Symptomatic parainfluenza virus infections in children undergoing hematopoietic stem cell transplantation

Outcome of Human Parainfluenza Virus infection in allogeneic stem cell transplantation recipients: possible impact of ribavirin therapy

BACKGROUND

This retrospective study focused on analyzing community-acquired respiratory virus (CARV) infections, in particular human parainfluenza virus (hPIV) after allogeneic stem cell transplant (allo-SCT) in adults recipients. It aimed to assess the impact of ribavirin treatment, clinical characteristics, and risk factors associated with lower respiratory tract disease (LRTD) progression and all-cause mortality.

PATIENTS AND METHODS

The study included 230 allo-SCT recipients diagnosed with hPIV between December 2013 and June 2023. Risk factors for the development of LRTD, disease severity, and mortality were analyzed. Ribavirin treatment was administered at physician discretion in 61 out of 230 cases (27%).

RESULTS

Risk factors for LRTD progression in multivariate analysis were corticosteroids > 30 mg/day (Odds ratio (OR) 3.5, 95% Confidence Interval (C.I.) 1.3-9.4, p = 0.013), fever at the time of hPIV detection (OR 3.89, 95% C.I. 1.84-8.2, p < 0.001), and absolute lymphocyte count (ALC) < 0.2 × 109/L (OR 4.1, 95% C.I. 1.42-11.9, p = 0.009). In addition, the study found that ribavirin therapy significantly reduced progression to LRTD [OR 0.19, 95% C.I. 0.05-0.75, p = 0.018]. Co-infections (OR 5.7, 95% C.I. 1.4-23.5, p = 0.015) and ALC < 0.2 × 109/L (OR 17.7, 95% C.I. 3.6-87.1, p < 0.001) were independently associated with higher day + 100 after hPIV detection all-cause mortality. There were no significant differences in all-cause mortality and infectious mortality at day + 100 between the treated and untreated groups.

CONCLUSION

ALC, corticosteroids, and fever increased the risk for progression to LRTD while ribavirin decreased the risk. However, mortality was associated with ALC and co-infections. This study supports further research of ribavirin therapy for hPIV in the allo-HSCT setting.

ADLM Guidance Document on Laboratory Diagnosis of Respiratory Viruses

Respiratory viral infections are among the most frequent infections experienced worldwide. The COVID-19 pandemic has highlighted the need for testing and currently several tests are available for the detection of a wide range of viruses. These tests vary widely in terms of the number of viral pathogens included, viral markers targeted, regulatory status, and turnaround time to results, as well as their analytical and clinical performance. Given these many variables, selection and interpretation of testing requires thoughtful consideration. The current guidance document is the authors' expert opinion based on the preponderance of available evidence to address key questions related to best practices for laboratory diagnosis of respiratory viral infections including who to test, when to test, and what tests to use. An algorithm is proposed to help laboratories decide on the most appropriate tests to use for the diagnosis of respiratory viral infections.

Pathogenesis of an experimental coinfection of porcine parainfluenza virus 1 and influenza A virus in commercial nursery swine

Porcine parainfluenza virus 1 (PPIV-1) is a recently characterized swine respirovirus. Previous experimental studies reported PPIV-1 replicates in the porcine respiratory tract causing minimal clinical disease or lesions. However, it is unknown if PPIV-1 co-infections with viral respiratory pathogens would cause respiratory disease consistent with natural infections reported in the field. The objective of this study was to evaluate if PPIV-1 increases the severity of influenza A virus respiratory disease in swine. Fifty conventional, five-week-old pigs were assigned to one of three challenge groups (n = 15) or a negative control group (n = 5). Pigs were challenged with a γ-cluster H1N2 influenza A virus in swine (IAV-S; A/Swine/North Carolina/00169/2006), PPIV-1 (USA/MN25890NS/2016), inoculum that contained equivalent titers of IAV-S and PPIV-1 (CO-IN), or negative control. Clinical scores representing respiratory disease and nasal swabs were collected daily and all pigs were necropsied five days post inoculation (DPI). The CO-IN group demonstrated a significantly lower percentage of pigs showing respiratory clinical signs relative to the IAV-S challenge group from 2 to 4 DPI. The IAV-S and CO-IN groups had significantly lower microscopic composite lesion scores in the upper respiratory tract compared to the PPIV-1 group although the IAV-S and CO-IN groups had significantly higher microscopic composite lung lesion scores. Collectively, PPIV-1 did not appear to influence severity of clinical disease, macroscopic lesions, or alter viral loads detected in nasal swabs or necropsy tissues when administered as a coinfection with IAV-S. Studies evaluating PPIV-1 coinfections with different strains of IAV-S, different respiratory pathogens or sequential exposure of PPIV-1 and IAV-S are warranted.

Persistence of RNA Viruses in the Respiratory Tract: An Overview

Respiratory RNA viruses are a major cause of acute lower respiratory tract infections and contribute substantially to hospitalization among infants, elderly, and immunocompromised. Complete viral clearance from acute infections is not always achieved, leading to persistence. Certain chronic respiratory diseases like asthma and chronic obstructive pulmonary disease have been associated with persistent infection by human respiratory syncytial virus and human rhinovirus, but it is still not clear whether RNA viruses really establish long-term infections as it has been recognized for DNA viruses as human bocavirus and adenoviruses. Herein, we summarize evidence of RNA virus persistence in the human respiratory tract, as well as in some animal models, to highlight how long-term infections might be related to development and/or maintenance of chronic respiratory symptoms.

Parainfluenza Virus Types 1-3 Infections Among Children and Adults Hospitalized With Community-acquired Pneumonia

BACKGROUND

Parainfluenza virus (PIV) is a leading cause of lower respiratory tract infections. Although there are several distinct PIV serotypes, few studies have compared the clinical characteristics and severity of infection among the individual PIV serotypes and between PIV and other pathogens in patients with community-acquired pneumonia.

METHODS

We conducted active population-based surveillance for radiographically confirmed community-acquired pneumonia hospitalizations among children and adults in 8 US hospitals with systematic collection of clinical data and respiratory, blood, and serological specimens for pathogen detection. We compared clinical features of PIV-associated pneumonia among individual serotypes 1, 2, and 3 and among all PIV infections with other viral, atypical, and bacterial pneumonias. We also compared in-hospital disease severity among groups employing an ordinal scale (mild, moderate, severe) using multivariable proportional odds regression.

RESULTS

PIV was more commonly detected in children (155/2354; 6.6%) than in adults (66/2297; 2.9%) (P < .001). Other pathogens were commonly co-detected among PIV cases (110/221; 50%). Clinical features of PIV-1, PIV-2, and PIV-3 infections were similar to one another in both children and adults with pneumonia. In multivariable analysis, children with PIV-associated pneumonia exhibited similar severity to children with other nonbacterial pneumonia, whereas children with bacterial pneumonia exhibited increased severity (odds ratio, 8.42; 95% confidence interval, 1.88-37.80). In adults, PIV-associated pneumonia exhibited similar severity to other pneumonia pathogens.

