HIV-1 Nef is a multifunctional protein with well-known lethal properties. HIV infects various cells from the brain compartment and expressed nef is responsible for developing neuropathogenic potential. HIV-infected glial cells express nefvirotoxinand stimulate the cascade of various pathways to activate uninfected cells to release neurotoxic elements damaging cells themselves. A lot of genetic variabilities of this protein have been reported from patients with HIV-associated neurocognitive disorders. To determine the neurotoxic potential of subtype-specific nef plasmids and nef plasmids of clinical samples with and without HAND were transfected in normal human astrocytes (NHA) and monocyte-derived macrophages (MDM) using nef-pCMV-HA plasmid constructs. Supernatants from subtype-specific Nef plasmids indicated the upregulation of proinflammatory cytokines. The induced expression might be due to the nef genetic variability or variations in the transfection efficiency and expression levels of nef.The mRNA expression of IL-6, IP-10, and TNF-α indicated upregulation of 5.0-fold in NHA and 3-fold in MDM with respect to empty vector control transfection. Further, the kynurenine metabolites were also assessed from culture supernatants of NHA and MDM indicating the upregulation of IDO and KYNU in NHA by 3.0-fold and 3.2-fold in MDM.The expression levels of nef and cytokines at the translational level were confirmed by western blotting and bio-plex Pro cytokine estimation assay respectively along with controls expressing green fluorescent protein (GFP).The oxidative stress was also found to be elevated as compared to control cells as determined by the estimation of nitric oxide from the culture supernatant to confirm the neurotoxic potential of HIV nef plasmids. The downregulation in the levels of cytokines, as well as kynurenine metabolites, was observed in culture supernatants after blocking the expression of nef using HIV nef siRNA. Phylogenetic analysis of Nef sequences indicated subtype C predominance except one sequence showing the partial sequence of HIV-1 subtype B sequence forming BC recombinantThe upregulation in the cytokine and pathway-specific metabolites might be linked with the neurotoxic potential of HIV-1 Nef leading to neuropathogenesis. In conclusion, the variation in the transfection efficiency, nef expression levels, and the genetic variability of Nef might be responsible for upregulating the expression levels of cytokines and kynurenine metabolites in astrocytes and MDM.

The HIV-1 nef gene terminates in a 3’-UGA stop codon, which is highly conserved in the main group of HIV-1 subtypes, along with a downstream potential coding region that could extend the nef protein by 33 amino acids, if readthrough of the stop codon occurs. Antisense tethering interactions (ATIs) between a viral mRNA and a host selenoprotein mRNA are a potential viral strategy for the capture of a host selenocysteine insertion sequence (SECIS) element (Taylor et al, 2016) [1]. This mRNA hijacking mechanism could enable the expression of virally encoded selenoprotein modules, via translation of in-frame UGA stop codons as selenocysteine (SeC). Here we show that readthrough of the 3’-terminal UGA codon of nef occurs during translation of HIV-1 nef expression constructs in transfected cells. This was accomplished via fluorescence microscopy image analysis and flow cytometry of HEK 293 cells, transfected with engineered GFP reporter gene plasmid constructs, in which GFP can only be expressed by translational recoding of the UGA codon. SiRNA knockdown of thioredoxin reductase 1 (TR1) mRNA resulted in a 67% decrease in GFP expression, presumably due to reduced availability of the components involved in selenocysteine incorporation for the stop codon readthrough, thus supporting the proposed ATI. Addition of 20 nM sodium selenite to the media significantly enhanced stop codon readthrough in the pNefATI1 plasmid construct, by >100%, supporting the hypothesis that selenium is involved in the UGA readthrough mechanism.

Human Immunodeficiency Virus (HIV) infection and its latent recurrent infection make vaccine development a significant challenge for traditional vaccines; however, the mRNA delivery of multiepitope antigens capable of creating antibodies against the surface proteins of HIV-1 and HIV-2 along with their respective Nef proteins, responsible for the latent infection can bring a most effective, as well as affordable solution to the unresolved epidemics of HIV. In this paper, we present the complete design of a multiepitope vaccine to prevent acute infections and inactivate Nef proteins that block the MHC-1 and MHC-2 pathways to hide the virus for later reinfection.