Evaluation of a new dot blot enzyme immunoassay (directigen flu A+B) for simultaneous and differential detection of influenza a and B virus antigens from respiratory samples

In situ bio-mineralized Mn nanoadjuvant enhances anti-influenza immunity of recombinant virus-like particle vaccines

Virus like particles (VLPs) have been well recognized as one of the most important vaccine platforms due to their structural similarity to natural viruses to induce effective humoral and cellular immune responses. Nevertheless, lack of viral nucleic acids in VLPs usually leads the vaccine candidates less efficient in provoking innate immune against viral infection. Here, we constructed a biomimetic dual antigen hybrid influenza nanovaccines THM-HA@Mn with robust immunogenicity via in situ synthesizing a stimulator of interferon genes (STING) agonist Mn3O4 inside the cavity of a recombinant Hepatitis B core antigen VLP (HBc VLP) having fused SpyTag and influenza M2e antigen peptides (Tag-HBc-M2e, THM for short), followed by conjugating a recombinant hemagglutinin (rHA) antigen on the surface of the nanoparticles through SpyTag/SpyCatcher ligating. Such inside Mn3O4 immunostimulator-outside rHA antigen design, together with the chimeric M2e antigen on the HBc skeleton, enabled the synthesized hybrid nanovaccines THM-HA@Mn to well imitate the spatial distribution of M2e/HA antigens and immunostimulant in natural influenza virus. In vitro cellular experiments indicated that compared with the THM-HA antigen without Mn3O4 and a mixture vaccine consisting of THM-HA + MnOx, the THM-HA@Mn hybrid nanovaccines showed the highest efficacies in dendritic cells uptake and in promoting BMDC maturation, as well as inducing expression of TNF-α and type I interferon IFN-β. The THM-HA@Mn also displayed the most sustained antigen release at the injection site, the highest efficacies in promoting the DC maturation in lymph nodes and germinal center B cells activation in the spleen of the immunized mice. The co-delivery of immunostimulant and antigens enabled the THM-HA@Mn nanovaccines to induce the highest systemic antigen-specific antibody responses and cellular immunogenicity in mice. Together with the excellent colloid dispersion stability, low cytotoxicity, as well as good biosafety, the synthetic hybrid nanovaccines presented in this study offers a promising strategy to design VLP-based vaccine with robust natural and adaptive immunogenicity against emerging viral pathogens.

The position of Spy Tag/Catcher system in hepatitis B core protein particles affects the immunogenicity and stability of the synthetic vaccine

Presenting exogenous antigens on virus-like particles (VLPs) through "plug-and-display" decoration strategies based on SpyTag/SpyCatcher isopeptide bonding have emerged as attractive technology for vaccine synthesis. However, whether the position of ligation site in VLPs will impose effects on immunogenicity and physiochemical properties of the synthetic vaccine remains rarely investigated. Here in the present work, the well-established hepatitis B core (HBc) protein was used as chassis to construct dual-antigen influenza nanovaccines, with the conserved epitope peptides derived from extracellular domain of matrix protein M2 (M2e) and hemagglutinin (HA) as target antigens. The M2e antigen was genetically fused to the HBc in the MIR region, together with the SpyTag peptide, which was fused either in the MIR region or at the N-terminal of the protein, so that a recombinant HA antigen (rHA) linked to SpyCatcher can be displayed on it, at two different localizations. Both synthetic nanovaccines showed ability in inducing strong M2e and rHA-specific antibodies and cellular immunogenicity; nevertheless, the one in which rHA was conjugated by N-terminal Tag ligation, was superior to another one synthesized by linking the rHA to MIR region SpyTagged-HBc in all aspects, including higher antigen-specific immunogenicity responses, lower anti-HBc carrier antibody, as well as better dispersion stability. Surface charge and hydrophobicity properties of the two synthetic nanovaccines were analyzed, results revealed that linking the rHA to MIR region SpyTagged-HBc lead to more significant and disadvantageous alteration in physiochemical properties of the HBc chassis. This study will expand our knowledge on "plug-and-display" decoration strategies and provide helpful guidance for the rational design of HBc-VLPs based modular vaccines by using SpyTag/Catcher synthesis.

Determination of the frequency of influensa-A and B antigens in swab samples in differentiating the diagnosis of influensa infection from other causes of upper respiratory tract infection

Aim: The aim of this study is to determine the frequency of influenza-A and B antigens in swab samples and to examine their potential changes at the time of initial diagnosis in differentiating the diagnosis of influenza infection from other causes of upper respiratory tract infection by physical examination and clinical vital signs in the emergency room. Materials and Methods: This retrospective cross-sectional descriptive research analyzed 113 patients with Influensa-A (n:8 and B (n:15) over the age of 18 who applied to the emergency department in the last three years, were diagnosed with acute upper respiratory tract and underwent nasopharyngeal swab sampling were included in the study. The data of the patients were accessed digitally from the University hospital database. Results: Verbal dysphagia scores (p0.05). White blood cells in blood count parameters were lower in the influenza test-positive group (p0.05). Conclusion: Influenza infections should be examined in detail regarding costs to public health and social security institutions, considering the burdens of diagnosis and treatment on the patient and society.

