Adherence, safety, and choice of the monthly dapivirine vaginal ring or oral emtricitabine plus tenofovir disoproxil fumarate for HIV pre-exposure prophylaxis among African adolescent girls and young women: a randomised, open-label, crossover trial

BACKGROUND

Half of new HIV acquisitions in Africa occur in adolescent girls and young women. Pre-exposure prophylaxis (PrEP) with oral tenofovir disoproxil fumarate plus emtricitabine or the monthly dapivirine vaginal ring is efficacious but has lower adherence and effectiveness among adolescent girls and young women. We aimed to assess product adherence, safety, and choice of oral PrEP compared with the dapivirine ring among African adolescent girls and young women.

METHODS

MTN-034/REACH was a randomised, open-label, phase 2a crossover trial among HIV-seronegative, non-pregnant adolescent girls and young women aged 16-21 years at four clinical research sites in South Africa, Uganda, and Zimbabwe. Participants were randomly assigned (1:1) to either the dapivirine ring or daily oral PrEP (200 mg of emtricitabine and 300 mg of tenofovir disoproxil fumarate) for 6 months, then switched to the other product option for 6 months, followed by a third 6-month period in which participants were given a choice of oral PrEP, the dapivirine ring, or neither. Fixed block randomisation was used, stratified by site. The primary adherence endpoint was use of each product during the randomised periods, with high use defined as tenofovir-diphosphate concentrations greater than or equal to 700 fmol/punch (associated with taking an average of four or more tablets per week in the previous month) and greater than or equal to 4 mg dapivirine released from the returned ring (continuous use for 28 days in the previous month) based on residual drug concentrations. The primary safety endpoint was grade 2 or higher adverse events during each randomised period of 24 weeks of ring and oral PrEP. This trial is registered at ClinicalTrials.gov, NCT03593655.

FINDINGS

From Feb 6, 2019 to Sept 9, 2021, 396 adolescent girls and young women were screened, 247 of whom were enrolled and randomly assigned (6 months of the ring followed by 6 months of oral PrEP n=124; 6 months of oral PrEP followed by 6 months of the ring n=123). Median age was 18 years (IQR 17-19). 54 grade 2 or higher product-related adverse events were reported during oral PrEP and five during dapivirine ring use, with no product-related serious adverse events. High adherence was observed in 753 (57%) of the 1316 oral PrEP visits and 806 (57%) of the 1407 dapivirine ring visits. Four women acquired HIV during follow-up.

INTERPRETATION

Adherence was moderately high and similar between oral PrEP and the dapivirine ring with favourable safety and tolerability. Oral PrEP and the dapivirine ring are effective, safe, and well tolerated HIV prevention options for adolescent girls and young women who would benefit from a choice of PrEP formulations to meet their needs and preferences.

FUNDING

National Institutes of Health.

Microbial community-scale metabolic modeling predicts personalized short chain fatty acid production profiles in the human gut

Microbially-derived short chain fatty acids (SCFAs) in the human gut are tightly coupled to host metabolism, immune regulation, and integrity of the intestinal epithelium. However, the production of SCFAs can vary widely between individuals consuming the same diet, with lower levels often associated with disease. A systems-scale mechanistic understanding of this heterogeneity is lacking. We present a microbial community-scale metabolic modeling (MCMM) approach to predict individual-specific SCFA production profiles. We assess the quantitative accuracy of our MCMMs using in vitro, ex vivo, and in vivo data. Next, we show how MCMM SCFA predictions are significantly associated with blood-derived clinical chemistries, including cardiometabolic and immunological health markers, across a large human cohort. Finally, we demonstrate how MCMMs can be leveraged to design personalized dietary, prebiotic, and probiotic interventions that optimize SCFA production in the gut. Our results represent an important advance in engineering gut microbiome functional outputs for precision health and nutrition.

