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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Animal Parasitic Diseases Laboratory » Research » Publications at this Location » Publication #306732
Title: Changes in leukocyte subsets of pregnant gilts experimentally infected with porcine reproductive and respiratory syndrome virus and relationships with viral load and fetal outcome

Author
item LADINIG, ANDREA - University Of Saskatchewan
item GERNER, WILHELM - University Of Vienna
item SAALMULLER, ARMIN - University Of Vienna
item Lunney, Joan
item ASHLEY, CAROLYN - University Of Saskatchewan
item PLASTOW, GRAHAM - University Of Alberta
item HARDING, JOHN - University Of Saskatchewan

Submitted to: Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2014
Publication Date: 12/2/2014
Citation: Ladinig, A., Gerner, W., Saalmuller, A., Lunney, J.K., Ashley, C., Plastow, G., Harding, J.C. 2014. Changes in leukocyte subsets of pregnant gilts experimentally infected with porcine reproductive and respiratory syndrome virus and relationships with viral load and fetal outcome. Veterinary Research. 45:128.

Interpretive Summary: Despite extensive research since 1989, our understanding of porcine reproductive and respiratory syndrome virus (PRRSv) immunity is still incomplete, particularly as it affects the sow and her litter. A PRRSv infection of the late term pregnant female can result in abortions, early farrowings, fetal death, and the birth of weak, congenitally infected piglets. The objectives of the present study were to investigate the effects of changes in peripheral blood mononuclear cell (PBMC) populations in third trimester pregnant females infected with North American (type 2) PRRSv. To do this a late term pregnant female gilt model was developed in which the gilt was infected at 86 days gestations and blood collected day 0 (D0), D2, D6, and D19 post infection. We analyzed potential relationships of changes in blood cell populations with viral load and fetal mortality rate. The first effect of PRRSv infection was an acute drop in total leukocyte counts affecting all PBMC populations by D2. Except for B cells, cell counts started to rebound by D6. The acuteness of the drop and subsequent rebound suggests cells in all PBMC subsets traffic from the blood to local sites of infection. When cell subsets were analyzed there was a greater, initial loss of naïve B cells, T-helper cells and cytolytic T cells from the blood; this was different for effector, or memory, T and B cells. Results indicated that absolute numbers of T helper cells may be predictive of fetal mortality rate. Several leukocyte populations (T helper and gamma-delta T cells) may be predictive of PRRSv-related pathological outcomes in pregnant gilts. Taken together, these findings provide insight into cellular anti-viral responses that may help researchers to determine new ways to reduce the impact of PRRSv in pregnant gilts.

Technical Abstract: In spite of more than two decades of extensive research, the understanding of porcine reproductive and respiratory syndrome virus (PRRSv) immunity is still incomplete. A PRRSv infection of the late term pregnant female can result in abortions, early farrowings, fetal death, and the birth of weak, congenitally infected piglets. The objectives of the present study were to investigate changes in peripheral blood mononuclear cell populations in third trimester pregnant females infected with type 2 PRRSv (NVSL 97-7895) and to analyze potential relationships with viral load and fetal mortality rate. PRRSv infection caused a massive, acute drop in total leukocyte counts affecting all PBMC populations by two days post infection. Except for B cells, cell counts started to rebound by day six post infection. The acuteness of the drop and subsequent rebound suggests cells in all PBMC subsets traffic to sites of infection. Our data also show a greater, initial loss of naïve B cells, T-helper cells and cytolytic T cells from the systemic circulation than their respective effector or memory counterparts. Absolute numbers of T cells and gamma-delta T cells were negatively associated with PRRSv RNA concentration in gilt serum over time. Additionally, absolute numbers of T helper cells may be predictive of fetal mortality rate. The preceding three leukocyte populations may therefore be predictive of PRRSv-related pathological outcomes in pregnant gilts. Although many questions regarding the immune responses remain unanswered, these findings provide insight and clues that may help reduce the impact of PRRSv in pregnant gilts.