title: Genomic Analysis, Phenotype, and Virulence of the Historical Brazilian Smallpox Vaccine Strain IOC: Implications for the Origins and Evolutionary Relationships of Vaccinia Virus.
abstract: Smallpox was declared eradicated in 1980 after an intensive vaccination program using different strains of vaccinia virus (VACV; Poxviridae). VACV strain IOC (VACV-IOC) was the seed strain of the smallpox vaccine manufactured by the major vaccine producer in Brazil during the smallpox eradication program. However, little is known about the biological and immunological features as well as the phylogenetic relationships of this first-generation vaccine. In this work, we present a comprehensive characterization of two clones of VACV-IOC. Both clones had low virulence in infected mice and induced a protective immune response against a lethal infection comparable to the response of the licensed vaccine ACAM2000 and the parental strain VACV-IOC. Full-genome sequencing revealed the presence of several fragmented virulence genes that probably are nonfunctional, e.g., F1L, B13R, C10L, K3L, and C3L. Most notably, phylogenetic inference supported by the structural analysis of the genome ends provides evidence of a novel, independent cluster in VACV phylogeny formed by VACV-IOC, the Brazilian field strains Cantagalo (CTGV) and Serro 2 viruses, and horsepox virus, a VACV-like virus supposedly related to an ancestor of the VACV lineage. Our data strongly support the hypothesis that CTGV-like viruses represent feral VACV that evolved in parallel with VACV-IOC after splitting from a most recent common ancestor, probably an ancient smallpox vaccine strain related to horsepox virus. Our data, together with an interesting historical investigation, revisit the origins of VACV and propose new evolutionary relationships between ancient and extant VACV strains, mainly horsepox virus, VACV-IOC/CTGV-like viruses, and Dryvax strain.
  
  
  OBJECTIVE
  First-generation vaccines used to eradicate smallpox had rates of adverse effects that are not acceptable by current health care standards. Moreover, these vaccines are genetically heterogeneous and consist of a pool of quasispecies of VACV. Therefore, the search for new-generation smallpox vaccines that combine low pathogenicity, immune protection, and genetic homogeneity is extremely important. In addition, the phylogenetic relationships and origins of VACV strains are quite nebulous. We show the characterization of two clones of VACV-IOC, a unique smallpox vaccine strain that contributed to smallpox eradication in Brazil. The immunogenicity and reduced virulence make the IOC clones good options for alternative second-generation smallpox vaccines. More importantly, this study reveals the phylogenetic relationship between VACV-IOC, feral VACV established in nature, and the ancestor-like horsepox virus. Our data expand the discussion on the origins and evolutionary connections of VACV lineages.
authors.affiliation: Laboratório de Biologia Molecular de Vírus, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Maria Luiza G
authors.initials: ML
authors.lastname: Medaglia
authors.affiliation: Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, Florida, USA.
authors.forename: Nissin
authors.initials: N
authors.lastname: Moussatché
authors.affiliation: Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Nitsche
authors.affiliation: Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany.
authors.forename: Pjotr Wojtek
authors.initials: PW
authors.lastname: Dabrowski
authors.affiliation: Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Diseases, Atlanta, Georgia, USA.
authors.forename: Yu
authors.initials: Y
authors.lastname: Li
authors.affiliation: Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Diseases, Atlanta, Georgia, USA.
authors.forename: Inger K
authors.initials: IK
authors.lastname: Damon
authors.affiliation: Departamento de Virologia, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Carolina G O
authors.initials: CG
authors.lastname: Lucas
authors.affiliation: Departamento de Virologia, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Luciana B
authors.initials: LB
authors.lastname: Arruda
authors.affiliation: Laboratório de Biologia Molecular de Vírus, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil damasoc@biof.ufrj.br.
authors.forename: Clarissa R
authors.initials: CR
authors.lastname: Damaso
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001483:Base Sequence; D001499:Bayes Theorem; D005075:Biological Evolution; D001938:Brazil; D002460:Cell Line; D020552:Comet Assay; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D051379:Mice; D008807:Mice, Inbred BALB C; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D012899:Smallpox / Q000517:prevention & control*; D013045:Species Specificity; D014616:Vaccinia virus / Q000235:genetics* / Q000276:immunology / Q000472:pathogenicity; D014765:Viral Vaccines / Q000235:genetics*; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics
chemical_list: D007074:Immunoglobulin G; D014765:Viral Vaccines; D037521:Virulence Factors