The Blocking Effect of West Nile Virus on Production of Sarcoma by Rous Virus in Chickens

Abstract

A system has been described wherein a non-oncogenic arbovirus B, West Nile virus (WNV), blocked tumor development by an oncogenic one, Rous sarcoma virus (RSV), in the subcutaneous wing web tissue of the White Leghorn chicken. The blocking effect was determined by measuring the increase in tumor latent period and by the incidence (percentage) of chickens showing absence of the sarcoma (complete blockade). The effect was time dependent: a) an increase in latent period and some incidence of complete blockade were seen on simultaneous inoculation of the virus pair; b) a marked increase in latent period and a high incidence of complete blockade were obtained if the RSV was delayed 24 to 120 hr post WNV inoculation; c) at 144 hr the effect was diminished; d) it disappeared between 168 and 240 hr post WNV injection. The effect was transient: chickens showing complete blockade were susceptible to sarcoma production if later challenged with RSV alone. The blocking effect could be obtained by inoculating the RSV at a site distant from that of previously injected WNV. It was RSV concentration dependent. The mechanism(s) underlying the blocking effect is (are) unknown.