Case Series of Jamestown Canyon Virus Infections with Neurologic Outcomes, Canada, 2011-2016

Jamestown Canyon virus (JCV) is a mosquitoborne orthobunyavirus in the California serogroup that circulates throughout Canada and the United States. Most JCV exposures result in asymptomatic infection or a mild febrile illness, but JCV can also cause neurologic diseases, such as meningitis and encephalitis. We describe a case series of confirmed JCV-mediated neuroinvasive disease among persons from the provinces of British Columbia, Alberta, Quebec, and Nova Scotia, Canada, during 2011-2016. We highlight the case definitions, epidemiology, unique features and clinical manifestations, disease seasonality, and outcomes for those cases. Two of the patients (from Quebec and Nova Scotia) might have acquired JCV infections during travel to the northeastern region of the United States. This case series collectively demonstrates JCV's wide distribution and indicates the need for increased awareness of JCV as the underlying cause of meningitis/meningoencephalitis during mosquito season.

Zika virus infection during pregnancy and vertical transmission: case reports and peptide-specific cell-mediated immune responses

Zika virus (ZIKV) infection in pregnant women is associated with birth defects, which are more prevalent and severe the earlier in pregnancy the infection occurs. Pregnant women at risk of possible ZIKV exposure (n = 154) were screened using ELISA for ZIKV IgM and IgG. Nine of 154 (5.84%) pregnant women who underwent screening exhibited positive ZIKV serology. Of these, two maternal infections were confirmed by real-time RT-PCR and five were considered probable, but only three of those were retained for further analysis based on strict diagnostic criteria. Plaque reduction neutralization tests (PRNT) confirmed ZIKV infection in nine cases (5.84%). Two cases of vertical ZIKV transmission were confirmed by PCR. One infant showed no signs of congenital ZIKV syndrome and had a normal developmental profile despite first-trimester maternal infection. In the second case, pregnancy was terminated. Production of interferon γ (IFN-γ) by peripheral blood mononuclear cells obtained from pregnant women and umbilical cord blood was measured using enzyme-linked immunospot assay (ELISpot) after stimulation with panels of synthetic peptides derived from the sequence of ZIKV proteins. This analysis revealed that, among all peptide pools tested, those derived from the ZIKV envelope protein generated the strongest IFN-γ response.

Evaluation of the performance of multiple immunoassay diagnostic platforms on the National Microbiology Laboratory SARS-CoV-2 National Serology Panel

BACKGROUND

Serological assays designed to detect SARS-CoV-2 antibodies are being used in serological surveys and other specialized applications. As a result, and to ensure that the outcomes of serological testing meet high quality standards, evaluations are required to assess the performance of these assays and the proficiency of laboratories performing them.

METHODS

A panel of 60 plasma/serum samples from blood donors who had reverse transcriptase-polymerase chain reaction (RT-PCR) confirmed SARS-CoV-2 infections and 21 SARS-CoV-2 negative samples were secured and distributed to interested laboratories within Canada (n = 30) and the United States (n = 1). Participating laboratories were asked to provide details on the diagnostic assays used, the platforms the assays were performed on, and the results obtained for each panel sample. Laboratories were blinded with respect to the expected outcomes.

RESULTS

The performance of the different assays evaluated was excellent, with the high-throughput platforms of Roche, Ortho, and Siemens demonstrating 100% sensitivity. Most other high-throughput platforms had sensitivities of >93%, with the exception of the IgG assay using the Abbott ARCHITECT which had an average sensitivity of only 87%. The majority of the high-throughput platforms also demonstrated very good specificities (>97%).

CONCLUSION

This proficiency study demonstrates that most of the SARS-CoV-2 serological assays utilized by provincial public health or hospital laboratories in Canada have acceptable sensitivity and excellent specificity.

Evaluation of commercial SARS-CoV-2 serological assays in Canadian public health laboratories

The COVID-19 pandemic has led to the influx of immunoassays for the detection of antibodies towards severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) into the global market. The Canadian Public Health Laboratory Network Serology Task Force undertook a nationwide evaluation of twelve laboratory and 6 point-of-care based commercial serological assays for the detection of SARS-CoV-2 antibodies. We determined that there was considerable variability in the performance of individual tests and that an orthogonal testing algorithm should be prioritized to maximize the accuracy and comparability of results across the country. The manual enzyme immunoassays and point-of-care tests evaluated had lower specificity and increased coefficients of variation compared to automated enzyme immunoassays platforms putting into question their utility for large-scale sero-surveillance. Overall, the data presented here provide a comprehensive approach for applying accurate serological assays for longitudinal sero-surveillance and vaccine trials while informing Canadian public health policy.

