McKinnon, Lyle R.

Sivro, Aida.

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1484 • JID 2017:216 (15 December) • EDITORIAL COMMENTARYThe Journal of Infectious DiseasesThe Journal of Infectious Diseases®  2017;216:1484–6Mucosal HIV Shedding During ARTAida Sivro1,2 and Lyle R. McKinnon1,2,31Centre for the AIDS Programme of Research in South Africa, Durban; 2Department of Medical Microbiology, University of Manitoba, Winnipeg, Canada; and 3Department of Medical Microbiology, University of Nairobi, Kenya(See the major article by King et al, on pages 1534–40.)Keywords. HIV; mucosal; viral shedding; antiretroviral therapy; Africa. Viral load (VL) of human immunodefi-ciency virus (HIV) in the HIV-infected partner is the best described correlate of heterosexual HIV transmission, with each order of magnitude of VL associated with a 2- to 3-fold increased risk for the HIV-uninfected partner (both male-to-female and female-to-male) [1]. While antiretro-viral therapy (ART) can dramatically reduce the rate of HIV transmission [2], placing this at the forefront of HIV prevention strategies, its effectiveness is contingent on consistent VL suppression [3]. Because a large propor-tion of HIV transmission occurs via sexual intercourse, the assumption was that by re-ducing plasma VL (PVL), ART is in parallel reducing genital VL (GVL). However, if this was not the case, the hypothesis was that suppressed PVL might not predict instances of onward HIV transmission due to “iso-lated” mucosal HIV shedding (PVL neg-ative but GVL positive). Studies in semen have demonstrated that local shedding can be persistent and at levels corresponding to “transmissible” virus [4]. Indeed, although PVL has correlated with GVL in studies of both male and female genital secretions [5], this correlation was typically modest, and many found that a proportion of individuals are GVL positive even though PVL is unde-tectable, suggesting that local factors could influence the risk of transmission [6]. This was further supported by evidence that GVL also correlated with HIV transmission risk, independent of PVL [7]. Together these studies have suggested that a better under-standing of how often, and in what circum-stances, mucosal shedding of HIV occurs during effective HIV treatment might have important HIV-prevention implications.In this issue of the Journal of Infectious Diseases, King et al report a large prospec-tive study of >1100 African women on ART carried out to better understand the extent of, and potential contributors to, genital HIV shedding. This large study utilized specimens from 3 HIV clinical trials span-ning several central and southern African countries. Genital HIV RNA was detected in 6% of >1400 visits made by women with undetectable PVL and 24% of approxi-mately 400 visits by women with detectable PVL. Both of these estimates are well below those observed in untreated HIV infec-tion, where approximately three-quarters of individuals are GVL positive. Importantly, <1% of women with suppressed PVL shed GVL consistently. Although there was no change in the magnitude of viral shedding, there was a decrease in the proportion of visits with genital shedding with increased ART duration in those with undetectable PVL. This is consistent with a previous re-port that showed a decline in shedding up to 18  months on ART [8], and suggests that the source of HIV mucosal shedding may decrease relative to the rate of PVL suppression. The observed rate of genital shedding of 6% is slightly lower, but gener-ally consistent with, rates reported in pre-vious studies (typically 10%–15%) that have had more limited power (n  =  100–200) [9–11]. It is also consistent with studies that have suggested that ART leads to a rapid de-cline in GVL (more rapidly than PVL) [12], suggesting that ART is highly effective in re-ducing GVL levels.One important contribution added by this study is the large sample size and in-clusion of multiple study cohorts. While this increases the accuracy and general-izability of reported shedding rates, it also allows better characterization of predic-tors of shedding, which could be key to fu-ture interventions. The main predictors of genital shedding among women with un-detectable PVL included advanced WHO classification of HIV disease stage and presence of genital ulcers or cervical ten-derness, followed by type of ART regimen. The extent of HIV disease was found to influence HIV shedding in previous work [13], and may be indicative of increased systemic immune activation and immune dysregulation during chronic HIV infec-tion. One might infer that with earlier ART initiation, as per all current guidelines, the rate of HIV shedding may decline further.A long-standing hypothesis has sug-gested that local events may influence HIV shedding, as is supported by the finding that HIV shedding was associated with surrogates of genital inflammation (which are also a risk factor for HIV acquisition [14]). Indeed, this finding is supported E D I T O R I A L  C O M M E N T A R Y© The Author 2017. