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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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HIV-1 p55gag DNA vaccination did not prime de novo CE humoral responses but increased pre-existing CE-specific responses.(A) Cartoon depicts the vaccination schedule. After receiving p24CE or p55gag DNA as priming vaccination (see Figure 2) the animals received a heterologous boost vaccination (vaccination 3) with p55gag DNA or p24CE DNA, respectively. (B) Comparison of plasma bAb to HIV-1 p24gag ELISA titers at vaccination 3 and 2 weeks later. The reciprocal Gag antibody endpoint titers (in log10) from individual macaques vaccinated with the p24CE DNA mixture following by a p55Gag DNA boost (N = 10; left panel) and macaques vaccinated with p55Gag DNA followed by a p24CE DNA boost (N = 4; right panel) are shown. Data from day of 3rd vaccination are from Fig. 2B. (C, D) Western immunoblot analysis was used to test macaque plasma for binding antibodies before (after vaccination 2) and after the boost (after vaccination 3). The membranes contain the soluble processed p24gag (lane 1), p24CE1 (lane 2) or p24CE2 (lane 3) proteins and were probed with plasma collected 2 weeks after vaccinations 2 and 3. Data from 2 representative macaques are shown from each vaccine group. The membranes were probed with plasma from (C) macaques (L862, M166), which received the p24CE prime-p55gag DNA boost (plasma dilution 1:2000) and from (D) macaques (P574, R288), which received the p55gag prime-p24CE DNA boost regimen (plasma dilution 1:500).
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pone-0111085-g004: HIV-1 p55gag DNA vaccination did not prime de novo CE humoral responses but increased pre-existing CE-specific responses.(A) Cartoon depicts the vaccination schedule. After receiving p24CE or p55gag DNA as priming vaccination (see Figure 2) the animals received a heterologous boost vaccination (vaccination 3) with p55gag DNA or p24CE DNA, respectively. (B) Comparison of plasma bAb to HIV-1 p24gag ELISA titers at vaccination 3 and 2 weeks later. The reciprocal Gag antibody endpoint titers (in log10) from individual macaques vaccinated with the p24CE DNA mixture following by a p55Gag DNA boost (N = 10; left panel) and macaques vaccinated with p55Gag DNA followed by a p24CE DNA boost (N = 4; right panel) are shown. Data from day of 3rd vaccination are from Fig. 2B. (C, D) Western immunoblot analysis was used to test macaque plasma for binding antibodies before (after vaccination 2) and after the boost (after vaccination 3). The membranes contain the soluble processed p24gag (lane 1), p24CE1 (lane 2) or p24CE2 (lane 3) proteins and were probed with plasma collected 2 weeks after vaccinations 2 and 3. Data from 2 representative macaques are shown from each vaccine group. The membranes were probed with plasma from (C) macaques (L862, M166), which received the p24CE prime-p55gag DNA boost (plasma dilution 1:2000) and from (D) macaques (P574, R288), which received the p55gag prime-p24CE DNA boost regimen (plasma dilution 1:500).

Mentions: We next asked whether boosting with the heterologous DNA plasmid could increase pre-existing humoral responses. Animals from both groups received an additional DNA vaccination as outlined in Figure 4A and the responses were monitored by ELISA. Sustained antibody responses were observed at the day of the heterologous boost vaccination in both groups (Figure 4B, vaccination 3) as a result of the prior priming vaccination. Plasma samples collected 2 weeks later showed that these responses were further boosted by heterologous DNA vaccination in both vaccine groups. Boosting of p24CE DNA primed responses by p55gag DNA resulted in an average 0.8 log increase in ELISA titers, and boosting of p55gag DNA primed responses by p24CE DNA increase the Gag ELIA titers by 0.9 log.


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)

HIV-1 p55gag DNA vaccination did not prime de novo CE humoral responses but increased pre-existing CE-specific responses.(A) Cartoon depicts the vaccination schedule. After receiving p24CE or p55gag DNA as priming vaccination (see Figure 2) the animals received a heterologous boost vaccination (vaccination 3) with p55gag DNA or p24CE DNA, respectively. (B) Comparison of plasma bAb to HIV-1 p24gag ELISA titers at vaccination 3 and 2 weeks later. The reciprocal Gag antibody endpoint titers (in log10) from individual macaques vaccinated with the p24CE DNA mixture following by a p55Gag DNA boost (N = 10; left panel) and macaques vaccinated with p55Gag DNA followed by a p24CE DNA boost (N = 4; right panel) are shown. Data from day of 3rd vaccination are from Fig. 2B. (C, D) Western immunoblot analysis was used to test macaque plasma for binding antibodies before (after vaccination 2) and after the boost (after vaccination 3). The membranes contain the soluble processed p24gag (lane 1), p24CE1 (lane 2) or p24CE2 (lane 3) proteins and were probed with plasma collected 2 weeks after vaccinations 2 and 3. Data from 2 representative macaques are shown from each vaccine group. The membranes were probed with plasma from (C) macaques (L862, M166), which received the p24CE prime-p55gag DNA boost (plasma dilution 1:2000) and from (D) macaques (P574, R288), which received the p55gag prime-p24CE DNA boost regimen (plasma dilution 1:500).
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pone-0111085-g004: HIV-1 p55gag DNA vaccination did not prime de novo CE humoral responses but increased pre-existing CE-specific responses.(A) Cartoon depicts the vaccination schedule. After receiving p24CE or p55gag DNA as priming vaccination (see Figure 2) the animals received a heterologous boost vaccination (vaccination 3) with p55gag DNA or p24CE DNA, respectively. (B) Comparison of plasma bAb to HIV-1 p24gag ELISA titers at vaccination 3 and 2 weeks later. The reciprocal Gag antibody endpoint titers (in log10) from individual macaques vaccinated with the p24CE DNA mixture following by a p55Gag DNA boost (N = 10; left panel) and macaques vaccinated with p55Gag DNA followed by a p24CE DNA boost (N = 4; right panel) are shown. Data from day of 3rd vaccination are from Fig. 2B. (C, D) Western immunoblot analysis was used to test macaque plasma for binding antibodies before (after vaccination 2) and after the boost (after vaccination 3). The membranes contain the soluble processed p24gag (lane 1), p24CE1 (lane 2) or p24CE2 (lane 3) proteins and were probed with plasma collected 2 weeks after vaccinations 2 and 3. Data from 2 representative macaques are shown from each vaccine group. The membranes were probed with plasma from (C) macaques (L862, M166), which received the p24CE prime-p55gag DNA boost (plasma dilution 1:2000) and from (D) macaques (P574, R288), which received the p55gag prime-p24CE DNA boost regimen (plasma dilution 1:500).
Mentions: We next asked whether boosting with the heterologous DNA plasmid could increase pre-existing humoral responses. Animals from both groups received an additional DNA vaccination as outlined in Figure 4A and the responses were monitored by ELISA. Sustained antibody responses were observed at the day of the heterologous boost vaccination in both groups (Figure 4B, vaccination 3) as a result of the prior priming vaccination. Plasma samples collected 2 weeks later showed that these responses were further boosted by heterologous DNA vaccination in both vaccine groups. Boosting of p24CE DNA primed responses by p55gag DNA resulted in an average 0.8 log increase in ELISA titers, and boosting of p55gag DNA primed responses by p24CE DNA increase the Gag ELIA titers by 0.9 log.

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