ImmunityBio, Inc., a clinical-stage immunotherapy company, reported initial data indicating that a single subcutaneous injection of the company’s COVID-19 vaccine candidate in healthy Phase 1 clinical study participants stimulates the generation of T cells that are reactive to the spike (S) and nucleocapsid (N) protein antigens delivered by the vaccine. Just 14-16 days after the single dose, the mean level of T cells generated in response to the hAd5 S+N T cell vaccine were ten times higher for N specific T cells. By day 21, both S and N T cell responses achieved levels ten times higher as compared to pre-vaccination levels. These preliminary findings were published in a preprint server medRxiv (link) titled, “Single Prime hAd5 Spike (S) + Nucleocapsid (N) Dual Antigen Vaccination of Healthy Volunteers Induces a Ten-Fold Increase in Mean S and N T Cell Responses Equivalent to T Cell Responses from Patients Previously Infected with SARS-CoV-2”.

The mean T cell levels seen in the vaccinated participants were equivalent to those for patients recovered from infection by the SARS-CoV-2 virus. ImmunityBio reported previously that T cells isolated from previously infected individuals react to the antigens delivered by the vaccine, indicating that immune responses to the vaccine could be protective against SARS-CoV-2 infection and COVID-19 illness.

The company also announced that it employed in silico techniques to examine T cell epitopes of SARS-CoV-2 variants as compared to the first-wave strain. The analysis indicated that T cell epitopes from the first wave and the variants largely overlapped, indicating that the hAd5 S+N vaccine has the potential to provide protection against both the first wave SARS-CoV-2 as well as against variants of SARS-CoV-2, including the B.1.1.7 variant (N501Y mutation) in the United Kingdom and the B.1.351 variant (E484K, K417N and N501Y mutations) identified in South Africa.

This T cell epitope analysis provides additional evidence of the potential for the vaccine candidate to serve as an universal booster for patients who have received an initial S protein only vaccine by not only fortifying S activated T cells, but also broadening protection by the addition of N activated T cells. This could provide additional protection against variants and longer-term protection against the virus.

“These data further validate the path we have taken in designing our vaccine candidate to target both the S and N proteins in order to increase T cell responses,” said Dr. Patrick Soon-Shiong, Founder and Executive Chairman of ImmunityBio. “Current vaccines target the S protein, leaving open the potential for antigen drift (mutation) and rendering these vaccines to be less effective against variants. Our goal is to develop the second-generation COVID-19 vaccine which is room temperature stable, can be self-administered orally and generates both antibody and long-term T cell immunity. Our Phase Ib clinical trials are ongoing to explore which combination of subcutaneous, oral or sublingual forms of hAd5 S+N would provide maximum protection against SARS-CoV-2.”