Prolonged influenza virus shedding and emergence of antiviral resistance in immunocompromised patients and ferrets

Virus Evolution in Prolonged Infections of Immunocompromised Individuals

BACKGROUND

Many viruses can cause persistent infection and/or viral shedding in immunocompromised hosts. This is a well-described occurrence not only with SARS-CoV-2 but for many other viruses as well. Understanding how viruses evolve and mutate in these patients and the global impact of this phenomenon is critical as the immunocompromised population expands.

CONTENT

In this review, we provide an overview of populations at risk for prolonged viral shedding, clinical manifestations of persistent viral infection, and methods of assessing viral evolution. We then review the literature on viral evolution in immunocompromised patients across an array of RNA viruses, including SARS-CoV-2, norovirus, influenza, and poliovirus, and discuss the global implications of persistent viral infections in these hosts.

SUMMARY

There is significant evidence for accelerated viral evolution and accumulation of mutations in antigenic sites in immunocompromised hosts across many viral pathogens. However, the implications of this phenomenon are not clear; while there are rare reports of transmission of these variants, they have not clearly been shown to predict disease outbreaks or have significant global relevance. Emerging methods including wastewater monitoring may provide a more sophisticated understanding of the impact of variants that evolve in immunocompromised hosts on the wider host population.

Drug susceptibility and the potential for drug-resistant SARS-CoV-2 emergence in immunocompromised animals

The reduced susceptibility of mRNA vaccines and diminished neutralizing activity of therapeutic monoclonal antibodies against Omicron variants, including BQ.1.1, XBB, and their descendants, highlight the importance of antiviral therapies. Here, we assessed the efficacy of two antivirals, molnupiravir, targeting a viral RNA-dependent RNA polymerase, and nirmatrelvir, targeting a main protease, against BQ.1.1 in hamsters. We found that prophylactic or therapeutic treatment with either drug significantly reduced the viral load in the lungs of infected hamsters. We also evaluated the risk of emergence of drug-resistant viruses in immunocompromised hamsters. Although 13 days of drug treatment reduced viral titers, the immunocompromised hosts could not completely clear the virus. Viruses isolated from drug-treated immunocompromised hamsters did not show reduced susceptibility to the drugs. Molnupiravir and nirmatrelvir remain effective in vivo against variants with reduced susceptibility to monoclonal antibodies and mRNA vaccine-induced antibodies, with limited emergence of drug-resistant variants under the conditions tested.

Pitfalls in definitions on respiratory viruses and particularities of Adenovirus infection in hematopoietic cell transplantation patients: Recommendations from the EBMT practice harmonization and guidelines committee

In 2023, the EBMT Practice harmonization and Guidelines Committee partnered with the EBMT Infection Diseases Working Party (IDWP) to undertake the task of delivering best practice recommendations, aiming to harmonize by expert consensus, the already existing definitions and future epidemiological and clinical studies among centers of the EBMT network. To attain this objective, a group of experts in the field was convened. The workgroup identified and discussed some critical aspects in definitions of community-acquired respiratory viruses (CARV) and adenovirus (ADV) infections in recipient of hematopoietic cell transplant (HCT). The methodology involved literature review and expert consensus. For CARV, expert consensus focused on defining infection severity, infection duration, and establishing criteria for lower respiratory tract disease (LRTD). For ADV, the expert consensus focused on surveillance methods and the definitions of ADV infection, certainty levels of disease, response to treatment, and attributable mortality. This consensus workshop provided indications to EBMT community aimed at facilitating data collection and consistency in the EBMT registry for respiratory viral infectious complications.

Zanamivir and baloxavir combination to cure persistent influenza and coronavirus infections after hematopoietic stem cell transplant

OBJECTIVES

Immunocompromised patients may experience prolonged shedding of influenza virus potentially leading to severe infections. Alternatives to monotherapy with neuraminidase inhibitors should be evaluated to entirely suppress viral replication and prevent drug-resistant mutations.

METHODS

We investigated the clinical and virological evolution in a case of persistent influenza A and human coronavirus OC43 (HCoV-OC43) coinfection in a hematopoietic stem cell transplant recipient after different therapeutic strategies.

RESULTS

Successive oseltamivir and zanamivir monotherapies failed to control both infections, with positive results persisting for over 110 days each. This led to the emergence of highly resistant oseltamivir strains due to neuraminidase mutations (E119V and R292K) followed by a deletion (del245-248), while maintaining sensitivity to zanamivir. The intra-host viral diversity data showed that the treatments impacted viral diversity of influenza virus, but not of HCoV-OC43. Considering the patient's underlying condition and the impact of prolonged viral shedding on pulmonary function, eradicating the influenza virus was necessary. A 10-day regimen combining zanamivir and baloxavir-marboxil effectively controlled influenza virus replication and was associated with the clearance of HCoV-OC43, finally resulting in comprehensive respiratory recovery.

CONCLUSION

These observations underscore the importance of further investigating combination treatments as the primary approach to achieve influenza eradication in immunocompromised patients.

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.

Is It Possible to Test for Viral Infectiousness?: The Use Case of (SARS-CoV-2)

Identifying and managing individuals with active or chronic disease, implementing appropriate infection control measures, and mitigating the spread of the COVID-19 pandemic highlighted the need for tests of infectiousness. The gold standard for assessing infectiousness has been the recovery of infectious virus in cell culture. Using cycle threshold values, antigen testing, and SARS-CoV-2, replication intermediate strands were used to assess infectiousness, with many limitations. Infectiousness can be influenced by host factors (eg, preexisting immune responses) and virus factors (eg, evolution).

Approach to hematopoietic cell transplant candidates with respiratory viral detection

The management of respiratory viruses prior to hematopoietic cell transplant (HCT) can be controversial and requires special consideration of host factors, transplant parameters, and the specific respiratory virus (RV). In the setting of adenovirus (ADV), human metapneumovirus (HMPV), influenza, parainfluenza virus (PIV), and respiratory syncytial virus (RSV) detection prior to hematopoietic cell transplant (HCT), clinical practice guidelines recommend transplant delay when possible; however, there is much more ambiguity when other respiratory viruses, such as seasonal coronaviruses (CoVs), human rhinovirus (HRV), and SARS-CoV-2, are detected. Our aims for this review include detailing clinical practical guidelines and reviewing current literature on pre-transplant respiratory viral infections (RVIs), including antiviral therapies and prevention strategies, when available. We will center our discussion on three representative clinical scenarios, with the goal of providing practical guidance to clinicians.

Increased circulation of human adenovirus in 2023: an investigation of the circulating genotypes, upper respiratory viral loads, and hospital admissions in a large academic medical center

IMPORTANCE

The circulation of human adenoviruses (HAdV) increased in 2023. In this manuscript, we show that HAdV-B3 was predominant in 2023 in a cohort characterized by the Johns Hopkins Hospital System. We also show that HAdV-B3 was associated with an increase in viral loads in respiratory samples and provide a correlation with the clinical presentations and outcomes.

