Identification of Rare PB2-D701N Mutation from a Patient with Severe Influenza: Contribution of the PB2-D701N Mutation to the Pathogenicity of Human Influenza

Several amino acid changes have been previously implicated in adaptation of avian influenza viruses to human hosts, among them the D701N change in the PB2 polymerase subunit that also is the main determinant of avian virus pathogenesis in animal models. However, previous studies using recombinant viruses did not provide conclusive information of the contribution of this PB2 residue to pathogenicity in human influenza virus strains. We identified this mutation in an A(H1N1)pdm09-like human influenza virus isolated from an infected patient with pneumonia and acute respiratory failure, admitted to the intensive care unit. An exhaustive search has revealed PB2-D701 as a highly conserved position in all available H1N1 human virus sequences in NCBI database, showing a very low prevalence of PB2-D701N change. Presence of PB2-701N amino acid correlates with severe or fatal outcome in those scarce cases with known disease outcome of the infection. In these patients, the residue PB2-701N may contribute to pathogenicity as it was previously reported in humans infected with avian viruses. This study helps to clarify a debate that has arisen regarding the role of PB2-D701N in human influenza virus pathogenicity.

Clinical response to pandemic H1N1 influenza virus from a fatal and mild case in ferrets

Background

The majority of pandemic 2009 H1N1 (A(H1N1)pdm09) influenza virus (IV) caused mild symptoms in most infected patients, however, a greater rate of severe disease was observed in healthy young adults and children without co-morbid conditions. The purpose of this work was to study in ferrets the dynamics of infection of two contemporary strains of human A(H1N1)pdm09 IV, one isolated from a patient showing mild disease and the other one from a fatal case.

Methods

Viral strains isolated from a patient showing mild disease-M (A/CastillaLaMancha/RR5661/2009) or from a fatal case-F (A/CastillaLaMancha/RR5911/2009), both without known comorbid conditions, were inoculated in two groups of ferrets and clinical and pathological conditions were analysed.

Results

Mild to severe clinical symptoms were observed in animals from both groups. A clinical score distribution was applied in which ferrets with mild clinical signs were distributed on a non-severe group (NS) and ferrets with severe clinical signs on a severe group (S), regardless of the virus used in the infection. Animals on S showed a significant decrease in body weight compared to animals on NS at 4 to 7 days post-infection (dpi). Clinical progress correlated with histopathological findings. Concentrations of haptoglobin (Hp) and serum amyloid A (SAA) increased on both groups after 2 dpi. Clinically severe infected ferrets showed a stronger antibody response and higher viral titres after infection (p = 0.001).

Conclusions

The severity in the progress of infection was independent from the virus used for infection suggesting that the host immune response was determinant in the outcome of the infection. The diversity observed in ferrets mimicked the variability found in the human population.

Identification, by RT-PCR, of eight novel I₂-conotoxins from the worm-hunting cone snails Conus brunneus, Conus nux, and Conus princeps from the eastern Pacific (Mexico)

Marine snails of the genus Conus (∼500 species) are tropical predators that produce venoms for capturing prey, defense and competitive interactions. These venoms contain 50-200 different peptides ("conotoxins") that generally comprise 7-40 amino acid residues (including 0-5 disulfide bridges), and that frequently contain diverse posttranslational modifications, some of which have been demonstrated to be important for folding, stability, and biological activity. Most conotoxins affect voltage- and ligand-gated ion channels, G protein-coupled receptors, and neurotransmitter transporters, generally with high affinity and specificity. Due to these features, several conotoxins are used as molecular tools, diagnostic agents, medicines, and models for drug design. Based on the signal sequence of their precursors, conotoxins have been classified into genetic superfamilies, whereas their molecular targets allow them to be classified into pharmacological families. The objective of this work was to identify and analyze partial cDNAs encoding precursors of conotoxins belonging to I superfamily from three vermivorous species of the Mexican Pacific coast: C. brunneus, C. nux and C. princeps. The precursors identified contain diverse numbers of amino acid residues (C. brunneus, 65 or 71; C. nux, 70; C. princeps, 72 or 73), and all include a highly conserved signal peptide, a C-terminal propeptide, and a mature toxin. All the latter have one of the typical Cys frameworks of the I-conotoxins (C-C-CC-CC-C-C). The prepropeptides belong to the I2-superfamily, and encode eight different hydrophilic and acidic mature toxins, rather similar among them, and some of which have similarity with I2-conotoxins targeting voltage- and voltage-and-calcium-gated potassium channels.

