Researchers at the Columbia University Medical Center have recently found out how they could induce flu immunity that lasts longer and protects against an extensive set of strains than conventional methods. The investigators are confident that to attain a comprehensive immunity, tissue-resident memory T cells need to be activated. According to tests on mice, intranasal administration of live attenuated virus is the way to go.
The group at Columbia University Medical Center hypothesizes that if somehow they could boost the TRM present in the lung tissue, it could lead to better immunity. They argue that TRM of lungs will initiate a local and rapid response upon influenza as lungs is their primary infection site. Though every healthy human has a population of TRM in his/her lungs, an amplified colony will reduce the severity of the infection.
The aforementioned claim has been backed up by research; in mice a boosted population of TSM has proved to be more defensive against flu infections than a boosted population of circulating T cells. It is evident from the research that TRM populations will soon be a target for influenza vaccines.
Hence, the team in Colombia tested if vaccines currently present in the market could do the trick and increase TRM populations. And luckily they found a nominee, an intra-nasal administration of a live attenuated virus. The vaccine essentially increased TRM population in mice. But it should be kept in mind that so far this has only been realized in pre-clinical trials on mice.
It is still to be determined in humans if the correlation between TSM population and influenza protection can be held and whether TSM count really is a better measure of a vaccine’s effectiveness or not. Even in the case TSM count isn’t downright better, it could be integrated in the list of heuristics used to formulate an optimal vaccine, as Donna Farber, a PhD professor at Columbia University, puts it: “Vaccine developers may want to combine these attributes in a universal vaccine that is capable of offering protection against the familiar strains of influenza we expect to see during a typical yearly outbreak as well as novel strains that can cause a pandemic.”
Brushing Up The Basics Of Immunology Targeted By The Vaccines
The influenza virus comes in three major categories: type A, type B and type C,with type A and B being responsible for the seasonal illness. A typical vaccine for the influenza virus will protect you from multiple types (multivalent), the problem however arises due to the appearance of new strains within the A and B types of influenza. To counter these emergent strains, new vaccine needs to be prepared each year that is designed to specifically counter the latest strains.
The reason for the emergence of these new influenza strains is the fact that the virus evolves its surface antigen, hence it becomes difficult to identify. Each year the virus updates its surface antigen. Conventional vaccines enable the body to combat viruses by helping identify the virus by its surface antigen, and that is exactly why you need a new influenza vaccine each year.
But that’s not all the body has in store. We know that among the body’s natural repertoire of defense mechanisms, there is a certain type of white blood cells called memory T cells that recognize the virus not by its surface antigen but by the internal antigens of the virus, preserved protein that don’t mutate like surface antigens. Therefore, if somehow we could prime these cells for an infection, we won’t have to worry about up-and-coming strains outsmarting our immune system.
The positive side of stimulating memory T cells is that since they are in charge of remembering all the previous infections the body has been through, the protection they grant is long lasting.
This is exactly what scientists are striving for: develop vaccines that specifically boost the number of memory T cells which in turn target the flu virus. Conventional flu vaccines do boost the number of memory T cells but here’s the catch, they don’t enhance the ‘right’ type of memory T cells.
Amongst the three types of memory T cells are the tissue resident memory T cells (TRM). As is evident from their name, these cells stay in a particular tissue type and don’t enter the circulatory system via blood. The memory T cells that experience an upsurge after conventional flu immunization are those present in the circulatory system.
In the event the mice model’s pattern holds for humans, we may have gotten one step closer to the ultimate goal of influenza vaccine research: the development of a universal influenza vaccine. But until then, brace yourselves for your annual flu shots.