Efficacy of oseltamivir treatment in influenza virus-infected obese mice

Obesity has been epidemiologically and empirically linked with more severe diseases upon influenza infection. To ameliorate severe disease, treatment with antivirals, such as the neuraminidase inhibitor oseltamivir, is suggested to begin within days of infection especially in high-risk hosts. However, this treatment can be poorly effective and may generate resistance variants within the treated host. Here, we hypothesized that obesity would reduce oseltamivir treatment effectiveness in the genetically obese mouse model. We demonstrated that oseltamivir treatment does not improve viral clearance in obese mice. While no traditional variants associated with oseltamivir resistance emerged, we did note that drug treatment failed to quench the viral population and did lead to phenotypic drug resistance in vitro. Together, these studies suggest that the unique pathogenesis and immune responses in obese mice could have implications for pharmaceutical interventions and the within-host dynamics of the influenza virus population. IMPORTANCE Influenza virus infections, while typically resolving within days to weeks, can turn critical, especially in high-risk populations. Prompt antiviral administration is crucial to mitigating these severe sequalae, yet concerns remain if antiviral treatment is effective in hosts with obesity. Here, we show that oseltamivir does not improve viral clearance in genetically obese or type I interferon receptor-deficient mice. This suggests a blunted immune response may impair oseltamivir efficacy and render a host more susceptible to severe disease. This study furthers our understanding of oseltamivir treatment dynamics both systemically and in the lungs of obese mice, as well as the consequences of oseltamivir treatment for the within-host emergence of drug-resistant variants.

Antisense oligonucleotides: a promising therapeutic option against infectious diseases

Infectious diseases have been one of the biggest health problems of humanity for centuries. Nucleic acid-based therapeutics have received attention in recent years with their effectiveness in the treatment of various infectious diseases and vaccine development studies. This review aims to provide a comprehensive understanding of the basic properties underlying the mechanism of antisense oligonucleotides (ASOs), their applications, and their challenges. The efficient delivery of ASOs is the greatest challenge for their therapeutic success, but this problem is overcome with new-generation antisense molecules developed with chemical modifications. The types, carrier molecules, and gene regions targeted by sequences have been summarized in detail. Research and development of antisense therapy is still in its infancy; however, gene silencing therapies appear to have the potential for faster and longer-lasting activity than conventional treatment strategies. On the other hand, realizing the potential of antisense therapy will require a large initial economic investment to ascertain the pharmacological properties and learn how to optimize them. The ability of ASOs to be rapidly designed and synthesized to target different microbes can reduce drug discovery time from 6 years to 1 year. Since ASOs are not particularly affected by resistance mechanisms, they come to the fore in the fight against antimicrobial resistance. The design-based flexibility of ASOs has enabled it to be used for different types of microorganisms/genes and successful in vitro and in vivo results have been revealed. The current review summarized a comprehensive understanding of ASO therapy in combating bacterial and viral infections.

A target-cell limited model can reproduce influenza infection dynamics in hosts with differing immune responses

We consider a hierarchy of ordinary differential equation models that describe the within-host viral kinetics of influenza infections: the IR model explicitly accounts for an immune response to the virus, while the simpler, target-cell limited TEIV and TV models do not. We show that when the IR model is fitted to pooled experimental murine data of the viral load, fraction of dead cells, and immune response levels, its parameters values can be determined. However, if, as is common, only viral load data are available, we can estimate parameters of the TEIV and TV models but not the IR model. These results are substantiated by a structural and practical identifiability analysis. We then use the IR model to generate synthetic data representing infections in hosts whose immune responses differ. We fit the TV model to these synthetic datasets and show that it can reproduce the characteristic exponential increase and decay of viral load generated by the IR model. Furthermore, the values of the fitted parameters of the TV model can be mapped from the immune response parameters in the IR model. We conclude that, if only viral load data are available, a simple target-cell limited model can reproduce influenza infection dynamics and distinguish between hosts with differing immune responses.

Development of Digital Droplet PCR Targeting the Influenza H3N2 Oseltamivir-Resistant E119V Mutation and Its Performance through the Use of Reverse Genetics Mutants

The monitoring of antiviral-resistant influenza virus strains is important for public health given the availability and use of neuraminidase inhibitors and other antivirals to treat infected patients. Naturally occurring oseltamivir-resistant seasonal H3N2 influenza virus strains often carry a glutamate-to-valine substitution at position 119 in the neuraminidase (E119V-NA). Early detection of resistant influenza viruses is important for patient management and for the rapid containment of antiviral resistance. The neuraminidase inhibition assay allows the phenotypical identification of resistant strains; however, this test often has limited sensitivity with high variability depending on the virus strain, drugs and assays. Once a mutation such as E119V-NA is known, highly sensitive PCR-based genotypic assays can be used to identify the prevalence of such mutant influenza viruses in clinical samples. In this study, based on an existing reverse transcriptase real-time PCR (RT-qPCR) assay, we developed a reverse transcriptase droplet digital PCR assay (RT-ddPCR) to detect and quantify the frequency of the E119V-NA mutation. Furthermore, reverse genetics viruses carrying this mutation were created to test the performance of the RT-ddPCR assay and compare it to the standard phenotypic NA assay. We also discuss the advantage of using an RT-ddPCR instead of qPCR method in the context of viral diagnostics and surveillance.

Assessing the fitness of a dual-antiviral drug resistant human influenza virus in the ferret model

Influenza antivirals are important tools in our fight against annual influenza epidemics and future influenza pandemics. Combinations of antivirals may reduce the likelihood of drug resistance and improve clinical outcomes. Previously, two hospitalised immunocompromised influenza patients, who received a combination of a neuraminidase inhibitor and baloxavir marboxil, shed influenza viruses resistant to both drugs. Here-in, the replicative fitness of one of these A(H1N1)pdm09 virus isolates with dual resistance mutations (NA-H275Y and PA-I38T) was similar to wild type virus (WT) in vitro, but reduced in the upper respiratory tracts of challenged ferrets. The dual-mutant virus transmitted well between ferrets in an airborne transmission model, but was outcompeted by the WT when the two viruses were co-administered. These results indicate the dual-mutant virus had a moderate loss of viral fitness compared to the WT virus, suggesting that while person-to-person transmission of the dual-resistant virus may be possible, widespread community transmission is unlikely.

Effect of Baloxavir and Oseltamivir in Combination on Infection with Influenza Viruses with PA/I38T or PA/E23K Substitutions in the Ferret Model

Amino acid substitutions I38T and E23K in the influenza polymerase acidic (PA) protein lead to reduced susceptibility to the influenza antiviral drug baloxavir. The in vivo effectiveness of baloxavir and oseltamivir for treatment of these viruses is currently unknown. Using patient-derived influenza isolates, combination therapy was equally effective as monotherapy in reducing viral titers in the upper respiratory tract of ferrets infected with A(H1N1pdm09)-PA/E23K or A(H3N2)-PA/I38T. When treated with baloxavir plus oseltamivir, infection with a mixture of PA/I38T or PA/E23K and corresponding wild-type virus was characterized by a lower selection of viruses with reduced baloxavir susceptibility over the course of infection compared to baloxavir monotherapy. De novo emergence of the oseltamivir resistance mutation NA/H275Y occurred in ferrets treated with oseltamivir alone but not in ferrets treated with baloxavir plus oseltamivir. Our data suggest that combination therapy with influenza drugs with different mechanisms of action decreased the selection pressure for viruses with reduced drug susceptibility.

