Influenza A/H5N1 infection: other treatment options and issues

Helmet CPAP revisited in COVID-19 pneumonia: A case series

Introduction

Noninvasive positive pressure ventilation (NIPPV) plays an important role in the management of respiratory failure. However, since the emergence of the COVID-19 pandemic, utilization of traditional face mask NIPPV has been curtailed in part due to risk of aerosolization of respiratory particles and subsequent health care worker exposure. A randomized clinical trial in 2016 reported that an alternative interface, helmet NIPPV, may be more effective than traditional NIPPV at preventing intubation and improving mortality. The helmet NIPPV interface provides positive airway pressure, while also theoretically minimizing aerosolization, making it a feasible modality in management of respiratory failure in COVID-19 patients.

Case and outcomes

This report describes a single-center experience of a series of three COVID-19 patients with hypoxemic respiratory failure managed with helmet NIPPV. One patient was able to avoid intubation while a second patient was successfully extubated to NIPPV. Ultimately, the third patient was unable to avoid intubation with helmet NIPPV, although the application of the device was late in the progression of the disease.

Discussion

NIPPV is an important modality in the management of respiratory failure and has been shown to reduce the need for immediate endotracheal intubation in select populations. For patients unable to tolerate facemask NIPPV, the helmet provides an alternate interface. In COVID-19 patients, the helmet interface may reduce the risk of virus exposure to health care workers from aerosolization. Based on this experience, we recommend that helmet NIPPV can be considered as a feasible option for the management of patients with COVID-19, whether the goal is to prevent immediate intubation or avoid post-extubation respiratory failure. Randomized studies are needed to definitively validate the use of helmet NIPPV in this population.

Conclusion

Helmet NIPPV is a feasible therapy to manage COVID-19 patients.

Broad neutralizing activity of a human monoclonal antibody against H7N9 strains from 2013 to 2017

H7N9 influenza virus has been circulating among humans for five epidemic waves since it was first isolated in 2013 in China. The recent increase in H7N9 infections during the fifth outbreak in China has caused concerns of a possible pandemic. In this study, we describe a previously characterized human monoclonal antibody, HNIgGA6, obtained by isolating rearranged heavy-chain and light-chain genes from patients who had recovered from H7N9 infections. HNIgGA6 recognized multiple HAs and neutralized the infectivity of 11 out of the 12 H7N9 strains tested, as well as three emerging HPAI H7N9 isolates. The only resistant strain was A/Shanghai/1/2013 (H7N9-SH1), which carries the avian receptor alleles 186V and 226Q in the sialic acid-binding pocket. The mAb broadly neutralized divergent H7N9 strains from 2013 to 2017 and represents a potential alternative treatment for H7N9 interventions.

Exhaled air dispersion during noninvasive ventilation via helmets and a total facemask

BACKGROUND

Noninvasive ventilation (NIV) via helmet or total facemask is an option for managing patients with respiratory infections in respiratory failure. However, the risk of nosocomial infection is unknown.

METHODS

We examined exhaled air dispersion during NIV using a human patient simulator reclined at 45° in a negative pressure room with 12 air changes/h by two different helmets via a ventilator and a total facemask via a bilevel positive airway pressure device. Exhaled air was marked by intrapulmonary smoke particles, illuminated by laser light sheet, and captured by a video camera for data analysis. Significant exposure was defined as where there was ≥ 20% of normalized smoke concentration.

RESULTS

During NIV via a helmet with the simulator programmed in mild lung injury, exhaled air leaked through the neck-helmet interface with a radial distance of 150 to 230 mm when inspiratory positive airway pressure was increased from 12 to 20 cm H2O, respectively, while keeping the expiratory pressure at 10 cm H2O. During NIV via a helmet with air cushion around the neck, there was negligible air leakage. During NIV via a total facemask for mild lung injury, air leaked through the exhalation port to 618 and 812 mm when inspiratory pressure was increased from 10 to 18 cm H2O, respectively, with the expiratory pressure at 5 cm H2O.

CONCLUSIONS

A helmet with a good seal around the neck is needed to prevent nosocomial infection during NIV for patients with respiratory infections.

A potent broad-spectrum protective human monoclonal antibody crosslinking two haemagglutinin monomers of influenza A virus

Effective annual influenza vaccination requires frequent changes in vaccine composition due to both antigenic shift for different subtype hemagglutinins (HAs) and antigenic drift in a particular HA. Here we present a broadly neutralizing human monoclonal antibody with an unusual binding modality. The antibody, designated CT149, was isolated from convalescent patients infected with pandemic H1N1 in 2009. CT149 is found to neutralize all tested group 2 and some group 1 influenza A viruses by inhibiting low pH-induced, HA-mediated membrane fusion. It promotes killing of infected cells by Fc-mediated antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity. X-ray crystallographic data reveal that CT149 binds primarily to the fusion domain in HA2, and the light chain is also largely involved in binding. The epitope recognized by this antibody comprises amino-acid residues from two adjacent protomers of HA. This binding characteristic of CT149 will provide more information to support the design of more potent influenza vaccines.

