A regular subunit pattern seen on non-infectious Newcastle disease virus particles.

Area of Science:

• Virology
• Cell Biology
• Structural Biology

Background:

• Newcastle disease virus (NDV) is an important avian pathogen.
• Viral particle structure influences infectivity and replication.
• Previous studies described crystalline matrix protein arrays in other paramyxoviruses.

Purpose of the Study:

• To investigate the structural characteristics of NDV La Sota strain grown in MDBK cells.
• To determine the effect of trypsin on the observed viral particle structure.
• To explore the relationship between viral structure and the semi-permissive replication environment.

Main Methods:

• Cultivation of NDV La Sota and Ulster strains in MDBK tissue culture.
• Electron microscopy to visualize viral particle morphology.
• Observation of structural changes upon addition of trypsin.

Main Results:

• A pseudo-crystalline array of subunits was observed on NDV La Sota particles.
• This array was absent in NDV Ulster strain under similar conditions.
• The pseudo-crystalline structure disappeared when trypsin was added to the culture.
• Trypsin addition correlated with increased infectious virus production.

Conclusions:

• The pseudo-crystalline array is specific to the NDV La Sota strain in this culture system.
• The structure is associated with semi-permissive replication and is sensitive to trypsin.
• The observed phenomenon may relate to the arrangement of viral matrix proteins.