Speculation on Pathogenesis in Death from Respiratory Syncytial Virus Infection

The lungs of three infants, two with bronchiolitis and one with pneumonia, were examined by fluorescent antibody techniques for the distribution of respiratory syncytial (R.S.) virus, and also for the presence of human globulin. In bronchiolitis the lungs contained little virus, whereas in pneumonia virus was abundant and widespread; and, paradoxically, while in bronchiolitis human globulin had the same scanty distribution as virus it was absent in pneumonia. It is suggested that the essential process in bronchiolitis is a widespread type 1 allergic reaction dependent on a second encounter with R.S. virus antigen, whereas in R.S. virus pneumonia the mucosal necrosis and alveolar and interstitial inflammation are the result of direct virus damage to the lungs. The alternative explanation put forward is that the process may be a type 3 allergic reaction.     

Respiratory Syncytial Virus in Hospital Cross-infection

During an epidemic of respiratory syncytial (R.S.) virus in Newcastle upon Tyne 13 children developed R.S. virus infections while in hospital with other conditions. R.S. virus infection was also noted in four members of the staff. In two of the hospital wards outbreaks developed. All children infected with R.S. virus developed symptoms. The symptoms varied with age; two children aged 2 months or less developed colds, as did five children over 1 year of age. One child of 15 months with Werdnig-Hoffman disease, though suffering from a cold, later developed pulmonary collapse. All five children aged 3 to 8 months developed bronchiolitis. The effectiveness of special nursing in cubicles was probably diminished because adults with mild colds were excreting virus. The dangers of R.S. virus infection to other children in the ward, especially those with congenital heart disease, is emphasized.     

Respiratory viruses and sudden infant death.

Viruses were shown to be present in the respiratory tract in 200 of 763 cases of the sudden infant death syndrome studied in the nine years 1974-82. Epidemiological and pathological evidence suggested that the distribution of viruses in the sudden infant death syndrome differs between infants aged 3 months or less and those aged over 3 months: the incidence of detection of virus was 14% in the younger group compared with 39% in the older group. The distribution of the viruses in these two groups was compared with that in 1341 live infants with respiratory virus infections. Adenovirus, influenza virus, parainfluenza virus, and rhinovirus had similar distribution among the victims of the sudden infant death syndrome and live controls. The incidence of detection of respiratory syncytial virus was increased in the older infants dying of the sudden infant death syndrome (90% of the cases detected) compared with the older group of live infants (53%). Antibody studies, detection of virus, and epidemiological data suggest that respiratory syncytial virus may be a precipitating factor of sudden death in older infants.     

Acute Respiratory Infections in Children: Part II. A Trial of Polyvalent Virus Vaccine

A new polyvalent respiratory virus vaccine has been evaluated in a double-blind trial involving infants and children. Five hundred and sixteen healthy infants and children were given either nine-strain polyvalent respiratory virus vaccine or placebo. The vaccine contained four Influenza strains, three Adenovirus strains and two Parainfluenza strains. Serologic studies revealed that persistent protective antibody levels were achieved with only the Asian Influenza component.The children were followed up clinically for a one-year period and each respiratory illness was recorded. No protection appeared to have been conferred by the vaccine, and indeed a significantly greater number of respiratory illnesses occurred among the vaccinated group.     

Acute Respiratory Infections in Children: I. An Intensive Study of Etiology in an Open Community

During a seven-month period from November 1960 to May 1961, 181 infants and children, hospitalized because of acute respiratory infections, were studied intensively to determine the responsible etiologic agents. Forty-two per cent of the illnesses in this group appeared to be caused by bacterial agents, either primary or secondary to virus. Parainfluenza viruses were identified as causes of laryngotracheobronchitis in nearly 50% of the cases. Adenoviruses were also found to be important pathogens, particularly as causes of pneumonia in infants. The over-all infection rate attributed to adenoviruses was 11.6%. An epidemic due to Influenza B virus affected approximately 40% of children in this city just following the hospital study. This study was conducted as the first step in a long-term project undertaken at the Regina General Hospital to determine the effectiveness of vaccines in the prevention and treatment of respiratory infections in children.     

