Diagnostic performance of influenza viruses and RSV rapid antigen detection tests in children in tertiary care

•

The here studied rapid antigen detection test (RADT) BinaxNOW RSV has a high sensitivity and positive predictive value.

•

RADT BinaxNOW Influenza A&B has a relatively low sensitivity and positive predictive value.

•

We advise a restricted use of RADT BinaxNOW Influenza A&B in a tertiary paediatric care setting.

Background

Rapid antigen detection tests (RADTs) are increasingly used to detect influenza viruses and respiratory syncytial virus (RSV). However, their sensitivity and specificity are a matter of debate, challenging their clinical usefulness.

Objectives

Comparing diagnostic performances of BinaxNow Influenza AB^® (BNI) and BinaxNow RSV^® (BNR), to those of real-time reverse transcriptase PCR (RT-PCR), virus isolation and direct immunofluorescence (D-IF) in paediatric patients.

Study design

Between November 2005 and September 2013, 521 nasal washings from symptomatic children (age <5 years) attending our tertiary care centre were tested, with a combination of the respective assays using RT-PCR as gold standard.

Results

Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of BNI were 69% (confidence interval [CI] [51–83]), 96% [94–97], 55% [39–70] and 98% [96–99] respectively. Of eleven false-negative samples, RT-PCR Ct-values were higher than all RT-PCR positive test results (27 vs 22, p = 0.012). Of twenty false-positive samples, none were culture positive and two tested positive in D-IF.

Sensitivity, specificity, PPV and NPV for BNR were 79% [73–85], 98% [96–99], 97% [93–99] and 88% [84–91]. Of the 42 false-negative samples the median Ct-value was higher than that of all RT-PCR positive samples (31 vs 23, p < 0.0001). Five false-positive samples were detected. Three of these tested positive for RSV in virus isolation and D-IF.

Conclusions

RADTs have a high specificity with BNR being superior to BNI. However, their relative low sensitivity limits their usefulness for clinical decision making in a tertiary care paediatric hospital.

Isolation of MERS coronavirus from a dromedary camel, Qatar, 2014

We obtained the full genome of Middle East respiratory syndrome coronavirus (MERS-CoV) from a camel in Qatar. This virus is highly similar to the human England/Qatar 1 virus isolated in 2012. The MERS-CoV from the camel efficiently replicated in human cells, providing further evidence for the zoonotic potential of MERS-CoV from camels.

Influenza: from zoonosis to pandemic

Probable epidemic influenza outbreaks have been described as early as the 5th century BC, as part of the Cough of Perinthus associated with the winter solstice, in Hippocrates' Corpus Hippocraticum “Of the Epidemics” [1]. The word “influenza” was first introduced in the 16th century, defining the illness of the cold season that in the early 1930s was shown to be caused by “filterable agents”, since then called influenza viruses. Three types or genera of influenza viruses have been recognised (influenza A, B and C viruses), while a fourth genus has been recently proposed [2]. Today, we distinguish three manifestations of influenza in humans, which may impose from mild to severe morbidity and mortality burdens: zoonotic, pandemic and seasonal influenza, all caused by an infection with an influenza virus. Although our arsenal of intervention strategies for influenza has advanced in the past decades and a growing public conception has arisen of influenza as a usually seasonal inconvenience, threats posed by influenza A viruses, with their different manifestations and associated complications, are continuously knocking on our door.