Enhanced inflammation and suppressed adaptive immunity in COVID-19 with prolonged RNA shedding

Little is known regarding why a subset of COVID-19 patients exhibited prolonged positivity of SARS-CoV-2 infection. Here, we found that patients with long viral RNA course (LC) exhibited prolonged high-level IgG antibodies and higher regulatory T (Treg) cell counts compared to those with short viral RNA course (SC) in terms of viral load. Longitudinal proteomics and metabolomics analyses of the patient sera uncovered that prolonged viral RNA shedding was associated with inhibition of the liver X receptor/retinoid X receptor (LXR/RXR) pathway, substantial suppression of diverse metabolites, activation of the complement system, suppressed cell migration, and enhanced viral replication. Furthermore, a ten-molecule learning model was established which could potentially predict viral RNA shedding period. In summary, this study uncovered enhanced inflammation and suppressed adaptive immunity in COVID-19 patients with prolonged viral RNA shedding, and proposed a multi-omic classifier for viral RNA shedding prediction.

Preclinical and clinical developments for combination treatment of influenza

Antiviral drugs are an important measure of control for influenza in the population, particularly for those that are severely ill or hospitalised. The neuraminidase inhibitor (NAI) class of drugs, including oseltamivir, have been the standard of care (SOC) for severe influenza illness for many years. The approval of drugs with novel mechanisms of action, such as baloxavir marboxil, is important and broadens potential treatment options for combination therapy. The use of antiviral treatments in combination for influenza is of interest; one potential benefit of this treatment strategy is that the combination of drugs with different mechanisms of action may lower the selection of resistance due to treatment. In addition, combination therapy may become an important treatment option to improve patient outcomes in those with severe illness due to influenza or those that are immunocompromised. Clinical trials increasingly evaluate drug combinations in a range of patient cohorts. Here, we summarise preclinical and clinical advances in combination therapy for the treatment of influenza with reference to immunocompromised animal models and clinical data in hospitalised patient cohorts where available. There is a wide array of drug categories in development that have also been tested in combination. Therefore, in this review, we have included polymerase inhibitors, monoclonal antibodies (mAbs), host-targeted therapies, and adjunctive therapies. Combination treatment regimens should be carefully evaluated to determine whether they provide an added benefit relative to effectiveness of monotherapy and in a variety of patient cohorts, particularly, if there is a greater chance of an adverse outcome. Safe and effective treatment of influenza is important not only for seasonal influenza infection, but also if a pandemic strain was to emerge.

A ferret model of immunosuppression induced with dexamethasone

Ferrets are nowadays frequently used as animal models for biomedical purposes; in many cases, immunosuppression of experimental animals is necessary. The aim of this study was to evaluate the effect of intramuscular dexamethasone administration (2 mg/kg as the initiation dose continued with 1 mg/kg q 12 h applied 5 times) on ferret's immune system. In comparison with ferrets which received the saline (n = 5), significantly lower total counts of leukocytes (P < 0.01), lymphocytes (P < 0.01) and monocyte (P < 0.05), as well as absolute numbers of CD4+CD8- (P < 0.01) and CD4-CD8+ (P < 0.01) subsets were noted in dexamethasone treated ferrets (n = 5) the first day after the treatment (D1). Absolute number of CD79+ lymphocytes remained unchanged throughout the experiment. The proliferation activity of lymphocytes in dexamethasone treated ferrets was lower only in D1 using concanavalin A (conA), phytohemagglutinin (PHA) and pokeweed mitogen (PWM); statistical significance was noted using PHA 40 (P < 0.05) and PWM 10 (P < 0.01). Lower neutrophil activity (P < 0.01) was detected in D1 after the dexamethasone treatment in both production of reactive oxygen species (chemiluminescence test) and ingestion of particles (phagocytosis assay). The dexamethasone treatment proved to be useful for short-term immunosuppression in ferrets. The results closely resembled data previously reported in human studies and indicate classification of ferrets as steroid-resistant species.

Influenza polymerase inhibitor resistance: Assessment of the current state of the art - A report of the isirv Antiviral group

It is more than 20 years since the neuraminidase inhibitors, oseltamivir and zanamivir were approved for the treatment and prevention of influenza. Guidelines for global surveillance and methods for evaluating resistance were established initially by the Neuraminidase Inhibitor Susceptibility Network (NISN), which merged 10 years ago with the International Society for influenza and other Respiratory Virus Diseases (isirv) to become the isirv-Antiviral Group (isirv-AVG). With the ongoing development of new influenza polymerase inhibitors and recent approval of baloxavir marboxil, the isirv-AVG held a closed meeting in August 2019 to discuss the impact of resistance to these inhibitors. Following this meeting and review of the current literature, this article is intended to summarize current knowledge regarding the clinical impact of resistance to polymerase inhibitors and approaches for surveillance and methods for laboratory evaluation of resistance, both in vitro and in animal models. We highlight limitations and gaps in current knowledge and suggest some strategies for addressing these gaps, including the need for additional clinical studies of influenza antiviral drug combinations. Lessons learned from influenza resistance monitoring may also be helpful for establishing future drug susceptibility surveillance and testing for SARS-CoV-2.

The limits of refusal: An ethical review of solid organ transplantation and vaccine hesitancy

Patients pursuing solid organ transplantation are encouraged to receive many vaccines on an accelerated timeline. Vaccination prior to transplantation offers the best chance of developing immunity and may expand the pool of donor organs that candidates can accept without needing posttransplant therapy. Furthermore, transplant recipients are at greater risk for acquiring vaccine-preventable illnesses or succumbing to severe sequelae of such illnesses. However, a rising rate of vaccine refusal has challenged transplant centers to address the phenomenon of vaccine hesitancy. Transplant centers may need to consider adopting a policy of denial of solid organ transplantation on the basis of vaccine refusal for non-medical reasons (i.e., philosophical or religious objections or personal beliefs that vaccines are unnecessary or unsafe). Arguments supporting such a policy are motivated by utility, stewardship, and beneficence. Arguments opposing such a policy emphasize justice and respect for persons, and seek to avoid worsening inequities or medical coercion. This paper examines these arguments and situates them within the special cases of pediatric transplantation, emergent transplantation, and living donation. Ultimately, a uniform national policy addressing vaccine refusal among transplant candidates is needed to resolve this ethical dilemma and establish a consistent, fair, and standard approach to vaccine refusal in transplantation.

COVID-19 in the Context of Inborn Errors of Immunity: a Case Series of 31 Patients from Mexico

INTRODUCTION

Patients with inborn errors of immunity (IEI) have a compromised or inappropriate immune response. Although they might be considered a high-risk group for severe SARS-CoV-2 infection, the reported impact of COVID-19 in these patients has been reassuring, while the differential susceptibility of distinct types of IEI remains unclear.

OBJECTIVE

We aimed to describe the findings and outcomes of our known patients with IEI who were diagnosed with COVID-19.

METHODS

In a retrospective study from March 2020 to February 2021, four centers in Mexico collected clinical, laboratory, and genetic data from pediatric and adult patients with known diagnoses of IEI who presented with COVID-19, based on compatible symptoms and positive SARS-CoV-2 testing or known household exposure.