Baseline preferences for oral pre-exposure prophylaxis (PrEP) or dapivirine intravaginal ring for HIV prevention among adolescent girls and young women in South Africa, Uganda and Zimbabwe (MTN-034/IPM-045 study)

INTRODUCTION

Adolescent girls and young women (AGYW) in sub-Saharan Africa are disproportionately affected by the HIV epidemic and face an array of challenges using proven behavioral and biomedical prevention methods. To address the urgent need for expanding prevention options, we evaluated the baseline preferences of HIV prevention methods among participants enrolled in the MTN-034/REACH crossover trial along with their stated product preference prior to product initiation.

METHODS

AGYW aged 16-21 years were enrolled at 4 study sites: Cape Town and Johannesburg, South Africa; Kampala, Uganda; and Harare, Zimbabwe and randomly assigned to the sequence of using oral PrEP and the dapivirine ring for 6 months each, followed by a choice period in which they could choose either product (or neither) for an additional six months. Eligible AGYW were HIV-negative, not pregnant and using effective contraception for at least two months prior to enrollment. Descriptive statistics were used to summarize demographic and behavioral data while multinomial analysis was used to determine predictors of stated product preference (ring or oral PrEP).

RESULTS

Of the 247 AGYW enrolled in REACH, 34% were aged 16-17 and 89% had a primary partner.The median age of sexual debut was 16 years and 40% had ever been pregnant. At screening, 35% of participants were diagnosed with a sexually transmitted infection (STI), 39% had an AUDIT-C score associated with harmful drinking and 11% reported intimate partner violence in the past 6 months. Overall, 28% of participants, had CESD-10 scores suggestive of depressive symptoms (≥12) in the past week. At baseline, similar proportions stated a preference for the ring and oral PrEP (38.1% and 40.5% respectively), with 19% of participants stating they preferred both products equally. Only study site was significantly associated with product preference (P<0.05) with AGYW from Johannesburg having higher odds of preferring the ring and those from Kampala having higher odds of preferring both options equally.

CONCLUSIONS

We successfully enrolled African AGYW with a clear unmet need for HIV prevention. The balanced preference between the two products suggests that multiple biomedical prevention options may be appealing to this age group and could address their prevention needs.

Intimate Partner Violence and Engagement in the HIV Care Continuum among Women in Sub-Saharan Africa: A Prospective Cohort Study

Research suggests that women's experience of intimate partner violence (IPV) is associated with poor engagement in HIV care and treatment. However, most studies have been cross-sectional and conducted in North America. We examined the association between physical IPV and HIV care outcomes in a prospective cohort study of women living with HIV (WLHIV) in Malawi, South Africa, Uganda, and Zimbabwe. At enrollment, 15% of the 351 participants self-reported physical IPV. IPV experience was not associated with time to first engagement in HIV care or the proportion virally suppressed after 6 months on ART. Women reporting physical IPV were less likely to initiate ART within 6 months of becoming eligible (adjusted RR 0.74, 95% CI 0.53-1.03). IPV screening is critical to identify survivors and link them to appropriate services. However, addressing IPV may not increase engagement in HIV care or viral load suppression among WLHIV in sub-Saharan Africa.

Casting a Wide Net: HIV Drug Resistance Monitoring in Pre-Exposure Prophylaxis Seroconverters in the Global Evaluation of Microbicide Sensitivity Project

Global Evaluation of Microbicide Sensitivity projects in 4 countries demonstrated the feasibility of establishing an HIV drug resistance monitoring program for pre-exposure prophylaxis (PrEP). These projects will provide valuable information on seroconversions in the context of PrEP use and will serve to inform Ministries of Health and policy makers on the need for long-term surveillance approaches.

Background:

Evidence of HIV drug resistance (HIVDR) in individuals using oral pre-exposure prophylaxis (PrEP) who acquire HIV is limited to clinical trials and case studies. More data are needed to understand the risk of HIVDR with oral PrEP during PrEP rollout. Mechanisms to collect these data vary, and are dependent on cost, scale of PrEP distribution, and in-country infrastructure for the identification, collection, and testing of samples from PrEP seroconverters.

Methods:

The Global Evaluation of Microbicide Sensitivity (GEMS) project, in collaboration with country stakeholders, initiated HIVDR monitoring among new HIV seroconverters with prior PrEP use in Eswatini, Kenya, South Africa, and Zimbabwe. Standalone protocols were developed to assess HIVDR among a national sample of PrEP users. In addition, HIVDR testing was incorporated into existing demonstration projects for key populations.