Nucleic acids of respiratory syncytial virus.

Analysis of purified respiratory syncytial virus revealed that the virion RNA was composed of 50S, 28S, 18S, and 4S species. The 18S and 28S species were presumed to represent host rRNA since virus grown in actinomycin D-treated cells contained only 50S and 4S RNAs. Actinomycin D treatment stimulated production of infectious respiratory syncytial virus 5- to 10-fold. The 50S virion RNA was shown to hybridize with polyadenylated mRNA's isolated from infected cells, indicating that respiratory syncytial virus RNA is of negative-strand sense. Six mRNA's were identified by polyacrylamide gel electrophoresis.     

Identification of human parainfluenza virus type 2 (HPIV-2) V protein amino acid residues that reduce binding of V to MDA5 and attenuate HPIV-2 replication in nonhuman primates

Human parainfluenza virus type 2 (HPIV-2), an important pediatric respiratory pathogen, encodes a V protein that inhibits type I interferon (IFN) induction and signaling. Using reverse genetics, we attempted the recovery of a panel of V mutant viruses that individually contained one of six cysteine-to-serine (residues 193, 197, 209, 211, 214, and 218) substitutions, one of two paired charge-to-alanine (R175A/R176A and R205A/K206A) substitutions, or a histidine-to-phenylalanine (H174F) substitution. This mutagenesis was performed using a cDNA-derived HPIV-2 virus that expressed the V and P coding sequences from separate mRNAs. Of the cysteine substitutions, only C193S, C214S, and C218S yielded viable virus, and only the C214S mutant replicated well enough for further analysis. The H174F, R175A/R176A, and R205A/K206A mutants were viable and replicated well. The H174F and R205A/K206A mutants did not differ from the wild-type (WT) V in their ability to physically interact with MDA5, a cytoplasmic sensor of nonself RNA that induces type I IFN. Like WT HPIV-2, these mutants inhibited IFN-β induction and replicated efficiently in African green monkeys (AGMs). In contrast, the C214S and R175A/R176A mutants did not bind MDA5 efficiently, did not inhibit interferon regulatory factor 3 (IRF3) dimerization or IFN-β induction, and were attenuated in AGMs. These findings indicate that V binding to MDA5 is important for HPIV-2 virulence in nonhuman primates and that some V protein residues involved in MDA5 binding are not essential for efficient HPIV-2 growth in vitro. Using a transient expression system, 20 additional mutant V proteins were screened for MDA5 binding, and the region spanning residues 175 to 180 was found to be essential for this activity.     

Mucosal immune responses to infections in infants with acute life threatening events classified as 'near-miss' sudden infant death syndrome

This study examined the hypothesis that dysregulation of mucosal immune responses to respiratory infections is a critical event, which could be causal in respiratory arrest of some previously healthy infants. To examine this hypothesis, a prospective study was undertaken of infants presenting to the emergency department of a major teaching hospital with acute life threatening events (ALTE) of unknown cause and classified as "near-miss" SIDS. Salivary immunoglobulin concentrations were measured on admission and again after 14 days. The salivary immunoglobulins were compared with three control groups: infants with a mild upper respiratory tract infection (URTI); bronchiolitis; and healthy age-matched infants. The salivary IgA and IgM concentrations in the ALTE infants at presentation to hospital indicated a significant mucosal immune response had already occurred, with nearly 60% of the IgA concentrations significantly above the population-based reference ranges. The hyper-immune response was most evident in the ALTE infants with pathology evidence of an infection; 87% of these infants had salivary IgA concentrations on average 10 times higher that the age-related median concentration. The most prevalent pathogen identified in the ALTE infants was respiratory syncytial virus (RSV) (64%). RSV was also identified in all subjects with bronchiolitis. Risk factors for SIDS were assessed in each group. The data indicated that the ALTE infants diagnosed as 'near-miss' SIDS were a relatively homogeneous group, and most likely these ALTE infants and SIDS represent associated clinical outcomes. The study identified exposure to cigarette smoke and elevated salivary IgA concentrations as predictors of an ALTE. The study findings support the hypothesis of mucosal immune dysregulation in response to a respiratory infection in some infants with an ALTE. They provide a plausible explanation for certain SIDS risk factors. The underlying patho-physiological mechanism of proinflammatory responses to infections during a critical developmental period might be a critical factor in infants who have life-threatening apnoea or succumb to SIDS. The study raises the possibility of using salivary IgA to test infants who present with mild respiratory infections to identify a substantial number of infants at risk of developing an ALTE or SIDS, thus enabling intervention management to prevent such outcomes.     

