[A guinea pig model of parainfluenza virus type 3 infection-induced acute and postinfectious cough]

OBJECTIVE

To establish a guinea pig model of cough induced by human parainfluenza virus type 3 (PIV3) infection, and to investigate the change of the cough reflex sensitivity (CRS).

METHODS

Sixty male SPF guinea pigs were divided into 6 groups (n=10, each), namely, a normal control group, an asthma group and 4 groups of PIV3 inoculation which included post-infection day (PID) 6, 12, 28, and 42. Infected animals were inoculated by intranasal instillation of PIV3 suspension. Control animals were inoculated by uninfected cell culture medium. Asthma animals were sensitized and challenged by ovalbumin. The Buxco system was used to assess cough reflex sensitivity (CRS) elicited by capsaicin and airway hyper-reaction (AHR). Airway inflammation was studied by bronchoalveolar lavage (BAL) cytology and lung histopathology.

RESULTS

The CRS of PID 6, 12, 28 and 42 groups was 7.50 (5.25), 7.30 (7.25), 8.40 (9.75) and 8.20 (5.50) Cough counts (CCnt). Compared with 2.50 (3.00) CCnt of the vehicle group, the CRS to capsaicin increased significantly in all the animals with PIV3 inoculation (P value were 0.024, 0.03, 0.011 and 0.008) and peaked in PID 42. There was no significant difference (P=0.18) between 3.90 (1.75) CCnt of the asthma animals and the normal control. Animals of PID 6 showed significantly greater AHR to 2 highest concentrations of methacholine than the normal controls. BAL total cell counts of both the PIV3-inoculated and the asthma animals were significantly higher than those of the normal control, with the number of lymphocytes increased significantly within first 2 weeks after PIV3 inoculation. The lung pathology of PIV3-inoculated animals showed airway inflammation without pneumonia in acute infectious phase.

CONCLUSIONS

An animal model of cough induced by PIV3 was created. The CRS of infected guinea pigs increased significantly in both acute and subacute phases of cough. Elevation of CRS may be characteristic of cough caused by virus.

Severe pneumonia caused by combined infection with Pneumocystis jiroveci, parainfluenza virus type 3, cytomegalovirus, and Aspergillus fumigatus in a patient with Stevens-Johnson syndrome/toxic epidermal necrolysis

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are severe adverse cutaneous reactions to drugs. We report here the first case of severe pneumonia caused by an unusual combined infection with Pneumocystis carinii (jiroveci), parainfluenza virus type 3, cytomegalovirus and Aspergillus fumigatus in a 63-year-old female patient with allopurinol-induced SJS/TEN overlap syndrome. Following treatment with high-dose systemic corticosteroids and intravenous immunoglobulin for SJS/TEN, her mucocutaneous lesions improved and she was due to be discharged. However, 15 days after cessation of corticosteroids, she developed pneumonia. Broncho-alveolar lavage revealed that the cause of infection was Pneumocystis carinii (jiroveci), parainfluenza virus type 3, cytomegalovirus and Aspergillus. These findings indicate that patients with SJS/TEN, particularly those treated with systemic corticosteroids, may be susceptible to infection with combinations of pathological agents resulting from damage to the bronchial epithelia.

Drying-Induced Variations in Physico-Chemical Properties of Amorphous Pharmaceuticals and Their Impact on Stability II: Stability of a Vaccine

OBJECTIVES

To investigate the impact of drying method on the storage stability of dried vaccine formulations.

MATERIALS AND METHODS

A sucrose-based formulation of a live attenuated virus vaccine of a parainfluenza strain, with and without surfactant, was dried from by different methods; freeze drying, spray drying and foam drying. Dried powders were characterized by differential scanning calorimetry, specific surface area (SSA) analysis and by electron spectroscopy for chemical analysis (ESCA) to evaluate vaccine surface coverage in the dried formulations. Dried formulations were subjected to storage stability studies at 4, 25 and 37 degrees C. The vaccine was assayed initially and at different time points to measure virus-cell infectivity, and the degradation rate constant of the vaccine in different dried preparations was determined.

RESULTS

SSA was highest with the spray dried preparation without surfactant (approximately 2.8 m(2)/g) and lowest in the foam dried preparations (with or without surfactant) (approximately 0.1 m(2)/g). Vaccine surface coverage was estimated based on ESCA measurements of nitrogen content. It was predicted to be highest in the spray dried preparation without surfactant and lowest in the foam with surfactant. Stability studies conducted at 25 degrees C and 37 degrees C showed that the vaccine was most stable in the foam dried preparation with surfactant and least stable in spray dried preparations without surfactant and in all freeze dried preparations regardless of the presence of surfactant. Addition of surfactant did lower the SSA and vaccine surface coverage in freeze dried preparations but still did not improve storage stability.

CONCLUSIONS

In drying methods that did not involve a freezing step, good storage stability of Medi 534 vaccine in the dried form was found with low SSA and low vaccine surface accumulation, both of which integrate into low fraction of vaccine at the surface. Ice appears to be a major destabilizing influence.

Transmissibility, infectivity and immunogenicity of a live human parainfluenza type 3 virus vaccine (HPIV3cp45) among susceptible infants and toddlers

BACKGROUND

This study examined the transmissibility between young children of an intranasally administered live attenuated human parainfluenza virus type 3 (HPIV3)-cp45 vaccine candidate.

METHODS

Eighty subjects were enrolled in playgroups among whom there was at least one infected vaccinee in close contact with a seronegative placebo recipient over 21 days without a confounding infection with wtHPIV3. Following vaccination viral cultures were obtained on nine occasions to detect shedding and transmission of HPIV3cp45. Serum antibody titers were measured before and 7 weeks after vaccination.

RESULTS

No child fulfilled the criteria for transmission of HPIV3cp45 giving a risk of transmission of 0.04 (95% CI 0.01-0.19), hence establishing that HPIV3cp45 is less infectious than wtHPIV3 and risk of transmission is not a limitation to further clinical development of this vaccine candidate.

[Parainfluenza virus infections in pediatric patients with acute respiratory infections in Beijing during 2001 - 2003]

OBJECTIVE

To understand the relationship of parainfluenza virus (PIV) and acute respiratory infections in infants and young children in Beijing, occurred in recent years.

METHODS

3141 throat swab/nasopharyngeal aspirate specimens were collected from infants and young children with acute respiratory tract infections in Beijing from Jan 2001 to Dec 2003. All of these 3141 specimens were inoculated into MDCK cells for influenza virus and PIV isolation, since PIV had been isolated in MDCK cells in this laboratory from preliminary studies. Out of 3141 specimens, 702 were inoculated into MDCK as well as Vero cells to compare the sensitivity on virus isolation of these cell lines by micro plate method. Growth of PIV in cell culture were identified by haemoagglutination test and indirect immunofluorescent assay.

