Background: We have observed a preferential depletion of CD4⁺ T cells from the gastrointestinal (GI) tract in acute and early HIV-1 infection. Here we compare the markers of immune activation, proliferation, and viral burden of GI CD4⁺ T cells with peripheral blood (PB) CD4⁺ T cells at this stage of infection.

Methods:  Subjects with acute and early HIV-1 infection (n = 10) as defined by the presence of plasma viremia and negative or evolving HIV-1 serology underwent phlebotomy and flexible sigmoidoscopy with biopsies. Uninfected subjects (n = 10) served as controls. Flow cytometry was utilized to phenotype GI and PB CD4⁺ lymphocytes. Immunohistochemistry was performed using the alkaline phosphatase-anti-alkaline phosphatase and peroxidase methods to assess proliferation of GI CD4⁺ T cells. PCR for HIV-1 proviral DNA and viral RNA was performed on sorted CD4⁺ T cells from the GI tract and PB.

Results:  Estimated duration of infection ranged from 2 to 14 weeks prior to enrollment. The mean CD4⁺ T-cell count in the blood was 531 cells/mm³ (380 to 1321) and the mean plasma HIV-1 RNA was 6.3 log₁₀ copies/mL (3.8 to 7.1). A mean of 8.5 GI CD4⁺ T cells from HIV-infected subjects expressed proliferation marker Ki-67 per unit area as opposed to a mean of 3.8 CD4⁺ T cells per unit area in HIV-uninfected subjects (p = 0.03). In 2 subjects tested thus far, GI CD4⁺ T cells had 30- and 80-fold more HIV-1 RNA than PB CD4⁺ T cells.

	GI CD4+ T cells	PB CD4+ T cells	p value
CD45 RO+ (mean%)	86.8%	62.9%	0.01
HLA DR+ (mean%)	32.7%	13%	<0.01
HLA DR+/CD45RO+(mean%)	30.2%	11.9%	<0.01
HIV-1 DNA (copies per 1000 cells)	93.5	25.4	0.05

Keywords: Primary HIV-1; Gastrointestinal tract; CD4+ T cells