CONCLUSIONS

Clinical features did not distinguish among infection with individual PIV serotypes in patients hospitalized with community-acquired pneumonia. However, in children, PIV pneumonia was less severe than bacterial pneumonia.

Human parainfluenza virus evolution during lung infection of immunocompromised humans promotes viral persistence

The capacity of respiratory viruses to undergo evolution within the respiratory tract raises the possibility of evolution under the selective pressure of the host environment or drug treatment. Long-term infections in immunocompromised hosts are potential drivers of viral evolution and development of infectious variants. We show that intra-host evolution in chronic human parainfluenza virus 3 (HPIV3) infection in immunocompromised individuals elicited mutations that favor viral entry and persistence, suggesting that similar processes may operate across enveloped respiratory viruses. We profiled longitudinal HPIV3 infections from two immunocompromised individuals that persisted for 278 and 98 days. Mutations accrued in the HPIV3 attachment protein hemagglutinin-neuraminidase (HN), including the first in vivo mutation in HN's receptor binding site responsible for activating the viral fusion process. Fixation of this mutation was associated with exposure to a drug that cleaves host cell sialic acid moieties. Longitudinal adaptation of HN was associated with features that promote viral entry and persistence in cells, including greater avidity for sialic acid and more active fusion activity in vitro, but not with antibody escape. Long term infection thus led to mutations promoting viral persistence, suggesting that host-directed therapeutics may support the evolution of viruses that alter their biophysical characteristics to persist in the face of these agents in vivo.

T-Cell Therapeutics Targeting Human Parainfluenza Virus 3 Are Broadly Epitope Specific and Are Cross Reactive With Human Parainfluenza Virus 1

Human Parainfluenza Virus-3 (HPIV3) causes severe respiratory illness in immunocompromised patients and lacks approved anti-viral therapies. A phase I study of adoptively transferred virus-specific T-cells (VSTs) targeting HPIV3 following bone marrow transplantation is underway (NCT03180216). We sought to identify immunodominant epitopes within HPIV3 Matrix protein and their cross-reactivity against related viral proteins. VSTs were generated from peripheral blood of healthy donors by ex-vivo expansion after stimulation with a 15-mer peptide library encompassing HPIV3 matrix protein. Epitope mapping was performed using IFN-γ ELIspot with combinatorial peptide pools. Flow cytometry was used to characterize products with intracellular cytokine staining. In 10 VST products tested, we discovered 12 novel immunodominant epitopes. All products recognized an epitope at the C-terminus. On IFN-γ ELISpot, individual peptides eliciting activity demonstrated mean IFN-γ spot forming units per well (SFU)/1x10⁵ cells of 115.5 (range 24.5-247.5). VST products were polyfunctional, releasing IFN-γ and TNF-α in response to identified epitopes, which were primarily HLA Class II restricted. Peptides from Human Parainfluenza Virus-1 corresponding to the HPIV3 epitopes showed cross-reactivity for HPIV1 in 11 of 12 tested epitopes (mean cross reactivity index: 1.19). Characterization of HPIV3 epitopes may enable development of third-party VSTs to treat immune suppressed patients with HPIV infection.

Hemophilus influenzae and Parainfluenza Virus Pneumonia in a Patient with AIDS

Patient: Male, 64-year-old

Final Diagnosis: Hemophilus influenzae and parainfluenza virus pneumonia in a patient with AIDS

Symptoms: Shortness of breath

Medication:—

Clinical Procedure: Bronchoalveolar lavage

Specialty: Infectious Diseases

Hijacking the Fusion Complex of Human Parainfluenza Virus as an Antiviral Strategy

Paramyxoviruses, including human parainfluenza virus type 3, are internalized into host cells by fusion between viral and target cell membranes. The receptor binding protein, hemagglutinin-neuraminidase (HN), upon binding to its cell receptor, triggers conformational changes in the fusion protein (F). This action of HN activates F to reach its fusion-competent state. Using small molecules that interact with HN, we can induce the premature activation of F and inactivate the virus. To obtain highly active pretriggering compounds, we carried out a virtual modeling screen for molecules that interact with a sialic acid binding site on HN that we propose to be the site involved in activating F. We use cryo-electron tomography of authentic intact viral particles for the first time to directly assess the mechanism of action of this treatment on the conformation of the viral F protein and present the first direct observation of the induced conformational rearrangement in the viral F protein.

The receptor binding protein of parainfluenza virus, hemagglutinin-neuraminidase (HN), is responsible for actively triggering the viral fusion protein (F) to undergo a conformational change leading to insertion into the target cell and fusion of the virus with the target cell membrane. For proper viral entry to occur, this process must occur when HN is engaged with host cell receptors at the cell surface. It is possible to interfere with this process through premature activation of the F protein, distant from the target cell receptor. Conformational changes in the F protein and adoption of the postfusion form of the protein prior to receptor engagement of HN at the host cell membrane inactivate the virus. We previously identified small molecules that interact with HN and induce it to activate F in an untimely fashion, validating a new antiviral strategy. To obtain highly active pretriggering candidate molecules we carried out a virtual modeling screen for molecules that interact with sialic acid binding site II on HN, which we propose to be the site responsible for activating F. To directly assess the mechanism of action of one such highly effective new premature activating compound, PAC-3066, we use cryo-electron tomography on authentic intact viral particles for the first time to examine the effects of PAC-3066 treatment on the conformation of the viral F protein. We present the first direct observation of the conformational rearrangement induced in the viral F protein.

Possible role of highly activated mucosal NK cells against viral respiratory infections in children undergoing haematopoietic stem cell transplantation

Infection is the leading cause of non-relapse-related mortality after allogeneic haematopoietic stem cell transplantation (HSCT). Altered functions of immune cells in nasal secretions may influence post HSCT susceptibility to viral respiratory infections. In this prospective study, we determined T and NK cell numbers together with NK activation status in nasopharyngeal aspirates (NPA) in HSCT recipients and healthy controls using multiparametric flow cytometry. We also determined by polymerase chain reaction (PCR) the presence of 16 respiratory viruses. Samples were collected pre-HSCT, at day 0, +10, +20 and +30 after HSCT. Peripheral blood (PB) was also analyzed to determine T and NK cell numbers. A total of 27 pediatric HSCT recipients were enrolled and 16 of them had at least one viral detection (60%). Rhinovirus was the most frequent pathogen (84% of positive NPAs). NPAs of patients contained fewer T and NK cells compared to healthy controls (p = 0.0132 and p = 0.120, respectively). Viral PCR + patients showed higher NK cell number in their NPAs. The activating receptors repertoire expressed by NK cells was also higher in NPA samples, especially NKp44 and NKp46. Our study supports NK cells relevance for the immune defense against respiratory viruses in HSCT recipients.

