Species B adenovirus serotypes 3, 7, 11 and 35 share similar binding sites on the membrane cofactor protein CD46 receptor

Abstract

We recently characterized the domains of the human cofactor protein CD46 involved in binding species B2 adenovirus (Ad) serotype 35. Here, the CD46 binding determinants are mapped for the species B1 Ad serotypes 3 and 7 and for the species B2 Ad11. Ad3, 7 and 11 bound and transduced CD46-positive rodent BHK cells at levels similar to Ad35. By using antibody-blocking experiments, hybrid CD46-CD4 receptor constructs and CD46 single point mutants, it is shown that Ad3, 7 and 11 share many of the Ad35-binding features on CD46. Both CD46 short consensus repeat domains SCR I and SCR II were necessary and sufficient for optimal binding and transgene expression, provided that they were positioned at an appropriate distance from the cell membrane. Similar to Ad35, most of the putative binding residues of Ad3, 7 and 11 were located on the same glycan-free, solvent-exposed face of the SCR I or SCR II domains, largely overlapping with the binding surface of the recently solved fiber knob Ad11-SCR I-II three-dimensional structure. Differences between species B1 and B2 Ads were documented with competition experiments based on anti-CD46 antibodies directed against epitopes flanking the putative Ad-binding sites, and with competition experiments based on soluble CD46 protein. It is concluded that the B1 and B2 species of Ad engage CD46 through similar binding surfaces. INTRODUCTIONThe 51 serotypes of human adenoviruses (Ads) are classified into six species, A-F (Benkő et al., 2000;Horwitz, 2001), and species B Ads are divided further into B1 and B2 serotypes, for which tropism differs. The B1 group comprises Ad3, 7, 16, 21 and 50 and predominantly infects the upper respiratory tract, whereas the B2 group serotypes Ad11, 14, 34 and 35 are associated with kidney and urinary-tract infections, with fatal outcome in immunocompromised patients (Leen & Rooney, 2005;Schmitz et al., 1983;Wadell, 2000). Species B Ads bind a different cell-surface receptor from most of the species A, C, D, E and F Ad serotypes, which bind to the coxsackievirus and adenovirus receptor (CAR) (Bergelson et al., 1997;Defer et al., 1990;Roelvink et al., 1998;Stevenson et al., 1995). Several groups have identified the membrane cofactor CD46 as an attachment receptor for species B serotypes, including Ad11 (Segerman et al., 2003b), Ad35 (Gaggar et al., 2003) and Ad3 (Sirena et al., 2004). CD46 belongs to a family of regulators of complement activation, whose biological role is to prevent complement activation on autologous tissue (Liszewski et al., 1991). Based on virus competition experiments and antibody-mediated blocking of various Ads on human cells, it has been suggested that more than one species B receptor exist (Segerman et al., 2003a;Sirena et al., 2004;Tuve et al., 2006), and it remains controversial whether CD46 functions as attachment receptor for all species B serotypes (Gaggar et al., 2003;Gustafsson et al., 2006;Marttila et al., 2005;Segerman et al., 2003b;Tuve et al., 2006). Additional Ads that bind to CD46 include species D Ad37 and 49 (Lemcke...

An Arginine Switch in the Species B Adenovirus Knob Determines High-Affinity Engagement of Cellular Receptor CD46

“…Ad11 uses CD46 as a high-affinity receptor (36,37,51). It is unclear whether the closely related Ad7 and Ad14 also do so (17,18,20,21,25,44,50). The knobs of all three Ads are highly similar in sequence, indicating that the differences in binding are due to specific amino acid exchanges.…”

“…Moreover, transfection with human CD46 cDNA rendered Chinese hamster ovary cells more permissive to infection by all species B Ads, with the exception of Ad3 and Ad7 (25,50), indicating that most species B Ads use CD46 as a receptor. However, Ad3 and Ad7 were also reported to bind and infect CD46-expressing cells in two recent studies (17,18). Finally, a second receptor (receptor X; species B Ad receptor [sBAR]) is thought to interact with some species B Ads (43,50).…”

“…In order to define the mechanism of CD46 binding by Ads, we performed a structural and functional analysis of three highly similar Ads (25): (i) Ad11, which is known to use CD46 as a high-affinity receptor and for which a crystal structure of the knob in complex with CD46 has been determined; (ii) Ad14, which can bind and infect CD46-expressing cells (25); and (iii) Ad7, which has been reported to bind and infect CD46-expressing cells in one study (17). However, others showed that Ad14 (50) and Ad7 (25,50) do not use CD46 for attachment but rather use the unknown receptor X (50), which shows characteristics similar to those of the species B Ad receptor (43).…”

Development of fiber-substituted adenovirus vectors containing foreign peptides in the adenovirus serotype 35 fiber knob

“…In addition, amino-acid sequences in the HI loop are relatively well conserved among the species B Ads. 45 These studies suggest that the HI loop makes a major contribution to the interaction with CD46 in the fiber knob of species B Ads, indicating that the HI loop would be well exposed to the outside of the fiber knob.…”

Enhanced Gene Delivery to Human Primary Endothelial Cells Using Tropism-Modified Adenovirus Vectors

“…It also bears noting that adenovirus type 16, type 3 and type 35 may also utilize the same receptor, CD46, as they are all subgroup B adenoviruses. [26]. However, in the case of serotype 3, the CD46 receptor was shown to mediate infection but use of an anti-CD46 antibody was unable to inhibit infection [27].…”