Wild-Type Human Adenovirus (Serotype 29)

Human adenovirus (HAdV) is a non-enveloped, double-stranded, linear DNA virus that commonly infects the respiratory tract, gastrointestinal tract, urinary tract, and conjunctiva, causing disease in these areas. Rare clinical manifestations include hemorrhagic cystitis, hemorrhagic enteritis, hepatitis, nephritis, pancreatitis, and encephalitis, and it can cause worldwide outbreaks. During large-scale epidemics, the mortality rate is high. Because infants and young children have underdeveloped immune systems and lack corresponding humoral and cellular immunity, they are the most susceptible population for HAdV infection.

HAdV virus particles have a spherical structure and are non-enveloped. The capsid contains the viral core, composed of naked double-stranded linear DNA and core proteins. The capsid consists of 252 capsomeres, exhibiting an icosahedral symmetry structure. Each face of the icosahedron is composed of 12 repeating copies of pseudo-hexagonal trimer hexagonal units, and the 12 vertices are formed by pentamer oligomers. Each oligomer contains one or more copies of non-covalently bound trimeric filaments. Each oligomer consists of four loops (loops 1-4), with the base of the oligomer containing P1 and P2 portions. Fibrous projections are linear projections extending from the capsid surface to the base of each pentamer, approximately 8.5–76.5 nm in length, including head regions and stalk structures. Their length depends on the number of β-helical repeats on the axis and the ADV type. The length and shape of the fibers, as well as sequence variations in the hypervariable regions of the three major capsid proteins, at least partially determine the entry pathways and immunological characteristics of different serotypes.