Determinants of Genital Shedding of Human Immunodeficiency Virus: A Review
Sexual transmission is the main route for Human Immunodeficiency Virus (HIV) spreading throughout the world. Heterosexual transmission of HIV is the predominant transmission modality among adults worldwide, while mother-to-child transmission accounts for the majority of HIV infections in children. Factors that affect genital tract shedding of the HIV virus or cell-associated provirus in women are probably important determinants of infectiveness, and hence of transmission risk during sexual contact or delivery. Cervical inflammation and genital ulcers have been associated with HIV shedding in the female genital tract. In fact, both ulcerative sexually transmitted infections (syphilis, chancroid and herpes) and non-ulcerative sexually transmitted infections (gonorrea and chlamydia) have been associated with high rates of transmission and acquisition of HIV. Bacterial vaginosis are associated with an increased prevalence of HIV1-RNA detection in cervicovaginal secretions. Although HIV infection is a well-known risk factor for cervical intraepithelial neoplasia (CIN), the influence of CIN on cervical shedding of HIV is poorly understood. Preliminary data suggest that CIN lesions represent a significant risk factor for genital HIV spreading. Additional factors associated with increased prevalence of HIV1-RNA detection are: advanced stage of the disease, hormonal contraceptive use, cervical ectopy, vitamin A deficiency, cervicitis and vulvovaginal candidiasis. In contrast to the lower female genital tract, the male genital tract is inaccessible to simple direct sampling. Poor detection and quantification of the HIV-1 virus in the semen have largely limited our knowledge of HIV infectivity in men. Symtomatic and asymptomatic urethritis are important cofactors for HIV shedding in the semen, suggesting that local genital tract infection are important determinants of HIV level in semen. Finally, the presence of HIV-RNA in blood strongly correlates with the detection of HIV-related nucleic acids in genital secretions but the shedding of HIV in the genital tract can occur in 20-30% of non-viremic subjects.
Keywords: HIV-1 RNA, genital shedding, cervicovaginal secrections, viral load, infectivity, sexual transmission
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