Lessons learned:

Countries are supportive of conducting a time-limited evaluation of HIVDR during the early stages of PrEP rollout. As PrEP rollout expands, the need for long-term HIVDR monitoring with PrEP will need to be balanced with maintaining national HIV drug resistance surveillance for pretreatment and acquired drug resistance. Laboratory capacity is a common obstacle to setting up a monitoring system.

Conclusions:

Establishing HIV resistance monitoring within PrEP programs is feasible. Approaches to drug resistance monitoring may evolve as the PrEP programs mature and expand. The methods and implementation support offered by GEMS assisted countries in developing methods to monitor for drug resistance that best fit their PrEP program needs and resources.

Qualitative Study on the Acceptability of and Adherence to a Vaginal Ring for HIV Prophylaxis Among Adolescent Girls

OBJECTIVE

This study aims to assess the product-related, relationship-related, and sex-related factors that act as facilitators and barriers to the acceptability of a vaginal ring (VR) for HIV prevention among adolescent girls.

DESIGN

Qualitative study.

METHODS

Ninety-six girls aged 15-17 years from 6 urban US sites were enrolled in MTN-023/IPM 030, a 24-week randomized controlled trial, for assessing the safety and acceptability of a dapivirine VR for HIV prevention. At week 24, 21 girls were randomly selected to participate in in-depth interviews. Interviews were transcribed verbatim and data analyzed using a thematic analysis approach. Facilitators and barriers to VR acceptability related to participants' relationships, sexual activity, and characteristics of the VR product were identified.

RESULTS

Factors related to relationships rarely seemed to act as barriers to VR acceptability; most participants disclosed VR use to sexual partners, and positive reactions from sexual partners, which were common, seemed to facilitate VR acceptability. Emotional and/or physical discomfort surrounding VR use during sex was mentioned occasionally as a barrier to VR acceptability. Product characteristics were most frequently mentioned as barriers to VR acceptability. Many participants reported concerns about the large size of the VR on first impression. Although most found the VR comfortable, some reported pain with VR insertion. Several participants were concerned about VR cleanliness, particularly during menstruation.

CONCLUSION

Product considerations, specifically size and use during menstruation, were the most commonly reported barriers to VR acceptability in this study. Adolescent girls may require additional counseling to assuage product concerns regarding a VR for HIV prevention.

Modeling uranium and 226Ra mobility during and after an acidic in situ recovery test (Dulaan Uul, Mongolia)

This article presents the results of groundwater monitoring over a period of six years and the interpretation of these results by a reactive transport model, following an In Situ Recovery (ISR) test on the Dulaan Uul uranium deposit in Mongolia. An environmental monitoring survey was set up using 17 piezometers, from which it has been possible to describe the changes in the water composition before, during and after the ISR test. The water quality before the start of mining activities rendered it unfit for human consumption. During and after the test, a descent of the saline plume was observed, resulting in a dilution of the injection solutions. After a rapid decrease to pH = 1.13 during the production phase of the ISR test, the pH stabilized at around 4 in the production area and 5.5 below the production cell one year after the end of the test. Uranium and radium were being naturally attenuated. Uranium returned to background concentrations (0.3 mg/L) after two years and the measured ²²⁶Ra concentrations represent no more than 10% of the expected concentrations during production (75 Bq/L). The modeling of the contaminants of concern mobility, namely pH and concentrations of sulfate, uranium and ²²⁶Ra, is based on several key complementary mechanisms: density flow, cation exchange with clay minerals and co-precipitation of ²²⁶Ra in the barite. The modeling results show that the observed plume descent and sulfate dilution can only be predicted if consideration of a high-density flow is included. Similarly, the changes in pH and ²²⁶Ra concentration are only correctly predicted when the cationic exchanges with the clays and the co-precipitation reaction within the barite using the solid solution theory are integrated into the models. Finally, the proper representation of the changes in water composition at the scale of the test requires the use of a sufficiently fine mesh (1 m × 1 m cell) to take into account the spatial variability of hydrogeological (permeability distribution in particular) and geological (reduced, oxidized and mineralized facies distributions) parameters.

