Novel respiratory virus infections in children, Brazil

Recently discovered respiratory viruses were detected in 19 (9.2%) of 205 nasal swab specimens from children in Brazil with respiratory illnesses. Five each were positive for human metapneumovirus (HMPV) alone and human bocavirus (HBoV) alone, 3 for human coronaviruses (HCoV-HKU1 or -NL63) alone, and 6 for more than 1 recently discovered virus.

Direct metagenomic detection of viral pathogens in nasal and fecal specimens using an unbiased high-throughput sequencing approach

With the severe acute respiratory syndrome epidemic of 2003 and renewed attention on avian influenza viral pandemics, new surveillance systems are needed for the earlier detection of emerging infectious diseases. We applied a “next-generation” parallel sequencing platform for viral detection in nasopharyngeal and fecal samples collected during seasonal influenza virus (Flu) infections and norovirus outbreaks from 2005 to 2007 in Osaka, Japan. Random RT-PCR was performed to amplify RNA extracted from 0.1–0.25 ml of nasopharyngeal aspirates (N = 3) and fecal specimens (N = 5), and more than 10 µg of cDNA was synthesized. Unbiased high-throughput sequencing of these 8 samples yielded 15,298–32,335 (average 24,738) reads in a single 7.5 h run. In nasopharyngeal samples, although whole genome analysis was not available because the majority (>90%) of reads were host genome–derived, 20–460 Flu-reads were detected, which was sufficient for subtype identification. In fecal samples, bacteria and host cells were removed by centrifugation, resulting in gain of 484–15,260 reads of norovirus sequence (78–98% of the whole genome was covered), except for one specimen that was under-detectable by RT-PCR. These results suggest that our unbiased high-throughput sequencing approach is useful for directly detecting pathogenic viruses without advance genetic information. Although its cost and technological availability make it unlikely that this system will very soon be the diagnostic standard worldwide, this system could be useful for the earlier discovery of novel emerging viruses and bioterrorism, which are difficult to detect with conventional procedures.

Differential recruitment of dendritic cells and monocytes to respiratory mucosal sites in children with influenza virus or respiratory syncytial virus infection

BACKGROUND

Influenza virus and respiratory syncytial virus (RSV) are among the most common viruses causing infections of the lower respiratory tract in young children. Although there are important differences in the immunopathogenesis of these 2 viral pathogens, little is known about how they affect antigen-presenting cells in children with acute infections.

METHODS

To characterize the immune cells that are mobilized to the respiratory tract by influenza virus and RSV, we analyzed nasal wash and blood samples obtained from children hospitalized with acute respiratory infections.

RESULTS

Influenza virus and RSV mobilize immune cells, including myeloid dendritic cells (mDCs) and plasmacytoid dendritic cells (pDCs), to the nasal mucosa. Patients with influenza virus infection had greater numbers of mDCs, pDCs, and monocytes in nasal wash samples than did patients with RSV infection. The frequencies of respiratory tract and blood T cell subsets were not affected by infection with influenza virus or RSV. Monocyte chemoattractant protein-1 concentrations in nasal wash samples were significantly increased in patients with influenza virus infection but not in those with RSV infection. RANTES (regulated on activation, normally T cell expressed and secreted) concentrations were increased only in the blood of patients with influenza virus infection.

CONCLUSIONS

Infection with influenza virus or RSV mobilizes antigen-presenting cells to the respiratory tract. The differences in antigen-presenting cell numbers and cytokine concentrations suggest that there are distinctive, early immune responses to these 2 viruses.

Infection, excretion and seroconversion dynamics of porcine circovirus type 2 (PCV2) in pigs from post-weaning multisystemic wasting syndrome (PMWS) affected farms in Spain and Denmark

Longitudinal case-control studies were performed in post-weaning multisystemic wasting syndrome (PMWS) affected farms from Denmark and Spain using similar designs. Fourteen independent batches of 100-154 pigs per batch were monitored from birth to PMWS outbreak occurrence. Pigs displaying PMWS-like signs and matched healthy cohorts were euthanized during the clinical outbreak. PMWS was diagnosed according to internationally accepted criteria and pigs were classified as: (i) PMWS cases, (ii) wasted non-PMWS cases and (iii) healthy pigs. Porcine circovirus type 2 (PCV2) quantitative PCR (qPCR) and serology techniques were applied to analyse longitudinally collected sera and/or nasal and rectal swabs. Results showed that PCV2 load increased in parallel to waning maternal antibody levels, reaching the maximum viral load concurrent with development of clinical signs. PMWS affected pigs had higher PCV2 prevalence and/or viral load than healthy pigs in all collected samples at necropsy (p<0.0001-0.05) and even in sera and nasal swabs at the sampling prior to PMWS outbreak (p<0.01-0.05). Danish farms had a higher PCV2 prevalence in young piglets as well as an earlier PMWS presentation compared to Spanish farms. PMWS diagnoses were confirmed by laboratory tests in only half of pigs clinically suspected to suffer from PMWS. Positive and significant correlations were found among PCV2 viral loads present in sera, nasal swabs, rectal swabs and lymphoid tissues (R=0.289-0.827, p<0.0001-0.01), which indicates that nasal and rectal swabs were suitable indicators of PCV2 excretion. Sensitivity and/or specificity values observed from both tests used separately or combined suggested that qPCR and/or serology tests are not apparently able to substitute histopathology plus detection of PCV2 in tissues for the individual PMWS diagnosis within PMWS affected farms. However, qPCR appears to be a potential reliable technique to diagnose PMWS on a population basis.

Experimental infection of rabbits with ovine herpesvirus 2 from sheep nasal secretions

Malignant catarrhal fever (MCF) is a generally fatal disease that primarily occurs in ruminants and is caused by a group of gammaherpesviruses. Outside of Africa MCF is mainly caused by ovine herpesvirus 2 (OvHV-2) which is carried subclinically by sheep. Cell-free virus is present in nasal secretions of shedding sheep and aerosol is the primary mode of transmission. Although OvHV-2 has never been propagated in vitro, experimental infection involving intranasal nebulization with nasal secretions from shedding sheep has been used to induce MCF in cattle and bison. This method of inoculation has never been tested in rabbits, which are the primary small animal model. The objectives of this study were to determine whether rabbits become infected with OvHV-2 after intranasal nebulization with cell-free virus from sheep nasal secretions and whether they develop MCF with consistent gross and histologic lesions. Five of eight rabbits became infected, showed clinical signs and developed histologic lesions typical of MCF including multisystemic vasculitis and perivascular lymphoid accumulation. These lesions are similar to those reported in rabbits infected by intravenous injection with tissues from clinically affected animals containing cell-associated virus. Viral DNA and mRNA transcripts of a structural viral protein were present in tissues from affected rabbits suggesting that viral replication occurred, although the significance in terms of pathogenesis is unknown. This work demonstrates that OvHV-2 infection of rabbits by intranasal nebulization is a potentially useful model that mimics the natural route of infection and may be used to study viral replication and pathogenesis.

The potential of phages to prevent MRSA infections

This short review attempts to examine whether there is a potential for the use of phages capable of infecting Staphylococcus aureus to eradicate or reduce nasal colonisation, thereby reducing the overall infection burden in patient populations identified as being at risk from MRSA infections. There is clear evidence that nasal decolonisation may be of benefit to certain patient groups and also that phages can effectively combat experimentally induced S. aureus infections in animals. However, this is not in itself enough to validate the use of phages for decolonisation and, given the appearance of strains resistant to currently used topical antibiotics, there is a need for clinical trials of this prophylactic use of phages.

