Browsing by Author "Tonui, Philip"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Association of Plasma Aflatoxin With Persistent Detection of Oncogenic Human Papillomaviruses in Cervical Samples From Kenyan Women Enrolled in a Longitudinal Study
    (BMC, 2023-06-06) Tong, Yan; Tonui, Philip; Orang’o, Omenge; Zhang, Jianjun; Maina, Titus; Muthoka, Kapten; Groopman, John; Smith, Joshua; Madeen, Erin; Ermel, Aaron; Loehrer, Patrick; Brown, Darron R.; Biostatistics, School of Public Health
    Background: Cervical cancer is caused by oncogenic human papillomaviruses (HR-HPV) and is common among Kenyan women. Identification of factors that increase HR-HPV persistence is critically important. Kenyan women exposed to aflatoxin have an increased risk of HR-HPV detection in cervical specimens. This analysis was performed to examine associations between aflatoxin and HR-HPV persistence. Methods: Kenyan women were enrolled in a prospective study. The analytical cohort for this analysis included 67 HIV-uninfected women (mean age 34 years) who completed at least two of three annual study visits and had an available blood sample. Plasma aflatoxin was detected using ultra-high pressure liquid chromatography (UHPLC)-isotope dilution mass spectrometry. Annual cervical swabs were tested for HPV (Roche Linear Array). Ordinal logistic regression models were fitted to examine associations of aflatoxin and HPV persistence. Results: Aflatoxin was detected in 59.7% of women and was associated with higher risk of persistent detection of any HPV type (OR = 3.03, 95%CI = 1.08-8.55, P = 0.036), HR-HPV types (OR = 3.63, 95%CI = 1.30-10.13, P = 0.014), and HR-HPV types not included in the 9-valent HPV vaccine (OR = 4.46, 95%CI = 1.13-17.58, P = 0.032). Conclusions: Aflatoxin detection was associated with increased risk of HR-HPV persistence in Kenyan women. Further studies, including mechanistic studies are needed to determine if aflatoxin synergistically interacts with HR-HPV to increase cervical cancer risk.
  • Thumbnail Image
    Item
    A community-based approach to cervical cancer prevention in western Kenya: An AMPATH feasibility project
    (Sage, 2022-05-23) Orang’o, Omenge; Tonui, Philip; Muthoka, Kapten; Kiptoo, Stephen; Maina, Titus; Agosa, Mercy; Ermel, Aaron; Tong, Yan; Brown, Darron; Medicine, School of Medicine
    Objectives: Centralized programs have been ineffective in reducing the burden of cervical cancer among Kenyan women. A community-based pilot study was initiated to screen Kenyan women for cervical cancer and to vaccinate their children against human papillomavirus (HPV). Methods: Women were educated about cervical cancer prevention at community meetings. Women then provided self-collected vaginal swabs for oncogenic HPV testing using the Roche Cobas Assay. All women were then referred to the local clinic for Visual Inspection with Acetic Acid (VIA). Women were offered the quadrivalent HPV vaccine for their children if and when it became available for the study. Results: Women in western Kenya were invited to participate in community meetings. A total of 200 women were enrolled: 151 (75.5%) were HIV-uninfected and 49 (24.5%) were HIV-infected; the median age for all women was 42 years. High-risk (HR)-HPV types were detected in 49 of swabs from all 200 participants (24.5%) including 20.5% of HIV-uninfected women and 36.7% of HIV-infected women (P = .022). VIA was performed on 198 women: 192 had normal examinations and six had abnormal examinations. Five cervical biopsies revealed two cases of CIN 2 and one CIN 3. Although all mothers were willing to have their children (N = 432) vaccinated, the HPV vaccine could not be delivered to Kenya during the study period. Conclusions: Kenyan women were willing to attend community meetings to learn about prevention of cervical cancer, to provide self-collected vaginal swabs for HPV testing, to travel to the Webuye Clinic for VIA following the collection of swabs, and to have their children vaccinated against HPV. HR-HPV was prevalent, especially in HIV-infected women. As a result of this pilot study, this community-based strategy to prevent cervical cancer will be continued in western Kenya.
