HIV infection of human fetal intestinal explant cultures induces epithelial cell proliferation

Abstract

Objective: The concept that HIV infection per se alters small intestinal mucosal structure and function (HIV enteropathy) remains controversial and in this study we report in vitro experiments designed to elucidate the matter.

Methods: Twenty pairs of human fetal intestinal tissue explants were maintained in vitro for up to 14 days; one explant of each pair was incubated and infected with HIV, and the other served as a matched uninfected control. At various times after infection, explant culture fluid and tissue were removed, p24 concentration was measured and tissue formalin fixed. Explant tissue was embedded in paraffin wax and sections stained by an immunoperoxidase method directed against proliferating cell nuclear antigen (PCNA). The percentage of proliferating crypt and villous epithelial cells, stained by PCNA, was calculated in paired samples. The difference between the percentage for paired samples was designated delta crypt proliferation (delta CP) and delta villous proliferation (delta VP), respectively. Epithelial cell proliferation was deemed to be enhanced if the percentage of PCNA-stained cells was greater in the HIV-infected than in the control tissue.

Results: Explant culture fluid from tissue exposed to HIV showed a progressive rise in p24 antigen (Ag) level, indicating HIV infection of these explants. Fifteen pairs of explants showed progressively positive delta CP with time (P < 0.01) indicating crypt hyperplasia and all 20 pairs of explants showed positive delta VP, indicating hyperplasia of villous epithelial cells.

Conclusions: This study provides direct evidence that HIV stimulates epithelial cell proliferation in intestinal mucosa. HIV-infected human intestinal explants provide a model of crypt hyperplastic villous atrophy previously described as HIV enteropathy and detected in clinical biopsy specimens from HIV-infected patients.