RESULTS

We report 31 patients with known IEI from Mexico who presented with SARS-CoV-2 infection. Seventy-four percent were male, 52% were pediatric, and 81% survived. Their ages ranged from 5 months to 56 years, with a median of 17 years. Sixty-five percent had predominant antibody deficiencies, 48% were hospitalized, and 26% required ICU. Pediatric patients had a higher hospital admission rate than adults. Inpatient mortality was 40%, and ICU mortality rate was 63%. Forty-eight percent developed pneumonia, while 36% had evidence of hyperinflammation (4 adults and 7 children). Predominant laboratory features were lymphopenia and thrombocytopenia, seen in 70 and 44% of patients, respectively. The serum D-dimer median value was 2.6 (0.5-20.6) μg/mL, and the median highest ferritin value was 1015 (32-10,303) ng/mL. Intravenous immunoglobulin was used in 80% of patients. Other treatments included macrolides (39%) and corticosteroids (29%). Six patients died from secondary infection or uncontrolled systemic inflammation.

DISCUSSION

Although impaired immunity due to IEI may be a predisposing factor for severe COVID-19, most of our patients with IEI who acquired the SARS-CoV-2 infection developed a well-tolerated infection and survived, as have more than 80% of worldwide reported patients to date. An impaired immune or inflammatory response may be a predisposing factor for some and a protective factor for others. A systematic review of the literature could help identify those patients at risk of severe disease and complications. Healthcare-associated infections should be aggressively prevented.

In Vivo Models to Study the Pathogenesis of Extra-Respiratory Complications of Influenza A Virus Infection

Animal models are an inimitable method to study the systemic pathogenesis of virus-induced disease. Extra-respiratory complications of influenza A virus infections are not extensively studied even though they are often associated with severe disease and mortality. Here we review and recommend mammalian animal models that can be used to study extra-respiratory complications of the central nervous system and cardiovascular system as well as involvement of the eye, placenta, fetus, lacteal gland, liver, pancreas, intestinal tract, and lymphoid tissues during influenza A virus infections.

Viral Kinetics and Resistance Development in Children Treated with Neuraminidase Inhibitors: The Influenza Resistance Information Study (IRIS)

Background

We studied the effect of age, baseline viral load, vaccination status, antiviral therapy, and emergence of drug resistance on viral shedding in children infected with influenza A or B virus.

Methods

Samples from children (aged ≤13 years) enrolled during the 7 years of the prospective Influenza Resistance Information Study were analyzed using polymerase chain reaction to determine the influenza virus (sub-)type, viral load, and resistance mutations. Disease severity was assessed; clinical symptoms were recorded. The association of age with viral load and viral clearance was examined by determining the area under the curve for viral RNA shedding using logistic regression and Kaplan-Meier analyses.

Results

A total of 2131 children infected with influenza (683, A/H1N1pdm09; 825, A/H3N2; 623, influenza B) were investigated. Age did not affect the mean baseline viral load. Children aged 1−5 years had prolonged viral RNA shedding (±1–2 days) compared with older children and up to 1.2-fold higher total viral burden. Besides, in older age (odds ratio [OR], 1.08; confidence interval [CI], 1.05–1.12), prior vaccination status (OR, 1.72; CI, 1.22–2.43) and antiviral treatment (OR, 1.74; CI, 1.43–2.12) increased the rate of viral clearance. Resistance mutations were detected in 49 children infected with influenza A virus (34, A/H1N1pdm09; 15, A/H3N2) treated with oseltamivir, most of whom were aged <5 years (n = 39).

Conclusions

Children aged 1−5 years had a higher total viral burden with prolonged virus shedding and had an increased risk of acquiring resistance mutations following antiviral treatment.

Clinical Trials Registration

NCT00884117.

[Epidemiological features and mechanism of coronavirus disease 2019 in children]

Compared with adults, children tend to have lower incidence rate, hospitalization rate, and mortality rate of coronavirus disease 2019 (COVID-19), while the cause of such age-based differences in disease severity remains unclear. An investigation of pathogenesis in children may help to analyze the therapies for the high-risk population. Human angiotensin-converting enzyme Ⅱ is the main receptor of severe acute respiratory syndrome coronavirus 2 and can limit pulmonary capillary leakage and inflammation mediated by angiotensin 2 and exert a protective effect against acute lung injury. Its expression decreases with age. Regular vaccination and frequent upper respiratory virus infection in children can lead to regular immune activation, and its combination with strong innate immunity can help to achieve virus clearance in the early stage of infection in children with COVID-19. Meanwhile, there are strong regeneration and repair abilities of alveolar epithelial cells in children, which may help with the early recovery of infection. In addition, risk factors, such as underlying cardiopulmonary diseases, obesity, and smoking, are relatively uncommon in children. Social factors, including home quarantine and timely closure of schools, may help to reduce the infection rate in children. However, children with immunodeficiency are a high-risk population and should be closely monitored. Further studies are needed to investigate the immune and protection mechanisms against COVID-19 in children.

Analyses of viral genomes for G-quadruplex forming sequences reveal their correlation with the type of infection

G-quadruplexes contribute to the regulation of key molecular processes. Their utilization for antiviral therapy is an emerging field of contemporary research. Here we present comprehensive analyses of the presence and localization of putative G-quadruplex forming sequences (PQS) in all viral genomes currently available in the NCBI database (including subviral agents). The G4Hunter algorithm was applied to a pool of 11,000 accessible viral genomes representing 350 Mbp in total. PQS frequencies differ across evolutionary groups of viruses, and are enriched in repeats, replication origins, 5'UTRs and 3'UTRs. Importantly, PQS presence and localization is connected to viral lifecycles and corresponds to the type of viral infection rather than to nucleic acid type; while viruses routinely causing persistent infections in Metazoa hosts are enriched for PQS, viruses causing acute infections are significantly depleted for PQS. The unique localization of PQS identifies the importance of G-quadruplex-based regulation of viral replication and life cycle, providing a tool for potential therapeutic targeting.

[Epidemiological features and mechanism of coronavirus disease 2019 in children]

Compared with adults, children tend to have lower incidence rate, hospitalization rate, and mortality rate of coronavirus disease 2019 (COVID-19), while the cause of such age-based differences in disease severity remains unclear. An investigation of pathogenesis in children may help to analyze the therapies for the high-risk population. Human angiotensin-converting enzyme Ⅱ is the main receptor of severe acute respiratory syndrome coronavirus 2 and can limit pulmonary capillary leakage and inflammation mediated by angiotensin 2 and exert a protective effect against acute lung injury. Its expression decreases with age. Regular vaccination and frequent upper respiratory virus infection in children can lead to regular immune activation, and its combination with strong innate immunity can help to achieve virus clearance in the early stage of infection in children with COVID-19. Meanwhile, there are strong regeneration and repair abilities of alveolar epithelial cells in children, which may help with the early recovery of infection. In addition, risk factors, such as underlying cardiopulmonary diseases, obesity, and smoking, are relatively uncommon in children. Social factors, including home quarantine and timely closure of schools, may help to reduce the infection rate in children. However, children with immunodeficiency are a high-risk population and should be closely monitored. Further studies are needed to investigate the immune and protection mechanisms against COVID-19 in children.

