Cross-Protection in PRRSV: Mechanisms, Limitations, and Implications for Vaccine Design

Area of Science:

• Veterinary Virology
• Immunology
• Swine Health

Background:

• Porcine reproductive and respiratory syndrome (PRRS) is a major economic threat to global swine production.
• PRRS virus (PRRSV) has two species (PRRSV-1, PRRSV-2) with significant antigenic differences.
• Current modified live vaccines (MLVs) provide inconsistent protection against heterologous and cross-species PRRSV strains.

Purpose of the Study:

• To review current knowledge on PRRSV protection, focusing on immune responses and viral factors.
• To analyze the limitations of existing vaccines against diverse PRRSV strains.
• To identify targets for developing next-generation PRRSV vaccines.

Main Methods:

• Literature review synthesizing data on humoral and cellular immunity to PRRSV.
• Analysis of viral determinants, including envelope glycoproteins, that impact immune breadth.
• Examination of the role of preexisting immunity in vaccine efficacy.

Main Results:

• Neutralizing antibodies provide strong homologous protection but are narrow in specificity and slow to develop.
• T-cell responses are broader but strain- and context-dependent.
• Viral glycoprotein structures (glycan shielding, decoy epitopes) limit cross-protection; preexisting immunity can lead to suboptimal responses.

Conclusions:

• PRRSV protection is complex, influenced by multiple viral and host factors.
• Existing vaccines struggle with heterologous and cross-species protection due to antigenic variation and immune response limitations.
• Development of next-generation vaccines requires strategies to induce broader and more durable immunity against PRRSV.