DESCRIPTION OF A NOVEL SINGLE MUTATION IN ACMNPV POLYHEDRIN GENE THAT ORIGINATES ABNORMALLY LARGE CUBIC POLYHEDRA

LOPEZ MARÍA GABRIELA; ALFONSO VICTORIA; CARRILLO ELISA; TABOGA OSCAR

Gramado, RS, Brazil

Congreso; XXI National Meeting of Virology and V Virology meeting of Mercosul; 2010

Sociedade Brasileira de Virologia

Baculoviruses belong to a broad family of virus pathogens of insects, which are specifically occluded within robust crystalline particles. This occlusion bodies (OB) act as protective packages allowing infectious virions to survive for long periods in harsh environments, protecting them from UV irradiation and desiccation. A point mutation in the Autographa californica Multiple Nucleopolyhedrovirus (AcMNPV) polyhedrin gene was found that originated abnormally large cubic polyhedra in packaging cell lines. In order to characterize this phenotype we constructed a mutant baculovirus, AcPOLE44G, in which a single change of residue 44 from E to G was introduced. The infection of Sf9 cells with AcPOLE44G corroborated that this mutation and no other alterations in the AcMNPV genome was responsible of the generation of abnormal occlusion bodies. Although baculoviral proteins are detected inside mutant polyhedra, electron microscopy demonstrated that large polyhedrin crystals allow few or no occlusion of virions, in accordance to previous reports of similar point mutations in polh gene. The infectious nature of the abnormal occlusion bodies was analyzed by oral infection of Rachiplusia nu larvae and, in comparison to wt polyhedra, the mutant inoculum resulted less infectious, confirming the occlusion deficiencies of AcPOLE44G baculovirus. Altogether, these results confirm that substitution in aa 44 of AcMNPV polyhedrin interferes with a correct assembly of polyhedrin and affects virus occlusion.