Global surveillance and advances in vaccine technology are essential to answer the threat of influenza pandemicshttp://ow.ly/Yt3e4

Immunogenicity and protective efficacy of recombinant Modified Vaccinia virus Ankara candidate vaccines delivering West Nile virus envelope antigens

West Nile virus (WNV) cycles between insects and wild birds, and is transmitted via mosquito vectors to horses and humans, potentially causing severe neuroinvasive disease. Modified Vaccinia virus Ankara (MVA) is an advanced viral vector for developing new recombinant vaccines against infectious diseases and cancer. Here, we generated and evaluated recombinant MVA candidate vaccines that deliver WNV envelope (E) antigens and fulfil all the requirements to proceed to clinical testing in humans. Infections of human and equine cell cultures with recombinant MVA demonstrated efficient synthesis and secretion of WNV envelope proteins in mammalian cells non-permissive for MVA replication. Prime-boost immunizations in BALB/c mice readily induced circulating serum antibodies binding to recombinant WNV E protein and neutralizing WNV in tissue culture infections. Vaccinations in HLA-A2.1-/HLA-DR1-transgenic H-2 class I-/class II-knockout mice elicited WNV E-specific CD8+ T cell responses. Moreover, the MVA-WNV candidate vaccines protected C57BL/6 mice against lineage 1 and lineage 2 WNV infection and induced heterologous neutralizing antibodies. Thus, further studies are warranted to evaluate these recombinant MVA-WNV vaccines in other preclinical models and use them as candidate vaccine in humans.

Susceptibility of Carrion Crows to Experimental Infection with Lineage 1 and 2 West Nile Viruses

West Nile virus (WNV) outbreaks in North America have been characterized by substantial die-offs of American crows (Corvus brachyrhynchos). In contrast, a low incidence of bird deaths has been observed during WNV epidemic activity in Europe. To examine the susceptibility of the western European counterpart of American crows, we inoculated carrion crows (Corvus corone) with WNV strains isolated in Greece (Gr-10), Italy (FIN and Ita09), and Hungary (578/10) and with the highly virulent North American genotype strain (NY99). We also inoculated American crows with a selection of these strains to examine the strains' virulence in a highly susceptible bird species. Infection with all strains, except WNV FIN, resulted in high rates of death and high-level viremia in both bird species and virus dissemination to several organs. These results suggest that carrion crows are highly susceptible to WNV and may potentially be useful as part of dead bird surveillance for early warning of WNV activity in Europe.

In Vitro and in Vivo Evaluation of Mutations in the NS Region of Lineage 2 West Nile Virus Associated with Neuroinvasiveness in a Mammalian Model

West Nile virus (WNV) strains may differ significantly in neuroinvasiveness in vertebrate hosts. In contrast to genetic lineage 1 WNVs, molecular determinants of pathogenic lineage 2 strains have not been experimentally confirmed so far. A full-length infectious clone of a neurovirulent WNV lineage 2 strain (578/10; Central Europe) was generated and amino acid substitutions that have been shown to attenuate lineage 1 WNVs were introduced into the nonstructural proteins (NS1 (P250L), NS2A (A30P), NS3 (P249H) NS4B (P38G, C102S, E249G)). The mouse neuroinvasive phenotype of each mutant virus was examined following intraperitoneal inoculation of C57BL/6 mice. Only the NS1-P250L mutation was associated with a significant attenuation of virulence in mice compared to the wild-type. Multiplication kinetics in cell culture revealed significantly lower infectious virus titres for the NS1 mutant compared to the wild-type, as well as significantly lower amounts of positive and negative stranded RNA.

