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Immunogenicity when utilizing adenovirus serotype 4 and 5 vaccines expressing circumsporozoite protein in naïve and adenovirus (Ad5) immune mice.

Schuldt NJ, Aldhamen YA, Godbehere-Roosa S, Seregin SS, Kousa YA, Amalfitano A - Malar. J. (2012)

Bottom Line: Priming with Ad4-CSP followed by a homologous boost resulted in significantly less CSP specific humoral responses than any other vaccination regimen tested in Ad naïve animals.In Ad5 immune animals use of Ad4-CSP improved CSP specific immune responses as compared to repeated use of Ad5-CSP, but could not achieve the levels of immunogenicity observed when the same vaccine regimens were used in Ad naïve animals.Based on these results, it is suggested that future studies should undertake similarly stringent analyses of alternative Ad serotypes to establish their effectiveness as replacements for Ad5.

View Article: PubMed Central - HTML - PubMed

Affiliation: Genetics Program, Michigan State University, 2240 E Biomedical and Physical Sciences Building, East Lansing, MI 48824, USA.

ABSTRACT

Background: Induction of potent long lasting effector T cell responses against liver stage malaria antigens strongly correlates with protection from malaria. While Adenovirus serotype 5 (Ad5) based malaria vaccine platforms have the ability to induce potent effector T cell responses against transgenes, high rates of pre-existing Ad5 immunity in malaria endemic regions has prompted study of alternative Ad serotype based malaria vaccines as replacements for Ad5 based malaria vaccines. The research described in this article examines the utility of alternative serotype adenovirus serotype 4 (Ad4) expressing a sporozoite surface protein (circumsporozoite protein (CSP)) (Ad4-CSP) to induce immune responses against CSP. The immunogenicity of Ad4-CSP was also tested in homologous and heterologous prime boost vaccinations in both Ad5 naïve and Ad5 immune backgrounds as compared to use of Ad5-CSP.

Results: In Ad5 naïve animals, use of Ad4-CSP priming vaccinations followed by boosting with Ad5-CSP (Ad4-CSP/Ad5-CSP) maximally increased the numbers of CSP specific cytokine secreting cytotoxic T cells relative to repeated use of Ad5-CSP. The Ad4-CSP/Ad5-CSP regimen also induced equivalent levels of CSP specific cell killing as did homologous prime-boost vaccinations with Ad5-CSP, despite stimulating lower numbers of CSP specific cytotoxic T cells. Priming with Ad4-CSP followed by a homologous boost resulted in significantly less CSP specific humoral responses than any other vaccination regimen tested in Ad naïve animals. In Ad5 immune animals, addition of Ad4-CSP in homologous or heterologous prime boost resulted in inductions of higher CSP specific responses than animals repeatedly vaccinated with Ad5-CSP alone. However, the observed responses were well below those observed in similarly treated Ad naïve mice.

Conclusions: While the Ad4-CSP/Ad5-CSP and Ad5-CSP/Ad5-CSP vaccination regimens resulted in equivalent CSP specific killing in Ad naïve animals, Ad4-CSP/Ad5-CSP achieved this result with a lower percentage of CSP specific CD8+ T cells and a higher number of IFNγ secreting cells, suggesting that the Ad4-CSP/Ad5-CSP vaccination regimen elicits more efficient cytotoxic T cells. In Ad5 immune animals use of Ad4-CSP improved CSP specific immune responses as compared to repeated use of Ad5-CSP, but could not achieve the levels of immunogenicity observed when the same vaccine regimens were used in Ad naïve animals. These data indicate the existence of some level of immunological cross-reactivity between these two adenovirus subgroups. Based on these results, it is suggested that future studies should undertake similarly stringent analyses of alternative Ad serotypes to establish their effectiveness as replacements for Ad5.