Are Community Acquired Respiratory Viral Infections an Underestimated Burden in Hematology Patients?

Despite a plethora of studies demonstrating significant morbidity and mortality due to community-acquired respiratory viral (CRV) infections in intensively treated hematology patients, and despite the availability of evidence-based guidelines for the diagnosis and management of respiratory viral infections in this setting, there is no uniform inclusion of respiratory viral infection management in the clinical hematology routine. Nevertheless, timely diagnosis and systematic management of CRV infections in intensively treated hematology patients has a demonstrated potential to significantly improve outcome. We have briefly summarized the recently published data on CRV infection epidemiology, as well as guidelines on the diagnosis and management of CRV infections in patients intensively treated for hematological malignancies. We have also assessed available treatment options, as well as mentioned novel agents currently in development.

Delaying haematopoietic stem cell transplantation in children with viral respiratory infections reduces transplant-related mortality

Viral respiratory infections (VRIs) contribute to the morbidity and transplant‐related mortality (TRM) after allogeneic haematopoietic stem cell transplantation (HSCT) and strategies to prevent and treat VRIs are warranted. We monitored VRIs before and after transplant in children undergoing allogeneic HSCT with nasopharyngeal aspirates (NPA) and assessed the impact on clinical outcome. Between 2007 and 2017, 585 children underwent 620 allogeneic HSCT procedures. Out of 75 patients with a positive NPA screen (12%), transplant was delayed in 25 cases (33%), while 53 children started conditioning with a VRI. Patients undergoing HSCT with a positive NPA screen had a significantly lower overall survival (54% vs. 79%) and increased TRM (26% vs. 7%) compared to patients with a negative NPA. Patients with a positive NPA who delayed transplant and cleared the virus before conditioning had improved overall survival (90%) and lower TRM (5%). Pre‐HSCT positive NPA was the only significant risk factor for progression to a lower respiratory tract infection and was a major risk factor for TRM. Transplant delay, whenever feasible, in case of a positive NPA screen for VRIs can positively impact on survival of children undergoing HSCT.

Respiratory Virus Infections in Hematopoietic Cell Transplant Recipients

Highly immunocompromised pediatric and adult hematopoietic cell transplant (HCT) recipients frequently experience respiratory infections caused by viruses that are less virulent in immunocompetent individuals. Most of these infections, with the exception of rhinovirus as well as adenovirus and parainfluenza virus in tropical areas, are seasonal variable and occur before and after HCT. Infectious disease management includes sampling of respiratory specimens from nasopharyngeal washes or swabs as well as sputum and tracheal or tracheobronchial lavages. These are subjected to improved diagnostic tools including multiplex PCR assays that are routinely used allowing for expedient detection of all respiratory viruses. Disease progression along with high mortality is frequently associated with respiratory syncytial virus, parainfluenza virus, influenza virus, and metapneumovirus infections. In this review, we discuss clinical findings and the appropriate use of diagnostic measures. Additionally, we also discuss treatment options and suggest new drug formulations that might prove useful in treating respiratory viral infections. Finally, we shed light on the role of the state of immune reconstitution and on the use of immunosuppressive drugs on the outcome of infection.

Risk Factors for Parainfluenza Virus Lower Respiratory Tract Disease after Hematopoietic Cell Transplantation

Parainfluenza virus (PIV) infection can progress from upper respiratory tract infection (URTI) to lower respiratory tract disease (LRTD) in immunocompromised hosts. Risk factors for progression to LRTD and presentation with LRTD without prior URTI are poorly defined. Hematopoietic cell transplant (HCT) recipients with PIV infection were retrospectively analyzed using standardized definitions of LRTD. PIV was detected in 540 HCT recipients; 343 had URTI alone and 197 (36%) had LRTD (possible, 76; probable, 19; proven, 102). Among 476 patients with positive nasopharyngeal samples, the cumulative incidence of progression to probable/proven LRTD by day 40 was 12%, with a median time to progression of 7 days (range, 2 to 40). In multivariable analysis monocytopenia (hazard ratio, 2.22; P = .011), steroid use ≥1mg/kg prior to diagnosis (hazard ratio, 1.89; P = .018), co-pathogen detection in blood (hazard ratio, 3.21; P = .027), and PIV type 3 (hazard ratio, 3.57; P = .032) were associated with increased progression risk. In the absence of all 4 risk factors no patients progressed to LRTD, whereas progression risk increased to >30% if 3 or more risk factors were present. Viral load or ribavirin use appeared to have no effect on progression. Among 121 patients with probable/proven LRTD, 64 (53%) presented LRTD without prior URTI, and decreased lung function before infection and lower respiratory co-pathogens were risk factors for this presentation. Mortality was unaffected by the absence of prior URTI. We conclude that the risk of progression to probable/proven LRTD exceeded 30% with ≥3 risk factors. To detect all cases of LRTD, virologic testing of lower respiratory samples is required regardless of URTI symptoms.

Respiratory Viral Infections in Patients With Cancer or Undergoing Hematopoietic Cell Transplant

Survival rates for pediatric cancer have steadily improved over time but it remains a significant cause of morbidity and mortality among children. Infections are a major complication of cancer and its treatment. Community acquired respiratory viral infections (CRV) in these patients increase morbidity, mortality and can lead to delay in chemotherapy. These are the result of infections with a heterogeneous group of viruses including RNA viruses, such as respiratory syncytial virus (RSV), influenza virus (IV), parainfluenza virus (PIV), metapneumovirus (HMPV), rhinovirus (RhV), and coronavirus (CoV). These infections maintain a similar seasonal pattern to those of immunocompetent patients. Clinical manifestations vary significantly depending on the type of virus and the type and degree of immunosuppression, ranging from asymptomatic or mild disease to rapidly progressive fatal pneumonia Infections in this population are characterized by a high rate of progression from upper to lower respiratory tract infection and prolonged viral shedding. Use of corticosteroids and immunosuppressive therapy are risk factors for severe disease. The clinical course is often difficult to predict, and clinical signs are unreliable. Accurate prognostic viral and immune markers, which have become part of the standard of care for systemic viral infections, are currently lacking; and management of CRV infections remains controversial. Defining effective prophylactic and therapeutic strategies is challenging, especially considering, the spectrum of immunocompromised patients, the variety of respiratory viruses, and the presence of other opportunistic infections and medical problems. Prevention remains one of the most important strategies against these viruses. Early diagnosis, supportive care and antivirals at an early stage, when available and indicated, have proven beneficial. However, with the exception of neuraminidase inhibitors for influenza infection, there are no accepted treatments. In high-risk patients, pre-emptive treatment with antivirals for upper respiratory tract infection (URTI) to decrease progression to LRTI is a common strategy. In the future, viral load and immune markers may prove beneficial in predicting severe disease, supporting decision making and monitor treatment in this population.