Molecular epidemiology and genetic diversity of hepatitis B virus in Ethiopia

Although hepatitis B virus (HBV) infection is hyperendemic in Ethiopia and constitutes a major public health problem, little is known about its genetic diversity, genotypes, and circulation. The aim of this study was to determine the molecular epidemiology and genetic diversity of HBV in Ethiopia, using 391 serum samples collected from HBsAg-positive blood donors living in five different geographic regions. The HBV S/pol gene was amplified, sequenced, and HBV genotypes, subgenotypes, serotypes, and major hydrophilic region (MHR) variants were determined. Phylogenetic analysis of 371 samples (95%) revealed the distribution of genotypes A (78%) and D (22%) in Ethiopia. Further phylogenetic analysis identified one subgenotype (A1) within genotype A, and 4 subgenotypes within genotype D (D1; 1.3%, D2; 55%, D4; 2.5%, and D6; 8.8%). Importantly, 24 isolates (30%) of genotype D formed a novel phylogenetic cluster, distinct from any known D subgenotypes, and two A/D recombinants. Analysis of predicted amino-acid sequences within the HBsAg revealed four serotypes: adw2 (79%), ayw1 (3.1%), ayw2 (7.8%), and ayw3 (11.6%). Subsequent examination of sequences showed that 51 HBV isolates (14%) had mutations in the MHR and 8 isolates (2.2%) in the reverse transcriptase known to confer antiviral resistance. This study provides the first description of HBV genetic diversity in Ethiopia with a predominance of subgenotypes A1 and D2, and also identified HBV isolates that could represent a novel subgenotype. Furthermore, a significant prevalence of HBsAg variants in Ethiopian population is revealed.

An orthopoxvirus-based vaccine reduces virus excretion after MERS-CoV infection in dromedary camels

Middle East respiratory syndrome coronavirus (MERS-CoV) infections have led to an ongoing outbreak in humans, which was fueled by multiple zoonotic MERS-CoV introductions from dromedary camels. In addition to the implementation of hygiene measures to limit further camel-to-human and human-to-human transmissions, vaccine-mediated reduction of MERS-CoV spread from the animal reservoir may be envisaged. Here we show that a modified vaccinia virus Ankara (MVA) vaccine expressing the MERS-CoV spike protein confers mucosal immunity in dromedary camels. Compared with results for control animals, we observed a significant reduction of excreted infectious virus and viral RNA transcripts in vaccinated animals upon MERS-CoV challenge. Protection correlated with the presence of serum neutralizing antibodies to MERS-CoV. Induction of MVA-specific antibodies that cross-neutralize camelpox virus would also provide protection against camelpox.

Characterization of the immune response in ganglia after primary simian varicella virus infection

Primary simian varicella virus (SVV) infection in non-human primates causes varicella, after which the virus becomes latent in ganglionic neurons and reactivates to cause zoster. The host response in ganglia during establishment of latency is ill-defined. Ganglia from five African green monkeys (AGMs) obtained at 9, 13, and 20 days post-intratracheal SVV inoculation (dpi) were analyzed by ex vivo flow cytometry, immunohistochemistry, and in situ hybridization. Ganglia at 13 and 20 dpi exhibited mild inflammation. Immune infiltrates consisted mostly of CD8(dim) and CD8(bright) memory T cells, some of which expressed granzyme B, and fewer CD11c(+) and CD68(+) cells. Chemoattractant CXCL10 transcripts were expressed in neurons and infiltrating inflammatory cells but did not co-localize with SVV open reading frame 63 (ORF63) RNA expression. Satellite glial cells expressed increased levels of activation markers CD68 and MHC class II at 13 and 20 dpi compared to those at 9 dpi. Overall, local immune responses emerged as viral DNA load in ganglia declined, suggesting that intra-ganglionic immunity contributes to restricting SVV replication.

Seroprevalence of Antibodies against Seal Influenza A(H10N7) Virus in Harbor Seals and Gray Seals from the Netherlands

In the spring and summer 2014, an outbreak of seal influenza A(H10N7) virus infection occurred among harbor seals (Phoca vitulina) off the coasts of Sweden and Denmark. This virus subsequently spread to harbor seals off the coasts of Germany and the Netherlands. While thousands of seals were reported dead in Sweden, Denmark and Germany, only a limited number of seals were found dead in the Netherlands. To determine the extent of exposure of seals in the Netherlands to influenza A/H10N7 virus, we measured specific antibody titers in serum samples from live-captured seals and seals admitted for rehabilitation in the Netherlands by use of a hemagglutination inhibition assay and an ELISA. In harbor seals in 2015, antibodies against seal influenza A(H10N7) virus were detected in 41% (32 out of 78) pups, 10% (5 out of 52) weaners, and 58% (7 out of 12) subadults or adults. In gray seals (Halichoerus grypus) in 2015, specific antibodies were not found in the pups (n = 26), but in 26% (5 out of 19) of the older animals. These findings indicate that, despite apparent low mortality, infection with seal influenza A(H10N7) virus was geographically widespread and also occurred in grey seals.