Atopy predisposing to acute bronchiolitis during an epidemic of respiratory syncytial virus.

Thirty-one infants admitted to hospital with acute bronchiolitis during an epidemic of respiratory syncytial virus were compared with a control group of 32 infants to establish whether the two groups differed in atopic background. Past history of respiratory illness, eczema, and present reactions to skin testing differed significantly between the two groups. Thus, infants with acute bronchiolitis had a significantly higher atopic predisposition than the controls.     

Studies with bovine parainfluenza - 3 virus in u.a.R. (Egypt)

A bovine strain of myxovirus parainfluenza-3 (MP3) virus, designated S virus, was isolated from lung tissue collected from cattle with respiratory illness in 1963. The virus agglutinates mammalian and avian erythrocytes, and is sensitive to ether, sodium desoxycholate and trypsin. It grows in primary calf kidney, buffalo kidney, dog kidney, camel kidney and MS cell cultures. The S virus forms well-defined plaques in buffalo and calf kidney cells on the 5th or 6th day after inoculation. Examination of cell cultures following inoculation with S virus revealed giant cell formation, and introcytoplasmic and intranuclear inclusions. At 37 degrees C the virus titer dropped from 10(10.4) to 10(2.6) in 3 days. Virus was completely inactivated at 56 degrees C within 15 minutes. Growth-curve studies in tissue culture monolayer cells revealed a latent period of 10 hours. The intracellular virus titer was slightly lower than that of extracellular virus. The isolate was identified as MP3 virus by serum neutralization and hemagglutination-inhibition tests. Antibodies (HI) to S virus were shown to be present in a significant proportion of Egyptian cattle. The epidemiological significance of MP3 (bovine strain) virus in U.A.R. is discussed.     

Targeted Recombination Demonstrates that the Spike Gene of Transmissible Gastroenteritis Coronavirus Is a Determinant of Its Enteric Tropism and Virulence

Targeted recombination within the S (spike) gene of transmissible gastroenteritis coronavirus (TGEV) was promoted by passage of helper respiratory virus isolates in cells transfected with a TGEV-derived defective minigenome carrying the S gene from an enteric isolate. The minigenome was efficiently replicated in trans and packaged by the helper virus, leading to the formation of true recombinant and pseudorecombinant viruses containing the S proteins of both enteric and respiratory TGEV strains in their envelopes. The recombinants acquired an enteric tropism, and their analysis showed that they were generated by homologous recombination that implied a double crossover in the S gene resulting in replacement of most of the respiratory, attenuated strain S gene (nucleotides 96 to 3700) by the S gene of the enteric, virulent isolate. The recombinant virus was virulent and rapidly evolved in swine testis cells by the introduction of point mutations and in-phase codon deletions in a domain of the S gene (nucleotides 217 to 665) previously implicated in the tropism of TGEV. The helper virus, with an original respiratory tropism, was also found in the enteric tract, probably because pseudorecombinant viruses carrying the spike proteins from the respiratory strain and the enteric virus in their envelopes were formed. These results demonstrated that a change in the tropism and virulence of TGEV can be engineered by sequence changes in the S gene.     