A Multicenter Consortium to Define the Epidemiology and Outcomes of Inpatient Respiratory Viral Infections in Pediatric Hematopoietic Stem Cell Transplant Recipients

BACKGROUND

Respiratory virus infections (RVIs) pose a threat to children undergoing hematopoietic stem cell transplantation (HSCT). In this era of sensitive molecular diagnostics, the incidence and outcome of HSCT recipients who are hospitalized with RVI (H-RVI) are not well described.

METHODS

A retrospective observational cohort of pediatric HSCT recipients (between January 2010 and June 2013) was assembled from 9 US pediatric transplant centers. Their medical charts were reviewed for H-RVI events within 1 year after their transplant. An H-RVI diagnosis required respiratory signs or symptoms plus viral detection (human rhinovirus/enterovirus, human metapneumovirus, influenza, parainfluenza, coronaviruses, and/or respiratory syncytial virus). The incidence of H-RVI was calculated, and the association of baseline HSCT factors with subsequent pulmonary complications and death was assessed.

RESULTS

Among 1560 HSCT recipients, 259 (16.6%) acquired at least 1 H-RVI within 1 year after their transplant. The median age of the patients with an H-RVI was lower than that of patients without an H-RVI (4.8 vs 7.1 years; P < .001). Among the patients with a first H-RVI, 48% required some respiratory support, and 14% suffered significant pulmonary sequelae. The all-cause and attributable case-fatality rates within 3 months of H-RVI onset were 11% and 5.4%, respectively. Multivariate logistic regression revealed that H-RVI onset within 60 days of HSCT, steroid use in the 7 days before H-RVI onset, and the need for respiratory support at H-RVI onset were associated with subsequent morbidity or death.

CONCLUSION

Results of this multicenter cohort study suggest that H-RVIs are relatively common in pediatric HSCT recipients and contribute to significant morbidity and death. These data should help inform interventional studies specific to each viral pathogen.

Viral Respiratory Tract Infections in Allogeneic Hematopoietic Stem Cell Transplantation Recipients in the Era of Molecular Testing

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Rhinovirus caused the majority of vRTI episodes in first 100 days following transplantation.

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Progression to lower respiratory tract infection was seen in 30% of patients with vRTI.

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vRTI in first 100 days after transplantation is associated with morbidity (ie, ICU admission).

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All of the deaths in our study cohort occurred in patients who acquired vRTI within 30 days of transplantation.

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Previous autologous transplantation is a significant risk factor for vRTI.

Viral respiratory tract infection (vRTI) is a significant cause of morbidity and mortality in patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). This study aimed to assess the epidemiologic characteristics, risk factors, and outcomes of vRTI occurring in the period from conditioning to 100 days after allo-HSCT in the era of molecular testing. This study was a retrospective record review of patients who underwent allo-HSCT at Royal Melbourne Hospital between January 2010 and December 2015. Symptomatic patients were tested using respiratory multiplex polymerase chain reaction (PCR). Logistic regression and Kaplan-Meier analysis were used to identify risk factors for vRTI and the risk of death or intensive care unit (ICU) admission, respectively. A total of 382 patients were reviewed, and 65 episodes of vRTI were identified in 56 patients (14.7%). Rhinovirus accounted for the majority of infections (69.2%). The majority of episodes presented initially with upper respiratory tract infection (58.5%), with 28.9% of them progressing to lower respiratory tract infection. Eleven episodes (16.9%) were associated with ICU admission. There were no deaths directly due to vRTI. Previous autologous HSCT was associated with an increased risk of vRTI (odds ratio, 2.1; 95% confidence interval, 1.0 to 4.1). The risks of death (P = .47) or ICU admission (P = .65) were not significantly different by vRTI status. vRTI is common in the first 100 days after allo-HSCT and is associated with ICU admission.

Dynamics of Sendai Virus Spread, Clearance, and Immunotherapeutic Efficacy after Hematopoietic Cell Transplant Imaged Noninvasively in Mice

There are no approved vaccines or virus-specific treatments for human parainfluenza viruses (HPIVs), which have recently been reclassified into the species Human respirovirus 1, Human respirovirus 3, Human rubulavirus 2, and Human rubulavirus 4 These viruses cause morbidity and mortality in immunocompromised patients, including those undergoing hematopoietic cell transplant (HCT). No small-animal models for noninvasive imaging of respiratory virus infection in the HCT host exist, despite the utility that such a system would offer to monitor prolonged infection, its clearance, and treatment options. We used a luciferase-expressing reporter virus to noninvasively image in mice the infection of murine respirovirus (strain Sendai virus [SeV]), the murine counterpart of HPIV1. Independent of disease severity, the clearance of infection began approximately 21 days after HCT, largely due to the recovery of CD8+ T cells. Immunotherapy with granulocyte colony-stimulating factor (G-CSF) and adoptive transfer of natural killer (NK) cells provided a limited therapeutic benefit. Treatment with a fusion (F) protein-specific monoclonal antibody arrested the spread of lung infection and reduced the disease severity even when treatment was delayed to up to 10 days postinfection but had little observable effect on upper respiratory tract infection. Adoptive transfer of virus-specific T cells at 10 days postinfection accelerated the clearance by 5 days, reduced the extent of infection throughout the respiratory tract, and reduced the disease severity. Overall, the results support investigation of the clinical treatment of respiratory virus infection in the HCT host with monoclonal antibodies and adoptive T-cell transfer; the imaging system should be extendable to other respiratory viruses, such as respiratory syncytial virus and influenza virus.IMPORTANCE Parainfluenza viruses are a major cause of disease and death due to respiratory virus infection in the immunocompromised host, including those undergoing bone marrow transplantation. There are currently no effective treatment measures. We noninvasively imaged mice that were undergoing a bone marrow transplant and infected with Sendai virus, a murine parainfluenza virus (respirovirus). For the first time, we show the therapeutic windows of adoptive T-cell therapy and treatment with a monoclonal antibody to the fusion (F) protein in clearing Sendai virus from the respiratory tract and reducing disease severity. Mice tolerated these treatments without any detectable toxicity. These findings pave the way for studies assessing the safety of T-cell therapy against parainfluenza virus in humans. Adoptive T-cell therapy against other blood-borne viruses in humans has been shown to be safe and effective. Our model of noninvasive imaging in mice that had undergone a bone marrow transplant may be well suited to track other respiratory virus infections and develop novel preventive and therapeutic strategies.

