Selection of coxsackievirus B4 variants with monoclonal antibodies results in attenuation.

Inoculation of suckling mice with coxsackievirus B4 (CB4) results in the death of a majority of the animals. In this study we selected antigenic variants of CB4 in the presence of neutralizing monoclonal antibodies and tested them to see whether they were attenuated. Antigenic variants selected with a single antibody showed little or no attenuation by producing a high mortality (60 to 100%). A double variant selected with two antibodies showed considerable attenuation by causing only 25% mortality. A triple variant selected with three antibodies was almost completely attenuated (killed only 5% of the animals). Polypeptides from these variants were tested for their ability to interact with the monoclonal antibodies used for their selection. These studies showed that resistance of variant virus to neutralization in general was due to the inability of the antibody to bind to the virus. However, one of the antibodies could bind but not neutralize the virus, perhaps due to an alteration in the epitope. It is concluded that selection of CB4 variants using more than one neutralizing monoclonal antibody can lead to attenuation of the virus.