Search

Mumps virus (MuV) outbreaks occur in the United States despite high coverage with measles, mumps, rubella (MMR) vaccine. Routine genotyping of laboratory-confirmed mumps cases has been practiced in the United States since 2006 to enhance mumps surveillance. This study reports the detection of unusual mutations in the small hydrophobic (SH) protein of contemporary laboratory-confirmed mumps cases and is the first to describe the impact of such mutations on SH protein function. These mutations are predicted to profoundly alter the amino acid sequence of the SH protein, which has been shown to antagonize host innate immune responses; however, they were neither associated with defects in virus replication nor attenuated protein function in vitro, consistent with detection in clinical specimens. A better understanding of the forces governing mumps virus sequence diversity and of the functional consequences of mutations in viral proteins is important for maintaining robust capacity for mumps detection and disease control., Between 2015 and 2017, routine molecular surveillance in the United States detected multiple mumps viruses (MuVs) with mutations in the small hydrophobic (SH) gene compared to a reference virus of the same genotype. These mutations include an unusual pattern of uracil-to-cytosine hypermutations and other mutations resulting in the generation of premature stop codons or disruption of the canonical stop codon. The mumps virus SH protein may serve as a virulence factor, based on evidence that it inhibits apoptosis and innate immune signaling in vitro and that recombinant viruses that do not express the SH protein are attenuated in an animal model. In this study, mumps viruses bearing variant SH sequences were isolated from contemporary outbreak samples to evaluate the impact of the observed mutations on SH protein function. All isolates with variant SH sequences replicated in interferon-competent cells with no evidence of attenuation. Furthermore, all SH-variant viruses retained the ability to abrogate induction of NF-κB-mediated innate immune signaling in infected cells. Ectopic expression of variant mumps SH genes is consistent with findings from infection experiments, indicating that the observed abrogation of signaling was not mediated by other viral factors that may modulate innate immune signaling. Molecular surveillance is an important public health tool for monitoring the diversity of circulating mumps viruses and can provide insights into determinants of disease. These findings, in turn, will inform studies employing reverse genetics to elucidate the specific mechanisms of MuV pathogenesis and potential impacts of observed sequence variants on infectivity, fitness, and virulence. IMPORTANCE Mumps virus (MuV) outbreaks occur in the United States despite high coverage with measles, mumps, rubella (MMR) vaccine. Routine genotyping of laboratory-confirmed mumps cases has been practiced in the United States since 2006 to enhance mumps surveillance. This study reports the detection of unusual mutations in the small hydrophobic (SH) protein of contemporary laboratory-confirmed mumps cases and is the first to describe the impact of such mutations on SH protein function. These mutations are predicted to profoundly alter the amino acid sequence of the SH protein, which has been shown to antagonize host innate immune responses; however, they were neither associated with defects in virus replication nor attenuated protein function in vitro, consistent with detection in clinical specimens. A better understanding of the forces governing mumps virus sequence diversity and of the functional consequences of mutations in viral proteins is important for maintaining robust capacity for mumps detection and disease control.

Public Health Laboratories (PHLs) in Puerto Rico did not escape the devastation caused by Hurricane Maria. We implemented a quality management system (QMS) approach to systematically reestablish laboratory testing, after evaluating structural and functional damage. PHLs were inoperable immediately after the storm. Our QMS-based approach began in October 2017, ended in May 2018, and resulted in the reestablishment of 92% of baseline laboratory testing capacity. Here, we share lessons learned from the historic recovery of the largest United States’ jurisdiction to lose its PHL capacity, and provide broadly applicable tools for other jurisdictions to enhance preparedness for public health emergencies., Hurricane Maria hit Puerto Rico in 2017 and resulted in a complete loss of activity of the Public Health Laboratories. Here, the authors discuss the approach taken and tools developed to re-establish activity in these laboratories using a quality management system and the lessons learned in this process.