Envelope protein Us9 is required for the anterograde transport of bovine herpesvirus type 1 from trigeminal ganglia to nose and eye upon reactivation

In this study, the authors examined the role of bovine herpesvirus type 1 (BHV-1) Us9 in the anterograde transport of the virus from trigeminal ganglia (TG) to nose and eye upon reactivation from latency. During primary infection, both BHV-1 Us9-deleted and BHV-1 Us9-rescued viruses replicated efficiently in the nasal and ocular epithelium. However, upon reactivation from latency, only the BHV-1 Us9-rescued virus could be isolated in the nasal and ocular shedding. By real-time polymerase chain reaction, comparable DNA copy numbers were detected in the TGs during latency and reactivation for both the viruses. Therefore, Us9 is essential for reactivation of the virus in the TG and anterograde axonal transport from TG to nose and eye.

A live bovine herpesvirus-1 marker vaccine is not shed after intramuscular vaccination

It should be established, whether animals vaccinated intramuscularly (IM) with a live Bovine herpesvirus type 1 (BHV-1) marker vaccine become viremic and/or excrete vaccine virus with nasal discharge. Five cattle, seronegative for BHV-1, were vaccinated with an overdose of the vaccine (Bovilis IBR marker live) via the IM route. Nasal swabs and blood samples were taken at regular intervals and tested for BHV-1 in a virus infectivity assay. In addition, a polymerase chain reaction (PCR) specific for BHV-1 DNA was performed on the blood samples. BHV-1 neutralizing antibody titres were determined in the sera taken prior to the vaccination and four weeks after immunisation. AIl animals were successfully vaccinated as judged by the development of BHV-1 neutralising antibodies. However, all nasal swab samples were tested negative for vaccine virus, and all blood samples were found negative for BHV-1 vaccine virus and BHV-1 specific DNA. From these data it can be concluded that the vaccine virus was not excreted with nasal discharge after IM vaccination and that the vaccinated animals did not have a detectable viremia. Therefore, it is recommended to apply the tested BHV-1 marker live vaccine by the IM route in situations where it is undesirable that the vaccine virus is excreted.

Similarity of European porcine reproductive and respiratory syndrome virus strains to vaccine strain is not necessarily predictive of the degree of protective immunity conferred

The objective of this study was to determine the degree of protection conferred by a Lelystad-like modified live virus (MLV) vaccine against a heterologous wild-type porcine reproductive and respiratory syndrome virus (PRRSV) isolate of the same cluster. For this purpose, fourteen 3-week-old piglets were divided into three groups: Group A pigs were vaccinated with a modified live virus vaccine, Group B pigs were used as positive controls, and Group C pigs as negative controls. Twenty-eight days after the last dose of vaccine, all pigs in Groups A and B were inoculated with the Spanish PRRSV strain 5710. To evaluate efficacy, clinical signs were recorded and the presence of challenge virus was determined by virus isolation in blood samples and nasal swabs collected at various time points post-challenge (p.c.) and in tissue samples collected at necropsy 24 days p.c. After challenge, moderate clinical signs were observed in pigs from Groups A and B. In addition, all vaccinated pigs were viremic at least once, although viremia tended to be more sporadic in this group than in Group B pigs. PRRSV was detected in at least one tissue sample from four out of five pigs from Group A and in all pigs from Group B. The results indicate that the protection conferred by the MLV vaccine used in this study against a closely related virulent strain was only partial. The findings suggest that the degree of genetic homology of ORF5 between MLV vaccine and challenge isolate is not a good predictor of vaccine efficacy.

Experimental infection of macaques with human metapneumovirus induces transient protective immunity

Human metapneumovirus (hMPV), a member of the family Paramyxoviridae, is a causative agent of acute respiratory-tract illness. Two main hMPV lineages circulate worldwide and reinfections occur frequently. It is unclear what level of protection is induced by natural hMPV infection, what the durability of this protection is and whether it differs for reinfection with homologous or heterologous viruses. Here, protective immunity in cynomolgus macaques at different time points after inoculation with molecularly cloned prototype viruses of the two main lineages of hMPV has been addressed. Animals received a homologous challenge at 4, 6 or 12 weeks after the primary infection. In addition, animals that had been inoculated three times within 10 weeks were challenged with homologous or heterologous virus 8 months later. Primary infection with 10(7) TCID(50) resulted in virus shedding and induction of virus-neutralizing antibody responses, with higher titres against the homologous than the heterologous virus. Infections associated with virus shedding and seroconversion protected completely from homologous reinfection within 6 weeks, and partly at 12 weeks, after primary infection. Eight months later, protection had waned to virtually undetectable levels. This study demonstrates that experimental hMPV infection induces transient protective immunity.

Establishment, characterization, and virus susceptibility of a new marine cell line from red spotted grouper (Epinephelus akaara)

A marine fish cell line from the snout of red spotted grouper Epinephelus akaara, a protogynous hermaphrodite, was established, characterized, and subcultured with more than 60 passages. The grouper snout cell line (GSC) cells multiplied well in Dulbecco's modified Eagle's medium (DMEM) medium supplemented with 10% fetal bovine serum. The optimal growth temperature was 25 degrees C, and morphologically the cells were fibroblastic. Chromosome analysis revealed that the GSC cell line has a normal diploid karyotype with 2n = 8st + 40t. A virus titration study indicated that the cells were susceptible to turbot Scophthalmus Maximus rhabdovirus (SMRV) (10(8.5) TCID(50) ml(-1)), while the viral titer of frog Rana grylio virus 9807 (RGV(9807)) reached 10(3.5) TCID(50) ml(-1). The infection was confirmed by cytopathic effect (CPE), immunofluorescence, and electron microscopy experiments, which detected the viral particles in the cytoplasm of virus-infected cells, respectively. Further, significant fluorescent signals were observed when the GSC cells were transfected with pEGFP vector DNA, indicating their potential utility for transgenic and genetic manipulation studies.

Linking syndromic surveillance with virological self-sampling

Calls to a UK national telephone health helpline (NHS Direct) have been used for syndromic surveillance, aiming to provide early warning of rises in community morbidity. We investigated whether self-sampling by NHS Direct callers could provide viable samples for influenza culture. We recruited 294 NHS Direct callers and sent them self-sampling kits. Callers were asked to take a swab from each nostril and post them to the laboratory. Forty-two per cent of the samples were returned, 16.2% were positive on PCR for influenza (16 influenza A(H3N2), three influenza A (H1N1), four influenza B) and eight for RSV (5.6%). The mean time between the NHS Direct call and laboratory analysis was 7.4 days. These samples provided amongst the earliest influenza reports of the season, detected multiple influenza strains, and augmented a national syndromic surveillance system. Self-sampling is a feasible method of enhancing community-based surveillance programmes for detection of influenza.

Inhibition of rhinovirus replication in vitro and in vivo by acid-buffered saline

Human rhinoviruses (HRVs) are quite sensitive to low pH. To determine whether this characteristic might be a therapeutic target, we evaluated the sensitivity of HRV to low-pH buffers in vitro and in vivo. Our findings confirm that low pH inhibited replication of most HRVs and reduced the replication of influenza virus. Preliminary experiments verified that the surface pH of the human nasopharynx could be transiently lowered to pH ∼4.0 by topical administration of citrate/phosphate (CP) buffers, which was well tolerated. In a pilot experimental colds study, intranasal administration of CP buffer, compared with normal saline, reduced viral shedding by 1 log unit (10³ vs. 10⁴ 50%tissue culture infective dose/mL; P < .01), although respiratory symptoms were not significantly reduced. These findings demonstrate that low-pH buffers have antiviral activity in vivo and suggest that a larger clinical trial is warranted to determine whether this approach could reduce rates of viral transmission.

