The site of an immune-selected point mutation in the transmembrane protein of human immunodeficiency virus type 1 does not constitute the neutralization epitope (original) (raw)
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Virology, 2011
The detailed interactions between antibodies and the HIV-1 envelope protein that lead to neutralization are not well defined. Here, we show that several conservative substitutions in the envelope gp41 led to a ~100 fold increase in neutralization sensitivity to monoclonal antibodies (MAbs) that target gp41: 4E10 and 2F5. Substitution at position 675 alone did not impact neutralization susceptibility to MAbs that recognize more distal sites in gp120 (b12, VRC01, PG9). However, changes at position 675 in conjunction with Thr to Ala at position 569 increased the neutralization sensitivity to all gp41 and gp120 MAbs and plasma, in some cases by more than 1000-fold. Interestingly, the T569A change had a dramatic effect on b12 binding, but no effect on neutralization sensitivity. This finding suggests that antibody neutralization may occur through a multi-step pathway that includes distinct changes in envelope conformation that may affect binding but not neutralization susceptibility.
Virology, 2011
Neutralizing antibodies (Nabs) are thought to play an important role in prevention and control of HIV-1 infection and should be targeted by an AIDS vaccine. It is critical to understand how HIV-1 induces Nabs by analyzing viral sequences in both tested viruses and sera. Neutralization susceptibility to antibodies in autologous and heterologous plasma was determined for multiple Envs (3–6) from each of 15 subtype-C-infected individuals. Heterologous neutralization was divided into two distinct groups: plasma with strong, cross-reactive neutralization (n = 9) and plasma with weak neutralization (n = 6). Plasma with cross-reactive heterologous Nabs also more potently neutralized contemporaneous autologous viruses. Analysis of Env sequences in plasma from both groups revealed a three-amino-acid substitution pattern in the V4 region that was associated with greater neutralization potency and breadth. Identification of such potential neutralization signatures may have important implications for the development of HIV-1 vaccines capable of inducing Nabs to subtype C HIV-1.
The Journal of general virology, 1998
Amino acids 731-752 (731PRGPDRPEGIEEEGGERDRDRS752) of the transmembrane glycoprotein gp41 of human immunodeficiency virus type 1 (HIV-1) are conserved in most virus isolates and are controversially reported to be implicated in virus neutralization. The humoral response in infected patients against this region is poor and humans immunized with gp160 show high levels of antibodies against the peptide but poor neutralization titres. Nonetheless, several groups have succeeded in obtaining neutralizing antibodies against this sequence using different antigen-presenting systems. In order to identify the sequence(s) against which the neutralizing response was generated, we used the flock house virus (FHV) antigen-presenting system to analyse neutralizing antisera from mice immunized with a cowpea mosaic virus (CPMV) chimera expressing the 731-752 sequence. Data show that the neutralizing response is uniquely directed against a conformational epitope mapping to the ERDRD portion of this seq...
Cell, 1988
Transmission and growth of HIV-1 produced from the biologically active clone HTLV-III/HXB2D in the constant presence of a neutralizing antiserum yielded a viral population specifically resistant to neutralization by the same antiserum. Molecular clones MX-1 and -2, containing the entire envelope gene, were obtained from cultures of the resistant variant. The coding regions for the large envelope protein and most of the transmembrane envelope protein of two such clones were substituted for the homologous segment of HXB2D. Infectious viruses from these constructs were also specifically resistant to neutralization by the selecting antiserum. The exchanged fragment contained only one base change, resulting in an Ala---Thr replacement at position 582. When this substitution was introduced into HXB2D it conferred the resistant phenotype. Thus, small differences may be selected for in vivo by the host immune response and result in relatively large differences in susceptibility of the virus to such a response.
Virology, 2005
Adaptation of antibody neutralization-resistant human immunodeficiency virus type I (HIV-1) to growth in vitro generally results in the acquisition of a neutralization-sensitive phenotype, an alteration of viral growth kinetics, and an array of amino acid substitutions associated with these changes. Here we examine a panel of Env chimeras and mutants derived from these neutralization-resistant and -sensitive parental Envs. A range of neutralization and infectivity phenotypes was observed. These included a modulation of the CD4 binding site (CD4bs) towards recognition by neutralizing and non-neutralizing CD4bs-directed antibodies, resulting in a globally neutralization-sensitive Env; alterations which affected Env complex stability; and interactions which resulted in differential infectivity and CCR5/CXCR4 usage. This range of properties resulted from the complex interactions of no more than three amino acids found in key Env locations. These data add to a growing body of evidence that dramatic functional alterations of the native oligomeric Env protein complex can result from relatively minor amino acid substitutions. D
Retrovirology, 2014
Background: The CD4 binding site (CD4bs) of envelope glycoprotein (Env) gp120 is a functionally conserved, important target of anti-human immunodeficiency virus type 1 (HIV-1) neutralizing antibodies. Two neutralizing human monoclonal antibodies, IgG1 b12 (b12) and VRC01, are broadly reactive neutralizing antibodies which recognize conformational epitopes that overlap the CD4bs of Env gp120; however, many CRF01_AE viruses are resistant to neutralization mediated by these antibodies. We examined the mechanism underlying the b12 resistance of the viruses using CRF01_AE Env (AE-Env)-recombinant viruses in this study. Results: Our results showed that an amino acid substitution at position 185 in the V2 region of gp120 played a crucial role in regulating the b12 susceptibility of AE-Env-recombinant viruses by cooperating with 2 previously reported potential N-linked glycosylation (PNLG) sites at positions 186 (N186) and 197 (N197) in the V2 and C2 regions of Env gp120. The amino acid residue at position 185 and 2 PNLG sites were responsible for the b12 resistance of 21 of 23 (>91%) AE-Env clones tested. Namely, the introduction of aspartic acid at position 185 (D185) conferred b12 susceptibility of 12 resistant AE-Env clones in the absence of N186 and/or N197, while the introduction of glycine at position 185 (G185) reduced the b12 susceptibility of 9 susceptible AE-Env clones in the absence of N186 and/or N197. In addition, these amino acid mutations altered the VRC01 susceptibility of many AE-Env clones. Conclusions: We propose that the V2 and C2 regions of AE-Env gp120 contain the major determinants of viral resistance to CD4bs antibodies. CRF01_AE is a major circulating recombinant form of HIV-1 prevalent in Southeast Asia. Our data may provide important information to understand the molecular mechanism regulating the neutralization susceptibility of CRF01_AE viruses to CD4bs antibodies.
