Bombyx mori nucleopolyhedrovirus : Biotechnological applications and a model to study host-virus interactions

Abstract

Bombyx mori Nucleopolyhedrovirus: Biotechnological Applications and a Model to Study Host-Virus Interactions

Abstract and Synopsis Introduction Autographa californica multinucleocapsid nucleopolyhedrovirus (AcMNPV) can infect nearly 40 species of lepidopteran larvae and their cell lines, but not Bombyx mori. In contrast, Bombyx mori nucleopolyhedrovirus (BmNPV) is restricted to B. mori and its derived cell lines. Understanding the molecular basis of this host specificity is crucial for both biotechnology and sericulture.

Baculoviruses are widely used as biopesticides and as expression vectors for recombinant proteins. The present study aimed to improve the BmNPV-based expression system for diverse applications, including surface display of heterologous proteins, vaccine development, and analysis of host-virus interactions.

Objectives

Characterize the gp64 gene encoding the envelope fusion glycoprotein GP64 from BmNPV.

Develop BmNPV as a eukaryotic surface display system using GP64.

Display heterologous viral antigens on BmNPV particles and evaluate their immunogenicity.

Analyze systemic and in vitro infection processes of BmNPV using recombinant GFP-tagged viruses.

Evaluate host specificity of AcMNPV and BmNPV in permissive and nonpermissive cell lines.

Key Results

Characterization of GP64 from BmNPV

GP64 is essential for viral entry, exit, and spread.

Transcription analysis revealed early and late promoters (CAGT and TAAG motifs).

Protein expression persisted throughout infection, differing from AcMNPV GP64.

GP64 localized to membranes, cytoplasm, and budded virions; glycosylation was critical for infectivity.

BmNPV-Based Surface Display System

GFP was successfully displayed on host cell surfaces and budded virions.

Recombinant BmNPV retained infectivity comparable to parental virus.

This was the first demonstration of protein display in B. mori larvae.

Display of Veterinary Viral Antigens

Fusion proteins of PPRV-F and RPV-H were displayed on BmNPV particles.

Antigenic epitopes were properly presented.

Recombinant particles induced immune responses in mice, highlighting vaccine potential.

Systemic and In Vitro Infection Analysis

GFP-tagged recombinant virus showed initial replication in midgut epithelial cells.

Spread occurred via tracheae to multiple tissues, including neurons and silk glands.

In vitro infections confirmed tracheae as key conduits for viral dissemination.

Host Specificity Studies

AcMNPV infects Spodoptera frugiperda but not B. mori.

BmNPV infects B. mori but not S. frugiperda.

Despite 90% genomic identity, host ranges remain distinct, underscoring molecular restrictions in nonpermissive hosts.

Conclusions BmNPV can be engineered as a surface display system for recombinant proteins.

Displayed antigens retain immunogenicity, supporting vaccine development.

GFP-tagged BmNPV provides a powerful tool for studying infection dynamics and screening antiviral agents.

Host specificity between AcMNPV and BmNPV is determined at molecular levels yet to be fully elucidated.

This work advances both biotechnological applications and pathogenesis studies of baculoviruses.