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J. Virol., 09 1997, 6359-6372, Vol 71, No. 9
RT Kilani, LJ Chang, MI Garcia-Lloret, D Hemmings, B Winkler-Lowen and LJ Guilbert
Whether cell-free human immunodeficiency virus type 1 (HIV-1) can
productively infect placental trophoblasts (which in turn could transmit
the virus into the fetal circulation) is controversial but essential to
know for the evaluation of alternative routes (such as cell-mediated
infection or trophoblast damage). We have addressed infection factors such
as cell purity, source, culture methods, and activation states as well as
virus variant and detection methods to conclusively determine the outcome
of trophoblast challenge by free virus. Pure (> 99.98%) populations of
trophoblasts from 11 different placentas were challenged at a multiplicity
of infection (MOI) as high as 6 with five different HIV-1 variants, three
of which are non- syncytium-forming, macrophage-tropic isolates from
infected infants, with and without coinfection with cytomegalovirus; these
preparations were monitored for productive infection for up to 3 weeks
after challenge by five different criteria, the most sensitive of which
were cocultivation with target cells that can detect virus at an MOI of
10(- 7) and HIV DNA PCR that detects 30 virus copies per 10(5) cells.
Infection was never detected. However, molecularly cloned T-cell (pNL4- 3)-
and macrophage (pNLAD8)-tropic provirus plasmids, when transfected into
primary trophoblasts, yielded productive infections, indicating that
trophoblasts do not suppress late-stage virus replication and assembly.
Because of the purity of the trophoblast preparations, the extended length
of the infection culture period, the number of trophoblast preparations and
virus types examined, the sensitivity of the bioassays and molecular
detection assays, and the observations that trophoblasts can support virus
replication from provirus, the results of this study strongly argue that
free virus cannot infect primary villous trophoblasts.
Copyright © 1997, American Society for Microbiology
Placental trophoblasts resist infection by multiple human immunodeficiency virus (HIV) type 1 variants even with cytomegalovirus coinfection but support HIV replication after provirus transfection
Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Canada.
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