Thus the vaccines of the future can be kept out of the fridge

From the newest anti-Covid vaccines to those used for a long time against many infectious diseases, most biological preparations that stimulate the immune system to produce antibodies against pathogens must be transported and stored at very low temperatures to prevent the product from becoming degradation. There cold chain represents a major obstacle to vaccination in countries such as Mali or Bangladesh, where up to 90% of health facilities do not have adequate refrigeration systems. To solve the problem, some researchers are working on formulations that can be kept at room temperature, although several hurdles remain to be overcome before the goal can be achieved. These largely depend on the strategy adopted for the formulation of the drug itself, i.e. on the active ingredient capable of inducing the immune response. In fact, there are vaccines based on RNA, DNA, viruses or bacteria that are attenuated or inactivated, or parts of the pathogen such as peptides or proteins. The latter are relatively stable, but other types, such as those incorporating inactivated or attenuated forms of the microorganism, are particularly susceptible to temperature changes.

A strategy used to make the temperature of different formulations more stable is the so-called Molecular “cage”, that is a silica cage which, in the case of the work carried out by Asel Sartbaeva, a chemist at the University of Bath, is used to stabilize the proteins of the vaccine for diphtheria, tetanus and pertussis (DTP), a formulation which as a rule must be kept at a temperature between 2 ° C and 8 ° C. “Silica – explained Sartbaeva in an article on Scienceit is quite malleable”Allowing a perfect adaptation to proteins. Attracted to regions of positively charged biomolecules, silica forms a kind of network which exactly matches the contours of the proteins. This strategy, already tested in animal models, allowed this vaccine to be stored for at least one month at room temperature and 2 hours at 80 ° C, according to data from the study published in Nature Scientific Reports.

Another approach employed by the researchers is the “Fruit Roll-Up” method which plans to enclose the viral vector (adenovirus) on which multiple vaccines are based, including several anti-Covid sera, inside a shell of sugars and salts. Developed by the University of Texas team led by Maria Croyle, this shell has been shown to keep an Ebola vaccine stable at room temperature, according to an Advance Science study. The vaccine thus enclosed can be administered orally, by dissolving the shell under the tongue, as well as being able to be reconstituted and then inoculated intramuscularly. The researchers believe that by changing the sugar and salt mixture, the method could work for other vaccines and drugs, including flu shots.

In the meantime, even for messenger RNA vaccines, such as the anti-Covid of Moderna and Pfizer-BionTech which currently foresee freezing temperatures to be stored, solutions are being studied that will allow to solve the problem of the cold chain. Specifically, just this month, Pfizer started clinical trials on one freeze-dried version of his vaccine, so that it can be stable at normal refrigerator temperatures, with the first results expected by the end of May.

Another strategy that could be employed is to modify the lipid nanoparticles that envelop the mRna molecule in the vaccine and are responsible for stringent storage requirements: the first nanoparticle that can be transported at refrigerator temperatures was designed by Seattle-based biotechnology company HDT Bio. According to Amit Khandhar, the company’s research manager, the nanoparticles can be transported in regular refrigerators, then combined with RNA just before inoculation. The approach will be tested in India, as part of the experimentation of a vaccine candidate that will use the nanoparticles of HDT Bio.

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