Effect of a Flaxseed Lignan Intervention on Circulating Bile Acids in a Placebo-Controlled Randomized, Crossover Trial

Plant lignans and their microbial metabolites, e.g., enterolactone (ENL), may affect bile acid (BA) metabolism through interaction with hepatic receptors. We evaluated the effects of a flaxseed lignan extract (50 mg/day secoisolariciresinol diglucoside) compared to a placebo for 60 days each on plasma BA concentrations in 46 healthy men and women (20-45 years) using samples from a completed randomized, crossover intervention. Twenty BA species were measured in fasting plasma using LC-MS. ENL was measured in 24-h urines by GC-MS. We tested for (a) effects of the intervention on BA concentrations overall and stratified by ENL excretion; and (b) cross-sectional associations between plasma BA and ENL. We also explored the overlap in bacterial metabolism at the genus level and conducted in vitro anaerobic incubations of stool with lignan substrate to identify genes that are enriched in response to lignan metabolism. There were no intervention effects, overall or stratified by ENL at FDR < 0.05. In the cross-sectional analysis, irrespective of treatment, five secondary BAs were associated with ENL excretion (FDR < 0.05). In vitro analyses showed positive associations between ENL production and bacterial gene expression of the bile acid-inducible gene cluster and hydroxysteroid dehydrogenases. These data suggest overlap in community bacterial metabolism of secondary BA and ENL.

Effect of a Flaxseed Lignan Intervention on Circulating Bile Acids in a Randomized, Crossover Trial

Objectives

Health benefits of high-fiber foods may be attributed, in part, to microbial metabolites of plant compounds. Lignans and their microbial metabolites, the enterolignans [enterolactone (ENL) and enterodiol (END)], reduce serum lipids through a variety of mechanisms, including regulation of bile acid (BA) synthesis. BA, released into the gut lumen in response to dietary fat, undergo microbial metabolism to secondary (2°) BA, which have been positively associated with chronic disease, e.g., liver disease and colorectal cancer. Our aims were to evaluate the effects of a flaxseed lignan supplement on circulating BA and examine associations between enterolignans and 2° BA.

Methods

We conducted a randomized, crossover trial of a flaxseed lignan supplement (50 mg/d secoisolariciresinol diglucoside) compared to placebo in 46 healthy men and women (20-45 y). Each period lasted 60 days, separated by a 60-day washout period. Six primary and fourteen 2° BA species were measured in fasting plasma using LC-MS. ENL and END were measured in 24-h urines by GC-MS. Low- and high-ENL excreters were defined as below and above the median 24-h ENL excretion at the end of the flaxseed lignan intervention (23.4 µmol/24 h). Linear mixed models were used to a) test the effects of the intervention on individual BA concentrations, overall and stratified by low and high ENL excreters; and b) to cross-sectionally determine the association between plasma 2o BA and ENL and END.

Results

There was no significant effect of the flaxseed lignan intervention compared to placebo on BA concentrations overall, or by ENL-excreter status, after FDR adjustment. In the cross-sectional analysis, irrespective of treatment, six 2° BA were statistically significantly associated with ENL (FDR &lt; 0.05), with two positive associations (isolithocholic and lithocholic acids), and four inverse associations (glycoursodeoxycholic, glycohyodeoxycholic, hyodeoxycholic, and muricholic acids).

Conclusions

The flaxseed lignan intervention and subsequent ENL production had no effect on plasma BA concentrations. However, the strong associations between ENL excretion and certain 2° BA concentrations suggests that the gut microbial communities capable of producing ENL may also play a role in 2° BA metabolism.

Funding Sources

NIH.

