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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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Induction of humoral immune responses upon p24CE DNA vaccination in macaques.(A) Cartoon depicts the vaccination schedule. Each macaque received 2 vaccinations with a mixture of p24CE1 and p24CE2 DNAs or p55gag DNA at week 0 and 8. Plasma samples were analyzed for bAb to Gag at the time of each vaccination and at the additional indicated time points. (B) Plasma bAb to HIV-1 p24Gag measured by ELISA. Mean and standard error of the reciprocal Gag antibody endpoint titers (in log10) of 10 macaques vaccinated with p24CE DNA mixture and 4 macaques which received the p55gag DNA are shown. (C, D) Western immunoblot analysis was used to identify binding antibodies to HIV-1 p24Gag and the p24CE proteins present in plasma collected after the last vaccination. The membranes contain the soluble processed clade B p24gag protein (lane 1), p24CE1 (lane 2) and p24CE2 (lane 3) protein and were probed with plasma collected after the last vaccination. The data from 2 representative macaques from each vaccine group are shown: (C) p24CE DNA vaccinated animals M437 (plasma dilution 1:2000) and P314 (plasma dilution 1:1000) and (D) p55gag DNA vaccinated animals M114 and M121 (plasma dilution 1:2000 for both). The positions of p24gag and p24CE proteins are indicated.
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pone-0111085-g002: Induction of humoral immune responses upon p24CE DNA vaccination in macaques.(A) Cartoon depicts the vaccination schedule. Each macaque received 2 vaccinations with a mixture of p24CE1 and p24CE2 DNAs or p55gag DNA at week 0 and 8. Plasma samples were analyzed for bAb to Gag at the time of each vaccination and at the additional indicated time points. (B) Plasma bAb to HIV-1 p24Gag measured by ELISA. Mean and standard error of the reciprocal Gag antibody endpoint titers (in log10) of 10 macaques vaccinated with p24CE DNA mixture and 4 macaques which received the p55gag DNA are shown. (C, D) Western immunoblot analysis was used to identify binding antibodies to HIV-1 p24Gag and the p24CE proteins present in plasma collected after the last vaccination. The membranes contain the soluble processed clade B p24gag protein (lane 1), p24CE1 (lane 2) and p24CE2 (lane 3) protein and were probed with plasma collected after the last vaccination. The data from 2 representative macaques from each vaccine group are shown: (C) p24CE DNA vaccinated animals M437 (plasma dilution 1:2000) and P314 (plasma dilution 1:1000) and (D) p55gag DNA vaccinated animals M114 and M121 (plasma dilution 1:2000 for both). The positions of p24gag and p24CE proteins are indicated.

Mentions: Rhesus macaques received two vaccinations with DNAs expressing either both p24CE1 and p24CE2 (N = 10) or p55gag (N = 4), each delivered by intramuscular injection followed by in vivo electroporation as outlined in Figure 2A and previously reported [18], [19]. Plasma samples were collected on the day of vaccination and 2 and 8 weeks later. We have previously reported that vaccination with p24CE DNA induced strong cellular immunity targeting new epitopes [18], [19]. Here, we examined the development of Gag-specific humoral responses induced by the same immunization regimen. Animals vaccinated with p24CE DNA developed antibody responses against p24gag and the kinetics of these responses were similar to those induced by p55gag DNA vaccination (Figure 2B). p24gag antibody responses were detectable upon a single DNA vaccination, and were efficiently boosted by the 2nd DNA immunization resulting in peak antibody titers (∼5.3 log reciprocal end-point dilution) detected 2 weeks later. Similar levels of Gag-specific antibody responses were detected 8 weeks later in both groups of animals, indicating comparable persistence of humoral responses. These results demonstrate that p24CE DNA, an immunogen designed to elicit optimal T-cell responses, is able to induce humoral immune responses to p24gag of similar magnitude as those induced by the p55gag DNA vaccine.


