Single-Point Mutations within the Coxsackie B Virus Receptor-Binding Site Promote Resistance against Soluble Virus Receptor Traps.

Coxsackie B viruses (CVB) cause a wide spectrum of diseases, ranging from mild respiratory syndromes and hand, foot, and mouth disease to life-threatening conditions, such as pancreatitis, myocarditis, and encephalitis. Previously, we and others found that the soluble virus receptor trap sCAR-Fc strongly attenuates CVB3 infection in mice. In this study, we investigated whether treatment with sCAR-Fc results in development of resistance by CVB3. Two CVB3 strains (CVB3-H3 and CVB3 Nancy) were passaged in HeLa cells in the presence of sCAR-Fc. The CVB3-H3 strain did not develop resistance, whereas two populations of CVB3 Nancy mutants emerged, one with complete (CVB3) and one with partial (CVB3) resistance. DNA sequence alignment of the resistant virus variant CVB3 with CVB3 Nancy revealed an amino acid exchange from Asn(N) to Ser(S) at position 139 of the CVB3 capsid protein VP2 (N2139S), an amino acid predicted to be involved in the virus's interaction with its cognate receptor CAR. Insertion of the N2139S mutation into CVB3-H3 by site-directed mutagenesis promoted resistance of the engineered CVB3-H3 to sCAR-Fc. Interestingly, development of resistance by CVB3-H3 and the exemplarily investigated CVB3-clone 2 (CVB3) against soluble CAR did not compromise the use of cellular CAR for viral infection. Infection of HeLa cells showed that sCAR-Fc resistance, however, negatively affected both virus stability and viral replication compared to that of the parental strains. These data demonstrate that during sCAR-Fc exposure, CVB3 can develop resistance against sCAR-Fc by single-amino-acid exchanges within the virus-receptor binding site, which, however, come at the expense of viral fitness. The emergence of resistant viruses is one of the most frequent obstacles preventing successful therapy of viral infections, representing a significant threat to human health. We investigated the emergence of resistant viruses during treatment with sCAR-Fc, a well-studied, highly effective antiviral molecule against CVB infections. Our data show the molecular aspects of resistant CVB3 mutants that arise during repetitive sCAR-Fc usage. However, drug resistance comes at the price of lower viral fitness. These results extend our knowledge of the development of resistance by coxsackieviruses and indicate potential limitations of antiviral therapy using soluble receptor molecules.