Abstract
The most common route of transmission of HIV is via the mucosa. We compared human and macaque intestinal epithelia to determine whether the SIV macaque system can be used as a model to study HIV transmission by the rectal route. The overall morphology of the macaque gut mucosa is very similar to that of humans. Differentiation markers follow the same pattern as in the human system. The carcinoembryonic antigen (CEA) is apical in epithelial cells of the rectum and is absent from the small intestine. Blood group H antigen is expressed by enterocytes but not by colonocytes or rectocytes. Galactosylceramide, a potential alternative receptor for HIV in epithelial cells, is expressed in all intestinal segments as in humans. In absorptive cells it is apical and intracellular in the rectum, colon, and cecum, whereas it is only intracellular in small intestine. In goblet cells the galactosylceramide is present in intracellular vacuoles in all segments. It is also present on the membrane of mucous granules in colon and small intestine but not in rectum. We therefore believe that the macaque digestive tract may constitute a good model for the human digestive tract in the transmission of lentiviruses.