Immune cells are able to recognize whether a bacteria is viable or not. This new evidence is remarkable, but why does this matter? Vaccines used to ward off disease come in two main varieties, live-attenuated (viable) or killed (dead) forms. Use of viable vaccines produces a more robust immune response. Until now, the underlying reason why has remained unknown. Sander et. al. (Nature 474: 385-389, June 10, 2011) demonstrate that an underlying reason for this is that the immune system can differentiate between viable and non-viable agents.
The presence (and detection) of prokaryotic mRNA signals to the immune system that the invading bacteria is viable and, therefore, potentially infectious. As a result, a strong immune response is initiated. It is not just presence of prokaryotic mRNA, however, but specifically, the immune cells recognize a lack of the 3’ -polyA tail on this mRNA. This means that killed virus that can retain the prokaryotic mRNA (i.e. killing with paraformaldehyde retains the mRNA) or is vaccines that are augmented with prokaryotic mRNA can produce an enhanced immune response. This could have a significant impact on vaccine design and development.
n3 science communications, llc