Genetic and antigenic diversity among noroviruses

Biertumpfel

Georgiev

et al. 2011

J Virol

Self Cite

119

156

Noroviruses are the dominant cause of outbreaks of gastroenteritis worldwide, and interactions with human histo-blood group antigens (HBGAs) are thought to play a critical role in their entry mechanism. Structures of noroviruses from genogroups GI and GII in complex with HBGAs, however, reveal different modes of interaction. To gain insight into norovirus recognition of HBGAs, we determined crystal structures of norovirus protruding domains from two rarely detected GII genotypes, GII.10 and GII.12, alone and in complex with a panel of HBGAs, and analyzed structure-function implications related to conservation of the HBGA binding pocket. The GII.10-and GII.12-apo structures as well as the previously solved GII.4-apo structure resembled each other more closely than the GI.1-derived structure, and all three GII structures showed similar modes of HBGA recognition. The primary GII norovirus-HBGA interaction involved six hydrogen bonds between a terminal ␣fucose1-2 of the HBGAs and a dimeric capsid interface, which was composed of elements from two protruding subdomains. Norovirus interactions with other saccharide units of the HBGAs were variable and involved fewer hydrogen bonds. Sequence analysis revealed a site of GII norovirus sequence conservation to reside under the critical ␣fucose1-2 and to be one of the few patches of conserved residues on the outer virion-capsid surface. The site was smaller than that involved in full HBGA recognition, a consequence of variable recognition of peripheral saccharides. Despite this evasion tactic, the HBGA site of viral vulnerability may provide a viable target for small molecule-and antibody-mediated neutralization of GII norovirus.

Section: Methodsmentioning

confidence: 99%

Crystal Structures of GII.10 and GII.12 Norovirus Protruding Domains in Complex with Histo-Blood Group Antigens Reveal Details for a Potential Site of Vulnerability

Biertumpfel

Georgiev

et al. 2011

J Virol

Self Cite

119

156

“…The norovirus P domains, GI.1 (Norwalk virus, Genbank accession number M87661), GI.11 (Akabane, EF547396), GII.1 (Hawaii, U07611), GII.2 (Snow Mountain, AY134748), GII.4 (Sydney-2012, JX459908 and Saga4 2006, AB447457), GII.10 (Vietnam026, AF504671), GII.12 (Hiro, AB044366), and GII.17 (Kawasaki308, LC037415 were expressed in E.coli, purified and stored in GFB (25mM Tris-HCl pH7.6, 0.3M NaCl) [66]. The full-length capsid genes, GI.1 (AY502016.1), GI.11, GII.1, GII.2, GII.4, GII.10, GII.12, and GII.17, were expressed in insect cells using the baculovirus expression system and stored in PBS [67,68].…”

Section: P Domain Productionmentioning

confidence: 99%

Nanobodies Targeting Norovirus Capsid Reveal Functional Epitopes and Potential Mechanisms of Neutralization

Koromyslova

2018

Biophysical Journal

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Norovirus is the leading cause of gastroenteritis worldwide. Despite recent developments in norovirus propagation in cell culture, these viruses are still challenging to grow routinely. Moreover, little is known on how norovirus infects the host cells, except that histo-blood group antigens (HBGAs) are important binding factors for infection and cell entry. Antibodies that bind at the HBGA pocket and block attachment to HBGAs are believed to neutralize the virus. However, additional neutralization epitopes elsewhere on the capsid likely exist and impeding the intrinsic structural dynamics of the capsid could be equally important. In the current study, we investigated a panel of Nanobodies in order to probe functional epitopes that could trigger capsid rearrangement and/ or interfere with HBGA binding interactions. The precise binding sites of six Nanobodies (Nano-4, Nano-14, Nano-26, Nano-27, Nano-32, and Nano-42) were identified using X-ray crystallography. We showed that these Nanobodies bound on the top, side, and bottom of the norovirus protruding domain. The impact of Nanobody binding on norovirus capsid morphology was analyzed using electron microscopy and dynamic light scattering. We discovered that distinct Nanobody epitopes were associated with varied changes in particle structural integrity and assembly. Interestingly, certain Nanobody-induced capsid morphological changes lead to the capsid protein degradation and viral RNA exposure. Moreover, Nanobodies employed multiple inhibition mechanisms to prevent norovirus attachment to HBGAs, which included steric obstruction (Nano-14), allosteric interference (Nano-32), and violation of normal capsid morphology (Nano-26 and Nano-85). Finally, we showed that two Nanobodies (Nano-26 and Nano-85) not only compromised capsid integrity and inhibited VLPs attachment to HBGAs, but also recognized a broad panel of norovirus genotypes with high affinities. Consequently, Nano-26 and Nano-85 have a great potential to function as novel therapeutic agents against human noroviruses. PLOS Author summaryWe determined the binding sites of six novel human norovirus specific Nanobodies (Nano-4, Nano-14, Nano-26, Nano-27, Nano-32, and Nano-42) using X-ray crystallography. The unique Nanobody recognition epitopes were correlated with their potential neutralizing capacities. We showed that one Nanobody (Nano-26) bound numerous genogroup II genotypes and interacted with highly conserved capsid residues. Four Nanobodies (Nano-4, Nano-26, Nano-27, and Nano-42) bound to occluded regions on the intact particles and impaired normal capsid morphology and particle integrity. One Nanobody (Nano-14) bound contiguous to the HBGA pocket and interacted with several residues involved in binding HBGAs. We found that the Nanobodies delivered multiple inhibition mechanisms, which included steric obstruction, allosteric interference, and disruption of the capsid stability. Our data suggested that the HBGA pocket might not be an ideal target for drug development, since the surrounding regio...

