Emergence and reemergence of vaccinia-like viruses: global scenario and perspectives

Abstract

Among the members of the genus Orthopoxvirus (OPXV), vaccinia virus (VACV), the type species of the genus is a double-stranded DNA virus, belongs to the subfamily Chordopoxvirinae of the family Poxviridae. The causative agents of smallpox, VACV and Variola virus are mutually immunogenic and the type species of Orthopoxvirus, cause only mild complications in humans. Therefore, the VACV was used as a smallpox vaccine world over under mass immunization program promoted by World Health Organization, which lead to the variola eradication globally in 1979. Since then, no vaccination of human population has been carried out; however, vaccination has been continued for at-risk laboratory workers, military personnel and others working with recombinant VACV or other non-variola orthopoxviruses (OPXVs). There has now been a surge in the development of safer smallpox vaccines and understanding of the biology of VACV necessitating re-use of this vaccine in most vulnerable population, because of rise in bioterrorist threats globally. Also, globally there has been the emergence and re-emergence of vaccinia-like viruses (VLVs) in Brazil, buffalopox viruses in Egypt, Indonesia, India and its neighbouring countries like Nepal, Pakistan. Bioterrorism as well as emergence and re-emergence of the VLVs constitute a concern as 50 % of the population globally (40 % in USA) <30 years are unvaccinated and most vulnerable for smallpox reemergence. Thus, the search for new generation safer smallpox vaccine entails review of biology of VLVs in the smallpox-free world. In this review, we present occurrence of VLVs in the world with exhaustive discussion particularly on the emergence and re-emergence of these viruses in India and Brazil where VLVs are sufficiently studied.

Keywords: Buffalopox; Emergence and reemergence; Vaccinia virus; Vaccinia-like viruses; Zoonosis.

Fig. 1

World-wide distribution of Vaccinia-Like Viruses in Brazil (purple), India (red), Nepal (pink), Pakistan (green), Egypt (yellow) and Indonesia (brick red). (Color figure online)

Fig. 2

a Phylogenetic analysis based on the deduced aa sequence of hemagglutinin (HA) gene. a Vaccinia and Vaccinia-Like Viruses (b) members of OPrthopoxviruses. Un-rooted tree was constructed using neighbor-joining method of MEGA version 4. Numbers on the tree branches represent the bootstrap support calculated per 1,000 bootstrap replicates. The scale bar represents the aa substitutions per site. BPXV isolates BPXV 2-04C (Cow); BPXV 9-04C (Cow); BPXVC 17-04C (Cow); BPXVC 13-03C (Cow); BPXV 14-03C (Cow); BPXV 1-04B (Buffalo); BPXV 18-04B (Buffalo) analyzed with various species/strains of various members of OPXVs are given; vaccinia virus (VACV) strain-WR, strain-Lister (Li), strain-Modified Vaccinia Ankara (MVA), strain-Acambis clone 3 (Aca), strain-Tian Tan (TT), VAVC-Copenhagen, VAVC-Duke, VAVC-Ankara, Rabbitpox virus (RPV or RPXV), strain-U23 (U23), CPXV strain-GRI90, CPXV-stain Brighton Red (BR), ARAV, MPXV strain-Zaire 79 (ZR), strain-Walter Reed (WR), Camelpox virus (CMLV) strain-CMS, strain-M96, Variola virus (VaV) strain-Garcia 1966 (GAR66), strain-Bangladesh 1975 (BAN75), strain-India 1967 (IND67). BAV, Belo Horizonte virus (VBH), Guarani P1 virus (GP1V), Guarani P2 virus (GP2V), Passatempo virus (PSTV), CTGV

Fig. 3

Phylogenetic analysis of Buffalopox virus (PBXV) isolates from India and other members of OPXVs based on deduced aa sequence of C18L gene. Details are same as mentioned for Fig. 2