Evaluation of a new point-of-care test for influenza A and B virus in travellers with influenza-like symptoms

Point-of-care (POC) tests for influenza facilitate clinical case management, and might also be helpful in the care of travellers who are at special risk for influenza infection. To evaluate influenza POC testing in travellers, a new assay, the ImmunoCard STAT! Flu A and B, was used to investigate travellers presenting with influenza-like symptoms. Influenza virus infection was diagnosed in 27 (13%) of 203 patients by influenza virus-specific PCR and viral culture. The POC test had sensitivity and specificity values of 64% and 99% for influenza A, and 67% and 100% for influenza B, respectively. Combined sensitivity and specificity were 67% and 99%, respectively, yielding positive and negative predictive values of 95%, and positive and negative likelihood ratios of 117 and 0.34, respectively. The convenient application, excellent specificity and high positive likelihood ratio of the POC test allowed rapid identification of influenza cases. However, negative test results might require confirmation by other methods because of limitations in sensitivity. Overall, influenza POC testing appeared to be a useful tool for the management of travellers with influenza-like symptoms.

Reassortment between human A(H3N2) viruses is an important evolutionary mechanism

Phylogenetic relationships of whole genomes of H3N2 viruses circulating in Germany during a 6-year period from 1998 to 2005 revealed the co-circulation of different lineages of viruses. Multiple reassortment events occurred during this time between viruses belonging to different lineages or different subgroups. Strains isolated during 1998-1999 were characterised by a surprisingly high heterogeneity and multiple reassortment events. Seventy percent of the examined 1998-1999 viruses had completely different genome compositions. To our knowledge, such an exceptional high proportion of different reassortant strains, encompassing all eight genome segments, have not been described before. In contrast, only one reassortant virus was prevalent during 1999-2000 even though two of the three 1998-1999 lineages were co-circulating. Reassortant viruses were isolated also in each of the other seasons. However, the proportion of H3N2 viruses with different genome compositions varied from season to season. Strains with a reassortant NA played an important role and were also detected during 2003-2004 and 2004-2005 accounting for 45% and 70% of the circulating H3N2 viruses, respectively. Moreover, different reassortment events occurring during these seasons included also the PB1, PB2 and NP genes. The results presented here emphasize that genetic reassortment is an important factor in the evolution of H3N2 viruses and highlight the need for a comprehensive analysis of influenza viruses, especially with regard to the annual vaccine composition.

Zur Schätzung der Schutzwirkung der Influenzaimpfung aus Surveillancedaten

The continuous antigenic drift of influenza viruses requires annual adaptation of the vaccine. Protection depends largely on the match of the variants represented in the vaccine with the viruses actually known to be in circulation and may differ considerably from season to season. Therefore studies to assess the efficacy and effectiveness of the vaccine are conducted rather sporadically on an annual basis and it would be desirable to make use of routinely available data from surveillance programs. We compared two different approaches: (1) the "screening method" where cases are identified from laboratory data and controls are taken from data on vaccination rates and (2) a second method that uses the same cases, but controls were influenza-negative individuals with influenza-like illness (also identified from laboratory data). The sensitivity of the methods to confounders that were considered as relevant was tested with a simulation. Both methods were applied to the data of the German influenza surveillance data of the season 2004/2005. The estimated effectiveness over all age groups was rather low with both methods, but comparable with other estimations from the literature. We observed differences in certain age groups between the methods as well as large differences between particular age groups within one method. Possible explanations are random variations due to low numbers in age strata and other influences not yet considered. Therefore the estimations should be interpreted with care; however, relative comparisons among seasons may still be meaningful.

A new European perspective of influenza pandemic planning with a particular focus on the role of mammalian cell culture vaccines

Sixteen EU scientists and doctors were interviewed about pandemic planning using psychometric methods applied to a scientific problem for the first time. Criticism was aimed at countries which have no plan whatsoever, the majority of nations. Many such countries have not invested in scientific infrastructure and public health. Amongst the 15 or so published pandemic plans a lack of detail was identified. Of particular need was investment into avian virus vaccine stocks (H1-15), prepared licenses of vaccine and pre purchase and agreed distribution, investment into stocks of antivirals, antibiotics and masks. Most but not all members of the group predicted a global outbreak within 5 years, most probably starting in SE Asia. However it was recognised that a pandemic could start anywhere in the world which had juxtaposition of young people, chickens, ducks and pigs. Mammalian cell culture production using wild type virus with the production factory at category III levels of security was exemplified. Antivirals would be essential to ameliorate the first wave of infection although significant quantities of cell grown vaccine could be produced if, as in 1918, 1957 and 1968 there is a long period between the first virus isolation and person to person spread. The wider scientific community is more energised than previously for very serious preparations to be in place way before the outbreak begins as this is a major public health problem, completely dwarfing concerns about bioterrorism.

