Pathogenesis of Lymantria dispar multiple nucleopolyhedrovirus in L. dispar and mechanisms of developmental resistance

Abstract

Lymantria dispar has a long historical association with the baculovirus Lymantria dispar multiple nucleopolyhedrovirus (LdMNPV), which is one of the primary population regulators of L. dispar in the field. However, host larvae exhibit strong developmental resistance to fatal infection by LdMNPV; the LD 50 in newly moulted fourth instars is 18-fold lower than in the middle of the instar (48-72 h post-moult). Using a recombinant of LdMNPV expressing lacZ, we examined the key steps of pathogenesis in the host to explore mechanisms of developmental resistance. At the midgut level, we observed reduced primary midgut infections in mid-fourth instars, indicating increased sloughing of infected cells. Additional barriers were observed as the virus escaped the midgut. Mid-fourth instars had higher numbers of melanized foci of infection associated with the midgut, apoptotic tracheal epidermal cells and haemocytes, and reduced numbers of infected haemocytes later in infection. Our results show that the co-evolutionary relationship between L. dispar and LdMNPV has resulted in both midgut-based and systemic antiviral defences and that these defences are age-dependent within the instar. This age-related susceptibility may contribute to how the virus is maintained in nature and could influence management of L. dispar by using the virus.

Wolbachia-Mediated Antiviral Protection in Drosophila Larvae and Adults following Oral Infection

“…A wide range of genes coordinate the disintegration of larval structures, where some larval organs are histolyzed and major new growth takes place, altering the morphology and in some cases pathogen susceptibility (43)(44)(45). Pathogen susceptibility is often age or life stage dependent and can have a large effect on population dynamics, viral spread, and maintenance of the virus within the population (45)(46)(47)(48). Studies focusing on the antiviral effects of Wolbachia have to date been conducted solely on adult flies and mosquitoes, without consideration of other developmental stages.…”

Interactions between an injected polydnavirus and per os baculovirus in gypsy moth larvae

“…Washburn et al (1996) strongly implicated the PDV-mediated abrogation of hemocytic encapsulation of infected cells as the reason for a rapid spread of AcMNPV in a ''highly refractory'' host, H. zea. Other work by McNeil et al (2010b) does not lend strong support for that mechanism achieving the same protective role in the gypsy moth-LdMNPV system. They found strong evidence for some encapsulation and melanization after LdMNPV challenge, but no obvious correlation between these and observed mortality.…”

Detection and kinetic analysis of Epinotia aporema granulovirus in its lepidopteran host by real-time PCR

“…However, the lack of an accurate method to quantify the number of viral copies in a given sample has impeded the investigation of different aspects of disease development. The in vivo increase in viral titer is extremely variable among baculovirus-host systems and is affected by multiple factors, such as concentration of virus inoculum, temperature and host developmental stage [10,14,15,20]. Most of these studies have focused on the NPV group, while information concerning GV is still limited.…”