Human bocavirus in Italian patients with respiratory diseases

BACKGROUND

hBoV, a recently discovered parvovirus, can be present in the respiratory tract of patients with acute respiratory diseases (ARD), but its etiologic involvement in the underlying diseases is still uncertain.

OBJECTIVE

To determine in a retrospective study, the prevalence of hBoV, compared with common respiratory viruses (RV), in respiratory specimens from patients with ARD.

STUDY DESIGN

A total of 335 specimens obtained over 7 years were examined. Two hundred were nasal swabs from infants hospitalized for ARD, 84 were nasal swabs or bronchoalveolar lavages from adults with pneumonia, bronchopneumonia or asthma, and 51 were nasal swabs from healthy children.

RESULTS

The overall rate of hBoV detection in specimens from infants with ARD, which was 4.5%, varied slightly from year to year, except for the period 2000-2002, when no specimen was positive. Unlike other RV, no seasonal variation in hBoV incidence was noted. Infants with hBoV infection suffered either from bronchiolitis or from bronchopneumonia and 5 out of 9 cases yielded no co-infecting viral pathogen. Only one sample from an adult was hBoV positive. None of the nasal swabs from healthy subjects tested hBoV-positive.

CONCLUSIONS

The findings indicate that hBoV can cause ARD in infants.

Pathogeneses of respiratory infections with virulent and attenuated vaccinia viruses

BACKGROUND

Respiratory infection with the neurovirulent vaccinia virus (VV) strain Western Reserve (WR) results in an acute infection of the lung followed by dissemination of the virus to other organs and causes lethality in mice. The mechanisms of lethality are not well-understood. In this study, we analyzed virus replication and host immune responses after intranasal infection with lethal and non-lethal doses of VV using the WR strain and the less virulent Wyeth strain.

RESULTS

The WR strain replicated more vigorously in the lung and in the brain than the Wyeth strain. There were, however, no differences between the virus titers in the brains of mice infected with the higher lethal dose and the lower non-lethal dose of WR strain, suggesting that the amount of virus replication in the brain is unlikely to be the sole determining factor of lethality. The WR strain grew better in primary mouse lung cells than the Wyeth strain. Lethal infection with WR strain was associated with a reduced number of lymphocytes and an altered phenotype of the T cells in the lung compared to non-lethal infections with the WR or Wyeth strains. Severe thymus atrophy with a reduction of CD4 and CD8 double positive T cells was also observed in the lethal infection.

CONCLUSION

These results suggest that the lethality induced by intranasal infection with a high dose of the WR strain is caused by the higher replication of virus in lung cells and immune suppression during the early phase of the infection, resulting in uncontrolled virus replication in the lung.

A two-amino acid change in the hemagglutinin of the 1918 influenza virus abolishes transmission

The 1918 influenza pandemic was a catastrophic series of virus outbreaks that spread across the globe. Here, we show that only a modest change in the 1918 influenza hemagglutinin receptor binding site alters the transmissibility of this pandemic virus. Two amino acid mutations that cause a switch in receptor binding preference from the human alpha-2,6 to the avian alpha-2,3 sialic acid resulted in a virus incapable of respiratory droplet transmission between ferrets but that maintained its lethality and replication efficiency in the upper respiratory tract. Furthermore, poor transmission of a 1918 virus with dual alpha-2,6 and alpha-2,3 specificity suggests that a predominant human alpha-2,6 sialic acid binding preference is essential for optimal transmission of this pandemic virus. These findings confirm an essential role of hemagglutinin receptor specificity for the transmission of influenza viruses among mammals.

Immune and protective abilities of ubiquitinated and non-ubiquitinated pseudorabies virus glycoproteins

Plasmids encoding ubiquitinated (ubi-) or non-ubiquitinated (non-ubi-) glycoproteins of Pseudorabies virus (PRV) were used for vaccination of pigs. We found that the fusion of ubiquitin to viral glycoproteins increased their degradation in proteasomes in vitro, in which ubiquitin plays a key role. In the animals immunized with the plasmids encoding PRV ubi-glycoproteins and then challenged with PRV, we detected a slightly decreased cellular immune response on days 13 and 19 after immunization and a reduced nasal excretion of infectious virus on day 2 after the challenge. Afterwards, no effect of the ubiquitination of the glycoproteins on humoral or cellular immunity and on excretion of infectious virus was observed. Similarly, no effect of the ubiquitination on protective abilities of PRV glycoproteins was found.

Influence of isolate pathogenicity on the aerosol transmission of Porcine reproductive and respiratory syndrome virus

The objectives of this study were to evaluate the role of isolate pathogenicity in the aerosol transmission of Porcine reproductive and respiratory syndrome virus (PRRSV) and to determine whether PRRSV could be detected in air samples. To assess transmission, we exposed naive recipient pigs to aerosols from pigs inoculated with PRRSV MN-30100, an isolate of low pathogenicity, or MN-184, a highly pathogenic isolate. Blood samples and nasal-swab samples were collected from the inoculated pigs during the exposure period and tested for the presence of PRRSV RNA by quantitative (real-time) reverse-transcriptase polymerase chain reaction (RT-PCR); the amount of RNA was expressed as the median tissue culture dose per milliliter (TCID50/mL). The recipient pigs were clinically evaluated for 14 d after exposure and tested on days 7 and 14 by qualitative RT-PCR and enzyme-linked immunosorbent assay (ELISA). To prove the presence of PRRSV in aerosols, air samples were collected from each recipient-pig chamber by means of an air sampler. The PRRSV RNA concentrations were significantly higher (P = 0.01) in the blood samples from the pigs infected with PRRSV MN-184 than in the blood samples from those infected with PRRSV MN-30100; however, the concentrations in the nasal-swab samples were not significantly different (P = 0.26). Recipient pigs exposed to aerosols from pigs infected with PRRSV MN-184 became infected, whereas those exposed to aerosols from pigs infected with PRRSV MN-30100 did not; the difference in transmission rate was significant at P = 0.04. We detected PRRSV MN-184 RNA but not PRRSV MN-30100 RNA in air samples by PCR. Under the conditions of this study, PRRSV isolate pathogenicity may influence aerosol transmission of the virus.

Development of a vaccine-challenge model for avian metapneumovirus subtype C in turkeys

The objective of this study was to evaluate different preparations of avian metapneumovirus (aMPV) subtype C as vaccine challenge in turkeys. Two aMPV isolates and their respective nasal turbinate homogenates after propagation in turkeys were used in the study. Significantly higher clinical sign scores were recorded in birds inoculated with 20 or 2% turbinate homogenate of recent isolate. Birds in the above groups showed more pronounced histopathological lesions, and a higher percentage of birds showed viral RNA and antigen in tissues. The data demonstrated that nasal turbinate homogenate of recent isolate produced severe clinical signs and lesions in turkeys and could be an ideal candidate for vaccine-challenge studies.

