Sars cov 2 mrna
Most human medicines, including vaccines, are small molecules or proteins. A decade ago, a company called Moderna started on the premise of messenger RNA (mRNA) as a therapy. Only two RNA-based therapies have been approved, neither being RNA messenger. While it’s not the only company focused on mRNA, it’s the front runner by far. Within eight years, it became the most valued biotechnology company before breaking a public offering record. Their stock has tripled to over $ 60 a share as the pandemic swept across the world.
A quick look at their drugs in development reveals a laundry list of therapies for rare metabolic disorders, cancers, heart failure, and a host of pathogens like Zika virus, Epstein-Barr virus, and the novel coronavirus SARS-CoV-2. It is the mRNA technology itself that enables them to tackle such diverse diseases with a single platform.
The premise of any vaccine is to induce a long-lived immune “memory” in the form of B and T cells. Upon any encounter with a pathogen (which can be bacteria or viruses), these cells will recognize the danger and fight it off by destroying the pathogen and pathogen-infected cells.
The danger signal takes the form of an antigen, a molecule that notifies the immune system of a pathogen. For SARS-CoV-2, the antigen targeted by B and T cells is usually a protruding spike protein on the surface of the virus. The challenge in vaccination is inducing this response, which requires a handshake between an antigen-presenting cell and a specific type of T cell, without getting people sick. It’s the antigen peptide (smaller sections of antigen molecule) presented in this interaction that determines the target of the immune response.
Common vaccines are weakened or inactivated versions of the virus, like the yearly flu or the polio vaccine children receive 2 months after birth. A huge variety of antigens, some useful and some not, can be presented since cells are receiving the entirety of the virus.
Newer vaccines utilize other engineered, well-studied doses containing specific regions of the target pathogen to create specific immune reactions. Moderna’s challenger in the race for a COVID-19 vaccine is based on this concept. Astra Zeneca’s vaccine candidate is a nonreplicating, weakened version of the common cold virus that contains the SARS-CoV-2 spike protein. This approach has been successful before as the first Ebola vaccine.
Other approaches simply inject the proteins researchers want the body to recognize as a danger, along with other molecules to raise the alarm initially for the vaccine response. For SARS-CoV-2, the surface spike protein is the most common target to be tested for vaccines.