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Haemagglutination inhibition antibodies in nasal secretions of persons after natural parainfluenza virus infection.

In 7 adults and 7 children with upper respiratory illness of parainfluenza aetiology, the virus was isolated in the acute phase from nasal washings or nasal smears in spite of high titres of haemagglutination inhibition (HI) antibodies in serum. By contrast, secretory HI antibodies were not demonstrated at the onset of illness in any of the patients, but their formation started early and the antibodies reached maximal levels about 10 days after onset of illness. The individual patients showed considerable differences in the dynamics of secretory antibody formation and especially in their persistence. In some of the patients, secretory antibodies were demonstrated as late as 12 months after the illness.

Adolescent↗

Homooligomerization of the hemagglutinin-neuraminidase glycoprotein of human parainfluenza virus type 3 occurs before the acquisition of correct intramolecular disulfide bonds and mature immunoreactivity.

The posttranslational maturation of the hemagglutinin-neuraminidase (HN) glycoprotein of human parainfluenza type 3 virus (PIV3) was investigated in pulse-chase experiments in which folding was monitored by immunoprecipitation with conformation-dependent antibodies and gel electrophoresis under nonreducing conditions and oligomerization was monitored by chemical cross-linking and sedimentation in sucrose gradients. The acquisition of mature immunoreactivity and the formation of correct intramolecular disulfide bonds were concurrent events, with half-times of approximately 10 to 15 min. The finding that newly synthesized HN had little reactivity with postinfection cotton rat serum or with most of the members of a panel of HN-specific monoclonal antibodies indicated that the major epitopes of the PIV3 HN protein are highly conformational in nature. Chemical cross-linking studies indicated that the mature HN protein is present in homoligomers, which are probably tetramers. These findings are consistent with recent observations for the HN protein of Sendai virus (S.D. Thompson, W.G. Laver, K.G. Murti, and A. Portner, J. Virol. 62:4653--4660, 1988; S. Vidal, G. Mottet, D. Kolakofsky, and L. Roux, J. Virol. 63:892--900, 1989). Surprisingly, analysis of pulse-labeled HN protein by sedimentation on sucrose gradients after labeling periods of as little as 2 min indicated that it was present intracellularly only in oligomeric form. The same results were obtained when the labeling period was preceded by a 1.5-h cycloheximide treatment to clear the endoplasmic reticulum of presynthesized HN protein, which indicated that the oligomerization did not involve the incorporation of newly synthesized monomers into partially assembled oligomers. Subsequent chase incubations did not significantly alter the sedimentation profile or stability of the oligomeric forms, suggesting that oligomers detected after short labeling periods were tetramers. Association with cellular proteins did not appear to be responsible for the sedimentation of newly synthesized HN protein as an oligomer. The absence of a detectable monomeric form of intracellular HN protein raised the possibility that oligomerization is cotranslational, and it is possible that the type II membrane orientation of the HN protein might be an important factor in its mode of oligomerization.

Antibodies, Monoclonal↗

Organ cultures of respiratory epithelium infected with rhinovirus or parainfluenza virus studied in a scanning electron microscope.

Organ cultures of bovine tracheal epithelium were infected with a rhinovirus or a strain of parainfluenza type 3 virus, and the epithelial surfaces were studied by scanning electron microscopy. When washed free from mucus, normal control cultures showed a thick carpet of normal cilia, whereas the two viruses each produced specific morphological abnormalities. In rhinovirus-infected cultures, degenerating ciliated and nonciliated cells with finely granular surfaces were rapidly extruded from the epithelium. The denuded epithelial surface was relatively smooth, and showed some evidence of squamous metaplasia. By contrast, in cultures infected with parainfluenza type 3 virus, damage developed more slowly and the epithelial surface was ultimately covered with a profuse array of short microvillous projections. In thin sections, some of these were shown to be the sites of viral maturation.

Animals↗

Enhanced pulmonary pathology in cotton rats upon challenge after immunization with inactivated parainfluenza virus 3 vaccines.

Vaccine-induced potentiation was studied in cotton rats immunized with formalin-inactivated human parainfluenza type 3, ultraviolet light-inactivated virus, or infection with live virus. Immunized animals and unimmunized controls were later challenged by intranasal inoculation of live virus and evaluated for pulmonary pathology 4 days later. Animals immunized with either of the inactivated vaccines developed marked peribronchiolitis, perivasculitis, and an alveolar cellular infiltration much more severe than seen in animals infected previously, or in unmanipulated but challenged animals. Disease enhancement after immunization with killed virus is thus a characteristic of a member of each of three genera of the family, Paramyxoviridae, and is not restricted to immunization with formalin-inactivated virus.

Animals↗

Enhanced surfactant protein and defensin mRNA levels and reduced viral replication during parainfluenza virus type 3 pneumonia in neonatal lambs.

Defensins and surfactant protein A (SP-A) and SP-D are antimicrobial components of the pulmonary innate immune system. The purpose of this study was to determine the extent to which parainfluenza type 3 virus infection in neonatal lambs alters expression of sheep beta-defensin 1 (SBD-1), SP-A, and SP-D, all of which are constitutively transcribed by respiratory epithelia. Parainfluenza type 3 viral antigen was detected by immunohistochemistry (IHC) in the bronchioles of all infected lambs 3 days postinoculation and at diminished levels 6 days postinoculation, but it was absent 17 days postinoculation. At all times postinoculation, lung homogenates from parainfluenza type 3 virus-inoculated animals had increased SBD-1, SP-A, and SP-D mRNA levels as detected by fluorogenic real-time reverse transcriptase PCR. Protein levels of SP-A in lung homogenates detected by quantitative-competitive enzyme-linked immunosorbent assay and protein antigen of SP-A detected by IHC were not altered. These studies demonstrate that parainfluenza type 3 virus infection results in enhanced expression of constitutively transcribed innate immune factors expressed by respiratory epithelia and that this increased expression occurs concurrently with decreased viral replication.

Animals↗

The L polymerase protein of parainfluenza virus 3 forms an oligomer and can interact with the heterologous Sendai virus L, P and C proteins.

We recently showed that the L protein of Sendai virus is present as an oligomer in the active P-L polymerase complex [Smallwood et al., Virology 304 (2002) 235]. We now demonstrate using two different epitope tags that the L protein of a second respirovirus, human parainfluenza type 3 virus (PIV3), also forms an L-L complex. L oligomerization requires the coexpression of the differentially epitope tagged L proteins. By exploiting a series of C-terminal truncations the L-L binding site maps to the N-terminal half of L. There is some complex formation between the heterologous PIV3 and Sendai L and P proteins; however, the heterologous L protein does not function in transcription of either the PIV3 or Sendai template. The PIV3 C protein binds PIV3 L and inhibits RNA synthesis in vitro and in vivo. Significant homology exists between the C proteins of PIV3 and Sendai and complex formation occurs between the PIV3 and Sendai heterologous C and L proteins. In addition, the heterologous C proteins can inhibit transcription at approximately 50% of the level of the homologous protein. These data suggest that while the C proteins may be functionally somewhat interchangeable, the L and P proteins are specific for each virus.

Animals↗