Immunoglobulin Classes of Serum Antibodies Formed in Response to Natural Infections with Myxo- and Pseudomyxoviruses among Infants and Children

The occurrence of immunoglobulin classes of serum antibody in response to natural infections with myxo- and pseudomyxoviruses among infants and children was investigated. Two types of the 19S antibody response have been demonstrated. In the first type, in which are included the measles and mumps virus infections, the 19S antibody appeared dominantly as a primary response to the virus infection. In the second type, which includes the influenza, parainfluenza and RS virus infections, the 19S antibody was either not detectable or produced in a limiting amount in infants even at an early stage of the illnesses. A possibility was discussed that production of the 19S antibody in response to the infection with myxo- and pseudomyxoviruses may be primarily determined by the nature of virus infection itself, particularly the presence or absence of a viremia.     

Saffold virus, a novel human Cardiovirus with unknown pathogenicity

Although cardioviruses have been thought to mainly infect rodents, a novel human cardiovirus, designated Saffold virus (SAFV), was identified in 2007. SAFV is grouped with Theiler-like rat virus and Theiler's murine encephalomyelitis virus (TMEV) in the species Theilovirus of the genus Cardiovirus of the family Picornaviridae. Eight genotypes of SAFV have now been identified. SAFV has been isolated from nasal and stool specimens from infants presenting with respiratory and gastrointestinal symptoms as well as from children with nonpolio acute flaccid paralysis; however, the relationship of SAFV to this symptomatology remains unclear. Of note, the virus has also been isolated from the cerebrospinal fluid specimens of patients with aseptic meningitis. This finding is of interest since TMEV is known to cause a multiple sclerosis-like syndrome in mice. The involvement of SAFV in various diseases (e.g., respiratory illness, gastrointestinal illness, neurological diseases, and type I diabetes) is presently under investigation. In order to clarify the pathogenicity of SAFV, additional epidemiological studies are required. Furthermore, identification of the SAFV cellular receptor will help establish an animal model for SAFV infection and help clarify the pathogenesis of SAFV-related diseases. In addition, investigation of the tissue-specific expression of the receptor may facilitate development of a novel picornavirus vector, which could be a useful tool in gene therapy for humans. The study of viral factors involved in viral pathogenicity using a reverse genetics technique will also be important.     

Persistent airway hyperresponsiveness after neonatal viral bronchiolitis in rats.

Viral bronchiolitis in human infants has been associated with permanent changes in small airways and gas exchange and an increased incidence of hyperresponsive airways later in life. Respiratory infection by Sendai virus in neonatal rats also has been reported to cause permanent changes in lung morphology and increased numbers of bronchiolar mast cells and eosinophils. We evaluated pulmonary mechanics, gas exchange, and airway responsiveness in rats at 7 and 13-16 wk after neonatal Sendai virus infection. Rats from the virus group had lower arterial PO2 and increased total lung resistance compared with controls. There were no significant differences between groups for arterial PCO2, dynamic lung compliance, quasi-static respiratory system compliance, or vital capacity. Rats from the infected group were significantly more sensitive to aerosolized methacholine than were controls, although both virus and control groups became less sensitive with age. We conclude that neonatal Sendai virus infection in rats results in persistent alterations in lung function and airway responsiveness. This phenomenon may be valuable for the study of the relationships among airway inflammation, lung morphology, and airway hyperresponsiveness, and it may be relevant to human airway disease.     

