Environmental Genomics
Environmental health
Driving pathogen diversity
Many diseases pass through multiple hosts and are therefore subject to a wide diversity of host organism environments. These environments can influence how pathogens evolve and diversify. Genomic tools can provide us with a better understanding of processes which can cause pathogens to diversify. This is important if we are to understand the evolution of virulence and drug resistance.
NERC scientists investigated the genetic structure of the Great Island virus, which infects seabirds via ticks. If the birds become infected, their immune system will develop antibodies to attack the virus. Over time, virus populations can evolve to develop a resistance to these antibodies. The scientists sought to identify the particular genes within the virus that have become selected for this trait.
The outer surface of the virus determines whether or not the host's antibodies
manage to inactivate it. The two genes that produce the outer surface of
the virus particle had a high proportion of nucleotide mutations that cause
changes to its protein structure. Such changes to surface proteins of pathogens
are usually driven by host antibodies. Field experiments showed that the
Great Island virus is indeed subject to intense selection due to the effects
of the birds' antibodies.
The scientists found that strains of virus sampled from seabird colonies around the UK exhibit little genetic difference from those in Norway or North America, but, like the influenza virus, different strains regularly swap segments containing whole genes. The significance of this is that a selected trait for resistance could be transmitted intact from one virus to another.
Despite this swapping, scientists found that some of the genes involved in virus immunity are distributed across different segments. This would imply that some types of resistance can be transmitted intact whilst others require transmission of multiple segments. It might also imply that there is more than one type of resistance.