RESULTS

The PIV positive cases in Vero cells were also positive in MDCK cells, indicating that the sensitivity for PIV isolation in MDCK was equal to Vero cells. Out of these 3141 specimens, 94 (3.0%) were PIV positive, including 35 (35/1191, 2.9%) of PIV1, 11 (11/1191, 0.9%) of PIV3 in upper respiratory tract infections; 15 (15/1634, 0.9%) of PIV1, 24 (24/1634, 1.5%) of PIV3 in lower respiratory tract infections; 3 (3/207, 1.4%) of PIV in asthma; 1 (1/38) of PIV in patients with fever; 5 (5/71) of PIV in others. Data indicated that among upper respiratory tract infections caused by PIV, PIV1 was more commonly seen than PIV3.

CONCLUSION

MDCK cells could be used for PIV isolation from clinical samples while PIV was one of the important pathogenic viruses causing acute respiratory tract infections in infants and young children in Beijing for the recente years.

Human parainfluenza virus 3 neuraminidase activity contributes to dendritic cell maturation

Mechanisms of dendritic cells (DCs) immunomodulation by parainfluenza viruses have not been characterized. We analyzed whether the human parainfluenza 3 (HPF3) virus hemagglutinin-neuraminidase glycoprotein (HN) might influence DC maturation. HN possesses a receptor binding function and a neuraminidase or desialidating activity. To assess whether the neuraminidase activity of HN affects DC maturation, human myeloid DCs were exposed to either live or UV-inactivated HPF3 viruses containing wild type or a mutated form of HN with decreased neuraminidase activity. Exposure of human DCs to either UV-inactivated or live virus induced up-regulation of CD83 and CD86 surface markers, morphological changes, and a cytokine expression pattern consistent with maturation. However, the level of maturation was found to be lower in DCs infected with the neuraminidase deficient variant as compared to the wild type. These results suggest that during the course of viral infection, HN's neuraminidase activity may play an important role contributing to maturation and activation of DCs.

Entry of parainfluenza virus into cells as a target for interrupting childhood respiratory disease

Human parainfluenza viruses cause several serious respiratory diseases in children for which there is no effective prevention or therapy. Parainfluenza viruses initiate infection by binding to cell surface receptors and then, via coordinated action of the 2 viral surface glycoproteins, fuse directly with the cell membrane to release the viral replication machinery into the host cell's cytoplasm. During this process, the receptor-binding molecule must trigger the viral fusion protein to mediate fusion and entry of the virus into a cell. This review explores the binding and entry into cells of parainfluenza virus type 3, focusing on how the receptor-binding molecule triggers the fusion process. There are several steps during the process of binding, triggering, and fusion that are now understood at the molecular level, and each of these steps represents potential targets for interrupting infection.

Inhibition of STAT 1 phosphorylation by human parainfluenza virus type 3 C protein

The P mRNA of the viruses belonging to the subfamily Paramyxovirinae possesses a unique property of giving rise to several accessory proteins by a process that involves the utilization of overlapping open reading frames (the C proteins) and by an "RNA-editing" mechanism (the V proteins). Although these proteins are considered accessory, numerous studies have highlighted the importance of these proteins in virus transcription and interferon signaling, including our previous observation on the role of human parainfluenza virus type 3 (HPIV 3) C protein in the transcription of viral genome (Malur et al., Virus Res. 99:199-204, 2004). In this report, we have addressed its role in interferon signaling by generating a stable cell line, L-C6, by using the lentiviral expression system which expresses HPIV 3 C protein. The L-C6 cells were efficient in abrogating both alpha and gamma interferon-induced antiviral states and demonstrated a drastic reduction in the formation of gamma-activated factor complexes in the cell extracts. Western blot analysis subsequently revealed a defect in the phosphorylation of STAT 1 in these cells. Taken together, our results indicate that HPIV 3 C protein is capable of counteracting the interferon signaling pathway by specifically inhibiting the activation of STAT 1.

Contamination of a specific-pathogen-free rat breeding colony with Human parainfluenzavirus type 3

Routine antibody surveillance for Sendai virus in a breeding colony suggested viral invasion into laboratory rats. A more specific haemagglutination-inhibition test implied that the agent was related closely to Human parainfluenza virus type 3 (hPIV3), rather than Sendai virus. To isolate this virus, Vero cells were inoculated with lung homogenates of 30 young animals from the colony. One of the cultures became positive at the second passage by RT-PCR directed to the hPIV3 NP and L genes. Cytopathic effect with cell fusion was observed at the third passage. The HN gene of this virus (KK24) had >93 % similarity to those of other hPIV3 isolates, suggesting a human origin of KK24. Experimental intranasal inoculation of KK24 into SD rats showed virus replication in the lungs at 3–5 days post-infection (p.i.). Pathological examination of the lungs at day 5 p.i. indicated a moderate detachment, degradation and apoptosis of bronchial epitheliocytes with peribronchial mononuclear infiltrations. At day 7 p.i., these changes became less prominent, and no lesions were apparent at day 10 p.i. or later. The infected rats seroconverted at day 7 p.i. On the contrary, none of the 30 experimentally infected ICR mice showed any pathological lesions in their lungs, despite seroconversion at 7 days p.i. These results suggest that hPIV3 can invade rat colonies and has a moderate and transient pathogenicity in rats. This is the first report of non-experimental hPIV3 infection in laboratory rats, unexpectedly detected by antibody screening for Sendai virus.

Conserved glycine residues in the fusion peptide of the paramyxovirus fusion protein regulate activation of the native state

Hydrophobic fusion peptides (FPs) are the most highly conserved regions of class I viral fusion-mediating glycoproteins (vFGPs). FPs often contain conserved glycine residues thought to be critical for forming structures that destabilize target membranes. Unexpectedly, a mutation of glycine residues in the FP of the fusion (F) protein from the paramyxovirus simian parainfluenza virus 5 (SV5) resulted in mutant F proteins with hyperactive fusion phenotypes (C. M. Horvath and R. A. Lamb, J. Virol. 66:2443-2455, 1992). Here, we constructed G3A and G7A mutations into the F proteins of SV5 (W3A and WR isolates), Newcastle disease virus (NDV), and human parainfluenza virus type 3 (HPIV3). All of the mutant F proteins, except NDV G7A, caused increased cell-cell fusion despite having slight to moderate reductions in cell surface expression compared to those of wild-type F proteins. The G3A and G7A mutations cause SV5 WR F, but not NDV F or HPIV3 F, to be triggered to cause fusion in the absence of coexpression of its homotypic receptor-binding protein hemagglutinin-neuraminidase (HN), suggesting that NDV and HPIV3 F have stricter requirements for homotypic HN for fusion activation. Dye transfer assays show that the G3A and G7A mutations decrease the energy required to activate F at a step in the fusion cascade preceding prehairpin intermediate formation and hemifusion. Conserved glycine residues in the FP of paramyxovirus F appear to have a primary role in regulating the activation of the metastable native form of F. Glycine residues in the FPs of other class I vFGPs may also regulate fusion activation.

