Kinetics of HIV infection of human placental syncytiotrophoblast cultures: an ultrastructural and immunocytochemical study.
We previously demonstrated that syncytiotrophoblast (ST) cells from term human placentas could be infected when cocultured with HIV-infected lymphocytic cells. Here, we have used fluorescence microscopy and transmission electron microscopy to examine the kinetics of this infection process. Molt-4 clone 8 cells infected with HIV-1Lai or filtered supernatant from these cultures were incubated with ST cells for different times. In cell-associated infection, immunofluorescence microscopy revealed that some ST colonies were positive for HIV core proteins (p24,p55) after 1 hr. The number of positive colonies and the intensity of the ST-associated fluorescence increased with time. Transmission electron microscopy showed viral particles with HIV morphology associated with the ST cell surface at 1 hr. Immature virions with budding morphology 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 pattern and intensity resembled that seen with cell-mediated infection at 4 hr. Transmission electron microscopy revealed an increasing number of viral particles associated with the ST cell plasma membrane with respect to time, and budding virions first appeared at 8 hr. These results demonstrate that HIV infection of placental ST cells proceeds very rapidly in culture and that, furthermore, cell-associated infection of ST is much more efficient than the infection with cell-free virus.
Fazely
F
F
Department of Medical Pathology, School of Medicine, University of California, Davis 95616, USA.
Fry
G N
GN
Thirkill
T L
TL
Hakim
H
H
King
B F
BF
Douglas
G C
GC
D002999:Clone Cells; D005260:Female; D015683:Gene Products, gag / Q000378:metabolism; D016655:HIV Core Protein p24 / Q000378:metabolism; D015658:HIV Infections / Q000209:etiology* / Q000378:metabolism / Q000821:virology; D015497:HIV-1 / Q000378:metabolism / Q000472:pathogenicity* / Q000648:ultrastructure; D006801:Humans; D007150:Immunohistochemistry; D007700:Kinetics; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D011247:Pregnancy; D011498:Protein Precursors / Q000378:metabolism; D014327:Trophoblasts / Q000378:metabolism / Q000648:ultrastructure / Q000821:virology*
D015683:Gene Products, gag; D016655:HIV Core Protein p24; D011498:Protein Precursors; C059767:p55 gag precursor protein, Human immunodeficiency virus 1