Variability in the integrity of human enteroviruses exposed to various simulated in vivo environments.

We exposed representatives of different enteroviruses to treatments imitating various in vivo environments that they face during infection. Short-term treatment in trypsin or human intestinal fluid regularly resulted in a cleavage of the capsid protein VP1, and in some cases of other capsid proteins as well. Infectivity of the virus preparations was usually not affected but there were two exceptions. Coxsackievirus A9 retained its infectivity as tested in RD cells but showed reduced infectivity in GMK cells, as reported previously. More strikingly, the titre of echovirus 22 was decreased by 2 logs. Overnight incubation in intestinal fluid affected the infectivity of all tested viruses, including polioviruses and coxsackievirus B4. Echovirus 22 and, to a lesser extent, coxsackievirus A9 were also partially inactivated by faecal suspension. After 2 h exposure to pH 2 at 37 degrees C all tested viruses retained their infectivity, but after 24 h all were inactivated. We conclude that the stability of enteroviruses exposed to various natural environments varies significantly, and that echovirus 22, no more classified in the genus Enterovirus, appears relatively more sensitive in body fluids.