F. Fazely et al., KINETICS OF HIV-INFECTION OF HUMAN PLACENTAL SYNCYTIOTROPHOBLAST CULTURES - AN ULTRASTRUCTURAL AND IMMUNOCYTOCHEMICAL STUDY, AIDS research and human retroviruses, 11(9), 1995, pp. 1023-1030
We previously demonstrated that syncytiotrophoblast (ST) cells from te
rm human placentas could be infected when cocultured with HIV-infected
lymphocytic cells, Here, we have used fluorescence microscopy and tra
nsmission electron microscopy to examine the kinetics of this infectio
n process, Molt-4 clone 8 cells infected with HIV-1(Lai) or filtered s
upernatant from these cultures were incubated with ST cells for differ
ent times, In cell-associated infection, immunofluorescence microscopy
revealed that some ST colonies were positive for HIV core proteins (p
24,p55) after 1 hr, The number of positive colonies and the intensity
of the ST-associated fluorescence increased with time, Transmission el
ectron microscopy showed viral particles with HIV morphology associate
d with the ST cell surface at 1 hr, Immature virions with budding morp
hology were observed at 2 hr, In cell-free infection, positive p24,p55
staining was first detected in a few ST colonies at 4 hr, The number
of positive colonies increased with time, At 24 hr, the fluorescence p
attern and intensity resembled that seen with cell-mediated infection
at 4 hr, Transmission electron microscopy revealed an increasing numbe
r of viral particles associated with the ST cell plasma membrane with
respect to time, and budding virions first appeared at 8 hr, These res
ults demonstrate that HIV infection of placental ST cells proceeds ver
y rapidly in culture and that, furthermore, cell-associated infection
of ST is much more efficient than the infection with cell-free virus.