Impact of corticosteroids on the immune response to a MF59-adjuvanted influenza vaccine in elderly COPD-patients

The influence of steroids on the antibody response to a MF59-adjuvanted influenza vaccine in elderly COPD patients has not been studied previously. In the influenza season 2001/02 (October-February) elderly COPD patients were recruited at 14 doctor's offices and our 250-bed hospital. Patients were stratified into three groups according to current treatment regimen: (a) > 10 mg of prednisolone/day (SS); (b) inhaled steroids (IS); (c) no steroid treatment (control group, CG). All patients were vaccinated with the MF59-adjuvanted influenza vaccine. Antibodies against the influenza strains A/H1N1, A/H3N2, and B were measured at baseline, 4 and 24 weeks after vaccination by hemagglutination inhibition (HI) assay. One-hundred and sixty-two patients completed the study (CG n = 42; IS n = 87; SS n = 33). Mean age was 71.3 years (range 60-89). Twenty-one percent of all patients reported local reactions; no serious adverse events were observed. Four weeks after vaccination, mean geometric HI titres (GMT) for A/H1N1, A/H3N and B increased significantly in all groups (p < or = 0.05). After 24 weeks, GMTs to A/H1N1 and A/H3N2 returned to baseline, while GMTs to type B remained significantly higher than baseline in all groups. Significant differences between the groups as regards GMTs, seroconversion (56-89%) or seroprotection rates (64-93%) were not observed. Systemic steroids did not influence the antibody response towards the MF59-adjuvanted influenza vaccine. We found that the strains included in the vaccine showed varying long-term immunogenicity.

Dysmyelination in the brain of adolescents and young adults with maple syrup urine disease

Maple syrup urine disease (MSUD) is associated with increased branched-chain amino acids (BCAA), their keto acids (BCKA), and acute or chronic encephalopathy. Aim of treatment is to reduce BCAA and BCKA to prevent or minimize brain dysfunction. We investigated 14 juvenile and adult patients with MSUD by means of cerebral magnetic resonance imaging (MRI) and correlated MRI changes to biochemical control measured as median plasma BCAA concentrations over 6-36 months prior to investigation. Abnormalities consisted of an increased signal in the white matter on T2-weighted images which is compatible with a disturbed water content of the white matter and dysmyelination. Areas affected most commonly were mesencephalon, brain stem, thalamus and globus pallidus; supratentorial lesions seem to be restricted to severe cases. No patient with white matter changes had acute neurological/encephalopathic symptoms indicating that the severity of dysmyelination does not correlate to acute neurotoxicity.

Antigenic drift and variability of influenza viruses

Annual influenza epidemics are caused by rapid evolution of the viral genome. Continuous and extensive antigenic variation has been shown for hemagglutinin (HA), the principal immunizing antigen of the virus. Monitoring of the antigenicity of circulating influenza viruses is necessary for selection of the most suitable vaccine strains. In this study, characterization of influenza A/H3N2 and influenza B viruses recently circulating in Germany was performed by molecular and antigenic analysis. Sequencing and phylogenetic analysis of the HA1 gene revealed that two distinct groups of H3N2 viruses co-circulated during 1997/1998. The majority of isolates clustered with the new drift variant A/Sydney/5/97, as was also shown by antigenic characterization. A noteworthy genetic drift of H3N2 viruses was evident during the winter 1998/1999. However, serological characterization using hemagglutinin inhibition tests did not result in detection of viruses belonging to different groups as confirmed by molecular analysis. Influenza B viruses isolated during 1996/1997 were antigenically closely related to the prototype vaccine strains B/Beijing/184/93 or B/Harbin/7/94. Molecular analysis demonstrated that our German 1996/1997 isolates differed by nine amino acids from B/Harbin/7/94 and represented a group of viruses that was completely different from the Harbin strain. Retrospective studies revealed the circulation of B/Yamanshi/166/98-like viruses in Germany already during the 1996/1997 season. Our results suggest that molecular analysis of the HA gene is important to complement the antigenic characterization for a better selection of appropriate vaccine strains.

Enhancing the predictive value of throat swabs in virological influenza surveillance

According to a national survey in Germany, the influenza virological surveillance can be improved when sentinel practitioners take throat swabs specimens only from patients who consult early after the disease onset (ie, within 48 hours), and when they use the strict clinical case definition of influenza-like illness. PCR should be used for primary detection of influenza viruses.

