Virus proteins and peptides are fundamental to viral structure, replication, and pathogenesis, and represent key targets for antiviral strategies. Viral proteins are broadly classified as structural proteins, which form the virion architecture, and nonstructural proteins, which function inside infected host cells. Peptides derived from viral or host proteins have emerged as promising antiviral agents, capable of inhibiting virus entry, replication, or stimulating immune responses. 

Classification and Roles of Viral Proteins

Viral proteins are categorized into:

• Structural proteins: These include capsid proteins that form the protective shell (nucleocapsid) around the viral genome and envelope glycoproteins embedded in lipid bilayers acquired from host membranes. The capsid proteins assemble into highly symmetrical structures, such as icosahedral or helical forms, ensuring genome protection and facilitating host cell attachment. The matrix protein layer, found between the nucleocapsid and envelope in enveloped viruses, provides structural rigidity and stability to the virion.
• Nonstructural proteins: Expressed inside infected cells but not packaged into virions, these proteins regulate viral genome replication, transcription, and modulation of host cell machinery. Examples include viral proteases that cleave polyproteins into functional units, RNA-dependent RNA polymerases, and proteins that counteract host immune defenses.

Viral Peptides as Antiviral Agents

Recent studies have identified peptides with the ability to inhibit viral entry and infection. Membrane-transiting peptides, originally known for their capacity to cross plasma membranes and deliver cargo into cells, have demonstrated antiviral activity by blocking virus entry. For example, four distinct peptides inhibited herpes simplex virus entry at low micromolar concentrations, some reversibly blocking entry without permanently inactivating virions, while others caused irreversible virion inactivation at higher concentrations.

Peptides can inhibit viruses by:

• Directly blocking receptor binding or membrane fusion processes necessary for viral entry.
• Inducing viral particle lysis or destabilization.
• Triggering apoptosis in infected cells to reduce viral load, as shown by peptides derived from tumor necrosis factor reducing HIV infection in vitro.

Virus proteins and peptides play multifaceted roles in viral life cycles and host interactions. We offer a comprehensive range of viral proteins and peptides to support research and development efforts aimed at understanding viral mechanisms and advancing antiviral therapeutics.