A single M protein mutation affects the acid inactivation threshold and growth kinetics of a chimeric flavivirus

Maier, Caroline C.; Delagrave, Simon; Zhang, Zhenxi; Brown, Nathan; Monath, Thomas P.; Пугачев, К. В.; Guirakhoo, Farshad

doi:10.1016/j.virol.2007.01.008

Cited by 15 publications

(8 citation statements)

References 37 publications

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“…In this study, we have isolated and characterized a WNV mutant with increased resistance to the acidotropic agent NH 4 Cl. In contrast to other previously described flaviviruses with altered pH requirements, which exhibited mutations on the proteins that conform the external shell of the virion (E and M) -[34] and references therein-, the WNV mutant here reported displayed a single amino acid substitution on the internal core protein. This amino acid substitution also increased resistance to other acidification inhibitor and induced a reduction of the neurovirulence in mice.…”

Section: Introductioncontrasting

confidence: 91%

A Single Amino Acid Substitution in the Core Protein of West Nile Virus Increases Resistance to Acidotropic Compounds

et al. 2013

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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.

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Section: Introductioncontrasting

confidence: 91%

A Single Amino Acid Substitution in the Core Protein of West Nile Virus Increases Resistance to Acidotropic Compounds

et al. 2013

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“…This suggestion is supported by multiple existing studies. The K115E (of prM, or the 26 th amino acid of M) mutation lies adjacent to a region of M that modulates E protein function during early steps of infection such as membrane fusion (Maier, Delagrave et al, 2007). Additional structural studies of the M and E proteins suggest that the first approximately 20 residues of the M protein interact with the ij loop in domain II (dimerization and fusion domain) of E (Zhang, Chipman et al, 2003).…”

Section: Discussionmentioning

confidence: 99%

Identification of genetic determinants of a tick-borne flavivirus associated with host-specific adaptation and pathogenicity

et al. 2008

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Tick-borne flaviviruses are maintained in nature in an enzootic cycle involving a tick vector and a vertebrate host. Thus, the virus replicates in two disparate hosts, each providing selective pressures that can influence virus replication and pathogenicity. To identify viral determinants associated with replication in the individual hosts, plaque purified Langat virus (TP21pp) was adapted to growth in mouse or tick cell lines to generate two virus variants, MNBp20 and ISEp20, respectively. Virus adaptation to mouse cells resulted in four amino acid changes in MNBp20 relative to TP21pp, occurring in E, NS4A and NS4B. A comparison between TP21pp and ISEp20 revealed three amino acid modifications in M, NS3 and NS4A of ISEp20. ISEp20, but not MNBp20, was attenuated following intraperitoneal inoculation of mice. Following isolation from mice brains, additional mutations reproducibly emerged in E and NS3 of ISEp20 that were possibly compensatory for the initial adaptation to tick cells. Thus, our data implicate a role for E, M, NS3, NS4A and NS4B in host adaptation and pathogenicity of tick-borne flaviviruses.

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“…According to this, WNV populations display a variable level of sequence diversity (Ciota et al, 2007;Jerzak et al, 2005) that favours rapid selection of variants in response to selective pressures. Although mutations in the E or M protein that alter pH sensitivity have been described for other flaviviruses (summarized by Maier et al, 2007), this kind of mutant has not been reported for WNV. To gain information on the molecular aspects of the conformational rearrangements of WNV virions following acid exposure, a WNV variant with increased resistance to acidinduced inactivation was isolated and characterized.…”

Section: Introductionmentioning

confidence: 98%

A West Nile virus mutant with increased resistance to acid-induced inactivation

Martín-Acebes

Saiz

2011

Journal of General Virology

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West Nile virus (WNV) is a mosquito-borne flavivirus responsible for epidemics of febrile illness, meningitis, encephalitis and flaccid paralysis. WNV gains entry into host cells through endocytosis. The acid pH inside endosomes triggers rapid conformational rearrangements of the flavivirus envelope (E) glycoprotein that result in fusion of the endosomal membrane with the virion envelope. Conformational rearrangements of the E glycoprotein can be induced by acid exposure in solution in the absence of target membranes, thus causing a loss of infectivity. Following a genetic approach to study this process, a WNV mutant with increased resistance to acid-induced inactivation was isolated and its complete genome was sequenced. A single amino acid substitution, T70I, in the E glycoprotein was found to be responsible for the increased acid resistance, which was linked to an increase in the sensitivity of infection to the chemical rise of endosomal pH, suggesting that the mutant required a more acid pH inside the endosomes for fusion. No alterations in viral infection kinetics, plaque size or induced mortality rates in mice of the mutant were noted. However, by means of virus competition assays, a reduction in viral fitness under standard culture conditions was observed for the mutant. These results provide new evidence of the adaptive flexibility to environmental factors -pH variation in this case -of WNV populations. Implications of the T70I replacement on the E glycoprotein structure-function relationship are discussed. INTRODUCTIONWest Nile virus (WNV) is a mosquito-borne flavivirus that cycles between several species of mosquitoes and birds, and also infects a broad range of vertebrates, including humans (Hayes et al., 2005a). After its first description in Uganda in 1937(Smithburn et al., 1940, WNV has been associated with sporadic outbreaks of meningoencephalitis in Africa and the Middle East until 1999, when the virus emerged in the USA causing thousands of infections among humans, horses and birds (Lanciotti et al., 1999). Although WNV infections in humans are mainly subclinical, clinically apparent infections range from a febrile illness (West Nile fever) to a neuroinvasive disease associated with high mortality (DeBiasi & Tyler, 2006; Hayes et al., 2005b). Despite great effort having been invested in understanding the molecular aspects of WNV infection, currently there is no vaccine or specific therapy approved for use in humans (Diamond, 2009).The WNV genome comprises a single-stranded, positivesense RNA molecule (approx. 11 000 nt) that encodes three structural proteins -the capsid (C), pre-membrane/ membrane (prM/M) and envelope (E) proteins -and seven non-structural proteins, generated by cleavage of a single polyprotein (Brinton, 2002). The genomic RNA is enclosed within a nucleocapsid composed of multiple copies of the C protein, which constitutes the core of the virion and is enveloped by a lipid bilayer derived from the host cell. Cryoelectron microscopy studies have revealed that mature virions are ...

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A single M protein mutation affects the acid inactivation threshold and growth kinetics of a chimeric flavivirus

Cited by 15 publications

References 37 publications

A Single Amino Acid Substitution in the Core Protein of West Nile Virus Increases Resistance to Acidotropic Compounds

A Single Amino Acid Substitution in the Core Protein of West Nile Virus Increases Resistance to Acidotropic Compounds

Identification of genetic determinants of a tick-borne flavivirus associated with host-specific adaptation and pathogenicity

A West Nile virus mutant with increased resistance to acid-induced inactivation

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