On Jul. 15, 2021, iBio announced that preclinical studies of IBIO-202, its subunit vaccine candidate that targets the nucleocapsid protein (‘N protein’) of SARS-CoV-2, demonstrated a robust, antigen-specific, memory T-cell response.

Data on commercially available COVID-19 vaccines – all of which target the spike protein (“S protein”) – suggests that neutralizing titers are effective, but likely to wane over time. In addition, the robustness of T-cell priming and cellular immunity achieved by S protein-directed vaccines may not be sufficient to create a durable immune response, especially in the context of emerging variant strains of the virus. In contrast, the N protein gene is more conserved and stable than the spike, with 90% amino acid homology and fewer mutations over time. Notably, the SARS-CoV-2 N protein shares substantial sequence conservation with the nucleocapsid of other coronaviruses.

It has been observed that the N protein can induce SARS-specific T-cell proliferation. The IBIO-202 immunization data are consistent with that, as a strong, cytotoxic, memory T-cell response was seen, rather than an inflammatory response. In addition, T-cell priming was achieved via both intramuscular and intranasal administration, allowing for the further exploration of multiple routes of administration and their respective benefits.