How Cutting-Edge Vaccines Are Armoring Rabbits Against Invisible Killers
Veterinary Immunology Research
Beneath their fluffy exterior, rabbits face an invisible battlefield. Emerging viral mutations like the highly virulent (HV) strain of Rabbit Viral Haemorrhagic Disease Virus 2 (RVHD2) are outpacing conventional vaccines, causing organ failure and death within 48 hours. With HV-RVHD2 confirmed in Europe and likely already in the UK undetected 1 6 , the race for next-generation vaccines has become critical. This article explores how recombinant antigens, virus-like particles (VLPs), and cytokine adjuvants are forging a new arsenal in this high-stakes fight.
Highly virulent strain causes death within 48 hours with 90% mortality in unvaccinated rabbits.
Next-gen approaches using VLPs and adjuvants show promise against mutating strains.
RVHD2 (GI.2), a calicivirus, attacks liver and blood vessels, causing fatal hemorrhages. Its mutation into an HV strain—with 5-10× higher mortality in vaccinated rabbits—exploits three weaknesses in old defenses 1 6 :
Classical vaccines target VP60 capsid proteins of older RVHD1 (GI.1), leaving gaps against GI.2 mutations.
Antibodies from existing vaccines fail to neutralize HV strains due to surface protein changes.
No commercial tests distinguish classical vs. HV strains in the UK, delaying outbreak responses 1 .
| Strain | Mortality Rate | Current Vaccine Efficacy |
|---|---|---|
| Classical RVHD1 | 50-70% | High (if boosted annually) |
| RVHD2 (GI.2) | 70-90% | Moderate (waning after 6 months) |
| HV-RVHD2 | >95% | Low (minimal cross-protection) |
Scientists genetically fuse surface loops from GI.1 and GI.2 VP60 proteins into a single "hybrid" capsid. Expressed in baculovirus systems, these self-assemble into non-infectious VLPs mimicking the virus.
Results: 100% survival against both strains 8 .
Subunit vaccines use isolated antigens (gB/gD) for precision strikes combined with GM-CSF to recruit dendritic cells.
Results: Antibody levels 3× higher, 100% survival vs PRV 4 .
Oral vaccines using attenuated Salmonella deliver VP60 DNA directly to immune cells with IL-2 adjuvant.
Results: 8× IgG response, 90% survival 7 .
| Group | Survival Rate | Antibody Titers |
|---|---|---|
| gB+gD+GM-CSF | 100% | 1:512 |
| gB+gD+ISA 201 | 80% | 1:128 |
| Inactivated PRV | 60% | 1:64 |
GM-CSF created a "trained alert" state, enabling rapid immune responses upon viral invasion. Histopathology revealed minimal brain lesions in survivors, proving systemic protection 4 .
| Reagent | Function | Example in Use |
|---|---|---|
| Baculovirus Expression System | Produces complex glycoproteins in insect cells | Used to generate authentic gB/gD for subunit vaccines 4 |
| pVAX1 Vector | Delivers DNA vaccines; safe for eukaryotic expression | VP60+IL-2 plasmid construction 7 |
| Adjuvants (GM-CSF, IL-2) | Boosts antigen presentation and T-cell activation | GM-CSF elevated survival to 100% in PRV challenge 4 |
| Attenuated S. typhimurium SL7207 | Oral DNA vaccine delivery to gut immune cells | Carried VP60+IL-2 for intestinal immunity 7 |
| Ni-NTA Chromatography | Purifies His-tagged recombinant proteins | Isolated GM-CSF from E. coli lysates 4 |
Critical measures:
The era of "one vaccine, one disease" is ending. By hijacking viral geometry (VLPs), weaponizing cytokines (GM-CSF/IL-2), and rewriting delivery (oral DNA vaccines), scientists are crafting adaptive shields. For rabbits—pets and ecological linchpins alike—this isn't just innovation. It's evolution with a helping hand.
Action Step: Rabbit owners should request the RVHD2-HV vaccine (e.g., Yurvac) 2+ weeks after their annual Myxo-RHD booster 5 .