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Design and pre-clinical evaluation of a universal HIV-1 vaccine.

Létourneau S, Im EJ, Mashishi T, Brereton C, Bridgeman A, Yang H, Dorrell L, Dong T, Korber B, McMichael AJ, Hanke T - PLoS ONE (2007)

Bottom Line: Each segment is a consensus sequence from one of the four major HIV-1 clades A, B, C and D, which alternate to ensure equal clade coverage.We also demonstrated that these conserved regions prime CD8(+) and CD4(+) T cell to highly conserved epitopes in humans and that these epitopes, although usually subdominant, generate memory T cells in patients during natural HIV-1 infection.Furthermore, this approach has merit in the simplicity of design and delivery, requiring only a single immunogen to provide extensive coverage of global HIV-1 population diversity.

View Article: PubMed Central - PubMed

Affiliation: Medical Research Council Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe, Oxford, United Kingdom.

ABSTRACT

Background: One of the big roadblocks in development of HIV-1/AIDS vaccines is the enormous diversity of HIV-1, which could limit the value of any HIV-1 vaccine candidate currently under test.

Methodology and findings: To address the HIV-1 variation, we designed a novel T cell immunogen, designated HIV(CONSV), by assembling the 14 most conserved regions of the HIV-1 proteome into one chimaeric protein. Each segment is a consensus sequence from one of the four major HIV-1 clades A, B, C and D, which alternate to ensure equal clade coverage. The gene coding for the HIV(CONSV) protein was inserted into the three most studied vaccine vectors, plasmid DNA, human adenovirus serotype 5 and modified vaccine virus Ankara (MVA), and induced HIV-1-specific T cell responses in mice. We also demonstrated that these conserved regions prime CD8(+) and CD4(+) T cell to highly conserved epitopes in humans and that these epitopes, although usually subdominant, generate memory T cells in patients during natural HIV-1 infection.

Significance: Therefore, this vaccine approach provides an attractive and testable alternative for overcoming the HIV-1 variability, while focusing T cell responses on regions of the virus that are less likely to mutate and escape. Furthermore, this approach has merit in the simplicity of design and delivery, requiring only a single immunogen to provide extensive coverage of global HIV-1 population diversity.

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Breadth of HIVCONSV-induced T cell responses in BALB/c mice.Mice were immunized using the regimen and immunogen indicated above (A, B and C) or below (D) the graphs and the HIVCONSV-specific responses were determined in ex vivo ELISPOT (A and E) or ICS (B and D) assays detecting the indicated cytokines and using for restimulation overlapping peptide pools schematically shown in Fig. 1D (A and B) or individual epitope peptides (D and E). (C) Identified peptides or epitope sequences and their origin, name and T cell reactivity. In (D): white–IFN-γ; black–IL-2; stripy-IFN-γ+IL-2; and grey–TNF-α; *-responses significantly above the no-peptide background (p<0.05). In (E): white–no peptide followed from left to right by epitopes H, G1, G2, P1, P2 and P3. Results are shown as a mean±SD (n = 4). For doses and timing, see Methods.
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pone-0000984-g003: Breadth of HIVCONSV-induced T cell responses in BALB/c mice.Mice were immunized using the regimen and immunogen indicated above (A, B and C) or below (D) the graphs and the HIVCONSV-specific responses were determined in ex vivo ELISPOT (A and E) or ICS (B and D) assays detecting the indicated cytokines and using for restimulation overlapping peptide pools schematically shown in Fig. 1D (A and B) or individual epitope peptides (D and E). (C) Identified peptides or epitope sequences and their origin, name and T cell reactivity. In (D): white–IFN-γ; black–IL-2; stripy-IFN-γ+IL-2; and grey–TNF-α; *-responses significantly above the no-peptide background (p<0.05). In (E): white–no peptide followed from left to right by epitopes H, G1, G2, P1, P2 and P3. Results are shown as a mean±SD (n = 4). For doses and timing, see Methods.

