Maturation of West Nile Virus Modulates Sensitivity to Antibody-Mediated Neutralization

University of California Irvine, United States of America
PLoS Pathogens (Impact Factor: 7.56). 06/2008; 4(5):e1000060. DOI: 10.1371/journal.ppat.1000060
Source: PubMed


West Nile virions incorporate 180 envelope (E) proteins that orchestrate the process of virus entry and are the primary target of neutralizing antibodies. The E proteins of newly synthesized West Nile virus (WNV) are organized into trimeric spikes composed of pre-membrane (prM) and E protein heterodimers. During egress, immature virions undergo a protease-mediated cleavage of prM that results in a reorganization of E protein into the pseudo-icosahedral arrangement characteristic of mature virions. While cleavage of prM is a required step in the virus life cycle, complete maturation is not required for infectivity and infectious virions may be heterogeneous with respect to the extent of prM cleavage. In this study, we demonstrate that virion maturation impacts the sensitivity of WNV to antibody-mediated neutralization. Complete maturation results in a significant reduction in sensitivity to neutralization by antibodies specific for poorly accessible epitopes that comprise a major component of the human antibody response following WNV infection or vaccination. This reduction in neutralization sensitivity reflects a decrease in the accessibility of epitopes on virions to levels that fall below a threshold required for neutralization. Thus, in addition to a role in facilitating viral entry, changes in E protein arrangement associated with maturation modulate neutralization sensitivity and introduce an additional layer of complexity into humoral immunity against WNV.

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Available from: Christiane Jost, Oct 14, 2015
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    • "Early studies suggested that complete maturation is necessary to render flavivirus particles infectious (Stadler et al., 1997). However, recent studies have demonstrated that not only are virions retaining uncleaved prM infectious (Colpitts et al., 2011; Mukherjee et al., 2011; Nelson et al., 2008; Zybert et al., 2008), but that complete maturation may be detrimental to WNV replication under certain circumstances (Zybert et al., 2008). Whilst most strains of WNV contain a glycosylation site in both E and the precursor portion of prM, some non-pathogenic strains lack the E glycosylation site. "
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    ABSTRACT: The molecular basis for the increased resistance of astrocytes to a nonneuropathogenic strain of WNV, WNV-MAD78, compared to the neuropathogenic strain WNV-NY remains unclear. In this report, we demonstrate that the reduced susceptibility of astrocytes to WNV-MAD78 is due to a combination of both cellular activities as well as viral determinants. Analyses of the viral particle indicated that astrocyte-derived WNV-MAD78 particles are less infectious than those of WNV-NY. Additionally, inhibition of cellular furin-like proteases increased WNV-MAD78 infectious particle production in astrocytes, suggesting that high levels of furin-like protease activity within these cells acts in a cell- and strain-specific manner to inhibit WNV-MAD78 replication. Moreover, analysis of recombinant viruses indicated that the structural proteins of WNV-MAD78 were responsible for decreased particle infectivity and the corresponding reduction in infectious particle production compared to WNV-NY. Thus, the composition of the WNV virion is also a major determinant for viral fitness within astrocytes and may contribute to WNV propagation within the CNS. Whether the WNV-MAD78 structural genes reduce virus replication and particle infectivity through the same mechanism as the cellular furin-like protease activity, or whether these two determinants function through distinct pathways, remains to be determined.
    Journal of General Virology 06/2014; 95(Pt 9). DOI:10.1099/vir.0.065474-0 · 3.18 Impact Factor
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    • "Previous studies have demonstrated that mature particles and partially mature particles were infectious whereas immature particles were virtually non-infectious [24,27,42,56]. The maturation state of virus particles can influence the neutralizing and enhancing capacity of antibodies direct against DENV surface proteins [24,27,63]. We detected the specific infectivity of the LoVo-released virus particles and found that the infectious properties of imDENV2 was 10,000-fold lower compared to that of C6/36-cultured standard virus preparations. "
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    ABSTRACT: Dengue virus (DENV) infection is the most important arthropod- borne viral disease in human, but antiviral therapy and approved vaccines remain unavailable due to antibody-dependent enhancement (ADE) phenomenon. Many studies showed that pre-membrane (prM)-specific antibodies do not efficiently neutralize DENV infection but potently promote ADE infection. However, most of the binding epitopes of these antibodies remain unknown. In the present study, we characterized a DENV cross-reactive monoclonal antibody (mAb), 4D10, that neutralized poorly but potently enhanced infection of four standard DENV serotypes and immature DENV (imDENV) over a broad range of concentration. In addition, the epitope of 4D10 was successfully mapped to amino acid residues 14 to18 of DENV1-4 prM protein using a phage-displayed peptide library and comprehensive bioinformatics analysis. We found that the epitope was DENV serocomplex cross-reactive and showed to be highly immunogenic in Balb/c mice. Furthermore, antibody against epitope peptide PL10, like 4D10, showed broad cross-reactivity and weak neutralizing activtity with four standard DENV serotypes and imDENV but significantly promoted ADE infection. These results suggested 4D10 and anti-PL10 sera were infection-enhancing antibodies and PL10 was infection-enhancing epitope. We mapped the epitope of 4D10 to amino acid residues 14 to18 of DENV1-4 prM and found that this epitope was infection-enhancing. These findings may provide significant implications for future vaccine design and facilitate understanding the pathogenesis of DENV infection.
    BMC Microbiology 08/2013; 13(1):194. DOI:10.1186/1471-2180-13-194 · 2.73 Impact Factor
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    • "This orchestrates profound rearrangements of viral glycoproteins that result in the acquisition of the mature structure of the virion [14], [15], [16]. While this cleavage is a required step in the viral life cycle, it can be inefficient; suggesting that complete maturation is not required for infectivity [17], [18]. Indeed, the presence of flaviviral ‘mosaic’ particles combining regions of mature and immature structure has been documented [19], and the degree of maturation of flavivirus particles has been related to different aspects of their interaction with antibodies [18], [20], [21], [22]. "
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    ABSTRACT: West Nile virus (WNV) is a worldwide distributed mosquito-borne flavivirus that naturally cycles between birds and mosquitoes, although it can infect multiple vertebrate hosts including horses and humans. This virus is responsible for recurrent epidemics of febrile illness and encephalitis, and has recently become a global concern. WNV requires to transit through intracellular acidic compartments at two different steps to complete its infectious cycle. These include fusion between the viral envelope and the membrane of endosomes during viral entry, and virus maturation in the trans-Golgi network. In this study, we followed a genetic approach to study the connections between viral components and acidic pH. A WNV mutant with increased resistance to the acidotropic compound NH4Cl, which blocks organelle acidification and inhibits WNV infection, was selected. Nucleotide sequencing revealed that this mutant displayed a single amino acid substitution (Lys 3 to Glu) on the highly basic internal capsid or core (C) protein. The functional role of this replacement was confirmed by its introduction into a WNV infectious clone. This single amino acid substitution also increased resistance to other acidification inhibitor (concanamycin A) and induced a reduction of the neurovirulence in mice. Interestingly, a naturally occurring accompanying mutation found on prM protein abolished the resistant phenotype, supporting the idea of a genetic crosstalk between the internal C protein and the external glycoproteins of the virion. The findings here reported unveil a non-previously assessed connection between the C viral protein and the acidic pH necessary for entry and proper exit of flaviviruses.
    PLoS ONE 07/2013; 8(7):e69479. DOI:10.1371/journal.pone.0069479 · 3.23 Impact Factor
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