HIV and the intestine

The epidemiology of human immunodeficiency virus (HIV) infection in children is characterized by a double scenario. In countries where highly active antiretroviral therapy (HAART) is available, the pattern of HIV infection is evolving into a chronic disease, whose control strictly depends on patients’ adherence to treatment. In developing countries, with no or limited access to HAART, acquired immune deficiency syndrome (AIDS) is rapidly expanding and is loaded with a high fatality ratio, due to the combined effects of malnutrition and opportunistic infections. The digestive tract is a target of the disease in both settings. Opportunistic infections are the most common cause of gastrointestinal disease in HIV patients. However, although opportunistic causes of diarrhoea have fallen dramatically in the era of HAART, overall the number of patients experiencing diarrhoea has changed very little. Severe diarrhoea associated with villous atrophy and crypt hypertrophy with no pathogen is found despite extensive investigation is defined as HIV enteropathy. The intestinal mucosa is a target for HIV and a site of significant HIV replication and cluster of differentiation (CD)4 T cell destruction, based upon the route of exposure and other aspects of mucosal immunology. Intestinal dysfunction is a specific HIV-related syndrome in children. Its pathophysiology is complex and involves multiple abnormalities. Although the mechanisms responsible for these abnormalities remain not completely known, several explanations have been put forward, from a virotoxic effect of HIV itself on enterocytes to an abnormal differentiation of enterocytes induced by HIV, to local activation of the gastrointestinal immune system. Intestinal infections with opportunistic agents and the complex interplay between intestinal malabsorption, immune impairment and infections are still responsible for the high incidence of intestinal dysfunction in children with HIV.