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Katherine G. Michel

Georgetown University

ORCID: 0000-0002-1852-9450

Publishes on Cervical Cancer and HPV Research, HIV/AIDS Research and Interventions, HIV-related health complications and treatments. 47 papers and 446 citations.

47Publications
446Total Citations

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Hormonal Contraception and HIV-1 Infection: Medroxyprogesterone Acetate Suppresses Innate and Adaptive Immune Mechanisms
Cited by 111Open Access

Recent observational studies indicate an association between the use of hormonal contraceptives and acquisition and transmission of HIV-1. The biological and immunological mechanisms underlying the observed association are unknown. Depot medroxyprogesterone acetate (DMPA) is a progestin-only injectable contraceptive that is commonly used in regions with high HIV-1 prevalence. Here we show that medroxyprogesterone acetate (MPA) suppresses the production of key regulators of cellular and humoral immunity involved in orchestrating the immune response to invading pathogens. MPA inhibited the production of interferon (IFN)-γ, IL-2, IL-4, IL-6, IL-12, TNFα, macrophage inflammatory protein-1α (MIP-1α), and other cytokines and chemokines by peripheral blood cells and activated T cells and reduced the production of IFNα and TNFα by plasmacytoid dendritic cells in response to Toll-like receptor-7, -8, and -9 ligands. Women using DMPA displayed lower levels of IFNα in plasma and genital secretions compared with controls with no hormonal contraception. In addition, MPA prevented the down-regulation of HIV-1 coreceptors CXCR4 and CCR5 on the surface of T cells after activation and increased HIV-1 replication in activated peripheral blood mononuclear cell cultures. The presented results suggest that MPA suppresses both innate and adaptive arms of the immune system resulting in a reduction of host resistance to invading pathogens.

Effect of Hormonal Contraception on the Function of Plasmacytoid Dendritic Cells and Distribution of Immune Cell Populations in the Female Reproductive Tract
Katherine G. Michel, Richard P. H. Huijbregts, Jonathan L. Gleason et al.|JAIDS Journal of Acquired Immune Deficiency Syndromes|2015
Cited by 47Open Access

OBJECTIVE: Epidemiological evidence suggests an association between the use of hormonal contraception and an increased risk of acquiring sexually transmitted diseases including HIV-1. We sought to elucidate the biological mechanisms underlying the effect of hormonal contraception on the immune system. DESIGN: Cross-sectional study. METHODS: To delineate the biological mechanisms underlying the effect of hormonal contraceptives on the immune system, we analyzed the functional capacity of circulating plasmacytoid dendritic cells (pDCs), the distribution of vaginal immune cell populations, and the systemic and genital levels of immune mediators in women using depot medroxyprogesterone acetate (DMPA), NuvaRing, or combined oral contraceptives (COC). RESULTS: The use of DMPA or NuvaRing was associated with reduced capacity of circulating pDCs to produce interferon (IFN)-α and tumor necrosis (TNF-α) in response to TLR-9 stimulation. Systemic levels of IFN-α and cervicovaginal fluid levels of IFN-α, CXCL10, monocyte chemotactic protein-1, and granulocyte-colony stimulating factor were significantly lower in DMPA users compared to control volunteers not using hormonal contraception. The density of CD207 Langerhans cells in the vaginal epithelium was reduced in NuvaRing and combined oral contraceptive users but not in DMPA users. CONCLUSIONS: The presented evidence suggests that the use of some types of hormonal contraception is associated with reduced functional capacity of circulating pDCs and altered immune environment in the female reproductive tract.

HIV Related Stigma among Healthcare Providers: Opportunities for Education and Training
Amanda B. Spence, Cuiwei Wang, Katherine G. Michel et al.|Journal of the International Association of Providers of AIDS Care (JIAPAC)|2022
Cited by 42Open Access

Background: HIV-stigma can influence engagement in care and viral suppression rates among persons living with HIV (PLWH). Understanding HIV-provider level stigma and its associated factors may aid in development of interventions to improve engagement in care. Methods: We assessed HIV-related stigma, provider knowledge, and practices and beliefs among healthcare providers using an online survey tool. Generalized linear modeling was used to determine factors associated with HIV-stigma score. Results: Among 436 participants, the mean age was 42.3 (SD 12.3), 70% female, 62% white, 65% physicians, and 44% worked at an academic center. The mean HIV Health Care Provider Stigma Scale (HPASS) score was 150.5 (SD 18.9, total = 180 [higher score = less stigma]) with factor subscale scores of 67.1 (SD 8.2, total = 78) prejudice, 51.3 (SD 9.7, total = 66) stereotyping, and 32.1 (SD 5, total = 36) discrimination. Female sex and comfort with talking about sex and drug use had 4.97 (95% CI 0.61, 9.32) and 1.99 (95% CI 0.88, 3.10) estimated higher HPASS scores. Disagreement/strong disagreement versus strong agreement with the statement that PLWH should be allowed to have babies and feeling responsible for talking about HIV prevention associated with −17.05 (95% CI −25.96, −8.15) and −2.16 (95% CI −3.43, −0.88) estimated lower HPASS scores. Conclusions: The modifiable factors we identified as associated with higher HIV related stigma may provide opportunities for education that may ameliorate these negative associations.

Menopause Is Associated With Immune Activation in Women With HIV
Brandilyn A. Peters, Xiaonan Xue, Lila A. Sheira et al.|The Journal of Infectious Diseases|2021
Cited by 24Open Access

BACKGROUND: Persistent immune activation due to gut barrier dysfunction is a suspected cause of morbidity in HIV, but the impact of menopause on this pathway is unknown. METHODS: In 350 women with HIV from the Women's Interagency HIV Study, plasma biomarkers of gut barrier dysfunction (intestinal fatty acid binding protein; IFAB), innate immune activation (soluble CD14 and CD163; sCD14, sCD163), and systemic inflammation (interleukin-6 and tumor necrosis factor receptor 1; IL-6, TNFR1) were measured at 674 person-visits spanning ≤2 years. RESULTS: Menopause (post- vs premenopausal status) was associated with higher plasma sCD14 and sCD163 in linear mixed-effects regression adjusting for age and other covariates (β = 161.89 ng/mL; 95% confidence interval [CI], 18.37-305.41 and 65.48 ng/mL, 95% CI, 6.64-124.33, respectively); but not with plasma IFAB, IL-6, or TNFR1. In piece-wise linear mixed-effects regression of biomarkers on years before/after the final menstrual period, sCD14 increased during the menopausal transition by 250.71 ng/mL per year (95% CI, 16.63-484.79; P = .04), but not in premenopausal or postmenopausal periods. CONCLUSIONS: In women with HIV, menopause may increase innate immune activation, but data did not support an influence on the gut barrier or inflammation. Clinical implications of immune activation during menopausal transition warrant further investigation.