Hepatitis C homolog in dogs with respiratory illness

摘要

In PNAS, Kapoor et al. (1) discover a Flaviviridae agent most closely related to hepatitis C virus (HCV); the identified RNA genome was isolated from domestic dogs with respiratory illness. This might shed new light on the origin and evolution of HCV and could lead to surrogate model systems for this important human pathogen. Over 100 million people are affected by hepatitis C worldwide, but research has been hampered by a lack of widely available animal models and representative culture systems. Thus, discovery of an HCV homolog in dogs gives hope for finding new ways to study this deadly human virus. The host range of HCV is restricted, and natural infection was detected only in humans; higher primates are susceptible to experimental infection (Fig. 1). However, an HCV homolog has not been detected in higher primates to date. The only other known homolog is GB virus B (GBV-B), which causes hepatitis in experimentally infected New World monkeys, but its true origin remains unknown (2) (Fig. 1). Thus, the finding of a homolog in dogs raises the interesting proposition that HCV might have evolved as a result of the close contact between dogs and humans during the past several thousand years. Kapoor et al. (1) estimate a divergence time of the dog and human viruses from a common ancestor within the past 500-1,000 y, but it is widely recognized that such calculations should be interpreted with great caution. As pointed out by Kapoor et al.