What is antigenic drift and how does it benefit viruses?
Antigenic drift is the gradual accumulation of mutations in the genes that encode viral surface proteins, such as hemagglutinin (HA) in influenza viruses, leading to changes in the antigenic properties of the virus. These antigenic changes enable the virus to evade the immune system and cause recurrent infections in individuals who have previously been exposed to the virus or vaccinated against it.
Antigenic drift benefits viruses by allowing them to escape recognition and neutralization by the host immune response, thereby increasing their survival and replication in the host population. It also enables viruses to spread globally and cause seasonal outbreaks or pandemics, as the immune system of the population gradually loses the ability to recognize and control the virus due to its antigenic changes. This is particularly evident in influenza viruses, which undergo frequent antigenic drift and require annual updates of the vaccine to match the predominant circulating strains.
Antigenic drift is a continuous process of genetic variation in viruses, mainly influenza viruses. It occurs when viral genes mutate slightly over time, resulting in small changes in the viral surface proteins, such as hemagglutinin (HA) and neuraminidase (NA). These surface proteins are recognized by the immune system and antibodies, which the body produces to defend against infection.
The benefits of antigenic drift for viruses are two-fold:
1. Escape from immune recognition: By accumulating small genetic changes, viruses can modify their surface proteins just enough to evade recognition by pre-existing antibodies in the host population. This allows the virus to reinfect individuals who were previously exposed or vaccinated against a similar strain, leading to recurring epidemics or seasonal outbreaks.
2. Persistence and survival: Antigenic drift helps viruses persist in the population by avoiding complete immunity. As new variants appear, individuals with partial immunity might still be susceptible to infection, creating a constant pool of susceptible hosts. This continuous circulation facilitates the viral persistence in the population, ensuring long-term survival.
Overall, antigenic drift allows viruses to adapt and survive in the face of the host immune system, enabling them to cause repeated infections and continue spreading over time.