Marek J. Slomka

Replication, Pathogenesis and Transmission of Pandemic (H1N1) 2009 Virus in Non-Immune Pigs

The declaration of the human influenza A pandemic (H1N1) 2009 (H1N1/09) raised important questions, including origin and host range [1], [2]. Two of the three pandemics in the last century resulted in the spread of virus to pigs (H1N1, 1918; H3N2, 1968) with subsequent independent establishment and evolution within swine worldwide [3]. A key public and veterinary health consideration in the context of the evolving pandemic is whether the H1N1/09 virus could become established in pig populations [4]. We performed an infection and transmission study in pigs with A/California/07/09. In combination, clinical, pathological, modified influenza A matrix gene real time RT-PCR and viral genomic analyses have shown that infection results in the induction of clinical signs, viral pathogenesis restricted to the respiratory tract, infection dynamics consistent with endemic strains of influenza A in pigs, virus transmissibility between pigs and virus-host adaptation events. Our results demonstrate that extant H1N1/09 is fully capable of becoming established in global pig populations. We also show the roles of viral receptor specificity in both transmission and tissue tropism. Remarkably, following direct inoculation of pigs with virus quasispecies differing by amino acid substitutions in the haemagglutinin receptor-binding site, only virus with aspartic acid at position 225 (225D) was detected in nasal secretions of contact infected pigs. In contrast, in lower respiratory tract samples from directly inoculated pigs, with clearly demonstrable pulmonary pathology, there was apparent selection of a virus variant with glycine (225G). These findings provide potential clues to the existence and biological significance of viral receptor-binding variants with 225D and 225G during the 1918 pandemic [5].

Identification of Sensitive and Specific Avian Influenza Polymerase Chain Reaction Methods Through Blind Ring Trials Organized in the European Union

Abstract Many different polymerase chain reaction (PCR) protocols have been used for detection and characterization of avian influenza (AI) virus isolates, mainly in research settings. Blind ring trials were conducted to determine the most sensitive and specific AI PCR protocols from a group of six European Union (EU) laboratories. In part 1 of the ring trial the laboratories used their own methods to test a panel of 10 reconstituted anonymized clinical specimens, and the best methods were selected as recommended protocols for part 2, in which 16 RNA specimens were tested. Both panels contained H5, H7, other AI subtypes, and non-AI avian pathogens. Outcomes included verification of 1) generic AI identification by highly sensitive and specific M-gene real-time PCR, and 2) conventional PCRs that were effective for detection and identification of H5 and H7 viruses. The latter included virus pathotyping by amplicon sequencing. The use of recommended protocols resulted in improved results among all six laboratories in part 2, reflecting increased sensitivity and specificity. This included improved H5/H7 identification and pathotyping observed among all laboratories in part 2. Details of these PCR methods are provided. In summary, this study has contributed to the harmonization of AI PCR protocols in EU laboratories and influenced AI laboratory contingency planning following the first European reports of H5N1 highly pathogenic AI during autumn 2005.

Real time reverse transcription (RRT)-polymerase chain reaction (PCR) methods for detection of pandemic (H1N1) 2009 influenza virus and European swine influenza A virus infections in pigs.

Please cite this paper as: Slomka et al. (2010) Real time reverse transcription (RRT)‐polymerase chain reaction (PCR) methods for detection of pandemic (H1N1) 2009 influenza virus and European swine influenza A virus infections in pigs. Influenza and Other Respiratory Viruses 4(5), 277–293.

18S rRNA is a reliable normalisation gene for real time PCR based on influenza virus infected cells

BackgroundOne requisite of quantitative reverse transcription PCR (qRT-PCR) is to normalise the data with an internal reference gene that is invariant regardless of treatment, such as virus infection. Several studies have found variability in the expression of commonly used housekeeping genes, such as beta-actin (ACTB) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), under different experimental settings. However, ACTB and GAPDH remain widely used in the studies of host gene response to virus infections, including influenza viruses. To date no detailed study has been described that compares the suitability of commonly used housekeeping genes in influenza virus infections. The present study evaluated several commonly used housekeeping genes [ACTB, GAPDH, 18S ribosomal RNA (18S rRNA), ATP synthase, H+ transporting, mitochondrial F1 complex, beta polypeptide (ATP5B) and ATP synthase, H+ transporting, mitochondrial Fo complex, subunit C1 (subunit 9) (ATP5G1)] to identify the most stably expressed gene in human, pig, chicken and duck cells infected with a range of influenza A virus subtypes.ResultsThe relative expression stability of commonly used housekeeping genes were determined in primary human bronchial epithelial cells (HBECs), pig tracheal epithelial cells (PTECs), and chicken and duck primary lung-derived cells infected with five influenza A virus subtypes. Analysis of qRT-PCR data from virus and mock infected cells using NormFinder and BestKeeper software programmes found that 18S rRNA was the most stable gene in HBECs, PTECs and avian lung cells.ConclusionsBased on the presented data from cell culture models (HBECs, PTECs, chicken and duck lung cells) infected with a range of influenza viruses, we found that 18S rRNA is the most stable reference gene for normalising qRT-PCR data. Expression levels of the other housekeeping genes evaluated in this study (including ACTB and GPADH) were highly affected by influenza virus infection and hence are not reliable as reference genes for RNA normalisation.

