No abstract

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.

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.

Abstract. 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 ≤ 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.

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.

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

The placenta is a readily available and ethically non-controversial source of large amounts of therapeutic stem cells. We isolated adherent cells from the Umbilical Cord (UC) and the Amnion Chorion (AC) of term placentas. These Placenta Derived Adherent Cells (PDACs) displayed a cell surface phenotype of CD29+, CD44+, CD73+, CD90+, CD105+, CD200+, CD34−, and constitutively secreted IL-6, IL-8 and Monocyte Chemoattractant protein-1 (MCP-1). PDACs demonstrated in vitro pluripotency and suppressed T cell proliferation in both the allogeneic mixed leukocyte reaction, and the autologous EBV regression assay. Because progenitor cells have been described to inhibit tumor growth in some systems, the role of PDACs in tumor suppression was investigated. EBV transformed tumor cells were cultured either alone, or with AC or UC PDACs. After 6 days, live (7-AAD− Annexin-V−) tumor cells were counted on a flow cytometer. Free growing tumor cells numbered 40,000. When tumor cells were co-cultured with AC or UC PDACs, the growth was suppressed to 10,000 cells, a suppression of 75%. We designed and tested a panel of tumor cell lines that included retinoblastoma (RB), histiocytic lymphoma (HL), chronic myelogenous leukemia (CML), and colon adenocarcinoma (CAC). The tissue origin of the selected tumor cell lines included neuronal tissue (retinoblastoma), epithelium (carcinomas) and the hematopoietic lineage (lymphomas and CML). Co-culture experiments showed that the growth of all tumor lines was suppressed more than 40%. When a transwell was introduced separating PDACs and tumor cells, contact dependency of suppression was 12% for HL, 22% for CML, 42% for CAC, and 51% for EBV transformed tumor cells. These results indicate that PDACs may have therapeutic value with respect to certain cancers.

The placenta is a readily available and ethically non-controversial source of large amounts of therapeutic stem cells. Placenta Derived Adherent Cells (PDACs) are isolated from the placenta by one of several methods including physical disruption of tissue from several different anatomical sites within the placenta that include the amniotic membrane, chorion, placental cotyledons, or any combination thereof. Flow cytometry analysis showed that PDACs isolated from certain sites exhibit defined phenotypes, including for example CD200+ CD105+ CD73+ CD34− CD45− at percentages ≥70% and constitutively secrete IL-6, IL-8, and Monocyte Chemoattractant Protein-1 (MCP-1). PDACs demonstrate in vitro pluripotency in the adipogenic, osteogenic, and chondrogenic lineages. Furthermore, PDACs suppress T cell proliferation in certain Mixed Leukocyte Reaction (MLR) and the autologous EBV regression assays. Because secreted factors can powerfully modify immune responses and influence therapeutic use of cells, we report on the cytokine secretion in certain PDAC MLR and regression assays. Cytokines were measured on a Luminex system in supernatants from 6-day PDAC cultures, PDAC MLRs or PDAC regression assays. MLRs include PDACs, Dendritic Cells (DC)s, and T cells at DC/PDAC/T ratios 1/2/10. EBV regression assays included PDACs, EBV antigen-presenting cells (APC), and T cells at APC/PDAC/T ratios 1/2/10. Levels of IL-6 (11 ng/ml) and IL-8 (16 ng/ml) stayed constant in PDAC solo cultures, PDAC MLRs, and PDAC regression assays. MCP-1 concentration was 2 ng/ml in PDAC solo cultures, and non-suppressive control adherent cell MLRs and regression assays, but increased to 10 ng/ml in suppressed PDAC MLRs and PDAC regression assays. These values are consistent with reported MCP-1 serum levels. Interleukin-2 (IL-2) is both a T cell survival factor and an obligate factor for CD4+CD25+ T regulatory cells. T regulatory cells are not required for PDAC T cell suppression, but IL-2 levels consistently increase when MLR suppression by PDACs occurs. The CD4 MLR supernatants contained 65 pg/ml IL-2, and the CD8 MLR contained 35 pg/ml IL-2. In the 85% and 75% suppressed CD4 and CD8 PDAC MLRs, the IL-2 levels rose 5-fold to 331 pg/ml (CD4) and 2-fold to 67 pg/ml(CD8). These results indicate that IL-2 and MCP-1, traditionally known as stimulators of the immune response, may play a role in PDAC immune suppression. PDACs, which cause the secretion, may thus be useful therapeutic tools in the clinic.