Direct in vitro infection of human intestine with HIV-1

To directly infect human fetal intestine with HIV in vitro.

Human fetal intestinal explant cultures were exposed to HIV-1 and monitored for evidence of infection by biochemical assay, immunohistochemistry and in situ hybridization.

Human fetal intestinal explants (14-21 weeks) were established in culture and exposed to HIV-1. Tissue culture fluid was assayed for p24 antigen and reverse transcriptase activity over a 14-day period. Explants were removed from culture on days 4, 7, 10 and 14 postinoculation and subjected (1) to immunohistochemistry to detect p24 and gp160/41 antigens, and (2) to in situ hybridization to detect HIV-1 RNA. Explant tissue culture fluid was cocultured with Jurkat T-cells to detect infectious viral particles.

Reverse transcriptase activity and p24 antigen levels in fetal explant culture fluid rose between 7 and 14 days after viral inoculation. Jurkat T-cell cocultures confirmed the presence of infectious virus. Cells in the lamina propria resembling lymphocytes and macrophages of both small intestine and colon stained positively for the viral proteins p24 and gp41. The same type of cells also stained positively for HIV-1 RNA using in situ hybridization. Dual-label immunohistochemistry, combined immunohistochemistry and in situ hybridization confirmed the presence of viral protein and RNA in cells bearing the CD3, CD4 (lymphocyte) or CD68 (macrophage) surface markers. There was no evidence at any time of HIV-1 infection of epithelial cells.

Cells of the lamina propria of the small intestine and colon, bearing lymphocyte or macrophage markers, can be directly infected by and support the replication of HIV-1. Such infection may be implicated in the pathogenesis of HIV enteropathy.