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Long-term cotrimoxazole prophylaxis reduces mortality and morbidity in HIV infection but the mechanisms underlying these sustained clinical benefits are unclear. Here we investigate the impact of cotrimoxazole on systemic inflammation, an independent driver of HIV mortality. In HIV-positive Ugandan and Zimbabwan children receiving antiretroviral therapy, we show that plasma inflammatory markers were lower after randomization to continue (n=144) versus stop (n=149) cotrimoxazole. This was not explained by clinical illness, HIV progression or nutritional status. Since sub-clinical enteropathogen carriage and enteropathy can drive systemic inflammation, we explored the impact of cotrimoxazole on the gut microbiome and biomarkers of intestinal inflammation. Although global microbiome community composition was unchanged, viridans group Streptococci and streptococcal mevalonate pathway enzymes were lower among children who continued (n=36) versus stopped (n=36) cotrimoxazole. These changes were associated with lower fecal myeloperoxidase. To isolate direct effects of cotrimoxazole on immune activation from its antibiotic properties, we established in vitro models of systemic and intestinal inflammation. In vitro cotrimoxazole treatment had modest but consistent inhibitory effects on pro-inflammatory cytokine production by blood leukocytes from HIV-positive (n=16) and HIV-negative (n=8) U.K. adults. It also reduced IL-8 production by inflamed gut epithelial cell lines. Together, these data demonstrate that cotrimoxazole reduces systemic and intestinal inflammation both indirectly via antibiotic effects on the microbiome, and directly by blunting immune and epithelial cell activation. Synergy between these pathways may explain the clinical benefits of cotrimoxazole despite high antimicrobial resistance, providing further rationale for extending coverage among people living with HIV in sub-Saharan Africa.

The introduction of HAART has had a major impact on the natural history of CMV retinitis with improved survival time and decreased risk of progression following diagnosis. However, immune reconstitution may be associated with inflammatory complications which can result in significant visual loss in the absence of active CMV disease.

HAART including a protease inhibitor can result in the complete suppression of CMV viraemia, an effect not previously observed in HIV-infected patients in the absence of specific anti-CMV therapy. This response correlated with protection against CMV retinitis in a group of patients at high risk of development of disease. These results help to explain why the natural history of CMV disease has altered since the introduction of such therapeutic regimens.

There was a considerable decline in AIDS-defining illnesses during 1996 and 1997, coinciding with the rapid development of new antiretroviral treatments and combinations of treatment. Further follow-up of large observational cohorts is essential to monitor the incidence of diagnoses less common than we were able to consider, such as tuberculosis, cryptosporidiosis, and cryptococcosis, and also to investigate whether the incidence of disease continues to fall, or whether it starts to rise again, as toxicities, compliance, drug resistance, and long-term side effects begin to appear.

Our data are consistent with a relationship between CD4 T-cell activation and disease progression. HIV-1 DNA load may be a better marker of viral replication and disease progression than viral RNA load. Lower level CD8 T-cell activation correlates with low viral RNA load but not with disease progression or viral DNA load.

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