CMV in critically ill patients: pathogen or bystander?

Prevalence of herpes and respiratory viruses in induced sputum among hospitalized children with non typical bacterial community-acquired pneumonia

Objective

Few comprehensive studies have searched for viruses in infants and young children with community-acquired pneumonia (CAP) in China. The aim of this study was to investigate the roles of human herpes viruses (HHVs) and other respiratory viruses in CAP not caused by typical bacterial infection and to determine their prevalence and clinical significance.

Methods

Induced sputum (IS) samples were collected from 354 hospitalised patients (infants, n = 205; children, n = 149) with respiratory illness (CAP or non-CAP) admitted to Wenling Hospital of China. We tested for HHVs and respiratory viruses using PCR-based assays. The epidemiological profiles were also analysed.

Results

High rate of virus detection (more than 98%) and co-infection (more than 80%) were found among IS samples from 354 hospitalised infants and children with respiratory illness in this study. Of 273 CAP samples tested, CMV (91.6%), HHV-6 (50.9%), RSV (37.4%), EBV (35.5%), HBoV (28.2%), HHV-7 (18.3%) and rhinovirus (17.2%) were the most commonly detected viruses. Of 81 non- CAP samples tested, CMV (63%), RSV (49.4%), HHV-6 (42%), EBV (24.7%), HHV-7 (13.6%) and HBoV (8.6%) were the dominant viruses detected. The prevalence of several viral agents (rhinovirus, bocavirus, adenovirus and CMV) among IS samples of CAP were significantly higher than that of non-CAP control group. We also found the prevalence of RSV coinfection with HHVs was also higher among CAP group than that of non-CAP control.

Conclusions

With sensitive molecular detection techniques and IS samples, high rates of viral identification were achieved in infants and young children with respiratory illness in a rural area of China. The clinical significance of rhinovirus, bocavirus, adenovirus and HHV (especially CMV) infections should receive greater attention in future treatment and prevention studies of CAP in infants and children.

Asymptomatic DNAemia heralds CMV-associated NEC: case report, review, and rationale for preemption

Human cytomegalovirus (CMV) infection may be acquired in very low birth weight and extremely low birth weight (ELBW) infants from breast milk. The clinical relevance of such infections is uncertain. There is no consensus on whether screening breast milk for CMV, freezing/pasteurizing milk before feeding, or performing virological monitoring on at-risk infants is warranted. We describe an ELBW infant who acquired CMV postnatally from breast milk and developed CMV sepsis syndrome and clinical evidence of necrotizing enterocolitis (NEC) at ≈ 5 weeks of age. The availability of serial dried blood spots from day of life (DOL) 4 to 21, coincidentally obtained for a metabolic study, provided the novel opportunity to retrospectively test for and quantify the magnitude of CMV DNAemia. DNAemia was present for several weeks before the onset of severe CMV disease, first being noted on DOL 18 and increasing in magnitude daily to 4.8 log10 genomes/mL on DOL 21, approximately 8 days before the onset of abdominal distension and 15 days before the onset of CMV sepsis syndrome and NEC. After surgical resection, supportive care, and ganciclovir therapy, the infant recovered. This case underscores the importance of including CMV infection in the differential diagnosis of sepsis and NEC in premature infants. This case also suggests the value of prospective virological monitoring in at-risk low birth weight and ELBW infants. Future studies should examine the potential utility of preemptive monitoring for, and possibly treatment of, CMV DNAemia in premature infants, which may herald the onset of serious disease.

Viral pathogens and acute lung injury: investigations inspired by the SARS epidemic and the 2009 H1N1 influenza pandemic

Acute viral pneumonia is an important cause of acute lung injury (ALI), although not enough is known about the exact incidence of viral infection in ALI. Polymerase chain reaction-based assays, direct fluorescent antigen (DFA) assays, and viral cultures can detect viruses in samples from the human respiratory tract, but the presence of the virus does not prove it to be a pathogen, nor does it give information regarding the interaction of viruses with the host immune response and bacterial flora of the respiratory tract. The severe acute respiratory syndrome (SARS) epidemic and the 2009 H1N1 influenza pandemic provided a better understanding of how viral pathogens mediate lung injury. Although the viruses initially infect the respiratory epithelium, the relative role of epithelial damage and endothelial dysfunction has not been well defined. The inflammatory host immune response to H1N1 infection is a major contributor to lung injury. The SARS coronavirus causes lung injury and inflammation in part through actions on the nonclassical renin angiotensin pathway. The lessons learned from the pandemic outbreaks of SARS coronavirus and H1N1 capture key principles of virally mediated ALI. There are pathogen-specific pathways underlying virally mediated ALI that converge onto a common end pathway resulting in diffuse alveolar damage. In terms of therapy, lung protective ventilation is the cornerstone of supportive care. There is little evidence that corticosteroids are beneficial, and they might be harmful. Future therapeutic strategies may be targeted to specific pathogens, the pathogenetic pathways in the host immune response, or enhancing repair and regeneration of tissue damage.

