Pathogenesis of Autographa californica multiple nucleopolyhedrovirus in fifth-instar Anticarsia gemmatalis larvae

Abstract

We have investigated infection and pathogenesis of Autographa californica multiple nucleopolyhedrovirus (AcMNPV) in Anticarsia gemmatalis (velvetbean caterpillar) larvae using a lacZ recombinant virus (AcMNPV-hsp70/lacZ) to track the temporal progression of infection in the midgut intestine and haemocoel. A. gemmatalis was highly resistant to fatal infection by occlusion bodies (OBs; LD 50 .5.5¾105 OB) and budded virus (BV; LD 50 .3¾10 5 BV) administered via oral and systemic routes, respectively. Orally administered occlusion-derived virus (ODV) efficiently attached and fused to midgut cells; however, high levels of infectioninduced apoptosis limited infection in the midgut. Transcriptional analysis of AcMNPV genes expressed in the midgut of OB-inoculated A. gemmatalis larvae showed high levels of mRNA encoding the major capsid protein VP39 in the absence of immediate-early transactivator 1 (ie-1) expression. In the midgut, virus was efficiently transferred from infected midgut epithelial cells to nearby tracheolar cells and circulating haemocytes to initiate systemic infection in the haemocoel. However, haemocoelic BV did not efficiently disseminate infection and only cuticular epidermal cells displayed high levels of viral infection. Flow cytometry analysis of haemocytes isolated from BV-inoculated A. gemmatalis larvae showed low-level expression of the BV envelope protein GP64 on the cell surface, suggesting that A. gemmatalis haemocytes have a limited capacity for amplifying virus. These results show that AcMNPV is not an effective biological control agent for limiting crop damage caused by A. gemmatalis larvae.

Inactivation of the budded virus of Autographa californica M nucleopolyhedrovirus by gloverin

“…After incubation for 1 h at 28 °C, the inocula was removed, methyl cellulose (1.5 g/ml) dissolved in TNM-FH media added to each well and the plate incubated in a humidified chamber at 28 °C. After 3 days, the cells were fixed with formaldehyde, rinsed three times with PBS, processed using X-gal to develop the blue lacZ-positive plaques, as previously described (Chikhalya et al, 2009) and the plaques counted using a Leica MZ12.5 stereomicroscope. This experiment was repeated at least three times on separate days and the resulting data combined to calculate the mean and SEM for each treatment.…”

Recent Advances in Our Knowledge of Baculovirus Molecular Biology and Its Relevance for the Registration of Baculovirus-Based Products for Insect Pest Population Control

“…Larvae of Anticarsia gemmatalis (velvetbean caterpillar) are highly resistant to AcMNPV. Infection was shown to be blocked at early stages of replication where, even though ODVs successfully entered the midgut cells and were rechanelled to tracheal cells, the immediate early gene, ie-1, was not transcribed (Chikhalya et al, 2009). The inhibition of this essential transactivator resulted in the disruption of the gene expression cascade resulting in a failure to produce infectious viral particles.…”

Caracterización biológica y molecular de genes involucrados en la virulencia de baculovirus de importancia agronómica

“…gemmatalis vía per os, solo a muy elevadas dosis (DL 50 > 5.5 x 10 5 OB/larva) y solo unos pocos tipos celulares parecen permitir la replicación viral cuando este virus es administrado vía per os o intrahemócelica a dosis también elevadas (Chikhalya et al, 2009).…”

“…La falta de infección vía per os en larvas de A. gemmatalis y S. frugiperda determinada en este trabajo podría ser debida a la utilización de dosis insuficientes como para causar la infección, aunque probablemente este inconveniente podría estar relacionado con la interaccion entre el ODV y receptores presentes en las células del intestino del hospedador (Haas-Stapleton et al, 2005). En cambio, el uso de BVs inyectados vía intrahemocélica mostraron resultados coincidentes con lo descrito por otros autores (Clarke & Clem, 2002;Chikhalya et al, 2009;Haas-Stapleton et al, 2003;2005).…”