Secondary substitutions in the hemagglutinin and neuraminidase genes associated with neuraminidase inhibitor resistance are rare in the Influenza Resistance Information Study (IRIS)

Amino acid substitutions in influenza virus neuraminidase (NA) that cause resistance to neuraminidase inhibitors (NAI) generally result in virus attenuation. However, influenza viruses may acquire secondary substitutions in the NA and hemagglutinin (HA) proteins that can restore viral fitness. To assess to which extent this happens, the emergence of NAI resistance substitutions and secondary - potentially compensatory - substitutions was quantified in influenza viruses of immunocompetent individuals included in the Influenza Resistance Information Study (IRIS; NCT00884117). Known resistance substitutions were detected by mutation specific RT-PCR in viruses of 57 of 1803 (3.2%) oseltamivir-treated individuals, including 39 individuals infected with A/H1N1pdm09 [H275Y] virus and 18 with A/H3N2 [R292K] virus. A total of fifteen and ten other amino acid substitutions were acquired in HA and NA respectively, of A/H1N1pdm09, A/H3N2 and influenza B viruses upon treatment with oseltamivir but none of these was associated with resistance to oseltamivir. All cultured viruses with the known resistance substitutions H275Y or R292K showed reduced susceptibility to oseltamivir in the NA-star assay. Upon next-generation sequencing, the vast majority of NAI resistant A/H1N1pdm09 and A/H3N2 viruses had no resistance-associated secondary substitutions at high frequency. Only in two A/H1N1pdm09 [H275Y] viruses, the potentially compensatory secondary substitutions HA-D52N and NA-R152K were detected. We conclude that the emergence of secondary substitutions that may restore viral fitness upon the emergence of known influenza virus NAI resistance substitutions was a rare event in this immunocompetent population.

Modeling Infection and Tropism of Human Parainfluenza Virus Type 3 in Ferrets

Human parainfluenza virus type 3 (HPIV-3) is a significant cause of lower respiratory tract infections, with the most severe disease in young infants, immunocompromised individuals, and the elderly. HPIV-3 infections are currently untreatable with licensed therapeutics, and prophylactic and therapeutic options are needed for patients at risk. To complement existing human airway models of HPIV-3 infection and develop an animal model to assess novel intervention strategies, we evaluated infection and transmission of HPIV-3 in ferrets. A well-characterized human clinical isolate (CI) of HPIV-3 engineered to express enhanced green fluorescent protein (rHPIV-3 CI-1-EGFP) was passaged on primary human airway epithelial cells (HAE) or airway organoids (AO) to avoid tissue culture adaptations. rHPIV3 CI-1-EGFP infection was assessed in vitro in ferret AO and in ferrets in vivo. Undifferentiated and differentiated ferret AO cultures supported rHPIV-3 CI-1-EGFP replication, but the ferret primary airway cells from AO were less susceptible and permissive than HAE. In vivo rHPIV-3 CI-1-EGFP replicated in the upper and lower airways of ferrets and targeted respiratory epithelial cells, olfactory epithelial cells, type I pneumocytes, and type II pneumocytes. The infection efficiently induced specific antibody responses. Taken together, ferrets are naturally susceptible to HPIV-3 infection; however, limited replication was observed that led to neither overt clinical signs nor ferret-to-ferret transmission. However, in combination with ferret AO, the ferret model of HPIV-3 infection, tissue tropism, and neutralizing antibodies complements human ex vivo lung models and can be used as a platform for prevention and treatment studies for this important respiratory pathogen. IMPORTANCE HPIV-3 is an important cause of pediatric disease and significantly impacts the elderly. Increasing numbers of immunocompromised patients suffer from HPIV-3 infections, often related to problems with viral clearance. There is a need to model HPIV-3 infections in vitro and in vivo to evaluate novel prophylaxis and treatment options. Currently existing animal models lack the potential for studying animal-to-animal transmission or the effect of immunosuppressive therapy. Here, we describe the use of the ferret model in combination with authentic clinical viruses to further complement human ex vivo models, providing a platform to study approaches to prevent and treat HPIV-3 infection. Although we did not detect ferret-to-ferret transmission in our studies, these studies lay the groundwork for further refinement of the ferret model to immunocompromised ferrets, allowing for studies of severe HPIV-3-associated disease. Such models for preclinical evaluation of prophylaxis and antivirals can contribute to reducing the global health burden of HPIV-3.

Seasonality of Non-SARS, Non-MERS Coronaviruses and the Impact of Meteorological Factors

Background: Seasonality is a characteristic of some respiratory viruses. The aim of our study was to evaluate the seasonality and the potential effects of different meteorological factors on the detection rate of the non-SARS coronavirus detection by PCR. Methods: We performed a retrospective analysis of 12,763 respiratory tract sample results (288 positive and 12,475 negative) for non-SARS, non-MERS coronaviruses (NL63, 229E, OC43, HKU1). The effect of seven single weather factors on the coronavirus detection rate was fitted in a logistic regression model with and without adjusting for other weather factors. Results: Coronavirus infections followed a seasonal pattern peaking from December to March and plunged from July to September. The seasonal effect was less pronounced in immunosuppressed patients compared to immunocompetent patients. Different automatic variable selection processes agreed on selecting the predictors temperature, relative humidity, cloud cover and precipitation as remaining predictors in the multivariable logistic regression model, including all weather factors, with low ambient temperature, low relative humidity, high cloud cover and high precipitation being linked to increased coronavirus detection rates. Conclusions: Coronavirus infections followed a seasonal pattern, which was more pronounced in immunocompetent patients compared to immunosuppressed patients. Several meteorological factors were associated with the coronavirus detection rate. However, when mutually adjusting for all weather factors, only temperature, relative humidity, precipitation and cloud cover contributed independently to predicting the coronavirus detection rate.

Case Study: Prolonged Infectious SARS-CoV-2 Shedding from an Asymptomatic Immunocompromised Individual with Cancer

Long-term severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) shedding was observed from the upper respiratory tract of a female immunocompromised individual with chronic lymphocytic leukemia and acquired hypogammaglobulinemia. Shedding of infectious SARS-CoV-2 was observed up to 70 days, and of genomic and subgenomic RNA up to 105 days, after initial diagnosis. The infection was not cleared after the first treatment with convalescent plasma, suggesting a limited effect on SARS-CoV-2 in the upper respiratory tract of this individual. Several weeks after a second convalescent plasma transfusion, SARS-CoV-2 RNA was no longer detected. We observed marked within-host genomic evolution of SARS-CoV-2 with continuous turnover of dominant viral variants. However, replication kinetics in Vero E6 cells and primary human alveolar epithelial tissues were not affected. Our data indicate that certain immunocompromised individuals may shed infectious virus longer than previously recognized. Detection of subgenomic RNA is recommended in persistently SARS-CoV-2-positive individuals as a proxy for shedding of infectious virus.

SARS-CoV-2 infections in children and young people

Though recent reports link SARS-CoV-2 infections with hyper-inflammatory states in children, most children experience no/mild symptoms, and hospitalization and mortality rates are low in the age group. As symptoms are usually mild and seroconversion occurs at low frequencies, it remains unclear whether children significantly contribute to community transmission. Several hypotheses try to explain age-related differences in disease presentation and severity. Possible reasons for milder presentations in children as compared to adults include frequent contact to seasonal coronaviruses, presence of cross-reactive antibodies, and/or co-clearance with other viruses. Increased expression of ACE2 in young people may facilitate virus infection, while limiting inflammation and reducing the risk of severe disease. Further potential factors include recent vaccinations and a more diverse memory T cell repertoire. This manuscript reviews age-related host factors that may protect children from COVID-19 and complications associated, and addresses the confusion around seropositivity and immunity.

