A Guinea pig cytomegalovirus resistant to the DNA maturation inhibitor BDCRB

Abstract

Herpesvirus DNA packaging is an essential step in virion morphogenesis and an important target for antiviral development. The halogenated benzimidazole 2-bromo-5,6-dichloro-1-β-d-ribofuranosyl-1H-benzimidazole (BDCRB) was the first compound found to selectively disrupt DNA packaging. It has activity against human cytomegalovirus as well as guinea pig cytomegalovirus. The latter provides a useful small animal model for congenital cytomegalovirus infection. To better understand the mechanism by which BDCRB acts, a guinea pig cytomegalovirus resistant to BDCRB was derived and characterized. An L406P substitution occurred within GP89, a subunit of the complex that cleaves and packages DNA, but transfer of this mutation to an otherwise wild type genetic background did not confer significant BDCRB resistance. The resistant virus also had a 13.4-kb deletion that also appeared to be unrelated to BDCRB-resistance as a virus with a similar spontaneous deletion was sensitive to BDCRB. Lastly, the BDCRB-resistant virus exhibited a dramatic increase in the number of reiterated terminal repeats at both genomic termini. The mechanism that underlies this change in genome structure is not known but may relate to the duplication of terminal repeats that is associated with DNA cleavage and packaging. A model is presented in which BDCRB impairs the ability of terminase to recognize cleavage site sequences, but repeat arrays overcome this impairment by presenting terminase with multiple opportunities to recognize the correct cleavage site sequences that lie within the repeats. Further elucidation of this phenomenon should prove valuable for understanding the molecular basis of herpesvirus DNA maturation and the mechanism of action of this class of drugs.

Anti-CMV therapy, what next? A systematic review

“…However, more recently, a GPCMV resistant to BDRCRB was generated and characterized. Genetic alterations were reported: an L406P substitution in GP89, the HCMV UL89 homolog; a 13.4 kb internal deletion of the GP131-GP143 non-essential ORFs; and a dramatic increase in the number of iterations of a 1 kb terminal repetitive sequence, from 0 or 1 to up to 9 at either genomic end ( Ourahmane et al, 2018 ).…”

“…Furthermore, deletion of the E region of HindIII is unlikely to contribute directly to resistance to BDCRB. Thus, the accumulation of terminal repeats could be a response to BDCRB pressure and the resulting increase in genome length resulted in compensatory deletion of the HindIII E region ( Ourahmane et al, 2018 ).…”