The importance of caregivers in the outcome of pediatric HIV management, Mombasa, Kenya.

We assessed programmatic gaps that prevent the optimal treatment of pediatric HIV infection despite free antiretroviral care in Kenya. Of 626 HIV-infected Kenyan children, the median age was five years, 54% were male and the mortality rate was 3.2 per 100 person-years. A total of 380 (61%) children initiated antiretroviral therapy (ART) during the study period. Among the 246 children who never started ART, 129 (52%) met the criteria for ART initiation. Immunologic failure occurred in 20% of children who received ART for >24 weeks. In multivariate analysis, immunological failure was associated with having nonimmediate relative or unrelated caregivers accompanying the child to clinic (AOR = 69.16, p = 0.008). Having ≥ 3 types of accompanying caregivers was also associated with virologic failure in multivariate analysis (AOR = 3.84, p = 0.03). The lost to follow-up rate was 8.7/100 persons-years for the entire cohort, and significantly higher (17.7/100 persons-years) among children not on ART (p < 0.001). Among children who do initiate ART, those with the best treatment outcomes were those who had a limited number of close relatives as caregivers and good adherence to ART. Focus on early ART initiation and education of the right caregiver will likely improve retention and quality of pediatric HIV care in Kenya.

Novel application of a whole blood intracellular cytokine detection assay to quantitate specific T-cell frequency in field studies.

We optimized a whole blood intracellular cytokine assay to quantitate the frequency of specific CD4+ and CD8+ T cells in small volumes of whole blood from infants from developing countries. The assay is performed in two steps. First, whole blood is stimulated in the presence of specific antigens for 6-18 h, ending with cryopreservation of fixed white cells. These stimulation steps were specifically adapted to be practical and reliable in a rural, developing country field setting. Later, in a more resourceful setting, interferon-gamma producing CD4+ or CD8+ T cells are detected by flow cytometry. The assay proved sensitive and specific for detecting mycobacteria-specific immunity 10 weeks after Bacillus Calmette-Guerin (BCG) vaccination of newborns from a rural field site.

Early detection of HIV infection among Kenyan infants using a reverse transcriptase activity assay.

Two hundred HIV-exposed Kenyan infants were tested for HIV infection at birth and at age 6, 12, 24 and 48 weeks, by DNA polymerase chain reaction (PCR) and Cavidi reverse transcriptase (RT) assays and after age 18 months by HIV antibody test. Eleven (5.5%) infants became HIV infected. In 6 infants, positive RT preceded positive DNA PCR. The use of RT assay may facilitate earlier HIV diagnosis in infants.

Implementation of a validated peripheral neuropathy screening tool in patients receiving antiretroviral therapy in Mombasa, Kenya.

Limited objective data are available for the prevalence of peripheral neuropathy (PN) among antiretroviral (ART)-treated human immunodeficiency virus (HIV)-infected patients in resource-limited settings. A validated neuropathy-screening tool was integrated into routine ART visits at an HIV clinic in Mombasa, Kenya. Diagnosis of PN required at least one symptom and either abnormal vibratory sensation or deep tendon reflex bilaterally. Among 102 consecutively screened patients, 63% were women, 62% were receiving ART for < or = 1 year, and 86% were receiving a stavudine (D4T)-based regimen. Thirty-seven (36%) had PN. Univariate analysis showed that current D4T use was protective against PN (P = 0.03) and older age was a marginal risk factor (P = 0.05). Multivariate analysis showed that older age was a risk factor for neuropathy (P = 0.04). Peripheral neuropathy was common, particularly among older HIV-infected adults in Kenya. The protective association with current D4T use likely represents survivor effect bias. Longitudinal studies using this screen will help further characterize PN in resource-limited settings.

Mycobacterium leprae inhibits dendritic cell activation and maturation.

Leprosy presents with a clinical spectrum of skin lesions that span from strong Th1-mediated cellular immunity and control of bacillary growth at one pole to poor Ag-specific T cell immunity with extensive bacillary load and Th2 cytokine-expressing lesions at the other. To understand how the immune response to Mycobacterium leprae is regulated, human dendritic cells (DC), potent inducers of adaptive immune responses, exposed to M. leprae, Mycobacterium tuberculosis (Mtb), and Mycobacterium bovis bacillus Calmette-Guerin (BCG) were studied for their ability to be activated and to prime T cell proliferation. In contrast with Mtb and BCG, M. leprae did not induce DC activation/maturation as measured by the expression of selected surface markers and proinflammatory cytokine production. In MLR, T cells did not proliferate in response to M. leprae-stimulated DC. Interestingly, M. leprae-exposed MLR cells secreted increased Th2 cytokines as well as similar Th1 cytokine levels as compared with Mtb- and BCG-exposed cells. Gene expression analysis revealed a reduction in levels of mRNA of DC activation and maturation markers following exposure to M. leprae. Our data suggest that M. leprae does not induce and probably suppresses in vitro DC maturation/activation, whereas Mtb and BCG are stimulatory.

Mycobacterium tuberculosis inhibits maturation of human monocyte-derived dendritic cells in vitro.

To induce effector immunity, dendritic cells (DCs) must differentiate into fully mature cells. We show that, after human monocyte-derived DCs were infected with virulent Mycobacterium tuberculosis, up-regulation of cellular-surface maturation markers was minimal and reversible. In the presence of a potent stimulus for maturation (tumor necrosis factor [TNF]-alpha, interleukin [IL]-1beta, and prostaglandin E2 [PGE2]), M. tuberculosis inhibited phenotypic DC maturation. M. tuberculosis-infected DCs had an impaired ability to induce allogeneic lymphoproliferation and activated autologous memory CD4+ and CD8+ T cells optimally only in the presence of TNF-alpha, IL-1beta, and PGE2. Thus, virulent M. tuberculosis inhibits phenotypic and functional maturation of human monocyte-derived DCs. This mechanism, which has been described elsewhere for various viruses and for the virulent mycobacterium M. leprae, may be a novel mechanism that this pathogen uses to evade the host's immune response.