Prolonged viral shedding in an immunocompetent patient with COVID-19

We present a case of COVID-19 in an immunocompetent patient with risk factors for severe disease who recovered after prolonged swab positivity of 61 days postsymptom onset without significant respiratory and organ dysfunction. We discuss the reasons behind her prolonged swab positivity in the context of current SARS-CoV-2 knowledge, document the trend in her inflammatory response and swab results, and discuss the implications swab positivity had on her isolation and recovery.

The Impacts of Antivirals on the Coronavirus Genome Structure and Subsequent Pathogenicity, Virus Fitness and Antiviral Design

With the global threat of SARS-CoV-2, much effort has been focused on treatment and disease control. However, how coronaviruses react to the treatments and whether the surviving viruses have altered their characteristics are also unanswered questions with medical importance. To this end, bovine coronavirus (BCoV), which is in the same genus as SARS-CoV-2, was used as a test model and the findings were as follows. With the treatment of antiviral remdesivir, the selected BCoV variant with an altered genome structure developed resistance, but its pathogenicity was not increased in comparison to that of wild type (wt) BCoV. Under the selection pressure of innate immunity, the genome structure was also altered; however, neither resistance developed nor pathogenicity increased for the selected BCoV variant. Furthermore, both selected BCoV variants showed a better efficiency in adapting to alternative host cells than wt BCoV. In addition, the previously unidentified feature that the spike protein was a common target for mutations under different antiviral treatments might pose a problem for vaccine development because spike protein is a common target for antibody and vaccine designs. The findings derived from this fundamental research may contribute to the disease control and treatments against coronaviruses, including SARS-CoV-2.

Pharmacologic effects of oseltamivir in immunocompromised adult patients as assessed by population PK/PD analysis and drug-disease modelling for dosing regimen optimization

Aim

Pharmacologic effects were analysed to determine a dose recommendation for oseltamivir in immunocompromised (IC) adults with influenza.

Methods

Quantitative clinical pharmacology methods were applied to data from 160 adult IC patients (aged 18‐78 years) from two studies (NV20234, 150 patients; NV25118, 10 patients) who received oseltamivir 75‐200 mg twice daily for up to 10 days. An established population‐pharmacokinetic (PK) model with additional effects on oseltamivir and oseltamivir carboxylate (OC) clearance described the PK characteristics of oseltamivir in IC patients versus otherwise healthy (OwH) patients from previous clinical trials. Estimated PK parameters were used to evaluate exposure‐response relationships for virologic endpoints (time to cessation of viral shedding, viral load measures and treatment‐emergent resistance). A drug‐disease model characterized the viral kinetics of influenza accounting for the effect of OC on viral production.

Results

Oseltamivir clearance was 32.5% lower (95% confidence interval [CI], 26.1‐38.8) and OC clearance was 33.7% lower (95% CI, 23.2‐44.1) in IC versus OwH patients. No notable exposure‐response relationships were identified for exposures higher than those achieved after conventional dose oseltamivir 75 mg, which appeared to be close to the maximum effect of oseltamivir. Simulations of the drug‐disease model predicted that initiating treatment within 48 hours of symptom onset had maximum impact, and a treatment duration of 10 days was favourable over 3‐5 days to limit viral rebound.

Conclusions

Our findings support the use of conventional‐dose oseltamivir 75 mg twice daily for 10 days in the treatment of IC adult patients with influenza.

COVID-19: a primer for the rheumatologist: management of patients and care settings

PURPOSE OF REVIEW

There are currently many unanswered questions surrounding the management of patients with immune-mediated inflammatory diseases during the COVID-19 pandemic and several 'rapid' guidelines have been released, although are subject to be updated and changed in the near future. The purpose of this review is to discuss the approach to management of patients with immune-mediated diseases during the COVID-19 pandemic.

RECENT FINDINGS

At present, there is little evidence to suggest an increased risk of COVID-19 infection or its complications in patients with immune-mediated diseases or associated with conventional or biologic disease modifying antirheumatic drugs; however, glucocorticoid use does appear to have negative associations.

SUMMARY

Currently, conventional and biologic disease modifying antirheumatic drugs can be continued in the absence of SARS-CoV-2 exposure. In the case of exposure, with the exception of hydroxyhcloroquine and sulfasalazine, immunosuppression should be held for 2 weeks. Our recommendations and the guidelines we discuss here are based on C-level recommendations but help provide a framework for how to counsel our patients during this pandemic.

Differential Viral-Host Immune Interactions Associated with Oseltamivir-Resistant H275Y and Wild-Type H1N1 A(pdm09) Influenza Virus Pathogenicity

Oseltamivir is a common therapy against influenza A virus (IAV) infections. The acquisition of oseltamivir resistance (OR) mutations, such as H275Y, hampers viral fitness. However, OR H1N1 viruses have demonstrated the ability to spread throughout different populations. The objective of this work was to compare the fitness of two strains of OR (R6 and R7) containing the H275Y mutation, and a wild-type (F) pandemic influenza A (H1N1) 2009 (pdm09) virus both in vitro and in vivo in mice and to select one OR strain for a comparison with F in ferrets. R6 showed faster replication and pathogenicity than R7 in vitro and in mice. Subsequently, R6 was selected for the fitness comparison with the F strain in ferrets. Ferrets infected with the F virus showed more severe clinical signs, histopathological lung lesions, and viral quantification when compared to OR R6-infected animals. More importantly, differential viral kinetics correlated with differential pro-inflammatory host immune responses in the lungs of infected ferrets, where OR-infected animals developed a protective higher expression of type I IFN and Retinoid acid Inducible Gene I (RIG-I) genes early after infection, resulting in the development of milder disease. These results suggest the presence of early specific viral-host immune interactions relevant in the development of influenza-associated lung pathology.

Influenza-induced thrombocytopenia is dependent on the subtype and sialoglycan receptor and increases with virus pathogenicity

Thrombocytopenia is a common complication of influenza virus infection, and its severity predicts the clinical outcome of critically ill patients. The underlying cause(s) remain incompletely understood. In this study, in patients with an influenza A/H1N1 virus infection, viral load and platelet count correlated inversely during the acute infection phase. We confirmed this finding in a ferret model of influenza virus infection. In these animals, platelet count decreased with the degree of virus pathogenicity varying from 0% in animals infected with the influenza A/H3N2 virus, to 22% in those with the pandemic influenza A/H1N1 virus, up to 62% in animals with a highly pathogenic A/H5N1 virus infection. This thrombocytopenia is associated with virus-containing platelets that circulate in the blood. Uptake of influenza virus particles by platelets requires binding to sialoglycans and results in the removal of sialic acids by the virus neuraminidase, a trigger for hepatic clearance of platelets. We propose the clearance of influenza virus by platelets as a paradigm. These insights clarify the pathophysiology of influenza virus infection and show how severe respiratory infections, including COVID-19, may propagate thrombocytopenia and/or thromboembolic complications.

