PRRSV: strains of low and high virulence compared

A research group from the University of Córdoba, led by Professor Librado Carrasco, has been researching Porcine reproductive and respiratory syndrome virus (PRRSV) for years, with the aim of developing effective vaccines.

Although PRRSV was discovered in the 1990s, in recent years more virulent strains have emerged. As each strain behaves differently, developing effective vaccines has proved difficult. The researchers have been looking for similarities between strains.

“In our last study we compared two strains, one of low virulence, on which we had been working since the discovery of the disease; and another of great virulence that is much less known,” explains Irene M. Rodríguez Gómez, one of the group’s researchers.

For the study, published in Veterinary Microbiology, three groups of pigs were used. The first was infected with the low-virulence strain (subtype 1 PRRSV-1 3249 strain), and the second with the high-virulence strain (subtype 3 PRRSV-1 Lena strain). The third was the control group.

The study lasted 13 days; body temperature and blood samples were taken daily, and clinical symptoms observed. On the day of euthanasia, a bronchoalveolar lavage was performed and lung samples were taken.

“The results indicated that the high-virulence strain caused earlier and greater damage than did the low-virulence strain,” says Irene Rodríguez.

In addition to the analysis of the symptoms and the lesions observed in the infected pigs, the study also compared the macrophages of the three groups.

“A reduction in this type of cells was observed in the lungs,” says Irene Rodríguez. “These cells are of great importance when it comes to defending the organ, so their reduction causes the lung to be exposed to secondary infections, mainly bacterial, giving rise to other processes, such as bronchopneumonia.” The study also determined that the high-virulence strain attacked not only the lungs, but also the organs of the lymphatic system, such as the thymus, or bone marrow, which was not seen with the low-virulence strain.

This study is part of a larger project, funded by the Ministry of Economy and Competitiveness, which aims to sequence the transcriptome of the alveolar macrophage in the context of this disease.

Researchers from the University of Murcia and Autonomous University of Barcelona also contributed to the study.

Article: Rodríguez-Gómez, I. M., Sánchez-Carvajal, J. M., Pallarés, F. J., Mateu, E., Carrasco, L., Gómez-Laguna, J. (2019). Virulent Lena strain induced an earlier and stronger downregulation of CD163 in bronchoalveolar lavage cells. Veterinary Microbiology, 235, 101-109, doi: 10.1016/j.vetmic.2019.06.011

[SOURCE: University of Córdoba]