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)

Induction of humoral immune responses upon p24CE DNA vaccination in macaques.(A) Cartoon depicts the vaccination schedule. Each macaque received 2 vaccinations with a mixture of p24CE1 and p24CE2 DNAs or p55gag DNA at week 0 and 8. Plasma samples were analyzed for bAb to Gag at the time of each vaccination and at the additional indicated time points. (B) Plasma bAb to HIV-1 p24Gag measured by ELISA. Mean and standard error of the reciprocal Gag antibody endpoint titers (in log10) of 10 macaques vaccinated with p24CE DNA mixture and 4 macaques which received the p55gag DNA are shown. (C, D) Western immunoblot analysis was used to identify binding antibodies to HIV-1 p24Gag and the p24CE proteins present in plasma collected after the last vaccination. The membranes contain the soluble processed clade B p24gag protein (lane 1), p24CE1 (lane 2) and p24CE2 (lane 3) protein and were probed with plasma collected after the last vaccination. The data from 2 representative macaques from each vaccine group are shown: (C) p24CE DNA vaccinated animals M437 (plasma dilution 1:2000) and P314 (plasma dilution 1:1000) and (D) p55gag DNA vaccinated animals M114 and M121 (plasma dilution 1:2000 for both). The positions of p24gag and p24CE proteins are indicated.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4206485&req=5

pone-0111085-g002: Induction of humoral immune responses upon p24CE DNA vaccination in macaques.(A) Cartoon depicts the vaccination schedule. Each macaque received 2 vaccinations with a mixture of p24CE1 and p24CE2 DNAs or p55gag DNA at week 0 and 8. Plasma samples were analyzed for bAb to Gag at the time of each vaccination and at the additional indicated time points. (B) Plasma bAb to HIV-1 p24Gag measured by ELISA. Mean and standard error of the reciprocal Gag antibody endpoint titers (in log10) of 10 macaques vaccinated with p24CE DNA mixture and 4 macaques which received the p55gag DNA are shown. (C, D) Western immunoblot analysis was used to identify binding antibodies to HIV-1 p24Gag and the p24CE proteins present in plasma collected after the last vaccination. The membranes contain the soluble processed clade B p24gag protein (lane 1), p24CE1 (lane 2) and p24CE2 (lane 3) protein and were probed with plasma collected after the last vaccination. The data from 2 representative macaques from each vaccine group are shown: (C) p24CE DNA vaccinated animals M437 (plasma dilution 1:2000) and P314 (plasma dilution 1:1000) and (D) p55gag DNA vaccinated animals M114 and M121 (plasma dilution 1:2000 for both). The positions of p24gag and p24CE proteins are indicated.
Mentions: Rhesus macaques received two vaccinations with DNAs expressing either both p24CE1 and p24CE2 (N = 10) or p55gag (N = 4), each delivered by intramuscular injection followed by in vivo electroporation as outlined in Figure 2A and previously reported [18], [19]. Plasma samples were collected on the day of vaccination and 2 and 8 weeks later. We have previously reported that vaccination with p24CE DNA induced strong cellular immunity targeting new epitopes [18], [19]. Here, we examined the development of Gag-specific humoral responses induced by the same immunization regimen. Animals vaccinated with p24CE DNA developed antibody responses against p24gag and the kinetics of these responses were similar to those induced by p55gag DNA vaccination (Figure 2B). p24gag antibody responses were detectable upon a single DNA vaccination, and were efficiently boosted by the 2nd DNA immunization resulting in peak antibody titers (∼5.3 log reciprocal end-point dilution) detected 2 weeks later. Similar levels of Gag-specific antibody responses were detected 8 weeks later in both groups of animals, indicating comparable persistence of humoral responses. These results demonstrate that p24CE DNA, an immunogen designed to elicit optimal T-cell responses, is able to induce humoral immune responses to p24gag of similar magnitude as those induced by the p55gag DNA vaccine.

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