Cross-Sectional Evaluation of Humoral Responses against SARS-CoV-2 Spike

SARS-CoV-2 is responsible for the coronavirus disease 2019 (COVID-19) pandemic, infecting millions of people and causing hundreds of thousands of deaths. The Spike glycoproteins of SARS-CoV-2 mediate viral entry and are the main targets for neutralizing antibodies. Understanding the antibody response directed against SARS-CoV-2 is crucial for the development of vaccine, therapeutic, and public health interventions. Here, we perform a cross-sectional study on 106 SARS-CoV-2-infected individuals to evaluate humoral responses against SARS-CoV-2 Spike. Most infected individuals elicit anti-Spike antibodies within 2 weeks of the onset of symptoms. The levels of receptor binding domain (RBD)-specific immunoglobulin G (IgG) persist over time, and the levels of anti-RBD IgM decrease after symptom resolution. Although most individuals develop neutralizing antibodies within 2 weeks of infection, the level of neutralizing activity is significantly decreased over time. Our results highlight the importance of studying the persistence of neutralizing activity upon natural SARS-CoV-2 infection.

Cross-sectional evaluation of humoral responses against SARS-CoV-2 Spike

The SARS-CoV-2 virus is responsible for the current worldwide coronavirus disease 2019 (COVID-19) pandemic, infecting millions of people and causing hundreds of thousands of deaths. The Spike glycoprotein of SARS-CoV-2 mediates viral entry and is the main target for neutralizing antibodies. Understanding the antibody response directed against SARS-CoV-2 is crucial for the development of vaccine, therapeutic and public health interventions. Here we performed a cross-sectional study on 106 SARS-CoV-2-infected individuals to evaluate humoral responses against the SARS-CoV-2 Spike. The vast majority of infected individuals elicited anti-Spike antibodies within 2 weeks after the onset of symptoms. The levels of receptor-binding domain (RBD)-specific IgG persisted overtime, while the levels of anti-RBD IgM decreased after symptoms resolution. Some of the elicited antibodies cross-reacted with other human coronaviruses in a genus-restrictive manner. While most of individuals developed neutralizing antibodies within the first two weeks of infection, the level of neutralizing activity was significantly decreased over time. Our results highlight the importance of studying the persistence of neutralizing activity upon natural SARS-CoV-2 infection.

Antibodies to human papillomavirus types 6, 11, 16 and 18: Vertical transmission and clearance in children up to two years of age

Background: There is a paucity of data on the dynamics of human papillomavirus (HPV) antibodies in children. We aimed to describe the vertical transmission and clearance of antibodies against HPV6, 11, 16 and 18 in children. Methods: We used data from pregnant women recruited into the HERITAGE cohort study between 2009 and 2012 who were positive for HPV-DNA at baseline. Dried blood spots were collected during the first trimester in pregnant participants, and at birth, 6, 12, and 24 months of age in children. The level of total immunoglobulin G (IgG) against HPV6, 11, 16 and 18 were measured using Luminex immunoassays. Spearman's coefficients were used to correlate HPV antibody levels between newborns and mothers. Panel and Kaplan-Meier graphics described antibody dynamics in the first 24 months of life. Findings: Antibodies from newborns and mothers (n = 58 pairs) were moderately to highly correlated with coefficients of 0·81 (95% confidence intervals (CI):0·70-0·88), 0·68 (95% CI:0·5-0·80), 0·90 (95% CI:0·83-0·94) and 0·85 (95% CI:0·76-0·91) against HPV6, 11, 16 and 18, respectively. In newborns seropositive at birth, anti-HPV antibodies were cleared by 80% and 100% at 12 and 24 months, respectively. Only two children presented detectable HPV antibodies at 24 months. The first child had no detectable antibodies at birth and the second presented increasing levels after two undetected measures. Interpretation: Correlation between mother and newborn IgG antibodies against HPV suggests vertical transfer. Most children cleared anti-HPV antibodies within six to 12 months. Funding: The Canadian Institutes of Health Research (CIHR).

