Genetic and Neutralization Properties of Subtype C Human Immunodeficiency Virus Type 1 Molecular env Clones from Acute and Early Heterosexually Acquired Infections in Southern Africa

Abstract

A standard panel of subtype C human immunodeficiency virus type 1 (HIV-1) Env-pseudotyped viruses was created by cloning, sequencing, and characterizing functional gp160 genes from 18 acute and early heterosexually acquired infections in South Africa and Zambia. In general, the gp120 region of these clones was shorter (most evident in V1 and V4) and less glycosylated compared to newly transmitted subtype B viruses, and it was underglycosylated but no different in length compared to chronic subtype C viruses. The gp120s also exhibited low amino acid sequence variability (12%) in V3 and high variability (39%) immediately downstream of V3, a feature shared with newly transmitted subtype B viruses and chronic viruses of both subtypes. When tested as Env-pseudotyped viruses in a luciferase reporter gene assay, all clones possessed an R5 phenotype and resembled primary isolates in their sensitivity to neutralization by HIV-1-positive plasmas. Results obtained with a multisubtype plasma panel suggested partial subtype preference in the neutralizing antibody response to infection. The clones were typical of subtype C in that all were resistant to 2G12 (associated with loss of N-glycosylation at position 295) and most were resistant to 2F5, but all were sensitive to 4E10 and many were sensitive to immunoglobulin G1b12. Finally, conserved neutralization epitopes in the CD4-induced coreceptor binding domain of gp120 were poorly accessible and were difficult to induce and stabilize with soluble CD4 on Env-pseudotyped viruses. These results illustrate key genetic and antigenic properties of subtype C HIV-1 that might impact the design and testing of candidate vaccines. A subset of these gp160 clones are suitable for use as reference reagents to facilitate standardized assessments of vaccine-elicited neutralizing antibody responses.

Cross-subtype antibody and cellular immune responses induced by a polyvalent DNA prime–protein boost HIV-1 vaccine in healthy human volunteers

“…There were 6 pseudotyped HIV-1 viruses in the first panel (Tier-1) including MN and five homologous to the Env immunogens included in the DP6−001 formulation. There were 12 viruses in the second panel (Tier 2), 4 each from subtypes B (QH0692042, SC422661.8; PVO.4 and AC10.0.29), A (Q23.17, Q168.A2, Q461.E2 and Q769.D22), and C (Du123.6, Du151.2, Du156.12 and Du172.17) [32,33]. In this assay, 200 TCID 50 of virus was incubated with diluted serum samples in triplicate in a total volume of 150μl for 1 h at 37 °C in 96-well flat-bottom culture plates.…”

The Genetic Bottleneck in Vertical Transmission of Subtype C HIV-1 Is Not Driven by Selection of Especially Neutralization-Resistant Virus from the Maternal Viral Population

“…Correlations between HIV-1 transmission, variable loop length and number of putative N-linked glycosylation (PNG) sites encoded in the HIV env gene have been reported in some studies (9,10,33,58,59,60) but not in others (9,32,47). In horizontal transmission, acutely infected subjects were found to have shorter variable loops and fewer PNG sites encoded in env compared to subjects with chronic HIV-1 infection for subtypes A and C, but not subtype B (10,32,34).…”

“…Animal studies have demonstrated that neutralizing antibodies elicited by a simian immunodeficiency virus (SIV) vaccine can at least slow disease progression (56), while direct administration of antibodies matched to the chal-lenge virus can block transmission (16,44). Studies of natural MCTC have yielded conflicting results (2,3,7,20,26,31,32,48), although possibly for identifiable reasons. The breadth of the neutralizing antibody response may depend on the subtype of HIV-1 being studied (5,10), and neutralizing antibody levels may be associated with the timing of transmission (3).…”

“…In horizontal transmission, acutely infected subjects were found to have shorter variable loops and fewer PNG sites encoded in env compared to subjects with chronic HIV-1 infection for subtypes A and C, but not subtype B (10,32,34). In vertical transmission, one study of an HIV-1 subtype CRF_AE-infected cohort found no difference in sequence length or PNG sites, while in other studies analyzing multiple subtypes there were fewer PNG sites in transmitted viruses (47,59).…”

Llama Antibody Fragments with Cross-Subtype Human Immunodeficiency Virus Type 1 (HIV-1)-Neutralizing Properties and High Affinity for HIV-1 gp120

“…In this study, MAb b12 was tested in parallel to the VHH against a panel of 65 viruses and was able to neu- (43,44), which were included in this study. Neutralization data obtained in this study for MAb b12 against these reference panels are concordant with the data previously published.…”