Modulation of Gut Microbiota by Glucosamine and Chondroitin in a Randomized, Double-Blind Pilot Trial in Humans

Glucosamine and chondroitin (G&C), typically taken for joint pain, are among the most frequently used specialty supplements by US adults. More recently, G&C have been associated with lower incidence of colorectal cancer in human observational studies and reduced severity of experimentally-induced ulcerative colitis in rodents. However, little is known about their effects on colon-related physiology. G&C are poorly absorbed and therefore metabolized by gut microbiota. G&C have been associated with changes in microbial structure, which may alter host response. We conducted a randomized, double-blind, placebo-controlled crossover trial in ten healthy adults to evaluate the effects of a common dose of G&C compared to placebo for 14 days on gut microbial community structure, measured by 16S rRNA gene sequencing. Linear mixed models were used to evaluate the effect of G&C compared to placebo on fecal microbial alpha and beta diversity, seven phyla, and 137 genera. Nine genera were significantly different between interventions (False Discovery Rate < 0.05). Abundances of four Lachnospiraceae genera, two Prevotellaceae genera, and Desulfovibrio were increased after G&C compared to placebo, while Bifidobacterium and a member of the Christensenellaceae family were decreased. Our results suggest that G&C affect the composition of the gut microbiome which may have implications for therapeutic efficacy.

Colonic mucosal and exfoliome transcriptomic profiling and fecal microbiome response to a flaxseed lignan extract intervention in humans

BACKGROUND

Microbial metabolism of lignans from high-fiber plant foods produces bioactive enterolignans, such as enterolactone (ENL) and enterodiol (END). Enterolignan exposure influences cellular pathways important to cancer risk and is associated with reduced colon tumorigenesis in animal models and lower colorectal cancer risk in humans.

OBJECTIVES

The aim of this study was to test the effects of a flaxseed lignan supplement (50 mg secoisolariciresinol diglucoside/d) compared with placebo on host gene expression in colon biopsies and exfoliated colonocyte RNA in feces and fecal microbial community composition, and to compare responses in relation to ENL excretion.

METHODS

We conducted a 2-period randomized, crossover intervention in 42 healthy men and women (20-45 y). We used RNA-seq to measure differentially expressed (DE) genes in colonic mucosa and fecal exfoliated cells through the use of edgeR and functional analysis with Ingenuity Pathway Analysis. We used 16S ribosomal RNA gene (V1-V3) analysis to characterize the fecal microbiome, and measured END and ENL in 24-h urine samples by gas chromatography-mass spectrometry.

RESULTS

We detected 32 DE genes (false discovery rate <0.05) in the exfoliome, but none in the mucosal biopsies, in response to 60 d of lignan supplement compared with placebo. Statistically significant associations were detected between ENL excretion and fecal microbiome measured at baseline and at the end of the intervention periods. Further, we detected DE genes in colonic mucosa and exfoliome between low- and high-ENL excreters. Analysis of biopsy samples indicated that several anti-inflammatory upstream regulators, including transforming growth factor β and interleukin 10 receptor, were suppressed in low-ENL excreters. Complementary analyses in exfoliated cells also suggested that low-ENL excreters may be predisposed to proinflammatory cellular events due to upregulation of nuclear transcription factor κB and NOS2, and an inhibition of the peroxisome proliferator-activated receptor γ network.

CONCLUSIONS

These results suggest that ENL or other activities of the associated gut microbial consortia may modulate response to a dietary lignan intervention. This has important implications for dietary recommendations and chemoprevention strategies. This study was registered at clinicaltrials.gov as NCT01619020.

HIV disease progression among women following seroconversion during a tenofovir-based HIV prevention trial

Background

Little is known regarding HIV disease outcomes among individuals who become infected with HIV while receiving antiretroviral medications for prevention. We compared HIV disease parameters among women who seroconverted while receiving tenofovir-containing oral or vaginal pre-exposure prophylaxis (PrEP) to placebo.

Methods

Participants with HIV seroconversion in a randomized placebo-controlled trial of oral tenofovir, oral tenofovir/emtricitabine, and vaginal tenofovir gel (MTN-003) were followed in a longitudinal cohort study (MTN-015). The effect of oral and vaginal tenofovir-containing PrEP on HIV disease progression was compared to placebo using linear mixed effects and Cox proportional hazard models, as appropriate. Additional analyses were performed to compare the outcomes among participants with detectable tenofovir or emtricitabine in plasma at the first quarterly visit in MTN-003.