Recovering full-length viral genomes from metagenomes

Infectious disease metagenomics is driven by the question: “what is causing the disease?” in contrast to classical metagenome studies which are guided by “what is out there?” In case of a novel virus, a first step to eventually establishing etiology can be to recover a full-length viral genome from a metagenomic sample. However, retrieval of a full-length genome of a divergent virus is technically challenging and can be time-consuming and costly. Here we discuss different assembly and fragment linkage strategies such as iterative assembly, motif searches, k-mer frequency profiling, coverage profile binning, and other strategies used to recover genomes of potential viral pathogens in a timely and cost-effective manner.

Dengue viruses cluster antigenically but not as discrete serotypes

The four genetically divergent dengue virus (DENV) types are traditionally classified as serotypes. Antigenic and genetic differences among the DENV types influence disease outcome, vaccine-induced protection, epidemic magnitude, and viral evolution. We characterized antigenic diversity in the DENV types by antigenic maps constructed from neutralizing antibody titers obtained from African green monkeys and after human vaccination and natural infections. Genetically, geographically, and temporally, diverse DENV isolates clustered loosely by type, but we found that many are as similar antigenically to a virus of a different type as to some viruses of the same type. Primary infection antisera did not neutralize all viruses of the same DENV type any better than other types did up to 2 years after infection and did not show improved neutralization to homologous type isolates. That the canonical DENV types are not antigenically homogeneous has implications for vaccination and research on the dynamics of immunity, disease, and the evolution of DENV.

Prevalence and clinical consequences of Hepatitis E in patients who underwent liver transplantation for chronic Hepatitis C in the United States

Background

Infection with hepatitis E virus (HEV) in immunocompromised patients can lead to severe liver disease. Treatment options for HEV include peginterferon or ribavirin, routinely also used for the treatment of hepatitis C virus (HCV) infection.

We determined the prevalence and clinical consequences of HEV in United States (US) based patients who underwent liver transplantation (LT) for chronic HCV.

Methods

Seroprevalence of HEV in 145 US LT recipients with a history of chronic HCV was determined pre-LT, 1, 3 and 5 years post-LT. All last available samples and all samples in IgM positive patients and post-LT IgG seroconverters were tested for HEV RNA.

Results

Overall anti-HEV seroprevalence was 42 %. Five patients were HEV IgM positive pre-LT, one patient had IgM seroconversion post-LT and eight patients had IgG seroconversion post-LT. None of the tested samples were positive for HEV RNA. Eight out of nine of the post-LT seroconverters had been treated for HCV recurrence before or at the moment of seroconversion.

Conclusions

LT recipients in the US are at risk of acquiring HEV. Post-LT HCV treatment with interferons and/or ribavirin may have protected patients against chronic HEV. With the arrival of new direct antiviral agents for the treatment of HCV and the elimination of peginterferon and ribavirin from HCV treatment regimens, the prevalence of chronic HEV in this population may rise again.

A novel antigen capture ELISA for the specific detection of IgG antibodies to elephant endotheliotropic herpes virus

BACKGROUND

Elephants are classified as critically endangered animals by the International Union for Conservation of Species (IUCN). Elephant endotheliotropic herpesvirus (EEHV) poses a large threat to breeding programs of captive Asian elephants by causing fatal haemorrhagic disease. EEHV infection is detected by PCR in samples from both clinically ill and asymptomatic elephants with an active infection, whereas latent carriers can be distinguished exclusively via serological assays. To date, identification of latent carriers has been challenging, since there are no serological assays capable of detecting seropositive elephants.

