Rapid detection of respiratory syncytial virus and influenza A virus in cell cultures by immunoperoxidase staining with monoclonal antibodies

Comparison of infectious influenza A virus quantification methods employing immuno-staining

Infections caused by highly variable influenza A viruses (IAVs) pose perpetual threat to humans as well as to animals. Their surveillance requires reliable methods for their qualitative and quantitative analysis. The most frequently utilized quantification method is the titration by plaque assay or 50% tissue culture infectious dose estimation by TCID₅₀. However, both methods are time-consuming. Moreover, some IAV strains form hardly visible plaques, and the evaluation of TCID₅₀ is subjective. Employment of immuno-staining into the classic protocols for plaque assay or TCID₅₀ assay enables to avoid these problems and moreover, shorten the time needed for reliable infectious virus quantification. Results obtained by these two alternatives of classic virus titration methods were compared to the newer rapid culture assay (RCA), where titration endpoint of infectious virus was estimated microscopically based on the immuno-staining of infected cells. In our analysis of compared methods, five different IAV strains of H1, H3 and H5 subtypes were used and results were statistically evaluated. We conclude that the RCA proved to be at least as reliable in assessment of infectious viral titer as plaque assay and TCID₅₀, considering the employed immuno-staining.

Development of an Immunoperoxidase Monolayer Assay for the Detection of Antibodies against Peste des Petits Ruminants Virus Based on BHK-21 Cell Line Stably Expressing the Goat Signaling Lymphocyte Activation Molecule

From 2013 to 2015, peste des petits ruminants (PPR) broke out in more than half of the provinces of China; thus, the application and development of diagnostic methods are very important for the control of PPR. Here, an immunoperoxidase monolayer assay (IPMA) was developed to detect antibodies against PPR. However, during IPMA development, we found that Vero cells were not the appropriate choice because staining results were not easily observed. Therefore, we first established a baby hamster kidney-goat signaling lymphocyte activation molecule (BHK-SLAM) cell line that could stably express goat SLAM for at least 20 generations. Compared with Vero cells, the PPR-mediated cytopathic effect occurred earlier in BHK-SLAM cells, and large syncytia appeared after virus infection. Based on this cell line and recombinant PPR virus expressing the green fluorescent protein (GFP) (rPPRV-GFP), an IPMA for PPR diagnosis was developed. One hundred and ninety-eight PPR serum samples from goats or sheep were tested by the IPMA and virus neutralization test (VNT). Compared with the VNT, the sensitivity and specificity of the IPMA were 91% and 100%, respectively, and the coincidence rate of the two methods was 95.5%. The IPMA assay could be completed in 4 h, compared with more than 6 d for the VNT using rPPRV-GFP, and it is easily performed, as the staining results can be observed under a microscope. Additionally, unlike the VNT, the IPMA does not require antigen purification, which will reduce its cost. In conclusion, the established IPMA will be an alternative method that replaces the VNT for detecting antibodies against PPRV in the field.

Clinical and socioeconomic impact of moderate-to-severe versus mild influenza in children

Some studies have assessed the efficacy of influenza vaccination in children separately for moderate-to-severe and any influenza, but the definition used for identifying children with moderate-to-severe illness has not been validated. We analyzed clinical and socioeconomic data from two prospective cohort studies of respiratory infections among children aged ≤13 years (four influenza seasons, 3,416 child-seasons of follow-up). We categorized children with laboratory-confirmed influenza into two mutually exclusive groups of moderate-to-severe and mild influenza using the previously proposed criteria. We obtained the data for the analyses from structured medical records filled out by the study physicians and from daily symptom cards filled out by the parents. Of 434 cases of influenza, 217 (50 %) were classified as moderate-to-severe and 217 (50 %) as mild. The mean duration of fever was 4.0 days in children with moderate-to-severe influenza and 3.1 days in those with milder illness (P < 0.0001). Antibiotics were prescribed to 111 (51 %) children with moderate-to-severe and to ten (5 %) children with mild influenza (P < 0.0001). The rates of parental work absenteeism were 184 days per 100 children with moderate-to-severe influenza and 135 days per 100 children with mild influenza (P = 0.02). The corresponding rates of children's own absenteeism from day care or school were 297 and 233 days respectively per 100 children (P = 0.006). Categorization of children into groups with moderate-to-severe and mild influenza is meaningful, and it identifies children in whom the clinical and socioeconomic impact of influenza is highest. Illness severity should be considered when assessing influenza vaccine effectiveness in children.

Comparative Burden of Influenza A/H1N1, A/H3N2 and B Infections in Children Treated as Outpatients

BACKGROUND

Few studies have directly compared the clinical impact of different types and subtypes of influenza viruses in children.

METHODS

In a prospective study of respiratory infections in preenrolled cohorts of children ≤13 years of age, we compared the clinical features and the overall burden of illness between outpatient children with A/H1N1, A/H3N2 and B infections. The data were derived from structured medical records filled out by study physicians and from daily symptom diaries filled out by the parents throughout the follow-up period.

RESULTS

Of 358 children included in the analyses, 203 (57%) had influenza A/H1N1, 96 (27%) had A/H3N2, and 59 (16%) had influenza B infection. Children with influenza A/H3N2 were significantly younger (median, 3.2 years) than those with A/H1N1 (median, 4.8 years) or B (median, 5.1 years) infections (P < 0.0001). When adjusted for age, children 3-6 years of age with A/H3N2 infection had a higher frequency of fever ≥39.0°C (67% vs. 38%; P = 0.002), longer duration of fever (median, 4 vs. 3 days; P = 0.02) and more antibiotic treatments (43% vs. 20%; P = 0.004) than did children with A/H1N1 infections. Overall, the clinical presentation, duration of illness, frequency of complications, children's absenteeism from day care or school and parental work absenteeism were comparable between children with A/H1N1, A/H3N2 and B infections.

CONCLUSIONS

Adjusted for age, the clinical manifestations and the burden of illness are largely comparable between children with influenza A/H1N1, A/H3N2 and B infections.

Signs and symptoms predicting influenza in children: a matched case-control analysis of prospectively collected clinical data

We aimed to determine whether there are signs or symptoms that could help clinicians to distinguish between influenza and other respiratory infections. The clinical data for this matched case-control analysis were derived from a 2-year prospective cohort study of respiratory infections among children aged≤13 years. At any signs of respiratory infection, the children were examined and nasal swabs were obtained for virologic analyses. Cases were 353 children with laboratory-confirmed influenza and controls were 353 children with respiratory symptoms who tested negative for influenza. Cases and controls were matched for gender, age, and timing of the visit. In the multivariate conditional logistic regression analyses, fever was the only sign that independently predicted influenza virus infection, with odds ratios ranging from 13.55 (95% confidence interval [CI], 6.90-26.63) to 50.10 (95% CI, 16.25-154.45), depending on the degree of fever. In all analyses, the predictive capability of fever increased with incremental elevations in the child's temperature. The likelihood ratio of fever≥40.0°C in predicting influenza was 6.00 (95% CI, 2.80-12.96). Among unselected children seen as outpatients during influenza outbreaks, fever is the only reliable predictor of influenza virus infection. The optimal use of influenza-specific antiviral drugs in children may require virologic confirmation.

Effectiveness of inactivated influenza vaccine in children aged 9 months to 3 years: an observational cohort study

BACKGROUND

Few prospectively collected data are available to support the effectiveness of inactivated influenza vaccines in children younger than 2 years. We aimed to establish the effectiveness of trivalent inactivated influenza vaccine against laboratory-confirmed influenza A and B infections in a cohort of children younger than 3 years.