Desirability and feasibility of a vaccine against cytomegalovirus

Publication of a report from the Institute of Medicine in 2000 showing that a vaccine against cytomegalovirus (CMV) would likely be cost saving was very influential and encouraged the clinical evaluation of candidate vaccines. The major objective of a CMV vaccination program would be to reduce disease caused by congenital CMV infection, which is the leading viral cause of sensorineural hearing loss and neurodevelopmental delay. CMV has challenges as a vaccine target because it is a herpesvirus, it persists lifelong despite host immunity, infected individuals can be reinfected with new strains, overt disease occurs in those with immature or impaired immune systems and persons with this infection do not usually report symptoms. Nevertheless, natural immunity against CMV provides some protection against infection and disease, natural history studies have defined the serological and molecular biological techniques needed for endpoints in future clinical trials of vaccines and CMV is not highly communicable, suggesting that it may not be necessary to achieve very high levels of population immunity through vaccination in order to affect transmission. Three phase 2 CMV vaccine studies have been completed in the last 3 years and all report encouraging outcomes. A key international meeting was organized by the Food and Drug Administration in January 2012 at which interested parties from regulatory bodies, industry and academia discussed and prioritised designs for phase 2 and phase 3 clinical trials. Vaccines able to prevent primary infection with CMV and to boost the immune response of those already infected are desirable. The major target populations for a CMV vaccine include women of childbearing age and adolescents. Toddlers represent another potential population, since an effect of vaccine in this age group could potentially decrease transmission to adults. In addition, prospective recipients of transplants and patients with AIDS would be expected to benefit.

Bride and groom in systemic inflammation--the bells ring for complement and Toll in cooperation

Attenuating the sepsis-induced systemic inflammatory response, with subsequent homeostatic imbalance, has for years been one of the main tasks in sepsis related research. Complement and the TLR family constitute two important upstream sensor and effector-systems of innate immunity. Although they act as partly independent branches of pattern recognition, recent evidence indicate a considerable cross-talk implying that they can either compensate, synergize or antagonize each other. Combined inhibition of these pathways is therefore a particularly interesting approach with a profound anti-inflammatory potential. In previous preclinical studies, we demonstrated that targeting the key molecules C3 or C5 of complement and CD14 of the TLR family had a vast anti-inflammatory effect on Gram-negative bacteria-induced inflammation and sepsis. In this review, we elucidate the significance of these key molecules as important targets for intervention in sepsis and systemic inflammatory response syndrome. Finally, we argue that a combined inhibition of complement and CD14 represent a potential general treatment regimen, beyond the limit of sepsis, including non-infectious systemic inflammation and ischemia reperfusion injury.

Cytomegalovirus and herpes simplex virus effect on the prognosis of mechanically ventilated patients suspected to have ventilator-associated pneumonia

OBJECTIVE

Cytomegalovirus (CMV) and herpes simplex virus (HSV) are common viruses that can affect critically ill patients who are not immunocompromised. The aim of this study was to determine whether the identification of CMV and/or HSV in mechanically ventilated critically ill patients suspected of having pneumonia was associated with an increased mortality.

DESIGN

Prospective epidemiological study.

SETTING

Medical intensive care unit of a tertiary medical center.

PATIENTS

Ninety-three patients with suspected pneumonia.

INTERVENTIONS

Patients with suspected pneumonia had bronchoalveolar lavage and blood samples taken to confirm the diagnosis. Antigenemia was used to detect CMV in the blood. Bronchoalveolar lavage samples were submitted to testing using quantitative real-time Polymerase Chain Reaction.

MEASUREMENTS AND MAIN RESULTS

We identified 22 patients with a CMV infection, 26 patients with an HSV infection and 45 patients without CMV or HSV infection (control group). Mortality at day 60 was higher in patients with a CMV infection than in patients from the control group (55% vs. 20%, P<0.01). Mortality at day 60 was not significantly increased in the group with HSV infection. Duration of ICU stay and ICU mortality were significantly higher in patients with CMV infections when compared to patients from the control group, whereas ventilator free days were significantly lower in patients with CMV infections when compared to patients from the control group.

CONCLUSIONS

In critically ill patients, a CMV infection is associated with an increased mortality. Further interventional studies are needed to evaluate whether treatment could improve the prognosis.

Burden of disease associated with human cytomegalovirus and prospects for elimination by universal immunisation

Cytomegalovirus is the most frequent cause of intrauterine infection and the commonest infectious agent to affect allograft recipients, yet the virus is acknowledged rarely as an occupational hazard for women of childbearing age or as a nosocomial infection. The potential role of cytomegalovirus in hastening the death of patients with AIDS, elderly people, individuals admitted to intensive-care units, and the general population is not emphasised. Development of vaccines against this important human pathogen has been delayed by reluctance to initiate proof-of-concept studies, but after recent trials, protection is a distinct possibility. Cytomegalovirus deserves to be eliminated from selected populations by means of universal immunisation as soon as suitable vaccines become licensed. This action should control disease in neonates and transplant recipients and could provide substantial additional benefits if other disease associations prove to be causal.

