Viral interference: A review

The inhibition of viral reproduction caused by previous exposure of cells to another virus is popularly known as viral interference or superinfection resistance. The primary virus infecting the cell prevents the replication of secondary virus in that cell, thus making viral interference a very important phenomenon in viral world. It may be simplified by stating that the virus can suppress the shedding of a new virus of the homologous or heterologous type which enters the cell. The mechanisms proposed to explain viral interference may be briefly described as competing by attachment interference where receptors for the superinfecting virus are reduced or blocked, competing for intracellular components required for replication of the host machinery and virus induced interferon interference. The intensity of viral interference however depends on several factors such as adaptation of viruses to host species, pathogenicity of viruses, time of co-infection, and environmental factors. This review highlights the importance of testing of interfering viruses during the molecular screening and viral isolation attempts of infected poul¬try flocks and other animals so as to identify the conse¬quences of interference during coinfection.