The S190R mutation in the hemagglutinin protein of pandemic H1N1 2009 influenza virus increased its pathogenicity in mice

Human influenza viruses preferentially bind to sialic acid-α2,6-galactose (SAα2,6Gal) receptors, which are predominant in human upper respiratory epithelia, whereas avian influenza viruses preferentially bind to SAα2,3Gal receptors. However, variants with amino acid substitutions around the receptor-binding sites of the hemagglutinin (HA) protein can be selected after several passages of human influenza viruses from patients’ respiratory samples in the allantoic cavities of embryonated chicken eggs. In this study, we detected an egg-adapted HA S190R mutation in the pandemic H1N1 virus 2009 (pdmH1N1), and evaluated the effects of this mutation on receptor binding affinity and pathogenicity in mice. Our results revealed that residue 190 is located within the pocket structure of the receptor binding site. The single mutation to arginine at position 190 slightly increased the binding affinity of the virus to the avian receptor and decreased its binding to the long human α2,6-linked sialic acid receptor. Our study demonstrated that the S190R mutation resulted in earlier death and higher weight loss in mice compared with the wild-type virus. Higher viral titers at 1 dpi (days post infection) and diffuse damage at 4 dpi were observed in the lung tissues of mice infected with the mutant virus.     

The core of the respiratory syncytial virus fusion protein is a trimeric coiled coil

Entry into the host cell by enveloped viruses is mediated by fusion (F) or transmembrane glycoproteins. Many of these proteins share a fold comprising a trimer of antiparallel coiled-coil heterodimers, where the heterodimers are formed by two discontinuous heptad repeat motifs within the proteolytically processed chain. The F protein of human respiratory syncytial virus (RSV; the major cause of lower respiratory tract infections in infants) contains two corresponding regions that are predicted to form coiled coils (HR1 and HR2), together with a third predicted heptad repeat (HR3) located in a nonhomologous position. In order to probe the structures of these three domains and ascertain the nature of the interactions between them, we have studied the isolated HR1, HR2, and HR3 domains of RSV F by using a range of biophysical techniques, including circular dichroism, nuclear magnetic resonance spectroscopy, and sedimentation equilibrium. HR1 forms a symmetrical, trimeric coiled coil in solution (K(3) approximately 2.2 x 10(11) M(-2)) which interacts with HR2 to form a 3:3 hexamer. The HR1-HR2 interaction domains have been mapped using limited proteolysis, reversed-phase high-performance liquid chromatography, and electrospray-mass spectrometry. HR2 in isolation exists as a largely unstructured monomer, although it exhibits a tendency to form aggregates with beta-sheet-like characteristics. Only a small increase in alpha-helical content was observed upon the formation of the hexamer. This suggests that the RSV F glycoprotein contains a domain that closely resembles the core structure of the simian parainfluenza virus 5 fusion protein (K. A. Baker, R. E. Dutch, R. A. Lamb, and T. S. Jardetzky, Mol. Cell 3:309-319, 1999). Finally, HR3 forms weak alpha-helical homodimers that do not appear to interact with HR1, HR2, or the HR1-HR2 complex. The results of these studies support the idea that viral fusion proteins have a common core architecture.     

单克隆抗体在呼吸道合胞病毒感染诊断和防治中的应用

呼吸道合胞病毒 (RSV)是世界范围内婴幼儿下呼吸道感染的重要病原 ,目前尚无成熟疫苗应用于临床。展开对RSV被动免疫的研究显得尤为重要。单克隆抗体成为深入研究和防治RSV感染的有力武器。本文综述了单克隆抗体在RSV感染的诊断、预防和治疗中的应用     

沈阳地区婴幼儿RSV感染的病原学调查研究

查明冬春季沈阳地区婴幼儿RSV感染流行情况.采用APAAP法和IFA法对65例临床诊断为急性病毒性下呼吸道感染的婴幼儿进行了检查.在RSV感染的高发季节由RSV引起婴幼儿的急性下呼吸道感染的阳性率为44.60%(29/65),0～6个月婴幼儿感染率最高,为74.07%(20/27),并有明显的喘息倾向.以上结果表明RSV仍是引起婴幼儿急性下呼吸道感染,特别是肺炎和毛细支气管炎的重要病原体,沈阳地区仍有流行.为防止和控制RSV的流行及为RSV的防治提供了依据.