Emerging respiratory tract viral infections

PURPOSE OF REVIEW

This article reviews the clinical and treatment aspects of avian influenza viruses and the Middle East Respiratory Syndrome coronavirus (MERS-CoV).

RECENT FINDINGS

Avian influenza A(H5N1) and A(H7N9) viruses have continued to circulate widely in some poultry populations and infect humans sporadically. Sporadic human cases of avian A(H5N6), A(H10N8) and A(H6N1) have also emerged. Closure of live poultry markets in China has reduced the risk of A(H7N9) infection. Observational studies have shown that oseltamivir treatment for adults hospitalized with severe influenza is associated with lower mortality and better clinical outcomes, even as late as 4-5 days after symptom onset. Whether higher than standard doses of neuraminidase inhibitor would provide greater antiviral effects in such patients requires further investigation. High-dose systemic corticosteroids were associated with worse outcomes in patients with A(H1N1)pdm09 or A(H5N1). MERS-CoV has continued to spread since its first discovery in 2012. The mortality rates are high in those with comorbid diseases. There is no specific antiviral treatment or vaccine available. The exact mode of transmission from animals to humans remains unknown.

SUMMARY

There is an urgent need for developing more effective antiviral therapies to reduce morbidity and mortality of these emerging viral respiratory tract infections.

Noninvasive Mechanical Ventilation: Models to Assess Air and Particle Dispersion

Respiratory failure is a major complication of viral infections such as severe acute respiratory syndrome (SARS) [1], avian influenza H5N1 infection [2], and the 2009 pandemic influenza (H1N1) infection [3]. The course may progress rapidly to acute respiratory distress syndrome (ARDS) and multi-organ failure, requiring intensive care. Noninvasive ventilation (NIV) may play a supportive role in patients with severe viral pneumonia and early ARDS/acute lung injury. It can act as a bridge to invasive mechanical ventilation, although it is contraindicated in critically ill patients with hemodynamic instability and multi-organ dysfunction syndrome [4]. Transmission of some of these viral infections can convert from droplets to airborne during respiratory therapy.

Modeling host genetic regulation of influenza pathogenesis in the collaborative cross

Genetic variation contributes to host responses and outcomes following infection by influenza A virus or other viral infections. Yet narrow windows of disease symptoms and confounding environmental factors have made it difficult to identify polymorphic genes that contribute to differential disease outcomes in human populations. Therefore, to control for these confounding environmental variables in a system that models the levels of genetic diversity found in outbred populations such as humans, we used incipient lines of the highly genetically diverse Collaborative Cross (CC) recombinant inbred (RI) panel (the pre-CC population) to study how genetic variation impacts influenza associated disease across a genetically diverse population. A wide range of variation in influenza disease related phenotypes including virus replication, virus-induced inflammation, and weight loss was observed. Many of the disease associated phenotypes were correlated, with viral replication and virus-induced inflammation being predictors of virus-induced weight loss. Despite these correlations, pre-CC mice with unique and novel disease phenotype combinations were observed. We also identified sets of transcripts (modules) that were correlated with aspects of disease. In order to identify how host genetic polymorphisms contribute to the observed variation in disease, we conducted quantitative trait loci (QTL) mapping. We identified several QTL contributing to specific aspects of the host response including virus-induced weight loss, titer, pulmonary edema, neutrophil recruitment to the airways, and transcriptional expression. Existing whole-genome sequence data was applied to identify high priority candidate genes within QTL regions. A key host response QTL was located at the site of the known anti-influenza Mx1 gene. We sequenced the coding regions of Mx1 in the eight CC founder strains, and identified a novel Mx1 allele that showed reduced ability to inhibit viral replication, while maintaining protection from weight loss.

Host responses to an infectious agent are highly variable across the human population, however, it is not entirely clear how various factors such as pathogen dose, demography, environment and host genetic polymorphisms contribute to variable host responses and infectious outcomes. In this study, a new in vivo experimental model was used that recapitulates many of the genetic characteristics of an outbred population, such as humans. By controlling viral dose, environment and demographic variables, we were able to focus on the role that host genetic variation plays in influenza virus infection. Both the range of disease phenotypes and the combinations of sets of disease phenotypes at 4 days post infection across this population exhibited a large amount of diversity, reminiscent of the variation seen across the human population. Multiple host genome regions were identified that contributed to different aspects of the host response to influenza infection. Taken together, these results emphasize the critical role of host genetics in the response to infectious diseases. Given the breadth of host responses seen within this population, several new models for unique host responses to infection were identified.