METHODS

In a prospective cohort study during the influenza season of 2007-08 in Turku, Finland, between Jan 14 and April 9, 2008, we assessed the effectiveness of trivalent inactivated influenza vaccine against laboratory-confirmed influenza A and B infections in children aged 9 months to 3 years. Our study was part of a clinical trial on antiviral treatment of influenza in children (ClinicalTrials.gov, number NCT00593502). The vaccine was given as part of the Finnish vaccination programme as a 0·5 mL injection. Children enrolled into our study through mailed announcements and local advertisements were examined every time they had fever or signs of respiratory infection. No exclusion criteria were used for enrolment. Influenza was diagnosed with viral culture, antigen detection, and RT-PCR assays of nasal swab specimens. Vaccination status of children was determined by parental report. We calculated the primary effectiveness of influenza vaccination by comparing the proportions of infections in fully vaccinated and unvaccinated children in the follow-up cohort.

FINDINGS

We enrolled 631 children into our study with a mean age of 2·13 years (range 9-40 months). Seven (5%) of 154 fully vaccinated children and 61 (13%) of 456 unvaccinated children contracted influenza during the study (effectiveness 66%, 95% CI 29-84; p=0·003). In the subgroup of children younger than 2 years, four (4%) of 96 fully vaccinated children and 21 (12%) of 172 unvaccinated children contracted influenza (66%, 9-88, p=0·03). We were unable to record any adverse events associated with the vaccination of the children in our study.

INTERPRETATION

Trivalent inactivated influenza vaccine was effective in preventing influenza in young children, including those younger than 2 years. Our findings suggest that influenza vaccine recommendations should be reassessed in most countries.

FUNDING

F Hoffmann-La Roche Ltd.

Clinical presentation of influenza in unselected children treated as outpatients

BACKGROUND

Influenza causes a great disease burden on children especially in the outpatient setting. The signs and symptoms of influenza in unselected children treated as outpatients have not been previously published.

METHODS

We assessed the clinical presentation of influenza in a prospective study of respiratory infections in preenrolled cohorts of children < or =13 years of age during 2 consecutive respiratory seasons (2231 child-seasons of follow-up). We examined the children and obtained a nasal swab for the detection of influenza during every episode of illness, regardless of the presence or absence of fever or the severity of the symptoms.

RESULTS

Influenza was virologically confirmed in 372 children, of whom 353 (95%) providing complete data on the signs and symptoms were included in the analyses. A total of 95% of these children were febrile, and 50% had fever > or =39.0 degrees C. Among children <3 years of age, 20% had fever > or =40.0 degrees C. Seventy-seven percent of the children had cough and 78% had rhinitis. In children 7 to 13 years of age, only 39% had headache and 13% had myalgia.

CONCLUSIONS

High fever is a prominent sign of influenza in children, and the clinical presentation of influenza is most severe in children <3 years of age. Headache and myalgia are not typical features of influenza in outpatient children. Most children with influenza have rhinitis during the early phase of the illness, which makes the clinical diagnosis of influenza difficult especially in the youngest children.

Challenge of conducting a placebo-controlled randomized efficacy study for influenza vaccine in a season with low attack rate and a mismatched vaccine B strain: a concrete example

Background

Our aim was to determine the efficacy of a trivalent inactivated split virus influenza vaccine (TIV) against culture-confirmed influenza A and/or B in adults 18 to 64 years of age during the 2005/2006 season in the Czech Republic.

Methods

6203 subjects were randomized to receive TIV (N = 4137) or placebo (N = 2066). The sample size was based on an assumed attack rate of 4% which provided 90% power to reject the hypothesis that vaccine efficacy (VE) was ≥ 45%. Cases of influenza like illness (defined as fever (oral temperature ≥37.8°C) plus cough and/or sore throat) were identified both by active (biweekly phone contact) and passive (self reporting) surveillance and nasal and throat swabs were collected from subjects for viral culture.

Results

TIV was well tolerated and induced a good immune response. The 2005/2006 influenza season was exceptionally mild in the study area, as it was throughout Europe, and only 46 culture-confirmed cases were found in the study cohort (10 influenza A and 36 influenza B). Furthermore among the B isolates, 35 were identified as B/Hong Kong 330/2001-like (B/Victoria/2/87 lineage) which is antigenically unrelated to the vaccine B strain (B/Yamagata/16/88 lineage). The attack rate in the vaccine group (0.7%) was not statistically significantly different from the attack rate in the placebo group (0.9%).

Conclusion

Due to the atypical nature of the influenza season during this study we were unable to assess TIV efficacy. This experience illustrates the challenge of conducting a prospective influenza vaccine efficacy trial during a single season when influenza attack rates and drift in circulating strains or B virus lineage match can be difficult to estimate in advance.

Trial Registration

Clinical trial registery: NCT00197223.

Respiratory syncytial virus differentially activates murine myeloid and plasmacytoid dendritic cells

Respiratory syncytial virus (RSV) is the primary cause of bronchiolitis in young children. Upon infection both T helper 1 (Th1) and Th2 cytokines are produced. Because RSV-induced Th2 responses have been associated with severe immunopathology and aggravation of allergic reactions, the regulation of the immune response following RSV infection is crucial. In this study we examined the influence of RSV on the activation and function of murine bone marrow-derived dendritic cells (DCs). RSV induced the expression of maturation markers on myeloid DCs (mDCs) in vitro. The mDCs stimulated with RSV and ovalbumin (OVA) enhanced proliferation of OVA-specific T cells, which produced both Th1 and Th2 cytokines. In contrast to mDCs, RSV did not induce the expression of maturation markers on plasmacytoid DCs (pDCs), not did it enhance the proliferation of OVA-specific T cells that were cocultured with pDCs. However, RSV stimulated the production of interferon-alpha (IFN-alpha) by pDCs. Our findings indicate a clear difference in the functional activation of DC subsets. RSV-stimulated mDCs may have immunostimulatory effects on both Th1 and Th2 responses, while RSV-stimulated pDCs have direct antiviral activity through the release of IFN-alpha.

Accuracy of clinical diagnosis of influenza in outpatient children

In a prospective study, children < or =13 years of age with respiratory infections were examined. At each visit, a nasal swab specimen was obtained for the detection of influenza, and the physician recorded his or her opinion on whether the child had influenza. Among 2288 infections, the overall sensitivity of the clinical diagnosis of influenza was 38% and the positive predictive value was 32%.

Tissue tropism of recombinant coxsackieviruses in an adult mouse model

Recombinant viruses, constructed by exchanging the 5′ non-coding region (5′NCR), structural and non-structural protein coding sequences were used to investigate determinants responsible for differences between coxsackievirus A9 (CAV9) and coxsackievirus B3 (CBV3) infections in adult mice and two cell lines. Plaque assay titration of recombinant and parental viruses from different tissues from adult BALB/c mice demonstrated that the structural region of CBV3 determined tropism to the liver tissue due to receptor recognition, and the 5′NCR of CBV3 enhanced viral multiplication in the mouse pancreas. Infection with a chimeric virus, containing the structural region from CBV3 and the rest of the genome from CAV9, and the parental CBV3 strain, caused high levels of viraemia in adult mice. The ability of these viruses to infect the central nervous system suggested that neurotropism is associated with high replication levels and the presence of the CBV3 capsid proteins, which also enhanced formation of neutralizing antibodies. Moreover, the appearance of neutralizing antibodies correlated directly with the clearance of the viruses from the tissues. These results demonstrate potential pathogenicity of intraspecies recombinant coxsackieviruses, and the complexity of the genetic determinants underlying tissue tropism.

Viral diagnosis by antigen detection techniques

BACKGROUND

Diagnosis of viral infections can be obtained in the early stages of a disease by detection of viral antigens directly in the clinical specimen. This has become an important tool for rapid virus diagnosis.

