The SARS-Cov-2 coronavirus pandemic, which causes COVID-19 disease, has caused a global health and economic crisis. The laboratories are therefore a hotbed of data and clinical trials with the aim of providing, as soon as possible, an effective vaccine or viral treatment. Several vaccine prototypes have already started the first phases to test their effectiveness.
Here’s another one, this time, by scientists from the University of Iowa and the University of Georgia. With one nuance: the prototype is not exactly a vaccine against COVID-19, but a vaccine against MERS (Middle East Respiratory Syndrome), another coronavirus that causes a respiratory disease, and that could be considered a cousin of the coronavirus causing the current pandemic. Because they are so similar, researchers believe this vaccine may be promising for developing vaccines against other diseases caused by a coronavirus, including COVID-19. This vaccine against MERS, moreover, is the most effective against this disease to date.
MERS and COVID-19 are caused by a coronavirus. MERS is more fatal in about a third of known cases, but there have only been 2,494 cases since 2012, when the first case appeared. In contrast, the coronavirus caused by COVID-19 has a much faster and effective spread, accounting for more than two million confirmed cases since late 2019.
How does the vaccine work?
The vaccine in question uses another type of virus, a harmless one, as a vehicle to deliver a MERS coronavirus protein into the cells to generate an immune response.
It consists of a harmless parainfluenza virus (PIV5), which carries the MERS spiked protein, which this coronavirus uses to infect cells (the SARS-Cov-2 coronavirus also uses a similar procedure to infect). The results are very promising, given that all vaccinated mice survived a lethal dose of the MERS coronavirus, as described in a paper published on 7 April in the magazine mBio. The application consisted of only a relatively low dose of the vaccine administered to mice via nose.
The same strategy, for COVID-19
Not only do scientists plan to use the same method to make a vaccine against COVID-19, but they already have several candidate compounds to be the next vaccine.
As the researchers write: "Our new study indicates that PIV5 may be a useful vaccine platform for emerging coronavirus diseases, including SARS-Cov-2, the virus that causes the COVID-19 pandemic. Using the same strategy, PIV5-based vaccine candidates have been generated that express the SARS-Cov-2 spigot protein. Further animal studies to assess the capacity of PIV5-based vaccines to prevent SARS-Cov-2 disease.
More details about mouse-generated immunity: When researchers analysed the immune responses generated by the vaccine, they found that both antibodies and protective T cells were produced. However, the antibody response was rather weak and it seems very likely that the protective effect of the vaccine is due to the response of T cells in the lungs of mice.
The advantages of using a harmless virus as a 'transport'
As explained earlier, the vaccine uses a harmless virus as a vehicle to transport the proteins in the spike of the coronavirus. This virus, PIV5, has many advantages as a carrier: first, because it can infect many different mammals, including humans, without causing disease (since it is a harmless virus). On the other hand, PIV5 is also being investigated as a means for a vaccine for other respiratory diseases, including respiratory syncytial virus (RSV) and common influenza.
In addition, the fact that a low dose of the vaccine was sufficient to protect mice could be beneficial in creating enough vaccine to cause mass immunization in the population, to vaccinate many people.