title: Comparison of HIV-1 and HIV-2 infectivity from a prospective cohort study in Senegal.
abstract: From a prospective cohort study of 1948 initially human immunodeficiency virus (HIV) uninfected female commercial sex workers followed between 1985 and 1999 in Dakar, Senegal, the authors compared the male to female per infectious sexual exposure transmission probability of HIV types one (HIV-1) and two (HIV-2). New non-parametric competing risks failure time methods were used, which minimized modelling assumptions and controlled for risk factors for HIV infection. The HIV-1 versus HIV-2 infectivity ratio over time was estimated by the ratio of smoothed non-parametric kernel estimates of the HIV-1 and HIV-2 infection hazard functions in sex workers, adjusted by an estimate of the relative HIV-1 versus HIV-2 prevalence in the partner population. HIV-1 was found to be significantly more infectious than HIV-2 throughout the follow-up period (P < 0.001). The HIV-1/HIV-2 infectivity ratio was inferred to be approximately constant over time, with estimated common value 3.55. The finding of greater HIV-1 infectivity persisted in sensitivity analyses and in covariate-adjusted analyses, with adjusted infectivity ratio estimates ranging between 3.40 and 3.86. Understanding the mechanisms by which HIV-1 infects more efficiently than HIV-2 may be useful in the development of HIV-1 vaccines. Additionally, the methodology developed here may be useful for analysing other data sets.
authors.affiliation: Statistical Center for HIV/AIDS Research and Prevention, Fred Hutchinson Cancer Research Center and Department of Biostatistics, University of Washington, Seattle, WA 98105, U.S.A. pgilbert@scharp.org
authors.forename: Peter B
authors.initials: PB
authors.lastname: Gilbert
authors.forename: Ian W
authors.initials: IW
authors.lastname: McKeague
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Eisen
authors.forename: Christopher
authors.initials: C
authors.lastname: Mullins
authors.forename: Aissatou
authors.initials: A
authors.lastname: Guéye-NDiaye
authors.forename: Souleymane
authors.initials: S
authors.lastname: Mboup
authors.forename: Phyllis J
authors.initials: PJ
authors.lastname: Kanki
mesh_terms: D000293:Adolescent; D000328:Adult; D015331:Cohort Studies; D005260:Female; D015658:HIV Infections / Q000453:epidemiology* / Q000635:transmission / Q000821:virology; D015497:HIV-1 / Q000472:pathogenicity*; D015498:HIV-2 / Q000472:pathogenicity*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D011446:Prospective Studies; D018570:Risk Assessment / Q000706:statistics & numerical data*; D012675:Senegal / Q000453:epidemiology; D011477:Sex Work; D012749:Sexually Transmitted Diseases / Q000453:epidemiology* / Q000635:transmission / Q000821:virology; D014774:Virulence