Plaque formation assay for human parainfluenza virus type 1

Area of Science:

• Virology
• Cell Biology

Background:

• Human parainfluenza virus type 1 (hPIV1) typically does not form visible plaques in standard cell lines using existing plaque assays.
• Serum proteins in overlay media often inhibit hPIV1 plaque visualization in Lewis lung carcinoma-monkey kidney (LLC-MK(2)) cells.

Purpose of the Study:

• To develop a reliable plaque formation assay for the isolation and titration of hPIV1.
• To establish a method for evaluating antiviral reagents and conducting epidemiologic research on hPIV1.

Main Methods:

• Developed a modified plaque assay using serum-free Eagle's minimum essential medium with agarose and acetylated trypsin for initial overlay, followed by neutral red staining.
• Utilized Lewis lung carcinoma-monkey kidney (LLC-MK(2)) cells for hPIV1 plaque formation.
• Employed a plaque reduction assay with anti-hPIV1 antibody to assess viral inhibitors.

Main Results:

• The new assay successfully induced large plaque formation for both laboratory and clinical hPIV1 strains in LLC-MK(2) cells.
• Complete elimination of serum proteins was essential for plaque visualization.
• The plaque reduction assay demonstrated efficacy in evaluating antiviral activity.

Conclusions:

• The developed plaque formation assay is effective for hPIV1 isolation and titration.
• This assay serves as a valuable tool for assessing antiviral efficacy and for hPIV1-related epidemiologic studies.