Localization of neutralization epitopes on adenovirus fiber knob from species C

Abstract

Although potential neutralization epitopes on the fiber knob of adenovirus (AdV) serotype 2 (Ad2) and Ad5 have been revealed, few studies have been carried out to identify neutralization epitopes on the knob from a broader panel of AdV serotypes. In this study, based on sequence and structural analysis of knobs from Ad1, Ad2, Ad5 and Ad6 (all from species C), several trimeric chimeric knob proteins were expressed in Escherichia coli to identify the locations of neutralization epitopes on the knobs by analysing their reactivity with mouse and rabbit polyclonal sera raised against AdVs and human sera with natural AdV infection. The dominant neutralization epitopes were located mainly in the N-terminal part of knobs from Ad1, Ad2 and Ad5, but they seemed to be located in the C-terminal part of the Ad6 knob, with some individual differences in rabbit and human populations. Our study adds to our understanding of humoral immune responses to AdVs and will facilitate the construction of more desirable capsid-modified recombinant Ad5 vectors.

Recombinantly Expressed Chimeric Fibers Demonstrate Discrete Type-Specific Neutralizing Epitopes in the Fowl Aviadenovirus E (FAdV-E) Fiber, Promoting the Optimization of FAdV Fiber Subunit Vaccines towards Cross-Protection in vivo

“…Aside from the structural effects discussed, our data on the immunogenicities of chimeras with reciprocally oriented sequences are similar to those of another study, conducted with HAdV fibers, where the outcome of in vitro reactivities of chimeric knobs varied due to different locations of the dominant neutralization epitope depending on the serotype ( 3 ). Although this hypothesis remains to be investigated for FAdVs, our results would indicate the location of the neutralizing epitope to be anywhere to the right in the FAdV-8a fiber, as opposed to being to the left in the FAdV-8b fiber, relative to the exchange site G441-R442, rendering crecFib-8b/8a the only, but very powerful, antigen attainable by such means.…”

“…Complicating the situation, adenoviral fibers show individual variations within their common morphological framework. This includes the number and type of fibers present on the capsid, but also variations in the surface accessibility of residue sites, with consequences for receptor tropism and immunity ( 3 , 19 ).…”

“…Knowledge about adenoviral antigenicity is predominantly derived from human adenoviruses, from the pioneer work on the major determinants by Norrby ( 1 ) to a range of studies on epitope identification. More recently, such studies have also advanced beyond the immunodominant antigen, hexon, and started to involve novel in silico approaches ( 2 – 4 ). Such information is widely unavailable for adenoviruses outside the genus Mastadenovirus , despite holding clinical applications, not only for certain veterinary areas but also for potential development of new vectorization platforms.…”

Vaccine development for human mastadenovirus

“…The recombinant fiber knob can specifically distinguish antibodies against different HAdV types, indicating that the trimeric knob would be a good candidate antigen for detecting HAdV serotype-specific NAbs in sera from naturally-infected subjects (60,61). Elucidation of the 3D conformation of the hexon protein would be helpful in determining accurate epitopes; however, X-ray crystal diffraction has only been successfully performed on a few hexon structures.…”

Broadly neutralizing monoclonal antibodies against human adenovirus types 55, 14p, 7, and 11 generated with recombinant type 11 fiber knob

“…Previous studies have mapped linear epitopes on the fiber knobs of Ad2, HAdV3, HAdV5, Ad8, and Ad15 with synthetic peptides 38–41 . Lang et al reported that the dominant neutralization epitopes were located primarily in the N-terminal region of knobs from Ad1, Ad2, and HAdV5, but they appeared to be located in the C-terminal region of the Ad6 knob, with some individual differences observed in rabbit and human populations 42 . However, only a few neutralization epitopes on HAdV fiber knob have been identified.…”