Priming with DNA encoding E2 and boosting with E2 protein formulated with CpG oligodeoxynucleotides induces strong immune responses and protection from Bovine viral diarrhea virus in cattle

The objective of this study was to develop an optimal vaccination strategy for Bovine viral diarrhea virus (BVDV). The E2 protein of BVDV plays a major protective role against BVDV infection. In order to be able to compare DNA, protein and DNA prime-protein boost regimens, a plasmid was constructed encoding a secreted form of the NADL strain E2 protein (pMASIA-tPAsDeltaE2). Furthermore, a pure secreted recombinant DeltaE2 (rDeltaE2) protein was produced. The rDeltaE2 protein was formulated with a combination of Emulsigen and CpG oligodeoxynucleotide. Groups of calves were immunized with pMASIA-tPAsDeltaE2 or with rDeltaE2, or first with pMASIA-tPAsDeltaE2 and then with rDeltaE2. To evaluate the protection against BVDV, calves were challenged with BVDV strain NY-1 after the last immunization. Although all immunized calves developed humoral and cellular immune responses, the antibody responses in the DNA prime-protein boost group were stronger than those elicited by either the DNA vaccine or the protein vaccine. In particular, E2-specific antibody titres were enhanced significantly after boosting the DeltaE2 DNA-primed calves with rDeltaE2 protein. Moreover, protection against BVDV challenge was obtained in the calves treated with the DNA prime-protein boost vaccination regimen, as shown by a significant reduction in weight loss, viral excretion and lymphopenia, compared with the unvaccinated calves and the animals immunized with the DNA or protein only. These results demonstrate the advantage of a DNA prime-protein boost vaccination approach in an outbred species.

Comparison of tissue and fluid samples for the early detection of canine distemper virus in experimentally infected dogs

The clinical utility of various specimens was examined for the early diagnosis of canine distemper (CD). Seven healthy dogs at 17 weeks of age were experimentally infected with a field isolate of canine distemper virus. The RT-PCR was carried out to detect CDV NP gene. Dogs showed mild fever and leukopenia, however, typical clinical signs of CD were not seen through the experimental period. CDV amplicons were detected more, earlier and for longer period in the conjunctival swabs than in the other samples employed. These results suggested that conjunctival swab samples, which are easy to obtain and non-invasive, would be the most suitable and practical specimen for the early antemortem diagnosis of CDV infection.

Induction of antigen-specific T-cell subset activation to bovine respiratory disease viruses by a modified-live virus vaccine

OBJECTIVE

To determine the efficacy of a modified-live virus vaccine containing bovine herpes virus 1 (BHV-1), bovine respiratory syncytial virus (BRSV), parainfluenza virus 3, and bovine viral diarrhea virus (BVDV) types 1 and 2 to induce neutralizing antibodies and cell-mediated immunity in naïve cattle and protect against BHV-1 challenge.

ANIMALS

17 calves.

PROCEDURES

8 calves were mock-vaccinated with saline (0.9% NaCl) solution (control calves), and 9 calves were vaccinated at 15 to 16 weeks of age. All calves were challenged with BHV-1 25 weeks after vaccination. Neutralizing antibodies and T-cell responsiveness were tested on the day of vaccination and periodically after vaccination and BHV-1 challenge. Specific T-cell responses were evaluated by comparing CD25 upregulation and intracellular interferon-gamma expression by 5-color flow cytometry. Titration of BHV-1 in nasal secretions was performed daily after challenge. Results-Vaccinated calves seroconverted by week 4 after vaccination. Antigen-specific cell-mediated immune responses, by CD25 expression index, were significantly higher in vaccinated calves than control calves. Compared with control calves, antigen-specific interferon-gamma expression was significantly higher in calves during weeks 4 to 8 after vaccination, declining by week 24. After BHV-1 challenge, both neutralizing antibodies and T-cell responses of vaccinated calves had anamnestic responses to BHV-1. Vaccinated calves shed virus in nasal secretions at significantly lower titers for a shorter period and had significantly lower rectal temperatures than control calves.

CONCLUSION AND CLINICAL RELEVANCE

A single dose of vaccine effectively induced humoral and cellular immune responses against BHV-1, BRSV, and BVDV types 1 and 2 and protected calves after BHV-1 challenge for 6 months after vaccination.

Kinetics of influenza A virus infection in humans

Currently, little is known about the viral kinetics of influenza A during infection within an individual. We utilize a series of mathematical models of increasing complexity, which incorporate target cell limitation and the innate interferon response, to examine influenza A virus kinetics in the upper respiratory tracts of experimentally infected adults. The models were fit to data from an experimental H1N1 influenza A/Hong Kong/123/77 infection and suggest that it is important to include the eclipse phase of the viral life cycle in viral dynamic models. Doing so, we estimate that after a delay of approximately 6 h, infected cells begin producing influenza virus and continue to do so for approximately 5 h. The average lifetime of infected cells is approximately 11 h, and the half-life of free infectious virus is approximately 3 h. We calculated the basic reproductive number, R(0), which indicated that a single infected cell could produce approximately 22 new productive infections. This suggests that antiviral treatments have a large hurdle to overcome in moderating symptoms and limiting infectiousness and that treatment has to be initiated as early as possible. For about 50% of patients, the curve of viral titer versus time has two peaks. This bimodal behavior can be explained by incorporating the antiviral effects of interferon into the model. Our model also compared well to an additional data set on viral titer after experimental infection and treatment with the neuraminidase inhibitor zanamivir, which suggests that such models may prove useful in estimating the efficacies of different antiviral therapies for influenza A infection.

Evaluation of the Quidel QuickVue test for detection of influenza A and B viruses in the pediatric emergency medicine setting by use of three specimen collection methods

The Quidel QuickVue influenza test was compared to viral culture and reverse transcriptase PCR by the use of three different respiratory specimen types. Of 122 pediatric subjects enrolled, 59 had influenza virus infections: 44 were infected with influenza A virus and 15 were infected with influenza B virus. The sensitivity of the QuickVue test was 85% with nasopharyngeal swabs, 78% with nasal swabs, and 69% with nasopharyngeal washes. Specificities were equivalent (97% to 98%) for all three collection methods.

Human metapneumovirus in adults: a short case series

This study was carried out to further the available information on adult cases of human metapneumovirus (hMPV), a recently described cause of respiratory infection. Among a cohort of 741 symptomatic patients tested since 2003, the virus was diagnosed in six adults using reverse transcriptase polymerase chain reaction. Of the six, two were from the community, two were hospital inpatients with chronic obstructive pulmonary disease and two were immunocompromised patients, both of whom required ventilation and later died. This report discusses the clinical features, epidemiology and diagnosis of hMPV, highlighting that this infection may be associated with death in high-risk adults. For adults presenting with respiratory symptoms and a background of pre-existing respiratory disease or who are immunocompromised, nucleic acid-based techniques are a cost-effective means of making the viral diagnosis in a clinically relevant time frame.

A chimpanzee-origin adenovirus vector expressing the rabies virus glycoprotein as an oral vaccine against inhalation infection with rabies virus

Rabies has the highest fatality rate of all human viral infections and the virus could potentially be disseminated through aerosols. Currently licensed vaccines to rabies virus are highly effective but it is unknown if they would provide reliable protection to rabies virus transmitted through inhalation, which allows rapid access to the central nervous system upon entering olfactory nerve endings. Here we describe preclinical data with a novel vaccine to rabies virus based on a recombinant replication-defective chimpanzee-origin adenovirus vector expressing the glycoprotein of the Evelyn Rokitniki Abelseth strain of rabies virus. This vaccine, termed AdC68rab.gp, induces sustained central and mucosal antibody responses to rabies virus after oral application and provides complete protection against rabies virus acquired through inhalation even if given at a moderate dose.

