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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 11, 2013
Interleukin-4 is needed for the infection of monocytes by human cytomegalovirus
1First Department of Internal Medicine, Kurume University School of Medicine, Asahimachi 67, Kurume, Fukuoka 839-0011 Japan. kitajima@med.kurume-u.ac.jp
Objective:
We studied the ability of human cytomegalovirus (HCMV) to infect peripheral blood mononuclear cells (PBMC) pretreated with or without Th2-cytokine interleukin-4 (IL-4) in vitro.
Methods:
Adherent cells and nonadherent cells were obtained from PBMC. We inoculated these cells with HCMV at concentrations ranging from 0 to 10 ng/ml of IL-4. Immediate-early antigen-1 (IE-1) and glycoprotein H (gH) mRNAs were detected using the reverse-transcription polymerase chain reaction.
Results:
IE-1 and gH mRNAs could be detected in monocytes pretreated with IL-4. In contrast, no IE-1 mRNA was detected in monocytes pretreated without IL-4. We tested whether higher infectious titers could result in the infection of monocytes whether or not they were pretreated with IL-4. However, no IE-1 mRNA was detected in the monocytes not pretreated with IL-4. To elucidate how HCMV-infected monocytes affect lung tissue, human embryonic lung fibroblasts MRC-5 were cocultured with HCMV-infected monocytes. The cytopathic effects of HCMV were observed microscopically and was confirmed by direct immunoperoxidase staining with a human monoclonal antibody against the HCMV IE-1.
Conclusion:
Our data strongly suggest that the ability of HCMV to infect monocytes may correlate with the presence of IL-4.
Insights
Human cytomegalovirus (HCMV) infection of monocytes depends on interleukin-4 (IL-4). Pretreatment with IL-4 enabled HCMV to infect monocytes, as shown by mRNA detection, while untreated monocytes remained uninfected.
Area of Science:
- Virology
- Immunology
Background:
- Human cytomegalovirus (HCMV) is a common pathogen with diverse cellular targets.
- Peripheral blood mononuclear cells (PBMC) are key immune cells involved in antiviral responses.
Purpose of the Study:
- To investigate the role of Th2-cytokine interleukin-4 (IL-4) in HCMV infection of PBMC in vitro.
- To determine if IL-4 enhances HCMV's ability to infect monocyte populations within PBMC.
Main Methods:
- PBMC were isolated into adherent and nonadherent fractions.
- Cells were pretreated with varying concentrations of IL-4 or left untreated.
- HCMV infection was assessed by detecting immediate-early antigen-1 (IE-1) and glycoprotein H (gH) mRNA using reverse-transcription polymerase chain reaction (RT-PCR).
- Coculture experiments with human embryonic lung fibroblasts (MRC-5) were performed to observe HCMV-induced cytopathic effects.
Main Results:
- IL-4 pretreatment significantly enhanced HCMV infection in monocytes, evidenced by detectable IE-1 and gH mRNA.
- Monocytes not pretreated with IL-4 did not show detectable IE-1 mRNA, even with higher HCMV titers.
- HCMV-infected monocytes exhibited cytopathic effects in cocultured MRC-5 cells, confirmed by microscopy and immunoperoxidase staining.
Conclusions:
- The presence of IL-4 is a critical factor correlating with HCMV's ability to infect human monocytes.
- IL-4 may prime monocytes for HCMV entry, suggesting a mechanism for viral persistence or pathogenesis.
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