Adenovirus-mediated gene therapy enhances parainfluenza virus 3 infection in neonatal lambs

Parainfluenza viruses are a common cause of seasonal respiratory disease, but in high-risk individuals (e.g., young children) these viruses can cause severe clinical manifestations that require hospitalization. Beta-defensins are a subclass of antimicrobial peptides with antiviral activity. Use of adenovirus-mediated beta-defensin gene expression has been proposed as therapy for chronic bacterial infections commonly seen in cystic fibrosis patients; however, its use during parainfluenza virus 3 (PIV3) infection has not been evaluated. The hypothesis in this experiment was that adenovirus expression of human beta-defensin 6 (HBD6) would diminish concurrent PIV3 infection in neonatal lambs. The group infected with adenovirus HBD6 and PIV3 had increased levels of pulmonary neutrophil recruitment compared to those for the group infected with PIV3 or PIV3 and adenovirus, with an increased respiration rate and body temperature late in the course of the PIV3-adenovirus HBD6 infection. Interestingly, the adenovirus-treated groups had higher levels of immunohistochemical staining for PIV3 and syncytial cell formation than the group infected with PIV3, suggesting that treatment with the adenovirus vector, regardless of whether it was carrying a target gene, exacerbated the PIV3 infection. The levels of expression of mRNA for antimicrobial surfactant proteins A and D and sheep beta-defensin 1 were increased by PIV3 and adenovirus treatment, and the increased levels of expression roughly corresponded to the degree of inflammation. While pulmonary administration of a high-dose adenovirus vector has been associated with undesirable inflammation, this is the first study to show that it can exacerbate concurrent viral infection, a concern that needs to be addressed for future studies of adenovirus in the lung. Additionally, this study showed that adenovirus-mediated HBD6 expression increases neutrophil recruitment, a recently described attribute of beta-defensins, with mild accentuation of PIV3 activity and inflammation.

Bovine parainfluenza virus type 3 (PIV3) expressing the respiratory syncytial virus (RSV) attachment and fusion proteins protects hamsters from challenge with human PIV3 and RSV

Parainfluenza virus type 3 (PIV3) and respiratory syncytial virus (RSV) are the main causes of ubiquitous acute respiratory diseases of infancy and early childhood, causing 20-25 % of pneumonia and 45-50 % of bronchiolitis in hospitalized children. The primary goal of this study was to create an effective and safe RSV vaccine based on utilizing attenuated bovine PIV3 (bPIV3) as a virus vector backbone. bPIV3 had been evaluated in human clinical trials and was shown to be attenuated and immunogenic in children as young as 2 months of age. The ability of bPIV3 to function as a virus vaccine vector was explored further by introducing the RSV attachment (G) and fusion (F) genes into the bPIV3 RNA genome. The resulting virus, bPIV3/RSV(I), contained an insert of 2900 nt, comprising two translationally competent transcription units. Despite this increase in genetic material, the virus replicated to high titres in Vero cells. This recombinant virus expressed the RSV G and F proteins sufficiently to evoke a protective immune response in hamsters upon challenge with RSV or human PIV3 and to elicit RSV neutralizing and PIV3 haemagglutinin inhibition serum antibodies. In effect, a bivalent vaccine was produced that could protect vaccinees from RSV as well as PIV3. Such a vaccine would vastly reduce the respiratory disease burden, the associated hospitalization costs and, most importantly, decrease morbidity and mortality of infants, immunocompromised individuals and the elderly.

Triggering of human parainfluenza virus 3 fusion protein (F) by the hemagglutinin-neuraminidase (HN) protein: an HN mutation diminishes the rate of F activation and fusion

For human parainfluenza virus type 3 and many other paramyxoviruses, membrane fusion mediated by the fusion protein (F) has a stringent requirement for the presence of the homotypic hemagglutinin-neuraminidase protein (HN). With the goal of gaining further insight into the role of HN in the fusion process, we developed a simple method for quantitative comparison of the ability of wild-type and variant HNs to activate F. In this method, HN/F-coexpressing cells with red blood cells (RBC) bound to them at 4 degrees C are transferred to 22 degrees C, and at different times after transfer 4-guanidino-neu5Ac2en (4-GU-DANA) is added; this inhibitor of the HN-receptor interaction then releases all reversibly bound RBC but not those in which F insertion in the target membrane or fusion has occurred. Thus, the amount of irreversibly bound (nonreleased) RBC provides a measure of F activation, and the use of fluorescently labeled RBC permits microscopic assessment of the extent to which F insertion has progressed to fusion. We studied two neuraminidase-deficient HN variants, C28a, which has two mutations, P111S and D216N, and C28, which possesses the D216N mutation only. C28a but not C28 exhibits a slow fusion phenotype, although determination of the HNs' receptor-binding avidity (with our sensitive method, employing RBC with different degrees of receptor depletion) showed that the receptor-binding avidity of C28a or C28 HN was not lower than that of the wild type. The F activation assay, however, revealed fusion-triggering defects in C28a HN. After 10 and also 20 min at 22 degrees C, irreversible RBC binding was significantly less for cells coexpressing wild-type F with C28a HN than for cells coexpressing wild-type F with wild-type HN. In addition, F insertion progressed to fusion more slowly in the case of C28a HN-expressing cells than of wild-type HN-expressing cells. Identical defects were found for P111S HN, whereas for C28 HN, representing the 216 mutation of C28a, F activation and fusion were as rapid as for wild-type HN. The diminished fusion promotion capacity of C28a HN is therefore attributable to P111S, a mutation in the stalk region of the molecule that causes no decrease in receptor-binding avidity. C28a HN is the first parainfluenza virus variant found so far to be specifically defective in HN's F-triggering and fusion promotion functions and may contribute to our understanding of transmission of the activating signal from HN to F.

Characterization of a novel parainfluenza virus, caviid parainfluenza virus 3, from laboratory guinea pigs (Cavia porcellus)

A novel Respirovirus was isolated from nasopharyngeal swab specimens from clinically normal laboratory guinea pigs, and was characterized and named caviid parainfluenza virus 3 (CavPIV-3). The CavPIV-3 is enveloped, is 100 to 300 nm in diameter, and has a characteristic 15-nm-diameter chevron-shaped virus ribonucleocapsid protein. Sequence analysis of the fusion glycoprotein of CavPIV-3 revealed it to be 94% identical to human and guinea pig parainfluenza 3 (PIV-3) viruses and 80% identical to bovine PIV-3. To determine whether CavPIV-3 causes clinical disease in laboratory guinea pigs and to compare the serologic response of guinea pigs to CavPIV-3 and to other paramyxoviruses, an infection study was performed, in which groups of guinea pigs were inoculated with CavPIV-3, Sendai virus, simian virus 5 (SV-5), murine pneumonia virus (PVM), or bovine PIV-3 virus. During the course of the study, guinea pigs were maintained in an infectious disease suite, housed in Micro-Isolator cages, and were only manipulated under a laminar flow hood. Clinical signs of disease were not observed in any of the paramyxovirus-inoculated guinea pigs during the eight-week course of the study, and histologic signs of disease were not evident at necropsy eight weeks after inoculation. Guinea pigs inoculated with CavPIV-3, Sendai virus, PVM, and bovine PIV-3 developed robust homologous or heterologous serologic responses. In contrast, guinea pigs inoculated with SV-5 developed modest or equivocal serologic responses, as assessed by use of an enzyme-linked immunosorbent assay. Further, use of the SV-5 enzyme-linked immunosorbent assay resulted in the highest degree of non-specific reactivity among all of the paramyxovirus assays. In summary, CavPIV-3 is a novel guinea pig Respirovirus that subclinically infects laboratory guinea pigs, resulting in a robust serologic response, but no observed clinical or histologic disease. The CavPIV-3 fusion glycoprotein gene sequence is available from GenBank as accession No. AF394241, and the CavPIV-3 virus is available from the American Type Culture Collection as accession No. DR-1547.