Advances and insights in the diagnosis of viral infections

Viral infections are the most common among diseases that globally require around 60 percent of medical care. However, in the heat of the pandemic, there was a lack of medical equipment and inpatient facilities to provide all patients with viral infections. The detection of viral infections is possible in three general ways such as (i) direct virus detection, which is performed immediately 1-3 days after the infection, (ii) determination of antibodies against some virus proteins mainly observed during/after virus incubation period, (iii) detection of virus-induced disease when specific tissue changes in the organism. This review surveys some global pandemics from 1889 to 2020, virus types, which induced these pandemics, and symptoms of some viral diseases. Non-analytical methods such as radiology and microscopy also are overviewed. This review overlooks molecular analysis methods such as nucleic acid amplification, antibody-antigen complex determination, CRISPR-Cas system-based viral genome determination methods. Methods widely used in the certificated diagnostic laboratory for SARS-CoV-2, Influenza A, B, C, HIV, and other viruses during a viral pandemic are outlined. A comprehensive overview of molecular analytical methods has shown that the assay's sensitivity, accuracy, and suitability for virus detection depends on the choice of the number of regions in the viral open reading frame (ORF) genome sequence and the validity of the selected analytical method.

Comparison of Directigen Flu A+B with Real Time PCR in the Diagnosis of Influenza

Early diagnosis and treatment of patients with influenza is the reason why physicians need rapid high-sensitivity influenza diagnostic tests that require no complex lab equipment and can be performed and interpreted within 15 min. The Aim of this study was to compare the rapid Directigen Flu A+B test with real time PCR for detection of influenza viruses in the Republic of Macedonia.

MATERIALS AND METHODS

One-hundred-eight respiratory samples (combined nose and throat swabs) were routinely collected for detection of influenza virus during influenza seasons. Forty-one patients were pediatric cases and 59 were adult. Their mean age was 23 years. The patients were allocated into 6 age groups: 0-4 yrs, 5-9 yrs, 10-14 yrs, 15-19 yrs, 20-64 yrs and > 65 yrs. Each sample was tested with Directigen Flu A+B and CDC real time PCR kit for detection and typisation/subtypisation of influenza according to the lab diagnostic protocol.

RESULTS

Directigen Flu A+B identified influenza A virus in 20 (18.5%) samples and influenza B virus in two 2 (1.9%) samples. The high specificity (100%) and PPV of Directigen Flu A+B we found in our study shows that the positive results do not need to be confirmed. The overall sensitivity of Directigen Flu A+B is 35.1% for influenza A virus and 33.0% for influenza B virus. The sensitivity for influenza A is higher among children hospitalized (45.0%) and outpatients (40.0%) versus adults.

CONCLUSION

Directigen Flu A+B has relatively low sensitivity for detection of influenza viruses in combined nose and throat swabs. Negative results must be confirmed.

Multiplex RT-PCR and indirect immunofluorescence assays for detection and subtyping of human influenza virus in Tunisia

Influenza viruses are negative stranded segmented RNA viruses belonging to Orthomyxoviridae family. They are classified into three types A, B, and C. Type A influenza viruses are classified into subtypes according to the antigenic characters of the surface glycoproteins: hemagglutinin (H) and neuraminidase (N). The aim of the present study is to develop a fast and reliable multiplex RT-PCR technique for detecting simultaneously the subtypes A/H1N1 and A/H3N2 of influenza virus. Our study included 398 patients (mean age 30.33 ± 19.92 years) with flu or flu-like syndromes, consulting physicians affiliated with collaborating teams. A multiplex RT-PCR detecting A/H1N1 and A/H3N2 influenza viruses and an examination by indirect immunofluorescence (IFI) were performed. In the optimized conditions, we diagnosed by IFI a viral infection in 90 patients (22.6 %): 85 cases of influenza type A, four cases of influenza type B, and only one case of coinfection with types A and B. An evaluation of the technique was performed on 19 clinical specimens positive in IFI, and we detected eight cases of A/H3N2, five cases of A/H1N1, one case of influenza virus type A which is not an H1N1 nor H3N2, and five negative cases. Multiplex RT-PCR is a sensitive technique allowing an effective and fast diagnosis of respiratory infections caused by influenza viruses in which the optimization often collides with problems of sensibility.

Multicenter clinical performance evaluation of BD Veritor™ system for rapid detection of respiratory syncytial virus

BACKGROUND

BD Veritor™ System for Rapid Detection of Respiratory Syncytial Virus (RSV) is a new-generation lateral flow immunochromatographic assay for objective detection of RSV in respiratory specimens from children.

