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Nucleotide sequence of the coding and flanking regions of the human parainfluenza virus type 3 fusion glycoprotein gene.

The complete nucleotide sequence of the human parainfluenza virus type 3 (HPIV3) fusion (F) protein gene has been determined. The HPIV3 F gene is 1851 nucleotides long including six U residues in the genomic RNA, which probably direct synthesis of the first few nucleotides in the F mRNA polyadenylate tail. The HPIV3 F gene contains a single long open reading frame coding for 539 amino acids. The predicted molecular weight of the unglycosylated precursor F0 protein was 60031. Four potential carbohydrate acceptor sites were identified. Comparison of the HPIV3 F protein sequence with the F gene sequences of two other paramyxoviruses, Sendai virus and simian virus 5, indicated a very close evolutionary relationship between HPIV3 and Sendai virus. Sequence analysis of HPIV3 F gene flanking regions identified signals which appear to be responsible for polymerase recognition and polyadenylation.

Amino Acid Sequence↗

Relative affinity of the human parainfluenza virus type 3 hemagglutinin-neuraminidase for sialic acid correlates with virus-induced fusion activity.

The ability of enveloped viruses to cause disease depends on their ability to enter the host cell via membrane fusion events. An understanding of these early events in infection, crucial for the design of methods of blocking infection, is needed for viruses that mediate membrane fusion at neutral pH, such as paramyxoviruses and human immunodeficiency virus. Sialic acid is the receptor for the human parainfluenza virus type 3 (HPF3) hemagglutinin-neuraminidase (HN) glycoprotein, the molecule responsible for binding of the virus to cell surfaces. In order for the fusion protein (F) of HPF3 to promote membrane fusion, the HN must interact with its receptor. In the present report, two variants of HPF3 with increased fusion-promoting phenotypes were selected and used to study the function of the HN glycoprotein in membrane fusion. Increased fusogenicity correlated with single amino acid changes in the HN protein that resulted in increased binding of the variant viruses to the sialic acid receptor. These results suggest that the avidity of binding of the HN protein to its receptor regulates the level of F protein-mediated fusion and begin to define one role of the receptor-binding protein of a paramyxovirus in the membrane fusion process.

Animals↗

Viral RNA and protein synthesis in two LLC-MK2 cell lines persistently infected with human parainfluenza virus 3.

Two lines of LLC-MK2 cells persistently infected with human parainfluenza virus 3 (HPIV-3) have been maintained in culture for approximately 3 years. Subgenomic RNAs (putative defective interfering particle genomes) were detected in virions released from both persistently infected cultures. In one of the persistently infected cell lines cyclic variation in the production of virions containing standard virus genomic-size (50S) RNA and subgenomic RNA was observed. The molar ratio of subgenomic RNA to 50S RNA ranged from less than 0.1/1 to 8.7/1. Northern blot analyses revealed that the patterns of viral mRNA synthesis in persistently infected cells from both cultures were similar to those of standard virus infected cells. Furthermore, the intracellular viral-specific proteins had electrophoretic mobilities similar to the corresponding proteins in standard virus-infected cells. Nucleotide sequence analysis of cloned M gene from virus after 29 months of persistence (147 passages) revealed only one variable conservative amino acid change in two clones analyzed from each cell line, indicating that the M protein is not likely to be involved in the maintenance of the persistent infections. The possible mechanisms by which the persistent state is maintained are discussed.

Cell Line↗

Clinical courses of croup caused by influenza and parainfluenza viruses.

Influenza viruses have occasionally been associated with severe manifestations of croup, but no comparative studies of different viral etiologies are available. In a retrospective study we compared the clinical courses of croup caused by influenza and parainfluenza viruses in hospitalized children. By several indicators the clinical picture of croup caused by influenza viruses was significantly more severe than that caused by parainfluenza viruses.

Child↗

Antiviral activity of Sanicula europaea L. extracts on multiplication of human parainfluenza virus type 2.

The antiviral activity of Sanicula europaea L. extracts against human parainfluenza virus type 2 (HPIV-2) was examined. The extract prepared from the leaves of the plant and a fraction separated from the crude extract with gel filtration chromatography were found to inhibit HPIV-2 replication without any toxic effect on Vero cells. The acidic fraction obtained from the crude extract of S. europaea leaves was found to be the most active fraction with plaque inhibition assay at non-cytotoxic concentrations. Unfortunately, antiviral activity was not detected in the molecules purified from the crude ethanol extract of Sanicula leaves.