Human Parainfluenza Virus Type 3 Infections in Patients with Hematopoietic Stem Cell Transplants: the Mode of Nosocomial Infections and Prognosis

There have been a few prospective and comprehensive surveillance studies on the respiratory viral infections (RVIs) among patients undergoing hematopoietic stem cell transplantation (HSCT). A 2-year prospective cohort surveillance study of symptomatic and asymptomatic RVIs was performed in hospitalized HSCT patients. Oropharyngeal (OP) swab samples were serially collected each week from 1 week before and up to 100 days after HSCT and were tested for virus isolation with cell culture-based viral isolation (CC-based VI) and a multiplex PCR (MPCR). A total of 2,747 OP swab samples were collected from 250 HSCT patients (268 HSCT procedures). Among these patients, 79 had RVIs (CC-based VI, n = 63; MPCR, n = 17). The parainfluenza virus type 3 (PIV3) accounted for 71% (57/80) of the cases of RVIs. Some PIV3 infections were asymptomatic and involved a longer virus-shedding period. The PIV3 was often cultured from samples taken before the onset of a respiratory disease. The PIV3 infections were attributed to the transmission of nosocomial infections. PIV3 infections before engraftment will more likely result in the development of lower respiratory tract infections and worse outcomes. A real-time monitoring of respiratory viral infections in the HSCT ward among patients with or without respiratory symptoms is required for the prevention of nosocomial RVIs, especially of PIV3 infections.

Non-invasive Imaging of Sendai Virus Infection in Pharmacologically Immunocompromised Mice: NK and T Cells, but not Neutrophils, Promote Viral Clearance after Therapy with Cyclophosphamide and Dexamethasone

In immunocompromised patients, parainfluenza virus (PIV) infections have an increased potential to spread to the lower respiratory tract (LRT), resulting in increased morbidity and mortality. Understanding the immunologic defects that facilitate viral spread to the LRT will help in developing better management protocols. In this study, we immunosuppressed mice with dexamethasone and/or cyclophosphamide then monitored the spread of viral infection into the LRT by using a noninvasive bioluminescence imaging system and a reporter Sendai virus (murine PIV type 1). Our results show that immunosuppression led to delayed viral clearance and increased viral loads in the lungs. After cessation of cyclophosphamide treatment, viral clearance occurred before the generation of Sendai-specific antibody responses and coincided with rebounds in neutrophils, T lymphocytes, and natural killer (NK) cells. Neutrophil suppression using anti-Ly6G antibody had no effect on infection clearance, NK-cell suppression using anti-NK antibody delayed clearance, and T-cell suppression using anti-CD3 antibody resulted in no clearance (chronic infection). Therapeutic use of hematopoietic growth factors G-CSF and GM-CSF had no effect on clearance of infection. In contrast, treatment with Sendai virus-specific polysera or a monoclonal antibody limited viral spread into the lungs and accelerated clearance. Overall, noninvasive bioluminescence was shown to be a useful tool to study respiratory viral progression, revealing roles for NK and T cells, but not neutrophils, in Sendai virus clearance after treatment with dexamethasone and cyclophosphamide. Virus-specific antibodies appear to have therapeutic potential.

Parainfluenza Virus Infection

Human parainfluenza viruses (HPIVs) are single-stranded, enveloped RNA viruses of the Paramyoviridaie family. There are four serotypes which cause respiratory illnesses in children and adults. HPIVs bind and replicate in the ciliated epithelial cells of the upper and lower respiratory tract and the extent of the infection correlates with the location involved. Seasonal HPIV epidemics result in a significant burden of disease in children and account for 40% of pediatric hospitalizations for lower respiratory tract illnesses (LRTIs) and 75% of croup cases. Parainfluenza viruses are associated with a wide spectrum of illnesses which include otitis media, pharyngitis, conjunctivitis, croup, tracheobronchitis, and pneumonia. Uncommon respiratory manifestations include apnea, bradycardia, parotitis, and respiratory distress syndrome and rarely disseminated infection. Immunity resulting from disease in childhood is incomplete and reinfection with HPIV accounts for 15% of respiratory illnesses in adults. Severe disease and fatal pneumonia may occur in elderly and immunocompromised adults. HPIV pneumonia in recipients of hematopoietic stem cell transplant (HSCT) is associated with 50% acute mortality and 75% mortality at 6 months. Though sensitive molecular diagnostics are available to rapidly diagnose HPIV infection, effective antiviral therapies are not available. Currently, treatment for HPIV infection is supportive with the exception of croup where the use of corticosteroids has been found to be beneficial. Several novel drugs including DAS181 appear promising in efforts to treat severe disease in immunocompromised patients, and vaccines to decrease the burden of disease in young children are in development.

Sendai virus as a backbone for vaccines against RSV and other human paramyxoviruses

Human paramyxoviruses are the etiological agents for life-threatening respiratory virus infections of infants and young children. These viruses, including respiratory syncytial virus (RSV), the human parainfluenza viruses (hPIV1-4) and human metapneumovirus (hMPV), are responsible for millions of serious lower respiratory tract infections each year worldwide. There are currently no standard treatments and no licensed vaccines for any of these pathogens. Here we review research with which Sendai virus, a mouse parainfluenza virus type 1, is being advanced as a Jennerian vaccine for hPIV1 and as a backbone for RSV, hMPV and other hPIV vaccines for children.

Parainfluenza virus infections in hematopoietic cell transplant recipients and hematologic malignancy patients: A systematic review

Parainfluenza viral infections are increasingly recognized as common causes of morbidity and mortality in cancer patients, particularly in hematopoietic cell transplant (HCT) recipients and hematologic malignancy (HM) patients because of their immunocompromised status and susceptibility to lower respiratory tract infections. Advances in diagnostic methods, including polymerase chain reaction, have led to increased identification and awareness of these infections. Lack of consensus on clinically significant endpoints and the small number of patients affected in each cancer institution every year make it difficult to assess the efficacy of new or available antiviral drugs. In this systematic review, we summarized data from all published studies on parainfluenza virus infections in HM patients and HCT recipients, focusing on incidence, risk factors, long-term outcomes, mortality, prevention, and management with available or new investigational agents. Vaccines against these viruses are lacking; thus, infection control measures remain the mainstay for preventing nosocomial spread. A multi-institutional collaborative effort is recommended to standardize and validate clinical endpoints for PIV infections, which will be essential for determining efficacy of future vaccine and antiviral therapies.