The impact of CMV infection on survival in older humans

Dysregulated immunity, 'immunosenescence', in the elderly is thought to contribute to their increased susceptibility to infectious disease and to impact on mortality. Accepted hallmarks of human immunosenescence are low numbers and frequencies of naïve T cells and higher numbers and frequencies of memory T cells in the peripheral blood of the elderly compared to the young. The proportion of the population infected with CMV increases with age and markedly influences these parameters. Infection with this persistent β-herpesvirus may therefore indirectly impact on survival in the elderly. Recent evidence pertaining to this controversial proposal is reviewed here.

Natural and adoptive T-cell immunity against herpes family viruses after allogeneic hematopoietic stem cell transplantation

Reactivated infections with herpes family-related cytomegalovirus, Epstein-Barr virus and varicella zoster virus are serious and sometimes life-threatening complications for patients undergoing allogeneic hematopoietic stem cell transplantation. The pathogenesis of these infections critically involves the slow and inefficient recovery of antiviral T-cell immunity after transplantation. Although efficient drugs to decrease viral load during this vulnerable period have been developed, long-term control of herpes viruses and protection from associated diseases require the sufficient reconstitution of virus-specific memory T cells. To heal the deficiency by immunotherapeutic means, numerous research groups have developed antiviral vaccines and strategies based on the adoptive transfer of virus-specific T cells. This article summarizes the substantial progress made in this field during the past two decades and gives future perspectives about challenges that need to be addressed before antigen-specific immunotherapy against herpes family viruses can be implemented in general clinical practice.

Prolonged recovery from pediatric cardiac surgery due to disseminated cytomegalovirus infection

Partial atrioventricular septal defect is usually followed by an uncomplicated postoperative course. We present an infant with unexplained persistent respiratory failure following partial a trioventricular septal defect repair. Extensive evaluation including bronchoalveolar lavage subsequently led to the diagnosis of disseminated cytomegalovirus. This is the first reported case to our knowledge of disseminated cytomegalovirus following surgical repair of congenital heart disease excluding orthotopic heart transplant.

Immunological insights into the pathogenesis of active CMV infection in non-immunosuppressed critically ill patients

Dissociation of cytomegalovirus (CMV) DNA loads between the lower respiratory tract and blood, with high levels in the former compartment and low or undetectable levels in the latter, commonly occurs during active CMV infection in critically ill patients despite the presence of high frequencies of CMV-specific IFN-γ-producing CD8(+) and CD4(+) T cells in blood. Data presented in this case report suggest that inter-compartmental differences in interleukin-10 (IL-10) levels may, in part, explain the pathobiology of this phenomenon. In the absence of ganciclovir treatment, a significant correlation was observed between IL-10 levels and CMV DNA loads in lower respiratory tract specimens (P = 0.016), but not in plasma samples (P = 0.46). Comparable data were obtained during the course of active CMV infection episodes that developed in six CMV-seropositive critically ill patients with no canonical immunosuppression. The presence of higher levels of IL-10 in the lower respiratory tract than in plasma may result in increased impairment of CMV-specific T-cell effector responses in the lung compared to the systemic compartment, facilitating local CMV replication.

Right place, right time: the evolving role of herpesvirus infection as a "second hit" in idiopathic pulmonary fibrosis

Over the course of the past decade, increasing evidence has implicated alveolar epithelial cell injury and dysfunction in the pathogenesis of idiopathic pulmonary fibrosis (IPF). Genetic factors, cigarette smoking, and other environmental exposures have been identified as potential factors leading to a population of vulnerable alveolar epithelial cells. In addition, molecular techniques have demonstrated herpesviruses are commonly detectable in the lungs of patients with IPF, raising suspicion that, in the setting of a vulnerable alveolar epithelium, lytic (or latent) herpesvirus infection may act as a "second hit" leading to the development of pulmonary fibrosis. Intriguingly, in vivo modeling has shown that herpesvirus infection induces or worsens lung fibrosis when combined with immunodeficiency or other injurious stimuli. Here, we discuss potential mechanisms through which herpesvirus infection may contribute to the pathogenesis of IPF. Ultimately, antiviral therapy may hold promise for halting the progression of this deadly disease.

Cytomegalovirus: pathogen, paradigm, and puzzle

Human cytomegalovirus (CMV), one of the eight herpesviruses that commonly infect humans, is best known for its propensity to cause disease in immunocompromised patients, especially transplant recipients, patients with advanced AIDS, and congenitally infected newborns. Advances in molecular virology coupled with improvements in diagnostic methods and treatment options have vastly improved our understanding of and ability to manage CMV, but many uncertainties remain, including the mechanisms of persistence and pathogenesis and its hypothesized roles in a variety of human illnesses. Here we review recent advances that are reshaping our view and approach to this fascinating virus.