Binding of the von Willebrand Factor A Domain of Capillary Morphogenesis Protein 2 to Anthrax Protective Antigen Vaccine Reduces Immunogenicity in Mice

ABSTRACT Protective antigen (PA) is a component of anthrax toxin that can elicit toxin-neutralizing antibody responses. PA is also the major antigen in the current vaccine to prevent anthrax, but stability problems with recombinant proteins have complicated the development of new vaccines containing...

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Autores principales:	Fabiana Freire Mendes de Oliveira, Sireesha Mamillapalli, Srinivas Gonti, Robert N. Brey, Han Li, Jarad Schiffer, Arturo Casadevall, James G. Bann
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2020
Materias:	anthrax antigen processing immunization protein stability Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/c5b08a3442284ba9b28cd6995fad9269
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spelling	oai:doaj.org-article:c5b08a3442284ba9b28cd6995fad92692021-11-15T15:27:52ZBinding of the von Willebrand Factor A Domain of Capillary Morphogenesis Protein 2 to Anthrax Protective Antigen Vaccine Reduces Immunogenicity in Mice10.1128/mSphere.00556-192379-5042https://doaj.org/article/c5b08a3442284ba9b28cd6995fad92692020-02-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mSphere.00556-19https://doaj.org/toc/2379-5042ABSTRACT Protective antigen (PA) is a component of anthrax toxin that can elicit toxin-neutralizing antibody responses. PA is also the major antigen in the current vaccine to prevent anthrax, but stability problems with recombinant proteins have complicated the development of new vaccines containing recombinant PA. The relationship between antigen physical stability and immunogenicity is poorly understood, but there are theoretical reasons to think that this parameter can affect immune responses. We investigated the immunogenicity of anthrax PA, in the presence and absence of the soluble von Willebrand factor A domain of the human form of receptor capillary morphogenesis protein 2 (sCMG2), to elicit antibodies to PA in BALB/c mice. Prior studies showed that sCMG2 stabilizes the 83-kDa PA structure to pH, chemical denaturants, temperature, and proteolysis and slows the hydrogen-deuterium exchange rate of histidine residues far from the binding interface. In contrast to a vaccine containing PA without adjuvant, we found that mice immunized with PA in stable complex with sCMG2 showed markedly reduced antibody responses to PA, including toxin-neutralizing antibodies and antibodies to domain 4, which correlated with fewer toxin-neutralizing antibodies. In contrast, mice immunized with PA in concert with a nonbinding mutant of sCMG2 (D50A) showed anti-PA antibody responses similar to those observed with PA alone. Our results suggest that addition of sCMG2 to a PA vaccine formulation is likely to result in a significantly diminished immune response, but we discuss the multitude of factors that could contribute to reduced immunogenicity. IMPORTANCE The anthrax toxin PA is the major immunogen in the current anthrax vaccine (anthrax vaccine adsorbed). Improving the anthrax vaccine for avoidance of a cold chain necessitates improvements in the thermodynamic stability of PA. We address how stabilizing PA using sCMG2 affects PA immunogenicity in BALB/c mice. Although the stability of PA is increased by binding to sCMG2, PA immunogenicity is decreased. This study emphasizes that, while binding of a ligand retains or improves conformational stability without affecting the native sequence, epitope recognition or processing may be affected, abrogating an effective immune response.Fabiana Freire Mendes de OliveiraSireesha MamillapalliSrinivas GontiRobert N. BreyHan LiJarad SchifferArturo CasadevallJames G. BannAmerican Society for Microbiologyarticleanthraxantigen processingimmunizationprotein stabilityMicrobiologyQR1-502ENmSphere, Vol 5, Iss 1 (2020)
institution	DOAJ
collection	DOAJ
language	EN
topic	anthrax antigen processing immunization protein stability Microbiology QR1-502