Hurricane Maria made landfall in Puerto Rico on September 20, 2017, causing major damage to infrastructure and severely limiting access to potable water, electric power, transportation, and communications. Public services that were affected included operations of the Puerto Rico Department of Health (PRDOH), which provides critical laboratory testing and surveillance for diseases and other health hazards. PRDOH requested assistance from CDC for the restoration of laboratory infrastructure, surveillance capacity, and diagnostic testing for selected priority diseases, including influenza, rabies, leptospirosis, salmonellosis, and tuberculosis. PRDOH, CDC, and the Association of Public Health Laboratories (APHL) collaborated to conduct rapid needs assessments and, with assistance from the CDC Foundation, implement a temporary transport system for shipping samples from Puerto Rico to the continental United States for surveillance and diagnostic and confirmatory testing. This report describes the initial laboratory emergency response and engagement efforts among federal, state, and nongovernmental partners to reestablish public health laboratory services severely affected by Hurricane Maria. The implementation of a sample transport system allowed Puerto Rico to reinitiate priority infectious disease surveillance and laboratory testing for patient and public health interventions, while awaiting the rebuilding and reinstatement of PRDOH laboratory services.

The continued detection of zoonotic influenza infections, most notably due to the avian influenza A H5N1 and H7N9 subtypes, underscores the need for pandemic preparedness. Decades of experience with live attenuated influenza vaccines (LAIVs) for the control of seasonal influenza support the safety and effectiveness of this vaccine platform. All LAIV candidates are derived from one of two licensed master donor viruses (MDVs), cold-adapted (ca) A/Ann Arbor/6/60 or ca A/Leningrad/134/17/57. A number of LAIV candidates targeting avian H5 influenza viruses derived with each MDV have been evaluated in humans, but have differed in their infectivity and immunogenicity. To understand these differences, we generated four H5N2 candidate pandemic LAIVs (pLAIVs) derived from either MDV and compared their biological characteristics in vitro and in vivo. We demonstrate that all candidate pLAIVs, regardless of gene constellation and derivation, were comparable with respect to infectivity, immunogenicity, and protection from challenge in the ferret model of influenza. These observations suggest that differences in clinical performance of H5 pLAIVs may be due to factors other than inherent biological properties of the two MDVs.

Vaccination is the most effective strategy for prevention and control of influenza. Timely production and deployment of seasonal influenza vaccines is based on an understanding of the epidemiology of influenza and on global disease and virologic surveillance. Experience with seasonal influenza vaccines guided the initial development of pandemic influenza vaccines. A large investment in pandemic influenza vaccines in the last decade has resulted in much progress and a body of information that can now be applied to refine the established paradigm. Critical and complementary considerations for pandemic influenza vaccines include improved assessment of the pandemic potential of animal influenza viruses, proactive development and deployment of pandemic influenza vaccines, and application of novel platforms and strategies for vaccine production and administration.

The recent outbreak of avian origin H10N7 influenza among seals in northern Europe and two fatal human infections with an avian H10N8 virus in China have demonstrated that H10 viruses can spread between mammals and cause severe disease in humans. To gain insight into the potential for H10 viruses to cross the species barrier and to identify a candidate vaccine strain, we evaluated the in vitro and in vivo properties and antibody response in ferrets to 20 diverse H10 viruses. H10 virus infection of ferrets caused variable weight loss, and all 20 viruses replicated throughout the respiratory tract; however, replication in the lungs was highly variable. In glycan-binding assays, the H10 viruses preferentially bound “avian-like” α2,3-linked sialic acids. Importantly, several isolates also displayed strong binding to long-chain “human-like” α2,6-linked sialic acids and exhibited comparable or elevated neuraminidase activity relative to human H1N1, H2N2, and H3N2 viruses. In hemagglutination inhibition assays, 12 antisera cross-reacted with ≥14 of 20 H10 viruses, and 7 viruses induced neutralizing activity against ≥15 of the 20 viruses. By combining data on weight loss, viral replication, and the cross-reactive antibody response, we identified A/mallard/Portugal/79906/2009 (H10N7) as a suitable virus for vaccine development. Collectively, our findings suggest that H10 viruses may continue to sporadically infect humans and other mammals, underscoring the importance of developing an H10 vaccine for pandemic preparedness. IMPORTANCE Avian origin H10 influenza viruses sporadically infect humans and other mammals; however, little is known about viruses of this subtype. Thus, we characterized the biological properties of 20 H10 viruses in vitro and in ferrets. Infection caused mild to moderate weight loss (5 to 15%), with robust viral replication in the nasal tissues and variable replication in the lung. H10 viruses preferentially bind “avian-like” sialic acids, although several isolates also displayed binding to “human-like” sialic acid receptors. This is consistent with the ability of H10 viruses to cross the species barrier and warrants selection of an H10 vaccine strain. By evaluating the cross-reactive antibody response to the H10 viruses and combining this analysis with viral replication and weight loss findings, we identified A/mallard/Portugal/79906/2009 (H10N7) as a suitable H10 vaccine strain.

