Benzinga | Oct 12, 2020 07:03AM EDT

Altimmune Publishes Pre-Clinical Data on its COVID-19 Vaccine Candidate

Key Findings of the Study

In the BioRxiv.org publication, the authors present data demonstrating strong activation of all three arms of the adaptive immune system following a single intranasal dose of AdCOVID. These data, conducted in two strains of mice, show that AdCOVID stimulated strong immune responses including:

* Serum Neutralizing Immunity: AdCOVID elicited a median serum neutralization titer against wild-type SARS-CoV-2 virus of up to 1:563 one-month post-vaccination in a 50% focus reduction neutralization test (FRNT). For context, this level of neutralizing activity was at least 3-fold higher than the minimum titer recommended by the FDA for convalescent plasma used in the treatment of COVID-19.

* T cell Immunity: AdCOVID stimulated both CD4+ and CD8+ antigen-specific T cell responses following a single intranasal vaccination. The response was focused in the lungs of the vaccinated mice and was biased toward CD8+ T cells. A significant fraction of the CD8+ T cells in the lung were found to be non-circulating tissue-resident memory (Trm) T cells, which have been shown to play a front-line role in fighting respiratory viral infections.

* Mucosal Immunity: Nasal mucosal immunity is a local type of immunity that has the potential to stop both infection and transmission of the virus. Significantly, only an intranasal vaccine can activate this important type of immunity. AdCOVID induced a 29-fold increase in mucosal IgA specific to the RBD, well above the level associated with protection in clinical studies of mucosal influenza vaccines where a 2 to 4-fold increase in IgA was found to be correlated with protection. The observed IgA response, together with the lung-associated Trm T cell response noted above, provided an additional level of immune response that may provide enhanced protection against COVID-19 disease and transmission.

"Our collaboration with UAB has been extremely productive and the preclinical data for AdCOVID continue to show promising differentiation from other COVID-19 vaccine candidates", said Dr. Scot Roberts, Ph.D., Chief Scientific Officer for Altimmune. "Intranasal vaccination represents an attractive strategy to prevent COVID-19 infection, as the nasal cavity comprises the first line of defense against the SARS-CoV-2 virus prior to entry into the lungs. By stimulating mucosal antibody and T cell immunity, along with potent systemic neutralizing antibody titers, all three arms of the immune system can work in concert to prevent and control infection."

Dr. Roberts continued, "Current first-generation COVID-19 vaccines, which are given by intramuscular injection are unable to activate nasal mucosal immunity, which may not only be critical for mounting a comprehensive immune response, but may also prevent further spread of the virus by blocking transmission."

"We are delighted that our work has provided convincing data on the potential of AdCOVID to provide broad and effective immune response, and look forward to continued collaboration with Altimmune on this important program," said Dr. Frances Lund, Ph.D., Charles H. McCauley Professor and Chair of the UAB Department of Microbiology and principal investigator and co-author of the manuscript.