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HIV-1 conserved elements p24CE DNA vaccine induces humoral immune responses with broad epitope recognition in macaques.

Kulkarni V, Valentin A, Rosati M, Rolland M, Mullins JI, Pavlakis GN, Felber BK - PLoS ONE (2014)

Bottom Line: In contrast, antibodies elicited by p55gag DNA vaccine failed to recognize p24CE protein and did not recognize linear epitopes spanning the CE.Interestingly, boosting of p24CE DNA primed animals with p55gag DNA resulted in augmentation of antibodies able to recognize p24gag as well as the p24CE proteins, thereby inducing broadest immunity.This novel and effective strategy to broaden responses could be applied against other antigens of highly diverse pathogens.

View Article: PubMed Central - PubMed

Affiliation: Human Retrovirus Pathogenesis Section, Vaccine Branch, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, Maryland, United States of America.

ABSTRACT
To target immune responses towards invariable regions of the virus, we engineered DNA-based immunogens encoding conserved elements (CE) of HIV-1 p24gag. This conserved element vaccine is designed to avoid decoy epitopes by focusing responses to critical viral elements. We previously reported that vaccination of macaques with p24CE DNA induced robust cellular immune responses to CE that were not elicited upon wild type p55gag DNA vaccination. p24CE DNA priming followed by p55gag DNA boost provided a novel strategy to increase the magnitude and breadth of the cellular immune responses to HIV-1 Gag, including the induction of strong, multifunctional T-cell responses targeting epitopes within CE. Here, we examined the humoral responses induced upon p24CE DNA or p55gag DNA vaccination in macaques and found that although both vaccines induced robust p24gag binding antibody responses, the responses induced by p24CE DNA showed a unique broad range of linear epitope recognition. In contrast, antibodies elicited by p55gag DNA vaccine failed to recognize p24CE protein and did not recognize linear epitopes spanning the CE. Interestingly, boosting of p24CE DNA primed animals with p55gag DNA resulted in augmentation of antibodies able to recognize p24gag as well as the p24CE proteins, thereby inducing broadest immunity. Our results indicate that an effectively directed vaccine strategy that includes priming with the conserved element vaccine followed by boost with the complete immunogen induces broad cellular and humoral immunity focused on the conserved regions of the virus. This novel and effective strategy to broaden responses could be applied against other antigens of highly diverse pathogens.

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Pepscan analysis of humoral responses induced upon p24CE and p55gag DNA vaccination in macaques.All macaques vaccinated with (A) p24CE DNA (N = 10) and (B) p55gag DNA (N = 4) were subjected to Pepscan analysis against 58 peptides (15-mers overlapping by 11 AA) spanning p24gag. Peptides corresponding to CE1 to CE7 are indicated and the peptides are listed below as detailed in Table 1. OD450 is reported after subtracting the mean OD450 of the values obtained from negative samples plus 3 SD.
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pone-0111085-g003: Pepscan analysis of humoral responses induced upon p24CE and p55gag DNA vaccination in macaques.All macaques vaccinated with (A) p24CE DNA (N = 10) and (B) p55gag DNA (N = 4) were subjected to Pepscan analysis against 58 peptides (15-mers overlapping by 11 AA) spanning p24gag. Peptides corresponding to CE1 to CE7 are indicated and the peptides are listed below as detailed in Table 1. OD450 is reported after subtracting the mean OD450 of the values obtained from negative samples plus 3 SD.

Mentions: To identify the linear epitopes recognized by the antibodies induced by the vaccination regimens, we performed a peptide scanning analysis (Pepscan) of plasma samples at the time of peak antibody responses (2 weeks after the 2nd vaccination) using a panel of peptides (15-mers overlapping by 11 AA) that cover the entire p24gag protein (see Table 1 for peptide sequences and association with CE). Data obtained with samples from macaques vaccinated with the p24CE DNA showed that each of the 10 animals developed antibodies that recognized CE1 and CE3 (Table 2). In addition, the number and locations of the peptides recognized suggest two distinct immunogenic epitopes within CE3. Three macaques (M166, R279 and P302) also developed responses to CE2, while two animals had responses to CE7 (L862, strong responses; P302, low responses) (Figure 3A). As expected, none of the macaques immunized with the p24CE recognized any peptide located outside the p24CE. In contrast, we found that the antibodies induced by p55gag DNA vaccination failed to efficiently recognize linear epitopes within the p24gag region (Figure 3B). Only one of the 4 animals (P574) had antibodies that recognized linear epitopes in CE1, CE3 and CE7, but we noted that different peptides were recognized compared to those in p24CE DNA vaccinated animals. Two macaques (P574 and R288) were able to recognize some peptides located in the ‘variable’ region between CE6 and CE7. These results demonstrate that vaccination with p24CE DNA triggered broad antibody responses that recognized several continuous epitopes within p24Gag, whereas vaccination with p55gag DNA failed to elicit antibodies against the linear segments in the conserved regions or in HIV-1 p24gag in general.


