Antibody status to influenza A/Singapore/1/57(H2N2) in Finland during a period of outbreaks caused by H3N2 and H1N1 subtype viruses.

The incidence of haemagglutination inhibition (HI) antibody (titre greater than or equal to 12) to influenza A/Singapore/1/57(H2N2) in sera collected from a Finnish population in the summer of 1981 was 58%. Subjects born after 1968 were essentially seronegative, and a comparable low HI antibody status was also recorded among the elderly, the lowest being in people born during the period 1901-10. A small increase in antibody titre to the H2N2 virus was observed in the different age groups after infections with the H3N2, but not the H1N1, subtype influenza A viruses. The heterotypic response, which could be due to HI or NA antibodies, was restricted almost exclusively to subjects already exhibiting this antibody in acute phase sera. Moreover, the anamnestic boosting was not as strong as that described in earlier studies from samples collected at the beginning of the present era of H3N2 viruses. At population level, the HI antibody status to H2N2 was about the same at the beginning and end of the follow-up period which covered eight epidemic seasons. The results are discussed with respect to the doctrine of ''original antigenic sin'' and to the threat of re-emergence of the H2N2 viruses.     

Emergence and possible transmission of amantadine-resistant viruses during nursing home outbreaks of influenza A (H3N2)

Outbreaks of influenza A (H3N2, A/Shanghai/11/87-like) occurred in two partially (60% and 79%) vaccinated nursing home populations in January 1988. A retrospective cohort study using chart review was designed to assess the effectiveness of influenza vaccination and amantadine prophylaxis (100 mg per day) in controlling the outbreaks and to determine the amantadine susceptibility of influenza viruses isolated from case-patients. The point estimate of vaccine efficacy in preventing influenza-like illness was -33% (95% confidence interval -115% to 18%). However, 9% of vaccinated case-patients died within 14 days after onset of influenza-like illness compared with 26% of unvaccinated case-patients (relative risk = 0.4, 95% confidence interval 0.1-1.0). There was no significant difference in illness severity among case-patients who became ill before amantadine prophylaxis was started (n = 84) compared with those who became ill while taking amantadine (n = 34). Four virus isolates obtained before amantadine prophylaxis was started demonstrated 52-68% inhibition by 1 microgram/ml of amantadine; by comparison, six isolates (resistant viruses) obtained from residents who became ill while taking amantadine demonstrated 1-18% inhibition. The resistant viruses had four different RNA sequences in the gene coding for the M2 protein transmembrane region. Three resistant viruses with identical RNA sequences were isolated from residents living in contiguous rooms who had onset of signs and symptoms during a 6-day interval. Further studies are needed to determine how frequently and under what circumstances resistant viruses occur when antiviral agents are used to control institutional influenza A outbreaks. Strategies for antiviral agent administration that limit the emergence and transmission of resistant virus strains may be needed.     

Antibody responses to influenza A(H1N1)pdm infection

We investigated humoral immune response to influenza A(H1N1)pdm infection and found 32 (22%) of the infected individuals identified by PCR failed to produce a ≥ 4-fold hemagglutinin inhibition assay (HAI) response; a subset of 18 (56%) produced an alternate antibody response (against full-length HA, HA stalk, or neuraminidase). These individuals had lower pre-existing HAI antibody titers and showed a pattern of milder illness. An additional subset of 14 (44%) did not produce an alternate antibody response, had higher pre-existing antibody titers against full-length & stalk HA, and were less sick. These findings demonstrate that some individuals mount an alternate antibody response to influenza infection. In order to design more broadly protective influenza vaccines it may be useful to target these alternate sites. These findings support that there are influenza cases currently being missed by solely implementing HAI assays, resulting in an underestimation of the global burden of influenza infection.     

Predicting antigenic variants of influenza A/H3N2 viruses

Current inactivated influenza vaccines provide protection when vaccine antigens and circulating viruses share a high degree of similarity in hemagglutinin protein. Five antigenic sites in the hemagglutinin protein have been proposed, and 131 amino acid positions have been identified in the five antigenic sites. In addition, 20, 18, and 32 amino acid positions in the hemagglutinin protein have been identified as mouse monoclonal antibody-binding sites, positively selected codons, and substantially diverse codons, respectively. We investigated these amino acid positions for predicting antigenic variants of influenza A/H3N2 viruses in ferrets. Results indicate that the model based on the number of amino acid changes in the five antigenic sites is best for predicting antigenic variants (agreement = 83%). The methods described in this study could be applied to predict vaccine-induced cross-reactive antibody responses in humans, which may further improve the selection of vaccine strains.     