Challenge with Bovine viral diarrhea virus by exposure to persistently infected calves: protection by vaccination and negative results of antigen testing in nonvaccinated acutely infected calves

Calves persistently infected (PI) with Bovine viral diarrhea virus (BVDV) represent an important source of infection for susceptible cattle. We evaluated vaccine efficacy using calves PI with noncytopathic BVDV2a for the challenge and compared tests to detect BVDV in acutely or transiently infected calves versus PI calves. Vaccination with 2 doses of modified live virus vaccine containing BVDV1a and BVDV2a protected the calves exposed to the PI calves: neither viremia nor nasal shedding occurred. An immunohistochemistry test on formalin-fixed ear notches and an antigen-capture enzyme-linked immunosorbent assay on fresh notches in phosphate-buffered saline did not detect BVDV antigen in any of the acutely or transiently infected calves, whereas both tests had positive results in all the PI calves.

Detection of respiratory syncytial virus and human metapneumovirus by reverse transcription polymerase chain reaction in adults with and without respiratory illness

BACKGROUND

Reverse transcription polymerase chain reaction (RT-PCR) is a powerful tool that allows the detection of minute quantities of viral RNA. Because of the sensitivity of these assays it is possible that the finding of viral RNA indicates not only active infection but also transient colonization or residual nucleic acid from a distant infection. Respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) are two viruses for which RT-PCR is now frequently used for diagnosis in adult disease.

OBJECTIVE

We evaluated nasal secretions from adults with and without respiratory illnesses by nested, one-tube RT-PCR for RSV and hMPV to determine if rates of detectable RNA were significantly higher among ill subjects compared to controls suggesting a causal relationship with respiratory illness.

METHODS

Adults presenting to a health care provider with complaints of respiratory illness were recruited as "cases" and those visiting for non-respiratory complaints were recruited as "controls". Subjects were enrolled during a 3-month period (January to April) when both viruses were expected to be prevalent in the community. Nasal swab samples were obtained and subjected to one-tube nested RT-PCR for RSV and hMPV.

RESULTS

Of 146 ill subjects, 17 (11.6%) tested positive for RSV and 5 (3.4%) were positive for hMPV. Of the 158 control subjects, one was RT-PCR positive for RSV and none tested positive for hMPV. The rates of RT-PCR positive cases compared to controls were significantly different for RSV (p<.0001) and hMPV (p<.02). Subjects remained RSV RT-PCR positive on average until day 7.1+/-2.8 of symptoms with a range of 3-10 days. No subject had a positive swab on days 14, 21 or 28.

CONCLUSION

Asymptomatic carriage of RSV or hMPV is uncommon. RT-PCR should be a useful method for the diagnosis of these viral illnesses in adults.

Live attenuated influenza vaccine is safe and immunogenic in immunocompromised ferrets

Patients undergoing chemotherapy for cancer are highly susceptible to influenza virus infection. Prevention of influenza virus infection is complicated in the immunocompromised host because of suboptimal responses to the trivalent inactivated influenza vaccine (TIV). A new, live attenuated influenza vaccine (LAIV; FluMist) may offer a more effective alternative to TIV, but the safety of this LAIV in immunocompromised patients must first be established. In the present study, FluMist was administered to ferrets immunocompromised by treatment with dexamethasone and cytarabine. Ferrets exhibited no signs or symptoms attributable to FluMist, and nasal clearance of LAIV strains from immunocompromised ferrets was similar to that from control ferrets. Serum antibody responses against the vaccinating strains were analyzed as a measure of vaccine efficacy. Antibody titers to all 3 vaccine strains in immunocompromised ferrets were similar to those seen in mock-treated control ferrets, as assessed by microneutralization assay. These findings support the potential use of this vaccine in immunocompromised humans.

Vaccination with a gE-negative bovine herpesvirus type 1 vaccine confers insufficient protection to a bovine herpesvirus type 5 challenge

In the present study, cross-protection to bovine herpesvirus type 5 (BHV-5) induced by bovine herpesvirus type 1 (BHV-1) vaccination was examined following inoculation of rabbits and calves with a glycoprotein E (gE)-negative BHV-1 vaccine and subsequent challenge with BHV-5. Rabbits (n=5) and calves (n=8) were vaccinated [five rabbits intranasally (IN), four calves IN and four intramuscularly (IM)] with 7.1 log(10)median tissue culture infective dose (TCID(50)) of the BHV-1 vaccine. Rabbits and calves were challenged IN [rabbits 2 weeks post-vaccination (pv); calves 5 weeks pv] with 9.1log(10)TCID(50) of BHV-5. Two out of five vaccinated rabbits died after challenge with typical BHV-5 disease, as did 3/5 non-vaccinated controls. In calves, 4/8 vaccinated animals displayed mild signs of disease, whereas 6/6 non-vaccinated controls developed signs of disease, so severe that 2/6 had to be killed. Besides, nasal virus shedding post-challenge was not reduced by vaccination. At necropsy, on day 21 post-challenge, typical BHV-5 lesions were evident in brain tissues of both vaccinated and non-vaccinated calves. Dexametasone administration at 180 days post-infection did not reactivate clinical signs despite BHV-5 shedding in nasal secretions of both vaccinated and non-vaccinated calves. These results show that the BHV-1 vaccine evaluated here did not confer protection to BHV-5 in rabbits. In calves, BHV-1 vaccination did confer some protection to BHV-5 induced clinical disease, but it did not prevent infection and had no effect on nasal virus shedding or on the development of encephalitic lesions.

Comparison of three methods of collecting nasal specimens for respiratory virus analysis

BACKGROUND

Nasopharyngeal aspiration (NPA) is used widely in the collection of nasal specimens for respiratory virus diagnosis. The method has limitations in relation to technical expertise, patient anxiety, and apparatus dependence. Nasal washing (NW) offers an alternative approach.

OBJECTIVE

To identify the merits of two different NW methods in comparison with NPA.

DESIGN

Two hundred children with acute respiratory infection (ARI) were randomised to receive one of three collection devices: (i) standard NPA, (ii) NW using a 30ml ear-syringe bulb (NWb), or (iii) NW using a 5ml syringe (NWs) with a shortened (9cm) 8FG tube. Assessment focused on ease of procedure, acceptability to parent and child, and adequacy of epithelial cell yield for immunofluorescence testing. A short questionnaire was delivered.

SETTING

Paediatric Ward of Kilifi District Hospital, (KDH) Kilifi, Kenya.

SUBJECTS

Any child admitted with ARI between 5th November 2001 and 24th January 2002.

RESULTS

Children recruited into NPA, NWb and NWs procedures numbered 62, 76 and 62, respectively (median age of 8 months). A higher proportion of children receiving NWb did not cry (43%) compared to those receiving NPA (13%) (OR 5.18; 95% CI 2.17-12.4). Whereas 66% of mothers were comfortable with NPA procedure, the proportion for NWs was 40% (OR 0.341; 0.163-0.714). Acceptability to the operator was marginally lower for NWs than NPA (79% vs 92%, OR 0.324, 0.107-0.974). For other observations there were no differences between the procedures; these were length of procedure (98% <5mins), the acceptable time interval for repeating a procedure (64% <1 week), comparison with blood collection (77% preferred the nasal specimen) and slides with 20 or more epithelial cells (overall 82%).

CONCLUSION

Nasal washing methods provide simple and effective alternatives to NPA, with the NWb being the more acceptable, and have merits for use in resource poor and home settings.

