Infection of the erythroid cell line, KU812Ep6 with human parvovirus B19 and its application to titration of B19 infectivity

A human parvovirus B19 (B19) infectivity assay was developed using the eryt hroid cell line, KU812Ep6. KU812Ep6 was cloned for high efficiency infectio n with B19 in vitro, in the presence of erythropoietin by a limiting diluti on method from the parent cell line, KU812. B19 was effectively propagated in KU812Ep6 and was detected for B19 antigens, VP1 and VP2. The titers of B 19 positive sera measured with KU812Ep6 cells were in the range of 10(6) to 10(8) TCID50 ml. This KU812Ep6 infectivity assay had a 10(3)-10(4.5) highe r sensitivity than the colony forming unit-erythroid (CFU-e) injury assay. It was calculated that one TCID50 needed 10(3) B19 genome copies, judging f rom the infectivity assay and semi-quantitative PCR. The KU812Ep6 infectivi ty assay was also used to determine infectivity of B19 in vitro, and to eva luate inactivation, as well as clearance of the virus. The inactivation of B19 by heating was carried out and infectivity declined from 10(4) TCID50 m l to < 10 TCID50 ml (lower limit of detection) at 60 degrees C for 3 h or a t 70 degrees C for 30 min, but only decreased to 10(2.5) TCID50 ml at 50 de grees C for 8 h. (C) 1999 Elsevier Science B.V. All rights reserved.