METHODS

Antigens produced during virus infections can be detected either in cells collected from the site of infection by immunohistological investigation or in secretions and blood by solid phase immunoassays (IA). Viruses causing acute respiratory infections can be diagnosed in cells from the respiratory tract, viruses causing vesicular eruptions in epithelial cells from skin scrapings, rabies virus in nerve cells of the brain or epithelial cells from skin and cornea and cytomegalovirus (CMV) matrix antigen, pp65, can be detected in peripheral blood leukocytes (PBL) by immunofluorescence (IF) or immunoperoxidase techniques. The quality of specimens can be easily checked during the reading of results. Some IAs for antigen detection, such as detection of HBsAg and HIV p24 antigen in blood are standardized and sensitive. Others give less sensitive results because of the variation of quality of the clinical specimen. The latex agglutination tests are mainly used for rapid detection of virus or viral antigens in faeces: rota-and adenoviruses; the method may not be very sensitive but yields a result within a few minutes. Assays detecting viral nucleic acids are more sensitive than antigen detection tests because of a tremendous amplification of gene segments obtained by the polymerase chain reaction (PCR). So far such assays are time consuming and expensive and are mainly used in specific clinical situations.

RESULTS

After introduction of specific monoclonal antibodies (Mabs), the antigen detection techniques are increasingly used. the need for quality control, trained staff, and standardized reagents and methods for specimen collection and preparation is now being appreciated. IF for viral respiratory viruses is used for diagnosis and epidemiological studies all over the world. Likewise, IF is still the method most often used for rabies diagnosis. For CMV, the pp65 matrix antigen is shown to be a sensitive marker closely correlated with clinical symptoms. Its detection by the IF technique has proven to be superior to other techniques for prediction of CMV pneumonia in bone marrow transplant patients. IAs are currently used in fully automated systems for large scale diagnosis based on antigen detection in serum specimens. Increase of antibody specificity on the solid phase by use of Mabs directed against the most abundant viral antigen in the clinical specimen shortens the reaction time; this has been employed in most of the constantly appearing new rapid diagnosis kits based on the immunoassay principle.

CONCLUSION

Although, in virology, more sensitive results are obtained by the gene detection method, PCR, directly in clinical samples, viral antigen detection tests are, after the introduction of Mabs for diagnostic purposes, increasingly used because of their low demand on laboratory equipment, their rapid and early result and relatively low cost. Antigen detection is successfully used directly in clinical specimens for rapid diagnosis of many viral infections as well as for identification of tissue culture isolated viruses. With Mab-based IAs the reaction time is shortened and new rapid, almost 'instant test' kits are appearing on the market.

Advances in the diagnosis of respiratory virus infections

Background: Advances have been made in selecting sensitive cell lines for isolation, in early detection of respiratory virus growth in cells by rapid culture assays, in production of monoclonal antibodies to improve many tests such as immunofluorescence detection of virus antigens in nasopharyngeal aspirates, in highly sensitive antigen detections by time-resolved fluoroimmunoassays (TR-FIAs) and biotin-enzyme immunoassays (BIOTH-E), and, finally, in the polymerase chain reaction (PCR) detection of respiratory virus DNA or RNA in clinical specimens. All of these advances have contributed to new or improved possibilities for the diagnosis of respiratory virus infections.

Objectives and study design: This review summarizes our experiences during the last 15 years in the development of diagnostic tests for respiratory virus infections, and in use of these tests in daily diagnostic work and in epidemiological studies.

Results: Immunofluorescence tests based on monoclonal antibodies, all-monoclonal TR-FIAs, and biotin-enzyme immunoassays (EIAs) have about the same sensitivities and specificities. They compare well with the sensitivity of virus culture. PCR followed by liquid-phase hybridization is a sensitive method for detecting adenovirus DNA and enterovirus and rhinovirus RNA in clinical specimens. IgG EIA on paired acute and convalescent phase sera is the most sensitive serological test for respiratory virus infections and is a valuable reference method when evaluating the sensitivity of new diagnostic tests. The IgG avidity test can distinguish primary infections from re-infections at least in respiratory syncytial virus (RSV) infections. IgM antibody assays, on the other hand, had low sensitivities in our studies.

Conclusions: The choice of diagnostic methods for respiratory virus infections depends on the type and location of the laboratory, the number of specimens tested, and the previous experience of the laboratory. Virus culture, whenever possible, should be the basic diagnostic method; the results, including identification of the virus, should be available no more than 24 h later than the results of rapid diagnostic tests. In small laboratories, especially in hospitals where specimen transportation is well organized, immunofluorescence may be the best choice for antigen detection with the provision that an experienced microscopist and a good UV microscope are available. If the laboratory receives a large number of specimens and has previous experience with EIAs, then biotin-EIAs or TR-FIAs may be the most practical techniques. Their advantages include the stability of the antigens in clinical samples since intact, exfoliated epithelial cells are not required, treatment of specimens is practical, testing of large numbers of specimens is possible, and reading the printed test result is less subjective than reading fluorescence microscopy. The larger role of PCR in the diagnosis of respiratory virus infections depends on future developments such as practical methods to extract DNA or RNA and to purify the extracts from nonspecific inhibitors, plus further improvements to minimize cross-contamination. Group-specific detection of enteroviruses and rhinoviruses is an example of the potential for PCR technology. In experienced laboratories. EIA IgG antibody tests should be available. Recombinant antigens may be a useful part of such assays.

Detection of influenza B in clinical specimens: comparison of high throughput RT-PCR and culture confirmation

Influenza virus is one of the major causes of worldwide respiratory tract infections during the winter season. Here we describe a high throughput (HTP) protocol for rapid diagnosis of influenza B that combines automated viral RNA extraction with detection and quantification by TaqMan-based PCR. Using this methodology, we tested 4176 nasal swabs collected from children enrolled in a European influenza vaccine trial during the winter of 2000 to compare our HTP PCR method to culture confirmation for detection of influenza B. Among these, 37 were positive by culture and 169 were positive by PCR irrespective of virus copy number. However, when specimens with fewer than 20 copies of the viral genome were disregarded, a good correlation between two methods was observed. At this cut-off, 34 specimens were positive and 4106 were negative by both methods. Statistical analysis of the data using culture confirmation as the standard indicated that the sensitivity of HTP RT-PCR for influenza B was 92% (95% CI, 0.83-1), and the specificity was 99% (95% CI, 0.99-1). In summary, HTP RT-PCR was proved to be more rapid and sensitive than culture confirmation, and it correlated significantly with culture confirmation for specimens containing more than 20 copies of the viral genome.

Influenza in the intensive care unit

Influenza remains an important epidemic viral infection. Thousands of deaths occur and billions of dollars are spent each year with influenza-related illnesses. Morbidity and mortality are largely attributed to respiratory complications that may require intensive care unit (ICU) admission. Medical and neonatal ICUs, transplant units, chronic-care wards, and nursing homes are at increased risk for nosocomial outbreaks of influenza, which are characterized by abrupt onset and rapid spread. In this article, the authors review the current concepts, recent advances, and management strategies in influenza-associated pneumonia. Pertinent issues to the critical care practitioner are discussed in detail.

NuMA and nuclear lamins are cleaved during viral infection--inhibition of caspase activity prevents cleavage and rescues HeLa cells from measles virus-induced but not from rhinovirus 1B-induced cell death

Nuclear matrix is a structural framework of important nuclear processes. We studied the effect of two different types of viral infections on nuclear matrix. HeLa cells were infected with human rhinovirus 1B (HRV 1B) or measles virus (MV), and Nuclear Mitotic Apparatus protein (NuMA) and lamins A/C and B were used as markers for internal nuclear matrix and peripheral nuclear lamina, respectively. We show that NuMA, lamins, and poly(ADP-ribose) polymerase-1 are cleaved during viral infection in a virus family-specific manner suggesting that these viruses activate different sets of proteases. Morphologically, NuMA was excluded from the condensed chromatin, lamins showed a folded distribution, and both proteins finally remained around the nuclear fragments. A general caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (z-VAD-FMK) prevented the nuclear disintegration and the cleavage of the proteins studied. Interestingly, z-VAD-FMK rescued MV-infected but not HRV 1B-infected cells from cell death. These results show for the first time that NuMA and lamins are specific target proteins during virus-induced programmed cell death.