OBJECTIVE

To evaluate the performance of BD Veritor™ System for Rapid Detection of RSV in respiratory specimens collected from pediatric patients.

STUDY DESIGN

A prospective, multicenter clinical trial was undertaken at five study sites representing geographically diverse regions of the U.S. to assess the performance of the BD Veritor™ System for Rapid Detection of RSV in comparison to R-mix shell vial culture and ProFlu+ reverse transcription-PCR assay (Gen-Probe/Prodesse).

RESULTS

440 nasopharyngeal washes/aspirates (NPW/A) and 706 nasopharyngeal swab (NPS) specimens from U.S. subjects<20 years of age were collected and tested using the BD Veritor™ System and compared with shell vial culture and real-time RT-PCR results. Analysis of the data indicates the overall sensitivity and specificity for BD Veritor™ System for all sample types combined was 90% and 97.0% versus shell vial culture and 75.5% and 98.7% versus RT-PCR respectively.

CONCLUSION

Overall, the BD Veritor™ System for the Rapid Detection of RSV performed well when compared to both viral cell culture and RT-PCR in children.

Viral agents causing lower respiratory tract infections in hospitalized children: evaluation of the Speed-Oligo® RSV assay for the detection of respiratory syncytial virus

Respiratory syncytial virus (RSV) is the viral agent which is more frequently involved in lower respiratory tract infections (LRTIs) in infants under 1 year of age in developed countries. A new oligochromatographic assay, Speed-Oligo® RSV, was designed and optimized for the specific detection and identification of RSV subtypes A and B. The test was evaluated in 289 clinical samples from 169 hospitalized children using an immunochromatography (IC) test, virus isolation by culture, and an in-house real-time polymerase chain reaction (RT-PCR). Other viruses causing LRTIs were investigated by cell culture or PCR-based tests. Sixty-two patients were infected by RSV (36.7%). In addition, adenovirus, influenza B, parainfluenza 2, and human metapneumovirus were detected in rates ranging from 5 to 8%. A proportion of 10.1% of the patients had mixed infections. The sensitivity, specificity, and positive and negative predictive values were, respectively, 94.9, 99.4, 98.9, and 97.4% for Speed-Oligo® RSV, 92.9, 96.3, 92.9, and 96.3% for RT-PCR/RSV, and 58.4, 98.1, 93.3, and 82.6% for IC. Our rates of viral detection and co-infection were similar to those of previously reported series. Finally, we find that Speed-Oligo® RSV is a rapid and easy-to-perform technique for the detection of RSV and the identification of subtypes A and B.

Selection and versatile application of virus-specific aptamers

Although the significance of molecular diagnostics in routine plant virus detection is rapidly growing, the preferred methods are still antibody-based enzyme immunoassays. In the past decade, aptamers have been demonstrated to be viable alternatives of antibodies in many applications. We set out to select apple stem pitting virus (ASPV)-specific aptamers and to apply them as antibody substitutes in various immunoassay methods. The applied systematic evolution of ligands by exponential enrichment (SELEX) procedure resulted in highly discriminative aptamers selectively binding to the target virus coat protein even in complex protein matrixes. We developed protocols for exploitation of aptamers in diverse plant virus diagnosis methods, such as dot and Western blot analyses and enzyme-linked oligonucleotide assay (ELONA). Our selected aptamers proved to be superior to the available antibody in all aspects. In contrast to the antibody, the aptamers decorate both native and denaturated proteins, and ELONA produces higher signal intensity than traditional enzyme-linked immunosorbent assay (ELISA) with virus-infected plant extract. Summarily, our results present the selection and practical utilization of first plant virus-specific aptamers. Most important, the first application of ELONA for virus detection is demonstrated, which proposes a novel, more flexible, and cost-effective means of virus diagnostics.

The limitations of point of care testing for pandemic influenza: what clinicians and public health professionals need to know

As the world prepares for the next influenza pandemic, governments have made significant funding commitments to vaccine development and antiviral stockpiling. While these are essential components to pandemic response, rapid and accurate diagnostic testing remains an often neglected cornerstone of pandemic influenza preparedness. Clinicians and Public Health Practitioners need to understand the benefits and drawbacks of different influenza tests in both seasonal and pandemic settings. Culture has been the traditional gold standard for influenza diagnosis but requires from 1-10 days to generate a positive result, compared to nucleic acid detection methods such as real time reverse transcriptase polymerase chain reaction (RT-PCR). Although the currently available rapid antigen detection kits can generate results in less than 30 minutes, their sensitivity is suboptimal and they are not recommended for the detection of novel influenza viruses. Until point-of-care (POC) tests are improved, PILPN recommends that the best option for pandemic influenza preparation is the enhancement of nucleic acid-based testing capabilities across Canada.

[Comparison study of a real-time reverse transcription polymerase chain reaction assay with an enzyme immunoassay and shell vial culture for influenza A and B virus detection in adult patients]

INTRODUCTION

The age of the patients and the type of sample are major problems in the diagnosis of influenza. Most available diagnostic techniques are highly effective in pediatric patients and in nasopharyngeal aspirates. However, in the adult population and using throat swabs, these techniques are much less reliable.