Characterization of neuraminidase inhibitor-resistant influenza virus isolates from immunocompromised patients in the Republic of Korea

Background

The emergence of influenza viruses resistant to anti-influenza drugs is a threat to global public health. The Korea Centers for Disease Control and Prevention operates the Korea Influenza and Respiratory Viruses Surveillance System (KINRESS) to monitor epidemics of influenza and Severe Acute Respiratory Infection (SARI) to identify mutated influenza viruses affecting drug resistance, pathogenesis, and transmission.

Methods

Oropharyngeal swab samples were collected from KINRESS and SARI during the 2018–2019 season. The specimens confirmed influenza virus using real-time RT-PCR on inoculated MDCK cells. HA and NA sequences of the influenza viruses were analyzed for phylogeny and mutations. Neuraminidase inhibition and hemagglutination inhibition assays were utilized to characterize the isolates.

Results

Two A(H1N1)pdm09 isolates harboring an H275Y substitution in the neuraminidase sequence were detected in patients with acute hematologic cancer. They had prolonged respiratory symptoms, with the virus present in the respiratory tract despite oseltamivir and peramivir treatment. Through the neuraminidase inhibition assay, both viruses were found to be resistant to oseltamivir and peramivir, but not to zanamivir. Although hemagglutinin and neuraminidase phylogenetic analyses suggested that the 2 A(H1N1)pdm09 isolates were not identical, their antigenicity was similar to that of the 2018–19 influenza vaccine virus.

Conclusions

Our data indicate the utility of monitoring influenza-infected immunocompromised patients in general hospitals for the early detection of emerging neuraminidase inhibitor-resistant viruses and maintaining continuous laboratory surveillance of patients with influenza-like illness in sentinel clinics to monitor the spread of such new variants. Finally, characterization of the virus can inform the risk assessment for future epidemics and pandemics caused by drug-resistant influenza viruses.

The antiviral effects of baloxavir marboxil against influenza A virus infection in ferrets

Background

Baloxavir marboxil (BXM), the oral prodrug of baloxavir acid (BXA), greatly reduces virus titers as well as influenza symptoms of uncomplicated influenza in patients.

Objectives

To investigate the pharmacokinetic profiles of BXA and its efficacy against influenza A virus infection in ferrets.

Methods

Ferrets were dosed orally with BXM (10 and 30 mg/kg twice daily for 1 day), oseltamivir phosphate (OSP) (5 mg/kg twice daily for 2 days) or vehicle to measure the antiviral effects of BXM and OSP. The pharmacokinetic parameters of BXA was determined after single oral dosing of BXM.

Results

The maximum plasma concentrations of BXA were observed at 1.50 and 2.00 hours with the two BXM doses, which then declined with an elimination half‐life of 6.91 and 4.44 hours, respectively. BXM at both doses remained detectable in the plasma in ferrets, which may be due to higher stability in liver microsomes. BXM (10 and 30 mg/kg twice daily) treatment at Day 1 post‐infection (p.i.) reduced virus titers by ≥3 log10 of the 50% tissue culture infective doses by Day 2, which was significantly different compared with vehicle or OSP. Body temperature drops over time were significantly greater with BXM than with vehicle or OSP. Significant reduction in virus titers was also demonstrated when BXM was administrated after symptom onset at Day 2 p.i. compared with vehicle and OSP, although body temperature changes largely overlapped between Day 2 and Day 4.

Conclusions

The results highlight the rapid antiviral action of BXM with post‐exposure prophylaxis or therapeutic dosing in ferrets and offer support for further research on prevention of influenza virus infection and transmission.

SARS-CoV-2: The viral shedding vs infectivity dilemma

Since December 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has infected over four million people worldwide. There are multiple reports of prolonged viral shedding in people infected with SARS-CoV-2 but the presence of viral RNA on a test does not necessarily correlate with infectivity. The duration of quarantine required after clinical recovery to definitively prevent transmission is therefore uncertain. In addition, asymptomatic and presymptomatic transmission may occur, and infectivity may be highest early after onset of symptoms, meaning that contact tracing, isolation of exposed individuals and social distancing are essential public health measures to prevent further spread. This review aimed to summarise the evidence around viral shedding vs infectivity of SARS-CoV-2.

•

Viral shedding has been demonstrated up to 63 days after symptom onset.

•

The distinction between viral shedding and infectivity is important for the development of quarantine guidelines and policy.

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There is an earlier peak in viral load in SARS-CoV-2 than seen in SARS.

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Quantitative viral loads are higher in the nose than the throat.

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It is likely that asymptomatic and presymptomatic transmission is occurring.

Limited Utility of Serology and Heterophile Test in the Early Diagnosis of Epstein-Barr Virus Mononucleosis in a Child after Renal Transplantation

Background: Epstein-Barr virus (EBV) infection is associated with significant morbidity and mortality in renal transplant (RT) recipients. The spectrum of illness ranges from infectious mononucleosis (IM) to post-transplant lymphoproliferative disorder (PTLD). In association with clinical signs and symptoms, virus-specific serology and heterophile antibody tests are widely used in confirming the diagnosis of IM in the general population. However, these tests may have a limited role in immunosuppressed RT recipients from seropositive donor, especially in children who were EBV-seronegative prior to the transplant. The aim of this study is to evaluate the utility of these tests in the early diagnosis of IM in this subset of patients. Methods: This is a case study with a review of literature. Results: Here, we present a 14-year-old male with hemophilia B who presented with fever, fatigue, sore throat, palatal petechial rash, exudative tonsillitis and cervical lymphadenopathy 3 months post-RT. He was EBV seronegative prior to RT and received a deceased donor kidney transplant from a seropositive donor. Induction was done with Thymoglobulin and maintenance immunosuppression consisted of tacrolimus and mycophenolate. Initial heterophile antibody test (monospot) was negative, but became positive at 5 months and remained positive at 9 months follow-up post-RT. EBV viral capsid antigens (VCA) IgM and IgG, early antigen (EA) and nuclear antigen (EBNA) were all negative at the time of presentation. VCA IgM and IgG both became positive at 5 months and peaked at 9 months follow-up, however the EA and EBNA remained negative. EBV viral load as measured by polymerase chain reaction (PCR) was negative for the first 3 months post-RT but became positive at presentation, peaked at 6 months and started declining thereafter. Peripheral blood smear examination showed no absolute and atypical lymphocytosis. Cytomegalovirus PCR in the blood and throat culture for streptococcus were negative. There was no splenomegaly. He was managed conservatively with intravenous fluids, bed rest, antipyretics and reduction of immunosuppression. Conclusions: EBV serological markers have a limited role in the early diagnosis of EBV-IM following RT in prior seronegative children. Initial heterophile antibody test may also be negative, and hence a repeat test may be necessary. Once becoming positive, the VCA IgM may remain persistently elevated for prolonged duration. In addition to the suppressed cellular immunity secondary to immunosuppression, humoral response to viral infections is also delayed in transplant recipients, especially in the early transplant period. Hence, routine monitoring with PCR is superior to serology in diagnosing IM early and monitoring the EBV infection post-RT for timely evaluation and management.

