CHEMOKINE HOMOLOG OF MOLLUSCUM-CONTAGIOSUM VIRUS - SEQUENCE CONSERVATION AND EXPRESSION

An analysis of the complete Molluscum contagiosum virus (MCV-I) genome sequence revealed a 104-amino-acid open reading frame (MC148R) that i s structurally related to the beta (CC) family of chemokines. The pred icted MCV chemokine homolog (MCCH) has a deletion in the NH2-terminal activation domain, suggesting the absence of chemoattractant activity. The principal objectives of the present study were to determine wheth er: (i) MCCH is conserved in independent isolates of MCV-1 and MCV-2; (ii) MCCH mRNA is expressed in vivo; and (iii) the MCCH protein is sec reted from mammalian cells. The nucleotide sequence of the MCCH gene f ocus was determined for 27 isolates of MCV-1 and 2 of MCV-2 obtained f rom 29 MCV-infected individuals. In each case, the characteristic CC s equence, the NH2-terminal deletion, and the length of the open reading frame were conserved, although there were some, mostly conservative, amino acid substitutions. Since MCV cannot be propagated in cell cultu re, mRNA was synthesized in vitro by the early transcription apparatus in purified MCV virions. MCCH RNA was amplified by RT-PCR; the sequen ce included the complete open reading frame and extended 40 to 50 nucl eotides past the first poxviral termination signal (TTTTTNT). similar RT-PCR results were obtained using total cellular RNA derived from MCV -infected tissue specimens. Finally, the MCCH open reading frame was e xpressed in a vaccinia virus Vector and the predicted size polypeptide was secreted into the medium, as determined by Western blotting. Take n together, our data support the prediction that MCV expresses a secre ted chemokine homolog that could antagonize the inflammatory response in vivo. (C) 1998 Academic Press.