CHARACTERIZATION OF THE GENE ENCODING THE A-TYPE INCLUSION PROTEIN OFCAMELPOX VIRUS AND SEQUENCE COMPARISON WITH OTHER ORTHOPOXVIRUSES

A gene was identified in camelpox virus strain CP-1 that is similar to the 160K gene of cowpox virus strain Brighton (BR) that encodes the A -type inclusion body protein (ATIP). The CP-1 gene was mapped. sequenc ed. and the presence of the ATIP-specific mRNA was demonstrated. The o pen reading frame 2178 nucleotides (nt)! was found at a similar posit ion in the CP genome as the one reported for the cowpox virus 160K ATI gene. DNA sequence comparison revealed a deletion of two adjacent ade nine residues relative to cowpox virus BR, generating a reading frame shift accompanied by the formation of a translational stop codon. An i dentical deletion has been described for vaccinia virus strain Western Reserve. The DNA sequence of the corresponding region of monkeypox vi rus strain Copenhagen revealed a deletion leading to a putative stop c odon 75 nt upstream of the same stop codons in the camelpox and vaccin ia virus genes. These findings are consistent with the expression of t runcated ATIPs, of 94K in vaccinia and camelpox viruses and of 92K in monkeypox virus. In addition, a deletion of 789 bp could be localized downstream of the ATI open reading frame in camelpox virus isolates of different origin. This causes the transcription of a shortened ATI-sp ecific mRNA (3.7 kb) relative to vaccinia and cowpox viruses (both 4.5 kb). The similarity observed in ATIP-encoding and flanking sequences might suggest that vaccinia and camelpox viruses are descended from a common ancestor.