Phenotypic and genetic diversity of the traditional Lister smallpox vaccine

Smallpox was eradicated using variant forms of vaccinia virus-based vaccines. One of these was Dryvax, a calf lymph vaccine derived from the New York City Board of Health strain. We used genome-sequencing technology to examine the genetic diversity of the population of viruses present in a sample of Dryvax. These studies show that the conserved cores of these viruses exhibit a lower level of sequence variation than do the telomeres. However, even though the ends of orthopoxviruses are more genetically plastic than the cores, there are still many telomeric genes that are conserved as intact open reading frames in the 11 genomes that we, and 4 genomes that others, have sequenced. Most of these genes likely modulate inflammation. Our sequencing also detected an evolving pattern of mutation, with some genes being highly fragmented by randomly assorting mutations (e.g., M1L), while other genes are intact in most viruses but have been disrupted in individual strains (e.g., I4L in strain DPP17). Over 85% of insertion and deletion mutations are associated with repeats, and a rare new isolate bearing a large deletion in the right telomere was identified. All of these strains cluster in dendrograms consistent with their origin but which also surprisingly incorporate horsepox virus. However, these viruses also exhibit a "patchy" pattern of polymorphic sites characteristic of recombinants. There is more genetic diversity detected within a vial of Dryvax than between variola virus major and minor strains, and our study highlights how propagation methods affect the genetics of orthopoxvirus populations.

Section: Downloaded Fromsupporting

confidence: 59%

“…The fact that old smallpox vaccines comprise a quasispecies is not restricted to Dryvax, of course. Garcel et al have documented a diversity of phenotypes exhibited by clones isolated from a stock of the VACV strain Lister (13), and shotgun sequencing of unpurified stocks identified Ͼ1,200 polymorphic sites distributed across a mix of Lister genomes (23).…”

mentioning

confidence: 99%

Genomic Analysis of the Vaccinia Virus Strain Variants Found in Dryvax Vaccine

Qin

Upton

Hazes

et al. 2011

“…Viral clones isolated from these vaccines may differ in virulence, efficacy of immune protection, and genetic content (8)(9)(10)(11)(12). In fact, the second-generation smallpox vaccine currently produced in the United States, ACAM2000, is a clone of the first-generation vaccine used in the country, Dryvax.…”

mentioning

confidence: 99%

“…In addition to the search for safer vaccines, recent genetic studies of clonal variants of first-generation vaccines have improved our understanding of the phylogenetic relationships and obscure origins of different VACV strains (8,11,12). Nevertheless, numerous questions remain unanswered.…”

mentioning

confidence: 99%

Genomic Analysis, Phenotype, and Virulence of the Historical Brazilian Smallpox Vaccine Strain IOC: Implications for the Origins and Evolutionary Relationships of Vaccinia Virus

Medaglia

Moussatché

Nitsche

et al. 2015

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. IMPORTANCEFirst-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. S mallpox, caused by variola virus (genus Orthopoxvirus, family Poxviridae), accounted for millions of deaths throughout human history. The disease was declared eradicated in 1980 after a worldwide program implemented by the WHO involving strict surveillance and intensive vaccination using vaccinia vi...

“…A clonal isolate of the Lister strain of the smallpox vaccine, designated VACV-107 (22,23), was used as the parental strain for isolation of deletion mutants. Virus was propagated on the chicken embryonic stem cell line EB 14 (provided by Vivalis, France) cultured in Dulbecco's modified Eagle medium (DMEM)-F12 medium supplemented with 10% fetal calf serum (FCS), nonessential amino acids, 1 mM sodium pyruvate, and 40 g/ml gentamicin.…”

Section: Methodsmentioning

confidence: 99%

Deletion of Major Nonessential Genomic Regions in the Vaccinia Virus Lister Strain Enhances Attenuation without Altering Vaccine Efficacy in Mice

Dimier

Ferrier-Rembert

Pradeau‐Aubreton

et al. 2011

Self Cite

The vaccinia virus (VACV) Lister strain was one of the vaccine strains that enabled smallpox eradication. Although the strain is most often harmless, there have been numerous incidents of mild to life-threatening accidents with this strain and others. In an attempt to further attenuate the Lister strain, we investigated the role of 5 genomic regions known to be deleted in the modified VACV Ankara (MVA) genome in virulence in immunodeficient mice, immunogenicity in immunocompetent mice, and vaccine efficacy in a cowpox virus challenge model. Lister mutants were constructed so as to delete each of the 5 regions or various combinations of these regions. All of the mutants replicated efficiently in tissue culture except region I mutants, which multiplied more poorly in human cells than the parental strain. Mutants with single deletions were not attenuated or only moderately so in athymic nude mice. Mutants with multiple deletions were more highly attenuated than those with single deletions. Deleting regions II, III, and V together resulted in total attenuation for nude mice and partial attenuation for SCID mice. In immunocompetent mice, the Lister deletion mutants induced VACV specific humoral responses equivalent to those of the parental strain but in some cases lower cell-mediated immune responses. All of the highly attenuated mutants protected mice from a severe cowpox virus challenge at low vaccine doses. The data suggest that several of the Lister mutants combining multiple deletions could be used in smallpox vaccination or as live virus vectors at doses equivalent to those used for the traditional vaccine while displaying increased safety.Vaccinia virus (VACV) has displayed extraordinary efficacy as a live attenuated vaccine since it has enabled the eradication of smallpox, one of the most deadly infectious diseases for mankind. Although smallpox vaccination is no longer routinely employed, some countries continue to vaccinate selected populations because of the fear of biological warfare or bioterrorism. During the course of their use, the smallpox vaccines were responsible for numerous vaccine-associated accidents like eczema vaccinatum and progressive vaccinia in individuals with immune deficiencies or skin disorders. Encephalitis was also long recognized as a very serious vaccine-related risk with an unknown predisposition (35), and vaccine-induced myopericarditis has been documented as an adverse event (27, 32). It is therefore not surprising that a good deal of research has been devoted to designing strategies that reduce the risks associated with smallpox vaccination (52). Further attenuation of the smallpox vaccine has also been sought because VACV is an attractive live virus vector for vaccination against infectious diseases and displays promising activity as a vector for prophylaxis and therapy of cancer (25).Modified vaccinia virus Ankara (MVA) was one of the first VACV strains shown to be highly attenuated in small-animal models and safe in human trials (42,66). MVA was isolated during the 1960s fr...