Rhinopharyngites de l’enfant

La rhinopharyngite désigne une inflammation modérée des voies aériennes supérieures d’origine infectieuse. Les signes habituels en sont l’obstruction nasale, la rhinorrhée, l’éternuement, la douleur pharyngée et la toux. Le terme de rhinopharyngite est spécifiquement français. Les auteurs anglo-saxons parlent de rhume (common cold) ou de upper respiratory tract infection (URI) pour décrire une inflammation aiguë des voies aériennes supérieures, et d’adénoïdite chronique (chronic adenoiditis) pour désigner une infection chronique des végétations adénoïdes responsable de rhinorrhées fébriles itératives ou d’obstruction des voies aériennes supérieures. Les rhinopharyngites aiguës non compliquées sont d’origine virale. Leur évolution spontanée est habituellement rapide et non compliquée. Elles ne nécessitent donc ni prélèvement bactériologique ni antibiothérapie systématique. En première intention, elles relèvent exclusivement d’un traitement antalgique et antipyrétique associé à des lavages des fosses nasales au sérum salé iso- ou hypertonique. Les complications des rhinopharyngites sont infectieuses, essentiellement représentées par les otites et les sinusites, et respiratoires obstructives. Le caractère fréquemment itératif des rhinopharyngites à partir de l’âge de 6 mois reflète un processus physiologique de maturation du système immunitaire. En présence de rhinopharyngites fréquentes et invalidantes, les principaux facteurs de risque devant être recherchés et si possible éradiqués sont le tabagisme passif et la fréquentation d’une collectivité d’enfants. L’adénoïdectomie n’est pas indiquée en l’absence de complications. Le développement d’antiviraux efficaces dans la prévention et dans le traitement des rhinopharyngites fait l’objet d’intenses recherches cliniques et expérimentales.

Rinofaringitis infantiles

La rinofaringitis designa una inflamación moderada de las vías respiratorias superiores de origen infeccioso. Sus signos habituales son obstrucción nasal, rinorrea, estornudos, dolor faríngeo y tos. Los autores anglosajones hablan de catarro (common cold) o de infección de vías respiratorias altas para describir una inflamación de las vías respiratorias superiores, y de adenoiditis crónica (chronic adenoiditis) para designar una infección crónica de las vegetaciones adenoides que produce rinorrea febril recidivante u obstrucción de las vías respiratorias altas. Las rinofaringitis agudas no complicadas son de origen vírico. Habitualmente su evolución espontánea es rápida y sin complicaciones. Por tanto, no hay que obtener muestras bacteriológicas ni hacer un tratamiento antibiótico sistemático. Como tratamiento de primera línea, sólo precisan analgésicos y antipiréticos asociados a lavados de las fosas nasales con suero salino isotónico o hipertónico. Las complicaciones de las rinofaringitis son infecciosas –representadas esencialmente por las otitis y las sinusitis– y respiratorias obstructivas. El carácter a menudo repetitivo de las rinofaringitis a partir de los 6 meses de edad refleja un proceso fisiológico de maduración del sistema inmunitario. Cuando existen rinofaringitis frecuentes e invalidantes, los principales factores de riesgo que se deben buscar, y de ser posible erradicar, son el tabaquismo pasivo y los contactos con una población infantil. La adenoidectomía ya no está indicada si no existen complicaciones. Se están realizando investigaciones clínicas y experimentales sobre el desarrollo de fármacos antivíricos eficaces para la prevención y el tratamiento de las rinofaringitis.

Persistent high plasma levels of interleukins 18 and 4 in children with recurrent infections of the upper respiratory tract

The aim of this study was to examine whether children with recurrent infections of the upper respiratory tract might have alterations in the systemic immune response to viral infections as compared with healthy control children. We quantitated plasma levels of interferon-gamma, interleukin-12, interleukin-18, interleukin-4, lymphocyte subpopulations, serum immunoglobulins, and subclasses of immunoglobulin G in 30 children under the age of 6 years with recurrent infections of the upper respiratory tract, both during the acute phase of the infection and 4 weeks later, when clinical symptoms had resolved, as well as in 20 normal controls. We found elevated levels of immunoglobulin G primarily due to increased levels of immunoglobulin G(1). Moreover, significantly higher levels of interleukin-18 and interleukin-4 were noted during the acute phase of infection among children with an increased incidence of respiratory infections as compared with the controls (P =.022 and P =.0001, respectively), while plasma levels of interferon-gamma and interleukin-12 were significantly lower (P =.034 and P =.0001, respectively) than in controls. We suggest that an imbalance between T-cell helper type-1 and T-cell helper type-2 immune responses might be responsible for the perpetuation of recurrent infections of the upper respiratory tract.

Incidence of influenza in Finnish children

BACKGROUND

Influenza is an important cause of respiratory illness in children, but data on virologically confirmed influenza infections in children treated as outpatients are limited.

METHODS

We carried out a prospective cohort study of normal children younger than 13 years (n = 1338) in the winter of 2000 to 2001. During the study period of 32 weeks, the children were examined at the study clinic whenever they had fever or signs of respiratory infection. Nasal swabs were obtained during each episode of infection for determination of the viral etiology of the illness.

RESULTS

The overall attack rate of influenza in the cohort was 18.8%. Influenza viruses were isolated from the children from the beginning of November 2000 through May 2001. Virtually in each week between mid-November and the end of April (a period of 24 weeks), influenza viruses accounted for at least 5% of all respiratory infections in the children. During the peak of the epidemic, the percentage of influenza-positive children exceeded 20%.

CONCLUSIONS

This study confirms the important role of influenza as a cause of acute respiratory infections in children, even in winters of mild or moderate influenza activity. The study also shows that influenza viruses may circulate in the community at substantial levels much longer than previously thought.

Five years' experience of reverse-transcriptase polymerase chain reaction in daily diagnosis of enterovirus and rhinovirus infections

To determine the efficiency of reverse-transcriptase polymerase chain reaction (RT-PCR) assays currently used in diagnosing enterovirus and rhinovirus infections, we compared results obtained with RT-PCR methods, which detect both enteroviruses and rhinoviruses simultaneously, with results obtained by conventional virus isolation. Both tests were performed on 591 specimens: 38 samples (6%) had positive results by both RT-PCR and isolation, 90 samples (15%) had positive results by RT-PCR only, and 7 samples (1%) had positive results only by virus isolation. In conclusion, RT-PCR was superior in rapidity and sensitivity to virus isolation and is recommended as the primary diagnostic tool for enterovirus and rhinovirus infections.

Zanamivir: a significant reduction in viral load during treatment in military conscripts with influenza

A randomized, double-blind, placebo-controlled, parallel-group trial performed at 5 residential units of the Finnish Defence Forces was conducted to assess the antiviral activity, efficacy and safety of inhaled zanamivir for the treatment of naturally acquired influenza. Conscripts were recruited within 2 d of onset of typical influenza symptoms and received inhaled zanamivir 10 mg via a Diskhaler twice daily for 5 d or matching placebo. Time to alleviation of clinically significant symptoms of influenza was the primary endpoint. Viral load measurements were made using quantitative real-time polymerase chain reaction assays. 435/588 patients (74%) had laboratory-confirmed influenza infection. The mean area under the curve for viral load during the first 48 h of treatment was 8.48 [95% confidence interval (95% CI) 2.85 to 14.11] log10 vRNA copies/ml x h lower in the zanamivir group compared with placebo (p = 0.003). Zanamivir reduced the time to alleviation of symptoms versus placebo in the influenza-positive group (medians 2.0 vs 2.33 d; 95% CI-0.17 to 1.0 d, p = 0.08). Zanamivir rapidly reduced viral load following the start of therapy compared with placebo and was well tolerated.

