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Experimental infection of human leukocytes with parainfluenza 1 (6/94) virus
Abstract:
Parainfluenza 1 (6/94) virus replicated in both unstimulated and phytohemagglutinin (PHA)-stimulated human peripheral blood leukocytes (PBL). After exposure of PBL to 6/94 virus at a multiplicity of infection of 1, the presence of viral antigen was demonstrated by immunofluorescence in the cytoplasm of less than 1% of unstimulated PBL and 1 to 5% of macrophages. Small amounts (less than 50 mean egg infective doses per ml in most instances) of cell-free virus were present in 18 of 30 (60%) cell cultures tested from 3 to 8 days postinfection. Cell-free virus peaked 6 days postinfection. Virus replication was enhanced in PHA-stimulated cells. Approximately 1 to 10% of PHA-stimulated PBL contained viral antigen as evidenced by immunofluorescence, and cell-free virus was present in 19 of 25 (76%) of the cell cultures tested from 3 to 8 days postinfection. Paramyxovirus nucleocapsids and tubular aggregates were seen in the cytoplasm of approximately 5% of PHA-stimulated PBL and were visualized only in lymphocytes. No other unusual intracytoplasmic or intranuclear structures were seen.
Insights
Parainfluenza 1 virus replicates in human peripheral blood leukocytes (PBL), with enhanced replication in cells stimulated by phytohemagglutinin (PHA). This study details viral antigen presence and cell-free virus production in both stimulated and unstimulated PBL.
Area of Science:
- Virology
- Immunology
Background:
- Parainfluenza viruses are significant respiratory pathogens.
- Understanding their replication in human immune cells is crucial for disease control.
Purpose of the Study:
- To investigate the replication of Parainfluenza 1 (6/94) virus in human peripheral blood leukocytes (PBL).
- To compare viral replication in unstimulated versus phytohemagglutinin (PHA)-stimulated PBL.
Main Methods:
- Human peripheral blood leukocytes (PBL) were exposed to Parainfluenza 1 (6/94) virus.
- Viral antigen presence was detected using immunofluorescence.
- Cell-free virus was quantified using egg infective doses.
- Electron microscopy was used to visualize viral structures.
Main Results:
- Parainfluenza 1 virus replicated in both unstimulated and PHA-stimulated PBL.
- Viral antigen was detected in unstimulated PBL (less than 1%) and macrophages (1-5%).
- Replication was enhanced in PHA-stimulated PBL (1-10% viral antigen), with peak cell-free virus at 6 days post-infection.
- Paramyxovirus nucleocapsids were observed in PHA-stimulated lymphocytes.
Conclusions:
- Parainfluenza 1 virus can infect and replicate within human peripheral blood leukocytes.
- Phytohemagglutinin (PHA) stimulation enhances Parainfluenza 1 virus replication in PBL, particularly in lymphocytes.