No abstract

Recent evidence indicates there is a role for small membrane vesicles, including exosomes, as vehicles for intercellular communication. Exosomes secreted by most cell types can mediate transfer of proteins, mRNAs, and microRNAs, but their role in the transmission of infectious agents is less established. Recent studies have shown that hepatocyte-derived exosomes containing hepatitis C virus (HCV) RNA can activate innate immune cells, but the role of exosomes in the transmission of HCV between hepatocytes remains unknown. In this study, we investigated whether exosomes transfer HCV in the presence of neutralizing antibodies. Purified exosomes isolated from HCV-infected human hepatoma Huh7.5.1 cells were shown to contain full-length viral RNA, viral protein, and particles, as determined by RT-PCR, mass spectrometry, and transmission electron microscopy. Exosomes from HCV-infected cells were capable of transmitting infection to naive human hepatoma Huh7.5.1 cells and establishing a productive infection. Even with subgenomic replicons, lacking structural viral proteins, exosome-mediated transmission of HCV RNA was observed. Treatment with patient-derived IgGs showed a variable degree of neutralization of exosome-mediated infection compared with free virus. In conclusion, this study showed that hepatic exosomes can transmit productive HCV infection in vitro and are partially resistant to antibody neutralization. This discovery sheds light on neutralizing antibodies resistant to HCV transmission by exosomes as a potential immune evasion mechanism.

No abstract

Hepatitis E virus (HEV) represents the main cause of acute hepatitis worldwide. HEV infection in immunocompromised patients involves a high risk for the development of chronic hepatitis. Because HEV is recognized as a zoonotic pathogen, it is currently believed that swine is the primary reservoir. However, this is not sufficient to justify the strikingly high seroprevalence of HEV in both developing and Western countries. Thus, this study aimed to identify new zoonotic sources that bear a high risk of transmission to humans. We collected fecal, blood, and milk samples of cows in a typical rural region of Yunnan Province in southwest China, where mixed farming of domestic animals is a common practice. HEV RNA was quantified by quantitative real-time polymerase chain reaction, and the whole genome was sequenced. HEV infectivity was assessed in rhesus macaques. We found a high prevalence of active HEV infection in cows as determined by viral RNA positivity in fecal samples. Surprisingly, we discovered that HEV is excreted into milk that is produced by infected cows. Phylogenetic analysis revealed that all HEV isolates from cow/ milk belong to genotype 4 and subtype 4h. Gavage with HEV-contaminated raw and even pasteurized milk resulted in active infection in rhesus macaques. Importantly, a short period of boiling, but not pasteurization, could completely inactivate HEV. Conclusion: Infectious HEV-contaminated cow milk is recognized as a new zoonotic source that bears a high risk of transmission to humans; these results call attention to understanding and establishing proper measurement and control of HEV zoonotic transmission, particularly in the setting of mixed farming of domestic animals. (HEPATOLOGY 2016;64:350-359) H epatitis E virus (HEV) is a positive singlestranded RNA virus with four defined genotypes and other newly discovered strains that have not been assigned to these known genotypes. (1) It is the most common cause of acute hepatitis globally. (2) In the Western world, chronic hepatitis has been frequently described in immunocompromised patients. (3) Thus, HEV infection has emerged as a global public health issue with a particularly high mortality rate in pregnant women. (4) Seroprevalence is rather high in the developing world, ranging 30%-80%. Strikingly, it is also very high in Western countries. In the United States, population-based surveys have indicated a seroprevalence of 21% from 1988 to 1994 and 6% from 2009 to 2010. (5) An overall seroprevalence of 22.4% and 27% was found in French (6) and Dutch (7) blood donors, respectively.In the developing world, epidemics of hepatitis E occur periodically and are mainly attributed to genotypes 1 and 2. They account for annually 20 million infections, over 3 million cases with symptomatic diseases, and 70,000 deaths. (8) Fecal contamination of drinking water is a major route of transmission of these two genotypes. (8) In contrast, in developed countries, HEV genotype 3 is predominant and spread by zoonotic transmission.