HA1 (Hemagglutinin) quantitation for influenza A H1N1 and H3N2 high yield reassortant vaccine candidate seed viruses by RP-UPLC

The only effective measure to decrease morbidity and mortality caused by the influenza virus in the human population is worldwide vaccination. Vaccination produces neutralizing antibodies that target the HA1 subunit of the HA (hemagglutinin) protein and are strain specific. The effectiveness of new influenza vaccines are linked to two factors, the correct prediction of the circulating strains in the population in a particular season and the concentration of the HA1 protein in the vaccine formulation. With the advent of the licensing of quadrivalent vaccines, pharmaceutical manufacturers are under considerable pressure due to time constraints and dedicated resources to deliver 194–198 million doses (2020–2021 U.S. market) of vaccine. Considering the valuable resources needed to produce the influenza vaccine in a timely manner, the efficient quantitation of the HA1 protein (the main component in the influenza vaccine) is required. Currently the only method approved by regulatory agencies for quantitation of the HA antigen in vaccines is the single radial immunodiffusion assay (SRID), an antibody dependent assay that is not time efficient. Time efficient methods that are antibody independent e.g. reverse phase-high performance liquid chromatography (RP-HPLC) or size exclusion-HPLC (SE-HPLC) are available. An improved method implementing reverse phase-ultra performance liquid chromatography (RP-UPLC) has been developed to quantitate the HA1 protein antigen present in the high yield reassortant vaccine seed viruses from influenza A H1N1 and H3N2 subtypes harvested from inoculated embryonated chicken eggs. This method differentiates between high yield and lower yielding reassortants in order to select the best vaccine candidate seed virus with the highest growth ‘in ovo’. This direct capability to monitor the HA1 concentration of potential reassortant seed viruses and to choose the best yielding HA influenza reassortant when faced with multiple viral seed candidates provides a major advantage on the industrial scale to the influenza vaccine process.     

Environmental contamination during influenza A virus (H5N1) outbreaks, Cambodia, 2006

To determine potential risk for bird-to-human transmission during influenza A virus (H5N1) outbreaks among backyard poultry in rural Cambodia, we collected environmental specimens. Viral RNA was detected in 27 (35%) of 77 specimens of mud, pond water, water plants, and soil swabs. Our results underscore the need for regular disinfection of poultry areas.     

Laboratory-based surveillance of influenza A(H1N1) and A(H3N2) viruses in 1980-81: antigenic and genomic analyses

During 1981, the A/Brazil/11/78-like strains of influenza virus that had been prevalent from 1978 to 1980 were displaced by a new set of heterogeneous, but closely related, variants (reference strain, A/England/333/80). Genomic analysis revealed that these new variants were almost exclusively nonrecombinant H1N1 viruses, i.e., they contained no genes of H3N2 origin. However, a few recombinant viruses containing the new variant HA and genes of H3N2 origin were identified. Antigenic analysis of H3N2 viruses indicated that they were also heterogeneous. The majority of these virus isolates were antigenically intermediate between A/Texas/1/77 and A/Bangkok/1/79, but additional variants were detected. Genomic analysis revealed that the H3N2 viruses isolated in the winter of 1980-81 were quite similar to H3N2 viruses isolated from 1977-79 in their T₁ oligonucleotide maps. No H1N1 genes were detected in H3N2 virus isolates. Comparison of pairs of oligonucleotide maps of total virus RNA indicated that a similar rate of genetic change had occurred for nonrecombinant H1N1 viruses, for recombinant H1N1 viruses, and for H3N2 viruses and that, in general, pairs of viruses exhibited increasing numbers of changes in their oligonucleotide maps as the time interval between isolation of the viruses increased.     

Avian-origin H3N2 canine influenza A viruses in Southern China

This study reports four sporadic cases of H3N2 canine influenza in Southern China, which were identified from sick dogs from May 2006 to October 2007. The evolutionary analysis showed that all eight segments of these four viruses are avian-origin and phylogenetically close to the H3N2 canine influenza viruses reported earlier in South Korea. Systematic surveillance is required to monitor the disease and evolutionary behavior of this virus in canine populations in China.     

