Exposure to Mycobacterium tuberculosis (Mtb) results in heterogeneous clinical outcomes including primary progressive tuberculosis and latent Mtb infection (LTBI). Mtb infection is identified using the tuberculin skin test and interferon-γ (IFN-γ) release assay IGRA, and a positive result may prompt chemoprophylaxis to prevent progression to tuberculosis. In the present study, we report on a cohort of Ugandan individuals who were household contacts of patients with TB. These individuals were highly exposed to Mtb but tested negative by IFN-γ release assay and tuberculin skin test, ‘resisting’ development of classic LTBI. We show that ‘resisters’ possess IgM, class-switched IgG antibody responses and non-IFN-γ T cell responses to the Mtb-specific proteins ESAT6 and CFP10, immunologic evidence of exposure to Mtb. Compared to subjects with classic LTBI, ‘resisters’ display enhanced antibody avidity and distinct Mtb-specific IgG Fc profiles. These data reveal a distinctive adaptive immune profile among Mtb-exposed subjects, supporting an expanded definition of the host response to Mtb exposure, with implications for public health and the design of clinical trials.

Background. Cryptococcal meningitis (CM) is the proximate cause of death in 20%–30% of persons with acquired immunodeficiency syndrome in Africa.Meth

Tools to reliably measure Plasmodium falciparum (Pf) exposure in individuals and communities are needed to guide and evaluate malaria control interventions. Serologic assays can potentially produce precise exposure estimates at low cost; however, current approaches based on responses to a few characterized antigens are not designed to estimate exposure in individuals. Pf-specific antibody responses differ by antigen, suggesting that selection of antigens with defined kinetic profiles will improve estimates of Pf exposure. To identify novel serologic biomarkers of malaria exposure, we evaluated responses to 856 Pf antigens by protein microarray in 186 Ugandan children, for whom detailed Pf exposure data were available. Using data-adaptive statistical methods, we identified combinations of antibody responses that maximized information on an individual’s recent exposure. Responses to three novel Pf antigens accurately classified whether an individual had been infected within the last 30, 90, or 365 d (cross-validated area under the curve = 0.86–0.93), whereas responses to six antigens accurately estimated an individual’s malaria incidence in the prior year. Cross-validated incidence predictions for individuals in different communities provided accurate stratification of exposure between populations and suggest that precise estimates of community exposure can be obtained from sampling a small subset of that community. In addition, serologic incidence predictions from cross-sectional samples characterized heterogeneity within a community similarly to 1 y of continuous passive surveillance. Development of simple ELISA-based assays derived from the successful selection strategy outlined here offers the potential to generate rich epidemiologic surveillance data that will be widely accessible to malaria control programs. Significance Widely available accurate estimates of malaria exposure are essential for targeting and evaluation of public health interventions. Antibody responses to the malaria parasite can provide information on past exposure, but to date, most such measurements have been based on responses to a small number of parasite proteins chosen by convenience rather than utility and have not provided quantitative information on an individual’s exposure. Our results generated by screening hundreds of responses in children with known exposure histories indicate that responses to a few appropriately selected antigens can provide such information. This new approach can be transformed into high-throughput, low-cost, field-based assays useful for surveillance of malaria and has the potential to be translated into similar tools for other infectious diseases.

Background: HIV RNA viral load testing is costly and is generally unavailable in resource-limited settings. We identified predictors of viral failure and documented genotypic mutations in a subset of patients with viral failure after 12 months on antiretroviral therapy (ART). Methods: From April 2004 to June 2005, consecutive treatment-naive patients beginning ART at a university clinic in Uganda were enrolled. Clinical information, CD4 cell count, and HIV RNA level were collected at baseline and every 3 to 6 months. Independent predictors of viral failure were identified using multivariate logistic regression. Genotypic drug resistance for 8 patients with viral failure at 12 months was measured at baseline and at 6 and 12 months. Results: Five hundred twenty-six adults and 250 children (0 to 18 years of age) were started on first-line ART regimens and followed for 12 months. Outcomes could not be assessed in 13% of patients (79 died and 21 were withdrawn). Children were almost twice as likely to have viral failure compared with adults (26% vs. 14%; P = 0.0001). In adults, the sole independent predictor of viral failure was treatment with stavudine (d4T)/lamivudine (3TC)/nevirapine (NVP) versus zidovudine (ZDV)/3TC/efavirenz (EFV) (odds ratio [OR] = 2.59, 95% confidence interval [CI]: 1.20 to 5.59). In children, independent predictors of viral failure included male gender (OR = 2.44, 95% CI: 1.20 to 4.93), baseline CD4% <5 (OR = 2.69, 95% CI: 1.28 to 5.63), and treatment with d4T/3TC/NVP versus ZDV/3TC/EFV (OR = 2.46, 95% CI: 1.23 to 4.90). All 8 patients with viral breakthrough and genotypic drug resistance results had nonnucleoside reverse transcriptase inhibitor (NNRTI)- and 3TC-associated mutations. Conclusions: These data demonstrate the effectiveness of ART in a low-resource setting. Children and patients of all ages taking the d4T/3TC/NVP regimen were more likely to have viral failure. Our data suggest that viral failure occurring 6 months or more after the start of ART regimens commonly used in Uganda is likely to be associated with NNRTI- and 3TC-resistant virus.