HIV infection leads to destruction of CD4+T cells in the gut-associated lymphoid tissue (GALT) and promotes a decline in mechanical barrier functions of the gut mucosa, and the subsequent translocation of microbial products from the gastrointestinal tract to systemic circulation. The gut mucosal immune system is not completely restored by cART, and the resultant microbial translocation may contribute to chronic inflammation, inadequate CD4 T-cell recovery, and increased rates of serious non-AIDS events. Many studies have revealed strong and characteristic compositional differences in gut microbiota between individuals with HIV infection and seronegative controls. So far, several probiotic organisms have shown the ability to enhance intestinal epithelial barrier functions, reduce inflammation, and support effective Th-1 responses. Probiotics mainly stimulates polymeric IgA secretion, avoid bacterial overgrowth and their translocation, and produce a self-limited inflammatory response through development of regulatory T (Treg) cells by anti-inflammatory cytokine production. Therefore, we design a prospective, randomized, double-blind, placebo-controlled study to determine whether the use of a probiotic can expand beneficial microbiota that aid in decreasing bacterial translocation and pro-inflammatory cytokine production, thereby improving immune functions in HIV-infected subjects. Participants in the intervention group will receive oral probiotic containing 3 billion Bifidobacterium and 1 billion Lactobacillus once daily, while those in the placebo group will take placebo which contains no probiotic but has the same flavor and characteristics as the probiotic product.. Gut bacterial community diversity and composition, immune recovery and activation in peripheral plasma, plasma levels of gut damage, microbial translocation and inflammation at baseline and after 12 months of receiving intervention will be analyzed.

Inclusion Criteria:

• 18-65 years old;
• Documented HIV infection;
• No history of gastrointestinal diseases;
• Good adherence and promise to follow-up;
• Ability to provide informed consent.

Exclusion Criteria:

• Administration of antibiotics, probiotics, or prebiotics or experience of diarrhea within the previous 3 months;
• Administration of anti-inflammatory drugs, corticosteroids, immunosuppressive drugs, immunomodulator within the previous 3 months;
• Severe organ dysfunction;
• Pregnancy or breastfeeding.

Patients were recruited from the Department of Infectious Diseases, Peking Union Medical College Hospital, Beijing, China. All participants are Chinese and meet eligibility criteria.