  • Thumbnail Image
    Item
    Detection and Concentration of Plasma Aflatoxin Is Associated With Detection of Oncogenic Human Papillomavirus in Kenyan Women
    (Oxford Academic, 2019-09-01) Zhang, Jianjun; Orang’o, Omenge; Tonui, Philip; Tong, Yan; Maina, Titus; Kiptoo, Stephen; Muthoka, Katpen; Groopman, John; Smith, Joshua; Madeen, Erin; Ermel, Aaron; Loehrer, Patrick; Brown, Darron R.; Department of Epidemiology, School of Public Health
    Abstract Background Cervical cancer is common in Kenyan women. Cofactors in addition to infection with oncogenic human papillomavirus (HPV) are likely to be important in causing cervical cancer, because only a small percentage of HPV-infected women will develop this malignancy. Kenyan women are exposed to dietary aflatoxin, a potent carcinogen and immunosuppressive agent, which may be such a cofactor. Methods Demographics, behavioral data, plasma, and cervical swabs were collected from 88 human immunodeficiency virus-uninfected Kenyan women without cervical dysplasia. Human papillomavirus detection was compared between women with or without plasma aflatoxin B1-lysine (AFB1-lys) and evaluated in relation to AFB1-lys concentration. Results Valid HPV testing results were available for 86 women (mean age 34.0 years); 49 women (57.0%) had AFB1-lys detected and 37 (43.0%) had none. The AFB1-lys detection was not associated with age, being married, having more than secondary school education, home ownership, living at a walking distance to healthcare ≥60 minutes, number of lifetime sex partners, or age of first sex. The AFB1-lys detection and plasma concentrations were associated with detection of oncogenic HPV types. Conclusions The AFB1-lys positivity and higher plasma AFB1-lys concentrations were associated with higher risk of oncogenic HPV detection in cervical samples from Kenya women. Further studies are needed to determine whether aflatoxin interacts with HPV in a synergistic manner to increase the risk of cervical cancer.
  • Thumbnail Image
    Item
    Persistence of oncogenic and non-oncogenic human papillomavirus is associated with human immunodeficiency virus infection in Kenyan women
    (SAGE, 2020-07-28) Tong, Yan; Tonui, Philip; Ermel, Aaron; Orang’o, Omenge; Wong, Nelson; Titus, Maina; Kiptoo, Stephen; Muthoka, Kapten; Loehrer, Patrick J; Brown, Darron R; Medicine, School of Medicine
    Objectives: Cervical cancer is caused by persistent infection with oncogenic, or “high-risk” types of human papillomaviruses, and is the most common malignancy in Kenyan women. A longitudinal study was initiated to investigate factors associated with persistent human papillomavirus detection among HIV-infected and HIV-uninfected Kenyan women without evidence of cervical dysplasia. Methods: Demographic/behavioral data and cervical swabs were collected from HIV-uninfected women (n = 82) and HIV-infected women (n = 101) at enrollment and annually for 2 years. Human papillomavirus typing was performed on swabs (Roche Linear Array). Logistic regression models of human papillomavirus persistence were adjusted for demographic and behavioral characteristics. Results: HIV-infected women were older and less likely to be married and to own a home and had more lifetime sexual partners than HIV-uninfected women. All HIV-infected women were receiving anti-retroviral therapy at enrollment and had satisfactory CD4 cell counts and HIV viral loads. One- and two-year persistent human papillomavirus detection was significantly associated with HIV infection for any human papillomavirus, high-risk human papillomavirus, International Agency for the Research on Cancer-classified high-risk human papillomavirus, and non-oncogenic “low-risk” human papillomavirus. Conclusion: Persistent detection of oncogenic and non-oncogenic human papillomavirus was strongly associated with HIV infection in Kenyan women with re-constituted immune systems based on satisfactory CD4 cell counts. In addition to HIV infection, factors associated with an increased risk of human papillomavirus persistence included a higher number of lifetime sex partners. Factors associated with decreased risk of human papillomavirus persistence included older age and being married. Further studies are needed to identify the immunological defects in HIV-infected women that allow human papillomavirus persistence, even in women receiving effective anti-retroviral therapy. Further studies are also needed to determine the significance of low-risk human papillomavirus persistence in HIV-infected women.