Secondary: proportion of patients in each classification of clinical critical treatment index (baseline, Days 7, 14, 28), all cause mortality on Day 28, invasive mechanical ventilation rate (Day 28), duration of oxygen therapy (Day 28), duration of hospitalization (Day 28), incidence of nosocomial infection (Day 28), CD4+ T cell count by flow cytometry in two groups (baseline, Day, 3, 6, 10, 14, 21, 28)