Substance P receptor expression on lymphocytes is associated with the immune response to respiratory syncytial virus infection

The kinetics and magnitude of SP receptor expression was determined for bronchoalveolar leukocyte cell subsets from BALB/c mice in the primary immune response to respiratory syncytial virus (RSV) and human parainfluenza virus-3 (PIV3) infection, and in the secondary immune response to RSV and PIV3 challenge. In both the primary and secondary responses to infection, expression of substance P (SP) receptors was markedly increased by infection, especially for T lymphocytes, compared to B220+, CD11b+ and CD14+ cells. CD4+ T lymphocytes predominantly expressed SP receptors in the secondary response. These results suggest that SP receptor expression may be important in the development of primary and secondary immune responses to respiratory virus infections.

A single amino acid alteration in the human parainfluenza virus type 3 hemagglutinin-neuraminidase glycoprotein confers resistance to the inhibitory effects of zanamivir on receptor binding and neuraminidase activity

Entry and fusion of human parainfluenza virus type 3 (HPF3) requires interaction of the viral hemagglutinin-neuraminidase (HN) glycoprotein with its sialic acid receptor. 4-Guanidino-2,4-dideoxy-2,3-dehydro-N-acetylneuraminic acid (4-GU-DANA; zanamivir), a sialic acid transition-state analog designed to fit the influenza virus neuraminidase catalytic site, possesses antiviral activity at nanomolar concentrations in vitro. We have shown previously that 4-GU-DANA also inhibits both HN-mediated binding of HPF3 to host cell receptors and HN's neuraminidase activity. In the present study, a 4-GU-DANA-resistant HPF3 virus variant (ZM1) was generated by serial passage in the presence of 4-GU-DANA. ZM1 exhibited a markedly fusogenic plaque morphology and harbored two HN gene mutations resulting in two amino acid alterations, T193I and I567V. Another HPF3 variant studied in parallel, C-0, shared an alteration at T193 and exhibited similar plaque morphology but was not resistant to 4-GU-DANA. Neuraminidase assays revealed a 15-fold reduction in 4-GU-DANA sensitivity for ZM1 relative to the wild type (WT) and C-0. The ability of ZM1 to bind sialic acid receptors was inhibited 10-fold less than for both WT and C-0 in the presence of 1 mM 4-GU-DANA. ZM1 also retained infectivity at 15-fold-higher concentrations of 4-GU-DANA than WT and C-0. A single amino acid alteration at HN residue 567 confers these 4-GU-DANA-resistant properties. An understanding of ZM1 and other escape variants provides insight into the effects of this small molecule on HN function as well as the role of the HN glycoprotein in HPF3 pathogenesis.

Polarity of human parainfluenza virus type 3 infection in polarized human lung epithelial A549 cells: role of microfilament and microtubule

Human parainfluenza virus type 3 (HPIV-3) is an airborne pathogen that infects the epithelial cells of the respiratory tract. In the present study we investigated the interaction of HPIV-3 with the type II alveolar human lung polarized epithelial A549 cells. Although HPIV-3 entry and budding were bidirectional from both the apical and the basolateral domains, HPIV-3 exhibited preferential entry and release from the apical pole. While disruption of the cellular actin microfilament and microtubule by cytochalasin D and nocodazole, respectively, had no effect on virus entry, disruption of the microtubule but not the microfilament inhibited HPIV-3 release.

Mutations in the C, D, and V open reading frames of human parainfluenza virus type 3 attenuate replication in rodents and primates

Human parainfluenza virus type 3 (HPIV3) is a single-stranded negative-sense RNA virus belonging to the Respirovirus genus of the Paramyxoviridae family in the order Mononegavirales. The P gene encodes at least four proteins, including the C protein, which is expressed from an open reading frame (ORF) that overlaps the P ORF, and the D protein, which is encoded when the P ORF is fused to the D ORF by transcriptional editing. The P mRNA also contains a third ORF for the V protein, although it is unclear how or whether this ORF is accessed. We have used recombinant DNA technology to recover five mutant viruses that either interrupt or alter the C, D, and V ORFs. In one mutant virus, rC-KO, expression of the C protein was abrogated by changing the start codon from methionine to threonine and introducing two stop codons at amino acid positions 7 and 26 of the C ORF. In a second mutant virus, rF164S, a point mutation was introduced into the C ORF changing amino acid position 164 from phenylalanine (F) to serine (S), which corresponds to the F170S mutation described in the C protein of Sendai virus (Itoh et al., J. Gen. Virol. 78, 3207-3215). rC-KO was significantly attenuated in vitro and in vivo (rodents and primates), whereas rF164S was attenuated only in vivo. Interestingly, the rF164S mutant was more attenuated in the upper than in the lower respiratory tract of hamsters and monkeys. This pattern is the converse of that seen with temperature-sensitive attenuating mutations, and thus inclusion of this novel mutation in a recombinant live-attenuated vaccine candidate might prove useful in reducing residual virulence in the upper respiratory tract. Both rC-KO and rF164S conferred protection against challenge with wild-type HPIV3. In three other viruses, the D and V ORFs were interrupted singly or in combination. Although interruption of the D and V ORFs individually did not affect virus replication in vitro or in vivo, interruption of both together attenuated replication in vivo. These results indicate that the C, D, and V proteins of HPIV3 each has a role in virus replication in vitro, in vivo, or both, and define mutations that might be useful for the development of a vaccine against HPIV3.

Recovery of infectious human parainfluenza virus type 3 from cDNA

Infectious HPIV3 was produced by the intracellular coexpression of four plasmid-borne cDNAs. These separately encoded a complete HPIV3 genome (negative-sense), the HPIV3 nucleocapsid protein N, the phosphoprotein P, and the polymerase protein L. The cDNA-encoded HPIV3 genome differed from the JS wildtype (wt) strain of HPIV3 used in its construction by seven point mutations: four of these are silent mutations in the HN or L gene coding regions that serve as markers of a cDNA-derived virus, two were introduced to create an amino acid substitution that ablates an epitope recognized by the HN-specific monoclonal neutralizing antibody 423/6, and the remaining point mutation results in an incidental amino acid substitution in the HN protein at amino acid position 263. The four plasmids were transfected into HEp-2 cell monolayers and their expression was driven by T7 RNA polymerase supplied by a vaccinia virus recombinant. The titer of virus present in the harvested transfection supernatant was low (<5 PFU/ml), and the recovered recombinant virus (rJS) retained each of the seven mutations present in the cDNA from which it was derived. Despite the introduced and incidental mutations, rJS retained the wt phenotypes as regards replication at elevated temperature in vitro and efficient replication in the upper and lower respiratory tract of hamsters. rJS was also recovered from a cDNA encoding a complete antigenome (positive-sense) with slightly greater efficiency than from the negative-sense construct. The ability to generate infectious HPIV3 from cDNA should greatly enhance our ability to develop new live-attenuated parainfluenza virus vaccines, including chimeric PIV1 and PIV2 vaccines, and to understand the genetic basis of attenuation of PIV3 candidate vaccines.

