Objective: To determine whether HIV-1 replicates locally in the female genital tract during therapy, and to study whether endocervix is the dominant source of virus in cervicovaginal lavage fluid.
Design: Sequence analyses of HIV-1 pol were performed from cervicovaginal secretions and blood plasma of HIV-infected women failing antiretroviral therapy with detectable viral load in both compartments, as well as from drug-naive subjects.
Methods: Viral RNA was extracted from cervicovaginal lavage fluid, endocervical secretions collected by Sno-strips, and blood plasma. Population sequencing of HIV-1 pol was performed using cycle sequencing. Drug resistance mutations were analyzed. Phylogenies were constructed based on synonymous positions in the sequences.
Results: Resistant virus was detected concordantly in blood and genital tract specimens, consistent with drug selection pressure in both compartments. However, drug-selected mutations often differed in each compartment, and phylogenetic analysis showed differences in virus lineage in these compartments, consistent with local replication in female genital tract. Viruses in cervicovaginal lavage and endocervical secretions were genetically distinguishable, suggesting that endocervix is not the only source of virus found in cervicovaginal lavage.
Conclusion: These data support the hypothesis that HIV replication is compartmentalized within the female genital tract during antiretroviral therapy, which has implications for pathogenesis and for epidemiologic surveillance of drug-resistant virus.
Cervicovaginal secretions can transmit HIV-1 vertically and horizontally. After antiretroviral therapy is started, viral load in cervicovaginal secretions may decline more rapidly than does viral load in blood plasma, 1 and drug responses are as durable in cervicovaginal secretions as in blood. 2 However, antiretroviral drug-resistant virus has been identified in female genital tract specimens. 3-5 Heterosexual and vertical transmission of drug-resistant HIV-1 is occurring. 6,7
Although HIV may replicate independently in the male genital tract relative to blood, 8 and virus in semen may lack resistance mutations found in contemporaneous virus in blood, there are fewer comparisons of nucleotide sequences and resistance mutations in HIV RNA in blood plasma versus female genital tract secretions. In a few subjects, some phylogenetic or mutational differences have been noted between blood and cervicovaginal lavage (CVL) fluid sequences. 3 Further characterization is needed to determine whether genetic differences, including drug-selected mutations, occur in female genital secretion-derived virus versus blood as a result of localized replication. If confirmed, monitoring genital tract as well as blood specimens may improve the surveillance for drug-resistant HIV-1.
The possible sources of HIV-1 RNA originating within the female genital tract are also not yet fully defined. Submucosal lymphoid cells are likely to be the major host cells for HIV-1 replication. Viral load is higher in endocervical canal fluid collected by Sno-strips compared with cervicovaginal fluid. 9 This suggests that the endocervix may be the dominant source of virus in CVL fluid. Genetic comparisons of endocervical secretions versus CVL fluid that can address this question have been limited to date.
We undertook this study to evaluate whether drug-selected pol mutations occurred in the female genital tract as well as blood HIV RNA in women treated with antiretroviral therapy who had detectable viral load in both blood and genital tract. We also studied whether HIV pol phylogenies were consistent with localized replication in the female genital tract and the hypothesis that the endocervix was the dominant source of virus in CVL fluid.