Tae Joon Yi

Impact of Asymptomatic Herpes Simplex Virus Type 2 Infection on Mucosal Homing and Immune Cell Subsets in the Blood and Female Genital Tract

HSV-2 infection is common and generally asymptomatic, but it is associated with increased HIV susceptibility and disease progression. This may relate to herpes-mediated changes in genital and systemic immunology. Cervical cytobrushes and blood were collected from HIV-uninfected African/Caribbean women in Toronto, and immune cell subsets were enumerated blindly by flow cytometry. Immune differences between groups were assessed by univariate analysis and confirmed using a multivariate model. Study participants consisted of 46 women, of whom 54% were infected with HSV-2. T cell activation and expression of the mucosal homing integrin α4β7 (19.60 versus 8.76%; p < 0.001) were increased in the blood of HSV-2–infected women. Furthermore, expression of α4β7 on blood T cells correlated with increased numbers of activated (coexpressing CD38/HLA-DR; p = 0.004) and CCR5+ (p = 0.005) cervical CD4+ T cells. HSV-2–infected women exhibited an increase in the number of cervical CD4+ T cells (715 versus 262 cells/cytobrush; p = 0.016), as well as an increase in the number and proportion of cervical CD4+ T cells that expressed CCR5+ (406 versus 131 cells, p = 0.001; and 50.70 versus 34.90%, p = 0.004) and were activated (112 versus 13 cells, p < 0.001; and 9.84 versus 4.86%, p = 0.009). Mannose receptor expression also was increased on cervical dendritic cell subsets. In conclusion, asymptomatic HSV-2 infection was associated with significant systemic and genital immune changes, including increased immune activation and systemic α4β7 expression; correlation of the latter with highly HIV-susceptible CD4+ T cell subsets in the cervix may provide a mechanism for the increased HIV susceptibility observed in asymptomatic HSV-2–infected women.

Genital immunology and HIV susceptibility in young women

Women account for a substantial majority of HIV infections in endemic regions, where women are also infected at a much younger age than men. Part of this epidemiological skewing is due to socio‐cultural factors, but it is clear that biological factors enhance the susceptibility of women – particularly young women – to HIV acquisition after sexual exposure. These factors, including important differences in mucosal immunology at the site of genital HIV exposure, are the focus of this concise review. Compared to heterosexual men, women have an increased surface area of mucosal HIV exposure, increased mucosal expression of the HIV co‐receptor CCR5 and a greater probability of virus exposure on the rectal mucosa. Differences that are specific to young women include a pro‐inflammatory immune environment and a proportionate increase in single‐cell, columnar genital epithelium. These important biological reasons for enhanced HIV susceptibility in young women highlight the need for targeted HIV prevention within this vulnerable population.

Mucosal correlates of isolated HIV semen shedding during effective antiretroviral therapy.

Effective antiretroviral therapy (ART) suppresses the blood HIV RNA viral load (VL) below the level of detection. However, some individuals intermittently shed HIV RNA in semen despite suppression of viremia, a phenomenon termed “isolated HIV semen shedding (IHS)”. In a previously reported clinical study, we collected blood and semen samples from HIV-infected men for 6 months after ART initiation, and documented IHS at ≥1 visit in almost half of the participants, independent of ART regimen or semen drug levels. We now report the mucosal immune associations of IHS in these men. Blood and semen plasma cytokine levels were assayed by multiplex enzyme-linked immunosorbent assay, T-cell populations were evaluated by flow cytometry in freshly isolated blood and semen mononuclear cells, and semen cytomegalovirus (CMV) DNA levels were measured by PCR. Although IHS was not associated with altered blood or semen cytokine levels, the phenomenon was associated with a transient, dramatic increase in CD4+ and CD8+ T-cell activation that was restricted to the semen compartment. All participants were CMV infected, and although semen CMV reactivation was common despite ART, this was not associated with T-cell activation or IHS. Further elucidation of the causes of compartmentalized mucosal T-cell activation and IHS may have important public health implications.

A Randomized Controlled Pilot Trial of Valacyclovir for Attenuating Inflammation and Immune Activation in HIV/Herpes Simplex Virus 2–Coinfected Adults on Suppressive Antiretroviral Therapy

