In vitro comparison between four variants of Aujeszky's disease virus

Area of Science:

• Virology
• Animal Pathology
• Molecular Biology

Background:

• Aujeszky's disease (pseudorabies) virus (ADV) poses a significant threat to swine health.
• Understanding ADV variant characteristics is crucial for disease control and vaccine development.
• Previous studies indicated differing pathogenicity among ADV strains.

Purpose of the Study:

• To characterize four Aujeszky's disease virus variants in vitro.
• To investigate their resistance to heat, sensitivity to trypsin, and replication in pig alveolar macrophages.
• To correlate in vitro characteristics with known in vivo pathogenicity.

Main Methods:

• In vitro characterization of four ADV variants: Ls-1, Ls-2, Stanley (virulent), and NIA-4 (non-virulent).
• Assessment of heat resistance at 48°C and trypsin sensitivity.
• Evaluation of viral replication in pig alveolar macrophages, including progeny virus titration at high and low virus input (0.1 TCID50/cell).

Main Results:

• Heat treatment at 48°C showed slight decreases in infectivity with no significant differences in inactivation rates among variants.
• Variants Ls-1 and Ls-2 exhibited significantly higher sensitivity to trypsin compared to Stanley and NIA-4 strains.
• Replication studies in pig alveolar macrophages revealed differentiation: Ls-1 produced higher progeny titres than Ls-2 at low virus input (statistically significant, P < 0.05).
• Cytopathogenicity in macrophages correlated with virulence for pigs; Stanley was most cytopathogenic, NIA-4 least.

Conclusions:

• In vitro assays, particularly trypsin sensitivity and macrophage replication dynamics, can differentiate Aujeszky's disease virus variants.
• The observed in vitro characteristics, including cytopathogenicity, are correlated with the in vivo virulence of ADV strains.
• These findings provide valuable insights into the biological properties of ADV variants and their pathogenicity.