RESULTS

Here we describe a novel ELISA that specifically detects EEHV antibodies circulating in Asian elephant plasma/serum. Approximately 80 % of PCR positive elephants display EEHV-specific antibodies. Monitoring three Asian elephant herds from European zoos revealed that the serostatus of elephants within a herd varied from non-detectable to high titers. The antibody titers showed typical herpes-like rise-and-fall patterns in time which occur in all seropositive animals in the herd more or less simultaneously.

CONCLUSIONS

This study shows that the developed ELISA is suitable to detect antibodies specific to EEHV. It allows study of EEHV seroprevalence in Asian elephants. Results confirm that EEHV prevalence among Asian elephants (whether captive-born or wild-caught) is high.

Human Influenza A Virus-Specific CD8+ T-Cell Response Is Long-lived

Animal and human studies have demonstrated the importance of influenza A virus (IAV)-specific CD8(+) cytotoxic T lymphocytes (CTLs) in heterosubtypic cross-protective immunity. Using peripheral blood mononuclear cells obtained intermittently from healthy HLA-typed blood donors between 1999 and 2012, we were able to demonstrate that IAV-specific CTLs are long-lived. Intercurrent IAV infections transiently increase the frequency of functionally distinct subsets of IAV-specific CTLs, in particular effector and effector memory T cells.

Re-evaluation of hepatitis B virus clinical phases by systems biology identifies unappreciated roles for the innate immune response and B cells

To identify immunological mechanisms that govern distinct clinical phases of a chronic hepatitis B virus (HBV) infection-immune tolerant (IT), immune active (IA), inactive carrier (IC), and hepatitis B e antigen (HBeAg)-negative (ENEG) hepatitis phases-we performed a systems biology study. Serum samples from untreated chronic HBV patients (n = 71) were used for multiplex cytokine measurements, quantitative hepatitis B surface antigen (HBsAg), HBeAg levels, HBV genotype, and mutant analysis. Leukocytes were phenotyped using multicolor flow cytometry, and whole-blood transcriptome profiles were generated. The latter were compared with liver biopsy transcriptomes from IA (n = 16) and IT (n = 3) patients. HBV viral load as well as HBeAg and HBsAg levels (P < 0.001), but not leukocyte composition, differed significantly between distinct phases. Serum macrophage chemotactic protein 1, interleukin-12p40, interferon (IFN)-gamma-inducible protein 10, and macrophage inflammatory protein 1 beta levels were different between two or more clinical phases (P < 0.05). Comparison of blood transcriptomes identified 64 differentially expressed genes. The gene signature distinguishing IA from IT and IC patients was predominantly composed of highly up-regulated immunoglobulin-encoding genes. Modular repertoire analysis using gene sets clustered according to similar expression patterns corroborated the abundant expression of B-cell function-related genes in IA patients and pointed toward increased (ISG) transcript levels in IT patients, compared to subsequent phases. Natural killer cell activities were clustered in clinical phases with biochemical liver damage (IA and ENEG phases), whereas T-cell activities were higher in all phases, compared to IT patients. B-cell-related transcripts proved to be higher in biopsies from IA versus IT patients.

CONCLUSION

HBV clinical phases are characterized by distinct blood gene signatures. Innate IFN and B-cell responses are highly active during the IT and IA phases, respectively. This suggests that the presumed immune tolerance in chronic HBV infections needs to be redefined.

