Densoviruses (DNV) are insect parvoviruses sharing with that group a non enveloped 20-25 nm icosaedric capsid and a single stranded DNA genome. Since they are lethal for several insects at larval stages, including agronomical pests and insects vector-borne diseases, the question of their use as biopesticides is revisited. As a model, we studied the interaction of Junonia coenia Densovirus (JcDNV) and one permissive host, Spodoptera frugiperda (Lepidoptera, Noctuidae). The larvae get infected by the oral route, ingesting viral particles contaminating food. The success of the infection first depends on the penetration of the virus through the midgut epithelium. In order to study this early step, we performed a cellular and physiological analysis of the entry of a Cy3-labelled JcDNV through S. frugiperda midgut in vitro. Primary cultures of midgut cells were developed to detect the sites of penetration and the intracellular pathway followed by Cy3-JcDNV. The virus was unable to infect stem cells and differentiated goblet cells, while in incubated columnar cells, whether at an early phase of differentiation or fully differentiated, the virus was visible after 10 minutes in the basolateral membrane and in microvilli, and after 30 minutes within the cytoplasm. Virus particles were apparent as spots, suggesting that they could be distributed in intracellular compartments. S. frugiperda midguts were then isolated from fifth instar larvae, mounted between Ussing chambers and incubated with JcDNV added to the luminal side of the epithelium. After 10 minutes of exposition, the virus induced a significant decrease of the paracellular electrical resistance, an indication that ions moved more rapidly through the aqueous channels formed by the intercellular junctions. The confocal image of whole-mount midguts, isolated and incubated for 10 minutes with luminal Cy3-JcDNV, clearly showed the presence of the virus in the enterocytes’ cytoplasm.
Cell penetration and electrophysiological effects of an insect parvovirus in the midgut of Spodoptera frugiperda / G. Cermenati, L. Fiandra, M. Casartelli, B. Giordana, M. Ogliastro. ((Intervento presentato al 1. convegno International Symposium on Insect Midgut Biology tenutosi a Guangzhou (Cina) nel 2008.
Cell penetration and electrophysiological effects of an insect parvovirus in the midgut of Spodoptera frugiperda
G. Cermenati;L. Fiandra;M. Casartelli;B. Giordana;
2008
Abstract
Densoviruses (DNV) are insect parvoviruses sharing with that group a non enveloped 20-25 nm icosaedric capsid and a single stranded DNA genome. Since they are lethal for several insects at larval stages, including agronomical pests and insects vector-borne diseases, the question of their use as biopesticides is revisited. As a model, we studied the interaction of Junonia coenia Densovirus (JcDNV) and one permissive host, Spodoptera frugiperda (Lepidoptera, Noctuidae). The larvae get infected by the oral route, ingesting viral particles contaminating food. The success of the infection first depends on the penetration of the virus through the midgut epithelium. In order to study this early step, we performed a cellular and physiological analysis of the entry of a Cy3-labelled JcDNV through S. frugiperda midgut in vitro. Primary cultures of midgut cells were developed to detect the sites of penetration and the intracellular pathway followed by Cy3-JcDNV. The virus was unable to infect stem cells and differentiated goblet cells, while in incubated columnar cells, whether at an early phase of differentiation or fully differentiated, the virus was visible after 10 minutes in the basolateral membrane and in microvilli, and after 30 minutes within the cytoplasm. Virus particles were apparent as spots, suggesting that they could be distributed in intracellular compartments. S. frugiperda midguts were then isolated from fifth instar larvae, mounted between Ussing chambers and incubated with JcDNV added to the luminal side of the epithelium. After 10 minutes of exposition, the virus induced a significant decrease of the paracellular electrical resistance, an indication that ions moved more rapidly through the aqueous channels formed by the intercellular junctions. The confocal image of whole-mount midguts, isolated and incubated for 10 minutes with luminal Cy3-JcDNV, clearly showed the presence of the virus in the enterocytes’ cytoplasm.
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