Search For New Hepatitis Agents

来自美国急性或慢性非甲、乙、丙、丁、戊型肝炎患者的临床样本正在进行研究，以寻找可传播病原体的生物学、血清学或分子证据。暴发型非甲至戊型肝炎患者仍是一个诊断之谜，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。另一种水媒肝炎病毒存在的证据来自印度和沙特阿拉伯的血清流行病学研究。我们正试图从这类患者的临床标本中传播一种病毒。几年前，据报道，一种肝炎病毒可以从一名非甲非乙型肝炎患者传播给猕猴。这种被称为GB试剂的药物可以在绒猴中连续传播，并具有部分特征。最近，Gb病毒被克隆和测序，并被证明是两个独立的病毒(GBV-A和GBV-B)，每个病毒都与丙型肝炎病毒和一种以前未被识别的人类病毒(GBV-C)有较远的亲缘关系。GB试剂和新发现的人类病毒正在灵长类动物身上和体外进行研究。构建了具有感染性的GBV-B基因。到目前为止，新发现的人类病毒(GBV-C)已传播给黑猩猩，并对由此产生的感染进行了表征。此外，在新大陆猴子身上发现了几种与GBV-A相关的新病毒。这些正在被进一步描述。获得了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、独特的HEV毒株，并对其进行了鉴定。对猪饲养员和配对献血者的血清流行病学研究表明，猪饲养员对HEV的抗体过剩，这表明该病毒可能是通过人畜传播的。野鼠感染HEV的类似血清学证据也已获得，正在寻找感染剂。到目前为止，我们已经成功地将一种类似HEV的病毒从被困在洛杉矶的大鼠传播到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该病毒的部分序列，并将其传播给可能更允许的其他品系的老鼠。确定老鼠HEV是否与人类感染有关的研究正在进行中。近年来，现代分子生物学技术被用来发现新的病毒。这些药物现在被应用于预期从输血相关性肝炎患者中收集的血清，以寻找新的肝炎病毒，这些病毒可能导致美国高达15%的此类肝炎。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，提高了分析的灵敏度。使用这项新技术，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品的安全性有一定的影响。 川崎病是一种危及幼儿生命的疾病。它具有传染病的流行病学特征。人类免疫系统正试图将川崎病患儿急性期临床样本中的一种推定病原体传播给非人类灵长类动物。试图从川崎患者的急性期血浆中微量的血清中传播一种试剂给黑猩猩，结果显示黑猩猩对疫苗非常敏感。这可以通过用稀释的接种剂对动物进行皮肤测试来量化。到目前为止，我们还没有发现一只黑猩猩对疫苗不敏感，而其他种类的非人类灵长类动物对疫苗没有反应。对川崎患者急性期血浆中活性物质的初步表征表明，它是一种热稳定的大分子。它正在被进一步描述。

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.