The Thai Journal of Veterinary Medicine


Porcine pulmonary intravascular macrophages (PIMs) have been recently known for their role of pulmonary surveillance. In the past few years, we have been investigating the role of PIMs in porcine reproductive and respiratory syndrome virus (PRRSV) infection. PRRSV antigen has been demonstrated in PIMs both in vitro and in vivo. PRRSV-infected PIMs reveal viral particles that tend to accumulate in the smoothed-wall vesicles and yield a high virus titer. The PRRSV infection induces either apoptosis or cell lysis. The bactericidal activity of in vitro PRRSV infected PIMs is significantly decreased and the phagocytic activity is questionable as the pulmonary copper clearance, which measures the phagocytic activity of PIMs in vivo, is significantly decreased in PRRSV-infected pigs. This evidence supports the hypothesis that PRRSV - induced damage to PIMs results in increased susceptibility to bacteremic diseases. This result could explain the increase in the chronic bacterial respiratory diseases, septicemia, and mortality experienced in pigs on farms endemically-or epizootically-infected with highly virulent strains of PRRSV. The objective of this article is to summarize the current knowledge of the complex interaction between PRRSV and the PIMs.



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