Sequencing of multiple recombinant clones generated from polymerase chain reaction-amplified products demonstrated that the degree of heterogeneity of two well-conserved regions of the hepatitis C virus (HCV) genome within individual plasma samples from a single patient was consistent with a quasispecies structure of HCV genomic RNA. About half of circulating RNA molecules were identical, while the remaining consisted of a spectrum of mutants differing from each other in one to four nucleotides. Mutant sequence diversity ranged from silent mutations to appearance of in-frame stop codons and included both conservative and nonconservative amino acid substitutions. From the relative proportion of essentially defective sequences, we estimated that most circulating particles should contain defective genomes. These observations might have important implications in the physiopathology of HCV infection and underline the need for a population-based approach when one is analyzing HCV genomes.

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In our geographic area, almost 70% of donors who are anti-HCV positive by ELISA are confirmed to be positive by RIBA-2; most of these donors appear to be chronic carriers of HCV and have substantial liver disease.

To evaluate the profile of hepatitis D virus replication and the corresponding immunoresponse after acute hepatitis D virus infection, sera from 50 patients with acute hepatitis D (36 with acute hepatitis B virus-hepatitis D virus coinfection and 14 HBsAg carriers with hepatitis D virus superinfection) were investigated for the presence of hepatitis D virus RNA and other serological hepatitis D virus markers. During the first week after onset of symptoms, hepatitis D virus RNA was detected by spot hybridization with a similar frequency among patients with coinfection (64%) and those with superinfection (71%). The presence of hepatitis D virus RNA in the first serum sample correlated with that of circulating hepatitis D antigen in both groups of patients. The presence of hepatitis D virus RNA was transient and its clearance paralleled that of serum hepatitis D antigen among patients with coinfection, so that 1 month after the onset of symptoms serum hepatitis D virus RNA was no longer detectable in any of these patients. Conversely, serum hepatitis D virus RNA was still present in 78% of those with superinfection, all of whom developed chronic liver disease, thus suggesting that the persistence of hepatitis D virus RNA in the serum for more than 4 weeks might indicate progression to chronicity. In nine of the 14 patients (64%) with hepatitis D virus superinfection progressing to chronicity, hepatitis D virus RNA was persistently detected throughout the follow-up, whereas in five patients it was detected occasionally. In four superinfected patients hepatitis D virus RNA and hepatitis B virus DNA were detected simultaneously in serial samples, thus suggesting that, at least during early stages of chronic hepatitis D virus infection, both viruses may replicate at the same time.