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Memory responses triggered by vaccination with homologous and heterologous prime boost regimens utilizing Ad4-CSP and Ad5-CSP in Ad naïve mice. Splenocytes (B-C) and PBMCs (D-E) were collected two weeks after final vaccination. Cells were stained for CD62L-V450, CD127-PerCP Cy5.5, and CSP (NYD) tet-PE. CSP specific central memory T cells were determined as CD62L+ CD127+ cells that are tet+ and effector memory cells are CD62Llo CD127+ cells that are tet+. Provided above is an example of gating (A). Bars represent ± standard error. Statistical analysis was completed using One Way ANOVA with Student-Newman-Keuls post-hoc test, **, *** denotes significance over naïve, P < 0.01, P < 0.001.
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Figure 3: Memory responses triggered by vaccination with homologous and heterologous prime boost regimens utilizing Ad4-CSP and Ad5-CSP in Ad naïve mice. Splenocytes (B-C) and PBMCs (D-E) were collected two weeks after final vaccination. Cells were stained for CD62L-V450, CD127-PerCP Cy5.5, and CSP (NYD) tet-PE. CSP specific central memory T cells were determined as CD62L+ CD127+ cells that are tet+ and effector memory cells are CD62Llo CD127+ cells that are tet+. Provided above is an example of gating (A). Bars represent ± standard error. Statistical analysis was completed using One Way ANOVA with Student-Newman-Keuls post-hoc test, **, *** denotes significance over naïve, P < 0.01, P < 0.001.

Mentions: Ad vectors are known to elicit strong Tem cell responses thought to be due to more persistent antigen production. This is important in the context of a malaria vaccine as Tem cell responses have been shown to be beneficial in protecting against liver stage malaria[38]. The magnitude of CSP-specific central memory and effector memory CD8+ T cell responses was compared in each of the various prime boost regimens induced in splenocytes and PBMCs harvested 14 days after the boosting vaccinations. All prime boost regimens demonstrated much higher percentages of CSP specific Tcm cells and Tem cells than was observed in non-vaccinated animals as indicated by the percent of CD127+ CD62L+ and CD127+ CD62L- tet+ T cells present in the splenocytes (Figure 3B-C). The percentage of CSP specific Tcm and Tem cells circulating in the blood was also analysed and it was found that the Ad5-CSP/Ad4-CSP vaccination group was the only group that had a significantly higher percentage of CSP specific Tcm cells in circulating blood when compared to non-vaccinated animals, while all vaccinated animals had higher percentages of CSP specific Tem cells present in this compartment as compared to non-vaccinated animals (Figure 3D-E). When memory phenotypes were analysed by gating on tetramer positive cells first, followed by gating for CD127 and CD62L, the tetramer positive cells of all groups had similar memory phenotypes as defined by comparison of the percentages of tet+ cells that were Tem and those that were Tcm cell.


Immunogenicity when utilizing adenovirus serotype 4 and 5 vaccines expressing circumsporozoite protein in naïve and adenovirus (Ad5) immune mice.

Schuldt NJ, Aldhamen YA, Godbehere-Roosa S, Seregin SS, Kousa YA, Amalfitano A - Malar. J. (2012)

Memory responses triggered by vaccination with homologous and heterologous prime boost regimens utilizing Ad4-CSP and Ad5-CSP in Ad naïve mice. Splenocytes (B-C) and PBMCs (D-E) were collected two weeks after final vaccination. Cells were stained for CD62L-V450, CD127-PerCP Cy5.5, and CSP (NYD) tet-PE. CSP specific central memory T cells were determined as CD62L+ CD127+ cells that are tet+ and effector memory cells are CD62Llo CD127+ cells that are tet+. Provided above is an example of gating (A). Bars represent ± standard error. Statistical analysis was completed using One Way ANOVA with Student-Newman-Keuls post-hoc test, **, *** denotes significance over naïve, P < 0.01, P < 0.001.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3472263&req=5

Figure 3: Memory responses triggered by vaccination with homologous and heterologous prime boost regimens utilizing Ad4-CSP and Ad5-CSP in Ad naïve mice. Splenocytes (B-C) and PBMCs (D-E) were collected two weeks after final vaccination. Cells were stained for CD62L-V450, CD127-PerCP Cy5.5, and CSP (NYD) tet-PE. CSP specific central memory T cells were determined as CD62L+ CD127+ cells that are tet+ and effector memory cells are CD62Llo CD127+ cells that are tet+. Provided above is an example of gating (A). Bars represent ± standard error. Statistical analysis was completed using One Way ANOVA with Student-Newman-Keuls post-hoc test, **, *** denotes significance over naïve, P < 0.01, P < 0.001.
Mentions: Ad vectors are known to elicit strong Tem cell responses thought to be due to more persistent antigen production. This is important in the context of a malaria vaccine as Tem cell responses have been shown to be beneficial in protecting against liver stage malaria[38]. The magnitude of CSP-specific central memory and effector memory CD8+ T cell responses was compared in each of the various prime boost regimens induced in splenocytes and PBMCs harvested 14 days after the boosting vaccinations. All prime boost regimens demonstrated much higher percentages of CSP specific Tcm cells and Tem cells than was observed in non-vaccinated animals as indicated by the percent of CD127+ CD62L+ and CD127+ CD62L- tet+ T cells present in the splenocytes (Figure 3B-C). The percentage of CSP specific Tcm and Tem cells circulating in the blood was also analysed and it was found that the Ad5-CSP/Ad4-CSP vaccination group was the only group that had a significantly higher percentage of CSP specific Tcm cells in circulating blood when compared to non-vaccinated animals, while all vaccinated animals had higher percentages of CSP specific Tem cells present in this compartment as compared to non-vaccinated animals (Figure 3D-E). When memory phenotypes were analysed by gating on tetramer positive cells first, followed by gating for CD127 and CD62L, the tetramer positive cells of all groups had similar memory phenotypes as defined by comparison of the percentages of tet+ cells that were Tem and those that were Tcm cell.

