Animal Health Research Reviews

Table of Contents - 2000 - Volume 1, Issue 02  

Research Article

The role of pulmonary intravascular macrophages in porcine reproductive and respiratory syndrome virus infection

Roongroje Thanawongnuwecha1a2, Patrick G. Halbura3 and Eileen L. Thackera2 c1

a1 Department of Veterinary Pathology, Chulalongkorn University, Faculty of Veterinary Science, Bangkok 10330, Thailand

a2 Veterinary Medical Research Institute, Iowa State University, Ames Iowa 50010 USA

a3 Department of Veterinary Diagnostic and Production Animal Medicine, Iowa State University, Ames Iowa 50011, USA

Abstract

The objective of this article is to summarize the current state of knowledge of the complex interaction of porcine reproductive and respiratory syndrome virus (PRRSV) and porcine pulmonary intravascular macrophages (PIMs). PIMs play an important role in pulmonary surveillance, and in the past few years we have investigated their role in PRRSV infection. PRRSV antigens and nucleic acids have been demonstrated in PIMs both in vitro and in vivo. Examination of cultured PIMs infected with PRRSV revealed the accumulation of viral particles in the smooth-walled vesicles. PRRSV-infected PIMs in vitro yielded a virus titer similar to pulmonary alveolar macrophages. PRRSV infection induces either apoptosis or cell lysis of PIMs. The in vitro bactericidal activity of PRRSV-infected PIMs is significantly decreased. Phagocytic activity of PIMs, as measured by pulmonary copper clearance, 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. Recent studies with PRRSV and Streptococcus suis coinfection confirmed that PRRSV predisposes pigs to S. suis infection and bacteremia. These results could explain the increase in bacterial respiratory diseases and septicemias observed in PRRSV-infected pigs.

(Received May 08 2000)

(Accepted October 10 2000)

Correspondence:

c1 *Veterinary Medical Research Institute, Iowa State University, 1802 Elwood Drive, Ames, IA 50010, USA E-mail: ethacker@iastate.edu

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