Inactivated SARS-CoV-2, Lineage B.1_2020 (NY-Wadsworth-103677-01/2020)

SARS-CoV-2, the causative agent of COVID-19, is a highly contagious virus primarily transmitted through respiratory droplets and aerosols expelled by infected individuals when they cough, sneeze, or talk. It can also be transmitted through fomites (contaminated surfaces) and, less commonly, the fecal-oral route. The virus enters host cells by binding its spike (S) protein to the angiotensin-converting enzyme 2 (ACE2) receptor, which is abundantly expressed in respiratory epithelial cells, as well as in the heart, kidneys, and gastrointestinal tract. Following viral attachment, membrane fusion occurs, releasing its RNA genome into the host cytoplasm, hijacking the cellular machinery for replication. The immune response to infection can range from asymptomatic to severe, with cytokine storms and acute respiratory distress syndrome (ARDS) observed in critically ill cases.

SARS-CoV-2 is an enveloped, positive-sense, single-stranded RNA virus belonging to the genus Betacoronavirus. The spherical virion is approximately 50-200 nanometers in diameter and is studded with spike (S), membrane (M), and envelope (E) proteins, which facilitate entry and assembly into host cells. The nucleocapsid (N) protein binds to the RNA genome to form a helical nucleocapsid encased in a lipid bilayer membrane. The genome is approximately 30 kilobases long and encodes 16 nonstructural proteins (nsp1-16) involved in replication and transcription, as well as structural and accessory proteins (S, M, E, N, and open reading frames). The S protein is essential for infectivity and consists of two subunits: S1 mediates receptor binding, and S2 drives membrane fusion.