4E10-Resistant Variants in a Human Immunodeficiency Virus Type 1 Subtype C-Infected Individual with an Anti-Membrane-Proximal External Region-Neutralizing Antibody Response

Abstract

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 effect on TM20.6. Using chimeric and mutant constructs of these two variants, we further demonstrated that the lentivirus lytic peptide-2 domain in the cytoplasmic tail affected the accessibility of the 4E10 epitope, as well as virus infectivity. Collectively, these genetic changes in the face of a neutralizing antibody response to the MPER strongly suggested immune escape from antibody responses targeting this region.

Potent and Broad Neutralization of HIV-1 Subtype C by Plasma Antibodies Targeting a Quaternary Epitope Including Residues in the V2 Loop

“…The observation that CAP256 neutralization sensitivity is determined by the presence of crucial residues within the V2 epitope but also by the length of the adjacent V1 loop was not unexpected. Indeed, this is similar to 4E10, where the sensitivity of viruses containing the intact epitope in the MPER may be modulated by changes elsewhere in the envelope (13 (40), as well as affecting the sensitivity of heterologous viruses to such specificities. Unlike the V1 loop, which is likely to be structurally disordered and is very variable in length, the V2 loop contains a number of subdomains that are very conserved across all subtypes and shows a greater constraint on the minimum length tolerated (48).…”

Human Immunodeficiency Virus Type 2 (HIV-2)/HIV-1 Envelope Chimeras Detect High Titers of Broadly Reactive HIV-1 V3-Specific Antibodies in Human Plasma

“…2A). HIV-2 KR.X7 was less infectious than HIV-2 KR.X4 , although still within a range observed for primary HIV-2 and HIV-1 strains and previously described HIV-2/HIV-1 chimeras (18,34,49). The V3 chimeric viruses HIV-2 KR.X7 YU2 V3, HIV-2 KR.X7 Ccon V3, and HIV-2 KR.X7 MN V3 were infectious and again exhibited a broad range in infectivity compared with the isogenic HIV-2 KR.X7 scaffold and the HIV-2 KR.X4 parental strain.…”

“…Previously, we along with others have demonstrated that HIV-2 Env could be used as a scaffold to present HIV-1 MPER and CD4i epitopes in the context of a functional glycoprotein and that such viruses could serve as sensitive and specific probes for HIV-1-elicited epitope-specific NAbs (18,19,34,61,102 In the present study, we focused on HIV-1 V3, which continues to attract substantial attention as a target of NAbs (2,54,72,74,76,99,107). Mamounas and colleagues first demonstrated that a chimeric virus containing an HIV-2 backbone and an HIV-1 MN V3 loop was capable of infecting human T cells and showed susceptibility to HIV-1 V3-specific antiserum (64).…”

Closing the door to human immunodeficiency virus

“…Co-administration of 4E10 and 2F5 results in a synergistic neutralizing effect in vitro (Zwick et al, 2001b). To note, substitutions in the MPER contributed to the resistance to 4E10 (Gray et al, 2008;Nakamura et al, 2010). The safety and tolerability of 4E10 for clinical use have also been confirmed by a phase 2 clinical study (Joos et al, 2006).…”