Antigenic Variation - Antigenic Variation in Viruses

Antigenic Variation in Viruses

Acute viral infections can be rapidly cleared by the immune system of the host. Nevertheless, some viral infections like influenza and HIV recur. The recurrence occurs due to the production of virions that are resistant to the neutralizing antibodies that were able to effectively block the infection. These virions can infect survivors of the acute infection caused by the original virus. These viruses have a structural plasticity that enables them to tolerate changes in amino acids in their structural proteins while still retaining their infectivity. There is a lot of diversity in the ability of viruses to exhibit such plasticity. They can range from as little as 3 serotypes as in poliovirus to nearly 100 serotypes in rhinovirus. Consequently, vaccines against poliovirus, measles and yellow fever confer lifetime immunity while a new influenza vaccine is needed every year.