Human rhinovirus C infections in pediatric hematology and oncology patients

Children with cancer and HSCT recipients are at high risk for common viral infections. We sought to define the viral etiology of ARI and identify risk factors. Nasal wash samples were collected from pediatric hematology-oncology patients and HSCT recipients with ARI during the 2003-2005 winter seasons. Real-time RT-PCR was performed to detect Flu A, influenza B, RSV, PIV 1-3, human MPV, and HRV. HRV specimens were sequenced and genotyped. Seventy-eight samples from 62 children were included. Viruses were detected in 31 of 78 samples (40%). HRV were detected most frequently, in 16 (52%) including five HRVC; followed by seven (22%) RSV, five (16%) Flu A, four (13%) MPV, and two (6%) PIV2. There was a trend toward higher risk of viral infection for children in day care. Only 8% of the study children had received influenza vaccine. HRV, including the recently discovered HRVC, are an important cause of infection in pediatric oncology and HSCT patients. Molecular testing is superior to conventional methods and should be standard of care, as HRV are not detected by conventional methods.

Circulating clinical strains of human parainfluenza virus reveal viral entry requirements for in vivo infection

Human parainfluenza viruses (HPIVs) cause widespread respiratory infections, with no vaccines or effective treatments. We show that the molecular determinants for HPIV3 growth in vitro are fundamentally different from those required in vivo and that these differences impact inhibitor susceptibility. HPIV infects its target cells by coordinated action of the hemagglutinin-neuraminidase receptor-binding protein (HN) and the fusion envelope glycoprotein (F), which together comprise the molecular fusion machinery; upon receptor engagement by HN, the prefusion F undergoes a structural transition, extending and inserting into the target cell membrane and then refolding into a postfusion structure that fuses the viral and cell membranes. Peptides derived from key regions of F can potently inhibit HPIV infection at the entry stage, by interfering with the structural transition of F. We show that clinically circulating viruses have fusion machinery that is more stable and less readily activated than viruses adapted to growth in culture. Fusion machinery that is advantageous for growth in human airway epithelia and in vivo confers susceptibility to peptide fusion inhibitors in the host lung tissue or animal, but the same fusion inhibitors have no effect on viruses whose fusion glycoproteins are suited for growth in vitro. We propose that for potential clinical efficacy, antivirals should be evaluated using clinical isolates in natural host tissue rather than lab strains of virus in cultured cells. The unique susceptibility of clinical strains in human tissues reflects viral inhibition in vivo.

IMPORTANCE

Acute respiratory infection is the leading cause of mortality in young children under 5 years of age, causing nearly 20% of childhood deaths worldwide each year. The paramyxoviruses, including human parainfluenza viruses (HPIVs), cause a large share of these illnesses. There are no vaccines or drugs for the HPIVs. Inhibiting entry of viruses into the human cell is a promising drug strategy that blocks the first step in infection. To develop antivirals that inhibit entry, it is critical to understand the first steps of infection. We found that clinical viruses isolated from patients have very different entry properties from those of the viruses generally studied in laboratories. The viral entry mechanism is less active and more sensitive to fusion inhibitory molecules. We propose that to interfere with viral infection, we test clinically circulating viruses in natural tissues, to develop antivirals against respiratory disease caused by HPIVs.

Parainfluenza virus type 3 Ab in allogeneic hematopoietic cell transplant recipients: factors influencing post-transplant Ab titers and associated outcomes

Parainfluenza virus type 3 (PIV-3) can cause severe respiratory illness among hematopoietic cell transplantation (HCT) recipients. Factors associated with PIV-3-specific Ab level, and the association between PIV-3 Ab levels and clinical outcomes in HCT recipients who acquire PIV-3 infection, are unknown. We evaluated PIV-3-specific hemagglutination inhibition Ab levels and clinical outcomes among 172 patients with PIV-3 infection following HCT. In a multivariable linear regression model, high post-transplantation Ab levels were independently associated with higher pre-transplantation recipient titer (mean difference 0.38 (95% confidence interval (CI), 0.26, 0.50), P<0.001). Significant associations between pre-HCT Ab titers in both patients and donors and occurrence of lower respiratory tract disease (LRD) after HCT were not observed. In conclusion, low pre-transplantation titers are associated with low Ab levels after HCT. The relationship between PIV-3 Ab levels and outcomes remain uncertain. Further study is needed to prospectively evaluate the dynamics of PIV-3-specific Ab responses and the relative contribution of PIV-3-specific Ab to protection from infection acquisition and progression to LRD.

The FilmArray® respiratory panel: an automated, broadly multiplexed molecular test for the rapid and accurate detection of respiratory pathogens

The FilmArray Respiratory Panel (RP) (BioFire(™) Diagnostics, Inc., Salt Lake City, UT, USA) is the first multiplex molecular panel cleared by the US FDA for the detection of both bacterial and viral respiratory pathogens in nasopharygeal swabs. The FilmArray RP targets 20 pathogens including 17 viruses and subtypes and three bacteria, and is performed with minimal sample manipulation. The FilmArray RP has a fully automated sample-to-answer workflow with a turn-around-time of approximately 1 h. The reported sensitivity and specificity of the assay ranges from 80 to 100 and 100%, respectively, with the sensitivity for the adenovirus as low as 46%. A new version of the FilmArray RP assay (version 1.7) with improved sensitivity for the adenovirus was released in 2013. The performance characteristics and simplified workflow have allowed its implementation in a wide range of laboratories. The FilmArray RP has changed the diagnostic landscape and will have a significant impact on the care of patients with respiratory tract infection.

Parainfluenza virus lower respiratory tract disease after hematopoietic cell transplant: viral detection in the lung predicts outcome

BACKGROUND

Parainfluenza virus (PIV) commonly infects patients following hematopoietic cell transplantation (HCT), frequently causing lower respiratory tract disease (LRTD). The definition of LRTD significantly differs among studies evaluating the impact of PIV after HCT.

METHODS

We retrospectively evaluated 544 HCT recipients with laboratory-confirmed PIV and classified LRTD into 3 groups: possible (PIV detection in upper respiratory tract with new pulmonary infiltrates with/without LRTD symptoms), probable (PIV detection in lung with LRTD symptoms without new pulmonary infiltrates), and proven (PIV detection in lung with new pulmonary infiltrates with/without LRTD symptoms).

RESULTS

Probabilities of 90-day survival after LRTD were 87%, 58%, and 45% in possible, probable, and proven cases, respectively. Patients with probable and proven LRTD had significantly worse survival than those with upper respiratory tract infection (probable: hazard ratio [HR], 5.87 [P < .001]; proven: HR, 9.23 [P < .001]), whereas possible LRTD did not (HR, 1.49 [P = .27]). Among proven/probable cases, oxygen requirement at diagnosis, low monocyte counts, and high-dose steroid use (>2 mg/kg/day) were associated with high mortality in multivariable analysis.

