Cytomegalovirus infection. Regulation of inflammation

Mesenchymal Stem Cell-Derived Exosomes Attenuate Murine Cytomegalovirus-Infected Pneumonia via NF-κB/NLRP3 Signaling Pathway

Reactivation and infection with cytomegalovirus (CMV) are frequently observed in recipients of solid organ transplants, bone marrow transplants, and individuals with HIV infection. This presents an increasing risk of allograft rejection, opportunistic infection, graft failure, and patient mortality. Among immunocompromised hosts, interstitial pneumonia is the most critical clinical manifestation of CMV infection. Recent studies have demonstrated the potential therapeutic benefits of exosomes derived from mesenchymal stem cells (MSC-exos) in preclinical models of acute lung injury, including pneumonia, ARDS, and sepsis. However, the role of MSC-exos in the pathogenesis of infectious viral diseases, such as CMV pneumonia, remains unclear. In a mouse model of murine CMV-induced pneumonia, we observed that intravenous administration of mouse MSC (mMSC)-exos reduced lung damage, decreased the hyperinflammatory response, and shifted macrophage polarization from the M1 to the M2 phenotype. Treatment with mMSC-exos also significantly reduced the infiltration of inflammatory cells and pulmonary fibrosis. Furthermore, in vitro studies revealed that mMSC-exos reversed the hyperinflammatory phenotype of bone marrow-derived macrophages infected with murine CMV. Mechanistically, mMSC-exos treatment decreased activation of the NF-κB/NLRP3 signaling pathway both in vivo and in vitro. In summary, our findings indicate that mMSC-exo treatment is effective in severe CMV pneumonia by reducing lung inflammation and fibrosis through the NF-κB/NLRP3 signaling pathway, thus providing promising therapeutic potential for clinical CMV infection.

US28 actions in HCMV infection: lessons from a versatile hijacker

Mimicking host proteins is a strategy adopted by several herpesviruses to exploit the host cell for their own benefit. In this respect the human cytomegalovirus (HCMV) chemokine receptor homologue US28, has been extensively studied. Molecular pirates such as US28 can teach us about crucial events in HCMV infection and may either offer a potential target for antiviral therapy or provide an alternative strategy to immune suppression. Despite elaborate research into the chemokine binding affinity, signalling properties, intracellular trafficking and expression kinetics of US28, a solid hypothesis about the role of US28 in HCMV infection has not yet been proposed. It appears that US28 may behave as a molecular pirate that employs smart strategies for cell entry, host gene regulation and immune evasion. This review will elaborate on these aspects of US28 biology and discuss possible implications for HCMV infection.

Cytomegalovirus infection, viral DNA, and immediate early-1 gene expression in rejecting rat liver allografts

BACKGROUND

Cytomegalovirus (CMV) infection has been linked to acute and chronic rejection. We have previously shown that concomitant rat cytomegalovirus (RCMV) infection increases portal inflammation and bile duct destruction in rejecting rat liver allografts. Many of the pro-inflammatory effects of CMV have been attributed to the immediate early (IE) proteins of CMV. We wanted to investigate whether RCMV and IE-1 gene expression persist in the liver graft in our model.

METHODS

Liver transplantations were performed from PVG (RT1c) into BN (RT1n) rats. One day after transplantation, the rats were infected with RCMV. No immunosuppression was given. The graft infection was studied by viral culture, immunofluorescence, DNA in situ hybridization and RT-PCR for the detection of IE-1 mRNA at various time points.

RESULTS

RCMV caused an active infection from 5 days to 2 weeks after transplantation, during which infectious virus was found in the graft. Thereafter the cultures were negative. RCMV antigens and DNA were found in hepatocytes, endothelial, inflammatory, and bile duct cells during the active infection. At 4 weeks, RCMV DNA positive hepatocytes, endothelial, inflamma tory, and bile duct cells could still be found, but in much smaller quantities. IE-1 mRNA expression was, however, only detected during the active infection, not at 4 weeks postinfection.

CONCLUSIONS

RCMV IE-1 expression does not persist in the graft after the active infection, although some viral DNA can be detected in the graft up to 4 weeks. In our model, the CMV-induced increase in graft damage does not seem to require the continued expression of IE-1.

Cytomegalovirus infection and graft rejection in renal transplantation

BACKGROUND

Cytomegalovirus (CMV) infection and CMV disease have been associated with acute and chronic graft rejection. The introduction of the sensitive CMV antigenemia pp65 assay for detection of CMV infection allowed us to study the time course of CMV infection and acute rejection and the long-term outcome in renal transplant recipients with and without a CMV risk constellation.

METHODS

Prospective single center study including 48 renal transplant recipients at risk for CMV infection (donor and/or recipient CMV seropositive) and a control group of 36 CMV seronegative recipients of CMV seronegative kidney donors. Evidence of CMV infection was monitored by the CMV antigenemia pp65 assay every 1 to 2 weeks and compared with the occurrence of acute rejection in the posttransplant period and graft function at 5 years.

RESULTS

CMV infection developed in 83% (40/48) of patients of the CMV risk group within 4 months posttransplant. A total of 18 of patients experienced an acute rejection episode (control group 16/36; P=0.65). In 12/18 CMV infection followed rejection and in three patients antigenemia preceded the diagnosis of rejection. In three patients CMV antigenemia remained negative. Five-year follow up: Patient survival (44/48 vs. 31/36; P=0.48), graft survival (38/48 vs. 27/36; P=0.79), number of patients with at least one acute rejection episode: CMV risk group: 42.1%, control group 51% (P=0.46), serum creatinine: CMV risk group:130 +/- 66 micromol/iter, control group: 126 +/- 37 micromol/ liter (P=0.56), proteinuria: CMV risk group: 0.02 +/- 0.02 g/mmol creatinine, control group: 0.02 +/- 0.02 g/mmol creatinine (P=1.0).

CONCLUSION

CMV infection within 4 months posttransplant, as defined by a positive antigenemia assay was not found to be a risk factor for acute graft rejection or chronic graft dysfunction at 5 years.