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HIV-1 envelope resistance to proteasomal cleavage: implications for vaccine induced immune responses.

Steers NJ, Ratto-Kim S, de Souza MS, Currier JR, Kim JH, Michael NL, Alving CR, Rao M - PLoS ONE (2012)

Bottom Line: The processed antigen is then presented on the cell surface bound to either MHC class I or class II molecules and induces/interacts with antigen-specific CD8+ and CD4+ T-cells, respectively.Each of the cathepsins generated distinct degradation patterns containing regions of light and dense epitope clusters.The sequence DKKQKVHALF that is part of the V2 loop of gp120 produced by cathepsins induced a polyfunctional cytokine response including the generation of IFN-γ from CD4(+) T-cell lines-derived from RV144 vaccinees.

View Article: PubMed Central - PubMed

Affiliation: United States Military HIV Research Program, Walter Reed Army Institute of Research, Silver Spring, Maryland, United States of America.

ABSTRACT

Background: Antigen processing involves many proteolytic enzymes such as proteasomes and cathepsins. The processed antigen is then presented on the cell surface bound to either MHC class I or class II molecules and induces/interacts with antigen-specific CD8+ and CD4+ T-cells, respectively. Preliminary immunological data from the RV144 phase III trial indicated that the immune responses were biased towards the Env antigen with a dominant CD4+ T-cell response.

Methods: In this study, we examined the susceptibility of HIV-1 Env-A244 gp120 protein, one of the protein boost subunits of the RV144 Phase III vaccine trial, to proteasomes and cathepsins and identified the generated peptide epitope repertoire by mass spectrometry. The peptide fragments were tested for cytokine production in CD4(+) T-cell lines derived from RV144 volunteers.

Results: Env-A244 was resistant to proteasomes, thus diminishing the possibility of the generation of class I epitopes by the classical MHC class I pathway. However, Env-A244 was efficiently cleaved by cathepsins generating peptide arrays identified by mass spectrometry that contained both MHC class I and class II epitopes as reported in the Los Alamos database. Each of the cathepsins generated distinct degradation patterns containing regions of light and dense epitope clusters. The sequence DKKQKVHALF that is part of the V2 loop of gp120 produced by cathepsins induced a polyfunctional cytokine response including the generation of IFN-γ from CD4(+) T-cell lines-derived from RV144 vaccinees. This sequence is significant since antibodies to the V1/V2-loop region correlated inversely with HIV-1 infection in the RV144 trial.

Conclusions: Based on our results, the susceptibility of Env-A244 to cathepsins and not to proteasomes suggests a possible mechanism for the generation of Env-specific CD4(+)T cell and antibody responses in the RV144 vaccinees.

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Related in: MedlinePlus

Kyte-Doolittle plot of HIV-1 Env-A244 in relation to peptide clusters.Hydrophobicity/hydrophilicity plots of HIV-1 Env-A244 (panel A) were generated with the Kyte-Doolittle algorithm (http://mobyle.pasteur.fr/cgi-bin/portal.py?form=pepwindowall). All the peptide fragments identified by mass spectrometry (Figure 3 A) are denoted by blue boxes (panel B). Red boxes represent the reported CD8+ T-cell epitopes and the green boxes represent the reported CD4+ T-cell epitopes (panel C). The constant and variable regions of Env-A244 are denoted in panel D. The greater the number of epitopes in each of the clusters, the greater is the height of the box.
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pone-0042579-g005: Kyte-Doolittle plot of HIV-1 Env-A244 in relation to peptide clusters.Hydrophobicity/hydrophilicity plots of HIV-1 Env-A244 (panel A) were generated with the Kyte-Doolittle algorithm (http://mobyle.pasteur.fr/cgi-bin/portal.py?form=pepwindowall). All the peptide fragments identified by mass spectrometry (Figure 3 A) are denoted by blue boxes (panel B). Red boxes represent the reported CD8+ T-cell epitopes and the green boxes represent the reported CD4+ T-cell epitopes (panel C). The constant and variable regions of Env-A244 are denoted in panel D. The greater the number of epitopes in each of the clusters, the greater is the height of the box.

Mentions: The peptides generated from either the CAT degradation or the CAT followed by proteasomal degradation indicated that Env-A244 had regions of high and low epitope clusters. A Kyte-Doolittle hydrophobicity plot [37] was constructed for Env-A244 and although epitopes were generated throughout the length of the antigen, the high-density epitope clusters were observed in the hydrophobic regions of C2, V3, and C3 regions of Env-A244 (Figure 5). High-density epitope clusters were also observed in the C1 region of Env-A244, however these clusters were not in the highly hydrophobic region and epitope clusters were sparse in the hydrophilic region of the protein. In the Los Alamos database, few functional Env-A244 MHC class I and class II epitopes have been reported within the Env-A244 sequence. However, the majority of epitopes are clustered in the hydrophobic regions. Similar results were obtained with clade B gp140 protein (data not shown).


