Clinical and virological course of infection with haemagglutinin D222G mutant strain of 2009 pandemic influenza A (H1N1) virus

BackgroundAspartic acid to glycine substitution (D222G) of haemagglutinin subunit (HA1) was associated with adverse outcomes in 2009 pandemic influenza A (H1N1) infections.ObjectivesTo characterize the virological profile and antiviral response of patients infected with the HA1 D222G mutant.Study designSixty-three adults admitted for pandemic influenza in Hong Kong were tested for D222G mutation by direct sequencing. Nasopharyngeal viral concentration on presentation was measured by real-time PCR to evaluate shedding from the upper respiratory tract. Serial upper and lower respiratory tract specimens were monitored to determine preferential tropism and document virological response to treatment.ResultsThe frequency of D222G infection was 17.4% among cases with severe pneumonia, and 26.7% among cases requiring intensive care. Altogether, four sporadic D222G cases spread across the first and second waves in Hong Kong were detected. A significant association between D222G infection with severe pneumonia (100% vs. 32.2%, P = 0.015) and intensive care admission (100% vs. 18.6%, P = 0.002) was observed. D222G was associated with lower concentrations of virus in the upper respiratory tract compared to wildtype, but persisted in the lower respiratory tract at high concentrations, despite clearance from the upper respiratory tract following antiviral treatment.ConclusionsThese observations suggest that D222G can arise de novo, sheds less virus from the upper respiratory tract and may be less transmissible, but more pneumotropic and more resistant to antiviral treatment. D222G is associated with a higher chance of developing critical disease. Lower respiratory tract specimen is needed for a reliable detection of this mutant.     

Detection of hemagglutinin variants of the pandemic influenza A (H1N1) 2009 virus by pyrosequencing

For influenza viruses, pyrosequencing has been successfully applied to the high-throughput detection of resistance markers in genes encoding the drug-targeted M2 protein and neuraminidase. In this study, we expanded the utility of this assay to the detection of multiple receptor binding variants of the hemagglutinin protein of influenza viruses directly in clinical specimens. Specifically, a customized pyrosequencing protocol that permits detection of virus variants with the D, G, N, or E amino acid at position 222 in the hemagglutinin of the 2009 pandemic influenza A (H1N1) virus was developed. This customized pyrosequencing protocol was applied to the analysis of 241 clinical specimens. The use of the optimized nucleotide dispensation order allowed detection of mixtures of variants in 10 samples (4.1%) which the standard cyclic nucleotide dispensation protocol failed to detect. The optimized pyrosequencing protocol is expected to provide a more accurate tool in the analysis of virus variant composition.     

Pandemic influenza A(H1N1) 2009 virus in pregnancy

Two hundred fourteen abstracts and 87 full texts regarding pregnant women infected with pandemic influenza A(H1N1) 2009 virus were systematically reviewed by using a PubMed search and assessing pandemic, clinical, laboratory test, vaccine, and control experiences. Both policy and health education were excluded. This review counted the total number of pregnant cases from different countries and analyzed their epidemic features, including trimester distribution, morbidity, hospitalization, intensive care unit admissions, maternal mortality, underlying diseases, complications, high‐risk factors for death, pregnancy outcome, and clinical symptoms compared with the previous pandemic seasonal influenza A/H1N1 as compared with the general population. Early identification and treatment were the most important factors in different countries and areas examined. The vaccine and antiviral drugs that have been the most efficient means to control the novel virus appear to be safe but require more extensive study. In the future, the focus should be placed on understanding vertical transmission and the severe mechanisms. Copyright © 2012 John Wiley & Sons, Ltd.     

Emergent 2009 influenza A(H1N1) viruses containing HA D222N mutation associated with severe clinical outcomes in the Americas

Background

During the 2010-2011 influenza season, a small sub-group of 2009 influenza A(H1N1) viruses (hereafter referred to as 2009 A(H1N1)) emerged that was associated with more severe clinical outcomes in Ecuador and North America. Genetically, the haemagglutinin (HA) of this sub-clade was distinct from HAs found in viruses associated with severe outbreaks in 2010 from the United Kingdom and from other global specimens isolated earlier in the season.

Objective

We report the emergence of a novel 2009 A(H1N1) variant possessing a re-emergent HA D222N mutation obtained from patients with severe respiratory illnesses and phylogenetically characterise these D222N mutants with other severe disease-causing variants clustering within a common emerging sub-clade.

