Viewing Native American Cervical Cancer Disparities through the Lens of the Vaginal Microbiome: A Pilot Study

Abstract

Vaginal dysbiosis is implicated in persistent human papillomavirus (HPV) infection and cervical cancer. Yet, there is a paucity of data on the vaginal microbiome in Native American communities. Here, we aimed to elucidate the relationships between microbiome, HPV, sociodemographic, and behavioral risk factors to better understand an increased cervical cancer risk in Native American women. In this pilot study, we recruited 31 participants (16 Native American and 15 non-Native women) in Northern Arizona and examined vaginal microbiota composition, HPV status, and immune mediators. We also assessed individuals' sociodemographic information and physical, mental, sexual, and reproductive health. Overall, microbiota profiles were dominated by common Lactobacillus species (associated with vaginal health) or a mixture of bacterial vaginosis-associated bacteria. Only 44% of Native women exhibited Lactobacillus dominance, compared with 58% of non-Native women. Women with vaginal dysbiosis also had elevated vaginal pH and were more frequently infected with high-risk HPV. Furthermore, we observed associations of multiple people in a household, lower level of education, and high parity with vaginal dysbiosis and abundance of specific bacterial species. Finally, women with dysbiotic microbiota presented with elevated vaginal levels of proinflammatory cytokines. Altogether, these findings indicate an interplay between HPV, vaginal microbiota, and host defense, which may play a role in the cervical cancer disparity among Native American women. Future longitudinal studies are needed to determine the mechanistic role of vaginal microbiota in HPV persistence in the context of social determinants of health toward the long-term goal of reducing health disparities between non-Hispanic White and Native American populations. Prevention Relevance: Cervical cancer disproportionally affects Native American women. Sociodemographic and behavioral factors might contribute to this disparity via alteration of vaginal microbiota. Here, we show the association between these factors and vaginal dysbiosis and immune activation, which can be implicated in high-risk HPV infection among Native American and other racial/ethnic populations.

Figure 1.

Vaginal microbiota composition of Native American women in our study. Bar plots show the relative abundance of taxa assigned to the A, genus or B, species level grouped based on race. Vaginal microbiota profiles were similar between Native American and non-Native American women from Northern Arizona. The most prevalent Lactobacillus species included Lactobacillus crispatus and Lactobacillus iners. Dysbiotic Lactobacillus-depleted profiles consisted of typical communities of anaerobic bacteria associated with bacterial vaginosis (BV), including Gardnerella vaginalis [assigned as Bifidobacterium vaginale in the Genome Taxonomy Database (GTDB)], Fannyhessea vaginae (formerly known as Atopobium vaginae), Sneathia vaginalis (formerly known as Sneathia amnii), Prevotella timonensis, Megasphaera lornae (assigned as 28L sp00017755 in GTDB), and Clostridiales genomosp. BVAB1 (assigned as UBA629 sp005465875 in GTDB).

Figure 2.

Associations of Lactobacillus dominance with race, vaginal pH, HPV status, and socioeconomic and lifestyle factors. Stacked bar plots show the number of participants with Lactobacillus-dominant microbiota or dysbiotic Lactobacillus-depleted microbiota among the groups based on A, race, B, vaginal pH, C, HPV status, D, age, E, BMI, F, size of household, G, education level, H, number of pregnancies, and I, marital status. P values were calculated using Fisher’s exact test. Vaginal microbiota profiles were dominated by Lactobacillus species in 44% of Native American women, which was similar to levels observed in non-Native American participants (58%). Lactobacillus dominance was highly associated with low vaginal pH (≤4.5). HPV-positive women also tended to have lower Lactobacillus abundance compared with HPV-negative women. Vaginal microbiota profiles were also more frequently dominated by Lactobacillus species in participants with BMI < 25, living in smaller households (1–3 people), having a college (bachelor’s, master’s, and doctorate) or associate/technical degree, who were nulliparous, married or living with a partner. No difference was observed between the younger and older participants (dichotomized based on the median age).

Figure 3.

Microbial features associated with sociodemographic factors, vaginal pH, and HPV status. Differentially abundant taxa between the groups based on A, race, B, vaginal pH, C, HPV status, D, BMI, E, education level, and F, household size were identified at the species level using ANCOM-BC. P values were corrected for multiple comparisons using the FDR method; taxa with q < 0.05 are depicted. Red and blue dots indicate taxa with LFC > 1 and LFC < −1, respectively. Numerous dysbiotic vaginal species are enriched in participants with abnormal vaginal pH, lower education level, who live in larger households, identify themselves as Native American, have higher BMI, and are hrHPV-positive, whereas Lactobacillus and Limosilactobacillus species were enriched in women with normal pH, higher education level and lower BMI.

Figure 4.

Vaginal profiles of cytokines, chemokines, and growth factors. A, heatmap reflects relative levels of proteins in vaginal swab samples. Unsupervised hierarchical clustering was used to assess the similarity between protein profiles. Two main clusters based on Euclidean distance and Ward linkage were observed. B, Stacked bar plots show the distribution of patients with normal and abnormal pH or C,Lactobacillus-dominant and dysbiotic Lactobacillus-depleted microbiota between the clusters. P values were calculated using the Fisher exact test. Unsupervised hierarchical clustering analysis indicates that immune marker levels associate with vaginal pH and Lactobacillus dominance.

Figure 5.

Vaginal levels of immune markers in the context of Lactobacillus dominance. Scatter plots show the concentration of A, cytokines, B, chemokines, and C, growth factors in vaginal swab samples in women with Lactobacillus-dominant or dysbiotic Lactobacillus-depleted microbiota. P values were calculated using two sample independent t tests (*, P < 0.05; **, P < 0.01). Women with dysbiotic Lactobacillus-depleted microbiota exhibited increased vaginal levels of IL1β, IL12 (p40), IL12 (p70), IL15, TNFɑ, and FGF2, when compared with women with Lactobacillus-dominant microbiota. In addition, GM-CSF and PDGF-AB/BB were significantly decreased in women with dysbiosis.