Virulent Lena strain induced an earlier and stronger downregulation of CD163 in bronchoalveolar lavage cells

• Published in: Veterinary microbiology Vol. 235; pp. 101 - 109
• Main Authors: Rodríguez-Gómez, Irene M., Sánchez-Carvajal, José M., Pallarés, Francisco J., Mateu, Enric, Carrasco, Librado, Gómez-Laguna, Jaime
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.08.2019; Elsevier BV
• Subjects: Alveoli; BALF; Bronchus; CD163; CD163 antigen; Fluorescence; Homeostasis; Immunohistochemistry; Inoculation; Lena; Lungs; Macrophages; PAMs; PRRSV-1; Strains (organisms); Suidae; Swine; Virulence; Viruses; Lena; CD163; PAMs; PRRSV-1; BALF
• ISSN: 0378-1135; 1873-2542
• DOI: 10.1016/j.vetmic.2019.06.011

•Virulent strain Lena induced a severe bronchopneumonia in the lungs when compared to a less virulent strain.•Lena strain caused a high rate of dead PAMs in the BALF in comparison with a strain of low virulence.•In comparison with the low virulent strain, Lena induced an earlier and stronger downregulation of CD163.•Lena strain replicated more efficiently in CD163+ cells than a strain of low virulence. Highly virulent porcine reproductive and respiratory syndrome virus (PRRSV) strains have increasingly overwhelmed Asia and Europe in recent years. This study aims to compare the clinical signs, gross and microscopic findings as well as the expression of CD163 within live pulmonary alveolar macrophages (PAMs) from bronchoalveolar lavage fluid (BALF) of pigs experimentally infected with two PRRSV strains of different virulence. Pigs were infected with either a subtype 1 PRRSV-1 3249 strain or a subtype 3 PRRSV-1 Lena strain and consecutively euthanized at 1, 3, 6, 8 and 13 days post-inoculation. Clinical signs were reported daily and BALF and lung tissue samples were collected at the different time-points and accordingly processed for their analysis. Pigs infected with Lena strain exhibited greater clinical signs as well as gross and microscopic lung scores compared to 3249-infected pigs. A decreased frequency of PAMs from BALF was observed early in pigs infected with Lena strain. Moreover, the frequency and median fluorescence intensity (MFI) of CD163 within PAMs were much lower in Lena-infected pigs than in 3249-infected pigs. This downregulation in CD163 was also observed in lung sections after the assessment of macrophages expressing CD163 by means of immunohistochemistry. This outcome may result from the effect of PRRSV replication, PRRSV-induced inflammation, the influx of immature macrophages to restore lung homeostasis and/or the evidence of CD163low cells after CD163+ cells decrease in BALF.