Matrix protein 2 vaccination and protection against influenza viruses, including subtype H5N1

Changes in influenza viruses require regular reformulation of strain-specific influenza vaccines. Vaccines based on conserved antigens provide broader protection. Influenza matrix protein 2 (M2) is highly conserved across influenza A subtypes. To evaluate its efficacy as a vaccine candidate, we vaccinated mice with M2 peptide of a widely shared consensus sequence. This vaccination induced antibodies that cross-reacted with divergent M2 peptide from an H5N1 subtype. A DNA vaccine expressing full-length consensus-sequence M2 (M2-DNA) induced M2-specific antibody responses and protected against challenge with lethal influenza. Mice primed with M2-DNA and then boosted with recombinant adenovirus expressing M2 (M2-Ad) had enhanced antibody responses that crossreacted with human and avian M2 sequences and produced T-cell responses. This M2 prime-boost vaccination conferred broad protection against challenge with lethal influenza A, including an H5N1 strain. Vaccination with M2, with key sequences represented, may provide broad protection against influenza A.     

广州市2019年H3N2流感病毒分子流行特征分析

目的 对广州市2019年不同来源的H3N2流感病毒进行基因测序,分析H3N2流感病毒的进化变异特点。方法 对广州市2019年门诊监测、暴发疫情、住院重症病例等不同标本来源的H3N2流感病毒进行分离并对其血凝素（HA）和神经氨酸酶（NA）基因进行测序,运用DNA Star 7.1、Mega 6.0软件分析病毒的变异和进化特点。结果 2019年广州市H3N2流感表现为流行期Ⅰ（2019年1-8月）和流行期Ⅱ（2019年11-12月）2个流行高峰。男性和女性的H3N2流感病毒阳性率分别为13.46%（703/5 221）和11.50%（510/4 435）,差异有统计学意义（χ²=8.43,P=0.00）。10~20岁年龄组H3N2流感病毒阳性率最高（25.18%,665/2 641）,各年龄组阳性率差异有统计学意义。测序发现,不同标本来源的毒株高度同源,亲缘关系相近,属于3C.2a.1分支。根据流行时间和进化特点,进一步划分为Group 1~3共3个小进化分支,Group 1分支流行于流行期Ⅰ、Group 3分支流行于流行期Ⅱ,Group 2分支为2个流行期过度的进化分支,流行期Ⅱ的病毒由流行期Ⅰ的病毒进化而来,且不同分支存在基因重组的现象。在疫苗选择压力下,Group 1~3分支逐渐出现HA抗原位点突变,导致新的抗原漂移。HA抗原位点变异主要发生A和B区,Group 1分支和Group 3分支受体结合位点变异发生在前壁和后壁,Group 2~3分支在HA抗原位点A区缺失2个糖基化位点。结论 2019年广州市H3N2流感病毒的遗传变异包括位点突变和基因重组。在疫苗免疫压力下H3N2流感病毒发生快速的进化变异,抗原位点变异逐渐累积,进而出现新的抗原漂移。应对H3N2流感病毒分子流行特点进行持续监测。     

Antigenic and genomic relation between human influenza A (H3N2) viruses circulating in Argentina during 1998 and the H3N2 vaccine component.

OBJECTIVE: Due to the lack of correlation from 1994 to 1997 between the A H3N2 component of the influenza vaccine recommended for this period and the circulating viruses in Argentina, we decided to study the antigenic and genomic relationships of the 1998 A H3N2 Argentine circulating strains with the corresponding vaccine component for that year as recommended by the World Health Organization (WHO). METHODS: We selected 18 influenza A H3N2 strains isolated in Argentina during 1998 to carry out an antigenic and genomic study of their hemagglutinin (HA) and neuraminidase (NA) proteins. For the genomic study we added 3 isolates from Uruguay. We compared the Argentine and Uruguayan strains with available reference strains. RESULTS: We found that all 18 strains from Argentina were similar to the A/Sydney/5/97 (H3N2) strain, as opposed to the A/Wuhan/359/95 (H3N2) strain, which was the vaccine component. This result was confirmed by the genomic study. CONCLUSIONS: The approach that we applied in Argentina has improved the quality and quantity of information about influenza in the country. This type of work should be encouraged in other countries in order to help choose the most appropriate vaccine components each year and provide individuals with the best possible protection against influenza.     

