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Effect of site-specific de-glycosylation on HIV gp120-specific CD4 T cell responses


Virus specific CD4+ T helper response is critical for maintenance of effective immunity against chronic viral infections. Vigorous HIV-specific T cell responses were found associated with control of viremia in HIV infected individuals. However, in most of the HIV infected individuals, virus specific CD4+ T cell responses are very low or undetectable. While the virus envelope is a critical target for the immune responses, this antigen is poorly immunogenic, especially for CD4+ T cells. One of the possible reasons is the heavy glycosylation of the envelope glycoproteins. In this study, we examined the effects of site-specific de-glycosylation on the presentation of gp120 antigen to the CD4+ T cells.

Materials and methods

Three potential N-linked glycosylation sites located in or flanking the CD4+ T cell epitope clusters in the C4 region of gp120 IIIB were disrupted by site-directed mutagenesis (N to Q) to generate mutants with single or multiple N-glycan deletions. Recombinant proteins were expressed in CHO cells, purified by affinity chromatography and analyzed for reactivity with soluble CD4 and various anti-gp120 mAbs in ELISA. The wild type and mutated proteins were then tested in 3H-thymidine incorporation assays for recognition by a mouse CD4+ T cell clone and a human CD4+ T cell line with specific C4 epitopes.


The reactivities of all of the mutated gp120 proteins to sCD4 and anti-gp120 mAbs were comparable to the wild type, suggesting that no major conformation changes occurred after removal of the specific glycan(s). However, the removal of one N-linked glycans at the C4 region decreased recognition of CD4+ T cells tested, while the deletion of the two other glycans had either slightly enhancing or no effects. Studies are on-going to assess what steps in antigen processing and presentation are affected by these N-glycan removals. In addition, the effects of these mutations on recognition of CD4 T cell specific for epitopes in other regions (C1, C2 and V3) of gp120 are being analyzed.


Removal of certain glycan(s) near a T cell epitope cluster of gp120 did not alter its reactivity with CD4 and mAbs, but could modulate the recognition of these epitopes by CD4 T cells.

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Open Access This article is published under license to BioMed Central Ltd. This is an Open Access article is distributed under the terms of the Creative Commons Attribution 2.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Li, H., Tuen, M., Cohen, S. et al. Effect of site-specific de-glycosylation on HIV gp120-specific CD4 T cell responses. Retrovirology 3 (Suppl 1), S34 (2006).

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