Summary auto-generated
This study examines how HIV-1's Nef protein enhances viral infectivity by investigating its role in the replication cycle across multiple CD4+ T cell lines. Researchers compared wild-type and nef mutant viruses using growth kinetics, single-round replication assays, and infectivity measurements. Results demonstrate that Nef is dispensable during late replication phases (transcription to virion production) but is essential in early phases (from virion adsorption through integration). Importantly, the study reveals that Nef enhances infectivity in a producer cell-dependent manner—the relative infectivity advantage of wild-type virus over nef mutant virus varied significantly depending on which cell line produced the virions. In M8166, H9, and A3.01 cells, wild-type virus showed 3-5 fold greater infectivity, while in CEMx174 cells the difference increased to approximately 11-fold. These findings suggest Nef modulates viral particles during assembly or release to improve infectivity through mechanisms that vary by producer cell type, possibly through interactions with virion structural proteins or maturation processes.
Key findings
- Nef protein is required during early HIV-1 replication (from virion adsorption to integration) but not during late phases (transcription to virion production)
- Nef enhances viral infectivity in a producer cell-dependent manner, with infectivity advantages ranging from 3-fold to 11-fold depending on the cell line producing the virus
- Nef acts on viral particles during assembly or maturation stages rather than at virus entry, suggesting it modulates virion structure or composition
- Wild-type virus consistently outperformed nef mutant virus across multiple CD4+ cell lines (H9, CEMx174, A3.01, M8166), confirming Nef as a positive factor in replication
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Abstract
The growth kinetics of wild-type and nef mutant viruses of human immunodeficiency virus type 1 were comparatively analysed in several human CD4+ cell lines. Delayed replication of nef mutant virus was observed in all cell lines examined. To determine the stage in the virus replication cycle that is affected by Nef, a single-round replication assay was performed. Initially, the expression of marker genes in transfected cells was examined in order to study the role of Nef in the late phase of infection. The results obtained indicated that Nef is dispensable during the transcription to virion production stage. Next, the effect of Nef on the early phase was investigated with a single-round infection. It was demonstrated that Nef is required in the early phase of the virus replication cycle, from virion adsorption to integration. Finally, the infectivity of virus stocks prepared from four cell lines was determined. The relative infectivity of the nef mutant from the four cell lines differed. Taken together, we conclude that Nef acts via modulation of viral particles to enhance virus infectivity in a cell-dependent manner.