Human CD81 Virus-Like Particles

CD81, also known as tetraspanin-28 (TSPAN28), is a member of the tetraspanin family and plays a key role in processes such as cell adhesion, signaling, and membrane organization. This 26 kDa protein is widely expressed in various tissues, including immune cells, hepatocytes, and neurons. Structurally, CD81 comprises four transmembrane domains, short intracellular N- and C-termini, and two extracellular loops (a small loop and a large loop) that mediate interactions with other proteins and pathogens. CD81 is a known coreceptor for hepatitis C virus (HCV) entry into hepatocytes, binding to the viral envelope glycoprotein E2. In addition to its role in viral infection, CD81 also participates in immune regulation by binding to CD19 and CD21 in the B cell receptor complex, influencing B cell activation.

Human CD81 virus-like particles (VLPs) are non-infectious nanostructures designed to mimic the native conformation of CD81 presenting on membranes or viral particles. These VLPs are typically produced by expressing CD81 along with other structural proteins, such as HCV E2 or HIV Gag, in heterologous systems such as mammalian, insect, or yeast cells. Unlike live viruses, VLPs lack genetic material, making them safe for use in research and therapeutic applications. CD81 VLPs retain the native structure of the protein, including its extracellular loops, making them useful for studying virus-host interactions, particularly HCV entry inhibition. They can serve as valuable tools for vaccine development due to their ability to elicit a strong immune response by presenting CD81 in a realistic three-dimensional format. CD81 VLPs are also used in drug screening to identify inhibitors of viral attachment or fusion.