Associations between nasal torquetenovirus load and spirometric indices in children with asthma

Fifty-nine children with well-controlled, mild to moderate persistent asthma were studied for the presence and load of torquetenovirus (TTV) in nasal fluid. Rates of TTV positivity and mean nasal TTV loads were not dissimilar to those observed in the general population and in a group of 30 age- and residence-matched healthy control children without a history of asthmatic disease. However, in the children with asthma, 3 important indices of lung function--forced expiratory flow (FEF) in which 25% and 75% of forced vital capacity (FVC) is expired (FEF(25%-75%)), forced expiratory volume in 1 s/FVC, and FEF(25%-75%)/FVC--showed an inverse correlation with nasal TTV load. Furthermore, signs of reduced airflow were more frequent in the children with asthma who had high nasal TTV loads (> or =6 log(10) DNA copies/mL of nasal fluid) than they were in those who had low nasal TTV loads (<6 log(10) DNA copies/mL of nasal fluid), despite similar therapy regimens. In contrast, the control children showed no associations between nasal TTV load and the spirometric indices. Levels of eosinophil cationic protein in sputum were also greater in the children with asthma who had higher nasal viral burdens than they were in those who had lower nasal viral burdens. These findings are the first report of TTV infection status in children with asthma and suggest that TTV might be a contributing factor in the lung impairment caused by this condition.

Improved outcome for children with disseminated adenoviral infection following allogeneic stem cell transplantation

Adenovirus (AdV) infections are a frequent cause of morbidity and mortality following allogeneic stem cell transplantation (SCT), and disseminated infection is associated with high mortality, particularly in paediatric SCT. Here, we describe an approach to reduce mortality from adenoviraemia by combining prospective monitoring for the occurrence of adenoviraemia using a sensitive polymerase chain reaction method, early antiviral therapy and prompt withdrawal of immunosuppression. A total of 155 consecutive paediatric SCT procedures were prospectively monitored, of which 113 (73%) transplants involved donors other than matched siblings and 126 (83%) employed T-cell depletion. Adenoviraemia was detected in 26/155 (17%) transplants and developed exclusively in patients who had received T-cell-depleted grafts. Withdrawal of immunosuppression coupled with early antiviral therapy led to resolution of adenoviraemia in 19/26 (81%) patients with only five patients succumbing to disseminate AdV infection. Survival from adenoviraemia was associated with lymphocyte recovery to above 0.3x10(9)/l. Mortality was closely linked with the absence of lymphocyte recovery because of profound T-cell depletion of the graft with CD34+ magnetic-activated cell sorting. Mortality from disseminated AdV infection was 5/26 (19%) in this study, which is significantly lower than previously reported.

[Detection of SARS-coronavirus in both human and animals by RT-PCR]

OBJECTIVE

To find the most suitable RT-PCR detection method for SARS-Coronavirus (SARS-CoV) detection in both human and animals, and to study the source of SARS virus by investigating the condition of virus carried by wild, domestic animals and animals sold in market.

METHODS

350 throat washes of confirmed, suspected and observed SARS cases were tested by TaqMan and molecular beacon fluorescence RT-PCR methods. 386 animals with 442 nasal-throat swabs, fecal swabs of animals and cell cultured were detected by TaqMan method and conventional RT-PCR method.

RESULTS

10 positive were detected from 41 SARS clinical confirmed cases (24.39%). The results of TaqMan and molecular beacon are basically coincident with the coincident rate of 88.89%. 18 cell cultures with CPE were detected and find 16 positive, among which, 14 were civet cats (87.5%). The detecting results of animal samples from Dongmen Market (Shenzhen) and other markets and farms in peripheral areas show that: the total positive rate of 4 kinds of wild animal (civet cat, raccoon dog, hog-badge and Chinese ferret-badge) is 39.02% , which has an significant difference (P < 0.01) compared with the positive rate of other animals as 0. The positive rate of PCR for nasal and fecal swabs from 109 major wild animals is 44.04%, but the positive rate of 145 wild live-animals is 0.

CONCLUSION

TaqMan and molecular beacon PCR methods both can be used in SARS detection.The results could support the hypothesis that animals (especially civet cat) could carry SARS virus.

Transmission of bovine viral diarrhea virus 1b to susceptible and vaccinated calves by exposure to persistently infected calves

Bovine viral diarrhea virus (BVDV) persistently infected (PI) calves represent significant sources of infection to susceptible cattle. The objectives of this study were to determine if PI calves transmitted infection to vaccinated and unvaccinated calves, to determine if BVDV vaccine strains could be differentiated from the PI field strains by subtyping molecular techniques, and if there were different rates of recovery from peripheral blood leukocytes (PBL) versus serums for acutely infected calves. Calves PI with BVDV1b were placed in pens with nonvaccinated and vaccinated calves for 35 d. Peripheral blood leukocytes, serums, and nasal swabs were collected for viral isolation and serology. In addition, transmission of Bovine herpes virus 1 (BHV-1), Parainfluenza-3 virus (PI-3V), and Bovine respiratory syncytial virus (BRSV) was monitored during the 35 d observation period. Bovine viral diarrhea virus subtype 1b was transmitted to both vaccinated and nonvaccinated calves, including BVDV1b seronegative and seropositive calves, after exposure to PI calves. There was evidence of transmission by viral isolation from PBL, nasal swabs, or both, and seroconversions to BVDV1b. For the unvaccinated calves, 83.2% seroconverted to BVDV1b. The high level of transmission by PI calves is illustrated by seroconversion rates of nonvaccinated calves in individual pens: 70% to 100% seroconversion to the BVDV1b. Bovine viral diarrhea virus was isolated from 45 out of 202 calves in this study. These included BVDV1b in ranch and order buyer (OB) calves, plus BVDV strains identified as vaccinal strains that were in modified live virus (MLV) vaccines given to half the OB calves 3 d prior to the study. The BVDV1b isolates in exposed calves were detected between collection days 7 and 21 after exposure to PI calves. Bovine viral diarrhea virus was recovered more frequently from PBL than serum in acutely infected calves. Bovine viral diarrhea virus was also isolated from the lungs of 2 of 7 calves that were dying with pulmonary lesions. Two of the calves dying with pneumonic lesions in the study had been BVDV1b viremic prior to death. Bovine viral diarrhea virus 1b was isolated from both calves that received the killed or MLV vaccines. There were cytopathic (CP) strains isolated from MLV vaccinated calves during the same time frame as the BVDV1b isolations. These viruses were typed by polymerase chain reaction (PCR) and genetic sequencing, and most CP were confirmed as vaccinal origin. A BVDV2 NCP strain was found in only 1 OB calf, on multiple collections, and the calf seroconverted to BVDV2. This virus was not identical to the BVDV2 CP 296 vaccine strain. The use of subtyping is required to differentiate vaccinal strains from the field strains. This study detected 2 different vaccine strains, the BVDV1b in PI calves and infected contact calves, and a heterologous BVDV2 subtype brought in as an acutely infected calf. The MLV vaccination, with BVDV1a and BVDV2 components, administered 3 d prior to exposure to PI calves did not protect 100% against BVDV1b viremias or nasal shedding. There were other agents associated with the bovine respiratory disease signs and lesions in this study including Mannheimia haemolytica, Mycoplasma spp., PI-3V, BRSV, and BHV-1.

