly after HIV-1 diagnosis early during the HIV-1 epidemic in the Netherlands may have contributed to the absence of HIV-1 superinfection observed in this study.