HIV causes gastrointestinal dysfunction and microbial translocation that can provoke local and systemic inflammation that may lead to disease progression. Inflammation and intestinal permeability increase and the reduction in immune defences creates the opportunity for microbial overgrowth and raised lipopolysaccharides levels, which may lead to disease progression. HIV-infected patients also tend to have low levels of beneficial bacteria. Probiotics have the potential to stimulate the immune system through IgA secretion and reduce inflammation. Prebiotics selectively stimulate the growth of some bacteria, altering the composition and metabolic activity of gut microbiota. This randomized, prospective, double-blind controlled pilot study evaluates use of probiotics and prebiotic to expand beneficial microbiota that help decrease bacterial translocation and pro-inflammatory cytokine production, thereby improving immune functions in HIV-infected subjects. 20 HIV-infected adult patients were divided into four groups (n=5 per group) to receive probiotics, synbiotic, a prebiotic, or placebo once daily for 16 weeks. Probiotics used were Lactobacillus rhamnosus plus Bifidobacterium lactis. From baseline to week 16, the synbiotic group showed a reduction in bacterial DNA concentrations in plasma. The probiotic and synbiotic groups demonstrated a decrease in total bacterial load in feces. The probiotic group showed a significant increase in beneficial bacteria load (such as Bifidobacterium and a decrease in harmful bacteria load (such as Clostridium). The synbiotic group had greater increases in CD4+ T-cell count and cytokine levels (IL-6) decreased significantly. Serious adverse effects previously reported with the use of probiotics in immunocompromised patients were not reported in this study. The authors found no decrease in HIV-1 plasma viral load so the use of a synbiotic for maintaining an undetectable viral load as part of the primary prevention of HIV transmission is not justified.