Mentions: The HIVCONSV chimaeric protein is not a natural protein, and the new context resulting from concatenating the fragments may impact the processing of intact epitopes that are embedded within the fragments. It was therefore important to demonstrate that HIVCONSV can induce T cell responses in mice and that epitopes recognized by human HLA-restricted T cells can be generated. We noted, as previously, that the response to the added H epitope dominated the T cell response in BALB/c mice (Fig. 3A). To avoid the H epitope domination of the T cell responses in the BALB/c mice[18], [53], vaccines expressing HIVCONSVdH immunogen with the H epitope deleted were constructed. Groups of BALB/c mice were immunized using the two strongest heterologous regimens from the previous experiment and the breadth of induced T cells was assessed using six pools of 32 peptides (15-mer overlapping by 11 amino-acid residues) corresponding to the whole HIVCONSV protein (Fig. 1D). While weak responses were observed following the DM regimen, higher frequencies of T cells recognizing at least 5 peptide pools were elicited by the DAM regimen (Fig. 3A, left and middle panels). In both instances, responses to pools 1–4 were dominated by the H epitope in pool 6 and were much stronger when the HIVCONSVdH immunogen was used (Fig. 3A, right panel). Next, we showed that the DM regimen of the HIVCONSVdH vaccines induced both CD8+ and CD4+ T cells, which could produce IFN-γ and IL-2 in response to antigenic stimuli (Fig. 3B). Following identification of the individual pool peptides, minimal previously identified peptides were confirmed for some responses minimal epitopes[53] (Fig. 3C). Further analysis demonstrated elicitation of high quality T cells capable of production of IFN-γ, IL-2 and TNF-α (Fig. 3D) and killing of targets sensitized with MHC class I-restricted peptides (not shown). Finally, using the HIVCONSV vaccines and the one CD4+ and five CD8+ T-cell epitopes, various dual and triple heterologous regimens were directly compared. This indicated that at the doses used, triple schedules were more immunogenic than the dual ones and indicated the superiority of DAM (Fig. 3E).


Design and pre-clinical evaluation of a universal HIV-1 vaccine.

Létourneau S, Im EJ, Mashishi T, Brereton C, Bridgeman A, Yang H, Dorrell L, Dong T, Korber B, McMichael AJ, Hanke T - PLoS ONE (2007)

Breadth of HIVCONSV-induced T cell responses in BALB/c mice.Mice were immunized using the regimen and immunogen indicated above (A, B and C) or below (D) the graphs and the HIVCONSV-specific responses were determined in ex vivo ELISPOT (A and E) or ICS (B and D) assays detecting the indicated cytokines and using for restimulation overlapping peptide pools schematically shown in Fig. 1D (A and B) or individual epitope peptides (D and E). (C) Identified peptides or epitope sequences and their origin, name and T cell reactivity. In (D): white–IFN-γ; black–IL-2; stripy-IFN-γ+IL-2; and grey–TNF-α; *-responses significantly above the no-peptide background (p<0.05). In (E): white–no peptide followed from left to right by epitopes H, G1, G2, P1, P2 and P3. Results are shown as a mean±SD (n = 4). For doses and timing, see Methods.
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Related In: Results  -  Collection

