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Updated: Jul 14, 2026
Conformational Evaluation of HIV-1 Trimeric Envelope Glycoproteins Using a Cell-based ELISA Assay
Published on: September 14, 2014
Conserved changes in envelope function during human immunodeficiency virus type 1 coreceptor switching
Cristina Pastore1, Rebecca Nedellec, Alejandra Ramos
1Department of Immunology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
Abstract:
We studied the evolution of human immunodeficiency virus type 1 (HIV-1) envelope function during the process of coreceptor switching from CCR5 to CXCR4. Site-directed mutagenesis was used to introduce most of the possible intermediate mutations in the envelope for four distinct coreceptor switch mutants, each with a unique pattern of CCR5 and CXCR4 utilization that extended from highly efficient use of both coreceptors to sole use of CXCR4. Mutated envelopes with some preservation of entry function on either CCR5- or CXCR4-expressing target cells were further characterized for their sensitivity to CCR5 or CXCR4 inhibitors, soluble CD4, and the neutralizing antibodies b12-IgG and 4E10. A subset of mutated envelopes was also studied in direct CD4 or CCR5 binding assays and in envelope-mediated fusion reactions. Coreceptor switch intermediates displayed increased sensitivity to CCR5 inhibitors (except for a few envelopes with mutations in V2 or C2) that correlated with a loss in CCR5 binding. As use of CXCR4 improved, infection mediated by the mutated envelopes became more resistant to soluble CD4 inhibition and direct binding to CD4 increased. These changes were accompanied by increasing resistance to the CXCR4 inhibitor AMD3100. Sensitivity to neutralizing antibody was more variable, although infection of CXCR4-expressing targets was generally more sensitive to neutralization by both b12-IgG and 4E10 than infection of CCR5-expressing target cells. These changes in envelope function were uniform in all four series of envelope mutations and thus were independent of the final use of CCR5 and CXCR4. Decreased CCR5 and increased CD4 binding appear to be common features of coreceptor switch intermediates.
Insights
Understanding human immunodeficiency virus type 1 (HIV-1) coreceptor switching reveals key envelope changes. HIV-1 envelope mutations during CCR5 to CXCR4 switching show decreased CCR5 and increased CD4 binding, impacting inhibitor sensitivity.
Area of Science:
- Virology
- Immunology
- Molecular Biology
Background:
- Human immunodeficiency virus type 1 (HIV-1) entry into host cells relies on the envelope (Env) glycoprotein binding to CD4 and a coreceptor, either CCR5 or CXCR4.
- Coreceptor tropism switching, from CCR5 (R5) to CXCR4 (X4), is a critical step in HIV-1 pathogenesis and influences viral tropism and therapeutic responses.
Purpose of the Study:
- To investigate the functional and binding alterations of the HIV-1 envelope during the transition from CCR5 to CXCR4 coreceptor utilization.
- To characterize intermediate envelope mutants for their sensitivity to entry inhibitors and neutralizing antibodies.
Main Methods:
- Site-directed mutagenesis was employed to generate four distinct series of HIV-1 envelope mutants mimicking coreceptor switch intermediates.
- Mutant envelopes were assessed for their utilization of CCR5 and CXCR4, sensitivity to CCR5/CXCR4 inhibitors (e.g., AMD3100), soluble CD4, and neutralizing antibodies (b12-IgG, 4E10).
- Binding assays (CD4, CCR5) and fusion assays were performed on a subset of mutants.
Main Results:
- Coreceptor switch intermediates exhibited increased sensitivity to CCR5 inhibitors, correlating with reduced CCR5 binding.
- As CXCR4 utilization increased, mutants showed enhanced resistance to soluble CD4 inhibition and increased CD4 binding.
- Mutants displayed increasing resistance to the CXCR4 inhibitor AMD3100, with variable sensitivity to neutralizing antibodies.
- Functional changes were consistent across all mutant series, irrespective of the final coreceptor preference.
Conclusions:
- Decreased CCR5 binding and increased CD4 binding are common characteristics of HIV-1 envelope intermediates during coreceptor switching.
- These envelope modifications during the CCR5-to-CXCR4 switch influence viral sensitivity to entry inhibitors and neutralizing antibodies.
- Understanding these evolutionary changes provides insights into HIV-1 tropism and potential therapeutic strategies.
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