Case reports

In early 2011, three cases of 2009 A(H1N1) infection, two from Quito, Ecuador, and one from Washington, DC, USA, were complicated by severe pneumonia requiring mechanical ventilation, resulting in one fatality. These cases were selected due to the reported nature of the acute respiratory distress (ARD) that were captured in Department of Defence (DoD)-sponsored global influenza surveillance nets.

Results

Genetically, the 2009 A(H1N1) strains isolated from two of the three severe cases carried a prominent amino acid change at position 222 (D222N) within the primary HA receptor binding site. Furthermore, these cases represent an emerging sub-clade of viruses defined by amino acid changes within HA: N31D, S162N, A186T and V272I. Phylogenetically, these viruses share a high degree of homology with strains associated with recent fatal cases in Chihuahua, Mexico.

Discussion

Previously, enhanced virulence associated with the change, D222G, has been clinically linked to severe morbidity and mortality. Initial observations of the prevalence of a novel sub-clade of strains in the Americas suggest that viruses with a re-emergent D222N mutation may too correlate with severe clinical manifestations. These findings warrant heightened vigilance for emerging sub-clades of 2009 A(H1N1) and presumptive clinical implications.     

Surveillance of autopsy cases for D222G substitutions in haemagglutinin of the pandemic (H1N1) 2009 virus in Alberta,Canada

Pandemic (H1N1) 2009 virus-positive specimens were collected from autopsy patients and matched to pandemic (H1N1) 2009 virus-positive nasopharyngeal specimens from community control patients and pandemic (H1N1) 2009 virus-positive specimens from intensive-care unit (ICU) patients. Specimens were analysed for polymorphisms at amino acid 222 of the haemagglutinin (HA) glycoprotein. Whereas some specimens from autopsy patients were positive for D222N, none was positive for D222G. All control patient specimens were wild-type D222. D222G polymorphisms were also identified in a subset of ICU patients with admixtures of D222G and D222 and of D222N, D222G and D222 present. The relevance of D222N and D222G to influenza pathogenesis and transmissibility currently remains unclear.     

动物源性和人源性甲型流感病毒(H1N1)血凝素(HA)的特征分析

目的 研究动物源性和人源性甲型H1N1流感病毒(influenza A virus)血凝素(hemagglutinin,HA)的特征,以探讨动物源性和人源性甲型H1N1流感病毒血凝素之间的关系.方法 从美国生物信息中心(NCBI)下载禽(鸟)源、猪源、人源的甲型H1N1流感病毒血凝素氨基酸序列,使用Clustal W2.0生物学软件比较上述血凝素氨基酸序列,并建立甲型H1N1流感病毒血凝素氨基酸序列的进化树.结果 2009年分离的人源性甲型流感病毒血凝素氨基酸序列同源性非常高,达到了99%～100%,而2009年分离的人源性甲型流感病毒血凝素氨基酸序列和禽(鸟)源,猪源的甲型流感病毒血凝素氨基酸序列之间的同源性非常低,只有77%～90%(只有猪源ABW36355和2009年分离的人源甲型流感病毒血凝素氨基酸序列同源性为90%,余同源性为77%～83%);蛋白生物进化树表明禽源(鸟)、猪源、人源的甲型流感病毒血凝素氨基酸序列明显分为3个大的分支.2009年分离的人源性甲型流感病毒血凝素氨基酸序列(ADA71154除外)与疫情前分离得到的人源的血凝素氨基酸序列同源性很低(79%～80%),并且进化树分为3个分支.结论 2009年流行的甲型H1N1流感病毒是一种新的流感病毒,病毒的血凝素氨基酸序列之间的同源性非常高,而和猪、禽(鸟)源的甲型H1N1流感病毒的血凝素氨基酸序列之间的同源性非常低,从这一层面上来讲,目前流行的甲型流感病毒的血凝素的基因并不是猪源和禽源,和疫情前人源的血凝素比对的结果也表明,2009年流行的甲型H1N1流感病毒也并不是直接源于2009年以前的人源流感H1N1病毒,而应该是另有来源.     

