Use of neutralizing murine monoclonal antibodies to rabies glycoprotein in passive immunotherapy against rabies

Passive immunization is an important parameter of post exposure rabies prophylaxis. Two types of rabies immunoglobulin (RIGs) are currently available for Passive immunization against rabies i.e., human rabies immunoglobulin (HRIG) and equine rabies immunoglobulin (ERIG). The former is very expensive and not easily available and the latter causes side effects because of which its utility is limited. In the present study we have produced murine monoclonal antibodies (Mabs) to rabies glycoprotein (G) and studied their utility in passive immunization against rabies using animal models. Their efficacy was compared to commercially available ERIG both in terms of neutralizing titer and effective protein concentration. The neutralizing titers of these Mabs ranged from 1650-75,000 IU/mL by RFFIT. They belonged to the IgG 2 a subclass. The Mabs were able to protect 70-100% of mice and guinea pigs inoculated with rabies viruses, depending on the strain of the virus. These Mabs were found to be 2,000 times more potent than commercial ERIG in terms of effective protein concentration and neutralizing titer. Further studies are required to study their utility in humans exposed to rabies.