Microbiota and Probiotics in Health and HIV Infection
Over the past 20 years, there has been growing interest in studying the effects of probiotics on health, leading to extensive research in the food and pharmaceutical industries to examine their impact on immune response regulation and their applications in disease prevention. The Food and Agriculture Organization/World Health Organization (FAO/WHO) defines probiotics as "live microorganisms which, when administered in adequate amounts, confer a health benefit on the host."
The human body hosts over 10¹⁴ microorganisms on its surfaces, including the lungs, oral mucosa, vagina, and intestines, which begin forming from birth and constitute the body’s microbiota. Approximately 99% of this microbiota resides in the gastrointestinal (GI) tract and has evolved alongside humans. This microbiota significantly influences digestive functions and mucosal immune responses, substantially impacting the host's health. As such, the gut microbiota is the most extensively studied microbiota and serves as a model for understanding host-microbiota interactions and diseases.
The GI tract is a primary site for HIV replication, and gastrointestinal disorders are among the most common complaints in HIV-infected patients. These patients often experience gastric hypoacidity, increasing the risk of opportunistic infections. Moreover, delayed gastric emptying can promote bacterial overgrowth in the upper GI tract, contributing to chronic diarrhea, weight loss, dysphagia, and odynophagia. Symptoms like nausea, vomiting, and abdominal pain are also common.
HIV infection negatively impacts the interaction between gut microbiota and the immune system. The gradual decline in immunity, ineffective epithelial repair, and increased epithelial permeability contribute to gastrointestinal disorders. In individuals with HIV or acquired immunodeficiency syndrome (AIDS), the small intestinal wall is damaged, crypts enlarge, and microvilli atrophy reduces their surface area. These changes lead to malabsorption, gastrointestinal discomfort, and reduced nutrient intake.
Various hypotheses suggest that probiotics can protect intestinal mucosal surfaces and delay the progression of HIV infection to AIDS. Probiotics are a cost-effective and beneficial approach to reducing mortality and HIV-related illnesses. They can combat HIV through various mechanisms, including competing for nutrients, adhering to the epithelium and mucosa to prevent epithelial invasion, countering inflammatory processes, stabilizing gut microbiota to maintain intestinal barrier integrity, preventing translocation of microbes, reducing mucosal and systemic inflammation, stimulating the production of antimicrobial substances, and enhancing gastrointestinal immune responses such as IgA.
Studies have shown that the use of probiotics, particularly as an adjunct strategy for HIV patients undergoing antiretroviral therapy (ART), can improve antioxidant defenses and help restore immune function.