The recent article by Piazza et al1 on sexual transmission of the hepatitis C virus (HCV) and efficacy of prophylaxis with intramuscular immune serum globulins (IGs) interested us greatly. The results obtained from this controlled trial showed that HCV can be sexually transmitted by chronically infected patients and provided strong evidence of a protective role of IG produced from unscreened plasma.
More information could be obtained by investigating the presence of HCV RNA by polymerase chain reaction in the IG lots used in this trial. In a recent study,2 we showed that 30 (45.5%) of 66 IG lots produced between 1990 and 1992 tested positive for HCV RNA, while 100% of the lots were strongly anti-HCV reactive by third-generation recombinant immunoblot assay. All 41 IG lots produced since 1993 from screened plasma tested negative for both HCV RNA and anti-HCV antibodies. Since IG produced from unscreened plasma was not subjected to any validated viral inactivation and/or removal step, the presence of viral RNA in such products could be a matter of concern. Nevertheless, IG has never been reported to be involved in transmission of HCV. This safety record is still unclear, and, under the present circumstances, debate is expected to continue because of the difficulty in monitoring IG recipients. One can postulate that the low dosage, the route of administration, and the occasional administration play a role in decreasing the risk of transmission of HCV by IG. Moreover, the presence of anti-HCV antibodies has been assumed to reduce the infectivity of the viral particles that may be present.3 Should any of the 4 lots used in the study by Piazza et al1 be found positive for HCV RNA, this would be the first direct evidence that IG positive for both HCV RNA and anti-HCV antibodies is not infectious.