Chimeric Viruses Expressing Primary Envelope Glycoproteins of Human Immunodeficiency Virus Type I Show Increased Sensitivity to Neutralization by Human Sera

Abstract

We constructed a number of HXB2 viruses chimeric for the gp 120 glycoprotein derived from a number of viable molecular clones obtained from a primary isolate. Comparative biological characterization of the parental primary viruses with the gp 120.HXB2 chimeras demonstrated identical patterns of cell tropism and cytopathicity. Furthermore, both parental and chimeric viruses were insensitive to neutralization by sCD4 and a panel of conformation-dependent monoclonal antibodies, demonstrating that transfer of the gp 120 protein alone was sufficient to confer a "neutralization-resistant" phenotype to the T-cell-adapted clone HXB2. We assessed the contribution of gp 120 epitopes to the neutralizing immune response by comparing the sensitivity of these viruses to neutralization by a panel of sera from HIV-infected individuals. Seven of eleven sera tested were able to neutralize HXB2 and two or more of the chimeric viruses; in contrast, only one serum neutralized more than one of the parental primary virus clones. The association of gp 120-gp41 envelope at the surface of infected PBMC cultures was measured in the presence or absence of soluble CD4. No differences in CD4-induced gp 120 dissociation were seen between the chimeric and parental virus-infected cultures. Since gp 120 conformation appeared the same between primary and chimeric viruses, we suggest that the ability of human sera to neutralize the chimeric viruses may be mediated by epitopes within gp41.

Functional Characterization of Intracellular and Secreted Forms of a Truncated Hepatitis C Virus E2 Glycoprotein

“…Recombinant human immunodeficiency virus type 1 (HIV-1) glycoprotein gp120 expressed in CHO cells was obtained from the Medical Research Council AIDS Directed Programme (ADP) Repository. Pooled HIVpositive human sera (QC256) were used to visualize GNA (Galanthus nivalis) lectin-captured gp120 as previously described (21). Recombinant glutathione S-transferase (GST) fusion proteins expressing the second extracellular loop (EC2) from both hCD81 and murine CD81 (mCD81) were constructed and expressed as previously described (11,12).…”

Detection of Antibody-Dependent Complement-Mediated Inactivation of both Autologous and Heterologous Virus in Primary Human Immunodeficiency Virus Type 1 Infection

“…The PCR conditions used were 30 cycles of 92°C for 45 s, 45°C for 45 s, and 68°C for 210 s. The amplified DNA fragment was cloned into pGEM-T Easy (Promega, Southampton, United Kingdom) and transferred into pHxB2-MCS-⌬-env by digestion with BstEII and MluI. Plasmid pHxB2-MCS-⌬-env allows incorporation of heterologous gp120 sequences from amino acid 38 (seven amino acids after the signal peptide) to 6 amino acids prior to the gp120/gp41 junction (19). The resulting molecular clones encode replication-competent viruses with gp41 derived from HIV-1 HxB2 .…”

Biological consequences of human immunodeficiency virus type 1 envelope polymorphism: does variation matter?: 1995 Fleming Lecture Delivered at the 134th Meeting of the Society for General Microbiology, 26 March 1996

“…It is interesting to note that there is no correlation between genotype and neutralization type, in that some viruses are sensitive to neutralization by serum from individuals infected with viruses of diverse clades. Likewise, some individuals, including those classified in 'non-progressor' cohorts (Cao et al, 1995 b), elicit an antibody response that can neutralize viruses from diverse clades (Fenyo et al, 1996;Kostrikis et al, 1996;Nyambi et al, 1995). These results clearly indicate that antibodies capable of neutralizing divergent primary viruses exist in response to a natural infection.…”