HIV-1 conserved elements p24CE DNA vaccine induces humoral immune responses with broad epitope recognition in macaques.

Kulkarni V, Valentin A, Rosati M, Rolland M, Mullins JI, Pavlakis GN, Felber BK - PLoS ONE (2014)

Pepscan analysis of humoral responses induced upon p24CE and p55gag DNA vaccination in macaques.All macaques vaccinated with (A) p24CE DNA (N = 10) and (B) p55gag DNA (N = 4) were subjected to Pepscan analysis against 58 peptides (15-mers overlapping by 11 AA) spanning p24gag. Peptides corresponding to CE1 to CE7 are indicated and the peptides are listed below as detailed in Table 1. OD450 is reported after subtracting the mean OD450 of the values obtained from negative samples plus 3 SD.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4206485&req=5

pone-0111085-g003: Pepscan analysis of humoral responses induced upon p24CE and p55gag DNA vaccination in macaques.All macaques vaccinated with (A) p24CE DNA (N = 10) and (B) p55gag DNA (N = 4) were subjected to Pepscan analysis against 58 peptides (15-mers overlapping by 11 AA) spanning p24gag. Peptides corresponding to CE1 to CE7 are indicated and the peptides are listed below as detailed in Table 1. OD450 is reported after subtracting the mean OD450 of the values obtained from negative samples plus 3 SD.
Mentions: To identify the linear epitopes recognized by the antibodies induced by the vaccination regimens, we performed a peptide scanning analysis (Pepscan) of plasma samples at the time of peak antibody responses (2 weeks after the 2nd vaccination) using a panel of peptides (15-mers overlapping by 11 AA) that cover the entire p24gag protein (see Table 1 for peptide sequences and association with CE). Data obtained with samples from macaques vaccinated with the p24CE DNA showed that each of the 10 animals developed antibodies that recognized CE1 and CE3 (Table 2). In addition, the number and locations of the peptides recognized suggest two distinct immunogenic epitopes within CE3. Three macaques (M166, R279 and P302) also developed responses to CE2, while two animals had responses to CE7 (L862, strong responses; P302, low responses) (Figure 3A). As expected, none of the macaques immunized with the p24CE recognized any peptide located outside the p24CE. In contrast, we found that the antibodies induced by p55gag DNA vaccination failed to efficiently recognize linear epitopes within the p24gag region (Figure 3B). Only one of the 4 animals (P574) had antibodies that recognized linear epitopes in CE1, CE3 and CE7, but we noted that different peptides were recognized compared to those in p24CE DNA vaccinated animals. Two macaques (P574 and R288) were able to recognize some peptides located in the ‘variable’ region between CE6 and CE7. These results demonstrate that vaccination with p24CE DNA triggered broad antibody responses that recognized several continuous epitopes within p24Gag, whereas vaccination with p55gag DNA failed to elicit antibodies against the linear segments in the conserved regions or in HIV-1 p24gag in general.

Bottom Line: In contrast, antibodies elicited by p55gag DNA vaccine failed to recognize p24CE protein and did not recognize linear epitopes spanning the CE.Interestingly, boosting of p24CE DNA primed animals with p55gag DNA resulted in augmentation of antibodies able to recognize p24gag as well as the p24CE proteins, thereby inducing broadest immunity.This novel and effective strategy to broaden responses could be applied against other antigens of highly diverse pathogens.

View Article: PubMed Central - PubMed

Affiliation: Human Retrovirus Pathogenesis Section, Vaccine Branch, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, Maryland, United States of America.

ABSTRACT
To target immune responses towards invariable regions of the virus, we engineered DNA-based immunogens encoding conserved elements (CE) of HIV-1 p24gag. This conserved element vaccine is designed to avoid decoy epitopes by focusing responses to critical viral elements. We previously reported that vaccination of macaques with p24CE DNA induced robust cellular immune responses to CE that were not elicited upon wild type p55gag DNA vaccination. p24CE DNA priming followed by p55gag DNA boost provided a novel strategy to increase the magnitude and breadth of the cellular immune responses to HIV-1 Gag, including the induction of strong, multifunctional T-cell responses targeting epitopes within CE. Here, we examined the humoral responses induced upon p24CE DNA or p55gag DNA vaccination in macaques and found that although both vaccines induced robust p24gag binding antibody responses, the responses induced by p24CE DNA showed a unique broad range of linear epitope recognition. In contrast, antibodies elicited by p55gag DNA vaccine failed to recognize p24CE protein and did not recognize linear epitopes spanning the CE. Interestingly, boosting of p24CE DNA primed animals with p55gag DNA resulted in augmentation of antibodies able to recognize p24gag as well as the p24CE proteins, thereby inducing broadest immunity. Our results indicate that an effectively directed vaccine strategy that includes priming with the conserved element vaccine followed by boost with the complete immunogen induces broad cellular and humoral immunity focused on the conserved regions of the virus. This novel and effective strategy to broaden responses could be applied against other antigens of highly diverse pathogens.

Show MeSH
Related in: MedlinePlus