Predictors of bacterial pneumonia in Evaluation of SUbcutaneous Interleukin-2 in a Randomized International Trial (ESPRIT).

BACKGROUND AND OBJECTIVES: Bacterial pneumonia still contributes to morbidity/mortality in HIV infection despite effective combination antiretroviral therapy (cART). Evaluation of SUbcutaneous Interleukin-2 in a Randomized International Trial (ESPRIT), a trial of intermittent recombinant interleukin-2 (rIL-2) with cART vs. cART alone (control arm) in HIV-infected adults with CD4 counts >300 cells/uL, offered the opportunity to explore associations between bacterial pneumonia and rIL-2, a cytokine that increases the risk of some bacterial infections.
METHODS: Baseline and time-updated factors associated with first-episode pneumonia on study were analysed using multivariate proportional hazards regression models. Information on smoking/pneumococcal vaccination history was not collected.
RESULTS: IL-2 cycling was most intense in years 1-2. Over =7 years, 93 IL-2 (rate 0.67/100 person-years (PY)) and 86 control (rate 0.63/100 PY) patients experienced a pneumonia event (hazard ratio (HR) 1.06; 95% confidence interval (CI) 0.79, 1.42; P=0.68). Median CD4 counts prior to pneumonia were 570cells/ul (IL-2 arm) and 463ccells/ul (control arm). Baseline risks for bacterial pneumonia included older age, injecting drug use, detectable HIV viral load (VL)and previous recurrent pneumonia; Asian ethnicity was associated with decreased risk. Higher proximal VL (HR for 1 log(10) higher VL 1.28; 95% CI 1.11, 1,47; P<0.001) was associated with increased risk; higher CD4 count prior to the event (HR per 100 cells/uL higher 0.94; 95% CI 0.89, 1.0; P=0.04) decreased risk. Compared with controls, the hazard for a pneumonia event was higher if rIL-2 was received <180 days previously (HR 1.66; 95% CI 1.07, 2.60; P=0.02) vs >180 days previously (HR 0.98; 95% CI 0.70, 1.37; P=0.9). Compared with the control Group, pneumonia risk in the iL-2 arm decreased over timem with HRs of 1.41, 1.71, 1,16, 0.62 and 0.84 in years 1, 2, 3-4, 5-6 and 7, respectively.
CONCLUSIONS: Baterial pneumonia rates in cART-treated adults with moderate immunodeficiency are high. The mechanism of the association between bacterial pneumonia and recent IL-2 receipt and/or detectable HIV vireaemia warrants further exploration.