Poxviruses of Insects: Entomopoxvirinae

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Entomopoxvirinae, a subfamily of Poxviridae encompasses viruses of insects with structural and genomic features as well as a replicative cycle similar to poxviruses of chordates. Entomopoxviruses (EPVs) are distinguished by the synthesis of an occlusion body, spheroid, into which mature virions are occluded late in the infection cycle. To date, seven EPV genomes have been sequenced with sizes ranging from 228.1 to 307.7 kb, and as in other poxviruses, the genome contains a conserved central region and variable termini that also contain the typical inverted terminal repeats. EPVs initiate infection in larval midgut cells followed by haemocytes that spread the virus to other permissive tissues, primarily fat tissues. This is in contrast to baculoviruses (BVs) that use the trachea as a conduit to disseminate infection. Even though EPVs and BVs are from varied ancestral origins, they occupy very similar ecological niches. It was shown that there was gene acquisition convergence between both group of viruses. To date, EPVs have not been used as biological control agents, primarily because of the long time it takes to kill the larval host.