Upon viral entry into the body and also after vaccination, the body produces virus neutralizing antibodies which bind and inactivate the virus. Specific regions of the G protein have been shown to be most antigenic in leading to the production of virus neutralizing antibodies. These antigenic sites, or epitopes, are categorized into regions I-IV and minor site a. Previous work has demonstrated that antigenic sites II and III are most commonly targeted by natural neutralizing antibodies.[14] Additionally, a monoclonal antibody with neutralizing functionality has been demonstrated to target antigenic site I.[15] Other proteins, such as the nucleoprotein, have been shown to be unable to elicit production of virus neutralizing antibodies.[16] The epitopes which bind neutralizing antibodies are both linear and conformational.[17]