The emergence of pandemic GII.4 norovirus (NoV) strains has been proposed to occur due to changes in receptor usage and thereby to lead to immune evasion. To address this hypothesis, we measured the ability of human sera collected between 1979 and 2010 to block glycan binding of four pandemic GII.4 noroviruses isolated in the last 4 decades. In total, 268 sera were investigated for 50% blocking titer (BT 50 ) values of virus-like particles (VLPs) against pig gastric mucin (PGM) using 4 VLPs that represent different GII.4 norovirus variants identified between 1987 and 2012. Pre- and postpandemic sera (sera collected before and after isolation of the reference NoV strain) efficiently prevented binding of VLP strains MD145 (1987), Grimsby (1995), and Houston (2002), but not the Sydney (2012) strain, to PGM. No statistically significant difference in virus-blocking titers was observed between pre- and postpandemic sera. Moreover, paired sera showed that blocking titers of ≥160 were maintained over a 6-year period against MD145, Grimsby, and Houston VLPs. Significantly higher serum blocking titers (geometric mean titer [GMT], 1,704) were found among IgA-deficient individuals than among healthy blood donors (GMT, 90.9) ( P < 0.0001). The observation that prepandemic sera possess robust blocking capacity for viruses identified decades later suggests a common attachment factor, at least until 2002. Our results indicate that serum IgG possesses antibody-blocking capacity and that blocking titers can be maintained for at least 6 years against 3 decades of pandemic GII.4 NoV. IMPORTANCE Human noroviruses (NoVs) are the major cause of acute gastroenteritis worldwide. Histo-blood group antigens (HBGAs) in saliva and gut recognize NoV and are the proposed ligands that facilitate infection. Polymorphisms in HBGA genes, and in particular a nonsense mutation in FUT2 (G428A), result in resistance to global dominating GII.4 NoV. The emergence of new pandemic GII.4 strains occurs at intervals of several years and is proposed to be attributable to epochal evolution, including amino acid changes and immune evasion. However, it remains unclear whether exposure to a previous pandemic strain stimulates immunity to a pandemic strain identified decades later. We found that prepandemic sera possess robust virus-blocking capacity against viruses identified several decades later. We also show that serum lacking IgA antibodies is sufficient to block NoV VLP binding to HBGAs. This is essential, considering that 1 in every 600 Caucasian children is IgA deficient.

A critical event in the life cycle of a virus is its initial attachment to host cells. This involves recognition by the viruses of specific receptors on the cell surface, including glycans. Viruses typically exhibit strain-dependent variations in recognizing specific glycan receptors, a feature that contributes significantly to cell tropism, host specificity, host adaptation and interspecies transmission. Examples include influenza viruses, noroviruses, rotaviruses, and parvoviruses. Both rotaviruses and noroviruses are well known gastroenteric pathogens that are of significant global health concern. While rotaviruses, in the family Reoviridae, are the major causative agents of life-threatening diarrhea in children, noroviruses, which belong to the Caliciviridae family, cause epidemic and sporadic cases of acute gastroenteritis across all age groups. Both exhibit enormous genotypic and serotypic diversity. Consistent with this diversity each exhibits strain-dependent variations in the types of glycans they recognize for cell attachment. This chapter reviews the current status of the structural biology of such strain-dependent glycan specificities in these two families of viruses.

