Background: HIV-1 subtype C has emerged as the most prevalent strain of HIV-1 worldwide, leading to speculation that subtype C may be more transmissible than other subtypes. We compared the risk of HIV-1 transmission for subtype C versus non-C subtypes (A, D, G and recombinant forms) among heterosexual African HIV-1 serodiscordant couples.
Methods: We conducted a nested case–control analysis using data from two prospective cohort studies of heterosexual HIV-1 serodiscordant couples from six countries in eastern and southern Africa. Cases (N = 121) included incident HIV-1 transmissions that were established as linked within the serodiscordant partnership by viral sequencing; controls (N = 501) were nontransmitting HIV-1-infected partners. Subtype was determined for partial env and gag genes. Multiple logistic regression controlled for age and gender of the HIV-1-nfected partner and self-reported unprotected sex. Plasma and genital HIV-1 RNA concentrations were compared between subtype C and non-C subtypes using generalized estimating equations.
Results: HIV-1 subtype C was not associated with increased risk of HIV-1 transmission compared with non-C subtypes: env adjusted odds ratio (adjOR) 1.14 [95% confidence interval (CI) 0.74–1.75, P = 0.6] and gag adjOR 0.98 (95% CI 0.63–1.52, P = 0.9). Plasma and genital HIV-1 RNA levels did not differ significantly for subtype C versus non-C.
Conclusion: In a geographically diverse population of heterosexual African HIV-1 serodiscordant couples, subtype C was not associated with greater risk of HIV-1 transmission compared with non-C subtypes, arguing against the hypothesis that subtype C is more transmissible compared with other common subtypes.
aDepartment of Epidemiology
bDepartment of Global Health
cDepartment of Medicine
dDepartment of Pediatrics
eDepartment of Microbiology
fDepartment of Laboratory Medicine, University of Washington
gVaccine and Infectious Disease Institute, Fred Hutchinson Cancer Research Center, Seattle, Washington, USA
hKenya Medical Research Institute, Kisumu, Kenya
iDepartment of Medicine, Indiana University, Indianapolis, Indiana, USA
jDepartment of Obstetrics & Gynecology, University of Nairobi & Kenyatta National Hospital, Nairobi, Kenya
kLondon School of Hygiene and Tropical Medicine, London, UK.
Correspondence to Erin Kahle, University of Washington, 325 Ninth Avenue, Box 359927, Seattle, WA 98104, USA. Tel: +1 206 520 3816; fax: +1 206 520 3831; e-mail: firstname.lastname@example.org
Received 4 April, 2013
Revised 24 July, 2013
Accepted 31 July, 2013
A portion of this work was presented at the XIX International AIDS Conference, 22–27 July 2012, Washington, DC, USA. Abstract TUAC0101.