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Chicken Anaemia Viral Infection of MSB1 Cells Is Sensitive to rChIFN-alpha

There are three major questions concerning the interaction between chicken anaemia virus (CAV) and chicken interferon (ChIFN). (1) Can CAV induce ChIFN? We do not think it can because it is a ssDNA virus that does not use dsRNA for replication. We have found that ChIFN can be induced in MSB1 cells, using inactivated Newcastle disease virus (iNDV) (unpublished observations). Thus, this question can be answered by infecting MSB1 cell cultures with CAV and monitoring abundance of mRNA for ChIFN(1) over time. (2) Can CAV interfere with production of ChIFN? Yes, we have shown that induction of ChIFN mRNA by iNDV was markedly reduced in SPF chickens with subclinical infection of CAV.(2) (3) Is CAV sensitive to ChIFN? This is the subject of the present report. The antiviral effect of ChIFN-alpha on CAV replication was investigated in MSB1 cell culture. Cells at 105 in 1 ml were infected with 106 TCID50 CAV, DelRoss strain, in 0.1 ml (24-well plates). Cells were treated 24 h later with 0, 1, 10, 100, 1000 or 10000 units of rChIFN-&#61537 ; (3) (a gift from Drs. P. I. Marcus and M. J. Sekellick, University of Connecticut). In another experiment, the cells also were treated with rChIFN-alpha one day before infection. Two days after infection, 10 microl aliquots were taken for viral titration.(4) Additional aliquots were taken to measure viral load by competitive nucleic acid hybridisation in microtitre plates.(5) The remaining cells were counted, 105 cells transferred in 1 ml to new plates, and rChIFN-alpha treatment repeated. This schedule was repeated twice. Viral load was significantly reduced by treatment with 1, 000 and 10, 000 units of rChIFN-alpha, as determined by viral titre (Fig. 1) and by abundance of CAV DNA (Fig. 2), even when cells were not pretreated. Viral titre and abundance of CAV DNA were correlated in both experimental protocols (Fig. 3). Although not highly sensitive, CAV was nevertheless susceptible to rChIFN-alpha treatment. Whether the infection can be eliminated by continued treatment remains to be determined.

CAV; NDV; ChIFN-alpha

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