Serial passage

Serial passage is a virus attenuation technique developed originally by Louis Pasteur in the 1880's. It is similar to selective breeding, and can be used to create an attenuated strain of a virus to develop vaccines, or to increase the virulence of a viral strain in order to create epidemics.

The process involves infecting a series of host organisms with a virus. Each time the virus is given some time to incubate, and then the next host is infected with the incubated virus. The virus may mutate repeatedly into a form that is resistant to a wide variety of host immune system defenses, or a weaker strain may result.

Pasteur produced an early rabies vaccine by using serial passage to transmit the virus until an attenuated developed which could be used to stimulate an immune response without causing a pathological infection.

Scientists have observed that non-virulent forms of HIV can give rise to virulent strains after serial passage occurs in primates.

Serial passage is also used in antimicrobial testing to determine how quickly an organism can acquire resistance to an antibiotic.