Cytomegalovirus reactivation enhances the virulence of Staphylococcus aureus pneumonia in a mouse model

Docosahexaenoic acid supplementation represses the early immune response against murine cytomegalovirus but enhances NK cell effector function

BACKGROUND

Docosahexaenoic acid (DHA) supplementation is beneficial for several chronic diseases; however, its effect on immune regulation is still debated. Given the prevalence of cytomegalovirus (CMV) infection and because natural killer (NK) cells are a component of innate immunity critical for controlling CMV infection, the current study explored the effect of a DHA-enriched diet on susceptibility to murine (M) CMV infection and the NK cell effector response to MCMV infection.

RESULTS

Male C57BL/6 mice fed a control or DHA-enriched diet for 3 weeks were infected with MCMV and sacrificed at the indicated time points postinfection. Compared with control mice, DHA-fed mice had higher liver and spleen viral loads at day 7 postinfection, but final MCMV clearance was not affected. The total numbers of NK cells and their terminal mature cell subset (KLRG1+ and Ly49H+ NK cells) were reduced compared with those in control mice at day 7 postinfection but not day 21. DHA feeding resulted in higher IFN-γ and granzyme B expression in splenic NK cells at day 7 postinfection. A mechanistic analysis showed that the splenic NK cells of DHA-fed mice had enhanced glucose uptake, increased CD71 and CD98 expression, and higher mitochondrial mass than control mice. In addition, DHA-fed mice showed reductions in the total numbers and activation levels of CD4+ and CD8+ T cells.

CONCLUSIONS

These results suggest that DHA supplementation represses the early response to CMV infection but preserves NK cell effector functions by improving mitochondrial activity, which may play critical roles in subsequent MCMV clearance.

Herpesviruses in Critically Ill Patients With ARDS

Reactivation of herpsviruses, mainly HSV, CMV and EBV, are frequent among critically ill patients. Although they are not immunocompromised from a classical point of view, these patients often present an alteration of their immune system favoring viral reactivation. Seropositive patients with sepsis and under mechanical ventilation are particularly at risk. Herpesviruses have a pulmonary tropism and can be responsible for non-resolving forms of acute respiratory distress syndrome with high mortality. However, the direct causality between herpesviruses reactivation and impaired outcomes among severely ill patients remains under debate.

Potent synergistic combination of rosuvastatin and levofloxacin against Staphylococcus aureus: in vitro and in vivo study

AIMS

The present study aims to evaluate the capability of rosuvastatin to synergize with levofloxacin against Staphylococcus aureus.

METHODS AND RESULTS

Rosuvastatin inhibited the growth of S. aureus with minimum inhibitory concentration of 16 μg ml^-1 . Additionally, it showed a bactericidal effect at 4x minimum inhibition concentration. Using a checkerboard method, a synergistic effect was recorded when rosuvastatin was combined with levofloxacin showing against S. aureus isolate 28 (S 28). Furthermore, this combination was also able to display a significant reduction in biofilm formation (92·8%) and suppress the production of coagulase and β-haemolysin, and virulence factors of S. aureus isolate 28. An animal model for wound infection was used to assess the therapeutic effect of the test combination, in vivo. It was found that the test combination reduced the bacterial burden in the infected wounds by 91·3%. Pathological and histological analyses have revealed a decline in cell infiltration in the excisional wound skin tissue after treatment with rosuvastatin and levofloxacin combination.

CONCLUSIONS

Rosuvastatin combined with levofloxacin can be considered as a promising solution to combat S. aureus antibiotic resistance phenomenon.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study unveils the potential effect of rosuvastatin when used in combination with levofloxacin can be used as a topical antibacterial agent to treat S. aureus skin infections.

A Review of Murine Cytomegalovirus as a Model for Human Cytomegalovirus Disease-Do Mice Lie?

Since murine cytomegalovirus (MCMV) was first described in 1954, it has been used to model human cytomegalovirus (HCMV) diseases. MCMV is a natural pathogen of mice that is present in wild mice populations and has been associated with diseases such as myocarditis. The species-specific nature of HCMV restricts most research to cell culture-based studies or to the investigation of non-invasive clinical samples, which may not be ideal for the study of disseminated disease. Initial MCMV research used a salivary gland-propagated virus administered via different routes of inoculation into a variety of mouse strains. This revealed that the genetic background of the laboratory mice affected the severity of disease and altered the extent of subsequent pathology. The advent of genetically modified mice and viruses has allowed new aspects of disease to be modeled and the opportunistic nature of HCMV infection to be confirmed. This review describes the different ways that MCMV has been used to model HCMV diseases and explores the continuing difficulty faced by researchers attempting to model HCMV congenital cytomegalovirus disease using the mouse model.

Involvement of heparan sulfate during mouse cytomegalovirus infection in murine-derived immortalized neuronal cell line

Cytomegalovirus infection cause of severe developmental disorders of the CNS. Aim: In this study, we utilized a differentiated mouse-derived hippocampal cell line (dHT22) to understand mouse CMV (MCMV) infection. Results: The expression of immediate early genes ( IE) 1 and 3 confirmed the time-dependent susceptibility of dHT22 cells to MCMV infection. MCMV infection alters the cellular distribution of heparan sulfate (HS). In addition, pretreatment with heparinase significantly reduces virus infectivity. Conclusion: The compartmentalization of HS in MCMV infected cells suggests multiple roles of HS in virus life cycle ranging from viral entry to viral transport and cellular remodeling. An enzymatic heparinase assay confirmed that HS is critical for viral entry and trafficking.