AIM

We performed a prospective study comparing the efficacy of a commercial real-time reverse transcription PCR assay (RT-PCR) with that of an enzyme immunoassay (EIA) or shell vial culture (SV) in the detection of influenza A and B viruses in 125 throat swabs from adults with clinically suspected influenza during the 2007-2008 flu season.

MATERIAL AND METHODS

Throat swabs were subjected to rapid antigen detection for influenza viruses by means of a commercial dot-blot EIA. For the RT-PCR technique, RNA was extracted from 200 microL of each sample by the automated extraction system, EZ1 virus minikit (version 2.0). Genomic amplification of the extracted viral RNA was carried out using the OneStep RT-PCR FluA+FluB automated system with the SmartCycler amplification system. Each sample was inoculated into 2 SV of the MDCK cell line. Turnaround times were calculated from the time specimens were received in the laboratory to the time the result was reported to clinicians.

RESULTS

The EIA system detected 27 (21.6%) positive samples, RT-PCR 62 (49.6%) positive samples, and SV 56 (44.8%) positive samples. Among the 62 positive samples, EIA detected 27 (43.5%), RT-PCR 62 (100%) and SV 56 (90.3%). With the use of RT-PCR, 38.4% of the adults studied were diagnosed on the same day samples were received. Among the total, 67.2% of diagnostic results were obtained within the first 24 hours; turnaround time was 1.1 days.

CONCLUSION

The real-time RT-PCR method studied displayed high sensitivity and specificity in the detection of influenza virus in adult patients, when compared with the conventional techniques. With real-time RT-PCR, large numbers of samples can be rapidly tested and results provided the same day samples are received.

[Diagnostic yield of paediatric respiratory samples in the Balearic Islands Sentinel Influenza Surveillance Network]

INTRODUCTION

Influenza disease is subjected to surveillance by national networks (RC) that predict the epidemic behaviour by reporting clinical and virological data.

OBJECTIVES

To evaluate the effectiveness of the paediatric respiratory samples in the Balearic Islands RC in the last five epidemic seasons.

MATERIAL AND PATIENTS

A breath sample was taken from paediatric patients in the RC who had flu symptoms. The samples were inoculated in the MDCK cell line. We reviewed the epidemiological data of patients with a culture positive to influenza A and B.

RESULTS

A total of 338 pharyngeal swabs from the RC were analysed during the study period. Of these, 65 (19.3%) belonged to <14 years old patients, and 44.6% of the samples were positive as opposed to 39.1% of adult respiratory samples. The influenza A virus was isolated in 24 paediatric samples (82.7%) and the influenza B virus in 5 (17.3%). The mean age of the paediatric patients of the RC who were positive was 8.5 years. Only 3 patients in the 0-4 year old group were positive (10.3%) and 26 patients (89.7%) in the 5-14 years old group.

CONCLUSIONS

In spite that paediatricians represented only 22% of the RC doctors and obtain the 19.3% of all respiratory samples, the percentage and effectiveness of these is higher that that obtained in the adult population.

Comparison of viral isolation and multiplex real-time reverse transcription-PCR for confirmation of respiratory syncytial virus and influenza virus detection by antigen immunoassays

We evaluated the Prodesse ProFlu-1 real-time reverse transcription-PCR multiplex assay with the SmartCycler instrument for the detection of human respiratory syncytial virus (RSV) and influenza A and B viruses in comparison to conventional cell culture and antigen immunoassays with the BD Directigen A+B and Binax NOW RSV assays over two successive respiratory virus seasons. Ninety-two percent of the 361 specimens tested were nasopharyngeal aspirates obtained from individual patients, of which 119 were positive for RSV and 59 were positive for influenza virus. The median age of the patients whose specimens were positive for RSV and influenza virus were 6.3 months and 42.4 years, respectively. The specificity of all of the methods tested was >or=99%, and the individual sensitivities of NOW RSV, RSV culture, Directigen A+B, influenza virus culture, and the Proflu-1 PCR for influenza/RSV were 82% (95% confidence interval [CI], 73 to 88), 57% (95% CI, 44 to 69), 59% (95% CI, 44 to 72), 54% (95% CI, 38 to 69), and 98% (95% CI, 93 to 100)/95% (95% CI, 85 to 99), respectively. In a clinical setting where viral isolation is performed to confirm rapid antigen immunoassay results for these common respiratory viruses, one-step real-time reverse transcriptase PCR testing can be a more sensitive and timely confirmatory method.