Application of a fluorogenic PCR assay for typing and subtyping of influenza viruses in respiratory samples

A fluorogenic PCR-based method (TaqMan-PCR) was developed for typing and subtyping of influenza virus genomes in clinical specimens. The TaqMan-PCR employs a probe technology that exploits the endogenous 5'-3' nuclease activity of the Taq DNA polymerase to allow direct detection of the amplicon by release of a fluorescent reporter during the PCR. Therefore, post-PCR analysis is avoided since hybridization with the fluorogenic probe and quantification of the amplified product is performed simultaneously during PCR cycling. The specificity of the method was evaluated on 86 influenza A (25 H1N1 and 61 H3N2) and 49 influenza B virus reference strains and isolates. The sensitivity of the technique was found to be at the level of 0.1 50% tissue culture infective dose. This TaqMan-PCR was applied prospectively to surveillance work by community-based sampling in Germany during the last two influenza seasons. Seven hundred five throat swabs were analyzed during the winter of 1997-1998. A total of 195 of 705 samples (28%) were positive by PCR. Influenza viruses could be isolated from 125 specimens (18%). During the 1998-1999 season, 1,840 respiratory samples were received. Influenza viruses were isolated from 281 specimens (15%) out of 525 throat swabs (29%) which were positive for influenza A or B virus by TaqMan-PCR. Further differentiation of influenza A virus-positive swabs revealed an intensive circulation of the subtype H3N2 during both seasons, 1997-1998 and 1998-1999. The TaqMan-PCR was much more sensitive than culture and revealed an excellent correlation for typing and subtyping of influenza viruses when samples were positive by both methods.

Calcium transport from mineral waters across caco-2 cells

In the present study the absorption of calcium from 13 different mineral waters has been examined. For this purpose the mineral waters were first digested in vitro by simulating gastric and intestinal digestion. Afterward, the absolute and fractional transport rates of calcium from these digested solutions across human colon adenocarcinoma (Caco-2) cell monolayers grown on bicameral filters were measured. Results showed that the fractional transport rates for calcium lie between 1.65 and 6.72% after 90 min of incubation time. The absolute transport values varied between 90.4 and 624.7 pmol/(min x cm(2)). The transport values [pmol/(min x cm(2))] for calcium from the mineral waters were in general not concentration dependent, showing neither signs of saturation kinetics nor unsaturable uptake mechanisms. In addition, the fractional transport rates from mineral waters with similar calcium concentrations were greatly different in some cases. On the basis of these results, it can be concluded that calcium bioavailability from mineral waters could vary dependent on probably several factors.

Influenza A outbreak among adolescents in a ski hostel

An outbreak of influenza A H3N2 with a high attack rate (49%) and abrupt onset (69% became ill within 2 days) occurred among 81 ski school participants who stayed in a crowded hostel in Austria in early 1997. Two students were hospitalized with pneumonia; one of them died. Cultures of blood and/or respiratory secretions from the hospitalized students yielded toxin-producing Staphylococcus aureus. Influenza A H3N2 was confirmed serologically in four participants, including one surviving hospitalized student, and by polymerase chain reaction of lung tissue from the deceased student. This investigation demonstrates that influenza can cause an explosive outbreak among skiers in a crowded hostel, leading to severe complications among previously healthy adolescents.

A multicentre quality assessment study to monitor the performance of HIV-1 PCR

Eleven German laboratories and one Swiss laboratory initiated a quality assessment study to evaluate the specificity and sensitivity of their polymerase chain reaction (PCR) for detection of HIV-1 DNA. Following its own PCR protocols, each laboratory tested a panel of ten coded samples consisting of cell pellets containing 0, 0.1, 1, 10, 10(2), 10(3) and 10(4) ACH-2 cells per 1.5 x 10(5) uninfected peripheral blood mononuclear cells. Of the twelve participating laboratories, three reported correct results for the dilution series as well as for uninfected specimens. One or more classification errors were recorded for 12% of the samples for which the diagnosis was expected to be positive or negative. Samples containing 10 copies of the target template were correctly reported by eleven of the twelve participants. The average sensitivity was 97%. The results of the study revealed no significant differences between the Amplicor kit and in-house procedures. Most of the classification errors occurred in specimens from HIV-negative samples. Out of 36 negative samples, 5 were reported false positive, showing that contamination remains a problem for some laboratories, regardless of the PCR test performed. Careful laboratory techniques and internal as well as external quality control procedures will help avoiding carryover contamination.

