Table 2.

Viral proteins: functions and characteristics.

Viral proteins	Functions	Characteristics	Refs
Envelop protein	(1)Recognize the corresponding receptors on the host cell membrane, mediate adhesion and entry into host cells; (2)Stabilize the envelope structure; (3)Transport substances.	(1)Highly antigenic, as a major inducer of neutralizing antibodies; (2)Highly variable. In diagnosis, their antibodies may only recognize certain strains of the same virus family due to their high variability; (3)Located outside the virion, enabling direct detection of intact virions.	[65,66]
Capsid protein	(1)Protect the viral genome; (2)Mediating self-assembly; (3)Intracellular trafficking; (4)Evasion of host intrinsic, innate and adaptive immunity; (5)Attachment, entry, and genome release.	(1)Some key neutralization sites (epitopes); (2)Some variability, but is generally more conserved than envelope proteins; (3)Ability to detect intact virus particles.	[67]
Nucleoprotein	(1)Plays an important role in virion replication, transcription, and packaging.	(1)Highly conserved, often used as a target protein in commercially available kits; (2)The cell lysate is required for detection.	[68]
Functional protein	(1)Enzymes such as reverse transcriptase, and RNA replicase; (2)As a primer for nucleic acid replication.	(1)Targets for traditional antiviral drug development; (2)Rarely used as a target for viral diagnostics; (3)The cell lysate is required for detection.	[69]