Cost-effectiveness of antiviral stockpiling and near-patient testing for potential influenza pandemic

A decision analytical model was developed to investigate the cost-effectiveness of stockpiling antiviral (AV) drugs for a potential influenza pandemic in the United Kingdom and the possible role of near-patient testing in conserving AV drug stocks. Under base-case assumptions (including a fixed stockpile that was smaller than the clinical attack rate), the treat-only option (treating all symptomatic patients with AV drugs) would be considered cost-effective ( pound1,900- pound13,700 per quality-adjusted life year [QALY] gained, depending on the fatality scenario), compared with no intervention (nonintervention but management of cases as they arise). The test-treat option (testing all symptomatic patients but treating those with positive tests results only) would result in moderate gains in QALYs over the treat-only option but at relatively large additional costs. Stockpiling sufficient AV drugs (but not near-patient tests) to treat all patients with clinical cases would be cost-effective, provided AV drugs are effective at preventing deaths from pandemic influenza.

Performance of Binax NOW Flu A and B and direct fluorescent assay in comparison with a composite of viral culture or reverse transcription polymerase chain reaction for detection of influenza infection during the 2006 to 2007 season

The Binax NOW Flu A and Flu B (Binax NOW), direct fluorescent assay (DFA), and viral culture were evaluated and compared with a composite of viral culture or reverse transcription polymerase chain reaction (RT-PCR). Participants with medically attended acute respiratory illness were identified through active surveillance during the 2006 to 2007 season, and consenting individuals (n=932) were tested for influenza by culture and RT-PCR. Physicians ordered a rapid antigen test (Binax NOW [n=73] or DFA [n=70]) according to their clinical judgment. The Binax NOW detected 11 of 18 influenza infections (sensitivity, 61%; 95% confidence interval [CI], 36-83%), whereas DFA detected 17 of 21 influenza infections (sensitivity 81%, 95% CI, 58-95%). Compared with culture/RT-PCR, specificity of both Binax NOW and DFA was 100%. During the 2006 to 2007 influenza season, DFA and Binax NOW demonstrated high specificity but failed to identify a substantial proportion of influenza infections.

[Respiratory viruses: old and new. Review of diagnostic methods]

Acute respiratory infections (ARI) of viral origin are one of the main causes of morbidity and mortality worldwide. In addition to traditional viruses, such as the influenza virus, respiratory syncytial virus, rhinovirus, parainfluenza viruses 1 to 4, and adenovirus, other viruses such as metapneumovirus, new coronaviruses (human coronavirus NL63 and HKU1 and severe acute respiratory syndrome [SARS]-coronavirus), and recently bocaviruses, have been identified as causal agents of ARI. Although most of these viral infections follow a benign and selflimiting course in healthy adults, the consequences for the health care systems increase when they involve children, the elderly, immunosuppressed individuals, or those with chronic underlying diseases. These viral infections are an important cause of hospitalization and death, mainly during the cold months of the year, and, from a social-health perspective, ARI are a drain on economic resources and a frequent cause of work absenteeism. Occasionally, some of these viruses may cause emergent world health problems, as has occurred with the influenza virus pandemic strain and SARScoronavirus. While classical diagnostic methods based on culture and antigen detection remain useful for traditional respiratory viruses, recently described viruses are diagnosed mainly by molecular amplification techniques.

Rapid method for detection of influenza a and B virus antigens by use of a two-photon excitation assay technique and dry-chemistry reagents

New separation-free assay methods for the rapid detection of influenza A and B virus antigens are presented. The methods employ dry-chemistry reagents and the recently developed two-photon excitation (TPX) fluorescence detection technology. According to the assay scheme, virus antigens are sandwiched by capture antibody onto polymer microspheres and fluorescently labeled antibody conjugate. Consequently, fluorescent immunocomplexes are formed on the surface of microspheres in proportion to the concentration of the analyte in the sample. The fluorescence signal from individual microspheres is measured, separation free, by means of two-photon excited fluorescence detection. In order to demonstrate the applicability of the new assay technique for virus antigen detection, methods for influenza A and B viruses were constructed. The assay method for influenza A virus applied a molecular fluorescent label, whereas the method for influenza B virus required a nanoparticle fluorescent reporter to reach sufficient clinical sensitivity. The new methods utilize a dry-chemistry approach, where all assay-specific reagents are dispensed into assay wells already in the manufacturing process of the test kits. The performance of the assay methods was tested with nasopharyngeal specimens using a time-resolved fluoroimmunoassay as a reference method. The results suggest that the new technique enables the rapid detection of influenza virus antigens with sensitivity and specificity comparable to that of the reference method. The dose-response curves showed linear responses with slopes equal to unity and dynamic assay ranges of 3 orders of magnitude. Applicability of the novel TPX technique for rapid multianalyte testing of respiratory infections is discussed.

