Assessment of viral inactivation during pH 3.3 pepsin digestion and caprylic acid treatment of antivenoms

Abstract

Antivenoms are manufactured by the fractionation of animal plasma which may possibly be contaminated by infectious agents pathogenic to humans. This study was carried out to determine whether pre-existing antivenom production steps, as carried out by EgyVac in Egypt, may reduce viral risks. Two typical manufacturing steps were studied by performing down-scaled viral inactivation experiments: (a) a pH 3.3 pepsin digestion of diluted plasma at 30 °C for 1 h, and (b) a caprylic acid treatment of a purified F(ab′)2 fragment fraction at 18 °C for 1 h. Three lipid-enveloped (LE) viruses [bovine viral diarrhoea virus (BVDV), pseudorabies virus (PRV), and vesicular stomatitis virus (VSV)] and one non-lipid-enveloped (NLE) virus [encephalomyocarditis virus (EMC)] were used as models. Kinetics of inactivation was determined by taking samples at 3 time-points during the treatments. The pH 3.3 pepsin digestion resulted in complete clearance of PRV (>7.0 log 10) and in almost complete reduction of VSV (>4.5 but ≤6.4 log 10), and in a limited inactivation of BVDV (1.7 log 10). EMC inactivation was ≥2.5 but ≤5.7 log 10. The caprylic acid treatment resulted in complete inactivation of the 3 LE viruses tested: BVDV (>6.6 log 10), PRV (>6.6 log 10), and VSV (>7.0 log 10). For EMC no significant reduction was obtained (0.7 log 10). Cumulative reduction was >13.6, >11.5, >8.3 and ≥2.5 for PRV, VSV, BVDV and EMC, respectively. Therefore the current manufacturing processes of at least some animal antisera already include production steps that can ensure robust viral inactivation of LE viruses and moderate inactivation of a NLE virus.