Human Metapneumovirus: Laboratory Methods for Isolation, Propagation, and Plaque Titration
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Updated: Jan 27, 2026
Titration of Human Coronaviruses Using an Immunoperoxidase Assay
Published on: April 28, 2008
Lilia J Bernal1, Myriam Velandia-Romero2, Carolina Guevara3
1Facultad de Odontología, Universidad Nacional de Colombia, Bogotá, Colombia.
Abstract:
The human metapneumovirus (hMPV) is an important viral agent associated with severe infections of the upper and lower airways, especially in young children and immunosuppressed subjects. Nevertheless, in vitro studies of hMPV are very difficult due to the little knowledge we have on its laboratory manipulation.
Objective:
The aim of this study was to isolate and propagate hMPV from patients, and to establish a method to quantify the virus by plaque assay.
Method:
As part of a Latin American respiratory virus surveillance study, 12 nasal secretion samples - hMPV-positive by direct fluorescence - were inoculated on LLC-MK2 cells to isolate the virus. The supernatants were re-inoculated and the cytopathic effect and syncytium formation were evaluated daily; the infection was confirmed by immunofluorescence and RT-PCR. A protocol to titrate the harvested virus was established inoculating serial dilutions on LLC-MK2 cells, and agarose was then added as an overlay. After different time periods, the monolayers were fixed and stained with Naphthol blue/black or crystal violet and finally the viral titer was obtained.
Results:
Eight out of 12 hMPV-positive respiratory samples were positive for the isolation and confirmed by RT-PCR and immunofluorescence, but the cytopathic effect and syncytium formation were observed only in 5 cultures. One out of 8 viral isolates was used for propagation and plaque assay standardization. We found that incubation for 7 days in the semisolid overlay yielded plaques with appropriate size and shape to be counted, although crystal violet staining showed slightly larger plaques than those seen with Naphthol blue/black staining.
Conclusions:
The isolation and propagation from patient-derived hMPV and the standardization of a practical, reliable, and inexpensive method of detection and quantification of hMPV were carried out, without the additional use of antibodies that had not been reported previously. These results offer some important insights for future studies of cellular and molecular biology of hMPV.
Insights
Researchers successfully isolated and propagated human metapneumovirus (hMPV) from patient samples. A new, cost-effective plaque assay method was developed for quantifying hMPV, aiding future research.
Area of Science:
- Virology
- Respiratory Virus Research
- Infectious Diseases
Background:
- Human metapneumovirus (hMPV) causes severe respiratory infections, particularly in vulnerable populations.
- In vitro studies of hMPV are challenging due to limited understanding of its laboratory handling.
- Effective methods for isolating, propagating, and quantifying hMPV are crucial for research.
Purpose of the Study:
- To isolate and propagate hMPV from clinical samples.
- To establish and standardize a reliable plaque assay for hMPV quantification.
- To overcome difficulties in laboratory manipulation of hMPV for in vitro studies.
Main Methods:
- hMPV isolation from 12 nasal secretion samples using LLC-MK2 cells.
- Confirmation of infection via immunofluorescence and RT-PCR.
- Development of a plaque assay protocol involving serial dilutions, agarose overlay, and staining (Naphthol blue/black or crystal violet).
Main Results:
- Successful isolation and confirmation of hMPV from 8 out of 12 samples.
- One hMPV isolate was used to standardize a plaque assay.
- A 7-day incubation period with agarose overlay yielded countable plaques; crystal violet staining resulted in slightly larger plaques than Naphthol blue/black.
Conclusions:
- A practical, reliable, and inexpensive method for detecting and quantifying hMPV was successfully developed and standardized.
- The study provides a valuable tool for future research into the cellular and molecular biology of hMPV.
- This method enables further investigation of hMPV without requiring additional antibodies.
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