Influenza A virus infection impairs mycobacteria-specific T cell responses and mycobacterial clearance in the lung during pulmonary coinfection.

Individuals infected with mycobacteria are likely to experience episodes of concurrent infections with unrelated respiratory pathogens, including the seasonal or pandemic circulating influenza A virus strains. We analyzed the impact of influenza A virus and mycobacterial respiratory coinfection on the development of CD8 T cell responses to each pathogen. Coinfected mice exhibited reduced frequency and numbers of CD8 T cells specific to Mycobacterium bovis bacille Calmette-Guérin (BCG) in the lungs, and the IFN-γ CD8 T cell response to BCG-encoded OVA was decreased in the lungs of coinfected mice, when compared with mice infected with BCG alone. Moreover, after 2 wk of infection, mice coinfected with both pathogens showed a significant increase in the number of mycobacteria present in the lung compared with mice infected with BCG only. Following adoptive transfer into coinfected mice, transgenic CD8 T cells specific for OVA257–264 failed to proliferate as extensively in the mediastinal lymph nodes as in mice infected only with BCG-OVA. Also noted was a reduction in the proliferation of BCG-specific CD4 transgenic T cells in mice coinfected with influenza compared with mice infected with BCG alone. Furthermore, phenotypic analysis of CD11c+ dendritic cells from mediastinal lymph nodes of the infected mice showed that coinfection was associated with decreased surface expression of MHC class II and class I. Thus, concurrent pulmonary infection with influenza A virus is associated with decreased MHC expression on dendritic cells, reduced activation of BCG-specific CD4 and CD8 T cells, and impaired clearance of mycobacteria.

Impact of HIV-associated conditions on mortality in people commencing anti-retroviral therapy in resource limited settings

Objectives: To identify associations between specific WHO stage 3 and 4 conditions diagnosed after ART initiation and all cause mortality for patients in resource-limited settings (RLS).

Design, Setting: Analysis of routine program data collected prospectively from 25 programs in eight countries between 2002 and 2010.

Subjects, Participants: 36,664 study participants with median ART follow-up of 1.26 years (IQR 0.55–2.27).

Outcome Measures: Using a proportional hazards model we identified factors associated with mortality, including the occurrence of specific WHO clinical stage 3 and 4 conditions during the 6-months following ART initiation.

Results: There were 2922 deaths during follow-up (8.0%). The crude mortality rate was 5.41 deaths per 100 person-years (95% CI: 5.21–5.61). The diagnosis of any WHO stage 3 or 4 condition during the first 6 months of ART was associated with
increased mortality (HR: 2.21; 95% CI: 1.97–2.47). After adjustment for age, sex, region and pre-ART CD4 count, a diagnosis of extrapulmonary cryptococcosis (aHR: 3.54; 95% CI: 2.74–4.56), HIV wasting syndrome (aHR: 2.92; 95%CI: 2.21 -3.85), nontuberculous mycobacterial infection (aHR: 2.43; 95% CI: 1.80–3.28) and Pneumocystis pneumonia (aHR: 2.17; 95% CI 1.80–3.28) were associated with the greatest increased mortality. Cerebral toxoplasmosis, pulmonary and extra-pulmonary
tuberculosis, Kaposi’s sarcoma and oral and oesophageal candidiasis were associated with increased mortality, though at lower rates.

Conclusions: A diagnosis of certain WHO stage 3 and 4 conditions is associated with an increased risk of mortality in those initiating ART in RLS. This information will assist initiatives to reduce excess mortality, including prioritization of resources for
diagnostics, therapeutic interventions and research.