Incidence of HIV-1 Dual Infection and Its Association with Increased Viral Load Set Point

This longitudinal study aimed to determine the incidence and pathogenic implications of dual human immunodeficiency virus type 1 (HIV-1) infection in a cohort of female sex workers.

Blood samples from 31 recently infected women were screened by use of a heteroduplex mobility assay and sequencing.

The median viral load set point was 5404 copies/mL (n = 22), which was measured by use of the bDNA assay.

Results

Within 3 months of infection, 19% (6/31) of the women were dually infected with 2 distinct HIV-1 subtype C viruses.

No evidence of superinfection was detected over the course of 24 months of follow-up, indicating that the risk of dual infection is highest around the time of the initial infection.

There was a significant association between dual infection and elevated viral load set point.

Discussion

The present study is the first natural-history study to follow highly exposed HIV-1 subtype Cinfected African women from the time of seroconversion and to show the incidence of dual infection and its effect on viral load set point.

The data in the present study support those of a previous study that predominantly focused on subtype B (n = 4) but included the individual in the present cohort who experienced rapid progression (Du151). This previous study reported on 5 dually infected individuals who progressed to AIDS or died within 2 years of infection.

The incidence of dual infection in the present study's subtype C-infected cohort of high-risk women (19%) was higher than the incidence found in a subtype B-infected cohort of men (12%). The risk of dual infection was highest close to the time of infection.

The present study has provided some insight into natural control of virus in a highly exposed cohort, and larger studies will be needed to determine whether multiple exposures at the mucosal interface leads to development of protective immunity and consequently lower viral loads.

In addition, it is not known whether dual infection or transmission of multiple divergent variants, enables rapid adaptation and immune escape, resulting in faster disease progression, or whether people who are genetically predisposed to experience rapid disease progression are unable to control viral diversity, enabling establishment of dual infections.

The possible pathogenic implications of dual infection suggest that HIV-concordant sex partners should continue to protect themselves from dual infection. Understanding the protective mechanisms associated with dual infection would provide vital information useful to our understanding of correlates of protection and contribute to vaccine design.

Institute for Infectious Diseases and Molecular Medicine, Division of Medical Virology, University of Cape Town, Observatory, and South African National Bioinformatics Institute, Bellville, Capetown, and National Institute for Communicable Diseases, Sandringham, Johannesburg, and Medical Research Council, and Centre for the AIDS Programme of Research in South Africa, University of Natal, Durban, South Africa.

09/08/04

Reference
J Grobler and others. Incidence of HIV-1 Dual Infection and Its Association with Increased Viral Load Set Point in a Cohort of HIV-1 Subtype C-Infected Female Sex Workers. The Journal of Infectious Diseases 190(7): 1355-1359. October 1, 2004.