Abstract
Since 1999, several Vaccinia virus (VACV) isolates, the etiological agents of bovine vaccinia (BV), have been frequently isolated and characterized with various biological and molecular methods. The results from these approaches have grouped these VACV isolates into two different clusters. This dichotomy has elicited debates surrounding the origin of the Brazilian VACV and its epidemiological significance. To ascertain vital information to settle these debates, we and other research groups have made efforts to identify molecular markers to discriminate VACV from other viruses of the genus Orthopoxvirus (OPV) and other VACV-BR groups. In this way, some genes have been identified as useful markers to discriminate between the VACV-BR groups. However, new markers are needed to infer ancestry and to correlate each sample or group with its unique epidemiological and biological features. The aims of this work were to characterize a new VACV isolate (VACV DMTV-2005) molecularly and biologically using conserved and non-conserved gene analyses for phylogenetic inference and to search for new genes that would elucidate the VACV-BR dichotomy. The VACV DMTV-2005 isolate reported in this study is biologically and phylogenetically clustered with other strains of Group 1 VACV-BR, the most prevalent VACV group that was isolated during the bovine vaccinia outbreaks in Brazil. Sequence analysis of C23L, the gene that encodes for the CC-chemokine-binding protein, revealed a ten-nucleotide deletion, which is a new Group 1 Brazilian VACV genetic marker. This deletion in the C23L open reading frame produces a premature stop-codon that is shared by all Group 1 VACV-BR strains and may also reflect the VACV-BR dichotomy; the deletion can also be considered to be a putative genetic marker for non-virulent Brazilian VACV isolates and may be used for the detection and molecular characterization of new isolates.
Highlights
The smallpox eradication campaign, which was promoted by the World Health Organization (WHO) in the 1960s and 1970s, represents a major milestone in medical history [1,2]
The smallpox vaccines used in the WHO campaign were, strains of the Vaccinia virus (VACV), a species belonging to the genus Orthopoxvirus (OPV), which induced serological cross-reactivity against other OPV members, including Variola virus (VARV) [3,1]
Smallpox vaccination was suspended due to several cases of adverse manifestations from the vaccine [4]. Despite this remarkable victory against VARV, the suspension of smallpox vaccination led to the emergence of a generation that is susceptible to other OPV species [4]. This fact may explain the emergence of zoonotic OPV species such as Cowpox virus (CPXV) in Europe [5]; Monkeypox virus (MPXV) [6], which occurs naturally in Africa and was recently introduced in the USA; and, ironically, VACV in rural areas of Brazil and India, which has been associated with exanthematic outbreaks in both humans and cattle [7,8,9]
Summary
The smallpox eradication campaign, which was promoted by the World Health Organization (WHO) in the 1960s and 1970s, represents a major milestone in medical history [1,2]. Smallpox vaccination was suspended due to several cases of adverse manifestations from the vaccine [4] Despite this remarkable victory against VARV, the suspension of smallpox vaccination led to the emergence of a generation that is susceptible to other OPV species [4]. This fact may explain the emergence of zoonotic OPV species such as Cowpox virus (CPXV) in Europe [5]; Monkeypox virus (MPXV) [6], which occurs naturally in Africa and was recently introduced in the USA; and, ironically, VACV in rural areas of Brazil and India, which has been associated with exanthematic outbreaks in both humans and cattle [7,8,9]. Regardless of its origins, the VACV strains have proven to be well-adapted to Brazilian rural and wild environments and have been detected in bovines, humans, rodents, monkeys, horses and other vertebrate species [8,12,13,14]
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