Animals↗

Comparison of different tissue cultures for isolation and quantitation of influenza and parainfluenza viruses.

Rhesus and cynomolgus monkey kidney tissue cultures and two continuous lines, Madin-Darby canine kidney (MDCK) and LLC-MK2, were compared in titrations and isolations of influenza and parainfluenza viruses. Tube cultures were inoculated with laboratory virus strains or stored patient specimens and observed for hemadsorption. Trypsin was added to the medium of the continuous lines to increase sensitivity. All four tissue cultures gave similar titers of influenza A/USSR (H1N1), A/Texas (H3N2), and B/HK, but lower titers of parainfluenza 1, 2, and 3 were observed with MDCK. Cynomolgus kidney was the best single tissue culture for reisolation of the six viruses, but foamy-virus contamination of many lots was a serious problem. Reisolation of influenza viruses was as successful with MDCK as with primary monkey kidney. LLC-MK2 was similar to rhesus kidney but less successful than cynomolgus kidney. For reisolation of parainfluenza viruses, LLC-MK2 was superior to rhesus monkey kidney and similar to cynomolgus kidney. MDCK was less useful for parainfluenza viruses. Thus, LLC-MK2 would be an acceptable single tissue alternative to primary monkey kidney. The combination of MDCK and LLC-MK2 would provide optimal sensitivity for isolation of all six viruses.

Animals↗

On the role of the response of the cell membrane in determining virus virulence. Contrasting effects of the parainfluenza virus SV5 in two cell types.

The simian myxovirus SV5 multiplies in a continuous line of baby hamster kidney (BHK21-F) cells causing extensive cell fusion, followed by cell death. After inoculation of 15 PFU/cell, the latent period was 7 hr, the doubling time approximately 60 min, and the yield 7 PFU per cell. Giant cell formation began about 6 hr after infection and rapidly progressed to the formation by 14 to 18 hr of a single syncytium which disintegrated by 24 to 36 hr. In contrast, SV5 multiplies in primary rhesus monkey kidney cells for long periods of time producing high yields of virus with little cytopathic effect. High multiplicities of SV5 induced cell fusion in BHK21-F cells within 1 hr in the absence of virus multiplication but had no visible effect on monkey kidney cells. Time-lapse photomicrography has demonstrated that giant cells form by fusion of infected cells, and that some polykaryocytes divide. During aberrant division of polykaryocytes giant nuclei are formed from the nuclear material of several parent nuclei. The cytoplasmic development of viral antigens as demonstrated by immunofluorescence is similar in BHK21-F and monkey kidney cells. Synthesis of cellular DNA, RNA, and protein in monkey kidney cells is not shut off by SV5-infection, and in BHK21-F cells synthesis of these macromolecules is not inhibited until after extensive cell fusion has occurred 12 to 15 hr after infection. Persistently infected BHK21-F and monkey kidney cells have been serially carried through 11 and 28 cell passages, respectively. The results suggest that whether SV5 acts as a moderate virus, as in monkey kidney cells, or a virulent virus, as in BHK21-F cells, depends on the response of the cell membrane to the virus.

Animals↗

Persistent infection with human parainfluenza virus 3 in CV-1 cells: analysis of the role of defective interfering particles.

Persistent infection of cultured cells with human parainfluenza virus type 3 (HPF3), established following infection at high multiplicity, has been associated with the presence of one or more viral defective-interfering (DI) particles in addition to standard viral genomes. We recently showed that persistent infection can also be established after low multiplicity infection, a condition not generally associated with amplification of DI particles. The association of DI particle genomes with persistent infection was therefore studied after infection with low multiplicity. Persistently infected cell cultures were established after low multiplicity infection with HPF3 in the presence of exogenous bacterial neuraminidase, and viral nucleocapsid RNA was analyzed for the presence of DI genomes at each passage after infection. In addition, the timing of DI particle appearance was assessed after infection with high multiplicity, a condition known to favor the amplification of DI particles. DI particles genomes did not appear until at least seven passages of persistently infected cell cultures, after either low or high multiplicity infection. Our data suggest that DI particles are not required for establishment of persistent infection of CV-1 cells by HPF3 and that DI particles are not generated early in infection. Despite reports of the association of paramyxovirus DI particles with persistent infection in culture, the role of these particles in HPF3 persistence is unknown; our findings offer insight into the complex interplay of viral and host factors in persistent infection.

