Nanoparticle–Virus Complex Shows Enhanced Immunological Effect Against Baculovirus

Abstract

Insects protect themselves from majority of infections by a non-specific innate immune system (present in both vertebrates and invertebrates). Bombyx mori nuclear polyhedrosis virus (BmNPV), a baculovirus, causing the deadly grasserie disease is a scourge to silkworm industry and we report here the first success in combating this disease with the help of a nanosilica-virus complex. Hydrophobic aluminium silicate nanoparticles were mixed with live BmNPV in vitro. This mixture was injected into one day old 5th instar silkworm larvae (into the hemocoel at the third abdominal spiracle) before challenging the larvae with live BmNPV via a second injection. This led to substantial enhancement of longevity in the diseased silkworm larvae and 35 +/- 5.3% larvae completed their lifecycle (i.e., formed normal pupae and enclosed as moth). On the other hand, 100% larvae infected with BmNPV alone died within 36 hours. The larvae treated with nanoparticles before infection had a longer lifespan but all of them eventually succumbed, not a single larva metamorphosed to adult stage. Results suggest two pathways of host protective response--one mediated by nanoparticlealone and the second, more important, via non-specific innate immunological mechanism. AFM and confocal studies show that nanoparticles alter 3-D molecular structure of the virus envelope. Possibly this exhibits novel potent epitope(s) which stimulate(s) anti-viral machinery in infected silkworm larvae. SDS-PAGE results suggest that 39 KDa viral protein is the major target of the nanoparticles.