Phylogenetic analysis of West Nile virus in Quebec, Canada, 2004-2016: Co-circulation of distinct variants harbouring conserved amino acid motifs in North America

West Nile virus (WNV) was introduced for the first time in the western hemisphere in 1999 in New York City. In 2002, a phenotype-modifying mutation (Env-V159A) defined the first North American genotype WN02. So far, three genotypes has been described in North America but little is known about WNV evolution in Canada. We report the phylogenetic characterization of twenty-six WNV genomes isolated from mosquitoes in the province of Quebec. WNV strains found in Quebec are phylogenetically related to American strains collected in northern and southern regions. We also noted the presence of two robust monophyletic groups of isolates characterized by distinct conserved amino acid motifs. These emerging genotypes were detected for several years in different ecosystems. These results highlight the need for the maintenance of a nationwide surveillance to follow the dispersion of emergent WNV genotypes.

Modular dispensability of dysferlin C2 domains reveals rational design for mini-dysferlin molecules

Dysferlin is a large transmembrane protein composed of a C-terminal transmembrane domain, two DysF domains, and seven C2 domains that mediate lipid- and protein-binding interactions. Recessive loss-of-function mutations in dysferlin lead to muscular dystrophies, for which no treatment is currently available. The large size of dysferlin precludes its encapsulation into an adeno-associated virus (AAV), the vector of choice for gene delivery to muscle. To design mini-dysferlin molecules suitable for AAV-mediated gene transfer, we tested internally truncated dysferlin constructs, each lacking one of the seven C2 domains, for their ability to localize to the plasma membrane and to repair laser-induced plasmalemmal wounds in dysferlin-deficient human myoblasts. We demonstrate that the dysferlin C2B, C2C, C2D, and C2E domains are dispensable for correct plasmalemmal localization. Furthermore, we show that the C2B, C2C, and C2E domains and, to a lesser extent, the C2D domain are dispensable for dysferlin membrane repair function. On the basis of these results, we designed small dysferlin molecules that can localize to the plasma membrane and reseal laser-induced plasmalemmal injuries and that are small enough to be incorporated into AAV. These results lay the groundwork for AAV-mediated gene therapy experiments in dysferlin-deficient mouse models.

Dysferlin interacts with tubulin and microtubules in mouse skeletal muscle

Dysferlin is a type II transmembrane protein implicated in surface membrane repair in muscle. Mutations in dysferlin lead to limb girdle muscular dystrophy 2B, Miyoshi Myopathy and distal anterior compartment myopathy. Dysferlin's mode of action is not well understood and only a few protein binding partners have thus far been identified. Using affinity purification followed by liquid chromatography/mass spectrometry, we identified alpha-tubulin as a novel binding partner for dysferlin. The association between dysferlin and alpha-tubulin, as well as between dysferlin and microtubules, was confirmed in vitro by glutathione S-transferase pulldown and microtubule binding assays. These interactions were confirmed in vivo by co-immunoprecipitation. Confocal microscopy revealed that dysferlin and alpha-tubulin co-localized in the perinuclear region and in vesicular structures in myoblasts, and along thin longitudinal structures reminiscent of microtubules in myotubes. We mapped dysferlin's alpha-tubulin-binding region to its C2A and C2B domains. Modulation of calcium levels did not affect dysferlin binding to alpha-tubulin, suggesting that this interaction is calcium-independent. Our studies identified a new binding partner for dysferlin and suggest a role for microtubules in dysferlin trafficking to the sarcolemma.

Characterization of lipid binding specificities of dysferlin C2 domains reveals novel interactions with phosphoinositides

Dysferlin is a type II transmembrane protein implicated in Ca(2+)-dependent sarcolemmal membrane repair. Dysferlin has seven C2 domains, which are lipid and protein binding modules. In this study, we sought to characterize the lipid binding specificity of dysferlin's seven C2 domains. Dysferlin's C2A domain was able to bind to phosphatidylserine (PS), phosphatidylinositol 4-phosphate [PtdIns(4)P], and phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P(2)] in a Ca(2+)-dependent fashion. The remainder of the C2 domains exhibited weaker and Ca(2+)-independent binding to PS and no significant binding to phosphoinositides.