Influenza A and B virus infections in children

To obtain data on the clinical manifestations of infection, the age distribution, and the underlying conditions of children with influenza severe enough to lead to hospital referral, we performed a retrospective study of children treated at Turku University Hospital (Turku, Finland) in 1980-1999. Influenza A or B antigen was detected in the nasopharyngeal aspirates of 683 of the 15,420 children studied. The median age of children with influenza A was 2.0 years (n=544), and that of children with influenza B was 4.2 years (n=139) (P<.001). One-fourth of the children had an underlying medical condition. High fever, cough, and rhinorrhea were the most frequently recorded symptoms. Acute otitis media developed in 24% of the children, and pneumonia developed in 9% of the children. The study shows that the majority of patient hospitalizations for pediatric influenza involve previously healthy infants and young children. Laboratory confirmation of influenza is particularly important for children because the clinical presentation of the infection is less characteristic than that seen in adults.

The common cold

Despite great advances in medicine, the common cold continues to be a great burden on society in terms of human suffering and economic losses. Of the several viruses that cause the disease, the role of rhinoviruses is most prominent. About a quarter of all colds are still without proven cause, and the recent discovery of human metapneumovirus suggests that other viruses could remain undiscovered. Research into the inflammatory mechanisms of the common cold has elucidated the complexity of the virus-host relation. Increasing evidence is also available for the central role of viruses in predisposing to complications. New antivirals for the treatment of colds are being developed, but optimum use of these agents would require rapid detection of the specific virus causing the infection. Although vaccines against many respiratory viruses could also become available, the ultimate prevention of the common cold seems to remain a distant aim.

Influenza

Influenza remains an important cause of morbidity and mortality in the United States. Although signs and symptoms of individual influenza cases are nonspecific, the epidemiology is characteristic, and a clinical diagnosis can be made accurately during epidemics. Several tests can be used to confirm influenza infection. Antiviral medications may be used for both treatment and prophylaxis, but prevention of influenza is most reliably achieved through vaccination.

Mapping of tissue tropism determinants in coxsackievirus genomes

Genomic regions responsible for the different tissue tropisms of coxsackievirus A9 (CAV9) and coxsackievirus B3 (CBV3) in newborn mice were investigated using recombinant viruses. Infectious cDNA clones of CAV9, a virus known to infect striated muscle, and CBV3, affecting the central nervous system, pancreas, liver, brown fat and striated muscle, were used to generate chimeric viruses. In situ hybridization analysis of different tissues from mice infected with the recombinant viruses, constructed by exchanging the 5' non-coding region (5'NCR), structural and non-structural genes, demonstrated that the pancreo- and liver tropism map predominantly to CBV3 sequences within the capsid genes, evidently due to receptor recognition. Although the major neurotropism determinant in the CBV3 genome was in the capsid region, viruses containing the CAV9 capsid were also able to initiate infection in the central nervous system provided they contained the CBV3 5'NCR. The presence of the 5'NCR of CAV9 clearly enhanced muscle tissue tropism.

Evaluation of the subtype specificity of monoclonal antibodies raised against H1 and H3 subtypes of human influenza A virus hemagglutinins

Three previously described monoclonal antibodies (MAbs) specific for influenza A(H1) hemagglutinins (HA) revealed high sensitivity (98.2 to 99.1%) and specificity (100%) when tested against 245 strains of different subtypes. One of them was included in the World Health Organization's influenza reagent kit for 2001 to 2002. In contrast, two MAbs raised against human influenza A(H3) HA revealed cross-reactivity with viruses of other subtypes.

Effect of lack of Interleukin-4, Interleukin-12, Interleukin-18, or the Interferon-gamma receptor on virus replication, cytokine response, and lung pathology during respiratory syncytial virus infection in mice

RSV is an important cause of bronchiolitis in infants. Immunopathology may play a role in RSV-induced bronchiolitis and severe RSV-induced disease has been associated with a Th2 type immune response. The aim of the study was to identify cytokine pathways that are crucial in influencing RSV-induced disease. For that purpose we inoculated IFNgammaR-/-, IL-12-/-, IL-18-/-, or IL-4-/- mice with RSV. We observed that an RSV infection resulted in a predominant Th1 cytokine response associated with slight bronchiolitis and alveolitis. Pulmonary histopathology was only aggravated in IFN R-/- mice, characterised by eosinophilic influx around the bronchioles. Despite subtle changes in cytokine expression, no differences in histopathology were observed in IL-12-/- and IL-18-/- mice. Deficiency of IL-4 has no effect on RSV-induced Th1 cytokines and pulmonary histopathology. IFNgamma-receptor deficiency during primary RSV infection resulted in a disturbed Th1 response based on increased IL-4, IL-5, and IL-13 expression and the presence of eosinophils in the lungs. It is concluded that IFNgamma signalling is required for a pronounced Th1 response to RSV while IL-12 and IL-18 are not. A shift in the balance between Th1 and Th2 towards a Th2 response induced by missing IFNgamma signalling leads to aggravated pulmonary pathology. This is not caused by enhanced viral load.

Influence of respiratory syncytial virus infection on cytokine and inflammatory responses in allergic mice

BACKGROUND

Th2 lymphocyte responses are associated with inflammation and disease during allergic responses. Exposure to particular environmental factors during the expression of allergy could result in more pronounced Th2-like immune responses and more severe disease. One factor might be a respiratory virus infection.

OBJECTIVE

The aim of our study was to investigate the influence of respiratory syncytial virus (RSV) infection on the expression of ovalbumin (OVA)-induced allergy in BALB/c mice.

METHODS

We determined OVA-specific IgE in serum, cytokine profiles and histopathological lesions in lungs of OVA-allergic mice after RSV infection.

RESULTS

OVA sensitization and challenge induced OVA-specific IgE in serum, Th2 cytokine mRNA expression, and mononuclear and eosinophilic inflammation in the lungs. RSV inoculation during the challenge period enhanced OVA-induced IL-4 and IL-5 mRNA expression in lung tissue. RSV further enhanced the OVA-induced hypertrophy of mucous cells and eosinophilic infiltration in lung tissue. Surprisingly, RSV infection decreased Th2 cytokine secretion and eosinophilic influx in bronchoalveolar lavage of OVA-allergic mice. Because inactivated RSV did not influence these responses, replication of RSV appeared essential for the modification of OVA-induced Th2 cytokine expression. RSV did not change OVA-specific IgE levels in serum. Furthermore, the RSV-induced IL-12 mRNA expression in lung tissue of OVA-allergic mice was diminished, but IFN-gamma mRNA expression was not affected.

CONCLUSION

RSV infection enhanced particular OVA-induced Th2 cytokine mRNA responses and pulmonary lesions in allergic mice and thus aggravated allergic respiratory disease.

Influenza pneumonia: a descriptive study

OBJECTIVE

To describe the clinical features and complications of patients hospitalized with influenza during the 1999-2000 influenza season.

METHODS

We reviewed all cases of patients with influenza admitted to a large metropolitan referral hospital during the 1999-2000 season.