Rapid detection of influenza A neuraminidase subtypes by cDNA amplification coupled to a simple DNA enzyme immunoassay

A newly developed colorimetric method, DNA enzyme immunoassay (DEIA), was applied to the detection of neuraminidase subtypes N1 and N2 of influenza A viruses. Reverse transcription and polymerase chain reaction with universal primers were used for genomic amplification of H1N1, H2N2, and H3N2 strains. Following amplification, an aliquot of the PCR product was hybridized to biotinylated DNA sequences (N1/N2 probes) immobilized on microtiter wells. The hybridization event was revealed by monoclonal antibodies to double stranded DNA in a standard ELISA reaction. The assay described here was able to distinguish accurately between the two neuraminidase subtypes of human influenza A viruses. It is a simple and rapid method facilitating the handling of a large number of samples and therefore seems to be easily applicable to diagnostic laboratories.

Rapid detection of tick-borne encephalitis virus sequences by cDNA amplification coupled to a simple DNA enzyme immunoassay

BACKGROUND

The tick-borne encephalitis virus (TBEV) causes many cases of severe neurological disease in Europe and Asia. Rapid and virus specific laboratory tests are needed for epidemiological studies and for diagnosis of human diseases.

OBJECTIVES

A newly developed colorimetric method, DNA enzyme immunoassay (DEIA), was applied to the detection of TBEV-specific sequences.

STUDY DESIGN

Reverse transcription and polymerase chain reaction (PRC) were used for g genomic amplification. The specificity of PCR products was confirmed using an internal biotinylated probe from the 5'-NCR immobilized on streptavidin coated microtiter wells. The hybridization event was revealed by monoclonal antibodies to double stranded DNA in a standard ELISA reaction.

RESULTS

A total of 23 TBEV strains among them prototype strains and isolates from Germany and other European countries was investigated. In all cases hybridization with the internal probe has occurred.

CONCLUSION

The DEIA described here is a simple and rapid method facilitating the handling of a large number of samples and therefore seems to be especially valuable to surveillance studies of endemic areas and for diagnosis of human diseases.

Differentiation of vaccine and wild-type polioviruses using polymerase chain reaction and restriction enzyme analysis

Genomic amplification followed by selective digestion of restriction enzymes was used to differentiate polioviruses. The method was based on conserved and variable components of the 5'-noncoding region. The differences between Sabin vaccine and wild-type viruses made it possible to identify rapidly an isolated poliovirus as vaccine-related or wild-type virus. A total of 60 isolates and strains were tested and all of them were correctly identified. This method is recommended as a sensitive, specific and rapid way to differentiate polioviruses in clinical isolates and environmental samples.

Cloning of higher plant omega-3 fatty acid desaturases

Arabidopsis thaliana T-DNA transformants were screened for mutations affecting seed fatty acid composition. A mutant line was found with reduced levels of linolenic acid (18:3) due to a T-DNA insertion. Genomic DNA flanking the T-DNA insertion was used to obtain an Arabidopsis cDNA that encodes a polypeptide identified as a microsomal omega-3 fatty acid desaturase by its complementation of the mutation. Analysis of lipid content in transgenic tissues demonstrated that this enzyme is limiting for 18:3 production in Arabidopsis seeds and carrot hairy roots. This cDNA was used to isolate a related Arabidopsis cDNA, whose mRNA is accumulated to a much higher level in leaf tissue relative to root tissue. This related cDNA encodes a protein that is a homolog of the microsomal desaturase but has an N-terminal extension deduced to be a transit peptide, and its gene maps to a position consistent with that of the Arabidopsis fad D locus, which controls plastid omega-3 desaturation. These Arabidopsis cDNAs were used as hybridization probes to isolate cDNAs encoding homologous proteins from developing seeds of soybean and rapeseed. The high degree of sequence similarity between these sequences suggests that the omega-3 desaturases use a common enzyme mechanism.

Functional and structural analysis of the ribonucleoprotein complexes of different human influenza virus strains

Ribonucleoprotein (RNP) cores were prepared from various strains of human influenza virus by treating the purified or spikeless virus particles with non-ionic detergents such as Nonidet P-40 and centrifugation in continuous linear glycerol gradients. In addition to RNA, the purified complexes contained viral nucleoprotein (NP) and the three P proteins (PA, PB1, PB2) as determined by polyacrylamide gel electrophoresis (PAGE) under denaturing conditions. Contaminations with other viral polypeptides, especially HA1, HA2 and M were below 1%. All RNP complexes were transcriptionally active in vitro. Comparison of the polymerase activity of purified complexes revealed considerable differences depending not only on the content of polymerase proteins. The activity of RNP complexes was enhanced for all strains tested by adding of ApG.