IN VITRO NEUTRALIZATION OF HCV WITH MONOCLONAL ANTIBODIES BEFORE ADMINISTRATION

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Hepatitis C virus infections in man become chronic in approximately 85% percent of individuals exposed. At present there are an estimated 2.7 million chronically infected people in the United States and an estimated 200 million worldwide. There is no vaccine and therapy for chronic HCV infections is limited a combination of interferon and ribavirin, but treatment is successful in less than half the patients. For these reasons, vaccination and/or immuno-therapy may be an important alternative. The envelope proteins of HCV are an obvious target for any HCV vaccine. Unfortunately, due to poor cell culture systems for the virus, classic in vitro neutralization tests using antibodies cannot be performed using infectious virus. An alternative method to test the neutralization potential of an antibody is to combine HCV and antibody in vitro overnight and then test the inactivation of the virus by inoculation into chimpanzees. Recently, HIV-HCV pseudotype particles were developed that can be potentially used to test the neutralizing capabilities of antibodies in vitro without the use of an animal model. However, it needs to be established that the pseudotype particles do represent authentic HCV particles and that antibodies that neutralize these pseudotype particles also neutralize HCV using an in vivo system. The only way to establish this is through a comparison of monoclonal antibodies shown to neutralize pseudotypes in vitro with an in vitro neutralization test using the chimpanzee as a read-out. This study aims to make this comparison. If a firm correlation is established the need for chimpanzees to determine neutralizing antibodies will be greatly reduced. 100 chimpanzee infectious doses of monoclonal HCV will be combined with each of 4 monoclonal antibodies in vitro overnight. Following incubation the combined mixtures will be inoculated i.v. into chimpanzees. (Total volume approx 5ml). Animals will be bled weekly and monitored for HCV viremia. If no infection is indicated after 8 weeks the animals will be challenged with un-neutralized HCV to demonstrate infectivity.