Identification of a nef allele that causes lymphocyte activation and acute disease in Macaque monkeys

Abstract

Residues 17 and 18 in nef of SIVmac239 were changed from RQ to YE to create a translated sequence of SRPSGDLYERLLRARGETYGRLLGEVEDGYSQSP from residues 10-43. The YXXL motifs in this context match very well with consensus sequences for SH2 binding domains and are similar to ones present in nef of the acutely lethal pathogen SIVpbj14. The YE variant of SIVmac239, unlike SIVmac239 but like SIVpbj14, replicated well in resting peripheral blood mononuclear cell cultures, caused extensive T lymphocyte activation, and produced an acute disease in rhesus and pigtailed monkeys characterized by severe diarrhea, rash, and extensive lymphoid proliferation in the gastrointestinal tract. The YEnef gene transformed NIH 3T3 cells in culture. Both 239nef and YEnef were found to associate with src in cotransfected COS cells, and both 60 kDa src and 34 kDa nef were phosphorylated at tyrosine in these cells. The extent of tyrosine phosphorylation of 239nef was considerably less than that of YEnef in these assays. These findings identify an important determinant of the SIVpbj14 phenotype, and they provide evidence of a role for nef in signal transduction and cellular activation.

HIV Nef Inhibits T Cell Migration

“…Among the regulatory proteins is Nef, whose role in viral infection and disease progression has been controversial (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11). Among the putative functions attributed to Nef are the maintenance of high viral load (1) and immune evasion due to its down-regulation of CD4 (2) and MHC I molecules (7).…”

“…Briefly, 3 ϫ 10 5 Jurkat cells or primary CD4ϩ T cells suspended in 300 l of migration medium (RPMI ϩ 0.5% bovine serum albumin) were loaded into each Transwell filter. Filters were then transferred to another well containing 600 l of migration medium with the indicated concentrations of SDF-1␣.…”

CD4+T Cells from CD4C/HIVNefTransgenic Mice Show Enhanced Activation In Vivo with Impaired Proliferation In Vitro but Are Dispensable for the Development of a Severe AIDS-Like Organ Disease

“…However, numerous controversial findings have been reported. For instance, in some in vitro studies, Nef was found to induce T-cell activation (1,3,5,6,15,16,37,55,68), while in others it was reported to inhibit (2,3,11,13,20,30,38,45,46) T-cell activation. Such conflicting results suggest that the function of Nef, particularly in vitro, may be difficult to fully appreciate.…”

“…Based on numerous observations, Nef appears to play a multifaceted role; it was found to promote high virulence and accelerate viral replication (reviewed in reference 26) and to downregulate cell surface CD4 (47,61) and major histocompatibility complex class I (MHC-I) (35) molecules, as well as to affect T-cell activation (1,3,15,38,62), proliferation (12,36), and cytokine (interleukin-2 [IL-2] and IL-10) production (7,38,67). However, numerous controversial findings have been reported.…”

Pro-apoptotic Activity of HIV-1 Auxiliary Regulatory Protein Vpr Is Subtype-dependent and Potently Enhanced by Nonconservative Changes of the Leucine Residue at Position 64

“…It is possible that other nonconservative changes of Leu 64 also promote the pro-apoptotic potential of Vpr. This result is reminiscent of SIVmac239 Nef, which upon acquiring two point mutations promotes efficient viral replication in resting cells (24). Although mutations occur frequently during HIV-1 infection, Leu 64 mutations are rarely observed (Table I).…”