Role of sensory neuropeptides in PIV-3-infection-induced airway hyperresponsiveness in guinea pigs

Viral respiratory tract infections are known to induce transient airway hyper-responsiveness. The role of the nonadrenergic noncholinergic neuropeptide system on virus-induced airway hyperresponsiveness was studied in the guinea pig. Ten guinea pigs were inoculated with parainfluenza 3 virus (PIV-3.2 x 10(6) PFU) by nasal route. 16 animals served as untreated controls. Viral infection was proven by histological changes and by demonstration of viral antigen using immunohistochemical techniques. Four days after inoculation, airway responsiveness to inhaled acetylcholine (ACH) aerosol was measured in anesthetized and tracheotomized guinea pigs. The ACH concentration which produced an increase of 100% in pulmonary resistance (PC100 RI) and in dynamic elastance (PC100 Edyn) was calculated from a 5-step ACH dose-response curve (0.125, 0.25, 0.5, 1.0 and 2.0% ACH). Two further groups of 8 PIV-3-infected guinea pigs and 8 noninfected control animals were pretreated with capsaicin in increasing doses (50, 100, 125 and 150 mg/kg) on 4 consecutive days starting 6 days before virus inoculation. Measurements of airway responsiveness to ACH were performed 4 days after virus inoculation. Another 5 uninfected control animals were pretreated only with the solvent for capsaicin and inoculated with virus-free cell supermatant. PIV-3 infection increased airway responsiveness to ACH compared to noninfected controls [PC100 RI 0.81 vs. > 2.0% ACH (median). p < 0.002 PC100 Edyn 0.52 vs. 1.07% ACH (median), p < 0.01]. In capsaicin-pretreated PIV-3-infected animals, airway hyperresponsiveness was completely prevented compared to the virus-infected group without capsaicin pretreatment (PC100 RI > 2.0 vs. 0.81% ACH, p < 0.01; PC100 Edyn 1.42 vs. 0.52% ACH p < 0.01). As neuropeptide depletion with capsaicin completely prevented the increase in airway constrictory response to ACH following virus infection, we conclude that neuropeptides are effectively involved in PIV-3-induced airway hyperresponsiveness in the guinea pig.

Bovine parainfluenza-3 virus selectively depletes a calcium-independent, phospholipid-dependent protein kinase C and inhibits superoxide anion generation in bovine alveolar macrophages

Bovine parainfluenza-3 (PI-3) virus inhibits oxygen-dependent bacterial killing by phagocytes, a key pulmonary defense, thus predisposing the host to intrapulmonary bacterial superinfection. PI-3 virus inhibited opsonized zymosan or PMA-activated superoxide anion (O2-) generation in bovine alveolar macrophages. The respiratory virus influenza also inhibits O2- generation by phagocytes, however, the mechanisms(s) of viral inhibition differs from PI-3. PI-3 did not trigger O2- generation before inhibition, whereas influenza triggered O2- generation before desensitization of ligand-initiated respiratory burst. PI-3 modified the twin signals of calcium and protein kinase C in alveolar macrophages. PI-3 infection increased macrophage membrane permeability to extracellular calcium, but did not inhibit calcium mobilization triggered by opsonized zymosan. These effects further distinguish bovine PI-3 from human influenza, which triggers mobilization of cell-associated calcium and inhibits calcium mobilization activated by physiologic ligands. Macrophages possessed two classes of PKC activity, a calcium/phosphatidylserine/diglyceride (Ca/PS/DG))-dependent activity and a Ca-independent, PS/DG-dependent histone IIIS phosphorylating activity. PI-3 infection selectively depleted the Ca-independent, PS/DG-dependent kinase activity but not the classical Ca/PS/DG-dependent activity. Inhibition of Ca-independent, PS/DG-dependent kinase activity and inhibition of O2- generation by PI-3 occurred at a similar viral dose and time frame, suggesting a role for this kinase in activating the respiratory burst. Inhibition of the oxygen-dependent bactericidal function of alveolar macrophages and disturbances in signal transduction may contribute to the immunosuppression and bacterial superinfection accompanying viral respiratory disease.

Effects of parainfluenza type 3 virus on guinea pig pulmonary alveolar macrophage functions in vitro

The influence of parainfluenza type 3 (PI-3) virus on the release of inflammatory mediators by guinea pig pulmonary alveolar macrophages (PAMs) was investigated in vitro. Direct application of PI-3 virus dose-dependently stimulated the generation of chemiluminescence by PAMs and induced aggregation of PAMs. No significant effects of PI-3 virus on the release of linoleic acid metabolites by PAMs were detected. However, an increased release of the arachidonic acid metabolite thromboxane B2 (TxB2) was observed when PAMs were stimulated with PI-3 virus. PAMs were also cultured for 2 h or 18 h in the presence of PI-3 virus or control medium. The production of reactive oxygen species and the release of fatty acid metabolites by these PAMs were determined upon stimulation with opsonized zymosan particles or phorbol myristate acetate. The amounts of hydrogen peroxide and superoxide produced did not differ between virus- and control medium-incubated PAMs. However, the PI-3 virus-treated PAMs generated twice as much chemiluminescence when compared to PAMs incubated with control medium. The 2-h incubation period with PI-3 virus also resulted in a decreased release of TxB2 from the PAMs upon zymosan stimulation. The changes in the production of reactive oxygen species and the release of TxB2 by PAMs could account for damage to the airways and bronchial hyperresponsiveness often seen after viral infection.

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.

Fusion properties of cells infected with human parainfluenza virus type 3: receptor requirements for viral spread and virus-mediated membrane fusion

Cells can be persistently infected with human parainfluenza virus type 3 (HPF3) by using a high multiplicity of infection (MOI) (> or = 5 PFU per cell). The persistently infected cells exhibit no cytopathic effects and do not fuse with each other, yet they readily fuse with uninfected cells. We have previously shown that the failure of the persistently infected cells to fuse with each other is due to the lack of a receptor on these cells for the viral hemagglutinin-neuraminidase glycoprotein, and we have established that both fusion and hemagglutinin-neuraminidase proteins are needed for cell fusion mediated by HPF3. We then postulated that the generation of persistent infection and the failure of cells infected with HPF3 at high MOI to form syncytia are both due to the action of viral neuraminidase in the high-MOI inoculum. In this report, we describe experiments to test this hypothesis and further investigate the receptor requirements for HPF3 infection and cell fusion. A normally cytopathic low-MOI HPF3 infection can be converted into a noncytopathic infection by the addition of exogenous neuraminidase, either in the form of a purified enzyme or as UV-inactivated HPF3 virions. Evidence is presented that the receptor requirements for an HPF3 virus particle to infect a cell are different from those for fusion between cells. By treating infected cells in culture with various doses of neuraminidase, we demonstrate that virus spreads from cell to cell in the complete absence of cell-cell fusion. We compare the outcome of HPF3 infection in the presence of excess neuraminidase with that of another paramyxovirus (simian virus 5) and provide evidence that these two viruses differ in their receptor requirements for mediating fusion.