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.DOI: 10.1093/infdis/jix551Received 11 October 2017; editorial decision 11 October 2017; accepted 12 October 2017; published online December 12, 2017.Correspondence: L. R. McKinnon, PhD, 504-745 Bannatyne Ave, Winnipeg MB R3E 0J9 (lyle.mckinnon@umanitoba.ca).15December216Downloaded from https://academic.oup.com/jid/article-abstract/216/12/1484/4733302by Tarryn Leslie useron 09 March 2018EDITORIAL COMMENTARY • JID 2017:216 (15 December) • 1485by several early, smaller studies that have suggested associations between cervical HIV shedding and increased frequencies of immune cells [15–18], higher mucosal cytokine levels [19, 20], cervical infections, herpes simplex type 2 reactivation, and/or vaginal dysbiosis [21–24]. Although the authors did not observe any effect of chla-mydia and gonococcal infections on HIV shedding, this is likely due to low preva-lence of these STIs. One weakness of the study is that many potential biological correlates of shedding were not measured, resulting in inability to determine the im-pact of these and whether they may have confounded the other predictors. One potential focus of future studies could be cytomegalovirus (CMV), an important opportunistic pathogen in HIV-infected individuals. In individuals with ART-suppressed HIV infection, CMV often reactivates asymptomatically and contrib-utes to persistent immune activation and ongoing inflammation [25, 26]. However, because the HIV shedding observed by King et al was relatively uncommon, even if the specific factors predicting HIV shed-ding were to be identified, intervening may not carry significant public health impact if the predicted event is relatively rare be-cause of the effectiveness of ART itself.Another open question, related to local drivers of HIV shedding, is the under-lying source of HIV in the genital mu-cosa. The extent to which viral shedding is due to the blood supply to the mucosa and/or due to local viral reservoirs is still unclear and likely depends on both the extent of viral replication at different an-atomical sites and on levels of local and systemic inflammation. Blood flow could deliver cell-free virus to tissues and/or enhance the infection of local CD4 T cells. A  case can also be made for com-partmentalization of virus, as has been observed in virologic differences between the genital and systemic compartments [27]. One interpretation of the data, in-cluding the modest correlation between PVL and GVL, coupled with the obser-vation of local drivers of HIV shedding, might suggest that HIV shedding can result from both infected tissue and new virus that is introduced from systemic circulation.This study also addresses the question of the degree to which different ARVs are able to access different tissues. One recent study in SIV-infected nonhuman primates has suggested that extensive SIV RNA can be detected in multiple organ systems [28]. Suboptimal tissue penetration of the ARVs may not fully suppress viral production in the tissues, a result that is dependent on physiochemical properties of the ARVs as well as levels of tissue inflammation [29]. There are mixed reports in the literature regarding ART regimen and HIV mucosal shedding, and this issue is not entirely clari-fied by the current study. Future studies that do not rely on self-reported ART adherence data and instead female reproductive tract and plasma drug level measurements may provide more clarity. The choice of reg-imen could also be a confounding factor, if patients with different outcomes are given different regimens in the clinic; this is not really addressed by King et al. Finally, this issue will need to be re-evaluated as newer ART regimens become available, particu-larly those containing integrase inhibitors.Finally, although these results support the concept that women on ART with sup-pressed PVL may still be at risk of transmit-ting HIV, the extent to which HIV shedding defined by GVL contributes to actual HIV transmission remains unclear. No HIV transmissions to HIV uninfected partners were observed by King et  al (all partici-pants were in an HIV-discordant couple). This supports a previous report in which approximately 14 000 exposures did not lead to HIV transmission despite detection of shedding [13], evidence from an HIV Prevention Trials Network study (HPTN 502), where the only transmission was in a person yet to suppress PVL [2], and the lack of HIV transmission from PVL-suppressed individuals in the PARTNER study [30]. Therefore, the low rates of HIV shedding observed by King et al should be reassuring to those who are implementing test-and-treat strategies of HIV prevention. These data combined with previously published studies suggest that because HIV shedding is relatively uncommon and not associated with significant rates of HIV transmission, efforts to address the major challenges of increasing rates of HIV testing and achiev-ing sustained ART adherence may be most critical for success in combination HIV pre-vention [31]. That being said, the develop-ment of additional therapeutic modalities to reduce mucosal inflammation, microbial dysbiosis, and other genital infections—the burden of which is higher in HIV-positive individuals and which contribute to signifi-cant morbidity—would be a major benefit to women globally, regardless of whether there are any implications for HIV transmission.NotePotential conflicts of interest. Both authors: No reported conflicts of inter-est. Both authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.References 1. Quinn TC, Wawer MJ, Sewankambo N, et  al. Viral load and heterosexual transmission of human immunodefi-ciency virus type 1. Rakai Project Study Group. N Engl J Med 2000; 342:921–9. 2. Cohen MS, Chen YQ, McCauley M, et  al.; HPTN 052 Study Team. Prevention of HIV-1 infection with early antiretroviral therapy. N Engl J Med 2011; 365:493–505. 3. Hughes JP, Baeten JM, Lingappa JR, et  al.; Partners in Prevention HSV/HIV Transmission Study Team. Determinants of per-coital-act HIV-1 infectivity among African HIV-1-serodiscordant couples. J Infect Dis 2012; 205:358–65. 4. Sheth PM, Kovacs C, Kemal KS, et al.; Toronto Mucosal Immunology Group. Persistent HIV RNA shedding in semen despite effective antiretro-viral therapy. AIDS 2009; 23:2050–4. 5. 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Mucosal HIV shedding during ART.

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Mucosal HIV shedding during ART.

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