Calibration of chimpanzee plasmas of known infectivity

An important driver of residual transmission risk by blood transfusion is the viral infectivity in blood. We compared Japanese chimpanzee plasma’s with a known infectivity titer to the VQC-Sanquin standards and according to this calibration experiment the 50% chimpanzee minimum infectious dose (CID50) (and range) was determined at 4.0 (1.3-12.6) and 8.1 (2.6-25.6) copies or virions for HBV and HCV respectively. According to recalibration of a very low HCV concentration in a pool of pre-ramp up samples we estimated that 14 (instead of 60) HCV virions were infectious in a chimpanzee, indicating that the CID50 (range) could be as low as 4.4 (1.4-14) virions. For worst case window period risk modelling we therefore assumed a 50% minimum infectious dose (MID50) of 3.16 (range between 1 and 10) virions or copies for both HBV or HCV. A similar worst case MID50 of 3.16 (1-10) virions was estimated from SIV infectivity studies in macaques, but the infectivity of HIV is estimated to be 10-100 fold lower in stored cellular blood components.

The calibration data of the chimpanzee infectivity plasma’s against the VQC-Sanquin standards are described in this validation report (PDF).