Association of SARS-CoV-2 Nucleocapsid Protein Mutations with Patient Demographic and Clinical Characteristics during the Delta and Omicron Waves

SARS-CoV-2 genomic mutations outside the spike protein that may increase transmissibility and disease severity have not been well characterized. This study identified mutations in the nucleocapsid protein and their possible association with patient characteristics. We analyzed 695 samples from patients with confirmed COVID-19 in Saudi Arabia between April 1, 2021, and April 30, 2022. Nucleocapsid protein mutations were identified through whole genome sequencing. Χ 2 tests and T tests assessed associations between mutations and patient characteristics. Logistic regression estimated risk of intensive care unit (ICU) admission or death. Of 60 mutations identified, R203K was most common followed by G204R, P13L, and E31del, R32del, and S33del. These mutations were associated with reduced risk of ICU admission. P13L, E31del, R32del, and S33del were also associated with reduced risk of death. By contrast, D63G, R203M, and D377Y were associated with increased risk of ICU admission. Most mutations were detected in the SR-rich region, which was associated with low risk of death. C-tail and central linker regions were associated with increased risk of ICU admission, whereas the N-arm region was associated with reduced ICU admission risk. Some SARS-CoV-2 nucleocapsid amino acid mutations may enhance viral infection and COVID-19 disease severity.