EFFECT OF HEPARIN ON INFECTION OF CELLS BY PORCINE REPRODUCTIVE AND RESPIRATORY SYNDROME VIRUS

Objective-To investigate whether heparin has any effect on the growth of porcine reproductive and respiratory syndrome virus (PRRSV). Sample Population-2 isolates of PRRSV, and as control viruses, 1 isolate of pseudorabies virus (PRV) and 1 isolate of parainfluenza 3 virus (PIV-3 ). Procedures-Plaque assays, using a continuous cell line (MARC-145) d erived from African green monkey kidney cell line (MA104), were perfor med for determination of inhibitory effect of heparin on PRRSV, PRV, a nd PIV-3. The effect of various doses of heparin and heparinase on the growth of PRRSV, PRV, and PIV3 was evaluated and compared. In each ex periment, values were expressed as the mean value for duplicate sample s. Results-The number of plaques formed by PRRSV and PRV was reduced t o 24 to 25 and 15% of the untreated control (100%), respectively, by 1 U of heparin/ml, but could not be reduced below 6 to 7 and 3%, respec tively, by use of concentrations up to 50 U/ml. An inhibitory effect o f heparin, at a concentration up to 50 U/ml, was not observed on PIV-3 . Delaying addition of heparin for 30 minutes after the addition of PR RSV and PRV reduced plaque formation by 48 to 51 and 68%, respectively , compared with 91 to 92 and 95%, respectively, if heparin was added a t the time of infection. In addition, most PRRSV added was retained by heparin beads, as was PRV. Heparinase treatment of MARC-145 cells red uced the number of PRRSV-, as well as PRV-induced plaques. On the othe r hand, the number of PIV-S-induced plaques did not decrease after tre atment of MARC-145 cells with heparinase. Conclusions-Addition of hepa rin to PRRSV or to the MARC-145 cells before virus inoculation and tre atment of the cells with heparinase prevented the virus from infecting the cells.