Smallpox abstract: Variola morphogenesis effected by a by an erb-B Tyrosine Kinase inhibitor: possible therapeutic functions

Overview

Tiara Harms¹, Hailin Yang², Mikyung Kim², Sung-Kwon Kim³, Ellis Reinherz², Raymond Welsh³, and Inger Damon¹

¹Centers for Disease Control and Prevention, Atlanta, United States of America
²Dana-Farber Cancer Institute and Department of Medicine, Harvard Medical School, Boston, MA, United States of America
³Department of Pathology, University of Massachusetts Medical Center, Worchester, MA, United States of America.

The variola major strain Bangladesh ORF D4R, encoding the homolog of the vaccinia virus growth factor (VGF), was evaluated as a potential therapeutic target. VGF, which demonstrates areas of significant homology with the epidermal growth factor (EGF) superfamily, previously suggested to be a ligand for vaccinia cell entry, mediates host cell proliferation and is a viral virulence factor in vivo.

A 40 amino acid region of the variola protein (SPGF), homologous to the active moiety of EGF, was cloned, expressed, and found to be functional as a growth factor. Neither SPGF, nor two monoclonal antibodies (mAbs) raised against SPGF could block the ability of variola to form plaques on primary or transformed cell lines.

An irreversible inhibitor of erb-B receptor tyrosine kinase pathways, CI-1033, in a dose-dependent manner, dramatically reduces the size of individual variola plaques and significantly (p<0.05) decreases="" the="" number="" of="" comets="" at="" ci-1033="" concentrations="" of="" ≥500nm.="" single-step="" growth="" curves,="" using="" two="" different="" cell="" lines,="" exhibit="" a="" delay="" and="" absolute="" decrease="" in="" extracellular="" enveloped="" virus="" (eev)="" formation,="" as="" well="" as="" some="" decrease="" in="" cell="" associated="" virus="" (cav)="">

No difference was found in viral DNA accumulation by use of quantitative orthopoxvirus PCR. Murine intranasal vaccinia challenge studies demonstrate a protective benefit of CI-1033 against SPGF, and this benefit is more pronounced when an intracellular mature virus (IMV) neutralizing mAb is used. These results suggest that CI-1033 blocks specific step(s) in viral morphogenesis and may be of therapeutic benefit.

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