High-yield reassortant virus containing hemagglutinin and neuraminidase genes of pandemic influenza A/Moscowl/01/2009 (H1N1) virus

The crossing of influenza A/Moscow/01/2009 (H1N1) virus and reassortant strain X31 (H3N2) containing the genes of internal and non-structural proteins of A/Puerto Rico/8/34 (H1N1) strain gave rise to reassortant virus ReM8. The reassortant contained hemagglutinin (HA) and neuraminidase (NA) genes of pandemic 2009 influenza virus and 6 genes of high-yield A/Puerto Rico/8/34 (H1N1) strain. The reassortant ReM8 produced higher yields in the embryonated chicken eggs than the parent pandemic virus, as suggested by infectivity and HA activity titration as well as by ELISA and the measurement of HA protein content by scanning electrophoresis in polyacrylamide gel slabs. High immunogenicity of ReM8 reassortant was demonstrated by immune protection studies in mice. The reassortant virus ReM8 is suitable as a candidate strain for the production of inactivated and subunit influenza vaccines.     

Immunological study of antigenic determinants in the isolated hemagglutinin of the influenza A virus (H1N1)

A preparation of isolated subunits of influenza A (H1N1) virus hemagglutinin was examined for antigenic properties by four serological tests: radioimmunoassay, radial immunodiffusion test, complement fixation test, and hemagglutination inhibition test with hyperimmune polyclonal serum to intact virion as well as with monospecific antibodies to individual antigenic determinants obtained by adsorption technique. In isolated hemagglutinin subunits, radioimmunoassay identified three main virus-specific antigenic sites identical to antigenic determinants in the hemagglutinin of the intact virion. No neuraminidase was found in the hemagglutinin preparation but increased serological activity of host cell antigens was observed.     

新型甲型H1N1流感病毒HA基因DNA疫苗诱导小鼠产生中和抗体

目的 探讨新型甲型流感病毒(2009H1N1)血凝素(HA)DNA疫苗诱导小鼠产生中和抗体特性.方法 构建2009H1N1或1918甲型流感病毒(1918H1N1)HA蛋白表达质粒2009HA和1918HA,采用25μg或200μg剂量2009HA质粒免疫小鼠,以2009HA或1918HA蛋白为包被抗原,测定小鼠血清中2009HA抗体总量或交叉反应抗体含量,分别用2009H1N1和1918H1N1两种假病毒(pp)测定抗体中和活性.结果 25 μg或200μg的2009HA质粒加强免疫小鼠后,4～16周内两组小鼠血清中2009HA总抗体水平以及对2009H1N1pp的中和抗体滴度相似(P>0.05),都含有与1918HA蛋白交叉反应抗体,对1918H1N1pp的交叉中和抗体滴度相似(P>0.05).结论 小剂量2009HA质粒DNA疫苗能够诱导小鼠产生持久的高水平中和抗体,对于预防新现流感病毒具有潜在应用价值.     

Characterization of 2009 pandemic influenza A (H1N1) virus specimens with a positive hemagglutinin 1 signal in the Luminex xTAG respiratory viral panel assay

This retrospective review analyzed Luminex xTAG respiratory viral panel (RVP) results for 2009 pandemic influenza A (H1N1) virus specimens. Comparing median fluorescence intensity (MFI) signals for the influenza A virus and hemagglutinin 1 (H1) reactions for specimens with very low positive (MFI < 1,000) or "no-call" H1 results reliably distinguished 2009 H1N1 from seasonal virus.     

In vivo evaluation of pathogenicity and transmissibility of influenza A(H1N1)pdm09 hemagglutinin receptor binding domain 222 intrahost variants isolated from a single immunocompromised patient

The influenza A(H1N1)pdm09 virus has circulated worldwide and continued to cause complicated infections and deaths. Reports have identified an increased prevalence of the hemagglutinin receptor binding domain D222G mutation in viruses isolated from individuals who have suffered such severe infections, but this association is still unclear. Virus isolated from a nasopharyngeal wash of a severely ill immunocompromised patient at the time of diagnosis contained the D222, but isolates collected later in his course from a bronchoalveolar lavage contained primarily the G222 mutation and was mixed with a minor population of D222. These clinical isolates were compared to a G222 plaque purified virus in the ferret model. The G222 predominant clinical isolate was the most pathogenic in ferrets and developed the most diversity at the 222 amino acid position during infection, suggesting that increased diversity and not a specific polymorphism at HA 222 may be important in predicting pathogenic potential.     