Evaluation of PCR testing of ethanol-fixed nasal swab specimens as an augmented surveillance strategy for influenza virus and adenovirus identification

Viral culture isolation has been widely accepted as the "gold standard" for laboratory confirmation of viral infection; however, it requires ultralow temperature specimen storage. Storage of specimens in ethanol at room temperature could expand our ability to conduct active surveillance and retrospective screenings of viruses with rapid and inexpensive real-time PCR tests, including isolates from remote regions where freezing specimens for culture is not feasible. Molecular methods allow for rapid identification of viral pathogens without the need to maintain viability. We hypothesized that ethanol, while inactivating viruses, can preserve DNA and RNA for PCR-based methods. To evaluate the use of ethanol-stored specimens for augmenting surveillance for detection of influenza viruses A and B and adenoviruses (AdV), paired nasal swab specimens were collected from 384 recruits with febrile respiratory illness at Fort Jackson, S.C., in a 2-year study. One swab was stored at ambient temperature in 100% ethanol for up to 6 months, and the other swab was stored at -70 degrees C in viral medium. For viral detection, frozen specimens were cultured for a variety of respiratory viruses, and ethanol-fixed specimens were tested with TaqMan (TM) probe and LightCycler SYBR green (SG) melting curve assays with at least two different PCR targets for each virus. The sensitivities of the TM and SG assays on specimens stored in ethanol for 1 month were 75% and 58% for influenza A, 89% and 67% for influenza B, and 93 to 98% and 57% for AdV, respectively. Lower specificities of the real-time assays corresponded to the increased detection of PCR-positive but culture-negative specimens. Influenza virus RNA was detected as well or better after 6 months of storage in ethanol.

Protection against influenza virus infection by intranasal administration of hemagglutinin vaccine with chitin microparticles as an adjuvant

Chitin in the form of microparticles (chitin microparticles, CMP) has been demonstrated to be a potent stimulator of macrophages, promoting T-helper-1 (Th1) activation and cytokine response. In order to examine the mucosal adjuvant effect of CMP co-administered with influenza hemagglutinin (HA) vaccine against influenza infection, CMP were intranasally co-administered with influenza HA vaccine prepared from PR8 (H1N1) virus. Inoculation of the vaccine with CMP induced primary and secondary anti-HA IgA responses in the nasal wash and anti-HA IgG responses in the serum, which were significantly higher than those of nasal vaccination without CMP, and provided a complete protection against a homologous influenza virus challenge in the nasal infection influenza model. In addition, CMP-based immunization using A/Yamagata (H1N1) and A/Guizhou (H3N2) induced PR8 HA-reactive IgA in the nasal washes and specific-IgG in the serum. The immunization with A/Yamagata and CMP resulted in complete protection against a PR8 (H1N1) challenge in A/Yamagata (H1N1)-vaccinated mice, while that with A/Guizhou (H3N2) and CMP exhibited a 100-fold reduction of nasal virus titer, demonstrating the cross-protective effect of CMP and influenza vaccine. It is suggested that CMP provide a safe and effective adjuvant for nasal vaccination with inactivated influenza vaccine.

Virological surveillance of influenza-like illness in the community using PCR and serology

Background: Surveillance of winter respiratory viral illness has been carried out for nearly 30 years using a clinical diagnosis by general practitioners as part of the Scottish Sentinel General Practice (SSGP) network. Contemparaneous laboratory diagnosis has not been available previously. Objectives: To assess the proportion of influenza-like illness (ILI) attributable to influenza, respiratory syncytial virus (RSV) and picornavirus infection during the winter season. To compare the influenza PCR data with serology of paired blood samples. Study design: Combined nose and throat swabs, from patients with ILI attending 15 general practices across Scotland, were submitted to the laboratory in virus PCR sample solution (VPSS). The extracted nucleic acid was tested using a multiplex reverse-transcription polymerase chain reaction (RT-PCR) assay. Serological analysis was performed on paired serum samples using complement fixation assays. The rate of influenza virus positivity was compared with reports of ILI obtained from the SSGP network. Results: Of 240 samples received at the laboratory, 132 (55%) were PCR positive for influenza A virus. There were nine (3.8%) picornavirus and three (1.2%) RSV PCR positives, two (0.8%) were dual influenza A/picornavirus infections. Ninety four (39.2%) were negative for all viruses tested. Results on paired sera from 89 patients showed a rising titre to influenza A in 48 of the 57 PCR positive samples (84.2%). One PCR negative patient displayed a significant rising titre to influenza A. Virological data paralleled the SSGP data but was available at least a week earlier. Conclusions: Influenza A infection was detected in the majority of patients with ILI; picornavirus infection was also shown to be an important cause of illness. PCR is a rapid and sensitive method for respiratory virus surveillance. Serology is slow, insensitive and difficult to interpret at low titres.

Canine herpesvirus-1 (CHV-1): clinical, serological and virological patterns in breeding colonies

Canine herpesvirus-1 (CHV-1) is presumed to be enzootic in the dog population and is associated with reproductive disorders and neonatal mortality. To advise dog breeders towards an effective management of CHV-1 infected colonies, 27 breeding bitches were studied during one reproductive cycle in field conditions: the effect of cycle stage, kennel size, initial antibody titre, mating and gestation on serologic and viral excretion patterns was evaluated, while the association between reproductive disorders and CHV-1 antibody titres and viral excretion was also analysed. All initially seronegative bitches seroconverted, while 40% of the initially seropositive bitches became seronegative at one or two occasions. No difference in antibody patterns was observed between mated and unmated bitches. Of the mated bitches, 46% experienced infertility, foetal resorption or mummification. No difference in antibody patterns was observed depending on the occurrence of reproductive disorders even if a decrease in antibody titres during early or late-di-oestrus was often present. Significantly higher titres were observed at all cycle stages in large kennels. None of the vaginal and nasal samples or buffy coats tested positive for CHV-1 DNA. The mixed image of clinical and sub-clinical carriage in this study demonstrated CHV-1 has a complex and difficult to predict clinical behavior. Preventive management with vaccination of reproducing bitches in kennels with reproductive disorders should therefore be advised.

Influenza virological surveillance in children: the use of the QuickVue rapid diagnostic test

New rapid diagnostic methods are needed to identify influenza infections to improve virological surveillance usually undertaken with conventional time-consuming, complex, and even expensive laboratory methods. Another reason for using a rapid test is to avoid inappropriate therapy, particularly in children, where use of antibiotics inappropriately and high influenza-related rates of hospitalisation are described. During two winter seasons, the performance of the QuickVue Influenza test (QV) was evaluated in children under 14 presenting with influenza like illness, and compared the results with those obtained from sentinel network surveillance using standard protocols for the sample collection and the laboratory analysis by virus culture and reverse transcription-polymerase chain reaction (RT-PCR). During the first influenza season (2000/2001), 22 paediatricians collected one nose- and one throat-swab from each of the 586 children 0-6 years old recruited in the study. The QV test was carried out in the physician's office by primary care staff on the nose swab material. When compared with virus culture of the throat swab, the QV test had a sensitivity of 36.5%. In the following 2001/2002-influenza season, the performance of the QV test as a rapid laboratory screening assay was assessed. 342 children aged 0-14 years were enrolled with only one throat swab collected from each patient and sent to the laboratory where the QV, virus culture, and RT-PCR tests were performed. The results showed a better sensitivity (54.5%) of the test in comparison with virus culture and RT-PCR assays. The data indicate that rapid QV testing in the physician office setting, using these easily obtained samples, may be too insensitive to be useful for surveillance and for immediate clinical management of children presenting with influenza-like illness. Nevertheless, the QV test may be a valuable diagnostic tool if used in laboratory, as a rapid screening test.

Surveillance of childhood influenza virus infection: what is the best diagnostic method to use for archival samples?

