title: Immunization with DNA Plasmids Coding for Crimean-Congo Hemorrhagic Fever Virus Capsid and Envelope Proteins and/or Virus-Like Particles Induces Protection and Survival in Challenged Mice.
abstract: Crimean-Congo hemorrhagic fever virus (CCHFV) is a bunyavirus causing severe hemorrhagic fever disease in humans, with high mortality rates. The requirement of a high-containment laboratory and the lack of an animal model hampered the study of the immune response and protection of vaccine candidates. Using the recently developed interferon alpha receptor knockout (IFNAR-/-) mouse model, which replicates human disease, we investigated the immunogenicity and protection of two novel CCHFV vaccine candidates: a DNA vaccine encoding a ubiquitin-linked version of CCHFV Gc, Gn, and N and one using transcriptionally competent virus-like particles (tc-VLPs). In contrast to most studies that focus on neutralizing antibodies, we measured both humoral and cellular immune responses. We demonstrated a clear and 100% efficient preventive immunity against lethal CCHFV challenge with the DNA vaccine. Interestingly, there was no correlation with the neutralizing antibody titers alone, which were higher in the tc-VLP-vaccinated mice. However, the animals with a lower neutralizing titer, but a dominant cell-mediated Th1 response and a balanced Th2 response, resisted the CCHFV challenge. Moreover, we found that in challenged mice with a Th1 response (immunized by DNA/DNA and boosted by tc-VLPs), the immune response changed to Th2 at day 9 postchallenge. In addition, we were able to identify new linear B-cell epitope regions that are highly conserved between CCHFV strains. Altogether, our results suggest that a predominantly Th1-type immune response provides the most efficient protective immunity against CCHFV challenge. However, we cannot exclude the importance of the neutralizing antibodies as the surviving immunized mice exhibited substantial amounts of them.IMPORTANCECrimean-Congo hemorrhagic fever virus (CCHFV) is responsible for hemorrhagic diseases in humans, with a high mortality rate. There is no FDA-approved vaccine, and there are still gaps in our knowledge of the immune responses to infection. The recently developed mouse models mimic human CCHF disease and are useful to study the immunogenicity and the protection by vaccine candidates. Our study shows that mice vaccinated with a specific DNA vaccine were fully protected. Importantly, we show that neutralizing antibodies are not sufficient for protection against CCHFV challenge but that an extra Th1-specific cellular response is required. Moreover, we describe the identification of five conserved B-cell epitopes, of which only one was previously known, that could be of great importance for the development of diagnostics tools and the improvement of vaccine candidates.
authors.affiliation: Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden.|Microbiology and Tumorbiology Center, Karolinska Institutet, Solna, Sweden.
authors.forename: Jorma
authors.initials: J
authors.lastname: Hinkula
authors.affiliation: Institute for Virology, Philipps University Marburg, Marburg, Germany.|Institute for Virology, FB10, Justus Liebig University, Giessen, Germany.
authors.forename: Stéphanie
authors.identifier: http://orcid.org/0000-0002-0618-5611
authors.initials: S
authors.lastname: Devignot
authors.affiliation: National Veterinary Institute, Uppsala, Sweden.
authors.forename: Sara
authors.initials: S
authors.lastname: Åkerström
authors.affiliation: Folkhälsomyndigheten, Stockholm, Sweden.
authors.forename: Helen
authors.initials: H
authors.lastname: Karlberg
authors.affiliation: National Veterinary Institute, Uppsala, Sweden.
authors.forename: Eva
authors.initials: E
authors.lastname: Wattrang
authors.affiliation: Folkhälsomyndigheten, Stockholm, Sweden.
authors.forename: Sándor
authors.initials: S
authors.lastname: Bereczky
authors.affiliation: Folkhälsomyndigheten, Stockholm, Sweden.
authors.forename: Mehrdad
authors.initials: M
authors.lastname: Mousavi-Jazi
authors.affiliation: Department of Chemistry, University of Copenhagen, Frederiksberg, Denmark.
authors.forename: Christian
authors.initials: C
authors.lastname: Risinger
authors.affiliation: Folkhälsomyndigheten, Stockholm, Sweden.
authors.forename: Gunnel
authors.initials: G
authors.lastname: Lindegren
authors.affiliation: National Veterinary Institute, Uppsala, Sweden.
authors.forename: Caroline
authors.initials: C
authors.lastname: Vernersson
authors.affiliation: Centre for Emerging and Zoonotic Diseases, National Institute for Communicable Diseases, National Health Laboratory Service, Sandringham, South Africa.
authors.forename: Janusz
authors.initials: J
authors.lastname: Paweska
authors.affiliation: Centre for Emerging and Zoonotic Diseases, National Institute for Communicable Diseases, National Health Laboratory Service, Sandringham, South Africa.
authors.forename: Petrus Jansen
authors.initials: PJ
authors.lastname: van Vuren
authors.affiliation: Department of Chemistry, University of Copenhagen, Frederiksberg, Denmark.
authors.forename: Ola
authors.initials: O
authors.lastname: Blixt
authors.affiliation: Centro de Investigación en Sanidad Animal, Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, Madrid, Spain.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Brun
authors.affiliation: Institute for Virology, Philipps University Marburg, Marburg, Germany.|Institute for Virology, FB10, Justus Liebig University, Giessen, Germany.
authors.forename: Friedemann
authors.identifier: http://orcid.org/0000-0001-9737-337X
authors.initials: F
authors.lastname: Weber
authors.affiliation: Folkhälsomyndigheten, Stockholm, Sweden Ali.Mirazimi@ki.se.|National Veterinary Institute, Uppsala, Sweden.|Department of Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Ali
authors.initials: A
authors.lastname: Mirazimi
mesh_terms: D000818:Animals; D057134:Antibodies, Neutralizing / Q000097:blood; D036022:Capsid Proteins / Q000235:genetics / Q000276:immunology*; D004195:Disease Models, Animal; D018985:Epitopes, B-Lymphocyte / Q000276:immunology; D003225:Hemorrhagic Fever Virus, Crimean-Congo / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D006479:Hemorrhagic Fever, Crimean / Q000276:immunology* / Q000517:prevention & control* / Q000821:virology; D006801:Humans; D007111:Immunity, Cellular; D007114:Immunization; D000071497:Immunogenicity, Vaccine; D016898:Interferon-alpha / Q000172:deficiency / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D010957:Plasmids / Q000008:administration & dosage / Q000235:genetics*; D018417:Th1 Cells; D018418:Th2 Cells; D019444:Vaccines, DNA / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology*; D058425:Vaccines, Virus-Like Particle / Q000008:administration & dosage / Q000276:immunology*; D014759:Viral Envelope Proteins / Q000235:genetics / Q000276:immunology*
chemical_list: D057134:Antibodies, Neutralizing; D036022:Capsid Proteins; D018985:Epitopes, B-Lymphocyte; D016898:Interferon-alpha; D019444:Vaccines, DNA; D058425:Vaccines, Virus-Like Particle; D014759:Viral Envelope Proteins
keywords: Crimean-Congo hemorrhagic fever virus; DNA vaccines; Th1/Th2 responses; VLP; neutralizing antibodies