Performance of Directigen flu A+B enzyme immunoassay and direct fluorescent assay for detection of influenza infection during the 2004-2005 season

Early diagnosis of influenza infection is needed to optimize the benefit of prescribing antiviral drugs. However, the accuracy of rapid tests is highly variable. This study evaluated the performance of Directigen flu A+B enzyme immunoassay (EIA) and direct fluorescent assay (DFA) during the 2004-2005 influenza season. Participants with medically attended acute respiratory illness were identified through an active surveillance. Consenting patients (n=818) were enrolled and cultured for influenza. Physicians ordered a rapid antigen test (EIA or DFA) according to their clinical judgment. Physicians ordered rapid tests with EIA (n=109), DFA (n=86), or both (n=9) in 204 patients with acute respiratory illness who were also cultured for influenza. The EIA detected 18 of 43 influenza infections (sensitivity, 42%; 95% confidence interval [CI], 28-57%), whereas DFA detected 26 of 38 influenza infections (sensitivity, 68%; 95% CI, 53-81%). Compared with culture, specificity of both EIA and DFA was 96%. During the 2004-2005 influenza season, both the EIA and DFA had low sensitivity and failed to detect influenza in many patients.

[Contribution of microbiological investigations to the diagnosis of lower respiratory tract infections]

The diagnosis of community-acquired pneumonia is usually based on clinical and radiological criteria. The identification of a causative organism is not required for the diagnosis. Although numerous microbiological techniques are available, their sensitivity and specificity are not high enough to guide first-line antimicrobial therapy. Consequently, this treatment remains most often empiric. If the causative organism is identified, the antimicrobial treatment is adapted. Sputum analysis may be proposed as a diagnostic tool for patients with an acute exacerbation of chronic obstructive pulmonary disease, in specific cases (prior antibiotherapy, hospitalization, failure of the empiric antimicrobial treatment).

C-reactive protein and leukocytes do not reliably indicate severity of influenza a infection in childhood

Influenza in children may mimic other infections leading to insufficient treatment. Determination of parameters that facilitate diagnosis and indicate severity would be useful to optimize treatment modalities. We prospectively screened 432 children for influenza infection. Forty-six children at the age of 4 weeks to 14 years (median, 18 months) with confirmed influenza A infection were analyzed. A clinical score of illness severity was calculated from the symptoms presented. To evaluate the dependency of the clinical score on C-reactive protein value, leukocyte count, age, and days of hospitalization, correlation and regression analyses were carried out. Neither the C-reactive protein values (median, 0.85 mg/dL; range, 0.2-18.6; r=0.14; p=0.35) nor the leukocyte counts (median, 7.95 G/L; range, 3.5-17.6; r=-0.14, p=0.34) correlated significantly with the clinical score of influenza severity. Thus, in daily clinical practice, C-reactive protein and leukocytes seem to be insufficient parameters to describe the clinical severity of influenza A infection in children.

Development and application of reference antisera against 15 hemagglutinin subtypes of influenza virus by DNA vaccination of chickens

Reference antisera were produced against 15 influenza hemagglutinin (HA) subtypes using DNA vaccination to produce a high-quality polyclonal serum to the HA protein without antibodies to other influenza viral proteins. The HA gene from each of 15 different HA subtypes of influenza virus was cloned into a eukaryotic expression vector and injected intramuscularly, together with a cationic lipid, into 3- to 4-week-old specific-pathogen-free chickens. Birds were boostered twice at 4-week intervals after the initial injection, and in general, antibody titers increased after each boost. The antisera were successfully applied in the hemagglutination inhibition test, which is the standard method for the classification of the HA subtypes of influenza virus. We also demonstrated the HA specificity of the antisera by Western blot and immunodot blot analysis. DNA vaccination also provides a safer alternative for the production of HA-specific antibodies, since it is produced without the use of live virus.

Rapid diagnosis of rabies in humans and animals by a dot blot enzyme immunoassay

OBJECTIVES

The presently advocated tests for rapid diagnosis of rabies, such as the fluorescent antibody test (FAT) are expensive and require expertise to carry out and interpret the results. In this study, a simple direct dot blot enzyme immunoassay (DIA) has been developed and evaluated to detect the rabies antigen in brain specimens of animals and humans. The utility of this test in the ante-mortem diagnosis of human rabies has also been evaluated.

METHODS

Brain homogenates of suspected rabid animals (n = 250), humans (n = 16) and clinical samples like saliva (n = 12) and cerebrospinal fluid (CSF) (n = 12) were directly spotted on polyvinylidene difluoride membrane (PVDF) and the absorbed rabies nucleoprotein antigen was detected using biotinylated antinucleoprotein antibody followed by treatment with streptavidin peroxidase conjugate and color development with diamino benzedine (DAB). Rabies-infected and normal mouse brain homogenates were used as positive and negative controls, respectively. The results of this test were evaluated with fluorescent antibody technique (for brain samples) and mouse inoculation test (for saliva and CSF samples).

RESULTS

A distinct dark brown color was seen in the positive control and all positive samples, while there was no color development with either the negative control or the negative samples. The concordance between the fluorescent antibody test (FAT) and dot immunoassay was 98.4% for brain samples, 83.3% for saliva and 91.6% for CSF samples. The specificity of the test was found to be 100%.

