RNAs of influenza A, B, and C viruses.

The nucleic acids of influenza A, B, and C viruses were compared. Susceptibility to nucleases demonstrates that influenza C virus, just as influenza A and B viruses, possesses single-stranded RNA as its genome. The base compositions of the RNAs of influenza A, B, and influenza C virus are almost identical and comparative analysis on polyacrylamide gels shows that the genome of influenza C/GL/1167/54 virus, like that of the RNAs of influenza A and B viruses, is segmented. Eight distinct RNA bands were found for influenza A/PR/8/34 virus and for influenza B/Lee/40 virus. The RNA of influenza C/GL/1167/54 virus separated into at least four segments. The total molecular weights of the RNA of influenza A/PR/8/34 and B/Lee/40 virus were calculated to be 5.29 X 10(6) and 6.43 X 10(6), respectively. A minimum value of 4.67 X 10(6) daltons was obtained for influenza C/GL/1167/54 virus RNA. The data suggest that influenza C viruses are true members of the influenza virus group.     

Polylactosaminoglycan modification of a small integral membrane glycoprotein, influenza B virus NB.

The structure of the carbohydrate components of NB, the small integral membrane glycoprotein of influenza B virus, was investigated. The carbohydrate chains of NB are processed from the high-mannose form (NB18) to a heterogeneous form of much higher molecular weight, designated NBp. Selection of this carbohydrate-containing form of NB with Datura stramonium lectin, its susceptibility to digestion by endo-beta-galactosidase, and determination of the size of NBp glycopeptides by gel filtration chromatography suggested that the increase in molecular weight is due to processing to polylactosaminoglycan. Investigation of the polypeptides produced by influenza B/Lee/40 virus infection of several cell types and another strain of influenza B virus suggested that the signal for modification to polylactosaminoglycan is contained in NB. Expression of mutants of NB lacking either one or both of the normal N-terminal sites of asparagine-linked glycosylation indicated that both carbohydrate chains are modified to contain polylactosaminoglycan. NBp and a small amount of unprocessed NB18 are expressed at the infected-cell surface, as determined by digestion of the surfaces of intact cells with various endoglycosidases. Unglycosylated NB, expressed either in influenza B virus-infected cells treated with tunicamycin or in cells expressing the NB mutant lacking both N-linked glycosylation sites, was expressed at the cell surface, indicating that NB does not require carbohydrate addition for transport.     

Role of neuraminidase in the morphogenesis of influenza B virus.

When ts7, a temperature-sensitive (ts) mutant of influenza B/Kanagawa/73 virus, infected MDCK cells at the nonpermissive temperature (37.5 degrees C), infectious virus was produced at very low levels compared with the yield at the permissive temperature (32 degrees C) and hemagglutinating activity and enzymatic activity of neuraminidase (NA) were negligible. However, viral protein synthesis and transport of hemadsorption-active hemagglutinin to the cell surface were not affected. When the cell lysate was treated with bacterial NA, hemagglutinating activity was recovered but infectivity was not, even after further treatment with trypsin. It was found that ts7 was defective in transport of NA to the cell surface and formation of virus particles. Analysis of the genomes of non-ts recombinants obtained by crossing ts7 and UV-inactivated B/Lee showed that ts7 had the ts mutation only in RNA segment 6 coding for NA and the glycoprotein NB. Nucleotide sequence analysis of the RNA segment revealed that ts7 had four amino acid changes in the NA molecule but not in NB. We suggest that assembly or budding of influenza B virus requires the presence of NA at the plasma membrane, unlike influenza A virus.     

Identification of hemagglutinin and neuraminidase genes of influenza B virus.

The genome of influenza B viruses was shown by electrophoresis to consist of eight RNA segments. The fifth largest segment coded for hemagglutinin and the sixth coded for neuraminidase.     

B型流感病毒研究进展

B型流感病毒为单股负链分节段RNA病毒,常在全球范围内以与A型流感病毒共流行的方式引起流感的局部暴发或季节性流行,对儿童、青少年、老人等特定人群易感,且感染儿童及青少年后引起的死亡率较高,给人类的公共卫生健康造成了严重威胁。B型流感病毒与A型相比更容易引发患者发生并发症,且其在流行季节造成的疾病负担甚至超过A型。近期,特别是2017年入冬后,B型流感病毒在我国的很多地区成为了引起流感发生的优势毒株,给人们的健康生活带来极大困扰。鉴于此,文中从B型流感病毒的结构、流行病学、免疫学及防治等方面进行了综述,旨在增强人们对该病毒的认识,为B型流感的防控提供借鉴和参考。     

Structural investigations of influenza B virus

Purified preparations of influenza B/Hong Kong/5/72 have been characterized by hydrodynamical measurements, electron microscopy and small-angle neutron scattering. As judged by these techniques the preparations are highly monodisperse, the virus particles being spherical and of molecular weight about 200 × 10⁶. The lipid bilayer is located at a radius of 425 Å and its molecular weight is estimated to be 60 × 10⁶, constituting about 30% of the total virus mass. The external radius is about 580 Å.     

Complete nucleotide sequence of the nucleoprotein gene of influenza B virus.

A DNA copy of influenza B/Singapore/222/79 viral RNA segment 5, containing the gene coding for the nucleoprotein (NP), has been cloned in Escherichia coli plasmid pBR322, and its nucleotide sequence has been determined. The influenza B NP gene contains 1,839 nucleotides and codes for a protein of 560 amino acids with a molecular weight of 61,593. Comparison of the influenza B NP amino acid sequence with that of influenza A NP (A/PR/8/34) reveals 37% direct homology in the aligned regions, indicating a common ancestor. However, influenza B NP has an additional 50 amino acids at its N-terminal end. As is the case with influenza A NP, influenza B NP is a basic protein, with its charged residues relatively evenly distributed rather than clustered. The structural homology suggests functional similarity between the NP of influenza A and B viruses.     