spellingShingle	anthrax antigen processing immunization protein stability Microbiology QR1-502 Fabiana Freire Mendes de Oliveira Sireesha Mamillapalli Srinivas Gonti Robert N. Brey Han Li Jarad Schiffer Arturo Casadevall James G. Bann Binding of the von Willebrand Factor A Domain of Capillary Morphogenesis Protein 2 to Anthrax Protective Antigen Vaccine Reduces Immunogenicity in Mice
description	ABSTRACT Protective antigen (PA) is a component of anthrax toxin that can elicit toxin-neutralizing antibody responses. PA is also the major antigen in the current vaccine to prevent anthrax, but stability problems with recombinant proteins have complicated the development of new vaccines containing recombinant PA. The relationship between antigen physical stability and immunogenicity is poorly understood, but there are theoretical reasons to think that this parameter can affect immune responses. We investigated the immunogenicity of anthrax PA, in the presence and absence of the soluble von Willebrand factor A domain of the human form of receptor capillary morphogenesis protein 2 (sCMG2), to elicit antibodies to PA in BALB/c mice. Prior studies showed that sCMG2 stabilizes the 83-kDa PA structure to pH, chemical denaturants, temperature, and proteolysis and slows the hydrogen-deuterium exchange rate of histidine residues far from the binding interface. In contrast to a vaccine containing PA without adjuvant, we found that mice immunized with PA in stable complex with sCMG2 showed markedly reduced antibody responses to PA, including toxin-neutralizing antibodies and antibodies to domain 4, which correlated with fewer toxin-neutralizing antibodies. In contrast, mice immunized with PA in concert with a nonbinding mutant of sCMG2 (D50A) showed anti-PA antibody responses similar to those observed with PA alone. Our results suggest that addition of sCMG2 to a PA vaccine formulation is likely to result in a significantly diminished immune response, but we discuss the multitude of factors that could contribute to reduced immunogenicity. IMPORTANCE The anthrax toxin PA is the major immunogen in the current anthrax vaccine (anthrax vaccine adsorbed). Improving the anthrax vaccine for avoidance of a cold chain necessitates improvements in the thermodynamic stability of PA. We address how stabilizing PA using sCMG2 affects PA immunogenicity in BALB/c mice. Although the stability of PA is increased by binding to sCMG2, PA immunogenicity is decreased. This study emphasizes that, while binding of a ligand retains or improves conformational stability without affecting the native sequence, epitope recognition or processing may be affected, abrogating an effective immune response.
format	article
author	Fabiana Freire Mendes de Oliveira Sireesha Mamillapalli Srinivas Gonti Robert N. Brey Han Li Jarad Schiffer Arturo Casadevall James G. Bann
author_facet	Fabiana Freire Mendes de Oliveira Sireesha Mamillapalli Srinivas Gonti Robert N. Brey Han Li Jarad Schiffer Arturo Casadevall James G. Bann
author_sort	Fabiana Freire Mendes de Oliveira
title	Binding of the von Willebrand Factor A Domain of Capillary Morphogenesis Protein 2 to Anthrax Protective Antigen Vaccine Reduces Immunogenicity in Mice
title_short	Binding of the von Willebrand Factor A Domain of Capillary Morphogenesis Protein 2 to Anthrax Protective Antigen Vaccine Reduces Immunogenicity in Mice
title_full	Binding of the von Willebrand Factor A Domain of Capillary Morphogenesis Protein 2 to Anthrax Protective Antigen Vaccine Reduces Immunogenicity in Mice
title_fullStr	Binding of the von Willebrand Factor A Domain of Capillary Morphogenesis Protein 2 to Anthrax Protective Antigen Vaccine Reduces Immunogenicity in Mice
title_full_unstemmed	Binding of the von Willebrand Factor A Domain of Capillary Morphogenesis Protein 2 to Anthrax Protective Antigen Vaccine Reduces Immunogenicity in Mice
title_sort	binding of the von willebrand factor a domain of capillary morphogenesis protein 2 to anthrax protective antigen vaccine reduces immunogenicity in mice
publisher	American Society for Microbiology
publishDate	2020
url	https://doaj.org/article/c5b08a3442284ba9b28cd6995fad9269
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Binding of the von Willebrand Factor A Domain of Capillary Morphogenesis Protein 2 to Anthrax Protective Antigen Vaccine Reduces Immunogenicity in Mice

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