Validated RealTime reverse transcriptase PCR methods for the diagnosis and pathotyping of Eurasian H7 avian influenza viruses.

Background  Avian influenza (AI) caused by H7 AI viruses (AIVs) of both low pathogenicity (LP) and high pathogenicity (HP) are notifiable poultry diseases.

First reported incursion of highly pathogenic notifiable avian influenza A H5N1 viruses from clade 2.3.2 into European poultry.

This study reports the first incursion into European poultry of H5N1 highly pathogenic notifiable avian influenza A (HPNAI) viruses from clade 2.3.2 that affected domestic poultry and wild birds in Romania and Bulgaria, respectively. Previous occurrences in Europe of HPNAI H5N1 in these avian populations have involved exclusively viruses from clade 2.2. This represents the most westerly spread of clade 2.3.2 viruses, which have shown an apparently expanding range of geographical dispersal since mid-2009 following confirmation of infections in wild waterfowl species in Mongolia and Eastern Russia. During March 2010, AI infection was suspected at post-mortem examination of two hens from two backyard flocks in Tulcea Country, Romania. HPNAI of H5N1 subtype was confirmed by reverse transcription polymerase chain reaction (RT-PCR). A second outbreak was confirmed 2 weeks later by RT-PCR, affecting all hens from another flock located 55 km east of the first cluster. On the same day, an H5N1 HPNAI virus was detected from a pooled tissue sample collected from a dead Common Buzzard found on the Black Sea coast in Bulgaria. Detailed genetic characterization of the haemagglutinin gene revealed the cleavage site of the isolates to be consistent with viruses of high pathogenicity belonging to clade 2.3.2 of the contemporary Eurasian H5N1 lineage. Viruses from a clade other than 2.2 have apparently spread to wild birds, with potential maintenance and spread through such populations. Whilst the scale of threat posed by the apparent westward spread of the clade 2.3.2 viruses remains uncertain, ongoing vigilance for clinical signs of disease as part of existing passive surveillance frameworks for AI, and the prompt reporting of suspect cases in poultry is advised.

Rapid death of duck cells infected with influenza: a potential mechanism for host resistance to H5N1.

Aquatic birds are the natural reservoir for most subtypes of influenza A, and a source of novel viruses with the potential to cause human pandemics, fatal zoonotic disease or devastating epizootics in poultry. It is well recognised that waterfowl typically show few clinical signs following influenza A infection, in contrast, terrestrial poultry such as chickens may develop severe disease with rapid death following infection with highly pathogenic avian influenza. This study examined the cellular response to influenza infection in primary cells derived from resistant (duck) and susceptible (chicken) avian hosts. Paradoxically, we observed that duck cells underwent rapid cell death following infection with low pathogenic avian H2N3, classical swine H1N1 and ‘classical’ highly pathogenic H5N1 viruses. Dying cells showed morphological features of apoptosis, increased DNA fragmentation and activation of caspase 3/7. Following infection of chicken cells, cell death occurred less rapidly, accompanied by reduced DNA fragmentation and caspase activation. Duck cells produced similar levels of viral RNA but less infectious virus, in comparison with chicken cells. Such rapid cell death was not observed in duck cells infected with a contemporary Eurasian lineage H5N1 fatal to ducks. The induction of rapid death in duck cells may be part of a mechanism of host resistance to influenza A, with the loss of this response leading to increased susceptibility to emergent strains of H5N1. These studies provide novel insights that should help resolve the long‐standing enigma of host–pathogen relationships for highly pathogenic and zoonotic avian influenza.

