Researchers led by Drs. Louis Falo, Jr. and Andrea Gambotto from the University of Pittsburgh have been working to develop vaccines for other coronaviruses, including the one that causes Middle East Respiratory System (MERS). They adapted the system they had been developing to produce a candidate MERS vaccine to rapidly produce an experimental vaccine using the SARS-CoV-2 spike protein.
The team developed a method for delivering their MERS vaccine into mice using a microneedle patch. Such patches resemble a piece of Velcro, with hundreds of tiny microneedles made of sugar. The needles prick just into the skin and quickly dissolve, releasing the vaccine. Since the immune system is highly active in the skin, delivering vaccines this way may produce a more rapid and robust immune response than standard injections under the skin.
When delivered by microneedle patch to mice, three different experimental MERS vaccines induced the production of antibodies against the virus. These responses were stronger than the responses generated by regular injection of one of the vaccines along with a powerful immune stimulant (an adjuvant). Antibody levels continued to increase over time in mice vaccinated by microneedle patch—up to 55 weeks, when the experiments ended.
Using knowledge gained from development of the MERS vaccine, the team made a similar microneedle vaccine targeting the spike protein of SARS-CoV-2. The vaccine prompted robust antibody production in the mice within two weeks.
The vaccinated animals haven’t been tracked for enough time to see if the long-term immune response is equivalent to that observed with the MERS vaccines. The mice have also not yet been challenged with SARS-CoV-2 infection. However, the findings are promising in light of results from the similar MERS vaccine.