Nef Stimulates Human Immunodeficiency Virus Type 1 Replication in Primary T Cells by Enhancing Virion-Associated gp120 Levels: Coreceptor-Dependent Requirement for Nef in Viral Replication

105

123

Nef is a multifunctional accessory protein of primate lentiviruses. Recently, it has been shown that the ability of Nef to downmodulate CD4, CD28, and class I major histocompatibility complex is highly conserved between most or all primate lentiviruses, whereas Nef-mediated downregulation of T-cell receptor-CD3 was lost in the lineage that gave rise to human immunodeficiency virus type 1 (HIV-1). Whether or not other Nef activities are preserved between different groups of primate lentiviruses remained to be determined. Here, we show that nef genes from a large variety of HIVs and simian immunodeficiency viruses (SIVs) enhance virion infectivity and stimulate viral replication in human cells and/or in ex vivo infected human lymphoid tissue (HLT). Notably, nef alleles from unpassaged SIVcpz and SIVsmm enhanced viral infectivity, replication, and cytopathicity in cell culture and in ex vivo infected HLT as efficiently as those from HIV-1 and HIV-2, their human counterparts. Furthermore, nef genes from several highly divergent SIVs that have not been found in humans were also highly active in human cells and/or tissues. Thus, most primate lentiviral Nefs enhance virion infectivity and stimulate viral replication. Moreover, our data show that SIVcpz and SIVsmm Nefs do not require adaptive changes to perform these functions in human cells or tissues and support the idea that nef alleles from other primate lentiviruses would also be capable of promoting efficient virus spread in humans.

Section: Vol 81 2007contrasting

confidence: 99%

Nef-Mediated Enhancement of Virion Infectivity and Stimulation of Viral Replication Are Fundamental Properties of Primate Lentiviruses

Münch

Rajan

Schindler

et al. 2007

105

123

“…However, these effects were limited in time since functionally defective nef alleles were also found in individuals who have controlled disease progression up to at least 11 years of infection and have thereafter showed unequivocal signs of progression to HIV disease, defined here as LP. In this regard, a recent report showed that Nef is not required for efficient replication of viruses that use solely CCR5 for entry (44). In addition, evolution of either gp41 Env in macaques infected with SIV deleted of nef (2) or chemokine coreceptor use towards CXCR4 in individuals infected with nef-deleted HIV (34) has been reported.…”

Section: Discussionmentioning

confidence: 99%

Nef Alleles from Human Immunodeficiency Virus Type 1-InfectedLong-Term-Nonprogressor Hemophiliacs with or without Late Disease Progression Are Defective in Enhancing Virus Replication and CD4 Down-Regulation

Crotti

Neri²,

Corti

et al. 2006

“…Quantitative ELISA for gp120. gp120 levels on virions were determined by ELISA as previously described (43). Briefly, Immulon flat-bottom 96-well plates (Dynex) were coated with gp120-specific sheep polyclonal antibody (4 g/ml; Cliniqa Inc.) for at least 6 h. Individual wells were blocked with 5% donor calf serum in PBS for 1 h, following washes.…”

Section: Methodsmentioning

confidence: 99%

A Mutation in the Human Immunodeficiency Virus Type 1 Gag Protein Destabilizes the Interaction of the Envelope Protein Subunits gp120 and gp41

Davis

Jiang

Zhou

et al. 2006

Self Cite

The Gag protein of human immunodeficiency virus type 1 (HIV-1) associates with the envelope protein complex during virus assembly. The available evidence indicates that this interaction involves recognition of the gp41 cytoplasmic tail (CT) by the matrix protein (MA) region of Pr55Gag . Here we show that substitution of Asp for Leu at position 49 (L49D) in MA results in a specific reduction in particle-associated gp120 without affecting the levels of gp41. Mutant virions were markedly reduced in single-cycle infectivity despite a relatively modest defect in fusion with target cells. Studies with HIV-1 particles containing decreased levels of envelope proteins suggested that the L49D mutation also inhibits a postentry step in infection. Truncation of the gp41 tail, or pseudotyping by vesicular stomatitis virus glycoprotein, restored both the fusion and infectivity of L49D mutant virions to wild-type levels. Truncation of gp41 also resulted in equivalent levels of gp120 on particles with and without the MA mutation and enhanced the replication of the L49D mutant virus in T cells. The impaired fusion and infectivity of L49D mutant particles were also complemented by a single point mutation in the gp41 CT that disrupted the tyrosine-containing endocytic motif. Our results suggest that an altered interaction between the MA domain of Gag and the gp41 cytoplasmic tail leads to dissociation of gp120 from gp41 during HIV-1 particle assembly, thus resulting in impaired fusion and infectivity.