CONCLUSIONS

PIV LRTD with viral detection in lungs (proven/probable LRTD) was associated with worse outcomes than was PIV LRTD with viral detection in upper respiratory samples alone (possible LRTD). This new classification should impact clinical trial design and permit comparability of results among centers.

The impact of RSV, adenovirus, influenza, and parainfluenza infection in pediatric patients receiving stem cell transplant, solid organ transplant, or cancer chemotherapy

RVIs are a significant cause of morbidity and mortality in immunocompromised children. We analyzed the characteristics and outcomes of infection by four respiratory viruses (RSV, adenovirus, influenza, and parainfluenza) treated at a pediatric tertiary care hospital in a retrospective cohort of patients who had received cancer chemotherapy, hematopoietic stem cell, or SOT. A total of 208 infections were studied among 166 unique patients over a time period of 1993-2006 for transplant recipients, and 2000-2005 for patients with cancer. RSV was the most common respiratory virus identified. There were 17 (10% of all patients) deaths overall, of which 12 were at least partly attributed to the presence of a RVI. In multivariate models, LRT symptoms in the absence of upper respiratory symptoms on presentation (OR 10.2 [2.3, 45.7], p = 0.002) and adenoviral infection (OR 3.7 [1.1, 12.6], p = 0.034) were significantly associated with poor outcome, defined as death or disability related to RVI. All of the deaths occurred in patients who had received either solid organ or HSCT. There were no infections resulting in death or disability in the cancer chemotherapy group.

Prospective detection of respiratory pathogens in symptomatic children with cancer

BACKGROUND

: The data on human rhinovirus, coronavirus, bocavirus, metapneumovirus, Chlamydophila pneumoniae, Mycoplasma pneumoniae and Bordetella pertussis infections in children with cancer is limited.

METHODS

: We sought to determine prospectively the prevalence of respiratory pathogens in these children, using multiplexed-polymerase chain reaction.

RESULTS

: We enrolled 253 children with upper or lower respiratory tract infection (LRTI) during a 1-year period. A respiratory virus was detected in 193 (76%) patients; 156 (81%) patients had upper respiratory tract infection. Human rhinovirus was the most common virus detected in 97 (62%) and 24 (65%) patients with upper respiratory tract infection and LRTI, respectively. Leukemia or lymphoma was the most common underlying diagnosis in 95 (49%) patients followed by solid tumor 47 (24%), posthematopoietic stem cell transplant 28 (15%) and brain tumor in 23 (12%) patients. By multiple logistic regression analysis, human bocavirus was the most commonly detected respiratory virus in patients with LRTI (P = 0.008; odds ratio, 4.52; 95% confidence interval: 1.48-13.79). Coinfection with >1 virus was present in 47 (24%) patients, and did not increase the risk for LRTI. Two (0.7%) patients succumbed to LRTI from parainfluenza virus-3 and respiratory syncytial virus/human rhinovirus infection, respectively. C. pneumoniae and M. pneumoniae were detected in 4 and 3 patients, respectively.

CONCLUSIONS

: Human rhinovirus was the most common virus detected in children with cancer and posthematopoietic stem cell transplant hospitalized with an acute respiratory illness, and was not associated with increased morbidity. Prospective studies with viral load determination and asymptomatic controls are needed to study the association of these emerging respiratory viruses with LRTI in children with cancer and posthematopoietic stem cell transplant.

Human parainfluenza virus serotypes differ in their kinetics of replication and cytokine secretion in human tracheobronchial airway epithelium

Human parainfluenza viruses (PIVs) cause acute respiratory illness in children, the elderly, and immunocompromised patients. PIV3 is a common cause of bronchiolitis and pneumonia, whereas PIV1 and 2 are frequent causes of upper respiratory tract illness and croup. To assess how PIV1, 2, and 3 differ with regard to replication and induction of type I interferons, interleukin-6, and relevant chemokines, we infected primary human airway epithelium (HAE) cultures from the same tissue donors and examined replication kinetics and cytokine secretion. PIV1 replicated to high titer yet did not induce cytokine secretion until late in infection, while PIV2 replicated less efficiently but induced an early cytokine peak. PIV3 replicated to high titer but induced a slower rise in cytokine secretion. The T cell chemoattractants CXCL10 and CXCL11 were the most abundant chemokines induced. Differences in replication and cytokine secretion might explain some of the differences in PIV serotype-specific pathogenesis and epidemiology.

Respiratory viral infections in pediatric solid organ and hematopoietic stem cell transplantation

Respiratory viruses are common in children, including pediatric recipients of both solid organ transplantation and hematopoietic stem cell transplantation. The prevalence and risk factors in each of these groups are reviewed. Furthermore, associated morbidity and mortality in pediatric transplant recipients with respiratory viral infections are addressed. The literature on specific prevention and treatment options for respiratory syncytial virus, adenovirus, influenza, and other respiratory viruses in pediatric solid organ and hematopoietic stem cell transplant recipients is reported.

Fourth European Conference on Infections in Leukaemia (ECIL-4): guidelines for diagnosis and treatment of human respiratory syncytial virus, parainfluenza virus, metapneumovirus, rhinovirus, and coronavirus

Community-acquired respiratory virus (CARV) infections have been recognized as a significant cause of morbidity and mortality in patients with leukemia and those undergoing hematopoietic stem cell transplantation (HSCT). Progression to lower respiratory tract infection with clinical and radiological signs of pneumonia and respiratory failure appears to depend on the intrinsic virulence of the specific CARV as well as factors specific to the patient, the underlying disease, and its treatment. To better define the current state of knowledge of CARVs in leukemia and HSCT patients, and to improve CARV diagnosis and management, a working group of the Fourth European Conference on Infections in Leukaemia (ECIL-4) 2011 reviewed the literature on CARVs, graded the available quality of evidence, and made recommendations according to the Infectious Diseases Society of America grading system. Owing to differences in screening, clinical presentation, and therapy for influenza and adenovirus, ECIL-4 recommendations are summarized for CARVs other than influenza and adenovirus.