Nonventilatory strategies for patients with life-threatening 2009 H1N1 influenza and severe respiratory failure

Severe respiratory failure (including acute lung injury and acute respiratory distress syndrome) caused by 2009 H1N1 influenza infection has been reported worldwide. Refractory hypoxemia is a common finding in these patients and can be challenging to manage. This review focuses on nonventilatory strategies in the advanced treatment of severe respiratory failure and refractory hypoxemia such as that seen in patients with severe acute respiratory distress syndrome attributable to 2009 H1N1 influenza. Specific modalities covered include conservative fluid management, prone positioning, inhaled nitric oxide, inhaled vasodilatory prostaglandins, and extracorporeal membrane oxygenation and life support. Pharmacologic strategies (including steroids) investigated for the treatment of severe respiratory failure are also reviewed.

Protective mechanical ventilation does not exacerbate lung function impairment or lung inflammation following influenza A infection

The degree to which mechanical ventilation induces ventilator-associated lung injury is dependent on the initial acute lung injury (ALI). Viral-induced ALI is poorly studied, and this study aimed to determine whether ALI induced by a clinically relevant infection is exacerbated by protective mechanical ventilation. Adult female BALB/c mice were inoculated with 104.5 plaque-forming units of influenza A/Mem/1/71 in 50 μl of medium or medium alone. This study used a protective ventilation strategy, whereby mice were anesthetized, tracheostomized, and mechanically ventilated for 2 h. Lung mechanics were measured periodically throughout the ventilation period using a modification of the forced oscillation technique to obtain measures of airway resistance and coefficients of tissue damping and tissue elastance. Thoracic gas volume was measured and used to obtain specific airway resistance, tissue damping, and tissue elastance. At the end of the ventilation period, a bronchoalveolar lavage sample was collected to measure inflammatory cells, macrophage inflammatory protein-2, IL-6, TNF-α, and protein leak. Influenza infection caused significant increases in inflammatory cells, protein leak, and deterioration in lung mechanics that were not exacerbated by mechanical ventilation, in contrast to previous studies using bacterial and mouse-specific viral infection. This study highlighted the importance of type and severity of lung injury in determining outcome following mechanical ventilation.

Exhaled air dispersion distances during noninvasive ventilation via different Respironics face masks

BACKGROUND

As part of our influenza pandemic preparedness, we studied the exhaled air dispersion distances and directions through two different face masks (Respironics; Murrysville, PA) attached to a human-patient simulator (HPS) during noninvasive positive-pressure ventilation (NPPV) in an isolation room with pressure of -5 Pa.

METHODS

The HPS was positioned at 45 degrees on the bed and programmed to mimic mild lung injury (oxygen consumption, 300 mL/min; lung compliance, 35 mL/cm H(2)O). Airflow was marked with intrapulmonary smoke for visualization. Inspiratory positive airway pressure (IPAP) started at 10 cm H(2)O and gradually increased to 18 cm H(2)O, whereas expiratory pressure was maintained at 4 cm H(2)O. A leakage jet plume was revealed by a laser light sheet, and images were captured by high definition video. Normalized exhaled air concentration in the plume was estimated from the light scattered by the smoke particles.

FINDINGS

As IPAP increased from 10 to 18 cm H(2)O, the exhaled air of a low normalized concentration through the ComfortFull 2 mask (Respironics) increased from 0.65 to 0.85 m at a direction perpendicular to the head of the HPS along the median sagittal plane. When the IPAP of 10 cm H(2)O was applied via the Image 3 mask (Respironics) connected to the whisper swivel, the exhaled air dispersed to 0.95 m toward the end of the bed along the median sagittal plane, whereas higher IPAP resulted in wider spread of a higher concentration of smoke.

CONCLUSIONS

Substantial exposure to exhaled air occurs within a 1-m region, from patients receiving NPPV via the ComfortFull 2 mask and the Image 3 mask, with more diffuse leakage from the latter, especially at higher IPAP.

Emerging influenza virus: a global threat

Since 1918, influenza virus has been one of the major causes of morbidity and mortality, especially among young children. Though the commonly circulating strain of the virus is not virulent enough to cause mortality, the ability of the virus genome to mutate at a very high rate may lead to the emergence of a highly virulent strain that may become the cause of the next pandemic. Apart from the influenza virus strain circulating in humans (H1N1 and H3N2), the avian influenza H5N1 H7 and H9 virus strains have also been reported to have caused human infections, H5N1 H7 and H9 have shown their ability to cross the species barrier from birds to humans and further replicate in humans. This review addresses the biological and epidemiological aspects of influenza virus and efforts to have a control on the virus globally.