Compartmentalization of immune responses in human tuberculosis: few CD8+ effector T cells but elevated levels of FoxP3+ regulatory t cells in the granulomatous lesions.

Immune responses were assessed at the single-cell level in lymph nodes from children with tuberculous lymphadenitis. Tuberculosis infection was associated with tissue remodeling of lymph nodes as well as altered cellular composition. Granulomas were significantly enriched with CD68+ macrophages expressing the M. tuberculosis complex-specific protein antigen MPT64 and inducible nitric oxide synthase. There was a significant increase in CD8+ cytolytic T cells surrounding the granuloma; however, CD8+ T cells expressed low levels of the cytolytic and antimicrobial effector molecules perforin and granulysin in the granulomatous lesions. Quantitative real-time mRNA analysis revealed that interferon-gamma, tumor necrosis factor-alpha, and interleukin-17 were not up-regulated in infected lymph nodes, but there was a significant induction of both transforming growth factor-beta and interleukin-13. In addition, granulomas contained an increased number of CD4+FoxP3+ T cells co-expressing the immunoregulatory cytotoxic T-lymphocyte antigen-4 and glucocorticoid-induced tumor necrosis factor receptor molecules. Low numbers of CD8+ T cells in the lesions correlated with high levels of transforming growth factor-beta and FoxP3+ regulatory T cells, suggesting active immunosuppression at the local infection site. Compartmentalization and skewing of the immune response toward a regulatory phenotype may result in an uncoordinated effector T-cell response that reduces granule-mediated killing of M. tuberculosis-infected cells and subsequent disease control.

Extended-dose nevirapine to 6 weeks of age for infants to prevent HIV transmission via breastfeeding in Ethiopia, India, and Uganda: an analysis of three randomised controlled trials.

BACKGROUND: UNICEF/WHO recommends that infants born to HIV-infected mothers who do not have access to acceptable, feasible, affordable, sustainable, and safe replacement feeding should be exclusively breastfed for at least 6 months. The aim of three trials in Ethiopia, India, and Uganda was to assess whether daily nevirapine given to breastfed infants through 6 weeks of age can decrease HIV transmission via breastfeeding. METHODS: HIV-infected women breastfeeding their infants were eligible for participation. Participants were randomly assigned to receive either single-dose nevirapine (nevirapine 200 mg to women in labour and nevirapine 2 mg/kg to newborns after birth) or 6 week extended-dose nevirapine (nevirapine 200 mg to women in labour and nevirapine 2 mg/kg to newborn babies after birth plus nevirapine 5 mg daily from days 8-42 for the infant). The randomisation sequences were generated by computer at a central data coordinating centre. The primary endpoint was HIV infection at 6 months of age in infants who were HIV PCR negative at birth. Analyses were by modified intention to treat, excluding infants with missing specimens and those with indeterminate or confirmed HIV infection at birth. These studies are registered with ClinicalTrials.gov, numbers NCT00074399, NCT00061321, and NCT00639938. FINDINGS: 2024 liveborn infants randomised in the study had at least one specimen tested before 6 months of age (1047 infants in the single-dose group and 977 infants in the extended-dose group). The modified intention-to-treat population included 986 infants in the single-dose group and 901 in the extended-dose group. At 6 months, 87 children in the single-dose group and 62 in the extended-dose group were infected with HIV (relative risk 0.80, 95% CI 0.58-1.10; p=0.16). At 6 weeks of age, 54 children in the single-dose group and 25 in the extended-dose group were HIV positive (0.54, 0.34-0.85; p=0.009). 393 infants in the single-dose group and 346 in the extended-dose group experienced grade 3 or 4 serious adverse events during the study (p=0.54). INTERPRETATION: Although a 6-week regimen of daily nevirapine might be associated with a reduction in the risk of HIV transmission at 6 weeks of age, the lack of a significant reduction in the primary endpoint-risk of HIV transmission at 6 months-suggests that a longer course of daily infant nevirapine to prevent HIV transmission via breast milk might be more effective where access to affordable and safe replacement feeding is not yet available and where the risks of replacement feeding are high. FUNDING: US National Institutes of Health; US National Institute of Allergy and Infectious Diseases; Fogarty International Center.

Impact of human immunodeficiency virus 1 infection on clinical presentation, treatment outcome and survival in a cohort of Ethiopian children with tuberculosis.

BACKGROUND: Childhood tuberculosis (TB) is difficult to diagnose reliably because signs and symptoms are nonspecific and sputum for direct microscopy is difficult to obtain, especially in very young children. This diagnostic dilemma is thought to have increased with the HIV pandemic. Few studies on treatment outcome of dually infected children in high endemic countries have been reported. This study examines the impact of HIV infection on clinical presentation, diagnostic criteria and treatment outcome of TB in Ethiopian children. METHODS: A prospective cohort study of children with TB diagnosed in Addis Ababa from December 1995 to January 1997 in which HIV-positive children were compared with HIV-negative children with regard to medical history, signs and symptoms, nutritional status, chest radiography, tuberculin skin test, response to TB treatment and final outcome. Mycobacterium tuberculosis was cultured in children with pulmonary manifestations. RESULTS: HIV-positive children were younger, were underweight and had a 6-fold higher mortality than HIV-negative children. The tuberculin skin test was less sensitive and chest radiography was less specific in HIV-infected patients. Adherence to treatment was high (96%), and the cure rate was 58% for HIV-positive and 89% for HIV-negative TB patients. CONCLUSION: HIV-positive children are at risk of diagnostic error as well as delayed diagnosis of TB. TB manifestations are more severe and progression to death is more rapid than in HIV-negative children. Weight for age may be used to identify children at high risk of a fatal outcome.

Slower clearance of nevirapine resistant virus in infants failing extended nevirapine prophylaxis for prevention of mother-to-child HIV transmission.

Nevirapine resistance mutations arise commonly following single or extended-dose nevirapine (ED-NVP) prophylaxis to prevent mother-to-child transmission (PMTCT) of human immunodeficiency virus (HIV), but decay within 6-12 months of single-dose exposure. Use of ED-NVP prophylaxis in infants is expected to rise, but data on decay of nevirapine resistance mutations in infants in whom ED-NVP failed remain limited. We assessed, in Ethiopian infants participating in the Six-Week Extended Nevirapine (SWEN) Trial, the prevalence and persistence of nevirapine resistance mutations at 6 and 12 months following single-dose or up to 6 weeks of ED-NVP, and correlated their presence with the timing of infection and the type of resistance mutations. Standard population genotyping followed by high-throughput cloning were done on dried blood spot samples collected during the trial. More infants who received ED-NVP had nevirapine resistance detected by standard population genotyping (high frequencies) at age 6 months compared with those who received single-dose nevirapine (SD-NVP) (58% of 24 vs. 26% of 19, respectively; p = 0.06). Moreover, 56% of ED-NVP-exposed infants with nevirapine resistance at age 6 months still had nevirapine resistance mutations present at high frequencies at age 1 year. Infants infected before 6 weeks of age who received either SD- or ED-NVP were more likely to have Y181C or K103N; these mutations were also more likely to persist at high frequencies through 1 year of age. HIV-infected infants in whom ED-NVP prophylaxis fails are likely to experience delayed clearance of nevirapine-resistant virus in the first year of life, which in turn places them at risk for early selection of multidrug-resistant HIV after initial therapy with nonnucleoside reverse transcriptase inhibitor-based regimens.