Main Article Content
Viruses have proven to be of major importance as infectious agents and as models for molecular studies. The viruses provide simple model systems that can be used to address many complex biological problems. The study of virus-virus interactions within host cells has contributed greatly to our understanding of gene function and has provided much knowledge concerning both theorganization and the expression of genetic information.When a single cell infected by multiple viruses, hybrid progeny can be produced that contain mixtures of genetic information of co-infecting parents. Besides this verity of interactions, both genetic and nongenetic, mayoccur between two viruses during coinfection. The coinfected hybrid progeny may occur due to genotypic mixing,phenotypic mixing,enhancement,interference and/or complementation.
In this reviewI represent different type of direct and indirect interactions among different plant viruses, animal viruses and bacterial viruses when they coinfect their respective host cell. In direct interaction nucleic acids or proteins of one virus physically interact with the genes or gene products of a coinfecting virus and this is mediated by complementation to helper dependent virus, phenotypic mixing of coinfected virus, superinfection exclusion, genomic recombination and/or heterologous transactivation. On the other hand, during indirect viral-viral-interaction alterations in progeny virus resulting from the host environment created by pre-existing or simultaneous coinfections are explored and this is mainly responsible for alteration of host susceptibility due to breakdown of physical barriers and/or due to altered receptor expression.