Modulation of cell growth and host protein synthesis during HIV infection in vitro
A M Di Rienzo1, P G Petronini, D Guetard
1Istituto di Patologia Generale, University of Parma, Italy.
Insights
Crude HIV preparations inhibit CEM cell proliferation due to membrane contaminants. Purified HIV virions, however, stimulate cell growth, indicating a complex interaction during human immunodeficiency virus (HIV) infection.
Area of Science:
- Virology
- Cell Biology
- Immunology
Background:
- HIV infection of T-lymphocyte cell lines can alter cellular processes.
- Viral preparations can vary in purity, potentially affecting experimental outcomes.
- Understanding HIV's impact on host cell growth and protein metabolism is crucial.
Purpose of the Study:
- To investigate the differential effects of crude versus purified HIV preparations on CEM cell growth and protein turnover.
- To identify the components responsible for observed growth inhibition or stimulation.
- To elucidate the mechanisms underlying HIV-induced changes in cell proliferation and protein metabolism.
Main Methods:
- In vitro culture of CEM cells.
- Infection with crude HIV supernatants and purified HIV virions.
- Cell proliferation assays.
- Protein synthesis and degradation studies.
- Use of soluble CD4 for viral neutralization.
- Analysis of purified membrane preparations.
Main Results:
- Crude HIV supernatants significantly inhibited CEM cell proliferation, attributed to contaminating membrane fragments.
- Purified HIV virions progressively stimulated CEM cell growth, an effect blocked by soluble CD4.
- Heat-inactivated virus or Zidovudine (ZDV)-treated virus also stimulated proliferation.
- While general protein synthesis was not inhibited by purified virions, both crude and purified preparations led to reduced protein content and increased degradation.
Conclusions:
- Contaminants in crude HIV preparations are responsible for growth inhibition, not the virus itself.
- Purified HIV virions possess intrinsic properties that stimulate cell proliferation, independent of viral replication.
- HIV infection, regardless of preparation purity, results in decreased cellular protein content and increased degradation.
Abstract:
During HIV infection of CEM cells cultured in vitro, significant differences in growth rate and protein turnover were observed with different viral preparations. There was a significant inhibition of proliferation after infection with crude HIV supernatants. On the other hand, infection with purified HIV particles obtained by filtration, differential centrifugation, and isopycnic sedimentation led to a progressively increasing stimulation of cell growth. This early stimulation was prevented by neutralizing the virus with soluble CD4 molecules. Study of cell growth in the presence of a purified membrane preparation indicated that membrane fragments contaminating the crude HIV supernatant were responsible for the observed growth inhibition. Interestingly, the stimulation of proliferation was also observed with heat-inactivated virus or after inhibition of viral replication with ZDV. In the presence of purified HIV virions, the rate of general protein synthesis was not inhibited, as is usually observed with crude viral supernatants. However, a marked reduction in protein content and increased protein degradation was found in cultures infected with either crude or purified HIV preparations.
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