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pone-0000984-g003: Breadth of HIVCONSV-induced T cell responses in BALB/c mice.Mice were immunized using the regimen and immunogen indicated above (A, B and C) or below (D) the graphs and the HIVCONSV-specific responses were determined in ex vivo ELISPOT (A and E) or ICS (B and D) assays detecting the indicated cytokines and using for restimulation overlapping peptide pools schematically shown in Fig. 1D (A and B) or individual epitope peptides (D and E). (C) Identified peptides or epitope sequences and their origin, name and T cell reactivity. In (D): white–IFN-γ; black–IL-2; stripy-IFN-γ+IL-2; and grey–TNF-α; *-responses significantly above the no-peptide background (p<0.05). In (E): white–no peptide followed from left to right by epitopes H, G1, G2, P1, P2 and P3. Results are shown as a mean±SD (n = 4). For doses and timing, see Methods.
Mentions: The HIVCONSV chimaeric protein is not a natural protein, and the new context resulting from concatenating the fragments may impact the processing of intact epitopes that are embedded within the fragments. It was therefore important to demonstrate that HIVCONSV can induce T cell responses in mice and that epitopes recognized by human HLA-restricted T cells can be generated. We noted, as previously, that the response to the added H epitope dominated the T cell response in BALB/c mice (Fig. 3A). To avoid the H epitope domination of the T cell responses in the BALB/c mice[18], [53], vaccines expressing HIVCONSVdH immunogen with the H epitope deleted were constructed. Groups of BALB/c mice were immunized using the two strongest heterologous regimens from the previous experiment and the breadth of induced T cells was assessed using six pools of 32 peptides (15-mer overlapping by 11 amino-acid residues) corresponding to the whole HIVCONSV protein (Fig. 1D). While weak responses were observed following the DM regimen, higher frequencies of T cells recognizing at least 5 peptide pools were elicited by the DAM regimen (Fig. 3A, left and middle panels). In both instances, responses to pools 1–4 were dominated by the H epitope in pool 6 and were much stronger when the HIVCONSVdH immunogen was used (Fig. 3A, right panel). Next, we showed that the DM regimen of the HIVCONSVdH vaccines induced both CD8+ and CD4+ T cells, which could produce IFN-γ and IL-2 in response to antigenic stimuli (Fig. 3B). Following identification of the individual pool peptides, minimal previously identified peptides were confirmed for some responses minimal epitopes[53] (Fig. 3C). Further analysis demonstrated elicitation of high quality T cells capable of production of IFN-γ, IL-2 and TNF-α (Fig. 3D) and killing of targets sensitized with MHC class I-restricted peptides (not shown). Finally, using the HIVCONSV vaccines and the one CD4+ and five CD8+ T-cell epitopes, various dual and triple heterologous regimens were directly compared. This indicated that at the doses used, triple schedules were more immunogenic than the dual ones and indicated the superiority of DAM (Fig. 3E).

Bottom Line: Each segment is a consensus sequence from one of the four major HIV-1 clades A, B, C and D, which alternate to ensure equal clade coverage.We also demonstrated that these conserved regions prime CD8(+) and CD4(+) T cell to highly conserved epitopes in humans and that these epitopes, although usually subdominant, generate memory T cells in patients during natural HIV-1 infection.Furthermore, this approach has merit in the simplicity of design and delivery, requiring only a single immunogen to provide extensive coverage of global HIV-1 population diversity.

View Article: PubMed Central - PubMed

Affiliation: Medical Research Council Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe, Oxford, United Kingdom.

ABSTRACT

Background: One of the big roadblocks in development of HIV-1/AIDS vaccines is the enormous diversity of HIV-1, which could limit the value of any HIV-1 vaccine candidate currently under test.

Methodology and findings: To address the HIV-1 variation, we designed a novel T cell immunogen, designated HIV(CONSV), by assembling the 14 most conserved regions of the HIV-1 proteome into one chimaeric protein. Each segment is a consensus sequence from one of the four major HIV-1 clades A, B, C and D, which alternate to ensure equal clade coverage. The gene coding for the HIV(CONSV) protein was inserted into the three most studied vaccine vectors, plasmid DNA, human adenovirus serotype 5 and modified vaccine virus Ankara (MVA), and induced HIV-1-specific T cell responses in mice. We also demonstrated that these conserved regions prime CD8(+) and CD4(+) T cell to highly conserved epitopes in humans and that these epitopes, although usually subdominant, generate memory T cells in patients during natural HIV-1 infection.

Significance: Therefore, this vaccine approach provides an attractive and testable alternative for overcoming the HIV-1 variability, while focusing T cell responses on regions of the virus that are less likely to mutate and escape. Furthermore, this approach has merit in the simplicity of design and delivery, requiring only a single immunogen to provide extensive coverage of global HIV-1 population diversity.

Show MeSH
Related in: MedlinePlus