Results

A total of 224 participants were included in the analysis; 93% from South Africa and 94% clade C virus. No differences in HIV RNA at steady state or the trajectory over 12 months were observed for each active arm compared to placebo; tenofovir gel recipients had higher CD4⁺ T cell counts (722 vs 596 cells/mm³; p = 0.02) at 90 days after estimated HIV seroconversion and higher average rates of change over 12 months compared to placebo (-181 vs -92 cells/mm³ per year; p = 0.08). With a median follow-up of 31 months, no significant differences were observed for time to CD4⁺ T cell count ≤350 cells/mm³, or the composite endpoint of CD4⁺ T cells ≤350 cells/mm³, initiation of antiretroviral therapy or death for each active arm compared to placebo. Additionally, there were no significant differences in the HIV RNA or CD4+ T cell counts at baseline, the change to month 12, or any disease progression outcomes among participants with oral drug detected and no oral drug detected compared to placebo.

Conclusions

No clinically significant differences in HIV seroconversion outcomes were observed among women randomized to tenofovir-containing oral or vaginal PrEP regimens, however low overall adherence limits the generalizability of these findings.

Exploratory plasma proteomic analysis in a randomized crossover trial of aspirin among healthy men and women

Long-term use of aspirin is associated with lower risk of colorectal cancer and other cancers; however, the mechanism of chemopreventive effect of aspirin is not fully understood. Animal studies suggest that COX-2, NFκB signaling and Wnt/β-catenin pathways may play a role, but no clinical trials have systematically evaluated the biological response to aspirin in healthy humans. Using a high-density antibody array, we assessed the difference in plasma protein levels after 60 days of regular dose aspirin (325 mg/day) compared to placebo in a randomized double-blinded crossover trial of 44 healthy non-smoking men and women, aged 21-45 years. The plasma proteome was analyzed on an antibody microarray with ~3,300 full-length antibodies, printed in triplicate. Moderated paired t-tests were performed on individual antibodies, and gene-set analyses were performed based on KEGG and GO pathways. Among the 3,000 antibodies analyzed, statistically significant differences in plasma protein levels were observed for nine antibodies after adjusting for false discoveries (FDR adjusted p-value<0.1). The most significant protein was succinate dehydrogenase subunit C (SDHC), a key enzyme complex of the mitochondrial tricarboxylic acid (TCA) cycle. The other statistically significant proteins (NR2F1, MSI1, MYH1, FOXO1, KHDRBS3, NFKBIE, LYZ and IKZF1) are involved in multiple pathways, including DNA base-pair repair, inflammation and oncogenic pathways. None of the 258 KEGG and 1,139 GO pathways was found to be statistically significant after FDR adjustment. This study suggests several chemopreventive mechanisms of aspirin in humans, which have previously been reported to play a role in anti- or pro-carcinogenesis in cell systems; however, larger, confirmatory studies are needed.

Comprehensive site-specific whole genome profiling of stromal and epithelial colonic gene signatures in human sigmoid colon and rectal tissue

The strength of associations between various exposures (e.g., diet, tobacco, chemopreventive agents) and colorectal cancer risk may partially depend on the complex interaction between epithelium and stroma across anatomic subsites. Currently, baseline data describing genome-wide coding and long noncoding gene expression profiles in the healthy colon specific to tissue type and location are lacking. Therefore, colonic mucosal biopsies from 10 healthy participants who were enrolled in a clinical study to evaluate effects of lignan supplementation on gut resiliency were used to characterize the site-specific global gene expression signatures associated with stromal vs. epithelial cells in the sigmoid colon and rectum. Using RNA-seq, we demonstrate that tissue type and location patterns of gene expression and upstream regulatory pathways are distinct. For example, consistent with a key role of stroma in the crypt niche, mRNAs associated with immunoregulatory and inflammatory processes (i.e., CXCL14, ANTXR1), smooth muscle contraction (CALD1), proliferation and apoptosis (GLP2R, IGFBP3), and modulation of extracellular matrix (MMP2, COL3A1, MFAP4) were all highly expressed in the stroma. In comparison, HOX genes (HOXA3, HOXD9, HOXD10, HOXD11, and HOXD-AS2, a HOXD cluster antisense RNA 2), and WNT5B expression were also significantly higher in sigmoid colon compared with the rectum. These findings provide strong impetus for considering colorectal tissue subtypes and location in future observational studies and clinical trials designed to evaluate the effects of exposures on colonic health.