Herpes simplex virus and Cytomegalovirus reactivation among severe ARDS patients under veno-venous ECMO

Background

Herpesviridae reactivation among non-immunocompromised critically ill patients is associated with impaired prognosis, especially during acute respiratory distress syndrome (ARDS). However, little is known about herpes simplex virus (HSV) and Cytomegalovirus (CMV) reactivation occurring in patients with severe ARDS under veno-venous extracorporeal membrane oxygenation (ECMO). We tried to determine the frequency of Herpesviridae reactivation and its impact on patients’ prognosis during ECMO for severe ARDS.

Results

During a 5-year period, 123 non-immunocompromised patients with a severe ARDS requiring a veno-venous ECMO were included. Sixty-seven patients (54%) experienced HSV and/or CMV reactivation during ECMO course (20 viral co-infection, 40 HSV alone, and 7 CMV alone). HSV reactivation occurred earlier than CMV after the beginning of MV [(6–15) vs. 19 (13–29) days; p < 0.01] and after ECMO implementation [(2–8) vs. 14 (10–20) days; p < 0.01]. In univariate analysis, HSV/CMV reactivation was associated with a longer duration of mechanical ventilation [(22–52.5) vs. 17.5 (9–28) days; p < 0.01], a longer duration of ECMO [15 (10–22.5) vs. 9 (5–14) days; p < 0.01], and a prolonged ICU [29 (19.5–47.5) vs. 16 (9–30) days; p < 0.01] and hospital stay [44 (29–63.5) vs. 24 (11–43) days; p < 0.01] as compared to non-reactivated patients. However, in multivariate analysis, viral reactivation remained associated with prolonged MV only. When considered separately, both HSV and CMV reactivation were associated with a longer duration of MV as compared to non-reactivation patients [29 (19.5–41) and 28 (20.5–37), respectively, vs. 17.5 (9–28) days; p < 0.05]. Co-reactivation patients had a longer duration of MV [58.5 (38–72.3); p < 0.05] and ICU stay [51.5 (32.5–69) vs. 27.5 (17.75–35.5) and 29 (20–30.5), respectively] as compared to patients with HSV or CMV reactivation alone. In multivariate analysis, HSV reactivation remained independently associated with a longer duration of MV and hospital length of stay.

Conclusions

Herpesviridae reactivation is frequent among patients with severe ARDS under veno-venous ECMO and is associated with a longer duration of mechanical ventilation. The direct causative link between HSV and CMV reactivation and respiratory function worsening under ECMO remains to be confirmed.

Evodiamine alleviates severe pneumonia induced by methicillin-susceptible Staphylococcus aureus following cytomegalovirus reactivation through suppressing NF-κB and MAPKs

Viral and bacterial severe pneumonia are leading causes of mortality across the globe. Evodiamine (Evo), a botanical alkaloid, has anti-inflammatory and antibacterial properties. In the present study, the effect of Evo on severe pneumonia induced by methicillin-susceptible Staphylococcus aureus (MSSA) following cytomegalovirus (CMV) reactivation, and its mechanism, were evaluated. In vitro, the protein and mRNA expression levels of inflammatory cytokines were determined by enzyme-linked immunosorbent assay and reverse transcription-quantitative polymerase chain reaction analysis, respectively. The expression levels of associated proteins of the nuclear factor (NF)-κB and mitogen-activated protein kinase (MAPK) signaling pathways were measured by western blot analysis. In vivo, mortality rate, weight loss, histological changes, lung bacteria count, inflammatory cytokines, and the expression proteins of associated with the NF-κB and MAPK signaling pathways were examined. The results revealed that Evo dose-dependently reduced the protein and mRNA expression levels of tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-1β, and inhibited the levels of phosphorylated (p-) inhibitor of NF-κBα, p-extracellular signal-regulated kinase, p-c-Jun N-terminal kinase and p-p38, and decreased the nuclear trans-location of NF-κB/p65 in BEAS-2B cells infected with MSSA. Furthermore, Evo markedly improved survival rate, decreased body weight loss and bacterial count, and attenuated lung histological alterations and the levels of inflammatory factors. In addition, the NF-κB and MAPK signaling pathways were significantly inhibited. Taken together, Evo effectively alleviated pneumonia via the NF-κB and MAPK pathways and may be a potential therapeutic agent for treating severe pneumonia.

A constant companion: immune recognition and response to cytomegalovirus with aging and implications for immune fitness

Approximately 50% of individuals aged 6-49 years in the United States are infected with cytomegalovirus (CMV), with seroprevalence increasing with age, reaching 85-90% by 75-80 years according to Bate et al. (Clin Infect Dis 50 (11): 1439-1447, 2010) and Pawelec et al. (Curr Opin Immunol 24:507-511, 2012). Following primary infection, CMV establishes lifelong latency with periodic reactivation. Immunocompetent hosts experience largely asymptomatic infection, but CMV can cause serious illness in immunocompromised populations, such as transplant patients and the elderly. Control of CMV requires constant immune surveillance, and recent discoveries suggest this demand alters general features of the immune system in infected individuals. Here, we review recent advances in the understanding of the immune response to CMV and the role of CMV in immune aging and fitness, while highlighting the importance of potential confounding factors that influence CMV studies. Understanding how CMV contributes to shaping "baseline" immunity has important implications for a host's ability to mount effective responses to diverse infections and vaccination.

Making Mouse Models That Reflect Human Immune Responses

Humans are infected with a variety of acute and chronic pathogens over the course of their lives, and pathogen-driven selection has shaped the immune system of humans. The same is likely true for mice. However, laboratory mice we use for most biomedical studies are bred in ultra-hygienic environments, and are kept free of specific pathogens. We review recent studies that indicate that pathogen infections are important for the basal level of activation and the function of the immune system. Consideration of these environmental exposures of both humans and mice can potentially improve mouse models of human disease.