Characterization of a temperature-sensitive influenza B virus mutant defective in neuraminidase.

ts5, a temperature-sensitive mutant of influenza B virus, belongs to one of seven recombination groups. When the mutant infected MDCK cells at the nonpermissive temperature (37.5 degrees C), infectious virus was produced at very low levels compared with the yield at the permissive temperature (32 degrees C) and hemagglutinating and enzymatic activities were undetectable. However, viral protein synthesis and transport of hemagglutinin (HA) and neuraminidase (NA) to the cell surface were not affected. The NA was found as a monomer within cells even at 32 degrees C, in contrast to wild-type virus NA, existing mostly as an oligomer, but the mutant had oligomeric NA, like the wild-type virus. Its enzymatic activity was more thermolabile than that of wild-type virus. Despite the low yield, large aggregates of progeny virus particles were found to accumulate on the cell surface at the nonpermissive temperature, and these aggregates were broken by treatment with bacterial neuraminidase, with the concomitant appearance of hemagglutinating activity, suggesting that NA prevents the aggregation of progeny virus by removal of neuraminic acid from HA and cell receptor, allowing its release from the cells. Further treatment with trypsin resulted in the recovery of infectivity. When bacterial NA was added to the culture early in infection, many hemagglutinable infectious virus was produced. We also suggest that the removal of neuraminic acid from HA by NA is essential for the subsequent cleavage of HA by cellular protease. Nucleotide sequence analysis of RNA segment 6 revealed that ts5 encoded five amino acid changes in the NA molecule but not in NB.     

The Canadian influenza decision, 1976.

This paper explains the Canadian decision process following the isolation and identification of A/New Jersey/8/76 at Fort Dix, New Jersey in February 1976. The cause for concern was the emergence of a swine-like strain related to that which caused the 1918-19 pandemic, together with proved man-to-man transmission. This concern was reinforced since all new influenza A strains known to have infected the number of persons involved at Fort Dix have become strains of epidemic importance. The Fort Dix outbreak gave sufficient warning to allow implementation of a national vaccination program, to prevent and protect against influenza. In the past such an opportunity had not occurred, and vaccine use had, at best, constituted an intervention in the course of an outbreak. The National Advisory Committee on Immunizing Agents had all available information when it reached its decision to recommend vaccination with bivalent (A/Victoria and A/New Jersey) or with monovalent (A/New Jersey) vaccine for selective, high-risk groups. This was an independent, scientifically based decision.     

乙型、丙型流感病毒的长记忆ARFIMA模型

用时间序列模型来分析乙型、丙型这两种流感病毒,对乙流、丙流病毒DNA序列提供了一种新的时间序列模型,即CGR弧度序列。利用CGR坐标将乙流、丙流病毒DNA序列转换成CGR弧度序列,且引入长记忆ARFIMA模型去拟合这两类序列。发现随机找来的10条乙流序列,10条丙流序列都具有长相关性且拟合很好,并且还发现这两种病毒序列可以尝试用不同的ARFIMA模型ARFIMA(0,d,4)模型,ARFIMA(1,d,1)模型去识别。     

Chimeric influenza A viruses with a functional influenza B virus neuraminidase or hemagglutinin

Reassortment of influenza A and B viruses has never been observed in vivo or in vitro. Using reverse genetics techniques, we generated recombinant influenza A/WSN/33 (WSN) viruses carrying the neuraminidase (NA) of influenza B virus. Chimeric viruses expressing the full-length influenza B/Yamagata/16/88 virus NA grew to titers similar to that of wild-type influenza WSN virus. Recombinant viruses in which the cytoplasmic tail or the cytoplasmic tail and the transmembrane domain of the type B NA were replaced with those of the type A NA were impaired in tissue culture. This finding correlates with reduced NA content in virions. We also generated a recombinant influenza A virus expressing a chimeric hemagglutinin (HA) protein in which the ectodomain is derived from type B/Yamagata/16/88 virus HA, whereas both the cytoplasmic and the transmembrane domains are derived from type A/WSN virus HA. This A/B chimeric HA virus did not grow efficiently in MDCK cells. However, after serial passage we obtained a virus population that grew to titers as high as wild-type influenza A virus in MDCK cells. One amino acid change in position 545 (H545Y) was found to be responsible for the enhanced growth characteristics of the passaged virus. Taken together, we show here that the absence of reassortment between influenza viruses belonging to different A and B types is not due to spike glycoprotein incompatibility at the level of the full-length NA or of the HA ectodomain.     

Transmembrane peptide NB of influenza B: a simulation, structure, and conductance study

The putative transmembrane segment of the ion channel forming peptide NB from influenza B was synthesized by standard solid-phase peptide synthesis. Insertion into the planar lipid bilayer revealed ion channel activity with conductance levels of 20, 61, 107, and 142 pS in a 0.5 M KCl buffer solution. In addition, levels at -100 mV show conductances of 251 and 413 pS. A linear current-voltage relation reveals a voltage-independent channel formation. In methanol and in vesicles the peptide appears to adopt an alpha-helical-like structure. Computational models of alpha-helix bundles using N = 4, 5, and 6 NB peptides per bundle revealed water-filled pores after 1 ns of MD simulation in a solvated lipid bilayer. Calculated conductance values [using HOLE (Smart et al. (1997) Biophys. J. 72, 1109-1126)] of ca. 20, 60, and 90 pS, respectively, suggested that the multiple conductance levels seen experimentally must correspond to different degrees of oligomerization of the peptide to form channels.