Despite the clinical importance of influenza virus in pediatric respiratory infections, the optimal set of diagnostic tests to use when conducting studies using archival samples is not clear. In this study, we compared diagnostic tests for influenza virus in 75 children younger than 5 years of age who presented with symptomatic respiratory infection during one of four influenza seasons, had negative viral cultures for other respiratory pathogens, and had both an archival nasal aspirate obtained at the time of illness and serology spanning that influenza season. For all eligible children, we compared the results of viral culture performed at the time of collection with serology and PCR of archival nasal aspirates. Using real-time viral culture as the "gold standard," the test characteristics of PCR of archival nasal aspirates (sensitivity, 82%; specificity, 100%) and serology (sensitivity, 82%; specificity, 87%) were similar. The relatively low sensitivity of PCR of archival nasal samples in this study compared to that of PCR of fresh samples in a previous study suggests that RNA degradation occurred despite storage of the specimens at -70 degrees C. RNA degradation would also explain why only 11 (52%) of 21 archival nasal samples that had positive influenza virus cultures at the time of collection had positive repeat cultures in the summer of 2000. Thus, in archival specimens stored at -70 degrees C, PCR was more sensitive than viral culture. However, testing of fresh specimens had the highest yield in this study. Studies of optimal methods for specimen storage are needed.

Sequential switching of DNA polymerase and thymidine kinase-mediated HSV-1 drug resistance in an immunocompromised child

Sequential herpes simplex virus type 1 (HSV-1) isolates were obtained from a paediatric haematopoietic stem cell transplant (HSCT) patient who received prolonged therapy with acyclovir (ACV) followed by foscarnet (PFA) and topical cidofovir (HPMPC) for severe persistent mucocutaneous HSV-1 infection. The isolates were retrospectively studied for drug resistance. The first resistant isolate associated with clinical failure of antiviral therapy emerged 44 days post-ACV treatment initiation. Susceptibility testing revealed an ACV-resistant HSV strain that demonstrated cross resistance to PFA in the absence of any previous PFA treatment. The observed cross resistance was conferred by a single amino acid substitution, Ser724Asn, in the HSV DNA polymerase (DNA pol) gene. During the subsequent course of ACV therapy, the ACV/PFA-cross-resistant isolates were replaced by ACV-resistant, PFA-sensitive isolates. These isolates carried no DNA pol mutations, but had an Arg163His substitution in the thymidine kinase gene. Upon subsequent switching of antiviral therapy from ACV to PFA, the original ACV/PFA-cross-resistant DNA pol mutant re-appeared. Our study shows the emergence of different drug-resistant HSV variants during ongoing, unchanged ACV therapy. Furthermore, a rapid re-selection of the original resistant variant was observed after switch. For optimal antiviral management of HSV infections in HSCT recipients, therapeutic decisions should be guided by drug susceptibility results whenever therapeutic failure is observed and/or when changes in antiviral treatment are considered.

New point of care test is highly specific but less sensitive for influenza virus A and B in children and adults

The importance of rapid diagnosis of influenza has increased with the availability of neuraminidase inhibitors, which need to be commenced within 48 hr of symptom onset. Furthermore, the recent development of influenza-like clinical syndromes with novel aetiologies (severe acute respiratory syndrome, SARS) has increased the need for rapid and accurate near-patient diagnosis. A new, modified point of care (POC) diagnostic test (ZstatFlu) was assessed on 469 nasopharyngeal aspirates (NPAs) and 260 nose/throat swabs (TS) taken from children and adults. The test was specific (77-98%) for all specimen types for influenza virus A and B, depending upon incubation conditions. However, it was less sensitive, detecting 65-77% of specimens confirmed as positive on culture, direct immunofluorescence or PCR testing. A positive test is useful, for both directing initiation of therapy in the clinician's office, and making a positive diagnosis of influenza in patients with influenza-like clinical syndromes.

Isolation and characterization of viruses related to the SARS coronavirus from animals in southern China

A novel coronavirus (SCoV) is the etiological agent of severe acute respiratory syndrome (SARS). SCoV-like viruses were isolated from Himalayan palm civets found in a live-animal market in Guangdong, China. Evidence of virus infection was also detected in other animals (including a raccoon dog, Nyctereutes procyonoides) and in humans working at the same market. All the animal isolates retain a 29-nucleotide sequence that is not found in most human isolates. The detection of SCoV-like viruses in small, live wild mammals in a retail market indicates a route of interspecies transmission, although the natural reservoir is not known.

Induction of influenza type A virus-specific resistance by immunization of mice with a synthetic multiple antigenic peptide vaccine that contains ectodomains of matrix protein 2

Matix protein 2 (M2) is a transmembrane protein of influenza type A virus. It contains a 23 aa long ectodomain (M2e) that is highly conserved amongst human influenza type A viruses. M2e-specific antibodies have been shown to restrict virus growth in vitro and in vivo and thus have the potential of providing cross-reactive resistance to influenza type A virus infection. We attempted to induce M2e-specific protection with synthetic multiple antigen peptide (MAP) constructs that contained covalently linked M2e- and Th-determinant peptides. Mice, vaccinated twice by the intranasal (i.n.) route with adjuvanted M2e-MAPs exhibited significant resistance to virus replication in all sites of the respiratory tract. Compared to mice primed by two consecutive heterosubtypic infections, resistance was of similar strength in nasal and tracheal tissue but lower in pulmonary tissue. Importantly, the protection in M2e-MAP- and infection-immunized mice appeared to be mediated by distinct immune mechanisms. This suggests that stronger protection may be achievable by combining both protective activities.

TT virus in the nasal secretions of children with acute respiratory diseases: relations to viremia and disease severity

The natural history and pathogenic potential of the recently identified TT virus (TTV) are currently a matter of intensive investigation. In an attempt to shed some light on these issues, nasal and blood specimens of 1- to 24-month-old children hospitalized with a clinical diagnosis of acute respiratory disease (ARD) were examined for the presence, load, and genetic characteristics of TTV. The results have indicated that at least in young children, the respiratory tract not only represents a route by which abundant TTV can be shed into the environment but also may be a site of primary infection and continual replication. Although we found no compelling evidence that TTV was the direct cause of ARD in some of the children studied, the average loads of TTV were considerably higher in patients with bronchopneumonia (BP) than in those with milder ARD, raising interesting questions about the pathophysiological significance of TTV at this site. Furthermore, group 4 TTV was detected almost exclusively in children with BP.

Nasal swab versus nasopharyngeal aspirate for isolation of respiratory viruses

To determine the usefulness of nasal swabs as a simple method for detection of respiratory viruses, we compared nasal swabs and nasopharyngeal aspirates obtained at the same time from the opposite nostrils of 230 children with upper respiratory infection. The sensitivity of nasal swabs was comparable to that of nasopharyngeal aspirates for the detection of all major respiratory viruses except respiratory syncytial virus.

PKR protection against intranasal vesicular stomatitis virus infection is mouse strain dependent

The interferon-induced antiviral state is mediated by interferon-stimulated genes that are upregulated in concert after stimulation by type I interferons. Because so many viruses encode strategies to inactivate the interferon-inducible double-stranded RNA (dsRNA)-dependent protein kinase PKR, this protein is likely to be a major player in antiviral defense. Here we demonstrate the increased susceptibility of PKR-/- animals to vesicular stomatitis virus (VSV) by the intranasal route, but also demonstrate that the protective effects of PKR are mouse strain dependent. We have found the difference between wild-type-BALB/c and 129SvEv animals to be on the order of 5 logs, with high levels of virus present in the lungs of BALB/c but not 129SvEv animals. To evaluate the sensitivity of PKR-/- mice to VSV clearly, the PKR mutation was bred onto the resistant 129SvEv background. The increased sensitivity of PKR-/- mice, compared to PKR+/+ strain-matched controls, is on the order of 10-fold as measured by median lethal dose (LD50). PKR-/- 129 mice support VSV replication in the lung unlike controls. While this result clearly demonstrates an important role for PKR in protection against VSV infection of the lung, it also underlines the importance of other host factors in containing a viral infection.