Functional Chimeras of Human Immunodeficiency Virus Type 1 gp120 and Influenza A Virus (H3) Hemagglutinin

Abstract

In an attempt to produce a protein that will allow determination of the native human immunodeficiency virus type 1 (HIV-1) gp120 (Env) structure in its trimeric state, we fused the globular head of gp120 to the stalk region of influenza virus A (X31) hemagglutinin (HA). The chimeric protein (EnvHA) has been expressed by using a recombinant vaccinia virus system, and its functional characteristics were determined. EnvHA is expressed as a 120-to 150-kDa protein that can oligomerize to form dimers and trimers. It retains the low-pH (5.2 to 5.4) requirement of X31-HA to trigger membrane fusion but, unlike X31-HA, it is not absolutely dependent on exogenously added trypsin for protein processing to release the HA2 fusion peptide. In terms of receptor binding the chimeric protein retains specificity for human CD4 but, in relation to the membrane fusion event, it appears to lose the Env coreceptor specificity of the parental HIV-1 strains: NL43 for CXCR4 and JRFL for CCR5. These properties suggest that stable, functional EnvHAs are being produced and that they may be exploited in terms of structural studies. Further, the potential of introducing the envHA genes into influenza viruses, by use of reverse genetics, and their use as a therapeutic vaccine for HIV are discussed.Attachment and entry of human immunodeficiency virus type 1 (HIV-1) to a host cell is mediated by the envelope (Env) glycoproteins. Env monomers are synthesized as 160-kDa glycoproteins (gp160) in the endoplasmic reticulum, where oligomerization takes place, with trimers being the predominant form (24). The gp160 precursor is transported to the Golgi, where it is proteolytically processed by furin into gp120 and gp41 subunits, which are held together noncovalently (24,34,69). The processed Env glycoproteins are then presented on the surface of the infected cell and subsequently, through budding, form the envelopes of progeny virions (69).HIV-1 attachment to target cells is mediated by the binding of gp120 to CD4, the primary HIV-1 receptor (20). This binding exposes a site on gp120 that enables interactions with secondary coreceptors and further conformational changes (39). Thiol/disulfide exchange mediated by protein disulfide isomerase is involved in these conformational changes (2, 42). The two major HIV-1 coreceptors are the chemokine receptors CCR5 and CXCR4; CCR5 is generally considered to be the coreceptor utilized by HIV-1 virions in early, asymptomatic stages of infection, whereas viruses utilizing CXCR4 usually emerge during late stages of disease (5, 54). Binding of gp120 to the appropriate coreceptor triggers a conformational change in gp41 (15, 66). gp41 contains a short N-terminal hydrophobic sequence of amino acids, the fusion peptide, which mediates fusion of viral and host cell membranes, enabling entry of the virus into the host cell (26, 27). The conformational change in gp41, induced by the gp120-coreceptor interaction is necessary in order for this fusion to take place (15,66).It is generally accepted that knowledge of the structu...

SARS-Cov-2 Natural or Artificial? That is the Question

“…It is important to mention here that there is extensive experience in creating chimeras that include the Gp120 protein in the genome of other viruses including Ebola, Influenza, and Sendai [69][70][71][72][73][74][75][76]. The finding of genes of the HIV virus has been corroborated by two new works published on a platform of the Chinese Academy of Sciences where articles can be submitted prior to their peer review (Chinaxiv.org).…”

Plant molecular farming of virus‐like nanoparticles as vaccines and reagents

“…The high level of expression and dense packing of influenza A virus HAs on membrane-bound VNPs ~100 nm in diameter makes them ideal influenza virus vaccine candidates, as detailed above. However, the HA molecule and its associated VNPs are also potentially very useful as display vehicles for other antigens or for other purposes, as shown in a number of studies in animal cell production systems including for improving HIV-1 Env density on VLPs, that fused HIV gp120 domains onto either whole HA2 domains or just the HA2 transmembrane and cytoplasmic tail domains (TMCT; Copeland, Elliot, & Daniels, 2005;Guo et al, 2003). There is a patent application that specifies the use of TMCT and ectopic domains of HAs in plants for improving the expression level, trimerization and density of accumulation of fused domains from other viral proteins (e.g., HIV-1 gp120, SARS CoV S protein, rabies virus G protein) (D'Aoust, Couture, Lavoie, & Vezina, 2014); however, otherwise this display vehicle has not been much explored for plant-made HA-derived VNPs.…”