Characterization of an enhanced antigenic change in the pandemic 2009 H1N1 influenza virus haemagglutinin

Murine hybridomas producing neutralizing mAbs specific to the pandemic influenza virus A/California/07/2009 haemagglutinin (HA) were isolated. These antibodies recognized at least two different but overlapping new epitopes that were conserved in the HA of most Spanish pandemic isolates. However, one of these isolates (A/Extremadura/RR6530/2010) lacked reactivity with the mAbs and carried two unique mutations in the HA head (S88Y and K136N) that were required simultaneously to eliminate reactivity with the murine antibodies. This unusual requirement directly illustrates the phenomenon of enhanced antigenic change proposed previously for the accumulation of simultaneous amino acid substitutions at antigenic sites of the influenza A virus HA during virus evolution (Shih et al., Proc Natl Acad Sci USA, 104 , 6283-6288, 2007). The changes found in the A/Extremadura/RR6530/2010 HA were not found in escape mutants selected in vitro with one of the mAbs, which contained instead nearby single amino acid changes in the HA head. Thus, either single or double point mutations may similarly alter epitopes of the new antigenic site identified in this work in the 2009 H1N1 pandemic virus HA. Moreover, this site is relevant for the human antibody response, as shown by competition of mAbs and human post-infection sera for virus binding. The results are discussed in the context of the HA antigenic structure and challenges posed for identification of sequence changes with possible antigenic impact during virus surveillance.

Severe acute respiratory syndrome coronavirus accessory proteins 6 and 9b interact in vivo

The 3'proximal one-third of the severe acute respiratory syndrome coronavirus (SARS-CoV) genome encodes the structural proteins and eight accessory proteins, including 3a, 3b, 6, 7a, 7b, 8a, 8b and 9b, varying in length from 39 to 274aa which do not share significant homology with viral proteins of known coronaviruses. The SARS-CoV protein 6 is 63 amino acids in length and has been previously involved in virus pathogenicity and replication. To further analyze this functions, the interaction of SARS-CoV protein 6 with other viral and/or cellular factors has been analyzed during SARS-CoV infective cycle. Protein 6 immunoprecipitation from extracts of SARS-CoV infected cells and mass spectrometry analysis revealed an interaction of viral proteins 6 and 9b in biologically relevant conditions. This interaction has been reinforced by co-localization of both proteins in the cytoplasm of SARS-CoV infected cells.

Role of emerging respiratory viruses in children with severe acute wheezing

BACKGROUND

Acute wheezing episodes are frequently associated with respiratory viral infections in children. However, the role of the recently described respiratory viruses is not yet fully understood.

OBJECTIVE

The main objective of this study was to estimate the frequency of human metapneumovirus (HMPV), human bocavirus (HBoV), and 14 other respiratory viruses in hospitalized children with acute wheezing.

METHODS

A prospective study was conducted on children <14 years old, admitted with an acute expiratory wheezing episode from September 2005 to June 2008. Viruses were detected in nasopharyngeal aspirates by polymerase chain reaction. Clinical data were prospectively recorded.

RESULTS

A viral pathogen was identified in 444 (71%) out of 626 hospitalized acute wheezing episodes. Respiratory syncytial virus (RSV) was the most frequently detected (27%), followed by rhinovirus (24%), adenovirus (17.8%), HBoV (16%), and HMPV (4.7%). The rate of viral detection was significantly higher in infants (77.3%), than in older children (59.8%) (P < 0.001). RSV and HBoV were more prevalent in infants (P < 0.001) than in older children.

CONCLUSION

The most prevalent viruses found in severe acute wheezing episodes were RSV and rhinovirus not only in childhood, but also in infancy. However, other emerging viruses such as HBoV and metapneumovirus also play an important role in wheezing episodes.