Long-term follow-up of HIV seroconverters in microbicide trials - rationale, study design, and challenges in MTN-015

BACKGROUND

As the effect of biomedical prevention interventions on the natural history of HIV-1 infection in participants who seroconvert is unknown, the Microbicide Trials Network (MTN) established a longitudinal study (MTN-015) to monitor virologic, immunological, and clinical outcomes, as well as behavioral changes among women who become HIV-infected during MTN trials. We describe the rationale, study design, implementation, and enrollment of the initial group of participants in the MTN seroconverter cohort.

METHODS

Initiated in 2008, MTN-015 is an ongoing observational cohort study enrolling participants who acquire HIV-1 infection during effectiveness studies of candidate microbicides. Eligible participants from recently completed and ongoing MTN trials are enrolled after seroconversion and return for regular follow-up visits with clinical and behavioral data collection. Biologic samples including blood and genital fluids are stored for future testing.

RESULTS

MTN-015 was implemented initially at six African sites and enrolled 100/139 (72%) of eligible women who seroconverted in HIV Prevention Trials Network protocol 035 (HPTN 035, conducted by the MTN). The median time from seroconversion in HPTN 035 to enrollment in MTN-015 was 18 months. Retention was good with >70% of visits completed. Implementation challenges included regulatory reviews, translation, and testing of questionnaires, and site readiness.

CONCLUSIONS

Enrollment of HIV-seroconverters into a longitudinal observational follow-up study is feasible and acceptable to participants. Data and samples collected in this protocol will be used to assess safety of investigational HIV microbicides and answer other important public health questions for HIV infected women.

Abstract 4284: Exploratory plasma proteomic analysis in a randomized cross-over trial of aspirin among healthy individuals

Background: Long-term use of aspirin is associated with lower colorectal cancer (CRC) incidence; however, the mechanism of the chemopreventive effect of aspirin is not fully understood. Animal studies suggest that COX-2, NFκB signaling and Wnt/β-catenin pathways may play a role, but no clinical trials have systematically evaluated the biological response to aspirin in healthy humans. Methods: We assessed the difference in plasma protein levels after 60 days of regular dose aspirin (325 mg/day) compared to placebo in a randomized, double-blinded, placebo-controlled, cross-over trial of 44 healthy non-smoking men and women, aged 21-45 years. Plasma proteomics was analyzed on an antibody microarray with ∼3,000 full-length antibodies, printed in triplicate. Moderated paired t-test was performed on individual antibodies, and gene set analyses were performed for KEGG and GO pathways. Results: Among the 3,387 antibodies, significant differences in plasma protein levels were observed for 267 antibodies (p&lt;0.05), the most significant protein being a transcription-factor regulator belonging to a steroid receptor family and found to be differentially expressed in colon cancer cells. Other significant proteins are involved in multiple oncogenic pathways related to colon tumorigenesis. In the pathway analysis, 4 KEGG (among 138) and 69 GO (among 1,089) pathways were found to be significant (p&lt;0.05), including natural killer (NK) cell-mediated cytotoxicity, butanoate metabolism and Wnt signaling pathways. Pathways that modulate cellular protein binding to steroid receptors were also significantly different between aspirin treatment and placebo (p&lt;0.05). None of the results remained statistically significant after correction for multiple testing. Conclusion: Several proteins and pathways, which have previously been reported as playing a role in colorectal carcinogenesis in vitro were found to be differentially expressed after aspirin treatment vs. placebo in healthy human subjects. This study suggests several chemopreventive mechanisms of aspirin; however, larger, confirmatory studies are needed.

Citation Format: Xiaoliang Wang, Yuzheng Zhang, Ali Shojaie, Paul D. Lampe, Lisa Levy, Ulrike Peters, John D. Potter, Emily White, Johanna W. Lampe. Exploratory plasma proteomic analysis in a randomized cross-over trial of aspirin among healthy individuals. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4284.

