Coxsackievirus B4: in vitro genetic markers and virulence.

The relationship of virulence to mice of the coxsackievirus B4 prototype JBV strain and selected mutants to several in vitro genetic markers has been examined. Markers studied include the t, d, DS, DEAE-D, and guanidine resistance (G), markers and a plaque size marker, here designated PS. The JVB strain was found to have the characteristics t-, d-, DS+, DEAE-D+, G-, PS+ and to be virulent when inoculated by the intraperitoneal route into suckling CD-1 mice (log titer/LD50 = 6.4/6.0). One naturally occurring mutant strain (characteristic = t-, d+, DS+, G-, PS+ was selected by terminal end point dilution and found to be virulent (log titer/LD50 = 7.0/6.0). Passage of the JVB population in the presence of guanidine hydrochloride (75 micrograms/ml) allowed selection of avirulent, guanidine resistant mutants with characteristics of t-, d-, DS+, DEAE-D+, G+. These mutants produced only small plaques (1.0-1.6 mm) and were designated PS-. The prototype and other selected strains that contained both large plaque and small plaque variants were characterized as PS+ and were invariably virulent. Although a variance in the d character has been demonstrated in some of the above strains, we conclude that virulence and the in vitro genetic markers t, d, DS, and DEAE-D are not related in our coxsackievirus B4 CD-1 mouse system. A relationship between plaque size (PS) and/or guanidine resistance (G+) of selected strains of coxsackievirus B4 and avirulence has been demonstrated in this system.