RESULTS

Thirty-five adult patients (15 men and 20 women) tested positive for influenza A by direct enzyme immunoassay. A fourfold to sevenfold increase in the number of influenza cases was observed over previous years. Most patients had serious comorbid illnesses (88%), such as diabetes and chronic respiratory and heart disease. Seventeen patients developed pneumonia; these patients tended to be older (mean +/- SD, 63 +/- 13 years vs 51 +/- 19 years, respectively; p = 0.04) and had a higher incidence of chronic lung disease (41% vs 6%, respectively; p = 0.02) than the patients without pneumonia. Shortness of breath was the only symptom that distinguished patients with pneumonia from those with an upper respiratory tract illness alone. Antiviral treatment was begun 4 +/- 3 days from initiation of symptoms in patients with pneumonia and consisted of oseltamivir (35.2%), rimantadine (5.8%), or a combination of both (17.6%). Respiratory and/or blood culture results were positive in five patients (29%), Staphylococcus aureus was isolated in five patients, and Streptococcus pneumoniae was isolated in one patient. Ten of the patients with pneumonia (58.8%) were admitted to the ICU, and 5 patients (29%) died. The length of ICU stay and mechanical ventilation were 28 +/- 26 days and 21.5 +/- 20.5 days, respectively. Death in most pneumonia patients was attributed to respiratory failure.

CONCLUSION

The recognized number of hospital admissions for influenza increased fourfold to sevenfold over previous years, most likely due to the implementation of rapid diagnostic tests for influenza. Patients with signs and symptoms of influenza and shortness of breath should undergo chest radiography. Hospitalization of patients with influenza pneumonia occurred in both previously healthy and immunocompromised patients and had a high mortality. S aureus was the most common bacterial isolate in patients with influenza pneumonia. Empiric antibiotics with staphylococcal activity should be used pending culture results in patients with influenza pneumonia. The effectiveness of oseltamivir and rimantadine in treating patients with influenza pneumonia remains to be determined.

Comparison of 44/107L one-step immunocapture enzyme-immunoassay and time-resolved fluoroimmunoassay for influenza A diagnosis

One-step immunocapture enzyme-immunoassay (EIA) was compared with time-resolved fluoroimmunoassay (TR-FIA) for rapid diagnosis of influenza A infection by antigen detection. The high-affinity monoclonal antibodies (MAbs) recognising two independent epitopes on the conservative nucleoprotein were used for capture (MAb 44) and detection (MAb 107L) of antigen by both assays. The detection limit for purified recombinant influenza A virus nucleoprotein was approximately 10 pg by EIA and 5 pg by TR-FIA. The performance of the methods was evaluated by testing 43 known positive and 50 negative clinical specimens (nasopharyngeal washes and aspirates). The sensitivity and specificity was 93% and 92% for EIA and 100% and 98% for TR-FIA, respectively, in comparison to the reference A3/A1 TR-FIA. The relationship of 44/107L immunoassays has been evaluated: in comparison to 44/107L TR-FIA (100%), EIA confirmed 93% of positive and 94% of negative samples. In conclusion, the capture-detector pair of MAbs 44 and 107L can be used for the sensitive detection of influenza A viral antigen in clinical samples by both immunocapture methods. Despite the slightly lower accuracy of the EIA, widespread availability and economy of the EIA methodology makes it an advantageous alternative for the laboratory diagnosis of influenza A virus infections.

Both immunisation with a formalin-inactivated respiratory syncytial virus (RSV) vaccine and a mock antigen vaccine induce severe lung pathology and a Th2 cytokine profile in RSV-challenged mice

Respiratory syncytial virus (RSV) is the most important cause of bronchiolitis and pneumonia in infants and young children. Immunopathology may play a role in RSV-induced disease and a severe RSV infection may also be associated with an increased risk of developing asthma. Vaccination with formalin-inactivated RSV (FI-RSV) prior to infection resulted both in human and in the mouse model in extensive lung pathology. In the mouse model, it has been shown that this aggravation of disease was associated with a shift in the balance between Th1 and Th2 cytokines towards a Th2-type response. The aim of the present study was to characterise the immunological and inflammatory responses in BALB/c mice upon RSV infection with or without prior vaccination with aluminium-adjuvanted FI-RSV or control antigens (FI-Mock). As previously reported by others, we also observed that a primary RSV infection in BALB/c mice resulted in a predominant Th1-type cytokine response, which was associated with slight bronchiolitis and alveolitis. FI-RSV vaccination prior to RSV challenge prevented virus replication and was associated with an aggravation of pulmonary histopathology and a shift towards a Th2-type response. Vaccination with FI-Mock did not prevent RSV replication in the lung but resulted in an even more pronounced Th2 response after infection while these mice were not sensitised to specific viral antigens. Thus, viral replication in a Th2 responding animal (induced by aluminium-adjuvanted mock vaccine) appears to boost the Th2 response upon RSV infection.

Detection of respiratory syncytial virus in nasopharyngeal secretions by 24-well plate precentrifugation assay using a monoclonal antibody against F protein

BACKGROUND

Respiratory syncytial virus (RSV) is responsible for 50% of all bronchiolitis and 25% of pneumonia cases during the first month of life. Detection of the RSV antigen by immunofluorescence in exfoliated nasal epithelium or by other methods in nasopharyngeal swabs is useful in the potentially infected patient because results are available within a few hours. In contrast, RSV antigen detection in cell culture may require as much as 3 weeks.

METHODS

Three methods for detection of respiratory syncytial virus in 131 clinical respiratory specimens from patients with acute respiratory disease and bronchiolitis were compared utilizing the following: a precentrifugation immunofluorescence assay using Hep-2 cells, indirect immunofluorescence assay, and conventional tube cell culture using Hep-2 cells.

RESULTS

Respiratory syncytial virus was identified in 36 specimens by the three methods previously described. The virus was recovered in 41 (31.3%) samples by precentrifugation immunofluorescence assay, 40 (30.5%) were identified by the immunofluorescence technique, and 38 (29.0%) cases were positive by conventional cell culture. The sensitivity of the precentrifugation assay in relation to the immunofluorescence technique was 90%, the specificity 94.5%, and the agreement, 96.2%. A positive predictive value of 90.2% was obtained. Sensitivity, specificity, agreement, and positive predictive values obtained by the precentrifugation assay variant compared to the conventional cell were 90.8%, 94.5%, 93.1%, and 87.8%, respectively.

CONCLUSIONS

The precentrifugation immunofluorescence assay method was as sensitive as the remainder of the methods used in our study and represents a valid alternative for rapid detection of respiratory syncytial virus in clinical samples.

Production of atypical measles in rhesus macaques: evidence for disease mediated by immune complex formation and eosinophils in the presence of fusion-inhibiting antibody

The severe disease atypical measles occurred when individuals immunized with a poorly protective inactivated vaccine contracted measles, and was postulated to be due to a lack of fusion-inhibiting antibodies. Here, rhesus macaques immunized with formalin-inactivated measles vaccine developed transient neutralizing and fusion-inhibiting antibodies, but no cytotoxic T-cell response. Subsequent infection with measles virus caused an atypical rash and pneumonitis, accompanied by immune complex deposition and an increase in eosinophils. Fusion-inhibiting antibody appeared earlier in these monkeys than in non-immunized monkeys. These data indicate that atypical measles results from previous priming for a nonprotective type 2 CD4 T-cell response rather than from lack of functional antibody against the fusion protein.

Viruses and bacteria in bronchial samples from patients with primary hypogammaglobulinemia

Viruses and bacteria in bronchoalveolar lavage fluids, protected specimen brush samples, and bronchial biopsies from 14 patients with primary hypogammaglobulinemia (11 patients with common variable immunodeficiency [CVID] and three patients with X-linked agammaglobulinemia [XLA]) were analyzed. At the time of the study, the patients had no signs of acute respiratory infections, and no antibiotics were administered. In addition to routine bacterial and viral cultures, polymerase chain reaction tests were used for the detection of adenovirus, cytomegalovirus (CMV), herpes simplex virus 1, enterovirus, rhinovirus, Borrelia burgdorferi, Chlamydia pneumoniae, Legionella spp., Mycoplasma pneumoniae, Pneumocystis carinii, and Ureaplasma urealyticum. Viruses (four adenoviruses, one CMV, and one rhinovirus) were detected in four of the 11 (36%) CVID patients. No viruses were found in the three patients with XLA or in 13 control patients. Bacteria from the lower respiratory tract were detected in nine of the 14 (64%) patients with hypogammaglobulinemia and three of the 13 (23%) control patients. Haemophilus influenzae was the most prevalent bacterium (43%) in the hypogammaglobulinemia patients. The study shows that patients with CVID harbor viral and bacterial infections in the lower respiratory tract, which may predispose to the development of changes in the respiratory tract.