Abstract A68: Does genetic ancestry influence the metabolic response to a traditional Mexican versus U.S. diet? A randomized crossover feeding trial among first and second generation women of Mexican descent

Background: Greater acculturation to the U.S. dietary habits has been suggested to contribute to the high rates of obesity, insulin resistance, and therefore, potential risk of type 2 diabetes (T2D) and breast cancer. Mexican immigrants may be evolutionary adapted to traditional diets high in legumes and complex carbohydrates. When consuming an inexpensive, readily available U.S. diet high in refined carbohydrates and added sugars they may experience a detrimental metabolic and/or inflammatory response, placing them at a disproportionately higher risk of certain cancers. To better understand these biological mechanisms that may underlie immigrant-related health disparities, we tested whether genetic ancestry modified the metabolic response to a traditional Mexican versus U.S. diet in a controlled feeding trial.

Methods: First and second generation, female, Mexican immigrants (n=53) completed a randomized, crossover feeding trial testing the response to a Mexican versus U.S. diet for 24 days each, separated by a 28-day washout period. The trial diets were designed to provide energy content for weight maintenance and were similar in macronutrient composition. Participants were instructed to consume only study provided foods. The traditional Mexican diet was high in corn tortillas, beans, Mexican soups, fruits, vegetables, animal fats, full-fat milk, and Mexican cheeses; in contrast, the U.S. diet was high in refined carbohydrates, vegetable oils, nonfat or low-fat milk, processed foods, processed meats and sugar-sweetened beverages. The metabolic response to the diets was measured by fasting serum concentrations of glucose, insulin, insulin-like growth factor (IGF)-1, IGF binding protein (IGFBP)-3, adiponectin, C-reactive protein (CRP), interleukin-6 (IL-6), and the calculated homeostasis model assessment of insulin resistance (HOMA-IR) at the beginning and end of each feeding period. DNA was extracted from baseline blood for genotyping and estimation of each participant's proportion of genetic ancestry from four populations – Indigenous American (IA), European, African, and Asian – with the use of 218 Informative Ancestry Markers. Linear mixed models were adjusted for diet sequence, feeding period, baseline and washout biomarker concentrations, age, body weight, and acculturation.

Results: The overall genetic ancestral background of the study sample was 53% IA and 36% European ancestry. In general, genetic ancestry did not modify the metabolic responses to the Mexican versus U.S. diet. However, genetic ancestry was associated with some baseline participant's characteristics and measures. Greater IA ancestry trended toward a positive association with waist-to-hip ratio (P=0.08) and was inversely associated with both education and acculturation (P&lt;0.05). Further, greater IA ancestry was positively associated with baseline fasting serum concentrations of glucose, CRP, IL-6, and calculated HOMA-IR (P&lt;0.05), and was inversely associated with circulating concentrations of IGF-1 and IGFBP-3 (P&lt;0.05).

Conclusions: Genetic ancestry suggested differences in baseline measures of several biomarkers that have been identified as cancer susceptibility biomarkers. Although, we found a significant metabolic response to the traditional Mexican versus U.S. diet, overall, we did not observe correlations between genetic ancestry and this response. Nonetheless, the results from the study may inform our understanding of variation in cancer susceptibility biomarkers in vulnerable populations. Additional research is needed to further investigate whether genetic ancestry modifies the associations of other lifestyle exposures, such as physical activity or smoking, with cancer susceptibility biomarkers in Mexican immigrants and other minority groups.

Citation Format: Margarita Santiago-Torres, Jean De Dieu Tapsoba, Mario Kratz, Johanna W. Lampe, Kara L. Breymeyer, Lisa Levy, Xiaoling Song, Adriana Villaseñor, Ching-Yun Wang, Christopher Carlson, Marian L. Neuhouser. Does genetic ancestry influence the metabolic response to a traditional Mexican versus U.S. diet? A randomized crossover feeding trial among first and second generation women of Mexican descent. [abstract]. In: Proceedings of the Eighth AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 13-16, 2015; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2016;25(3 Suppl):Abstract nr A68.