HIV-1 envelope resistance to proteasomal cleavage: implications for vaccine induced immune responses.

Steers NJ, Ratto-Kim S, de Souza MS, Currier JR, Kim JH, Michael NL, Alving CR, Rao M - PLoS ONE (2012)

Kyte-Doolittle plot of HIV-1 Env-A244 in relation to peptide clusters.Hydrophobicity/hydrophilicity plots of HIV-1 Env-A244 (panel A) were generated with the Kyte-Doolittle algorithm (http://mobyle.pasteur.fr/cgi-bin/portal.py?form=pepwindowall). All the peptide fragments identified by mass spectrometry (Figure 3 A) are denoted by blue boxes (panel B). Red boxes represent the reported CD8+ T-cell epitopes and the green boxes represent the reported CD4+ T-cell epitopes (panel C). The constant and variable regions of Env-A244 are denoted in panel D. The greater the number of epitopes in each of the clusters, the greater is the height of the box.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3412807&req=5

pone-0042579-g005: Kyte-Doolittle plot of HIV-1 Env-A244 in relation to peptide clusters.Hydrophobicity/hydrophilicity plots of HIV-1 Env-A244 (panel A) were generated with the Kyte-Doolittle algorithm (http://mobyle.pasteur.fr/cgi-bin/portal.py?form=pepwindowall). All the peptide fragments identified by mass spectrometry (Figure 3 A) are denoted by blue boxes (panel B). Red boxes represent the reported CD8+ T-cell epitopes and the green boxes represent the reported CD4+ T-cell epitopes (panel C). The constant and variable regions of Env-A244 are denoted in panel D. The greater the number of epitopes in each of the clusters, the greater is the height of the box.
Mentions: The peptides generated from either the CAT degradation or the CAT followed by proteasomal degradation indicated that Env-A244 had regions of high and low epitope clusters. A Kyte-Doolittle hydrophobicity plot [37] was constructed for Env-A244 and although epitopes were generated throughout the length of the antigen, the high-density epitope clusters were observed in the hydrophobic regions of C2, V3, and C3 regions of Env-A244 (Figure 5). High-density epitope clusters were also observed in the C1 region of Env-A244, however these clusters were not in the highly hydrophobic region and epitope clusters were sparse in the hydrophilic region of the protein. In the Los Alamos database, few functional Env-A244 MHC class I and class II epitopes have been reported within the Env-A244 sequence. However, the majority of epitopes are clustered in the hydrophobic regions. Similar results were obtained with clade B gp140 protein (data not shown).

Bottom Line: The processed antigen is then presented on the cell surface bound to either MHC class I or class II molecules and induces/interacts with antigen-specific CD8+ and CD4+ T-cells, respectively.Each of the cathepsins generated distinct degradation patterns containing regions of light and dense epitope clusters.The sequence DKKQKVHALF that is part of the V2 loop of gp120 produced by cathepsins induced a polyfunctional cytokine response including the generation of IFN-γ from CD4(+) T-cell lines-derived from RV144 vaccinees.

View Article: PubMed Central - PubMed

Affiliation: United States Military HIV Research Program, Walter Reed Army Institute of Research, Silver Spring, Maryland, United States of America.

ABSTRACT

Background: Antigen processing involves many proteolytic enzymes such as proteasomes and cathepsins. The processed antigen is then presented on the cell surface bound to either MHC class I or class II molecules and induces/interacts with antigen-specific CD8+ and CD4+ T-cells, respectively. Preliminary immunological data from the RV144 phase III trial indicated that the immune responses were biased towards the Env antigen with a dominant CD4+ T-cell response.

Methods: In this study, we examined the susceptibility of HIV-1 Env-A244 gp120 protein, one of the protein boost subunits of the RV144 Phase III vaccine trial, to proteasomes and cathepsins and identified the generated peptide epitope repertoire by mass spectrometry. The peptide fragments were tested for cytokine production in CD4(+) T-cell lines derived from RV144 volunteers.

Results: Env-A244 was resistant to proteasomes, thus diminishing the possibility of the generation of class I epitopes by the classical MHC class I pathway. However, Env-A244 was efficiently cleaved by cathepsins generating peptide arrays identified by mass spectrometry that contained both MHC class I and class II epitopes as reported in the Los Alamos database. Each of the cathepsins generated distinct degradation patterns containing regions of light and dense epitope clusters. The sequence DKKQKVHALF that is part of the V2 loop of gp120 produced by cathepsins induced a polyfunctional cytokine response including the generation of IFN-γ from CD4(+) T-cell lines-derived from RV144 vaccinees. This sequence is significant since antibodies to the V1/V2-loop region correlated inversely with HIV-1 infection in the RV144 trial.

Conclusions: Based on our results, the susceptibility of Env-A244 to cathepsins and not to proteasomes suggests a possible mechanism for the generation of Env-specific CD4(+)T cell and antibody responses in the RV144 vaccinees.

Show MeSH
Related in: MedlinePlus