PROJECT SUMMARY This proposal aims to rapidly generate vaccine candidates against the 2019 novel coronavirus SARS-CoV- 2. Since its emergence about three months ago, this virus has caused more than 120,000 infections and 4,300 deaths worldwide and is rapidly spreading to virtually every country including the United States. This global health emergency must be immediately addressed by rapidly developing medial countermeasures. Our bacteriophage (phage) T4 vaccine platform is uniquely suited to address this threat. Developed in PI's laboratory, the T4 vaccines have been proven to generate robust humoral as well as cellular immune responses and confer complete protection against anthrax and plague in multiple animal models including mice, rats, rabbits, and macaques. The T4 vaccines do not need an adjuvant as its surface structure mimics the Pathogen- Associated Molecular Patterns (PAMPs) of viral pathogens and stimulate strong innate and adaptive immunity. The 120 x 86 nm phage T4 capsid is packaged with 171 kb genome and decorated with two non-essential outer capsid proteins; 870 molecules of Soc (small outer capsid protein) and 155 copies of Hoc (highly antigenic outer capsid protein). In specific aim 1, a series of T4-corona phages will be constructed by incorporating SARS- CoV-2 virion components individually and in combinations, by CRISPR engineering. The gene encoding the entire spike ectodomain will be inserted into phage genome under the control of the strong CAG promoter. Upon immunization, host cells (myocytes and antigen presenting cells at the site of immunization) take up phage particles and secrete the ectodomain trimers continuously, stimulating the immune system for weeks to months. The gene for the receptor binding domain (RBD) of S protein will be inserted such that the RBD will be expressed in host cells, as well as in E. coli as a Soc fusion protein which will then be displayed on phage capsid up to 870 copies per capsid. The ectodomain of E protein will be fused to Hoc and displayed up to 155 copies per capsid. Finally, ~400 copies of N protein will be packaged inside the capsid as part of the scaffolding core. In specific aim 2, the above T4-corona recombinant phages will be evaluated for elicitation of SARS-CoV- 2 virion-specific immune responses in a mouse model. Mice will be immunized with purified phage particles intramuscularly and the immune responses will be quantified by ELISA, competitive receptor binding, ELISpot, and virus neutralization assays. We expect that the T4-corona vaccines will elicit robust antibody and cellular responses and also inform which candidate(s) will be most effective in blocking SARS-CoV-2 infection. We have streamlined the CRISPR engineering such that the proposed T4 vaccines can be constructed in about 4 weeks and the animal testing can be completed in about 12 weeks. The candidate vaccines will then be available for clinical trials and vaccine manufacture. The T4 vaccine will be exceed...