Successful competition in translation by the flavivirus Kunjin with poliovirus during co-infections in Vero cells.

Infection with poliovirus effectively inhibited the translation of Vero cell messengers (carrying type 1 or type 2 caps at the 5' end) and of influenza virus messengers (type 1 caps) in co-infections. In contrast, Kunjin virus RNA (type 1 caps) and Semliki Forest virus RNA (a togavirus, with type 0 caps) continued to be translated in the presence of co-infecting poliovirus. Translation of Kunjin virus RNA was also unaffected during co-infections with either influenza virus or Semliki Forest virus. Guanidine treatment effectively blocked poliovirus replication only, but the inhibitory effect on translation of cell messengers and influenza virus messengers was still observed, indicating that this effect was not caused by competition in translation with poliovirus messengers. It was therefore concluded that the observed inhibition was most likely caused by cleavage of the p220 subunit of the cap binding protein (CBP) complex of the cell normally required for translation of capped messengers, as reported by others. However, Kunjin virus RNA could be efficiently translated apparently in the absence of a functional CBP complex, except when its secondary structure was stabilized by hypertonic salt in the culture medium.