BACKGROUND Human immunodeficiency virus (HIV) is associated with increased systemic inflammation and immune activation that persist despite suppressive antiretroviral therapy (ART). Herpes simplex virus type 2 (HSV-2) is a common coinfection that may contribute to this inflammation. METHODS Sixty HIV type 1 (HIV-1)/HSV-2-coinfected adults on suppressive ART were randomized 1:1:1 to 12 weeks of placebo, low-dose valacyclovir (500 mg twice daily), or high-dose valacyclovir (1 g twice daily) in this 18-week trial. Co-primary outcome measures were the percentage of activated (CD38(+)HLA-DR(+)) CD8 T cells in blood, and highly sensitive C-reactive protein, interleukin 6, and soluble intercellular adhesion molecule 1 in plasma. Secondary outcomes included additional immune, inflammatory cytokine, and endothelial activation markers. The impact of valacyclovir (both groups combined) on each outcome was estimated using treatment × time interaction terms in generalized estimating equation regression models. RESULTS Participants were mostly white (75%) men who have sex with men (80%). Median age was 51 (interquartile range [IQR], 47-56) years, median duration of HIV infection was 15 (IQR, 8-21) years, median CD4 count at enrollment was 520 (IQR, 392-719) cells/µL, and median nadir CD4 count was 142 (IQR, 42-240) cells/µL. Valacyclovir was not associated with significant changes in any primary or secondary immunological outcomes in bivariate or multivariable models. Medication adherence was 97% by self-report, 96% by pill count, and 84% by urine monitoring. Eight patients had adverse events deemed possibly related to the study drug (5 placebo, 1 low-dose, 2 high-dose), and 6 patients reported at least 1 HSV outbreak (3 placebo, 3 low-dose, 0 high-dose). CONCLUSIONS Valacyclovir did not decrease systemic immune activation or inflammatory biomarkers in HIV-1/HSV-2-coinfected adults on suppressive ART. CLINICAL TRIALS REGISTRATION NCT01176409.

Impact of antiretroviral therapy duration and intensification on isolated shedding of HIV-1 RNA in semen.

BACKGROUND Effective antiretroviral therapy (ART) dramatically reduces human immunodeficiency virus (HIV) transmission. However, isolated shedding of HIV type 1 (HIV-1) in semen (IHS) can occur in the absence of detectable viremia or genital infections. We hypothesized that ART intensification with medications active in semen might prevent IHS. METHODS Paired blood and semen samples were collected monthly for 6 months from HIV-infected men starting ART that was intensified (iART) with maraviroc and raltegravir in an open-label fashion. Semen parameters were compared to those of historical controls starting standard ART (sART). RESULTS Compared with 25 controls who started sART, the semen HIV-1 load in 13 subjects who started iART was more rapidly suppressed (P = .043). IHS was detected at >1 visit in 2 participants (15%) receiving iART and in 12 controls (48%) receiving sART (P = .040). Among iART recipients, IHS was associated with lower raltegravir concentrations in blood and semen, compared with complete HIV-1 suppression (P = .03). Prolonged, high-level IHS (ie, shedding of >5000 RNA copies/mL) was observed in 1 iART recipient (8%), despite rapid viremia suppression and therapeutic drug levels; for 10 months, this virus remained R5 tropic, drug susceptible, and similar in sequence to virus recovered from blood. IHS was not seen after >3 years of effective ART in a parallel, prospective cohort study. CONCLUSIONS iART transiently reduced the occurrence of IHS early after ART initiation but did not prevent high-level IHS. IHS was not seen after more prolonged sART.

Association of HPV infection and clearance with cervicovaginal immunology and the vaginal microbiota

Cervical human papillomavirus (HPV) infection may increase HIV risk. Since other genital infections enhance HIV susceptibility by inducing inflammation, we assessed the impact of HPV infection and clearance on genital immunology and the cervico-vaginal microbiome. Genital samples were collected from 65 women for HPV testing, immune studies and microbiota assessment; repeat HPV testing was performed after 6 months. All participants were HIV-uninfected and free of bacterial STIs. Cytobrush-derived T cell and dendritic cell subsets were assessed by multiparameter flow cytometry. Undiluted cervico-vaginal secretions were used to determine cytokine levels by multiplex ELISA, and to assess bacterial community composition and structure by 16S rRNA gene sequence analysis. Neither HPV infection nor clearance were associated with broad differences in cervical T cell subsets or cytokines, although HPV clearance was associated with increased Langerhans cells and HPV infection with elevated IP-10 and MIG. Individuals with HPV more frequently had a high diversity cervico-vaginal microbiome (community state type IV) and were less likely to have an L. gasseri predominant microbiome. In summary, HPV infection and/or subsequent clearance was not associated with inflammation or altered cervical T cell subsets, but associations with increased Langerhans cells and the composition of the vaginal microbiome warrant further exploration.

