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CD14lo/CD16hi Monocytes are More Permissive to HIV-1 Infection in vitro and May Selectively Harbour HIV-1 in Patients on HAART
P Ellery1,2, C Sonza1, G Paukovics1, P U Cameron3, A Solomom2,4, SR Lewin2,4, S M Crowe*1,2,4,5, and
1Macfarlane Burnet Inst. for Med. Res. and Publ. Hlth., Melbourne, Australia; 2Monash Univ., Melbourne, Australia; 3Univ. of Melbourne, Australia; 4Alfred Hosp., Melbourne, Australia; and 5Natl. Ctr. for HIV Virology Res., Melbourne, Australia
Background: HIV-1 has been
shown to persist in a number of cell types despite effective HAART. Previously,
our laboratory has shown infectious HIV-1 may be readily recovered from
monocytes of patients on HAART with undetectable VL. As less than 1% of monocytes
harbor HIV, we hypothesize that there is a subset of monocytes which is more susceptible
to HIV infection. The minor CD14lo/CD16hi subset of
monocytes (5 to 15% in healthy individuals) has been reported previously to be
expanded in HIV-infected individuals.
Methods: We used a whole
blood flow cytometric assay to analyze monocyte subsets and CCR5 expression on monocytes from HIV+
and HIV- individuals. We also isolated CD14lo/CD16hi
and CD14hi/CD16- monocytes from HIV- donors (n = 6) by high-speed flow cytometric
sorting, and immediately exposed these cells to DNase-treated HIV-1Ba-L
for 2 hours in vitro. Cells were cultured for a further 36 hours and a
combination of real-time and conventional PCR
was used to detect viral entry. CD14lo/CD16hi and CD14hi/CD16-
monocytes were also isolated from patients by either magnetic bead technology
(n=6) or flow cytometric sorting (n =
4). A sensitive PCR assay, able to
detect a single copy of viral DNA,
was used to compare the ability of monocyte subsets to harbour HIV-1 in vivo.
Results: Our cross-sectional
study suggests monocyte subsets are not significantly altered in HIV-infected
individuals (percentage of CD14lo/CD16hi monocytes; HIV+
(n = 64) mean 16.49%, HIV- (n=23) mean
14.06%, p = 0.30). The proportion of
CD14lo/CD16hi monocytes does not correlate with the
patients’ plasma viral load or CD4 count. CD14lo/CD16hi
monocytes express significantly higher CCR5
than CD14hi/CD16- monocytes (n = 52, p = <0.01),
and HIV-1 infection does not affect monocyte CCR5
expression (p =>0.05). In vitro
infection assays show CD14lo/CD16hi monocytes are more
permissive to HIV-1 infection than CD14hi/CD16- monocytes from the
same donors (n = 6, mean; 490.32 and
49.16 HIV-1 DNA copies per 10,000
cells respectively [p = 0.03]). Our data
also suggest CD14lo/CD16hi monocytes selectively harbor
HIV-1 DNA (7 of the 10 donors
examined). The ability to qualitatively detect of HIV-1 DNA
in monocytes did not correlate with viral load, CD4 count, or therapy regimen.
Conclusions: Our data suggest
CD14lo/CD16hi monocytes are preferentially infected with
HIV-1 in vitro and in vivo. This is possibly related to higher CCR5 expression observed.
Keywords: monocyte; subset; reservoir
