Live and Inactivated Vaccines of Group B Arboviruses: Role of Neutralizing Antibody and Serum Protective Factor

Abstract

IT is generally accepted that vaccination provides protection against subsequent viral disease either by stimulating the production of neutralizing antibody or by sensitizing the antibody producing cells so that on infection neutralizing antibody is produced¹. The results presented here suggest that inactivated group B arbovirus vaccines depend chiefly on the production of neutralizing antibody to provide protection against subsequent viral disease, whereas live group B arbovirus vaccines depend not only on neutralizing antibody but also on the presence of a new humoral substance which we call serum protective factor (SPF)² Indeed, using the immunosuppressant drug cyclophosphamide, serum protective factor can be shown to provide protection in the absence of any detectable neutralizing antibody response before the initiation of infection or subsequent to the challenge virus. Thus live group B arbovirus vaccines produce two lines of defence because neutralizing antibody acts on the virus before it penetrates the cell and serum protective factor acts on the cell to confer protection².