Climate Factors as Important Determinants of Dengue Incidence in Curaçao

Macro- and microclimates may have variable impact on dengue incidence in different settings. We estimated the short-term impact and delayed effects of climate variables on dengue morbidity in Curaçao. Monthly dengue incidence data from 1999 to 2009 were included to estimate the short-term influences of climate variables by employing wavelet analysis, generalized additive models (GAM) and distributed lag nonlinear models (DLNM) on rainfall, temperature and relative humidity in relation to dengue incidence. Dengue incidence showed a significant irregular 4-year multi-annual cycle associated with climate variables. Based on GAM, temperature showed a U-shape, while humidity and rainfall exhibited a dome-shaped association, suggesting that deviation from mean temperature increases and deviation from mean humidity and rainfall decreases dengue incidence, respectively. Rainfall was associated with an immediate increase in dengue incidence of 4.1% (95% CI: 2.2-8.1%) after a 10-mm increase, with a maximum increase of 6.5% (95% CI: 3.2-10.0%) after 1.5 month lag. A 1 °C decrease of mean temperature was associated with a RR of 17.4% (95% CI: 11.2-27.0%); the effect was inversed for a 1°C increase of mean temperature (RR= 0.457, 95% CI: 0.278-0.752). Climate variables are important determinants of dengue incidence and provide insight into its short-term effects. An increase in mean temperature was associated with lower dengue incidence, whereas lower temperatures were associated with higher dengue incidence.

Human bocavirus infection as a cause of severe acute respiratory tract infection in children

In 2005 human bocavirus (HBoV) was discovered in respiratory tract samples of children. The role of HBoV as the single causative agent for respiratory tract infections remains unclear. Detection of HBoV in children with respiratory disease is frequently in combination with other viruses or bacteria. We set up an algorithm to study whether HBoV alone can cause severe acute respiratory tract infection (SARI) in children. The algorithm was developed to exclude cases with no other likely cause than HBoV for the need for admission to the paediatric intensive care unit (PICU) with SARI. We searched for other viruses by next-generation sequencing (NGS) in these cases and studied their HBoV viral loads. To benchmark our algorithm, the same was applied to respiratory syncytial virus (RSV)-positive patients. From our total group of 990 patients who tested positive for a respiratory virus by means of RT-PCR, HBoV and RSV were detected in 178 and 366 children admitted to our hospital. Forty-nine HBoV-positive patients and 72 RSV-positive patients were admitted to the PICU. We found seven single HBoV-infected cases with SARI admitted to PICU (7/49, 14%). They had no other detectable virus by NGS. They had much higher HBoV loads than other patients positive for HBoV. We identified 14 RSV-infected SARI patients with a single RSV infection (14/72, 19%). We conclude that our study provides strong support that HBoV can cause SARI in children in the absence of viral and bacterial co-infections.

Market implementation of the MVA platform for pre-pandemic and pandemic influenza vaccines: A quantitative key opinion leader analysis

A quantitative method is presented to rank strengths, weaknesses, opportunities, and threats (SWOT) of modified vaccinia virus Ankara (MVA) as a platform for pre-pandemic and pandemic influenza vaccines. Analytic hierarchy process (AHP) was applied to achieve pairwise comparisons among SWOT factors in order to prioritize them. Key opinion leaders (KOLs) in the influenza vaccine field were interviewed to collect a unique dataset to evaluate the market potential of this platform.

The purpose of this study, to evaluate commercial potential of the MVA platform for the development of novel generation pandemic influenza vaccines, is accomplished by using a SWOT and AHP combined analytic method. Application of the SWOT–AHP model indicates that its strengths are considered more important by KOLs than its weaknesses, opportunities, and threats. Particularly, the inherent immunogenicity capability of MVA without the requirement of an adjuvant is the most important factor to increase commercial attractiveness of this platform. Concerns regarding vector vaccines and anti-vector immunity are considered its most important weakness, which might lower public health value of this platform. Furthermore, evaluation of the results of this study emphasizes equally important role that threats and opportunities of this platform play.

This study further highlights unmet needs in the influenza vaccine market, which could be addressed by the implementation of the MVA platform. Broad use of MVA in clinical trials shows great promise for this vector as vaccine platform for pre-pandemic and pandemic influenza and threats by other respiratory viruses. Moreover, from the results of the clinical trials seem that MVA is particularly attractive for development of vaccines against pathogens for which no, or only insufficiently effective vaccines, are available.