Pseudotyping of budded virus of AcMNPV with P74 from ocludded-derived virus

ALFONSO VICTORIA; LOPEZ MARÍA GABRIELA; 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 are pathogens of insects. Two distinct infectious phenotypes exist in their infection cycle: occlusion-derived viruses (ODVs) and budded viruses (BVs). ODVs are responsible for primary infection in insect hosts because of their high per os infectivity. On the contrary, BVs poorly infect endothelial gut cells but propagate the infection in the tissues of insects with a high efficiency. P74 is one of the most important proteins from ODVs, which participates in the attachment of this viral phenotype to endothelial cells in the midgut. We evaluated the possibility of pseudotyping budded viruses of Autographa californica multiple nucleopolyhedrovirus with two versions of P74 and its effect on their oral infectivity. One of them consisted in the display of a portion of P74 that is thought to be exposed on the surface of ODVs fused to GP64 in BVs peplomers (AcP74exSup). The second strategy consisted in distributing P74 on the viral envelope, anchoring it to the cell membrane by its own transmembrane domain, taking advantage of baculoviruses passively acquiring P74 during the budding process (AcP74Sig). Initially we demonstrated, by an immunofluorescence assay, the localization of P74 on the surface of cells infected with both recombinant baculoviruses AcP74Sig and AcP74exSup, indicating that, as expected, P74 was anchored to membranes. Furthermore, the protein was clearly detected in purified budded baculoviruses, although the immunoblotting results suggested that P74 was poorly represented in the virions. Growth curves performed in cultured cells revealed that modified viruses retain the ability to infect cells in a secondary infection on the same level as wt; nevertheless, budded viruses displaying P74 were even less orally infectious than wild type viruses in Rachiplusia nu larvae, suggesting that the presence of P74 in the membrane of budded virions interferes with the mechanism used by this phenotype to infect midgut cells.