Bottom Line: Priming with Ad4-CSP followed by a homologous boost resulted in significantly less CSP specific humoral responses than any other vaccination regimen tested in Ad naïve animals.In Ad5 immune animals use of Ad4-CSP improved CSP specific immune responses as compared to repeated use of Ad5-CSP, but could not achieve the levels of immunogenicity observed when the same vaccine regimens were used in Ad naïve animals.Based on these results, it is suggested that future studies should undertake similarly stringent analyses of alternative Ad serotypes to establish their effectiveness as replacements for Ad5.

View Article: PubMed Central - HTML - PubMed

Affiliation: Genetics Program, Michigan State University, 2240 E Biomedical and Physical Sciences Building, East Lansing, MI 48824, USA.

ABSTRACT

Background: Induction of potent long lasting effector T cell responses against liver stage malaria antigens strongly correlates with protection from malaria. While Adenovirus serotype 5 (Ad5) based malaria vaccine platforms have the ability to induce potent effector T cell responses against transgenes, high rates of pre-existing Ad5 immunity in malaria endemic regions has prompted study of alternative Ad serotype based malaria vaccines as replacements for Ad5 based malaria vaccines. The research described in this article examines the utility of alternative serotype adenovirus serotype 4 (Ad4) expressing a sporozoite surface protein (circumsporozoite protein (CSP)) (Ad4-CSP) to induce immune responses against CSP. The immunogenicity of Ad4-CSP was also tested in homologous and heterologous prime boost vaccinations in both Ad5 naïve and Ad5 immune backgrounds as compared to use of Ad5-CSP.

Results: In Ad5 naïve animals, use of Ad4-CSP priming vaccinations followed by boosting with Ad5-CSP (Ad4-CSP/Ad5-CSP) maximally increased the numbers of CSP specific cytokine secreting cytotoxic T cells relative to repeated use of Ad5-CSP. The Ad4-CSP/Ad5-CSP regimen also induced equivalent levels of CSP specific cell killing as did homologous prime-boost vaccinations with Ad5-CSP, despite stimulating lower numbers of CSP specific cytotoxic T cells. Priming with Ad4-CSP followed by a homologous boost resulted in significantly less CSP specific humoral responses than any other vaccination regimen tested in Ad naïve animals. In Ad5 immune animals, addition of Ad4-CSP in homologous or heterologous prime boost resulted in inductions of higher CSP specific responses than animals repeatedly vaccinated with Ad5-CSP alone. However, the observed responses were well below those observed in similarly treated Ad naïve mice.

Conclusions: While the Ad4-CSP/Ad5-CSP and Ad5-CSP/Ad5-CSP vaccination regimens resulted in equivalent CSP specific killing in Ad naïve animals, Ad4-CSP/Ad5-CSP achieved this result with a lower percentage of CSP specific CD8+ T cells and a higher number of IFNγ secreting cells, suggesting that the Ad4-CSP/Ad5-CSP vaccination regimen elicits more efficient cytotoxic T cells. In Ad5 immune animals use of Ad4-CSP improved CSP specific immune responses as compared to repeated use of Ad5-CSP, but could not achieve the levels of immunogenicity observed when the same vaccine regimens were used in Ad naïve animals. These data indicate the existence of some level of immunological cross-reactivity between these two adenovirus subgroups. Based on these results, it is suggested that future studies should undertake similarly stringent analyses of alternative Ad serotypes to establish their effectiveness as replacements for Ad5.

Show MeSH
Related in: MedlinePlus