Mutation impact on dysferlin inferred from database analysis and computer-based structural predictions

Dysferlin is a large sarcolemmal protein implicated in the repair of surface membrane tears in muscle cells. Mutations in dysferlin result in limb girdle muscular dystrophy type 2B and Miyoshi myopathy. Using a cDNA based approach we identified eight new pathogenic dysferlin alleles. To better understand how missense mutations could lead to reduced or absent dysferlin expression levels, we mapped missense mutations from our own and from published databases (n=55) to the secondary protein structure of dysferlin, deduced by computerized structural prediction tools. We found the protein to be very sensitive to the alteration of residues that were predicted to be buried inside the protein structure. We identified seven putative C2 domains, one more than commonly reported, of both type I and type II topology in dysferlin. Missense mutations often affected those structures as well as residues that were highly conserved between members of the ferlin family. Thus, alteration of structurally important residues in dysferlin could lead to improper folding and degradation of the mutant protein.

Lariat branch point mutation in the dysferlin gene with mild limb-girdle muscular dystrophy

The authors report a genotype-phenotype correlation in a limb-girdle muscular dystrophy 2B family. Two severely affected sisters were homozygous for a dysferlin null mutation. Their mildly affected compound heterozygous mother harbored, in addition to one null allele, an in-frame exon-skipping allele caused by a novel lariat branch point mutation. The dysferlin molecule arising from the latter allele appeared to partially complement the null mutation, likely accounting for the mother's mild phenotype.

Cathepsins X and B display distinct activity profiles that can be exploited for inhibitor design

The carboxypeptidase and endopeptidase activities of cathepsins X and B, as well as their inhibition by E-64 derivatives, have been investigated in detail and compared. The results clearly demonstrate that cathepsins X and B do not share similar activity profiles against substrates and inhibitors. Using quenched fluorogenic substrates, we show that cathepsin X preferentially cleaves substrates through a monopeptidyl carboxypeptidase pathway, while cathepsin B displays a preference for the dipeptidyl pathway. The preference for one or the other pathway is about the same for both enzymes, i. e. approximately 2 orders of magnitude. Cleavage of a C-terminal dipeptide of a substrate by cathepsin X can be observed under conditions that preclude efficient monopeptidyl carboxypeptidase activity. In addition, an inhibitor designed to exploit the unique structural features responsible for the carboxypeptidase activity of cathepsin X has been synthesized and tested against cathepsins X, B and L. Although of moderate potency, this E-64 derivative is the first reported example of a cathepsin X-specific inhibitor. By comparison, CA074 was found to inactivate cathepsin B at least 34000-fold more efficiently than cathepsin X.

Cathepsins X and B can be differentiated through their respective mono- and dipeptidyl carboxypeptidase activities

Several new cysteine proteases of the papain family have been discovered in the past few years. To help in the assignment of physiological roles and in the design of specific inhibitors, a clear picture of the specificities of these enzymes is needed. One of these novel enzymes, cathepsin X, displays a unique specificity, cleaving single amino acid residues at the C-terminus of substrates very efficiently. In this study, the carboxypeptidase activities and substrate specificity of cathepsins X and B have been investigated in detail and compared. Using quenched fluorogenic substrates and HPLC measurements, it was shown that cathepsin X preferentially cleaves substrates through a monopeptidyl carboxypeptidase pathway, while cathepsin B displays a preference for the dipeptidyl pathway. The preference for one or the other pathway is about the same for both enzymes, i.e., approximately 2 orders of magnitude, a result supported by molecular modeling of enzyme-substrate complexes. Cleavage of a C-terminal dipeptide of a substrate by cathepsin X can become more important under conditions that preclude efficient monopeptidyl carboxypeptidase activity, e.g., nonoptimal interactions in subsites S(2)-S(1). These results confirm that cathepsin X is designed to function as a monopeptidyl carboxypeptidase. Contrary to a recent report [Klemencic, I., et al. (2000) Eur. J. Biochem. 267, 5404-5412], it is shown that cathepsins X and B do not share similar activity profiles, and that reagents are available to clearly distinguish the two enzymes. In particular, CA074 was found to inactivate cathepsin B at least 34000-fold more efficiently than cathepsin X. The insights obtained from this and previous studies have been used to produce an inhibitor designed to exploit the unique structural features responsible for the carboxypeptidase activity of cathepsin X. Although of moderate potency, this E-64 derivative is the first reported example of a cathepsin X-specific inhibitor.