Distinct Effects of the Cervicovaginal Microbiota and Herpes Simplex Type 2 Infection on Female Genital Tract Immunology

Background Genital inflammation is a key determinant of human immunodeficiency virus (HIV) transmission, and may increase HIV-susceptible target cells and alter epithelial integrity. Several genital conditions that increase HIV risk are more prevalent in African, Caribbean, and other black (ACB) women, including bacterial vaginosis and herpes simplex virus type-2 (HSV-2) infection. Therefore, we assessed the impact of the genital microbiota on mucosal immunology in ACB women and microbiome-HSV-2 interactions. Methods Cervicovaginal secretions and endocervical cells were collected by cytobrush and Instead Softcup, respectively. T cells and dendritic cells were assessed by flow cytometry, cytokines by multiplex enzyme-linked immunosorbent assay (ELISA), and the microbiota by 16S ribosomal ribonucleic acid gene sequencing. Results The cervicovaginal microbiota of 51 participants were composed of community state types (CSTs) showing diversity (20/51; 39%) or predominated by Lactobacillus iners (22/51; 42%), L. crispatus (7/51; 14%), or L. gasseri (2/51; 4%). High-diversity CSTs and specific bacterial phyla (Gardnerella vaginalis and Prevotella bivia) were strongly associated with cervicovaginal inflammatory cytokines, but not with altered endocervical immune cells. However, cervical CD4+ T-cell number was associated with HSV-2 infection and a distinct cytokine profile. Conclusions This suggests that the genital microbiota and HSV-2 infection may influence HIV susceptibility through independent biological mechanisms.

Valacyclovir Therapy Does Not Reverse Herpes-Associated Alterations in Cervical Immunology: A Randomized, Placebo-Controlled Crossover Trial

Herpes simplex virus type 2 (HSV-2) infection is associated with a 3-fold increase in the risk of human immunodeficiency virus (HIV) acquisition, perhaps through alterations in mucosal HIV-susceptible target cells. We performed a clinical trial to assess the impact of herpes therapy on cervical immunology in HSV-2-infected, HIV-uninfected women from Africa or the Caribbean who were living in Toronto, Canada. Thirty participants received 1 g of valacyclovir orally each day for 2 months in a randomized double-blind, placebo-controlled, crossover trial. Valacyclovir did not reduce the number of cervical CD4(+) T cells, the number of dendritic cells, or the expression of proinflammatory cytokines and tended to increase the expression of the HIV coreceptor CCR5 and the activation marker CD69. Short-term valacyclovir therapy did not reverse HSV-2-associated alterations in genital immunology. Clinical Trials Registration. NCT00946556.

Effect of Intercurrent Infections and Vaccinations on Immune and Inflammatory Biomarkers Among Human Immunodeficiency Virus-Infected Adults on Suppressive Antiretroviral Therapy.

We used generalized estimating equations to quantify the impact of recent vaccination or intercurrent infections on immune and inflammatory biomarkers among 144 human immunodeficiency virus (HIV)-infected adults with HIV RNA < 50 copies/mL on antiretroviral therapy. These events were associated with a 2.244 µg/mL increase in high sensitivity C-reactive protein and should be routinely assessed in future studies.

Peroxisome Proliferator-Activated Receptor–δ Supports the Metabolic Requirements of Cell Growth in TCRβ-Selected Thymocytes and Peripheral CD4+ T Cells

During T cell development, progenitor thymocytes undergo a large proliferative burst immediately following successful TCRβ rearrangement, and defects in genes that regulate this proliferation have a profound effect on thymus cellularity and output. Although the signaling pathways that initiate cell cycling and nutrient uptake after TCRβ selection are understood, less is known about the transcriptional programs that regulate the metabolic machinery to promote biomass accumulation during this process. In this article, we report that mice with whole body deficiency in the nuclear receptor peroxisome proliferator-activated receptor–δ (PPARδmut) exhibit a reduction in spleen and thymus cellularity, with a decrease in thymocyte cell number starting at the double-negative 4 stage of thymocyte development. Although in vivo DNA synthesis was normal in PPARδmut thymocytes, studies in the OP9–delta-like 4 in vitro system of differentiation revealed that PPARδmut double-negative 3 cells underwent fewer cell divisions. Naive CD4+ T cells from PPARδmut mice also exhibited reduced proliferation upon TCR and CD28 stimulation in vitro. Growth defects in PPAR-δ–deficient thymocytes and peripheral CD4+ T cells correlated with decreases in extracellular acidification rate, mitochondrial reserve, and expression of a host of genes involved in glycolysis, oxidative phosphorylation, and lipogenesis. By contrast, mice with T cell–restricted deficiency of Ppard starting at the double-positive stage of thymocyte development, although exhibiting defective CD4+ T cell growth, possessed a normal T cell compartment, pointing to developmental defects as a cause of peripheral T cell lymphopenia in PPARδmut mice. These findings implicate PPAR-δ as a regulator of the metabolic program during thymocyte and T cell growth.