CONCLUSIONS

The dot blot enzyme immunoassay (DIA) test described here is a sensitive, specific and rapid test for the post-mortem diagnosis of rabies in animals and humans. The utility of this test for the ante-mortem diagnosis of rabies needs to be further evaluated.

Comparison of Binax NOW and Directigen for rapid detection of influenza A and B

Directigen Flu A + B and Binax NOW Flu A and Flu B tests detected 33 (55.9%) and 31 (52.5%) of 59 influenza-positive samples, respectively. In children under 2 years of age, sensitivity increased to 75% for both tests. Three samples tested falsely-positive for influenza B using Binax NOW.

Detection of influenza virus: traditional approaches and development of biosensors

Influenza is an acute respiratory disease caused by the influenza virus. The disease occurs annually, causing fatality in the elderly and children and billions of dollars loss in business and productivity. Traditional viral detection methods include MDCK cell culture, complement fixation, hemagglutinin-inhibition, and recently RT-PCR. Although effective, these methods generally involve labor-intensive laboratory procedures and often require trained personnel to carry them out. The development of biosensor technologies will enable rapid and specific disease diagnosis on-site so that a clinician can quickly determine whether treatment is needed. This paper reviews traditional viral assays and progress in the biosensor development for influenza virus. Recent advances in single-step direct detection using non-labeling techniques such as surface plasmon resonance, quartz-crystal microbalance, and colorimetric functional polymers are discussed.

Influenza Surveillance in Indonesia: 1999-2003

Although influenza is recognized for its worldwide importance, little is known about the disease from tropical countries like Indonesia. From August 1999 through January 2003, a surveillance study was conducted in clinics at 6 sentinel locations. Adults (age, >14 years) and children (age, 4-14 years) presenting with respiratory symptoms suggestive of influenza were asked to enroll in the study. Nasal and pharyngeal swabs were examined by virus isolation, polymerase chain reaction, and rapid immunochromatographic tests. A total of 3079 specimens were collected from 1544 participants. Influenza infection was confirmed in 172 volunteers (11.1%) presenting with influenza-like illness. Influenza A (H1N1 and H3N2) and B viruses were detected at all sites. Peak prevalence tended to coincide with the respective rainy seasons, regardless of location. In light of the recent epidemic of severe acute respiratory syndrome, continued influenza surveillance would be useful in strengthening the infrastructure of the Indonesian public health system.

Detection of influenza antigen with rapid antibody-based tests after intranasal influenza vaccination (FluMist)

Rapid tests for influenza antigen detection are frequently used, but it is not known how receipt of intranasal influenza vaccine affects results of these tests. We tested healthy adults who received either intranasal or intramuscular influenza vaccine. Of the 14 intranasal vaccine recipients, 7 (50%) had a direct fluorescent antibody test (DFA) result and 2 (14%) had an enzyme immunoassay (EIA) result that was positive for influenza antigen within 7 days after vaccination. No subjects had positive EIA results on day 12 or 13 after vaccination. For some intranasal vaccine recipients, rapid influenza-antigen detection tests yield positive results within 1 week after vaccination.

Microsphere-based duplexed immunoassay for influenza virus typing by flow cytometry

We have developed a rapid, duplexed microsphere-based immunoassay for the characterization of influenza virus types that has the potential to overcome many of the limitations of current detection methods. The assay uses microspheres of two sizes, each coupled to an influenza type A- or type B-specific monoclonal antibody (MAb), to capture influenza viruses in the sample. A cocktail of fluorescently labeled, influenza-specific polyclonal antibodies then binds the captured viruses. The sandwich complexes are measured using a multiparameter flow cytometer. The assay can distinguish between influenza types A and B in a single reaction with good reproducibility and high sensitivity. Detection sensitivity is much higher than that of commercially available influenza diagnosis quick kits: the FLU OIA (Thermo Biostar) kit and the Directigen Flu A+B kit (Becton Dickinson). The multiplexing capabilities of the current assay, which are not possible with enzyme-linked immunosorbent assay (ELISA) and the commercially available kits, reduce sample handling and consume fewer costly reagents. This assay represents a more efficient and sensitive method of characterizing influenza types. With inclusion of influenza subtype-specific antibodies as capture antibodies, this microsphere-based immunoassay can be expanded to differentiate among influenza types and subtypes in a single reaction to improve world-wide influenza surveillance.