Cold-passaged human parainfluenza type 3 viruses contain ts and non-ts mutations leading to attenuation in rhesus monkeys

Cold-passaged (CP) mutants derived from the JS strain of wild type wt parainfluenza type 3 virus (PIV3) are being evaluated as candidate live virus vaccines. The wt virus was serially passaged 45 times at low temperature and mutant clones with the cold-adapted (CA), temperature-sensitive (ts), and attenuation (ATT) phenotypes were selected following passage levels 12, 18 and 45 (cp12, cp18, and cp45). The cp45 virus was more ts than the cp12 or cp18 mutants, although all 3 mutant viruses were clearly attenuated in rhesus monkeys compared to wild type virus. The mean peak titers of the cp12 and cp18 viruses administered by the intratracheal route were at least 6000-fold lower than JSwt in both the upper and lower respiratory tracts. The cp45 virus was not recovered from monkeys administered virus by the i.t. route alone; however, when the cp45 virus was administered by the intranasal route, it replicated in the upper respiratory tract to a level comparable to that of the cp12 and cp18 viruses, but continued to be markedly restricted in the lower respiratory tract. These data indicate that the cp12 and cp18 viruses contain predominantly non-ts attenuating mutations whereas the cp45 mutant has both non-ts and ts attenuating mutations. Each of the CP mutants induced a high level of resistance to wild type virus challenge. Also, the ATT phenotype of the cp12 and cp18 viruses as measured in rhesus monkeys was stable after replication in chimpanzees or humans, respectively, although the ts phenotype was not. Based on its greater level of temperature sensitivity in vitro and its greater degree of attenuation in rhesus monkeys, the cp45 virus appears to be the most promising vaccine candidate for humans.

The fusion and hemagglutinin-neuraminidase glycoproteins of human parainfluenza virus 3 are both required for fusion

Recombinant vaccinia viruses, VF and VHN, expressing the fusion (F) and hemagglutinin-neuraminidase (HN) glycoproteins of human parainfluenza virus 3 (HPIV3) were constructed. Infection of HeLa T4 cells with VF and VHN led to the synthesis of glycoproteins, with the correct apparent molecular weights, that were recognized by monoclonal antibodies specific for HPIV3F and HN. The HN glycoprotein was present on the surface of cells infected with VHN and these cells demonstrated both hemadsorbing and neuraminidase activities. The F glycoprotein was present in cleaved and uncleaved forms and was also expressed on the surface of VF-infected cells. Fusion activity, however, as evidenced by syncytium formation and lysis of human erythrocytes, could only be demonstrated when HeLa T4 cells were coinfected with VF and VHN. Fusion events that are mediated by HPIV3, therefore, require both the F and HN glycoproteins.

Evaluation of bovine, cold-adapted human, and wild-type human parainfluenza type 3 viruses in adult volunteers and in chimpanzees

In an attempt to evaluate the level of attenuation of live parainfluenza type 3 virus (PIV3) vaccine candidates, we compared the responses of partially immune adult volunteers inoculated intranasally with 10(6) to 10(7) 50% tissue culture infective dose (TCID50) of bovine PIV3 (n = 18) or cold-adapted (ca) PIV3 (n = 37) with those of 28 adults administered 10(6) to 10(7) TCID50 of wild-type PIV3. The candidate vaccine viruses and the wild-type virus were avirulent and poorly infectious for these adults even though all of them had a low level of nasal antibodies to PIV3. To determine whether the ca PIV3 was attenuated, we then administered 10(4) TCID50 of ca PIV3 (cold-passage 12) or wild-type PIV3 intranasally and intratracheally to two fully susceptible chimpanzees, respectively, and challenged the four primates with wild-type virus 1 month later. Compared with wild-type virus, which caused upper respiratory tract illness, the ca PIV3 was highly attenuated and manifested a 500-fold reduction in virus replication in both the upper and lower respiratory tracts of the two immunized animals. Despite restriction of virus replication, infection with ca PIV3 conferred a high level of protective immunity against challenge with wild-type virus. The ca PIV3 which had been passaged 12 times at 20 degrees C did not retain its ts phenotype. These findings indicate that ca PIV3 may be a promising vaccine candidate for human beings if a passage level can be identified that is genetically stable, satisfactorily attenuated, and immunogenic.

Studies of natural population variability of parainfluenza viruses during their epidemic circulation

The population of circulating serotype 3 parainfluenza virus strains isolated in different years proved to be sufficiently polymorphic concerning its antigenic and biological features as well as their virulence for newborn hamsters. The highly virulent strain population appeared to have an antigenic pattern different from that of the prototype strain. The epidemic caused by it in groups of school and preschool children was more intensive as compared to that induced by avirulent strains population.

Infection of cultured human tracheal epithelial cells by human parainfluenza virus types 2 and 3

Despite growing information of the effects of human respiratory virus infection on airway physiology, little information is available on the mechanisms of pathology and pathophysiology in these infections. The human respiratory pathogens, parainfluenza virus types 2 and 3 (hPIV2, hPIV3, respectively), clinically cause laryngotracheobronchitis (infection of the large proximal airways). In order to examine the pathobiology of these viruses in airway cells of human origin, we exposed primary cultures of human tracheal epithelial cells. Primary cultures of human tracheal epithelial cells were readily infected by these agents: cells exposed to hPIV2 and hPIV3 expressed viral antigens (demonstrated by indirect immunofluorescence assay), produced infectious virus, and demonstrated cytopathic effects (including early syncytium formation). Peak viral titers of 2 x 10(7) plaque-forming units per milliliter were obtained, similar to titers from permissive CV-1 cells. Trypan blue staining and direct cell counts demonstrated no difference in the viability of the control and infected cells until the infected cells began to detach from the culture substrate. However, infected cells release significantly more LDH than control cells by 48 h following infection at a multiplicity of infection of 1 virus/target cell. This system provides a model for studying the effects of infection of the human tracheal epithelium by human respiratory viral pathogens without confounding interactions with other cell and tissue types.

Pathogenesis of human parainfluenza virus 3 infection in two species of cotton rats: Sigmodon hispidus develops bronchiolitis, while Sigmodon fulviventer develops interstitial pneumonia

Human parainfluenza virus 3 replicates well in the noses and lungs of two species of cotton rats, Sigmodon hispidus and Sigmodon fulviventer. Peak viral titers of nearly 10(6) PFU/g are reached 2 days after infection in both tissues, are maintained through day 5, and are equivalent in the two species. Infectious virus is eliminated by day 8 after infection. Both species produce a strong neutralizing antibody response with titers of 1:10,000 4 weeks after infection. Viral replication in the nasal epithelium results in only minor histological changes, and viral antigen is found only in the apical portion of epithelial cells. Infection of S. hispidus causes a bronchiolitis with a peribronchiolar lymphoid cell infiltration that reaches a peak 6 days after infection, and there is only a minor component of interstitial pneumonia. In contrast, infection of S. fulviventer causes an interstitial pneumonia, and this lesion reaches its maximal extent by 6 days after infection. There is minimal peribronchiolar lymphoid cell infiltration in infected S. fulviventer. Lung lesions in both species of cotton rats are largely healed 9 days after infection, and the lungs are indistinguishable from those of uninfected controls 16 days after infection. These species of cotton rats offer separate models for the two major pulmonary manifestations of human parainfluenza virus 3 infection. The models may be useful for basic studies of the pathogenesis of this infection and for initial evaluation of candidate vaccines.

