Search For New Hepatitis Agents

美国正在研究急性或慢性非甲、乙、丙、丁、戊型肝炎患者的临床样本，以寻找传播媒介的生物学、血清学或分子证据。暴发性非甲到戊型肝炎患者的诊断仍然是一个谜，可能感染了一种或多种以前未被识别的病毒。我们正试图找出这种疾病的病因。在印度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的临床标本中传播一种病原体。几年前，据报道一种肝炎病毒可从一名非甲、非乙肝炎患者传染给狨猴。该病菌可在狨猴中连续传播，已被部分鉴定。最近对GB病毒进行了克隆和测序，结果显示是两种不同的病毒（GBV-A和GBV-B），每一种病毒都与丙型肝炎病毒以及以前未被识别的人类病毒（GBV-C）有远亲关系。GB试剂和新发现的人类病毒正在灵长类动物和体外进行研究。构建了GBV-B的感染性cDNA。迄今为止，新发现的人类病毒（GBV-C）已传播给黑猩猩，由此产生的感染具有特征。此外，在新大陆猴子身上发现了几种与GBV-A有关的新病毒。这些正在被进一步表征。获得猪感染戊型肝炎病毒（HEV）的血清学证据。从感染猪中分离到一株新的独特HEV毒株，并对其进行了鉴定。对猪操作人员和匹配的献血者进行的血清流行病学研究显示，猪操作人员体内HEV抗体过量，表明该病毒可能通过人畜共患传播。也获得了野生大鼠感染戊型肝炎病毒的类似血清学证据，目前正在寻找感染源。迄今为止，我们已成功地将洛杉矶捕获的大鼠的一种hev样病原体传播给同一物种的实验室大鼠（褐家鼠）。然而，传播一直很困难，这表明病毒以低滴度复制。我们目前正试图获得病毒的部分序列，并将其传播给其他可能更容易接受的大鼠品系。确定大鼠HEV是否与人类感染有关的研究正在进行中。近年来，分子生物学的现代技术被用于发现新的病毒。目前，这些技术正被应用于从输血相关性肝炎患者中前瞻性收集血清，以寻找可能导致美国高达15%此类肝炎的新型肝炎病毒。为了提高特定病毒发现技术的灵敏度（即，那些能够在不考虑序列的情况下扩增独特序列的技术），我们对现有技术进行了修改，以提高检测的灵敏度。利用这项新技术，我们发现了两种以前未被识别的牛细小病毒，它们污染了大部分牛血清。这一发现对用牛血清制备的生物制剂的安全性具有启示意义。

Clinical samples from patients with acute or chronic non-A, B, C, D, E hepatitis in the United States are being studied for biological, serological or molecular evidence of transmissible agents. Patients with fulminant non-A to E hepatitis remain a diagnostic enigma and may be infected with one or more previously unrecognized viruses. We are attempting to discover the etiology of this disease. Evidence for the existence of an additional water-borne hepatitis virus has come from seroepidemiologic studies in India and Saudi Arabia. We are attempting to transmit an agent from clinical specimens of such patients. Some years ago, a hepatitis virus was reported to be transmissible from a non-A, non-B hepatitis patient to marmoset (tamarin) monkeys. The agent, called the GB agent, could be serially transmitted in marmosets and was partially characterized. Recently the GB agent was cloned and sequenced and shown to be two separate viruses (GBV-A and GBV-B), each distantly related to hepatitis C virus as well as to a previously unrecognized human virus (GBV-C). The GB agents and the newly discovered human virus are being studied in primates and in vitro. An infectious cDNA of GBV-B has been constructed. To date, the newly recognized human virus (GBV-C), has been transmitted to chimpanzees and the resulting infection characterized. In addition, several new viruses, related to GBV-A, have been discovered in New World monkeys. These are being further characterized. 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. 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. 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 an HEV-like agent from rats trapped in Los Angeles to laboratory rats of the same species (Rattus norvegicus). However, transmission has been difficult, suggesting that the virus replicates at low titer. We are currently attempting to obtain a partial sequence of the virus and to transmit it to other strains of rats that may be more permissive. Studies to determine if rat HEV is linked to human infection are in progress. Modern techniques of molecular biology have been used to discover new viruses in recent years. These are now being applied to prospectively collected sera from patients with transfusion-associated hepatitis in a search for new hepatitis viruses that may cause up to 15% of such hepatitis in the US. In an attempt to increase the sensitivity of specific virus discovery technologies (i.e., those capable of amplifying unique sequences without regard to the sequence) we have introduced modifications to existing techniques that have improved the sensitivity of the assay. Using the new technology, we have discovered two previously unrecognized bovine parvoviruses that contaminate most lots of bovine serum. This finding has implications for the safety of biologicals that are prepared with bovine serum. Kawasaki Disease is a life-threatening illness of young children. It has the epidemiologic characteristics of an infectious disease. The HVS is attempting to transmit a putative agent from acute phase clinical samples of children with Kawasaki Disease to nonhuman primates. Attempts to transmit an agent from minute quantities of an acute phase serum of plasma from Kawasaki patients to chimpanzees resulted in the demonstration of extreme hypersensitivity of the chimpanzee to the inoculum. This could be quantified by skin testing the animals with dilutions of the inoculum. To date, we have not found a single chimpanzee that was not hypersensitive to the inoculum, whereas other species of non-human primates were non-reactive. Initial characterization of the reactive substance in the acute phase plasma of the Kawasaki patients revealed that it was a heat-stable macromolecule. It is being further characterized.