Genetic stability of Rift Valley fever virus MP-12 vaccine during serial passages in culture cells

Abstract

Rift Valley fever: Whole-virus vaccine alters the attenuation profile A vaccine candidate for Rift Valley fever virus can undergo mutations and partially revert to parental pathogenic strain. Rift Valley fever is a prolific infection that affects livestock and humans in Africa. Tetsuro Ikegami and Nandadeva Lokugamage, of the University of Texas Medical Branch, United States, tested the genetic stability of vaccine candidate MP-12, an attenuated form of the virus, through ‘serial passaging’—culturing the virus, establishing a new culture from a sample, then repeating the procedure to determine how the virus mutates in response to successive new environments. The duo found that after 25 ‘passages’, MP-12 reverted a part of attenuation mutations back to its original, pathogenic sequence. Though MP-12 redundantly encodes stable attenuation mutations, it will be important to use a seed lot system to avoid the attenuation profile changes.