[Application of molecular methods in the diagnosis and epidemiological study of viral respiratory infections]

Hasta la fecha se han identificado más de 200 virus pertenecientes a 6 familias taxonómicas diferentes asociados con la infección del tracto respiratorio humano. La utilización generalizada de métodos moleculares en los laboratorios de microbiología clínica no sólo ha aportado grandes ventajas al diagnóstico de estas infecciones, sino también está permitiendo profundizar en el conocimiento de la enfermedad y el comportamiento epidemiológico de los virus causantes. Esta tecnología incrementa de manera notable el rendimiento de detección de virus en las muestras respiratorias, debido a su elevada sensibilidad en comparación con las técnicas clásicas y a la posibilidad de identificar virus no cultivables o de crecimiento fastidioso en las líneas celulares habituales, lo que permite realizar el diagnóstico etiológico con mayor rapidez. Sin embargo, también comporta algunos inconvenientes, como son detectar virus que se encuentran colonizando la mucosa respiratoria de personas asintomáticas, o en secreciones de pacientes que ya se han recuperado de una infección pasada, a consecuencia de excreción prolongada de éstos. La secuenciación de los productos obtenidos en la reacción de amplificación genómica permite caracterizar de forma adicional los virus detectados mediante su genotipado, realizar estudios de epidemiología molecular e identificar resistencias a determinados antivirales, por citar sólo algunos ejemplos.

[Migraine with aura and patent foramen ovale. A different clinical entity]

INTRODUCTION

This work has aimed to evaluate the prevalence of patent foramen ovale in subjects with migraine with aura by transcranial contrast doppler and to describe the clinical and risk profile of these patients.

METHOD

We performed a transcranial contrast doppler in 94 consecutive out-patients with migraine with aura (MWA) in a neurology outpatient clinic. They were divided into two groups according to the presence of patent foramen ovale: MWA_RLsh (with right-to-left shunt) and MWA_RLNsh (without right-to-left shunt). Differences between the groups were analyzed according to endpoints of age, gender, clinical severity, aura type and attacks frequency, comorbility, cardiovascular risk factors (CVRFs), neuroimaging findings, severity of shunt and treatment.

RESULTS

n=94; MWA_RLsh: 47 (54%). MWA_RLNsh: 40 (46%). Age: 33.13; standard desviation (SD): 10.8 vs 33.496; SD: 11.2; p=0.728. Female: 66 vs 72.5%; p=0.511. Visual aura: 73.9% vs 78.9%; p=0.921. There were no significant differences in regards to the risk factors studied or to the comorbid diseases that are associated to migraine. The patients with patent foramen ovale have an odds ratio (OR) of ischemic stroke: 1.189 (95% confidence interval [CI]: 0.226 to 6.248; p=0.840), OR for subclinical brain lesions in cranial magnetic resonance imaging (MRI): 0.589 (95% CI: 0.193 to 1.799; p=0.35) and OR for combined previous ischemic stroke and subclinical brain lesions: 0.745 (95% CI: 0.261 to 2.129; p=0.58). Migraine attack frequency >1 per month: 27.9 vs 36.4; p=0.464. Need for prophylaxis therapy: 44.7 vs 57.7%; p=0.284.

CONCLUSIONS

Both groups are similar regarding their clinical profile. We did not find a greater prevalence of stroke or silent brain lesions in the group with positive shunt..

[Stroke in the very old. Care in neurology units versus others general medical ward]

INTRODUCTION

The aim of this study is to compare the diagnosis, management, clinical course and outcome of the very major patients with acute stroke in our sanitary area.

METHOD

Retrospective collection of data from a hospital-based registry, between January 2002 and March 2004, 130 stroke patients aged 84 and older admitted consecutively. We compared the patients admitted to the neurology unit (NU) to those admitted to other services (GWs). Demographic analysis, risk factors, morbidity to hospital admission (dementia, cancer, previous stroke and laboratory variables), neurological deficit measured for Canadian Neurological Scale (CNS) score, diagnostic studies, length of stay, outcomes variables (in-hospital mortality, complications developed during hospitalization and Rankin scale at hospital discharge) and need for institutionalization were analyzed.

RESULTS

from a total of 130 patients, 44 (34,1 %) admitted to NU and 85 (65,9 %) to GWs. No difference was seen in demographic analysis, risk factors, morbidity to hospital admission, neurological deficit and outcomes variables. Length of stay was 8,4 days; 5,5 in the NU and 12,87 days among patients in the GWs (p=0,0001). There are significant differences in diagnostic studies in favor to NU (p < 0,05). Among the patients admitted into GWs the percentage of institutionalization to the discharge was of 28,8 % opposite to 5,6 % in the NU (p=0,006).

