Development of a low-cost, insect larvae-derived recombinant subunit vaccine against RHDV

Area of Science:

• Veterinary Virology
• Vaccine Development
• Recombinant Protein Expression

Background:

• Current rabbit hemorrhagic disease virus (RHDV) vaccines rely on inactivated virus from infected rabbit livers.
• Existing recombinant RHDV immunogens face high production costs, limiting their vaccine application.
• There is a need for inexpensive, safe, and stable RHDV vaccine antigens.

Purpose of the Study:

• To develop an affordable, safe, and stable vaccine antigen for RHDV.
• To evaluate the efficacy of a recombinant RHDV capsid protein (VP60r) produced in insect larvae.

Main Methods:

• A baculovirus vector expressed RHDV capsid protein (VP60r) in Trichoplusia ni insect larvae.
• Expression efficiency, antigenicity, and immunogenicity of VP60r were assessed.
• Stability of lyophilized crude larvae extracts containing VP60r was tested at room temperature.
• Rabbits were immunized intramuscularly with VP60r and challenged with RHDV.

Main Results:

• High expression efficiency of VP60r (12.5% of soluble protein, ~2 mg/larva) was achieved.
• VP60r retained its antigenicity and immunogenicity.
• Lyophilized VP60r extracts remained stable for over 800 days at room temperature.
• A single intramuscular dose of VP60r (2 µg with adjuvant, 100 µg without) protected rabbits against RHDV challenge.
• Oral administration of VP60r without adjuvant did not provide protection.

Conclusions:

• The insect larva expression system offers a cost-effective strategy for producing RHDV VP60r antigen.
• This recombinant antigen is stable, immunogenic, and provides protection against RHDV.
• Larva-based production of recombinant antigens (insectigens) can reduce vaccine costs for human and animal health.