Pan Qinjian,Shikano Ikkei, Felton Gary W, Liu Tong-Xian, Hoover Kelli.Host permissiveness to baculovirus influences time-dependent immune responses and fitness costs

Host permissiveness to baculovirus influences time-dependent immune responses and fitness costs.

Pan Qinjian,Shikano Ikkei, Felton Gary W, Liu Tong-Xian, Hoover Kelli

Insect science

DOI:10.3390/genes11010081

Abstract :Insects possess specific immune responses to protect themselves from different types of pathogens. Activation of immune cascades can inflict significant developmental costs to the surviving host. To characterize infection kinetics in a surviving host that experiences baculovirus inoculation, it is crucial to determine the timing of immune responses. Here, we investigated time-dependent immune responses and developmental costs elicited by inoculations from each of two wild-type baculoviruses, Autographa californica multiple nucleopolyhedrovirus (AcMNPV) and Helicoverpa zea single nucleopolyhedrovirus (HzSNPV), in their common host H. zea. As H. zea is a semi-permissive host of AcMNPV and fully permissive to HzSNPV, we hypothesized that there are differential immune responses and fitness costs associated with resisting infection by each virus species. Newly molted fourth-instar larvae that were inoculated with a low dose (LD15 ) of either virus showed significantly higher hemolymph FAD-glucose dehydrogenase (GLD) activities compared to the corresponding control larvae. Hemolymph phenoloxidase (PO) activity, protein concentration and total hemocyte numbers were not increased, but instead were lower than in control larvae at some time points post-inoculation. Larvae that survived from either virus inoculation exhibited reduced pupal weight; survivors inoculated with AcMNPV grew slower than the control larvae, while survivors of HzSNPV pupated earlier than control larvae. Our results highlight the complexity of immune responses and fitness costs associated with combating different baculoviruses. This article is protected by copyright. All rights reserved.