An international team of researchers claim to haveuncovered how human immune cells remember previously encountered strains ofinfluenza. This discovery may pave the way to the development of a single universal flu shot to immunize people against all strains of the infectious disease for their entire lives.
Influenza is a virulent and infectious virus that affects countless scoresof people worldwide, and has resulted in several pandemicsthat have killed millions. One of the reasons that influenza is so hard toeradicate or inoculate against is the fact that it mutates so often, meaning the immune system can’t quickly swing known methods into action tocombat it.
A new breakthrough breakthrough involves an understanding of how "killer" CD8 + T cells – part of the body’s active immune system that travel throughout the bodyhunting down specific pathogens – rememberpreviously encountered virus strains.
In simple terms, killer Tcells hunt and destroy cells that are infected with viruses (and other diseasesor problems). They are activated when their specific receptor binds toan antigen complex (that is, the proteins found on the surface of a pathogen) aidedby a co-receptor on the T cell, which alerts it to the antigen’s presence. When activated,the T cell searches out cells with this antigen and destroys them.
No previous studies had managed to fully ascertain how killer T-cells remembered whichviruses had been encountered before, and it was not until the Australia-Sinocollaboration during the outbreak of the bird-borne H7N9 influenza virus inChina in 2013 that this mechanism was uncovered. With a 30 percentmortality rate and an almost 100 percent hospitalization rate for those infected, the H7N9 strain was particularly virulent, but also offered researchers theopportunity to come to grips with the virus’ infection methods first-hand.
"We’d never seen anything like H7N9," said Associate ProfessorKedzierska from the University of Melbourne. "The virus was infecting morepeople rapidly and nobody had immunity. Thankfully, we did manage to containthe virus but we knew we had come face-to-face with a potential pandemic thatcould kill millions of people around the world if the virus became able tospread between humans. After collecting samples from infected patients we foundthat people who couldn’t make these T cell flu assassins were dying. Thesefindings lead to the potential of moving from vaccines for specific influenza strainstoward developing a protection, which is based on T-cells."
In discovering that the CD8 + T cell response to new pathogens is directlyrelated to an individual body’s ability to activate these effector mechanisms,the team claims to have unravelled the requirements to initiate theseimmune responders no matter the influenza strain present. In other words,knowing the mechanism found in the influenza virus itself (and common to allstrains) required to activate an immune response may lead to the development ofinoculations that provide T-cells with the ability to recognize any influenzavirus, not just particular strains.
"Our extraordinary breakthrough could lead to the development of avaccine component that can protect against all new influenza viruses, with thepotential for future development of a one-off universal flu vaccine shot," said Associate ProfessorKedzierska. "This work will also help clinicians to make early predictionsof how well a patient’s immune system will respond to viruses so they canmanage early interventions such as artificial ventilation more effectively,particularly in cases where the patient is at risk of dying."
This work was led by the University of Melbourne, the Shanghai PublicHealth Clinical Center and Fudan University in China, with assistance from scientistsat St Jude Children’s Research Hospital, in Memphis, Tennessee.
The results of this research were recently published in the journal NatureCommunications.
Source: The University of Melbourne