Blotting, Northern↗

The use of MDCK, MEK and LLC-MK2 cell lines with enzyme immunoassay for the isolation of influenza and parainfluenza viruses from clinical specimens.

Primary Monkey Kidney (PMK) epithelial cells or egg inoculation have been traditionally used for the culture of influenza and parainfluenza viruses. The high cost and variability of obtaining high quality PMK cells prompted us to investigate the use of other cell strains for the growth of these viruses. For this study we investigated three cell lines viz. MDCK, MEK and LLC-MK2 for the culture of influenza A and B and parainfluenza 1, 2 and 3 viruses. Clinical specimens were spun onto cell monolayers in microtitre wells. The growth of these viruses was then identified by specific antibodies in an enzyme immunoassay (EIA). The LLC-MK2 and MDCK cell lines were found to provide optimal growth of parainfluenza and influenza viruses respectively. During the period from November, 1990 to July, 1992, 6501 respiratory specimens were tested. There were 100 influenza A, 36 influenza B and 261 parainfluenza virus isolates. The influenza isolates were further subtyped by the WHO Influenza Reference Centre. The use of these cell lines and the EIA provided an effective method for the routine culture of these viruses.

Animals↗

Presence of a unique parainfluenza virus 3 strain identified by RT-PCR in visna-maedi virus infected sheep.

The presence in farm sheep of a paramyxovirus closely related to parainfluenza virus type 3 (Pi3) from humans or cattle was confirmed using RT-PCR on RNA samples from lung cells from slaughtered animals. Sequencing and restriction enzyme patterns of the amplified fragment of the F gene confirms the distinctness of the isolate, and suitable PCR primers allow specific detection of the ovine virus. A study of the incidence of ovine Pi3 in samples from sheep with or without distinctive histopathological signs of maedi shows that it is uncommon in aged sheep with overt lentiviral disease, but it occurs at moderate frequency in lambs and may, in the presence of visna-maedi virus, contribute to early lesion formation.

Abattoirs↗

The hemagglutinin-neuraminidase glycoproteins of human parainfluenza virus type 1 and Sendai virus have high structure-function similarity with limited antigenic cross-reactivity.

Human parainfluenza virus type 1 (hPIV-1) is closely related to Sendai virus on the basis of cross-reactivity of antisera. We examined this association further by using monoclonal antibodies to the Sendai virus hemagglutinin-neuraminidase (HN) glycoprotein to determine the relationship between overall protein structure and the hemagglutination and neuraminidase functions. Of 10 monoclonal antibodies representing four nonoverlapping antigenic sites on the HN of Sendai virus, only 4 from two sites cross-reacted with hPIV-1, indicating a limited conservation of epitopes. One of these four inhibited the hemagglutinating activity of hPIV-1 comparably to Sendai virus, but none appreciably inhibited the neuraminidase activity of hPIV-1. The ability of some of these monoclonal antibodies to inhibit only hemagglutinating or neuraminidase activity of either virus provided evidence for two separate active sites on the HN molecule. To determine the overall structural relationship of the HNs of hPIV-1 and Sendai virus, we cloned and sequenced the HN gene of hPIV-1. The HN clone was made from genomic RNA and was identified by hybrid-arrested in vitro translation of mRNA. The predicted HN protein sequence of hPIV-1 was identical in length to that of Sendai virus and had a shared identity of 72%. There was a marked conservation of structural elements (cysteines, prolines, and glycines), which would predict a similar molecular conformation. However, there were 10 potential glycosylation sites on the HN of hPIV-1, compared with 5 on Sendai virus. Some of these sites may be responsible for the inability of the Sendai virus monoclonal antibodies to cross-react. The results of our study support a close structure-function relationship between hPIV-1 and Sendai virus but suggest limited antigenic cross-reactivity.

Amino Acid Sequence↗

Properties of an encephalitogenic canine parainfluenza virus.

An isolate of canine parainfluenza (CPI) virus from the cerebrospinal fluid of a dog with neurological dysfunction was characterized in vitro in comparison to a prototype strain of CPI virus, D008. The virus, designated 78-238 was found to be antigenically related to CPI virus (Manhatten strain) and simian virus 5 (SV5), but not to mumps virus (Enders strain). Ultrastructural observation of gradient-purified 78-238 virus revealed enveloped pleomorphic virions with helical nucleocapsid symmetry. Preliminary pathological studies indicated that 78-238 virus was encephalitogenic for gnotobiotic dogs when inoculated by the intracerebral route.