Rapid detection and identification of two lineages of influenza B strains with monoclonal antibodies

Monoclonal antibodies (Mabs) against influenza B virus were obtained by immunizing mice with B/Nagasaki/1/87, one of the strains of the B/Victoria group. Immunoprecipitation analysis revealed that individual Mabs precipitated the nucleoprotein (NP), the matrix protein (M) or the hemagglutinin protein (HA). By using these Mabs by the peroxidase-antiperoxidase (PAP) staining method, a rapid detection and identification method for influenza B virus was established. Monolayers of Madin-Darby canine kidney cells in microplates were infected with each-strain and incubated for about 24 h, and then were subjected to the PAP staining method using the Mabs as the first antibody. Influenza B virus strains are classified into two major phylogenetic trees, the B/Victoria group and the B/Yamagata group. When anti-NP and anti-M antibodies were used in the PAP staining method, all 13 influenza B virus strains isolated from clinical specimens between 1940 and 1994 were detected regardless of the antigenic drift of the influenza virus. On the other hand, several anti-HA Mabs which reacted specifically with the strains of the B/Victoria group, did not react with any strain of the B/Yamagata group. In the 1996/97 influenza season in Osaka Prefecture in Japan, two antigenically distinct groups of influenza B virus strains were isolated. They belonged to different phylogenetic trees and were clearly distinguishable by the PAP staining method with anti-HA Mabs.

Development and use of nested polymerase chain reaction (PCR) for the detection of adenovirus from conjunctivitis specimens

BACKGROUND

The standard virus isolation method for detecting adenovirus is time consuming and direct detection of viral antigens in smears has its limitations. Therefore a rapid and a reliable method to identify virus in clinical specimens is desirable.

OBJECTIVE

To develop and evaluate nested PCR as a tool for detecting adenovirus from conjunctival swabs of patients with acute conjunctivitis during an epidemic.

STUDY DESIGN

A total of 201 patients with acute conjunctivitis were seen between August and November 1996. Conjunctival swabs from the most recently affected eyes were collected from 20 random patients and processed for antigen detection in direct smears, for adenovirus, enterovirus (EV70) and coxsackievirus A24 variant and adenovirus isolation by culture. Nested PCR was performed using oligonucleotides to amplify 1004 basepair (bp) and 956 bp fragments of DNA coding for adenovirus hexon protein. The neutralisation test, to type the adenovirus, was done on four isolates selected at random.

RESULTS

The PCR could detect 0.0032 fg of adenovirus DNA (corresponding to 8.3 x 10(-3) adenovirus particles). The EV70 and coxsackievirus A24 antigens were not detected. The specimens were positive for adenovirus by all three techniques in seven patients: (a) by direct smear and PCR in 2; (b) by virus isolation and PCR in 2; and (c) by PCR alone in five patients. In one patient the direct smear alone was positive. The PCR required 3 days to detect the virus, antigen detection provided diagnosis the same day and virus isolation required 8-27 days. A total of four isolates selected at random were identified as serotype 7a.

CONCLUSION

The nested PCR is a reliable and rapid technique for detection of adenovirus from conjunctival swabs. The adenovirus serotype 7a was the likely causative agent of this epidemic conjunctivitis.

Application of subtype-specific monoclonal antibodies for rapid detection and identification of influenza A and B viruses

We established a rapid method for the identification of influenza A and B virus strains: the peroxidase-antiperoxidase (PAP) staining method with two subtype-specific murine monoclonal antibodies, C179 (H1 and H2 specific) and F49 (H3 specific), and an anti-influenza B virus rabbit polyclonal serum. The types and subtypes of 160 strains were examined, and 158 strains were identified to be the same by the hemagglutination-inhibition (HI) test and the PAP method. In contrast to the results by the HI test, two strains were revealed to be a mixture of two subtypes (H1 and H3) by the PAP method, which was confirmed by plaque cloning. We further analyzed clinical specimens by the PAP method by directly inoculating specimens into Madin-Darby canine kidney cells in microplates. After 40 h of incubation, the types and subtypes of viruses in 52 of 152 specimens were clearly identified. Since the reactivities of the two monoclonal antibodies are not influenced by the antigenic drift of influenza virus, the newly developed method should be applicable not only for rapid diagnosis but also for the epidemiological study of influenza.

Detection of respiratory syncytial virus, parainfluenzavirus 3, adenovirus and rhinovirus sequences in respiratory tract of infants by polymerase chain reaction and hybridization

BACKGROUND

Immunofluorescence assay (IFA) of viral antigens in nasal aspirates is largely used for the diagnosis of respiratory syncytial virus (RSV), parainfluenzavirus (PIV) type 3 and adenovirus (AdV) infections, whilst rhinovirus (RV) are detected by virus isolation technique (VIT) only. Using the two techniques, IFA and VIT, a significant number of specimens remain negative in spite of clinical and epidemiological presumptions of viral infection.

OBJECTIVES AND STUDY DESIGN

The polymerase chain reaction (PCR) should improve the sensitivity of viral detection in clinical specimens. From October 1995 to March 1996, 277 nasal aspirates from hospitalized infants were tested simultaneously by IFA, VIT, polymerase chain reaction and hybridization with a DNA enzyme immunoassay (PCR-EIA) for RSV, PIV-3, AdV and RV.

RESULTS

RSV were detected in 177 (64%) samples, PIV-3 in 23 (8%), RV in 40 (14%), and AdV in 30 (10%). PCR-EIA detected RSV in more samples 173 (62%) than IFA/VIT: 109 (39%) (P < 10(-7)). In most cases (79%), RSV-infected infants had lower respiratory tract disease, and routine and PCR techniques were positive. Out of the 23 PIV-3 infections, 12 were IFA/VIT- and PCR-EIA-positive, and 11 IFA/VIT-negative and PCR-EIA-positive. For RV, 35 (87%) specimens were PCR EIA-positive and 11 (27%) culture-positive; for AdV 30 samples were PCR-EIA-positive and four were culture-positive. Simultaneous viral infections were revealed in a significantly higher proportion than in conventional techniques: 18% (50/277) versus 2.5% (7/277); P < 10(-7). One RSV infection in four was associated with the presence of another virus, mainly PIV-3 (16 cases) and AdV (13 cases).

CONCLUSIONS

PCR-EIA detects more positive-specimens than IFA/VIT, 1.5 times more for RSV, 1.9 for PIV-3, 4 for RV and 10 for AdV, respectively. This increased sensitivity of viral detection by PCR-EIA compared to the IFA/VIT could suggest that samples containing low levels of virus are missed by routine methods IFA/VIT, and consequently, RSV or PIV-3, and above all RV or AdV are overlooked as agents of respiratory diseases. However, apart from the fact that the economic and convenient aspects of virus diagnostic cannot be missed, it is difficult to answer the following questions: what is the meaning of the detection of a viral sequences in nasal aspirates of infants, or may PCR have detected virus in patients who would not developed disease?

