Search For New and Emerging Etiologic Agents

正在研究急性或慢性非甲、乙、丙、丁、戊型肝炎是否存在传播因子的生物学、血清学或分子证据。暴发性非甲至戊型肝炎仍然是一个诊断谜，可能代表一种或多种以前未被认识的疾病。我们正试图找出这种疾病的病因。我们在印度、埃及和沙特阿拉伯进行的血清流行病学研究提供了另一种水传播肝炎病毒存在的证据。我们正试图从这些病人身上传播一种病原体。戊型肝炎病毒可能正在成为一个比以前认为的更大的公共卫生问题。我们正在研究它在全世界发展中国家和工业化国家的流行病学。

Acute or chronic non-A, B, C, D, E hepatitis is being studied for biological, serological or molecular evidence of transmissible agents. Fulminant non-A to E hepatitis remains a diagnostic enigma and may represent one or more previously unrecognized diseases. We are attempting to discover the etiology of this disease. Evidence for the existence of an additional water-borne hepatitis virus has come from our seroepidemiologic studies in India, Egypt and Saudi Arabia. We are attempting to transmit an agent from such patients. Hepatitis E virus may be emerging as a greater public health problem than previously thought. We are studying its epidemiology in developing and industrialized countries worldwide. Serologic evidence of infection of swine with hepatitis E virus (HEV) was obtained. A new and unique HEV strain was recovered from infected swine and characterized. It was shown to have a worldwide distribution. Seroepidemiological studies of swine handlers and matched blood donors have shown an excess of antibody to HEV in swine handlers, suggesting that the virus may be zoonotically spread. In addition, throughout FY 2009, we have been evaluating the significance of antibody to HEV (anti-HEV) in domestic animals that are part of the human food chain, especially cattle, sheep and goats. Anti-HEV has been found in all of the species, although not to the extent that it is found in swine. Rarely, swine are an important zoonotic source of hepatitis E, especially in industrialized countries, but these don't account for the high prevalence of anti-HEV in Islamic and Jewish cultures. In collaboration with XJ Meng, we are determining the susceptibility of goats to infection with the recognized HEV strains and attempting to recover HEV-like agents from young goats that are being intensively monitored for serologic and molecular evidence of infection. Similar serologic evidence for infection of wild rats with HEV has also been obtained and the infecting agent is being sought. To date we have successfully transmitted the agent from rats trapped in Los Angeles to laboratory rats of the same species (Rattus norvegicus). However, transmission was difficult, suggesting that the virus replicates at low titer. Modern techniques of molecular biology have been used to discover new viruses in recent years. These are now being applied to sera from patients with transfusion-associated or community-acquired hepatitis in a search for new hepatitis viruses that may cause up to 2% of such hepatitis in the US and up to one-third of hepatitis in developing countries. In addition, a significant number of cases of chronic hepatitis, cirrhosis and liver cancer remain undiagnosed. In an attempt to increase the sensitivity of virus discovery, we are applying microarray technology to attempts to transmit new agents to chimpanzees, the only species other than man that is susceptible to all five recognized human hepatitis viruses. Preliminary results are promising. Similarly, approximately one half of nonbacterial gastroenteritis cases have no recognized etiology. In collaboration with the Epidemiology Section, LID, we are applying the same approaches to attempts to identify new gastroenteritis agents. Kawasaki Disease is a life-threatening illness of young children. It has the epidemiologic characteristics of an infectious disease. The HVS and MHS have attempted to transmit a putative agent from acute phase clinical samples of children with Kawasaki Disease to chimpanzees. Preliminary results were promising but confirmatory studies have been negative, possibly because available chimpanzees may have been exposed to the putative agent of Kawasaki disease previously. In FY 2009, while evaluating the innate and adaptive immune responses of chimpanzees that had been experimentally infected with hepatitis E virus (HEV), we discovered an aberrant innate immune response in two chimpanzees that had been infected with HEV from an outbreak of hepatitis E in Pakistan. Based on extensive experience with innate and adaptive immune responses to all five recognized human hepatitis viruses in chimpanzees, we postulated that the response in these animals was to a second agent replicating in the liver. By attempting transmission from the second innate immune response episode to new chimpanzees, we demonstrated evidence for an infection not related to hepatitis E in the original infection. We are in the process of examining an additional passage of this putative agent in chimpanzees. It has been associated with only minor biochemical evidence of hepatitis, but that is also true for HEV infection of chimpanzees. We plan to determine if this putative agent produces more severe infection on serial passage and whether it can be associated with hepatitis or other liver disease, such as liver cancer. Liver cancer is a common sequela of infection with three of the five recognized human hepatitis viruses.