Naturally occurring bovine-human reassortant rotaviruses with a P[11] VP4 genotype exhibit a tropism for neonates. Interaction of the VP8* domain of the spike protein VP4 with sialic acid was thought to be the key mediator for rotavirus infectivity. However, recent studies have indicated a role for nonsialylated glycoconjugates, including histo-blood group antigens (HBGAs), in the infectivity of human rotaviruses. We sought to determine if the bovine rotavirus-derived VP8* of a reassortant neonatal G10P[11] virus interacts with hitherto uncharacterized glycans. In an array screen of >600 glycans, VP8* P[11] showed specific binding to glycans with the Galβ1-4GlcNAc motif, which forms the core structure of type II glycans and is the precursor of H type II HBGA. The specificity of glycan binding was confirmed through hemagglutination assays; GST-VP8* P[11] hemagglutinates type O, A, and B red blood cells as well as pooled umbilical cord blood erythrocytes. Further, G10P[11] infectivity was significantly enhanced by the expression of H type II HBGA in CHO cells. The bovine-origin VP4 was confirmed to be essential for this increased infectivity, using laboratory-derived reassortant viruses generated from sialic acid binding rotavirus SA11-4F and a bovine G10P[11] rotavirus, B223. The binding to a core glycan unit has not been reported for any rotavirus VP4. Core glycan synthesis is constitutive in most cell types, and modification of these glycans is thought to be developmentally regulated. These studies provide the first molecular basis for understanding neonatal rotavirus infections, indicating that glycan modification during neonatal development may mediate the age-restricted infectivity of neonatal viruses.

Human noroviruses (HuNoVs) cause sporadic and epidemic gastroenteritis worldwide. They are classified into two major genogroups (GI and GII), with each genogroup further divided into multiple genotypes. Susceptibility to these viruses is influenced by genetically determined histo-blood group antigen (HBGA) expression. HBGAs function as cell attachment factors by binding to a surface-exposed region in the protruding (P) domain of the capsid protein. Sequence variations in this region that result in differential HBGA binding patterns and antigenicity are suggested to form a basis for strain diversification. Recent studies show that serum antibodies that block HBGA binding correlate with protection against illness. Although genogroup-dependent variation in HBGA binding specificity is structurally well characterized, an understanding of how antibodies block HBGA binding and how genotypic variations affect such blockade is lacking. Our crystallographic studies of the GI.1 P domain in complex with the Fab fragment of a human IgA monoclonal antibody (IgA 5I2) with HBGA blocking activity show that the antibody recognizes a conformational epitope formed by two surface-exposed loop clusters in the P domain. The antibody engulfs the HBGA binding site but does not affect its structural integrity. An unusual feature of the antigen recognition by IgA 5I2 is the predominant involvement of the CDR light chain 1 in contrast to the commonly observed CDR heavy chain 3, providing a unique perspective into antibody diversity in antigen recognition. Identification of the antigenic site in the P domain shows how genotypic variations might allow escape from antibody neutralization and exemplifies the interplay between antigenicity and HBGA specificity in HuNoV evolution.