CONCLUSIONS

There are not evidences of age discrimination for access to neurological units for demographic, risk factors, morbidity or neurological deficit. The diagnostic process is more rigorous and less costly in the NU than in the GWs.

Lack of transmission of H5N1 avian-human reassortant influenza viruses in a ferret model

Avian influenza A H5N1 viruses continue to spread globally among birds, resulting in occasional transmission of virus from infected poultry to humans. Probable human-to-human transmission has been documented rarely, but H5N1 viruses have not yet acquired the ability to transmit efficiently among humans, an essential property of a pandemic virus. The pandemics of 1957 and 1968 were caused by avian-human reassortant influenza viruses that had acquired human virus-like receptor binding properties. However, the relative contribution of human internal protein genes or other molecular changes to the efficient transmission of influenza viruses among humans remains poorly understood. Here, we report on a comparative ferret model that parallels the efficient transmission of H3N2 human viruses and the poor transmission of H5N1 avian viruses in humans. In this model, an H3N2 reassortant virus with avian virus internal protein genes exhibited efficient replication but inefficient transmission, whereas H5N1 reassortant viruses with four or six human virus internal protein genes exhibited reduced replication and no transmission. These findings indicate that the human virus H3N2 surface protein genes alone did not confer efficient transmissibility and that acquisition of human virus internal protein genes alone was insufficient for this 1997 H5N1 virus to develop pandemic capabilities, even after serial passages in a mammalian host. These results highlight the complexity of the genetic basis of influenza virus transmissibility and suggest that H5N1 viruses may require further adaptation to acquire this essential pandemic trait.

Threonine 157 of influenza virus PA polymerase subunit modulates RNA replication in infectious viruses

Previous results have shown a correlation between the decrease in protease activity of several influenza A virus PA protein mutants and the capacity to replicate of the corresponding mutant ribonucleoproteins (RNPs) reconstituted in vivo. In this work we studied the phenotype of mutant viruses containing these mutations. Viruses with a T162A mutation, which showed a very moderate decrease both in protease and replication activities of reconstituted RNPs, showed a wild-type phenotype. Viruses with a T157A mutation, which presented a severe decrease in protease activity and replication of RNPs, showed a complex phenotype: (i) transport to the nucleus of PAT157A protein was delayed, (ii) virus multiplication was reduced at both low and high multiplicities, (iii) transcriptive synthesis was unaltered while replicative synthesis, especially cRNA, was diminished, and (iv) viral pathogenesis in mice was reduced, as measured by loss of body weight and virus titers in lungs. Finally, recombinant viruses with a T157E mutation in PA protein, which resulted in a drastic reduction of protease and replication activities of RNPs, were not viable. These results indicate that residue T157 in PA protein is important for the capacity of viral polymerase to synthesize cRNA.

Electrophysiological and hemolytic activity elicited by the venom of the jellyfish Cassiopea xamachana

In this study, we determined hemolysis activity in human and sheep erythrocytes, and characterized the electrical responses in Xenopus oocyte membrane elicited by the venom of the jellyfish Cassiopea xamachana (Cx). The Cx venom produced hemolysis in both species, being more potent on human red cells. The electrophysiological study showed that the Cx venom elicited three different responses in the oocytes. One current was generated in all the oocytes tested and corresponded with a slow inward current (I(Cx)) associated with an increase in membrane conductance. I(Cx) was concentration-dependent and had a reversal potential of -10.3+/-0.4 mV. Ionic substitution studies indicated that the conductive pathway was mainly permeable to cations and non-selective. The oocyte membrane resistance was completely recovered after washout of the venom, this suggested that the effect was due to generation of a specific membrane conductance as opposed to a possible non-specific membrane breakdown. A comparative study with three distinct native cationic channels present in the oocyte membrane [i.e. (1) hemi-gap-junction channels, (2) mechanosensitive channels, and (3) the ouabain-sensitive channel activated by palytoxin], showed that I(Cx) might correspond to opening of mechanosensitive channels or to activation of an unknown cationic channel located in the oocyte membrane. The bioactive fraction eliciting I(Cx) were peptides and was separated from two other peptidic hemolytic fractions by chromatography.