Syncytium-Inducing and Non-Syncytium-Inducing Capacity of Human Immunodeficiency Virus Type 1 Subtypes Other Than B: Phenotypic and Genotypic Characteristics

Abstract

Positively charged amino acid substitutions at positions 11 and 25 within the loop of the third variable region (V3) of HIV-1 subtype B envelope have been shown to be associated with the syncytium-inducing (SI) phenotype of the virus. The present study was designed to examine SI and NSI-associated V3 mutations in HIV-1 subtypes other than B. HIV-1 RNA was isolated from 53 virus stocks and 26 homologous plasma samples from 53 recently infected individuals from Brazil, Rwanda, Thailand, and Uganda. The C2-V3 region of the viral envelope was converted to cDNA, amplified, and sequenced. Of 53 primary virus stock samples 49 were biologically phenotyped through measurement of the syncytium-inducing capacity in MT-2 cells (to differentiate between SI and NSI phenotypes). In addition, after passage of primary isolates through PHA stimulated donor PBMC, the replication capacity was determined in U937-2, CEM, MT-2, and Jurkat-tat cell lines (to differentiate rapid/high and slow/low phenotypes). According to the sequence analysis 9 (17.0%) of the viruses belonged to subtype A, 15 (28.3%) to subtype B, 1 (1.9%) to subtype C, 13 (24.5%) to subtype D, and 15 (28.3%) to subtype E. Sequence analysis of virus RNA, obtained from 26 homologous plasma samples, confirmed the homogeneity of sequence populations in plasma compared to primary virus isolates. Of the 49 viruses tested 12 had the SI phenotype, 5 were confirmed to be rapid/high, and 4 appeared to be slow/low pattern 3 replicating. Of 49, 29 had the NSI phenotype, 24 were confirmed to be slow/low pattern 1 or 2, and 3 appeared to be slow/low pattern 3 replicating. Analysis of mutations at V3 loop amino acid positions 11 and 25 revealed that 10/12 (83.3%) of the SI viruses had SI-associated V3 mutations and that 28/29 (96.6%) of the NSI viruses lacked these mutations. V3 loop heterogeneity, length polymorphism, and a high number of positively charged amino acid substitutions were most frequently found among subtype D variants. These results indicate that both the phenotypic distinction between SI and NSI viruses and the association of biological phenotype with V3 mutations is present among HIV-1 subtypes other than B.

N-Linked Glycosylation of the HIV Type-1 gp120 Envelope Glycoprotein as a Major Determinant of CCR5 and CXCR4 Coreceptor Utilization

“…In accordance, HIV-1 subtypes D and E demonstrate the highest frequency of V3 de-glycosylation, even at the lower V3 charges, and both these subtypes reportedly have a high frequency of SI viruses among infected individuals (71,72). It will be interesting to address why subtype C viruses keep a low charge in the V3 region, whereas rates of disease progression do not appear to be different nor do the viral loads seem to be lower than for the other subtypes (70).…”

Isolation of CD4-Independent Primary Human Immunodeficiency Virus Type 1 Isolates That Are Syncytium Inducing and Acutely Cytopathic for CD8+Lymphocytes

“…As listed by the ARRP, the 12 primary viruses that we tested were originally obtained from patients in North America, Africa, and Asia and contained R5-, X4-, or dual (R5X4)-tropic isolates of clades A, B, D, and E (Table 1). Some of these patients have been studied extensively by different groups over the years (3,4,7,11,23,24,37). Infection and isolation of CD4-independent viruses were performed by using a previously described technique (31).…”

“…The sequences were analyzed by a comprehensive VESPA analysis (20). The CD4-tropic env sequences from some of these patients are also available in the HIV sequence database and from previous studies (3,4,7,11,23,24,37).…”

Intranasal HIV-1-gp160-DNA/gp41 Peptide Prime-Boost Immunization Regimen in Mice Results in Long-Term HIV-1 Neutralizing Humoral Mucosal and Systemic Immunity

“…Considering that experimental approaches inducing longterm mucosal immune responses may be necessary, we evaluated the immunogenicity of a peptide representing the gp41 coiled-coil pocket region in mice. We also evaluated whether these immune responses can be enhanced by combining HIV-1 rgp160/Rev DNA, CCR5 DNA, and CCR5 peptides with other well-conserved gp41 epitopes of the envelope from HIV-1 clades A, B, C, and D (24). A spectrum of specific epitopes from subtypes A-D provides both broad HIV-1 clade immunity combined with autoantibodies against the prominent coreceptor CCR5.…”