Timeline, epidemiology, and risk factors for bacterial, fungal, and viral infections in children and adolescents after allogeneic hematopoietic stem cell transplantation

Advances made in the field of hematopoietic stem cell transplantations (HSCT) over the past 20 years may have had an impact on the distribution of posttransplantation infections. We sought to retrospectively analyze the epidemiology and risk factors for bacterial, fungal, and viral infections in children after allogeneic HSCT in a cohort of 759 children who underwent allogeneic HSCT in a single institution between 1990 and 2009. The association between infections and risk factors of interest at 0 to 30 days, 31 to 100 days, and 101 days to 2 years posttransplantation was evaluated using logistic regression. Difference among the subtypes within each category was studied. There were 243 matched-related donors, 239 matched-unrelated donors (MUDs), and 176 haploidentical donor transplantations. Era of transplantation (0-30 days), peripheral blood stem cell product, acute graft-versus-host disease (aGVHD; 31-100 days), and chronic GVHD (cGVHD; 101-730 days) were associated with higher risk for bacterial infections at the respective time periods. Patients with aGVHD (31-100 days), cGVHD, and older age (101-730 days) were at higher risk for fungal infections. Cytomegalovirus (CMV) donor/recipient (D/R) serostatus (0-100 days), era of transplantation, MUD HSCT (31-100 days), and cGVHD (101-730 days), influenced viral infections. Gram-positive outnumbered gram-negative bacterial infections; aspergillosis and candidemia were equally prevalent in all time periods. Haploidentical donor HSCT was not associated with an increased risk of infections. There seems to be a continuum in the timeline of infections posttransplantation, with bacterial, fungal, and viral infections prevalent in all time periods, particularly late after the transplantation, the risk affected by GVHD, CMV, D/R status, product type, older age, and use of unrelated donors.

Adaptation of human parainfluenza virus to airway epithelium reveals fusion properties required for growth in host tissue

Paramyxoviruses, a family of RNA enveloped viruses that includes human parainfluenza virus type 3 (HPIV3), cause the majority of childhood croup, bronchiolitis, and pneumonia worldwide. Infection starts with host cell receptor binding and fusion of the viral envelope with the cell membrane at the cell surface. The fusion process requires interaction of the two viral surface glycoproteins, the hemagglutinin-neuraminidase (HN) and the fusion protein (F). We have previously shown that viruses with an HN/F pair that is highly fusogenic in monolayers of immortalized cells due to mutations in HN’s secondary sialic acid binding site are growth impaired in differentiated human airway epithelium (HAE) cultures and in vivo. Here we have shown that adaptation of HPIV3 to growth in the lung is determined by specific features of HN and F that are different from those required for growth in cultured immortalized cells. An HPIV3 virus bearing a mutated HN (H552Q), which is fit and fusogenic in immortalized cells but unfit for growth in the lung, evolved into a less-fusogenic but viable virus in differentiated human airway epithelium. Stepwise evolution led to a progressive decrease in efficiency of fusion activation by the HN/F pair, with a mutation in F first decreasing the activation of F by HN and a mutation in HN’s secondary sialic acid binding site decreasing fusion activation further and producing a stable virus. Adaptation of HPIV3 to successful growth in HAE is determined by specific features of HN and F that lead to a less easily activated fusion mechanism.

Human parainfluenza viruses (HPIVs) are paramyxoviruses that cause the majority of childhood cases of croup, bronchiolitis, and pneumonia worldwide, but there are currently no vaccines or antivirals available for treatment. Enveloped viruses must fuse their membrane with the target cell membrane in order to initiate infection. Parainfluenza virus fusion proceeds via a multistep reaction orchestrated by the two glycoproteins that make up its fusion machine. The receptor-binding hemagglutinin-neuraminidase (HN), upon receptor engagement, activates the fusion protein (F) to penetrate the target cell and mediate viral entry. In this study, we show that the precise balance of fusion activation properties of these two glycoproteins during entry is key for infection. In clinically relevant tissues, viruses evolve to acquire a set of fusion features that provide key clues about requirements for infection in human beings.

Comparison of the Luminex xTAG RVP Fast assay and the Idaho Technology FilmArray RP assay for detection of respiratory viruses in pediatric patients at a cancer hospital

Respiratory viruses are increasingly recognized as serious causes of morbidity and mortality in immunocompromised patients. The rapid and sensitive detection of respiratory viruses is essential for the early diagnosis and administration of appropriate antiviral therapy, as well as for the effective implementation of infection control measures. We compared the performance of two commercial assays, xTAG RVP Fast (Luminex Diagnostics, Toronto, Canada) and FilmArray RVP (FA RVP; Idaho Technology, Salt Lake City, UT), in pediatric patients at Memorial Sloan-Kettering Cancer Center. These assays detect the following viruses: respiratory syncytial virus; influenza A and B viruses; parainfluenza viruses 1, 2, 3, and 4; human metapneumovirus; adenovirus; enterovirus-rhinovirus; coronaviruses NL63, HKU1, 229E, and OC43; and bocavirus. We tested a total of 358 respiratory specimens from 173 pediatric patients previously tested by direct fluorescence assay (DFA) and viral culture. The overall detection rate (number of positive specimens/total specimens) for viruses tested by all methods was 24% for DFA/culture, 45% for xTAG RVP Fast, and 51% for FA RVP. The agreement between the two multiplex assays was 84.5%, and the difference in detection rate was statistically significant (P < 0.0001). Overall, the FA RVP assay was more sensitive than the xTAG RVP Fast assay and had a turnaround time of approximately 1 h. The sensitivity, simplicity, and random-access platform make FA RVP an excellent choice for laboratory on-demand service with low to medium volume.

Pathogenesis of acute respiratory illness caused by human parainfluenza viruses

Human parainfluenza viruses (HPIVs) are a common cause of acute respiratory illness throughout life. Infants, children, and the immunocompromised are the most likely to develop severe disease. HPIV1 and HPIV2 are best known to cause croup while HPIV3 is a common cause of bronchiolitis and pneumonia. HPIVs replicate productively in respiratory epithelial cells and do not spread systemically unless the host is severely immunocompromised. Molecular studies have delineated how HPIVs evade and block cellular innate immune responses to permit efficient replication, local spread, and host-to-host transmission. Studies using ex vivo human airway epithelium have focused on virus tropism, cellular pathology and the epithelial inflammatory response, elucidating how events early in infection shape the adaptive immune response and disease outcome.

Premature activation of the paramyxovirus fusion protein before target cell attachment with corruption of the viral fusion machinery

Paramyxoviruses, including the childhood pathogen human parainfluenza virus type 3, enter host cells by fusion of the viral and target cell membranes. This fusion results from the concerted action of its two envelope glycoproteins, the hemagglutinin-neuraminidase (HN) and the fusion protein (F). The receptor-bound HN triggers F to undergo conformational changes that render it competent to mediate fusion of the viral and cellular membranes. We proposed that, if the fusion process could be activated prematurely before the virion reaches the target host cell, infection could be prevented. We identified a small molecule that inhibits paramyxovirus entry into target cells and prevents infection. We show here that this compound works by an interaction with HN that results in F-activation prior to receptor binding. The fusion process is thereby prematurely activated, preventing fusion of the viral membrane with target cells and precluding viral entry. This first evidence that activation of a paramyxovirus F can be specifically induced before the virus contacts its target cell suggests a new strategy with broad implications for the design of antiviral agents.