Journal of Virology, 1992
The principal neutralization determinant (PND) of human immunodeficiency virus type 1 envelope glycoprotein gp120 contains a conserved GPG sequence. The effects of a 29-amino-acid deletion of most of the PND, a 3-amino-acid deletion in the GPG sequence, and 16 single-amino-acid substitutions in the GPG sequence were determined in a transient expression assay. All mutant envelope glycoproteins were expressed at levels comparable to that of the wild-type envelope, and mutations in the GPG sequence did not affect processing to gp120 or, except for the 29-amino-acid deletion, binding to CD4. Of all of the mutants, only the GHG and GFG mutants induced formation of syncytia similar in size and number to those induced by the wild-type envelope. When the envelope expression level was increased 10-fold or more, several additional mutants (APG, GAG, GSG, GQG, GVG, and GPF) also induced syncytium formation. Transfection with infectious proviral molecular clones containing the GHG, GFG, APG, GA...
Resistance of Human Immunodeficiency Virus Type 1 to Antiretroviral Agents: A Review
Clinical Infectious Diseases, 1994
The ability of human immunodeficiency virus type 1 (HIV-1) to replicate in the presence of strong immune responses to the virus may be due to its high mutation rate, which provides envelope gene variability for selection of neutralization-resistant variants. Understanding neutralization escape mechanisms is therefore important for the design of HIV-1 vaccines and our understanding of the disease process. In this report, we analyze mutations at amino acid positions 281 and 582 in the HIV-1 envelope, where substitutions confer resistance to broadly reactive neutralizing antisera from seropositive individuals. Neither of these mutations lies within an antibody-binding site, and therefore the mechanism of immune escape in both cases is by alteration of the shape of the envelope proteins. The conformation of the CD4-binding site is shown to be critical with regard to presentation of other discontinuous epitopes. From our analysis of the neutralization of these variants, we conclude that escape from polyclonal sera occurs through alterations at several different epitopes, generally resulting from single amino acid substitutions which influence envelope conformation. Experiments on a double mutant showed that the combination of both mutations is not additive, suggesting that these variants utilized alternate pathways to elicit similar alterations of the HIV-1 envelope structure.
Journal of General Virology, 1989
An important antigenic determinant of human immunodeficiency virus type 1 that induces neutralizing activity in infected humans and chimpanzees was previously mapped with nonapeptides between amino acids 307 and 320 on the external envelope glycoprotein (gp120) of strain HTLV-IIIB (molecular clone BH 10) and amino acids 320 to 330 of strain HTLV-IIIRF. Using different sera we found different reactive nonapeptides that overlapped and shared a tetrapeptide, GPGR. This tetrapeptide, which is the same in HTLV-IIIB and HTLV-IIIRF, is flanked by amino acids that vary between virus strains. Because GPGR is predicted to form a fl-turn and is flanked by two cysteine residues that may form a disulphide bridge, a hairpin-like structure is suggested for this part of gpl20. The tetrapeptide GPGR and the reactive peptides are located on top of this structure, well exposed to antibodies. We determined the role of the individual amino acids in antibody binding using three sets of peptide analogues derived from three reactive nonapeptides (two of strain HTLV-IIIB which overlapped and one of strain HTLV-IIIRF). Each set contained peptide analogues in which each amino acid was replaced, one at a time, by all genetically encoded amino acids. At least five consecutive amino acids in each nonapeptide were essential for antibody binding. They include amino acids of GPGR and potentially provide the virus with ample opportunity to escape immune surveillance.
Journal of Virology, 2008
The broadly neutralizing monoclonal antibody (MAb) 4E10 recognizes a linear epitope in the C terminus of the membrane-proximal external region (MPER) of gp41. This epitope is particularly attractive for vaccine design because it is highly conserved among human immunodeficiency virus type 1 (HIV-1) strains and neutralization escape in vivo has not been observed. Multiple env genes were cloned from an HIV-1 subtype C virus isolated from a 7-year-old perinatally infected child who had anti-MPER neutralizing antibodies. One clone (TM20.13) was resistant to 4E10 neutralization as a result of an F673L substitution in the MPER. Frequency analysis showed that F673L was present in 33% of the viral variants and in all cases was linked to the presence of an intact 2F5 epitope. Two other envelope clones were sensitive to 4E10 neutralization, but TM20.5 was 10-fold less sensitive than TM20.6. Substitutions at positions 674 and 677 within the MPER rendered TM20.5 more sensitive to 4E10 but had no...