Rapid PCR-Based Molecular Pathotyping of H5 and H7 Avian Influenza Viruses

ABSTRACT While the majority of avian influenza virus (AIV) subtypes are classified as low-pathogenicity avian influenza viruses (LPAIV), the H5 and H7 subtypes have the ability to mutate to highly pathogenic avian influenza viruses (HPAIV) in poultry and therefore are the etiological agents of notifiable AIV (NAIV). It is of great importance to distinguish HPAIV from LPAIV variants during H5/H7 outbreaks and surveillance. To this end, a novel and fast strategy for the molecular pathotyping of H5/H7 AIVs is presented. The differentiation of the characteristic hemagglutinin (HA) protein cleavage sites (CSs) of HPAIVs and LPAIVs is achieved by a novel PCR method where the samples are interrogated for all existing CSs with a 484-plex primer mixture directly targeting the CS region. CSs characteristic for HP or LP H5/H7 viruses are distinguished in a seminested duplex real-time PCR format using plexor fluorogenic primers. Eighty-six laboratory isolates and 60 characterized NAIV-positive clinical specimens from poultry infected with H5/H7 both experimentally and in the field were successfully pathotyped in the validation. The method has the potential to substitute CS sequencing in the HA gene for the determination of the molecular pathotype, thereby providing a rapid means to acquire additional information concerning NAIV outbreaks, which may be critical to their management. The new assay may be extended to the LP/HP differentiation of previously unknown H5/H7 isolates. It may be considered for integration into surveillance and control programs in both domestic and wild bird populations.

Role of Real-Time RT-PCR Platform Technology in the Diagnosis and Management of Notifiable Avian Influenza Outbreaks: Experiences in Great Britain

Abstract Diagnosis and management of avian influenza outbreaks now include the use of validated real-time reverse transcription PCR (RRT-PCR) methods in many countries, including all member states of the European Union. Two outbreaks in poultry of notifiable avian influenza (H5 and H7 subtypes) that occurred in Great Britain during 2007 will serve as examples in which RRT-PCR demonstrated its value in 1) rapid diagnosis and confirmation of disease by sensitive and specific laboratory testing of samples derived from the index cases and 2) high-volume, rapid testing of surveillance samples. The two poultry outbreaks followed the incursion of a H7N2 low-pathogenicity notifiable avian influenza (LPNAI) virus (May–June 2007) and a Eurasian lineage H5N1 highly pathogenic notifiable avian influenza (HPNAI) virus (November 2007). Coupled with the use of high-throughput, robotic RNA extraction methods, a total of approximately 9300 and 20,300 field samples were tested by appropriate, validated RRT-PCR assays during the 4- and 5-wk duration of the H7N2 LPNAI and H5N1 HPNAI outbreaks, respectively. Fundamental features of the validated RRT-PCR assays used included their high degree of sensitivity, specificity, and rapidity, attributes that were invaluable in providing timely and accurate information for notifiable AI outbreak management.

Challenges for accurate and prompt molecular diagnosis of clades of highly pathogenic avian influenza H5N1 viruses emerging in Vietnam

Forty-six chickens and 48 ducks were sampled from four Vietnamese poultry premises in 2009 infected with H5N1 highly pathogenic avian influenza (HPAI) clade 2.3.2 and 2.3.4 viruses, which also differed by cleavage site (CS) sequences in their haemagglutinin (HA) genes. All clinical specimens (n=282), namely tracheal and cloacal swabs plus feathers, were tested by five Eurasian reverse-transcriptase AI RealTime polymerase chain reaction (RRT-PCR) methods. Bayesian modelling showed similar high sensitivity for the validated H5 HA2 RRT-PCR and a new modified M-gene RRT-PCR that utilizes lyophilized reagents. Both were more sensitive than the validated “wet” M-gene RRT-PCR. Another RRT-PCR, which targeted the H5-gene CS region, was effective for clade 2.3.4 detection, but severely compromised for clade 2.3.2 viruses. Reduced sensitivity of the H5 CS and “wet” M-gene RRT-PCRs correlated with mismatches between the target and the primer and/or probe sequences. However, the H5 HA2 RRT-PCR sensitively detected both clade 2.3.2 and 2.3.4 viruses, and agreed with N1 RRT-PCR results. Feather testing from diseased chicken and duck flocks by AI RRT-PCRs resulted in the most sensitive identification of H5N1 HPAI-infected birds. Evolution of new H5N1 HPAI clades remains a concern for currently affected Asian countries, but also for more distant regions where it is important to be prepared for new incursions of H5N1 HPAI viruses. Genetic evidence for adamantane resistance and sensitivity was also observed in isolates from both clades.