Characterization of human parainfluenza virus type 3 persistent infection in cell culture

Three cell lines persistently infected with human parainfluenza virus type 3 were characterized on a molecular level in this study. All six structural protein genes were transcribed into monocistronic RNAs in the persistently infected cells. In both acutely and persistently infected cells, polycistronic transcripts were abundant, although the ratio of polycistronic to monocistronic transcripts was reduced in the persistently infected cells. Each of the persistently infected cell lines contained a distinct subgenomic RNA species. The subgenomic RNAs were present in purified nucleocapsid cores, indicating that they represent viral genome RNA, were far more abundant than full-length RNA, and were stably maintained through at least 36 cell passages. Nucleotide sequence analysis of the subgenomic RNAs from two of the persistently infected cell lines revealed that the 5' ends are identical to that of the standard genome. Hybridization experiments with oligonucleotide probes showed that both fragments retain sequences from the 5' end of the standard genome and contain approximately 1,200 nucleotides (cell line 1) and 1,500 nucleotides (cell line 2) of the polymerase gene sequence. The demonstration of several alterations in viral gene expression in persistently infected cells offers insight into the factors associated with persistence of parainfluenza virus 3.

Syncytium formation by recombinant vaccinia viruses carrying bovine parainfluenza 3 virus envelope protein genes

The highly syncytium-inducing M strain and the weakly syncytium-inducing SC strain of bovine parainfluenza 3 virus differ by a single amino acid substitution in each of the hemagglutinin-neuraminidase (HN) and membrane (M) proteins, while their fusion (F) proteins are identical (T. Shioda, S. Wakao, S. Suzu, and H. Shibuta, Virology 162:388-396, 1988). We constructed recombinant vaccinia viruses which express separately the M virus HN (Vac-MHN), SC virus HN (Vac-SCHN), M virus M (Vac-MM), SC virus M (Vac-SCM), and common F (Vac-F) proteins. CV-1 cells were infected with the recombinants, singly or in combination, and implanted onto indicator MDBK cells for syncytium formation. Combinations of Vac-MHN plus Vac-F and Vac-SCHN plus Vac-F induced extensive and weak syncytium formation, respectively. Vac-F alone did not induce syncytium formation, and both Vac-MM and Vac-SCM had no effect on syncytium formation. These findings indicated that the syncytium formation by bovine parainfluenza 3 virus requires both the F and HN proteins and that the extensive syncytium formation by the M virus is due to the M virus HN protein. MSC, another weakly syncytium-inducing virus variant, newly isolated from the M virus, was identical to the M virus in the primary structure of the HN and M proteins but differed from the M virus by a single amino acid residue in the F protein. The combination of the recombinant vaccinia virus expressing the MSC virus F protein and Vac-MHN resulted in weak syncytium formation.

[Comparative study of the hemolytic activity of ortho- and paramyxoviruses]

A comparative study of hemolytic activity of influenza type A, B, and C viruses, human parainfluenza type 3, and Sendai virus showed the pattern of pH-dependence and the nature of the curve to differ not only for different viruses under study but also for different erythrocyte species. Studies of virus-induced hemolysis of influenza C virus demonstrated that, depending on the erythrocyte species used, it had common properties both with influenza types A and B viruses and with paramyxoviruses.

[Mechanism of penetration of human type 3 parainfluenza virus into monkey kidney cells]

The mechanism of human parainfluenza type 3 virus penetration into monkey kidney cells was studied by morphological and biochemical methods. The results of electron microscopic studies permit a conclusion that the virus penetrates into the cells by the mechanism of receptor endocytosis. Analysis of subvirus structures in cytosole revealed two types of particles: nucleocapsids and structures of a larger size and lower buoyant density containing, in addition to NP protein, matrix (M) protein. It is presumed that nucleocapsid is released from the endocytic vacuole into the cytosole in association with M protein which is gradually eliminated from the nucleocapsid surface.

[Study of the multiplication in cell cultures of two strains of para-influenza virus type 3. III. Multiplication in BHK 21 cells]

Study was conducted on the multiplication of two strains (C243 and D) of parainfluenza virus type 3 in BHK 21 cells. Multiplication curve of the virus was established and immunohistochemical aspects of the process were investigated. Chronological study of successive steps of the formation and development of viral components allowed to see that the virus multiplication rate is low in this cell system. The parainfluenza antigen became detectable by immunofluorescence in the infected cell perinuclear region after a relatively long eclipse period (18 h) and synthetized virus has few RNA and induced no inclusion information in the cytoplasm or the nucleus. However, an important nuclear participation was noted: 72 h after inoculation, nuclear fluorescence was observed, as well as a nuclear DNA rising and frequent aberrant mitoses. Comparison between the two investigated strains led to the observation that the autochthonous D strain induced more frequent aberrant mitoses and more important cell destruction than the C243 one. Differences were also noted as regards the infecting and hemagglutinating titers.

Protection of weanling hamsters from experimental infection with wild-type parainfluenza virus type 3 (para 3) by cold-adapted mutants of para 3

Parainfluenza virus type 3 (para 3) was adapted to replicate at 20 degrees C, a nonpermissive temperature for wild-type (wt) para 3. Serial passage at 20 degrees C resulted in the generation of cold-adapted (ca) and temperature-sensitive (ts) mutants. These mutant viruses have been characterized both in vitro and in vivo [Belshe and Hissom (1982): Journal of Medical Virology 10:235-242; Crookshanks and Belshe (1984): Journal of Medical Virology 13:243-249]. We now report the evaluation of three mutants (clone 1150, passaged 12 times in the cold [cp12], clone 1146, passaged 18 times in the cold [cp18], and clone 1328, passaged 45 times in the cold [cp45]) for their ability to protect hamsters from infection by wild-type para 3. Ether-anesthetized male syrian hamsters were intranasally vaccinated with either wt para 3 (clone 127) or one of the ca para 3 mutants and on day 28 post-vaccination; each animal was intranasally challenged with 10(5.0) pfu of wt para 3. On days 1, 2, 3, and 4 post-challenge, 4 to 13 hamsters from each group were sacrificed, and the quantity of para 3 in the nasal turbinates and lungs was determined. Wt virus induced protection from challenge. cp12, cp18, and cp45 reduced the peak titer of wt replication in the lungs by greater than 100-fold, tenfold, and tenfold, respectively. The duration of virus replication was shortened also by intranasal vaccination with the mutants. These data give evidence of an inverse relationship between the degree of protection induced by vaccination with cold-adapted mutants and the number of passages of the virus in the cold.