Influenza

Although most influenza infections are self-limited, few other diseases exert such a huge toll of suffering and economic loss. Despite the importance of influenza, there had been, until recently, little advance in its control since amantadine was licensed almost 40 years ago. During the past decade, evidence has accrued on the protection afforded by inactivated vaccines and the safety and efficacy in children of live influenza-virus vaccines. There have been many new developments in vaccine technology. Moreover, work on viral neuraminidase has led to the licensing of potent selective antiviral drugs, and economic decision modelling provides further justification for annual vaccination and a framework for the use of neuraminidase inhibitors. Progress has also been made on developing near-patient testing for influenza that may assist individual diagnosis or the recognition of widespread virus circulation, and so optimise clinical management. Despite these advances, the occurrence of avian H5N1, H9N2, and H7N7 influenza in human beings and the rapid global spread of severe acute respiratory syndrome are reminders of our vulnerability to an emerging pandemic. The contrast between recent cases of H5N1 infection, associated with high mortality, and the typically mild, self-limiting nature of human infections with avian H7N7 and H9N2 influenza shows the gaps in our understanding of molecular correlates of pathogenicity and underlines the need for continuing international research into pandemic influenza. Improvements in animal and human surveillance, new approaches to vaccination, and increasing use of vaccines and antiviral drugs to combat annual influenza outbreaks are essential to reduce the global toll of pandemic and interpandemic influenza.

Comparison of SmartCycler real-time reverse transcription-PCR assay in a public health laboratory with direct immunofluorescence and cell culture assays in a medical center for detection of influenza A virus

A single-tube real-time (fluorogenic) reverse transcription (RT)-PCR with the SmartCycler instrument (SmartCycler RT-PCR) for influenza A virus detection was evaluated with 238 respiratory specimens. Direct immunofluorescence antibody staining (DFA) and primary rhesus monkey kidney cell culture were performed on-site at Yale-New Haven Hospital. Specimens were transported to the Connecticut Department of Public Health Laboratory for real-time RT-PCR. Cell culture detected influenza A virus in all 150 influenza A virus-positive specimens, DFA detected the virus in 148 influenza A virus-positive specimens, and SmartCycler RT-PCR detected the virus 143 influenza A virus-positive specimens. The sensitivity and specificity of RT-PCR were 95.3 and 100%, respectively. The high sensitivity and specificity and the rapid turnaround time made the SmartCycler RT-PCR valuable for the rapid diagnosis of influenza A, especially in a public health laboratory. The closed real-time RT-PCR system avoided cross-contamination possible with RT-PCR and the excessive manipulations required for conventional RT-PCR analysis and saved time and labor as well. In a medical center, rapid diagnosis by DFA was labor intensive but was 98.7% sensitive and 100% specific compared to the results of culture and provided results within 2 h throughout operating hours, helping with bed allocation on admission and patient management.

Comparison of the Denka-Seiken INFLU A.B-Quick and BD Directigen Flu A+B kits with direct fluorescent-antibody staining and shell vial culture methods for rapid detection of influenza viruses

The INFLU A.B-Quick and Directigen Flu A+B enzyme immunoassays were compared with direct immunofluorescence and cell culture for detection of influenza A and B viruses in a total of 255 patient specimens. Both assays identified 23 of 42 influenza A viruses (sensitivity, 54.8%; specificity, 100%; positive predictive value [PPV], 100%; negative predictive value [NPV], 91.8%). The INFLU A.B-Quick assay identified 10 of 16 influenza B viruses (sensitivity, 62.5%; specificity, 99.6%; PPV, 90.9%; NPV, 97.5%), and the Directigen Flu A+B assay detected 9 of 16 influenza B viruses (sensitivity, 56.3%; specificity, 99.6%; PPV, 90%; NPV, 97.1%).

Influenza diagnosis and treatment in children: a review of studies on clinically useful tests and antiviral treatment for influenza

BACKGROUND

Prompt testing for influenza can help guide clinical management of patients with suspected influenza. Three antiviral medications, amantadine, oseltamivir and zanamivir, are approved for treatment of influenza in children. Rimantadine and ribavirin have also been used.

OBJECTIVES

To review the published evidence on clinically useful diagnostic tests and antiviral treatment for influenza virus infections in children.

METHODS

Studies published from 1966 through September 2002 were reviewed on clinical diagnosis, immunofluorescence and rapid influenza tests and on antiviral treatment of influenza virus infections among pediatric populations.

RESULTS

No studies assessed the accuracy of clinical diagnosis of influenza in children compared with viral culture. Compared with viral culture, direct immunofluorescence antibody and indirect immunofluorescence antibody tests for influenza had fair to moderate median sensitivities and high median specificities, whereas rapid influenza diagnostic tests had moderate median sensitivities and moderately high median specificities. No randomized, placebo-controlled studies were found of amantadine or rimantadine for treatment of influenza A. In a few separate controlled studies, oseltamivir, zanamivir and ribavirin each reduced symptom duration of influenza compared with placebo.

CONCLUSIONS

Additional data are needed about the accuracy of clinical diagnosis of influenza in children. Although direct immunofluorescence antibody staining, indirect immunofluorescence antibody staining and rapid tests are moderately to reasonably accurate in detecting influenza virus infections in children, physicians should use clinical judgment and local surveillance data about circulating influenza viruses when interpreting test results. Further controlled studies of the efficacy, adverse effects and emergence of antiviral resistance during treatment of influenza are needed for all of the antiviral drugs.