3起学校甲型H1N1流感暴发疫情流行病学分析

目的分析山东省2009年9月1日-9月9日3起学校甲型H1N1流感暴发疫情的流行病学特征,为防控工作提供科学依据。方法采用流行病学调查方法调查确诊病例的流行病学史、临床表现等,调查资料实时录入甲型H1N1流感信息管理系统;应用Excel建立数据库,采用SAS软件进行统计分析。结果3起暴发疫情累计确诊甲型H1N1流感病例85例,3起暴发疫情的罹患率分别为A大学0.99%、B中学6.29%、C中学0.62%,3起疫情罹患率间差异有统计学意义(χ2=95.54,P0.001)。C中学发现病例即采取全校停课措施,严格分类管理病例,使C中学暴发流行周期最短。结论3起甲型H1N1流感暴发疫情均发生在学校,学校是控制甲型H1N1流感疫情的关键,应高度关注学校甲型H1N1流感防控措施。     

Avian influenza A virus (H5N1) outbreaks, Kuwait, 2007

Phylogenetic analysis of influenza A viruses (H5N1) isolated from Kuwait in 2007 show that (H5N1) sublineage clade 2.2 viruses continue to spread across Europe, Africa, and the Middle East. Virus isolates were most closely related to isolates from central Asia and were likely vectored by migratory birds.     

甲型H1N1流感病毒致血栓性血小板减少性紫癜1例

正血栓性血小板减少性紫癜(thrombotic thrombocytopenic purpura,TTP)属于危重症血液病,临床罕见,若不能及时诊治会造成极高的病死率。临床若具有典型五联征:发热、溶血性贫血、紫癜或血小板减少症相关的出血、神经系统症状、伴有血尿和/或蛋白尿或尿素氮升高的肾病即可诊断,行血浆     

The development of vaccine viruses against pandemic A(H1N1) influenza

Wild type human influenza viruses do not usually grow well in embryonated hens’ eggs, the substrate of choice for the production of inactivated influenza vaccine, and vaccine viruses need to be developed specifically for this purpose. In the event of a pandemic of influenza, vaccine viruses need to be created with utmost speed. At the onset of the current A(H1N1) pandemic in April 2009, a network of laboratories began a race against time to develop suitable candidate vaccine viruses. Two approaches were followed, the classical reassortment approach and the more recent reverse genetics approach. This report describes the development and the characteristics of current pandemic H1N1 candidate vaccine viruses.     

Type A influenza (H2N2) viruses isolated in Leningrad in 1980.

In April-May 1980, two independent outbreaks of influenza-like illness occurred in Leningrad among children''s-home children aged from 3 months to 2 years (of 68 children under observation, 50 became ill) and among boarding-school pupils aged 15-17 years (of 50 pupils under observation, 13 became ill). A total of five influenza A virus strains were derived from one clinically healthy and three affected children of the children''s home. Similar viruses were obtained from one affected boarding-school pupil and from an infected woman aged 24 years (a sporadic case within a household). On the basis of laboratory findings, all these seven strains were identified as influenza A H2N2 subtype strains. Six of the affected children showed significant seroconversion only to H2 haemagglutinin from February to May 1980. Type A influenza H2N2 virus was isolated from three persons, including the sporadic case, who also showed significant seroconversion to H2 haemagglutinin. H2N2 influenza A virus was isolated on two occasions, at a 7-day interval, from the girl N. Ju. Laboratory findings obtained from the study of the viruses isolated using up-to-date immunological and molecular-biochemical techniques enable us to conclude the following. The A/Leningrad/80 isolates belong to H2N2 sero-subtype. The viruses isolated are similar but not identical to the A/Singapore/I/57 reference strain in details of polypeptide and gene composition.     

一起院内感染甲型H3N2流感暴发疫情调查

目的 明确某院内感染流感疫情流行特征及可能的暴发原因,为控制疫情提供科学依据。 方法 制订病例定义进行病例搜索,采取现场流行病学调查方法开展个案调查和现场卫生学调查;采用描述性流行病学和病例对照研究方法,结合病例临床特征和实验室病毒核酸检测结果,分析疫情的流行特征和可能的暴发原因。 结果 此次院内感染疫情共报告实验室确诊病例9人,临床诊断病例8人。发病高峰为5月31日。推算潜伏期最短为1 d,最长4 d,平均为2.6 d;一楼住院病人和护士的发病率差异无统计学意义(P=0.695);护士是否在1楼上班发病率差异有统计学意义(OR=6.60, 95%CI:1.48~29.36);采集10例患者标本进行RT-PCR检测,9例均为H3N2流感病毒核酸阳性;所有护士无流感疫苗免疫接种史;通过对病例的隔离治疗,所有病例病情稳定或痊愈,且在最长潜伏期内无新发病例出现。 结论 本次疫情为一起医院内由新入院患者作为传染源,在护士和其他住院患者间经飞沫传播的甲型H3N2流感暴发疫情;及时进行隔离治疗是最有效的防控措施之一;护士可能是导致此次流感疫情暴发的主要传播者之一;医疗卫生机构工作人员应加强流感疫苗的接种, 以增强免疫力或减轻流感症状。