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Modulation of cell surface molecules during HIV-1 infection of H9 cells. An immunoelectron microscopic study
T Meerloo1, H K Parmentier, A D Osterhaus
1Department of Pathology, University Hospital, Utrecht, The Netherlands.
Insights
Host cell molecules concentrate on budding HIV-1 virions during early infection, impacting cell surface molecule density. This may explain the disappearance of molecules like CD4 from the cell membrane post-infection.
Area of Science:
- Virology
- Immunology
- Cell Biology
Background:
- Human Immunodeficiency Virus type 1 (HIV-1) infection alters host cell surface molecules.
- Understanding the dynamic interplay between viral proteins and host cell markers is crucial for comprehending viral pathogenesis.
Purpose of the Study:
- To investigate the localization of host cell surface molecules and HIV-1 proteins on infected H9 cells using immunogold electron microscopy.
- To analyze single and double labeling patterns of host-derived molecules and HIV-1 proteins.
Main Methods:
- H9 cells were infected with HIV-1 and analyzed 2 days post-infection.
- Immunocytochemistry and conventional transmission electron microscopy with cryo-ultramicrotomy were employed.
- Double immunogold labeling was used to detect host antigens (CD3, CD4, HLA-DR, etc.) and HIV-1 antigens (gag p24, env gp41, gp120, etc.).
- Quantitative assessment of cell membrane labeling density for leukocyte markers was performed.
Main Results:
- HIV-1 virions expressed gag p24, pol, env gp41, and gp120.
- Uninfected cells showed random distribution of surface molecules like CD4; CD63 was mainly cytoplasmic.
- Infected cells displayed CD4 labeling at sites of viral budding and on free virions.
- Virions also showed labeling for CD3, CD5, CD25, CD30, CD63, and HLA-DR.
- Infected cells had significantly lower densities of CD4, CD5, and HLA-DR compared to uninfected cells.
- A significant increase in CD63 labeling density was observed in infected cells.
Conclusions:
- Host cell molecules accumulate on budding HIV-1 structures and newly formed virions during early infection.
- This phenomenon may lead to the depletion of specific host molecules, such as CD4, from the cell membrane after HIV-1 infection.
Objective:
To study cell surface molecules and HIV-1 proteins on H9 cells 2 days after infection by immunogold electron microscopy, either in single or in double labelling using combinations of host cell-derived molecules and HIV-1 proteins.
Design And Methods:
The presence of host cell antigens CD3, CD4 and human leukocyte antigen-DR (HLA-DR) and HIV-1 antigens gag p15, p17, p24 and env gp41 was evaluated using immunocytochemistry at the light microscopic level. H9 cells 2 days after infection were processed for conventional transmission electron microscopy and cryo-ultramicrotomy. Leukocyte antigens investigated were CD2, CD3, CD4 (two antibodies), CD5, CD8, CD25, CD30, CD63 antigens and HLA-DR; HIV-1-encoded antigens were gag p24, pol reverse transcriptase, and env gp41 and gp120. Double immunogold labelling was performed using reagents with different sized gold particles. For leukocyte markers, the labelling density of the cell membrane was assessed quantitatively on uninfected and infected H9 cells.
Results:
Infected cells revealed the presence of gag p24, pol, and env gp41 and gp120 antigens on HIV-1 virions. Uninfected H9 cells showed a random distribution of cell surface molecules, including CD4 antigen, along the plasma membrane. The CD63 antigen, a lysosomal membrane glycoprotein, was located mainly in the cytoplasm of uninfected cells. Cells 2 days after infection showed CD4 labelling on sites where virions were budding from or attached to the cell surface and on free virions. Virions also showed labelling by CD3, CD5, CD25, CD30 and CD63 antibodies and anti-HLA-DR. Compared with uninfected cells, a significantly lower density was found on infected cells in labelling for CD4, CD5 and anti-HLA-DR. A significantly higher density on cells 2 days after infection was seen in CD63 labelling.
Conclusion:
During the first phase of infection host cell molecules concentrate on budding structures and newly generated HIV-1 virions. This phenomenon might contribute to the disappearance of these molecules (like the CD4 molecule) from the cell membrane after infection.
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