Antigenic Variation in Viruses

Persistent virus Infections represent an immunologlcal paradox, in that viruses persist in the face of normal immune responses. The classical serological studies on viruses causing acute Infections established a remarkable degree of antigen and structural uniformity within each virus type. The obvious exception has been Influenza which, because of changes in specific antigenic determinants, is able to generate a variety of antigenic variants which can elude the immune responses of hosts previously infected with slightly differing viruses. The phenomenon of high mutability and antigenic variation previously associated uniquely with influenza virus, appears to be a more general one. Recent studies indicate that many viruses, long thought to be antlgenlcally stable, are known to exist in multiple antigenic forms, both in the laboratory and in nature. Data will be presented here that this is true as well of measles virus, thought previously to be the most antlgenlcally stable of any of the common acute viruses. The biological implications and possible role of viral antigenic changes in human disease, particularly in relation to persistent infections, will be discussed in this article.