The aim of this study was to determine the role of the human neonatal receptor for the Fc fragment of IgG (hFcRn) as a common uncoating cellular receptor for echoviruses and coxsackievirus A9 during infection of human rhabdomyosarcoma (RD) cells. Material and methods. The protective effect of the human serum albumin, purified from globulins, (HSA-GF) and antibodies to hFcRn was studied in RD cells infected with several strains and clones of species B enteroviruses possessing different receptor specificity (echoviruses 3, 9, 11, 30 and coxsackieviruses A9, B4, B5). Results. It was shown that HSA-GF at concentrations of 4% or less protected RD cells from infection with echoviruses 3, 9, 11 and coxsackievirus A9. The antibodies to hFcRn at concentrations of 2.5 ug/mL or less demonstrated the similar spectrum of protective activity in RD cells against infection with echoviruses 3, 9, 11, 30 and coxsackievirus A9. The protective effect of HSA-GF or the antibodies to hFcRn was not observed in RD cells infected with coxsackieviruses B4 and B5 that need coxsackievirus-adenovirus receptor for uncoating. Discussion. The usage of the previously characterized echovirus 11 clonal variants with different receptor specificity allowed us to define the function of hFcRn as a canyon-binding uncoating receptor in RD cells. The kinetics and magnitude of the observed protective effects correlated with receptor specificity of the enteroviruses used in this work supporting the two-step interaction of DAF-dependent echoviruses with the cellular receptors. Conclusions. In this study, the function of hFcRn was defined in RD cells as a canyon-binding and uncoating receptor for echoviruses and coxsackievirus A9. The two-step interaction of DAF-dependent echoviruses during entry into the cells was confirmed: initially with the binding receptor DAF and subsequently with the uncoating receptor hFcRn.

Экспериментально установлено влияние роданина на форму графика инфекционной активности в одиночном цикле репродукции эховируса 11 серотипа в культуре клеток RD. Выявлено более выраженное ингибирующее действие роданина на процесс депротеинизации гемагглютинирующего клона эховируса 11 по сравнению с негемагглютинирующим клоном. Представлена динамическая модель ин- терпретации графиков одиночного цикла репродукции эховирусов, позволяющая проводить сравни- тельный анализ задержки интернализации, интенсивности депротеинизации и эффективности синтеза новых вирионов.

Decay accelerating factor (DAF. CD55) is used by OAF-dependent (Daf+) variants of echovirus 11 (EV11) as a primary cellular receptor. The interaction of EV11 with DAF is completely reversible, therefore DAF-dependent variants require an unidentified coreceptor to initiate uncoating. Daf- variants of EV11, which do not interact with DAF, use an alternative primary cellular receptor. The aim of this study was to test the hypothesis whether the coreceptor, which is necessary for the uncoating of DAF-dependent variants, may act as an alternative primary receptor for the Daf- variants of EV11. By using the model of the two closely related daf+ and daf- clones of EV11 in rhabdomyosarcoma (RD) cell line, it was shown that a single amino acid substitution in the capsid protein VP2 could control the expression of the DAF-dependent phenotype. Anti-DAF monoclonal antibody has blocked the infection of RD cells by the OAF-dependent daf+ clone, but not by the daf- clone of EV11. Since the structural proteins of the two clones differed only in the receptor binding site for DAF, the unidentified non-DAF primary receptor for the daf- clone might have the same conformation as the uncoating coreceptor required for the daf+ clone. Despite the difference in primary receptors, both daf+ and daf- clones were equally inhibited by a monoclonal antibody to beta2-microglobulin. The monoclonal antibody B9.12.1 to class I human leukocyte antigen molecules showed no inhibitory effect in regards to either clone. The hypothesis of convergent intracellular traffic of Daf+ and Daf- variants of EV11 is discussed. (C) 2012 Elsevier B.V. All rights reserved.

In this study we present the comparative sequence analysis of the parental haemagglutinating (daf+) and mutant non-haemagglutinating (daf-) clones of echovirus 11 (EV11) isolated from the prototype strain Gregory. The sequence comparison revealed only a single amino acid substitution in the capsid protein VP2 of each mutant clone. These substitutions were located in the area of viral receptor-binding site for DAF. Since daf- mutants of EV11 did not interact with DAF, they used an alternative receptor for the cell entry. To elucidate the nature of the alternative receptor we used subvariant clones of EV11 adapted to human rhabdomyosarcoma (RD), human carcinoma (HEp-2) and African Green monkey kidney (BGM) cell lines. The usage of the subvariant clones with altered host range and the cell cultures of human and simian origin allowed us to map the amino acid substitutions associated with the adaptation of EV11 to the alternative cellular receptors. These amino acid substitutions were located on the surface of the virion in the canyon area. Hence the virus canyon may serve as the receptor-binding site for the alternative (in respect to DAF) cellular receptor(s).

The review presents the currently available data on the receptor specificity of enteroviruses. It discusses whether changes in the receptor specificity of enteroviruses may play a role in their in vitro and in vivo reproduction.

The aim of this paper was to construct the mathematical model of the kinetics of nonhemagglutinating mutant accumulation in the cloned population of hemagglutinating echovirus 11 and to verify the model adequacy by comparing the results of biological and numerical experiments.

The frequency of nonhemagglutinating (h-) mutants was determined in hemagglutinating (HA) clones of echovirus 11. The HA clones were derived from the prototype strain Gregory and a clinical isolate of echovirus 11. The h- mutants were found at a constant frequency of 3.0 x 10(-5) (mean value) in the HA clones derived from both strains. Since the conditions of the population equilibrium of HA clones and neutrality of the mutation were satisfied, it was proposed that the observed frequency of h- mutants occurred as a result of a point mutation. The frequency of h+ revertants at the second passage of h- mutant clone was 9.1 x 10(-5). Hence the frequency of reversion suggests that the number of potential sites of back mutation was restricted.