Long-term follow-up study on SIV intestinal proviral load in rhesus macaques

Tubuloreticular structures in rectal biopsies of SIV-infected rhesus monkeys (Macaca mulatta)

Tubuloreticular structures (TRS) are considered to be a specific ultrastructural marker for AIDS in various organs. Experimental SIV infection in rhesus macaques is the most appropriate animal model of HIV infection. In 8 rhesus monkeys, experimentally infected with SIVmac251/MPBC, rectum biopsies were taken prior to and post infection (day 3; 1, 2, 4, 12 weeks p.i.) and were investigated by transmissionelectron microscopy to determine incidence and extent of tubuloreticular structures as well as affected cells. From the first week p.i. on TRS were found in all experimental animals as tubuli with a diameter of 20-30 nm. The tubuli were arranged in regular paracristalline formations and formed intracytoplasmatic heterogenous, polymorph accumulations, which were localized close to the endoplasmatic reticulum. In the rectal lamina propria macrophages, endothelial cells, plasma cells, lymphocytes, fibroblasts, and neutrophilic granulocytes were the affected cell types. In 5 control biopsies TRS were detected, too, but, in contrast to SIV-infected animals, they appeared only singular and very small. The results indicate that TRS are a characteristic morphologic criteria of intestinal SIV infection. They appear in very early stages of the infection. In the rectum, they can be detected as bigger, conspicuous, and abundant formations in several cells and have a restricted diagnostic and prognostic validity.

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Immunohistochemical detection of simian immunodeficiency virus (SIV) in rectal mucosa of experimentally infected rhesus macaques (Macaca mulatta)

Experimental simian immunodeficiency virus (SIV) infection is the most appropriate animal model for human HIV infection. Eight male rhesus monkeys (Macaca mulatta) were intravenously or intrarectally infected with SIVmac251/MPBMC to comparatively investigate the distribution and spread of the virus within the rectum during the course of the disease. SIV-positive cells were immunohistochemically detected in rectal biopsies obtained at days 3 and 7 and week 2, 4 and 12 postinfection. SIV-expressing cells were detected for the first time at one week after experimental infection and were present in the lamina propria and lymph follicles. Numbers of positive cells per individual animal varied strongly in time, with a more rapid rise in animals with rapid progression of the disease. Differences were not observed between intravenous and intrarectal infection. Our observations support the significance of the intestinal tract as target organ in initial pathogenesis of SIV infection.