Evaluation of monoclonal antibodies for subtyping of currently circulating human type A influenza viruses

The hemagglutinin subtype specificities of six monoclonal antibodies (MAbs) to influenza type A viruses were evaluated in a rapid culture assay by immunoperoxidase staining. Confluent monolayers of MDCK cells in multiwell plates were inoculated with (i) 23 reference viruses, (ii) 200 isolates collected during the influenza season 1995 to 1996, and (iii) 28 clinical specimens previously found to be influenza virus positive. After overnight incubation, the cells were fixed and stained with MAbs IVA1/B10, IIF4/D3, 12L/5, 13L/6, 18L/1, or 18L/4. Type-specific MAbs were included as controls. All antibodies gave intensive cytoplasmic staining with infected cells in the absence of any reaction with uninfected cells. MAbs 12L/5, 13L/6, 18L/1, and 18L/4 exclusively reacted with viruses of the subtype H1, and the antibodies IVA1/B10 and IIF4/D3 exclusively reacted with viruses of the subtype H3. None of these MAbs reacted with viruses of the H2 subtype or with influenza type B viruses. Of the 200 recent isolates, 63 were identified as influenza virus type A, subtype H1, 95 were identified as type A, subtype H3, and 41 were identified as type B. One isolate contained a mixture of a type A (H3) and a type B influenza virus. Of the 28 previously positive clinical specimens, 15 contained an influenza virus A, subtype H3, 1 contained an influenza virus A, subtype H1, and 9 contained an influenza B virus. The subtype of a very weakly positive specimen could not be determined, and two specimens remained negative. The MAbs described here allow for a rapid typing and subtyping of influenza virus isolates and for the type- and subtype-specific detection of influenza viruses in clinical specimens.

A sensitive one-step immunocapture EIA for rapid diagnosis of influenza A

A highly sensitive one-step immunocapture EIA for the detection of influenza A virus antigen directly in a clinical specimen was developed. The sensitivity was achieved by using two high-affinity cross-reactive influenza type A-specific monoclonal antibodies, recognizing independent nonoverlapping epitopes on the influenza A nucleoprotein. One of the two MAbs was used as a capture antibody, while the other was coupled with enzyme peroxidase and served as a detector. Sensitivity to detection of highly purified recombinant influenza A virus nucleoprotein by EIA reached approximately 10 pg. Fifteen purified human influenza A virus strains of H1, H2 and H3 subtypes, isolated during the period 1934-1992, were tested by this system. All the influenza A viruses tested positive, whereas two influenza B viruses used as a control were negative. The efficiency of the system for detection of influenza A viral antigen directly in clinical specimens was confirmed by testing nasal and nasopharyngeal washes and aspirates, tested previously by time-resolved fluoroimmunoassay and by virus culture confirmation assay.

Virus-specific, antibody-secreting cells during upper respiratory infections

The humoral immune response of 18 army recruits with febrile upper respiratory infection (URI) was studied by enumerating virus-specific, antibody-secreting cells in the peripheral blood. Diagnosis was based on viral antigen detection in nasopharyngeal specimens, virus isolation from throat swabs, or on antibody measurement from paired serum samples. At the time of the sample collection, three viruses, including adenovirus, influenza A, and influenza B, were found mainly to cause URIs among the recruits, and ELISPOT assay for enumeration of the specific antibody-secreting cells was selected for these viruses. Of the 36 patients with febrile URI studied, viral diagnosis was made in 18 cases, which included 11 patients with adenovirus infection, three with influenza A, and four with influenza B. The first blood sample was collected at the first signs of URI and the second and third samples at 2-week intervals. The adenovirus-positive patients developed a strong IgG class antibody-secreting cell response against the homologous virus, which peaked at the first sample and decreased steeply by the second and third samples. In the influenza A and B patients, the response was similar kinetically to that seen in adenovirus-positive patients. In those cases where also IgA and IgM class antibody-secreting cells were determined, the IgG response dominated. The ELISPOT method has potential also as a diagnostic tool for respiratory infections.

Incidence of acute otitis media associated with group A and B respiratory syncytial virus infections

The comparative association of respiratory syncytial virus group A and B infections with acute otitis media was determined by analysing the hospital records of children with community-acquired respiratory syncytial virus infection during three successive outbreaks from 1987 to 1992. Of 326 episodes analysed, 192 (59%) were caused by group A and 134 (41%) by group B infections. Acute otitis media was diagnosed in 101 (75%) children with group B infection, compared with 119 (62%) with group A infection (p = 0.01). Group A infections were more often associated with wheezing (71% versus 59% in group B; p = 0.02) and oxygen therapy in inpatients (48% versus 31%, respectively; p = 0.008). The higher incidence of acute otitis media associated with group B infections was observed both after adjustment for potential confounding variables and during each outbreak.

Preparation of monoclonal antibodies for the diagnosis of influenza A infection using different immunization protocols

Four immunization protocols were used to obtain cross-reactive influenza type A-specific monoclonal antibodies: (1) repeated administration of purified influenza virus, (2) immunization with bromelain-treated viral particles free of HA and NA, (3) sequential immunization with two strains of different subtypes, and (4) immunization with bromelain-treated particles following tolerization of mice to surface glycoproteins by cyclophosphamide. The fourth approach was shown to be the most effective since a high proportion of hybridomas producing cross-reactive influenza virus type A-specific MAbs were obtained. MAbs of type A specificity were immunochemically characterized and examined for their ability to detect virus in clinical specimens. It was demonstrated that two pairs of the newly prepared MAbs provided excellent reagents for viral detection in clinical specimens using time-resolved fluoroimmunoassay.

Type- and subtype-specific detection of influenza viruses in clinical specimens by rapid culture assay

A rapid culture assay which allows for the simultaneous typing and subtyping of currently circulating influenza A(H1N1), A(H3N2), and B viruses in clinical specimens was developed. Pools of monoclonal antibodies (MAbs) against influenza A and B viruses and MAbs HA1-71 and HA2-76, obtained by immunizing mice with the denatured hemagglutinin subfragments HA1 and HA2 of influenza virus A/Victoria/3/75, were used for immunoperoxidase staining of antigens in infected MDCK cells. MAb HA1-71 reacted exclusively with influenza A viruses of the H3 subtype, while MAb HA2-76 reacted with subtypes H1, H3, H4, H6, H8, H9, H10, H11, and H12, as determined with 78 human, 4 swine, and 10 avian influenza virus reference strains subtyped by the hemagglutination inhibition test. To determine if the technique can be used as a rapid diagnostic test, 263 known influenza virus-positive frozen nasal or throat swabs were inoculated into MDCK cells. After an overnight incubation, the cells were fixed and viral antigens were detected by immunoperoxidase staining. Influenza A viruses of the H1 and H3 subtypes were detected in 31 and 113 specimens, respectively. The subtypes of 10 influenza A virus-positive specimens could not be determined because they contained too little virus. Influenza B viruses were detected in 84 specimens, and 25 specimens were negative. We conclude that this assay is a rapid, convenient, non-labor-intensive, and relatively inexpensive test for detecting, typing, and subtyping influenza viruses in clinical specimens.

Biology of parainfluenza viruses

Parainfluenza virus types 1 to 4 (PIV1 to PIV4) are important human pathogens that cause upper and lower respiratory tract infections, especially in infants and children. PIV1, PIV2, and PIV3 are second only to respiratory syncytial virus as a cause of croup in young children. Although some clinical symptoms are typical of PIVs, etiologic diagnosis always requires detection of infectious virus, viral components, or an antibody response. PIVs are typical paramyxoviruses, causing a syncytial cytopathic effect in cell cultures; virus growth can be confirmed either by hemadsorption or by using immunological reagents. Currently, PIV is most often diagnosed by demonstrating viral antigens in clinical specimens by rapid and highly sensitive immunoassays. More recently, PCR has been used for the detection of PIVs. Serological diagnosis is made by detecting a rising titer of immunoglobulin G or by demonstrating immunoglobulin M antibodies. PIVs infect species other than humans, and animal models are used to study the pathogenesis of PIV infections and to test candidate vaccines. Accumulating knowledge on the molecular structure and mechanisms of replication of PIVs has accelerated research on prevention and treatment. Several strategies for vaccine development, such as the use of live attenuated, inactivated, recombinant, and subunit vaccines, have been investigated, and it may become possible to prevent PIV infections in the near future.