Experimental parainfluenza virus infection in mice: growth and spread of a highly pathogenic variant of parainfluenza 3 virus in the mouse brain

We had previously showed that following intracerebral inoculation of newborn mice, the 910 N and M strains of bovine parainfluenza 3 virus induce a non-lethal hydrocephalus and a lethal disease with marked thymic and splenic atrophy, respectively. Moreover, only the M virus was lethal for 2-week-old mice. In the present study, we demonstrate that the M virus multiplies and spreads in the mouse brain invading the thalamus, hypothalamus and brain stem beyond the ependyma whereas the 910 N virus causes only slight ependymitis. This growth and spread of M virus was blocked by passive immunization 3 days after infection. Mouse embryo brain cell cultures were infected with M and 910 N viruses, about 50 per cent became antigen-positive for M whereas only a small proportion of cells were positive for the 910 N virus. However, the latter did produce higher yeilds of infectious virus than M.

Susceptibility of specific pathogen-free lambs to concentrations of Pasteurella haemolytica serotype A2 in aerosols

A 100-fold reduction in the numbers of organisms in an aerosol of Pasteurella haemolytica used to infect specific pathogen-free lambs did not alter the number of cases of pneumonia which resulted. In a separate experiment a further 10-fold reduction in the number of organisms in the aerosol did not cause fewer cases of pneumonia.

Respiratory disease in calves produced with aerosols of parainfluenza-3 virus and Pasteurella haemolytica

In four experiments, 22 calves were exposed to aerosols of parainfluenza-3 virus, followed by Pasteurella haemolytica at intervals of three to 13 days. The purpose of each experiment was to study viral-bacterial interactions in the respiratory tracts. Two experiments, in which the viral aerosols were diluted by the addition of air, produced sporadic temperature elevations while two experiments with undiluted viral aerosols produced consistent temperature elevations. Diluted viral aerosols produced lobular sized lesions in the lungs and hemagglutinating inhibition antibodies in sera, whilst undiluted aerosols produced a synergistic effect in the form of purulent pneumonia in ten of 14 calves when the interval between viral and bacterial aerosols was from three to ten days. Histopathological changes attributable to the virus only were seen in all experiments, and the histopathological changes due to mixed infection of parainfluenza-3 virus and P. haemolytica are described in detail. This is the first report of extensive purulent pneumonia in calves after parainfluenza-3 virus and P. haemolytica exposure. This was achieved using much smaller inocula than in experiments previously reported.

Experimental parainfluenzavirus infection in mice: fatal illness with atrophy of thymus and spleen in mice caused by a variant of parainfluenza 3 virus

Intracerebral inoculation of the YN strain of parainfluenza 3 virus was found to induce an acute fatal illness characterized by marked thymic and splenic atrophy in newborn mice. Previously we showed that the YN strain contains three distinct plaque-type variants, LT, SC, and M. Of these, the M-type variant induced this fatal illness, whereas the other two variants induced hydrocephalus.

The cotton rat as an experimental model of human parainfluenza virus type 3 disease

Intranasal or aerosol inoculation of cotton rats (Sigmodon hispidus) with human parainfluenza virus type 3 (P3) produces pulmonary changes which closely resemble human disease due to this agent. Active viral replication resulted in peak titers by day 2 of infection. Viral antigen was localized by immunofluorescence in bronchial epithelial cells alone (aerosol inoculation) or epithelial and alveolar cells (intranasal instillation). Cytopathic effects in epithelial cells was noted as early as day 2, and marked cellular proliferation occurred by day 7. Intranasal instillation of virus resulted in development of patchy interstitial pneumonitis. Mononuclear cell infiltration in the peribronchial and perivascular areas peaked on days 6 and 7. A brisk systemic antibody response was measured both by complement fixation and virus neutralization techniques. These data establish the value of the cotton rat as an experimental model for the study of bronchiolitis and pneumonia due to P3. Since previous work has demonstrated that respiratory syncytial virus and Mycoplasma pneumoniae also will replicate and cause pulmonary disease in cotton rats, comparative studies in a single animal species are facilitated.

Virus infection of endothelial cells

Endothelial injury is important in the pathogenesis of thrombosis, atherosclerosis, disseminated intravascular coagulation, and vasculitis. The ability of several common human viruses to infect cultures of endothelial cells obtained from human umbilical veins or bovine thoracic aorta was demonstrated. Indicators of infection included cytopathology, viral growth curves, and antigen detection by immunofluorescence. Herpes simplex virus type 1, adenovirus type 7, measles virus, and parainfluenza virus type 3 infected both human venous and bovine aorta endothelium. Mumps virus, poliovirus type 1, and echovirus type 9 grew only in human venous cells; coxsackievirus B4 infected only bovine arterial cultures; and cytomegalovirus, influenza A/Victoria/75 (H3N2) virus, and respiratory syncytial virus failed to grow in either cell culture. During replication some viruses caused acute lytic changes; some produced chronic, less destructive alterations; and other induced no apparent cytopathology. The results suggest that viral replication within endothelium may be important in the pathogenesis of viral disease of initiation of vessel-wall injury.

Injury of respiratory epithelium

The large surface area provided by the respiratory tract epithelium of humans for exposure to microbial agents and toxic substances in the environment makes this organ system very vulnerable but a good early indicator of adverse health effects. However, the complexity of pulmonary defense mechanisms complicates definition of the interactive effects of pollutants and infectious agents. Tracheal organ culture has been utilized to maintain organized, differentiated respiratory epithelium in vitro. This model system permits the exposure of respiratory epithelium to injurious agents in an easily visualized and controlled environment. Effects of individual toxin and/or infectious agents may be examined without the involvement of most host defenses and unwanted secondary microbial invaders which hamper interpretation of in vivo model studies. Further, elements of host immune response, pharmacologic agents and the like may be added selectively if desired. A body of information is being developed on specialized respiratory cell injury by various common pathogenic agents--including respiratory syncytial virus, parainfluenza virus type 3, Bordetella pertussis and Mycoplasma pneumoniae--through studies in tracheal organ cultures. These agents injure specialized epithelial cells in different ways, providing a spectrum of changes against which the added effects of toxic substances could be evaluated at the cellular and subcellular levels. Information on the pathogenesis of infectious/toxic injury could suggest new directions for human health research and for means to benefit the human host.

Parainfluenza-3 virus: difference in capacity of neuraminidase-weak and strong strains to infect young calves and to elicit cellular immune response

Calves less than four weeks old could not be infected with a neuraminidase-weak strain of parainfluenza-3 virus (Pi3) but were successfully infected with either of two neuraminidase-strong strains. The criteria for infection were virus excretion, cell-mediated and antibody-mediated immune responses. In the lymphocyte stimulation test, calves infected with the neuraminidase-strong Pi3 strain Tüb-E6 responded more strongly to antigen prepared from this strain than to antigen from the heterologous Pi3 strain Um-23. The non-immunoglobulin haemagglutination inhibition activity of the liquid phase of nasal secretions of newborn calves decreased after treatment with Vibrio cholerae neuraminidase. For virus-bound neuraminidase the liquid phase from newborn calves was a richer substrate than the liquid phase from older animals.