Pandemic (H1N1) 2009 influenza virus seroconversion rates in HIV-infected individuals

The impact of pandemic (H1N1) 2009 influenza in HIV-infected individuals is unknown. Determining the prevalence of pandemic influenza in this at-risk group will guide vaccination programs. After the first pandemic wave, the seroprevalence rate of pandemic influenza in HIV-infected individuals in western Sydney, New South Wales, Australia, was 34.2%, similar to the rate observed in the general population. However, true seroprevalence is more accurately determined by seroconversion, defined as a 4-fold or greater rise between preexposure and postexposure antibody levels, which was 14.6% in the present study. Seroconversion rates were independent of CD4 T-lymphocyte count and HIV plasma load. Neither HIV infection, nor severe immunosuppression, was a significant risk factor for pandemic influenza during the first southern hemisphere pandemic wave.     

Rhinoviruses delayed the circulation of the pandemic influenza A (H1N1) 2009 virus in France

In contrast to the experience in other European countries, the onset of the A(H1N1)2009 influenza virus epidemic was unexpectedly slow in France during the first part of autumn 2009. Our objective was to test the hypothesis that intense circulation of rhinoviruses might have reduced the probability of infection by A(H1N1)2009 virus at the beginning of autumn 2009. Systematic analysis for the detection of A(H1N1)2009 (H1N1) and human rhinovirus (HRV) was performed by RT-PCR from week 36 to week 48 on respiratory samples sent to the diagnostic laboratory by the paediatric hospital (n = 2121). Retrospective analysis of the obtained data, using 2 × 2 contingency tables with Fisher's exact test, revealed evidence of an inverse relationship between HRV and H1N1 detection. Between weeks 36 and 48 of 2009, both HRV and H1N1 were detected but in different time frames. HRV dispersed widely during early September, peaking at the end of the month, whereas the H1N1 epidemic began during mid-October and was still active at the end of this survey. During the co-circulation period of these two respiratory viruses (weeks 43–46), HRV detection appeared to reduce the likelihood of H1N1 detection in the same sample (OR = 0.08–0.24 p <0.0001). These results support the hypothesis that HRV infections can reduce the probability of A(H1N1) infection. This viral interference between respiratory viruses could have affected the spread of the H1N1 viruses and delayed the influenza pandemic at the beginning of autumn in France.     

The validation of a real-time RT-PCR assay which detects influenza A and types simultaneously for influenza A H1N1 (2009) and oseltamivir-resistant (H275Y) influenza A H1N1 (2009)

Influenza A H1N1 (2009) was declared by the World Health Organisation (WHO) as the first influenza pandemic of the 21st century. Rapid detection of influenza A and differentiation of influenza A H1N1 (2009) and seasonal influenza A is beneficial. In addition the rapid detection of antiviral resistant strains of influenza A H1N1 (2009) would be useful for clinicians to allow for change to an effective treatment at a much earlier stage if resistance is found. It was the aim of this study to develop a real-time RT-PCR that can detect all influenza A viruses and type simultaneously for influenza A H1N1 (2009) and oseltamivir resistant (H275Y) influenza A H1N1 (2009). This multiplex assay will allow laboratories to screen respiratory samples for all types of influenza A, influenza A H1N1 (2009) virus and oseltamivir resistant (H275Y) influenza A H1N1 (2009) virus in a rapid and cost effective format, ensuring that typing methods for seasonal and avian viruses are used on a smaller subset of samples. Since most virology laboratories already offer a molecular service for influenza A this assay could easily be implemented into most areas at little cost therefore increasing local access to resistance testing.     

Molecular and genetic characteristics of hemagglutinin and neuraminidase in Iranian 2009 pandemic influenza A(H1N1) viruses

Influenza virus infections cause severe illness worldwide. Vaccination reduces the morbidity and mortality of influenza. The efficacy of vaccines varies due to antigenic differences between the circulating influenza strains and the vaccine. Neuraminidase inhibitors are effective for prophylaxis and treatment of influenza infections, and the emergence of drug resistant mutants is an important challenge. Full-length nucleotide and deduced amino acid sequences of the hemagglutinin and neuraminidase genes of three 2009 pandemic influenza A/H1N1 isolates were compared with the vaccine strain and some strains from different countries. Phylogenetic analysis for hemagglutinin and neuraminidase showed they were related to their vaccine strain, with an average of 99.56 and 99.53% sequence identity, respectively. No genetic indication of resistance to neuraminidase inhibitors was found. Although genomic analysis of hemagglutinin and neuraminidase genes of Iranian strains in comparison to the corresponding vaccine strain revealed some mutations, none of these were identified in functionally important receptor-binding sites.