As with many other viruses, the initial cell attachment of rotaviruses, which are the major causative agent of infantile gastroenteritis, is mediated by interactions with specific cellular glycans. The distally located VP8* domain of the rotavirus spike protein VP4 (ref. 5) mediates such interactions. The existing paradigm is that 'sialidase-sensitive' animal rotavirus strains bind to glycans with terminal sialic acid (Sia), whereas 'sialidase-insensitive' human rotavirus strains bind to glycans with internal Sia such as GM1 (ref. 3). Although the involvement of Sia in the animal strains is firmly supported by crystallographic studies, it is not yet known how VP8* of human rotaviruses interacts with Sia and whether their cell attachment necessarily involves sialoglycans. Here we show that VP8* of a human rotavirus strain specifically recognizes A-type histo-blood group antigen (HBGA) using a glycan array screen comprised of 511 glycans, and that virus infectivity in HT-29 cells is abrogated by anti-A-type antibodies as well as significantly enhanced in Chinese hamster ovary cells genetically modified to express the A-type HBGA, providing a novel paradigm for initial cell attachment of human rotavirus. HBGAs are genetically determined glycoconjugates present in mucosal secretions, epithelia and on red blood cells, and are recognized as susceptibility and cell attachment factors for gastric pathogens like Helicobacter pylori and noroviruses. Our crystallographic studies show that the A-type HBGA binds to the human rotavirus VP8* at the same location as the Sia in the VP8* of animal rotavirus, and suggest how subtle changes within the same structural framework allow for such receptor switching. These results raise the possibility that host susceptibility to specific human rotavirus strains and pathogenesis are influenced by genetically controlled expression of different HBGAs among the world's population.

A hemagglutination inhibition (HAI) assay to assess serum antibody responses following Norwalk virus (NV) infection was developed. HAI activity increased significantly in individuals experimentally infected with NV ( n = 18) and correlated with antibody levels measured in a histo-blood group antigen (HBGA) blocking assay. Prechallenge HAI antibody levels also correlated with protection from the development of gastroenteritis (Mann-Whitney test, P = 0.02). The HAI assay is another assay suitable for the detection of antibody that correlates with protection from Norwalk virus-associated disease.

Strain-dependent variation of glycan recognition during initial cell attachment of viruses is a critical determinant of host specificity, tissue-tropism and zoonosis. Rotaviruses (RVs), which cause life-threatening gastroenteritis in infants and children, display significant genotype-dependent variations in glycan recognition resulting from sequence alterations in the VP8* domain of the spike protein VP4. The structural basis of this genotype-dependent glycan specificity, particularly in human RVs, remains poorly understood. Here, from crystallographic studies, we show how genotypic variations configure a novel binding site in the VP8* of a neonate-specific bovine-human reassortant to uniquely recognize either type I or type II precursor glycans, and to restrict type II glycan binding in the bovine counterpart. Such a distinct glycan-binding site that allows differential recognition of the precursor glycans, which are developmentally regulated in the neonate gut and abundant in bovine and human milk provides a basis for age-restricted tropism and zoonotic transmission of G10P[11] rotaviruses., Rotaviruses cause life-threatening gastroenteritis in children and have been shown to have variations in glycan recognition from genetic alterations. Here, the authors use X-ray crystallography to indicate that these alterations can change the specificity of the virus from cows to infant humans.

Noroviruses (NoVs) commonly cause acute gastroenteritis outbreaks. Broadly reactive diagnostic assays are essential for rapid detection of NoV infections. We previously generated a panel of broadly reactive monoclonal antibodies (MAbs). We characterized MAb reactivities by use of virus-like particles (VLPs) from 16 different NoV genotypes (6 from genogroup I [GI], 9 from GII, and 1 from GIV) coating a microtiter plate (direct enzyme-linked immunosorbent assay [ELISA]) and by Western blotting. MAbs were genotype specific or recognized multiple genotypes within a genogroup and between genogroups. We next applied surface plasmon resonance (SPR) analysis to measure MAb dissociation constants (Kd) as a surrogate for binding affinity; aKdlevel of Kdcould not be measured by SPR analysis also failed to capture the NoV VLPs; in contrast, those with a measurableKdgave a positive signal in the capture ELISA. Thus, some broadly cross-reactive epitopes in the VP1 protruding domain may be partially masked on intact particles. One MAb, NV23, was able to detect genogroup I, II, and IV VLPs from 16 genotypes tested by sandwich ELISA, and it successfully detected NoVs in stool samples positive by real-time reverse transcription-PCR when the threshold cycle (CT) value was