Inhibition of coxsackie B virus infection by soluble forms of its receptors: binding affinities, altered particle formation, and competition with cellular receptors.
We previously reported that soluble decay-accelerating factor (DAF) and coxsackievirus-adenovirus receptor (CAR) blocked coxsackievirus B3 (CVB3) myocarditis in mice, but only soluble CAR blocked CVB3-mediated pancreatitis. Here, we report that the in vitro mechanisms of viral inhibition by these soluble receptors also differ. Soluble DAF inhibited virus infection through the formation of reversible complexes with CVB3, while binding of soluble CAR to CVB induced the formation of altered (A) particles with a resultant irreversible loss of infectivity. A-particle formation was characterized by loss of VP4 from the virions and required incubation of CVB3-CAR complexes at 37 degrees C. Dimeric soluble DAF (DAF-Fc) was found to be 125-fold-more effective at inhibiting CVB3 than monomeric DAF, which corresponded to a 100-fold increase in binding affinity as determined by surface plasmon resonance analysis. Soluble CAR and soluble dimeric CAR (CAR-Fc) bound to CVB3 with 5,000- and 10,000-fold-higher affinities than the equivalent forms of DAF. While DAF-Fc was 125-fold-more effective at inhibiting virus than monomeric DAF, complement regulation by DAF-Fc was decreased 4 fold. Therefore, while the virus binding was a cooperative event, complement regulation was hindered by the molecular orientation of DAF-Fc, indicating that the regions responsible for complement regulation and virus binding do not completely overlap. Relative contributions of CVB binding affinity, receptor binding footprint on the virus capsid, and induction of capsid conformation alterations for the ability of cellular DAF and CAR to act as receptors are discussed.
Goodfellow
Ian G
IG
School of Animal and Microbial Sciences, University of Reading, United Kingdom.
Evans
David J
DJ
Blom
Anna M
AM
Kerrigan
Dave
D
Miners
J Scott
JS
Morgan
B Paul
BP
Spiller
O Brad
OB
D000818:Animals; D001667:Binding, Competitive; D018958:CD55 Antigens / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D002460:Cell Line; D062727:Coxsackie and Adenovirus Receptor-Like Membrane Protein; D003384:Coxsackievirus Infections / Q000503:physiopathology / Q000517:prevention & control* / Q000821:virology; D019281:Dimerization; D029822:Enterovirus B, Human / Q000472:pathogenicity* / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D066298:In Vitro Techniques; D011991:Receptors, Virus / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012995:Solubility; D013552:Swine
D018958:CD55 Antigens; C568771:CLMP protein, human; C568772:CLMP protein, mouse; D062727:Coxsackie and Adenovirus Receptor-Like Membrane Protein; D011991:Receptors, Virus; D011994:Recombinant Proteins