Antigenic Sites on the Receptor-Binding Domain of Human Adenovirus Type 2 Fiber

Abstract

The trimeric fiber of adenovirus type 2 (Ad2) mediates the first stage of virus-cell attachment, and the distal head region of the fiber has been implicated as the receptor-binding domain. To locate regions on the primary polypeptide sequence of the fiber which may be involved in virus-cell interaction, peptide-based epitope mapping was performed using (1) polyclonal antibodies prepared against both native Ad2 fiber and Ad2 head protein expressed in Escherichia coli and (2) 18 monoclonal antibodies prepared against trimeric Ad2 head protein expressed in baculovirus. The approach using polyclonal antibodies revealed eight domains on the primary sequence of the head which contain one or more continuous epitopes. At least two of these regions were also recognized by monoclonal antibodies reacting against both monomeric and trimeric fiber head protein. The majority of monoclonal antibodies which did not recognize Ad2 head-specific peptides in ELISA were also nonreactive against the monomeric form of protein in Western blot, suggesting that their recognition of trimer is due to the existence of as yet undefined discontinuous epitopes or to alterations in monomer configuration. Our results correspond well with the recently published X-ray crystallographic model of Ad5 fiber head (D. Xia, L.J. Henry, R.D. Gerard, and J. Deisenhofer, Structure 2, 1259-1270, 1994), since most antigenic determinants containing linear epitopes mapped to the outer loops or uppermost beta-sheets in this structure. Four of five neutralizing monoclonal antibodies recognized trimer only and none recognized linear peptides. This might suggest that the trimeric form of fiber is necessary for making contact with the receptor(s) and that discontinuous epitopes on the head domain may be involved in fiber-cell interaction.

Mechanistic Aspects of Adenovirus Serotype 2 Inactivation with Free Chlorine

“…However, significant differences between adenovirus viability (N/N 0 ) and fiber protein integrity (F/F 0 ) were observed at each pH (Table 3). These results indicate that the region of the fiber knob responsible for binding to the antifiber antibody, which is critical for binding CAR (6), is relatively stable during free chlorine exposures that result in adenovirus inactivation.…”

Neutralizing Antibody Blocks Adenovirus Infection by Arresting Microtubule-Dependent Cytoplasmic Transport

“…Using several approaches, it has been shown convincingly that hexon is the major target for neutralization (8,14,28,34,45). Antifiber and anti-penton base NAbs that block primary receptor interactions and integrin-mediated internalization, respectively, have been identified (7,13,19,32,45); however, they likely represent only a small portion of the neutralizing activity of serum. Studies of the mechanisms of antiHAdV NAbs have identified modes of action that are common to antibody neutralization of other viruses.…”

Detection of Antibodies against Adenovirus Protein IX, Fiber, and Hexon in Human Sera by Immunoblot Assay

“…Neutralizing antibody responses to adenoviruses are directed against components of the virion surface, primarily against fiber, penton base, and hexon (35). Neutralizing antibodies against fiber are qualified to block binding of the fiber knob to its cellular attachment receptor and to aggregate virions by cross-linking fibers on separate virus particles (14). Neutralizing antibodies against penton bases are mainly directed against the integrin-binding RGD motif and prevent virus internalization (18).…”