Animals↗

Recovery of a fully viable chimeric human parainfluenza virus (PIV) type 3 in which the hemagglutinin-neuraminidase and fusion glycoproteins have been replaced by those of PIV type 1.

The recent recovery of human parainfluenza virus type 3 (PIV3) from cDNA, together with the availability of a promising, highly characterized live attenuated PIV3 vaccine virus, suggested a novel strategy for the rapid development of comparable recombinant vaccine viruses for human PIV1 and PIV2. The strategy, illustrated here for PIV1, is to create chimeric viruses in which the two protective antigens, the hemagglutinin-neuraminidase (HN) and fusion (F) envelope glycoproteins, of an attenuated PIV3 variant are replaced by those of PIV1 or PIV2. As a first step, this has been achieved by using recombinant wild-type (wt) PIV3 as the recipient for PIV1 HN and F, engineered so that each PIV1 open reading frame is flanked by the existing PIV3 nontranslated regions and transcription signals. This yielded a viable chimeric recombinant virus, designated rPIV3-1, that encodes the PIV1 HN and F glycoproteins in the background of the wt PIV3 internal proteins. There were three noteworthy findings. First, in contrast to recently reported glycoprotein replacement chimeras of vesicular somatitis virus or measles virus, the PIV3-1 chimera replicates in LLC-MK2 cells and in the respiratory tract of hamsters as efficiently as its PIV1 and PIV3 parents. This is remarkable because the HN and F glycoproteins share only 43 and 47%, respectively, overall amino acid sequence identity between serotypes. In particular, the cytoplasmic tails share only 9 to 11% identity, suggesting that their presumed role in virion morphogenesis does not involve sequence-specific contacts. Second, rPIV3-1 was found to possess biological properties derived from each of its parent viruses. Specifically, it requires trypsin for efficient plaque formation in tissue culture, like its PIV1 parent but unlike PIV3. On the other hand, it causes an extensive cytopathic effect (CPE) in LLC-MK2 cultures which resembles that of its PIV3 parent but differs from that of its noncytopathic PIV1 parent. This latter finding indicates that the genetic basis for the CPE of PIV3 in tissue culture lies outside regions encoding the HN or F glycoprotein. Third, it should now be possible to rapidly develop a live attenuated PIV1 vaccine by the staged introduction of known, characterized attenuating mutations present in a live attenuated PIV3 vaccine candidate into the PIV3-1 cDNA followed by recovery of attenuated derivatives of rPIV3-1.

Animals↗

Identification of RNA-binding regions on the P and V proteins of human parainfluenza virus type 2.

We have shown that the P and V proteins of human parainfluenza virus type 2 (hPIV-2) bind to genomic RNA by using Northwestern blot analysis. To identify the RNA-binding regions on the P and V proteins, we used a set of deletion mutants produced in Escherichia coli. One region required for the RNA-binding was found in the P-V common domain (aa 1-82). Others were found in the P protein-specific region (aa 249-354) and the V protein-specific region (aa 176-225). In addition, we have shown that substitutions of some basic residues with alanines in these regions abrogate RNA-binding by the P or V proteins. Intriguingly, the P and V proteins of hPIV2 can selectively bind to the viral RNA under our experimental conditions.

Amino Acid Substitution↗

Messenger RNA encoding the phosphoprotein (P) gene of human parainfluenza virus 3 is bicistronic.

The complete nucleotide sequence of the phosphoprotein (P) mRNA of human parainfluenza virus 3 (PIV-3) was derived from two cDNA clones spanning almost the entire P gene. The mRNA, excluding the poly(A) tail, is 2014 nucleotides long and is bicistronic. The first open reading frame (ORF) codes for the phosphoprotein (P) of mol wt 68,860. Seven nucleotides downstream from the first AUG codon, in a +1 reading frame, there is an additional ORF which can code for a polypeptide of mol wt 23,266. The latter protein appears to be similar to the C proteins found in cells infected with several paramyxoviruses. Comparison of the predicted amino acid sequence of the P and C proteins of PIV-3 with the corresponding Sendai virus proteins reveals considerable homology at the C-terminal half. In contrast, the P and C proteins of PIV-3 share very little homology with the measles virus P and C proteins, respectively.

Amino Acid Sequence↗