Molecular basis of antibiotic resistance and beta-lactamase inhibition by mechanism-based inactivators: perspectives and future directions

Antibacterial chemotherapy is particularly striking in the family of penicillins and cephalosporins. Over 40 structurally different beta-lactam molecules are available in 73 formulations and the majority of them are currently prescribed for medical use in hospitals. beta-Lactams are well tolerated by humans with few side effects. They interact very specifically with their bacterial target, the D-alanyl-D-alanine carboxypeptidase-transpeptidase usually referred to as DD-peptidase. The outstanding number of beta-lactamases produced by bacteria represent a serious threat to the clinical utility of beta-lactams. The discovery of beta-lactamase inhibitors was thought to solve, in part, the problem of resistance. Unfortunately, bacteria have evolved new mechanisms of resistance to overcome the inhibitory effects of beta-lactamase inactivators. Here, we summarize the diversified mechanistic features of class A beta-lactamases interactions with mechanism-based inhibitors using available microbiological, kinetic and structural data for the prototype TEM beta-lactamases. A brief historical overview of the strategies developed to counteract beta-lactamases will be presented followed by a short description of the chemical events which lead to the inactivation of TEM beta-lactamase by inhibitors from different classes. Finally, an update on the clinical prevalence of natural and inhibitor-resistant enzyme mutants, the total chemical synthesis to design and synthesize a new structure and produced a broad spectrum beta-lactamase inhibitor that mimics the beta-lactam ring, but does not contain it is discussed.

Evaluation of inhibition of the carbenicillin-hydrolyzing beta-lactamase PSE-4 by the clinically used mechanism-based inhibitors

Characterization of the biochemical steps in the inactivation chemistry of clavulanic acid, sulbactam and tazobactam with the carbenicillin-hydrolyzing beta-lactamase PSE-4 from Pseudomonas aeruginosa is described. Although tazobactam showed the highest affinity to the enzyme, all three inactivators were excellent inhibitors for this enzyme. Transient inhibition was observed for the three inactivators before the onset of irreversible inactivation of the enzyme. Partition ratios (k(cat)/k(inact)) of 11, 41 and 131 were obtained with clavulanic acid, tazobactam and sulbactam, respectively. Furthermore, these values were found to be 14-fold, 3-fold and 80-fold lower, respectively, than the values obtained for the clinically important TEM-1 beta-lactamase. The kinetic findings were put in perspective by determining the computational models for the pre-acylation complexes and the immediate acyl-enzyme intermediates for all three inactivators. A discussion of the pertinent structural factors is presented, with PSE-4 showing subtle differences in interactions with the three inhibitors compared to the TEM-1 enzyme.

Beta-lactamases and outer membrane investigations in beta-lactam-resistant Comamonas acidovorans strains

Imipenem-induced beta-lactamase (level of expression, specific activity and kinetic parameters (Vmax and Km) in response to nitrocefin) and outer membrane proteins (OMPs) (hydrophobicity, permeability and electrophoretic pattern) were characterized in, one beta-lactam sensitive (PAC-9), one resistant (PAC-1) and two resistant laboratory mutants (PAC-9M, PAC-9M2) of Comamonas acidovorans strains. Beta-lactamases from both mutant strains showed different Vmax values compared to the parental strains. Beta-lactam resistance was found to be associated in PAC-1 with inducible beta-lactamase production and OMP alteration by the appearance of a 102-KDa protein. Moreover, PAC-1 was less permeable to nitrocefin than PAC-9. These data indicate that C. acidovorans resistance to beta-lactam resulted from synergy between beta-lactamase and OMP alterations.

Roles of amino acids 161 to 179 in the PSE-4 omega loop in substrate specificity and in resistance to ceftazidime

The PSE-4 enzyme is a prototype carbenicillin-hydrolyzing enzyme exhibiting high activity against penicillins and early cephalosporins. To understand the mechanism that modulates substrate profiles and to verify the ability of PSE-4 to extend its substrate specificity toward expanded-spectrum cephalosporins, we used random replacement mutagenesis to generate six random libraries from amino acids 162 to 179 in the Omega loop. This region is known from studies with TEM-1 to be implicated in substrate specificity. It was found that the mechanism modulating ceftazidime hydrolysis in PSE-4 was different from that in TEM-1. The specificity of class 2c carbenicillin-hydrolyzing enzymes could not be assigned to the Omega loop of PSE-4. Analysis of the percentage of functional enzymes revealed that the hydrolysis of ampicillin was more affected than hydrolysis of carbenicillin by amino acid substitutions at positions 162 to 164 and 165 to 167.