Systematic review of orogenital HIV-1 transmission probabilities

Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College London, London, UK.
International Journal of Epidemiology (Impact Factor: 9.18). 08/2008; 37(6):1255-65. DOI: 10.1093/ije/dyn151
Source: PubMed


The objective was to assess the risk of HIV transmission from orogenital intercourse (OI).
Systematic review of the literature on HIV-1 infectiousness through OI conducted according to MOOSE guidelines for reviews of observational studies. The PubMed database and bibliographies of relevant articles were searched to July 2007.
Of the titles, 56 214 were searched from which 10 potentially appropriate studies were identified; two additional studies were identified through bibliographies and one through discussion with experts. There were 10 included studies, providing estimates of transmission probabilities per-partner (n = 5), incidence per-partner (n = 3), per-study participant (n = 3, following initially seronegative individuals whose partners are of unknown serostatus) and per-act (n = 3). Only four of 10 studies reported non-zero estimates: two per-partner estimates (20%, 95% CI: 6-51, n = 10 and a model-based estimate, 1%, range 0.85-2.3%), one per-study participant estimate (0.37%, 95% CI: 0.10-1.34%) and one per-act estimate (0.04%, 95% CI: 0.01-0.17%). Upper bounds for the 95% CI for zero estimates tended to be relatively large due to the small study sample sizes: 9.0, 12.1 and 2.8% for per-partner; 4.7, 9.6 and 1.8 per 100 person-years for incidence per-partner; 4.4% per-study participant and 0.45 and 0.02% for per-act. Given the small number of studies, a meta-analysis was not considered appropriate.
There are currently insufficient data to estimate precisely the risk from OI exposure. The low risk of transmission evident from identified studies means that more and larger studies would be required to provide sufficient evidence to derive more precise estimates.

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    • "The probability of HIV transmission as a function of sexual practice was reviewed from modeling studies using empirical data to estimate the per-contact risk of HIV transmission independently for receptive and insertive anal sex [24]–[29]. There is general consensus that the HIV transmission rate associated with unprotected receptive anal sex is about 1.0%. "
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    ABSTRACT: Background Despite preventive efforts, HIV incidence remains high among men who have sex with men (MSM) in industrialized countries. Condoms are an important element in prevention but, given the high frequency of condom use and their imperfect effectiveness, a substantial number and proportion of HIV transmissions may occur despite condoms. We developed a model to examine this hypothesis. Methods We used estimates of annual prevalent and incident HIV infections for MSM in Ontario. For HIV-negative men, we applied frequencies of sexual episodes and per-contact HIV transmission risks of receptive and insertive anal sex with and without a condom and oral sex without a condom. We factored in the proportion of HIV-infected partners receiving antiretroviral therapy and its impact in reducing transmissibility. We used Monte-Carlo simulation to determine the plausible range for the proportion of HIV transmissions for each sexual practice. Results Among Ontario MSM in 2009, an estimated 92,963 HIV-negative men had 1,184,343 episodes of anal sex with a condom and 117,133 anal sex acts without a condom with an HIV-positive partner. Of the 693 new HIV infections, 51% were through anal sex with a condom, 33% anal sex without a condom and 16% oral sex. For anal sex with a condom, the 95% confidence limits were 17% and 77%. Conclusions The proportion of HIV infections related to condom failure appears substantial and higher than previously thought. That 51% of transmissions occur despite condom use may be conservative (i.e. low) since we used a relatively high estimate (87.1%) for condom effectiveness. If condom effectiveness were closer to 70%, a value estimated from a recent CDC study, the number and proportion of HIV transmissions occurring despite condom use would be much higher. Therefore, while condom use should continue to be promoted and enhanced, this alone is unlikely to stem the tide of HIV infection among MSM.
    PLoS ONE 09/2014; 9(9):e107540. DOI:10.1371/journal.pone.0107540 · 3.23 Impact Factor
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    • "while URAI is highest at 1.4% [2]. This heterogeneity in transmission at receptive exposure sites is well observed in the literature [3]–[6], but little is known on the biological factors that influence this phenomenon. "
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    ABSTRACT: Objective Sexual transmission of HIV occurs across a mucosal surface, which contains many soluble immune factors important for HIV immunity. Although the composition of mucosal fluids in the vaginal and oral compartments has been studied extensively, the knowledge of the expression of these factors in the rectal mucosa has been understudied and is very limited. This has particular relevance given that the highest rates of HIV acquisition occur via the rectal tract. To further our understanding of rectal mucosa, this study uses a proteomics approach to characterize immune factor components of rectal fluid, using saliva as a comparison, and evaluates its antiviral activity against HIV. Methods Paired salivary fluid (n = 10) and rectal lavage fluid (n = 10) samples were collected from healthy, HIV seronegative individuals. Samples were analyzed by label-free tandem mass spectrometry to comprehensively identify and quantify mucosal immune protein abundance differences between saliva and rectal fluids. The HIV inhibitory capacity of these fluids was further assessed using a TZM-bl reporter cell line. Results Of the 315 proteins identified in rectal lavage fluid, 72 had known immune functions, many of which have described anti-HIV activity, including cathelicidin, serpins, cystatins and antileukoproteinase. The majority of immune factors were similarly expressed between fluids, with only 21 differentially abundant (p<0.05, multiple comparison corrected). Notably, rectal mucosa had a high abundance of mucosal immunoglobulins and antiproteases relative to saliva, Rectal lavage limited HIV infection by 40–50% in vitro (p<0.05), which is lower than the potent anti-HIV effect of oral mucosal fluid (70–80% inhibition, p<0.005). Conclusions This study reveals that rectal mucosa contains many innate immune factors important for host immunity to HIV and can limit viral replication in vitro. This indicates an important role for this fluid as the first line of defense against HIV.
    PLoS ONE 06/2014; 9(6):e100820. DOI:10.1371/journal.pone.0100820 · 3.23 Impact Factor
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    • "Our value for the rate of HIV transmission is the average of the minimum (0.011) and maximum values (0.95) for the same parameter in Baggaley et al. [5] and Boily et al. [6]. We assumed that a death rate due to AIDS and KS coinfection would be 0.4; in our model, δ1 and δ2 are summed. "
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    ABSTRACT: We formulate a deterministic system of ordinary differential equations to quantify HAART treatment levels for patients co-infected with HIV and Kaposi's Sarcoma in a high HIV prevalence setting. A qualitative stability analysis of the equilibrium states is carried out and we find that the disease-free equilibrium is globally attracting whenever the reproductive number ℛ k < 1. A unique endemic equilibrium exists and is locally stable whenever ℛ k > 1. Therefore, reducing ℛ k to below unity should be the goal for disease eradication. Provision of HAART is shown to provide dual benefit of reducing HIV spread and the risk of acquiring another fatal disease for HIV/AIDS patients. By providing treatment to 10% of the HIV population, about 87% of the AIDS population acquire protection against coinfection with HIV and Kaposi's Sarcoma (KS). Most sub-Sahara African countries already have programmes in place to screen HIV. Our recommendation is that these programmes should be expanded to include testing for HHV-8 and KS counseling.
    Computational and Mathematical Methods in Medicine 11/2013; 2013:753424. DOI:10.1155/2013/753424 · 0.77 Impact Factor
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