University of Nairobi

About: University of Nairobi is a education organization based out in Nairobi, Nairobi, Kenya. It is known for research contribution in the topics: Population & Health care. The organization has 6702 authors who have published 10777 publications receiving 231294 citations. The organization is also known as: UoN & IAU-020319.

Characterization of a Human Cervical CD4+ T Cell Subset Coexpressing Multiple Markers of HIV Susceptibility

Abstract: The HIV pandemic disproportionately affects women, with most infections acquired through receptive vaginal sex. Although the target cells by which HIV establishes infection in the female genital tract remain poorly defined, it is known that immune activation results in CD4(+) T cells with enhanced susceptibility, as does expression of the mucosal integrin α4β7 and the HIV coreceptor CCR5. Blood and cervical cytobrush specimens were collected from female sex workers (FSWs) in Nairobi, Kenya. Genital infection diagnostics were performed, T cell populations were defined by multiparameter flow cytometry based on their expression of surface receptors relevant to mucosal homing and/or HIV acquisition, and cytokine production was assayed by intracellular cytokine staining. The integrin α4β7 was expressed on 26.0% of cervical CD4(+) T cells, and these cells were more likely to express both the HIV coreceptor CCR5 (p < 0.0001) and the early activation marker CD69 (p < 0.0001) but not CXCR4 (p = 0.34). Cervical Th17 frequencies were enhanced compared with blood (7.02 versus 1.24%; p < 0.0001), and cervical IL-17A(+) CD4(+) T cells preferentially coexpressed α4β7 and CCR5. Expression of IFN-γ and IL-22 was greater in cervical Th17 cells than in blood Th17 cells. In keeping with the hypothesis that these cells are preferential HIV targets, gp120 preferentially bound CCR5(+) cervical T cells, and cervical Th17 cells were almost completely depleted in HIV(+) FSWs compared with HIV(-) FSWs. In summary, a subset of Th17 CD4(+) T cells in the cervical mucosa coexpresses multiple HIV susceptibility markers; their dramatic depletion after HIV infection suggests that these may serve as key target cells during HIV transmission.

Genital shedding of human immunodeficiency virus type 1 DNA during pregnancy: association with immunosuppression, abnormal cervical or vaginal discharge, and severe vitamin A deficiency.

Abstract: More than 2 million children worldwide are infected with human immunodeficiency virus type 1 (HIV-1), the majority of whom acquired the infection from their mothers [1]. Mother-to-child transmission of HIV-1 occurs in utero, intrapartum, and postnatally (through breast-feeding), with transmission rates ranging from 14% to 39% [2]. Several observations, including the differential infection rate of vaginally delivered twins, the protective effect of cesarean delivery on vertical transmission, and the association of prolonged ruptured membranes with vertical transmission, suggest that infant exposure to HIV-1 in the maternal genital tract during delivery is an important determinant of transmission [2]. The association between vertical transmission of HIV-1 and advanced maternal disease, immunosuppression, and plasma viremia or antigenemia, and the inverse association with antiretroviral therapy suggest that systemic maternal virus burden is an important factor in HIV-1 transmission [2–8]. Markers of systemic virus burden, however, may not necessarily reflect local virus burden, and the effect of genital HIV-1 shedding on vertical transmission may be distinct from the effect of plasma viremia on transmission. HIV-1 has been cultured from cell-free and cellular fractions of vaginal and endocervical secretions of HIV-1–seropositive women [9, 10]. HIV-1–infected cells are detectable in female genital tract secretions by polymerase chain reaction (PCR) amplification. The prevalence of HIV-1 DNA in cervical secretions was 33% and 37% in two previously published studies from Nairobi and 17% in vaginal specimens in one of these studies [11, 12]. Correlates of HIV-1 DNA detection in the cervix have included oral contraceptives, cervical mucopus, ectopy, and cervical inflammation [11, 12]. In addition, two studies have shown an increased prevalence of HIV-1 DNA in the cervix of pregnant women, but these studies together included only 29 pregnant women at various stages of gestation [12, 13]. While detection of HIV-1 in semen has been inversely associated with CD4 cell count and zidovudine use, little is known about these factors in female genital tract shedding of HIV-1 [14, 15]. Moreover, correlates of genital shedding of HIV-1 in pregnancy have not been described. To characterize the prevalence and correlates of HIV-1 detection in cervical and vaginal specimens from pregnant women, we evaluated HIV-1–seropositive women participating in a breast-feeding transmission study in Nairobi. Little is known about factors that predispose to virus localization within a host. We previously evaluated prevalence and correlates of HIV-1 pro virus in breast milk of women participating in this cohort [16]. To evaluate provirus shedding at different epithelial sites, we determined the relationship between HIV-1 shedding in the cervix and vagina and in breast milk.

Scale and diversity of the physical technosphere: A geological perspective:

Abstract: We assess the scale and extent of the physical technosphere, defined here as the summed material output of the contemporary human enterprise. It includes active urban, agricultural and marine components, used to sustain energy and material flow for current human life, and a growing residue layer, currently only in small part recycled back into the active component. Preliminary estimates suggest a technosphere mass of approximately 30 trillion tonnes (Tt), which helps support a human biomass that, despite recent growth, is ~5 orders of magnitude smaller. The physical technosphere includes a large, rapidly growing diversity of complex objects that are potential trace fossils or ‘technofossils’. If assessed on palaeontological criteria, technofossil diversity already exceeds known estimates of biological diversity as measured by richness, far exceeds recognized fossil diversity, and may exceed total biological diversity through Earth’s history. The rapid transformation of much of Earth’s surface mass into th...

State of the Climate in 2013

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