“…One study showed that individuals expressing the O type (H antigen) had higher infection rates than individuals expressing other blood types, while those with the B type were resistant to infections (5). Human noroviruses are genetically and antigenetically distinct (1). There are two main genogroups (GI and GII), and those can be further subdivided into numerous genotypes.…”

Section: Human Norovirus and Histo-blood Group Antigensmentioning

confidence: 99%

Human Norovirus Interactions with Histo-Blood Group Antigens and Human Milk Oligosaccharides

Schroten

Hanisch

2016

J Virol

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Human noroviruses interact with both human histo-blood group antigens (HBGAs) and human milk oligosaccharides (HMOs). The former are believed to be important for a virus infection, while the latter might act as natural decoys in the host during an infection. However, certain noroviruses are known to bind poorly to HBGAs and yet still cause infections; some interact with numerous HBGA types but are nonprevalent; and yet others bind HBGAs and seem to be increasing in prevalence. HBGAs and HMOs can be found as soluble antigens in humans, can be structurally alike, and can interact with equivalent residues at identical binding pockets on the capsid. In this Gem, we discuss HBGA and HMO binding studies for human noroviruses, concentrating on the clinically important genogroup II noroviruses. In short, the roles of HBGA and HMO interactions in norovirus infections are still unclear. Human noroviruses are the dominant cause of outbreaks of acute gastroenteritis. These viruses are also responsible for significant numbers of sporadic infections, are often found in asymptomatic cases, can cause chronic infections, and infect all age groups. Noroviruses are transmitted via the fecal-oral route, and infections often result from consumption of contaminated foods such as bivalves (clams and oysters). Noroviruses have a single-stranded, positive-sense RNA genome of ϳ7.5 kb. The genome contains three open reading frames (ORFs): ORF1 encodes nonstructural proteins, ORF2 encodes a capsid protein (VP1), and ORF3 encodes a minor capsid protein. Human norovirus is difficult to grow in cell cultures, and the exact locations of the cells and the cell type(s) that norovirus infect remain unknown. Expression of the capsid protein in insect cells can generate selfassembled virus-like particles (VLPs) that are morphologically and antigenically similar to the native virion (1). The norovirus particle is composed of 180 copies of VP1, which forms 90 VP1 homodimers. The X-ray crystal structure of norovirus VLPs identified two main domains, the shell (S) domain and the protruding (P) domain (2). The S domain surrounds the viral RNA, whereas the P domain is further subdivided into P1 and P2 subdomains and contains determinants for cell attachment and antigenicity. HUMAN NOROVIRUS AND HISTO-BLOOD GROUP ANTIGENSHuman noroviruses are known to interact with histo-blood group antigens (HBGAs), and this interaction could be important for infection (3-7). HBGAs can be found as soluble antigens in saliva and are expressed on the mucosal epithelium of the digestive tract. Therefore, noroviruses could interact several times with HBGAs during the course of an infection. Interestingly, human noroviruses can naturally bioaccumulate in bivalves, where they are thought to bind HBGA-like carbohydrates in the gastrointestinal epithelial cells (8). However, this accumulation does not appear to cause harm to the bivalves.Multiple gene families control human HBGA biosynthesis through the action of glycosyltransferases (9). As HBGAs can be either lipid or protein ...