Spike protein

[5] The term is derived from the Greek peplos, "a loose outer garment",[3] "robe or cloak",[6] or "woman['s] mantle".

They may interact with cell-surface receptors located on the host cell and may have hemagglutinizing activity as a result, or in other cases they may be enzymes.

[6]: 362 Spikes or peplomers can be visible in electron micrograph images of enveloped viruses such as orthomyxoviruses, paramyxoviruses, rhabdoviruses, filoviruses, coronaviruses, bunyaviruses, arenaviruses, and retroviruses.

For this reason the spike protein has been the focus of development for COVID-19 vaccines in response to the COVID-19 pandemic caused by the virus SARS-CoV-2.

[11][12] A subgenus of the betacoronaviruses, known as embecoviruses (not including SARS-like coronaviruses), have an additional shorter surface protein known as hemagglutinin esterase.