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An In vitro Model to Study Immune Responses of Human Peripheral Blood Mononuclear Cells to Human Respiratory Syncytial Virus Infection
Published on: December 10, 2013
Contribution of the human parainfluenza virus type 3 HN-receptor interaction to pathogenesis in vivo
G A Prince1, M G Ottolini, A Moscona
1Virion Systems, Inc., Rockville, Maryland, USA.
Abstract:
The envelope of human parainfluenza virus type 3 (HPF3) contains two viral glycoproteins, the hemagglutinin-neuraminidase (HN) protein and the fusion (F) protein. In a previous study, highly fusogenic variant HPF3 viruses were isolated, including two, C-0 and C-22, that exhibit increased avidity for sialic acid receptors due to single amino acid changes in the HN protein and one, C-28, that has decreased neuraminidase activity relative to that of the wild type (wt) and is delayed in the release of virus particles into the supernatant fluid. These variants form very large plaques and destroy a cell monolayer more rapidly than does wt HPF3 in cell culture. These variant viruses allowed us to formulate hypotheses about the roles of HN in pathogenesis. We investigated the behavior of wt HPF3 and the three variant viruses in the cotton rat model. In the cotton rat, there was no delayed clearance of any of the variant viruses compared to that of the wt. The variant plaque morphology was preserved in vivo, and there was no reversion to the wt phenotype in the infected animals. In spite of a slight advantage of wt virus in viral titer, there were no differences in the severities of peribronchiolitis between wt viruses and the variants. However, there were marked differences in severities in alveolitis and interstitial pneumonitis when each of the three variants was compared to the wt, with the variants causing enhanced disease. Thus, despite similar or lower viral titers and similar clearance rates, the variants caused more extensive disease in the lung. The results show that mutations in HN conferring altered fusion properties in cell culture also confer striking differences in the ability of HPF3 to cause extensive disease in the cotton rat lung and that this effect is dissociated from any effect on viral replication.
Insights
Mutations in the hemagglutinin-neuraminidase (HN) protein of human parainfluenza virus type 3 (HPF3) enhanced disease severity in cotton rats, independent of viral replication or clearance rates. These HN variants caused more extensive lung inflammation.
Area of Science:
- Virology
- Immunology
- Pathogenesis
Background:
- Human parainfluenza virus type 3 (HPF3) envelope glycoproteins, hemagglutinin-neuraminidase (HN) and fusion (F) proteins, are critical for viral infection.
- Previous studies identified HPF3 variants with altered HN protein functions, including increased sialic acid receptor avidity and decreased neuraminidase activity.
- These variants exhibited distinct plaque morphologies and rapid cell monolayer destruction in vitro, suggesting altered pathogenic potential.
Purpose of the Study:
- To investigate the in vivo pathogenicity of HPF3 variants with mutations in the HN protein using the cotton rat model.
- To determine if altered HN protein properties correlate with disease severity, viral clearance, and replication in a mammalian host.
- To elucidate the role of HN protein in HPF3-mediated pathogenesis beyond its effects on viral fusion and replication.
Main Methods:
- Infection of cotton rats with wild-type (wt) HPF3 and three HN variants (C-0, C-22, C-28).
- Assessment of viral clearance, viral titers, and plaque morphology in infected animals.
- Histopathological analysis of lung tissues to evaluate the severity of peribronchiolitis, alveolitis, and interstitial pneumonitis.
Main Results:
- All variant viruses showed similar clearance rates and plaque morphology preservation in vivo compared to wt HPF3.
- No significant differences in viral titers or peribronchiolitis severity were observed between wt and variant viruses.
- Variant viruses caused significantly enhanced alveolitis and interstitial pneumonitis, indicating increased lung disease severity despite similar viral loads.
Conclusions:
- Mutations in the HPF3 HN protein that alter fusion properties in vitro also lead to increased severity of lung disease in cotton rats.
- The enhanced pathogenicity of these HN variants is dissociated from their viral replication efficiency and clearance rates.
- The HN protein plays a crucial role in HPF3 pathogenesis, influencing disease outcome independently of viral replication kinetics.
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