Passive immune therapy and other immunomodulatory agents for the treatment of severe influenza: Systematic review and meta-analysis

BACKGROUND

A range of immunomodulatory therapies have been proposed as adjuncts to conventional antivirals to suppress harmful inflammation during severe influenza infection. We conducted a systematic review to assess available data of the effect of adjunctive non-corticosteroid immunomodulatory therapy and potential adverse effects.

METHOD

We searched MEDLINE, Embase, Web of Science and clinical trial databases for published and unpublished studies, and screened the references of included articles. We included RCTs, quasi-RCTs and observational studies of virologically confirmed influenza infections in hospitalised patients. We did not restrict studies by language of publication, influenza type/subtype or age of participants. Where possible, we pooled estimates of effect using random-effects meta-analysis models.

RESULTS

We identified 11 eligible studies for inclusion: five studies (4 RCTs and 1 observational; 693 individuals) of passive immune therapy; four studies (3 RCTs and 1 observational; 1120 individuals) of macrolides and/or non-steroidal anti-inflammatory drugs (NSAIDs), one RCT of mTOR inhibitors (38 individuals), and one RCT of statin therapy (116 individuals). Meta-analysis of RCTs of passive immune therapy indicated no significant reduction in mortality (OR 0.84, 0.37-1.90), but better clinical outcomes at Day 7 (OR 1.42, 1.05-1.92). There was a significant reduction in mortality associated with macrolides and/or NSAIDs (OR 0.28; 0.10-0.77).

CONCLUSIONS

Passive immune therapy is unlikely to offer substantial mortality benefit in treatment of severe seasonal influenza, but may improve clinical outcomes. The effect of other immunomodulatory agents is uncertain, but promising. There is a need for high-quality RCTs with sufficient statistical power to address this evidence gap.

Safety, Resistance, and Efficacy Results from a Phase IIIb Study of Conventional- and Double-Dose Oseltamivir Regimens for Treatment of Influenza in Immunocompromised Patients

INTRODUCTION

Immunocompromised patients infected with influenza exhibit prolonged viral shedding and higher risk of resistance. Optimized treatment strategies are needed to reduce the risk of antiviral resistance. This phase IIIb, randomized, double-blind study (NCT00545532) evaluated conventional-dose or double-dose oseltamivir for the treatment of influenza in immunocompromised patients.

METHODS

Patients with primary or secondary immunodeficiency and influenza infection were randomized 1:1 to receive conventional-dose oseltamivir (75 mg adolescents/adults [≥ 13 years]; 30-75 mg by body weight in children [1-12 years]) or double-dose oseltamivir (150 or 60-150 mg, respectively), twice daily for an extended period of 10 days. Nasal/throat swabs were taken for virology assessments at all study visits. Co-primary endpoints were safety/tolerability and viral resistance. Secondary endpoints included time to symptom alleviation (TTSA) and time to cessation of viral shedding (TTCVS).

RESULTS

Of 228 patients enrolled between February 2008 and May 2017, 215 (199 adults) were evaluable for safety, 167 (151 adults) for efficacy, and 152 (138 adults) for resistance. Fewer patients experienced an adverse event (AE) in the conventional-dose group (50.5%) versus the double-dose group (59.1%). The most frequently reported AEs were nausea, diarrhea, vomiting, and headache. Fifteen patients had post-baseline resistance, more commonly in the conventional-dose group (n  = 12) than in the double-dose group (n  = 3). In adults, median TTSA was similar between arms, while median TTCVS was longer with conventional dosing.

CONCLUSIONS

Oseltamivir was well tolerated, with a trend toward better safety/tolerability for conventional dosing versus double dosing. Resistance rates were higher with conventional dosing in this immunocompromised patient population.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00545532.

FUNDING

F. Hoffmann-La Roche Ltd.

A Guide for the Use of the Ferret Model for Influenza Virus Infection

As influenza viruses continue to jump species barriers to cause human infection, assessments of disease severity and viral replication kinetics in vivo provide crucial information for public health professionals. The ferret model is a valuable resource for evaluating influenza virus pathogenicity; thus, understanding the most effective techniques for sample collection and usage, as well as the full spectrum of attainable data after experimental inoculation in this species, is paramount. This is especially true for scheduled necropsy of virus-infected ferrets, a standard component in evaluation of influenza virus pathogenicity, as necropsy findings can provide important information regarding disease severity and pathogenicity that is not otherwise available from the live animal. In this review, we describe the range of influenza viruses assessed in ferrets, the measures of experimental disease severity in this model, and optimal sample collection during necropsy of virus-infected ferrets. Collectively, this information is critical for assessing systemic involvement after influenza virus infection in mammals.

Community-Acquired Respiratory Viruses in Transplant Patients: Diversity, Impact, Unmet Clinical Needs

Patients undergoing solid-organ transplantation (SOT) or allogeneic hematopoietic cell transplantation (HCT) are at increased risk for infectious complications. Community-acquired respiratory viruses (CARVs) pose a particular challenge due to the frequent exposure pre-, peri-, and posttransplantation. Although influenza A and B viruses have a top priority regarding prevention and treatment, recent molecular diagnostic tests detecting an array of other CARVs in real time have dramatically expanded our knowledge about the epidemiology, diversity, and impact of CARV infections in the general population and in allogeneic HCT and SOT patients. These data have demonstrated that non-influenza CARVs independently contribute to morbidity and mortality of transplant patients. However, effective vaccination and antiviral treatment is only emerging for non-influenza CARVs, placing emphasis on infection control and supportive measures. Here, we review the current knowledge about CARVs in SOT and allogeneic HCT patients to better define the magnitude of this unmet clinical need and to discuss some of the lessons learned from human influenza virus, respiratory syncytial virus, parainfluenzavirus, rhinovirus, coronavirus, adenovirus, and bocavirus regarding diagnosis, prevention, and treatment.

Baloxavir marboxil, a novel cap-dependent endonuclease inhibitor potently suppresses influenza virus replication and represents therapeutic effects in both immunocompetent and immunocompromised mouse models

Baloxavir marboxil (BXM) is an orally available small molecule inhibitor of cap-dependent endonuclease (CEN), an essential enzyme in the initiation of mRNA synthesis of influenza viruses. In the present study, we evaluated the efficacy of BXM against influenza virus infection in mouse models. Single-day oral administration of BXM completely prevented mortality due to infection with influenza A and B virus in mice. Moreover, 5-day repeated administration of BXM was more effective for reducing mortality and body weight loss in mice infected with influenza A virus than oseltamivir phosphate (OSP), even when the treatment was delayed up to 96 hours post infection (p.i.). Notably, administration of BXM, starting at 72 hours p.i. led to significant decrease in virus titers of >2-log₁₀ reduction compared to the vehicle control within 24 hours after administration. Virus reduction in the lung was significantly greater than that observed with OSP. In addition, profound and sustained reduction of virus titer was observed in the immunocompromised mouse model without emergence of variants possessing treatment-emergent amino acid substitutions in the target protein. In our immunocompetent and immunocompromised mouse models, delayed treatment with BXM resulted in rapid and potent reduction in infectious virus titer and prevention of signs of influenza infection, suggesting that BXM could extend the therapeutic window for patients with influenza virus infection regardless of the host immune status.

Animal Models for Influenza A Virus Infection Incorporating the Involvement of Innate Host Defenses: Enhanced Translational Value of the Porcine Model

Influenza is a viral respiratory disease having a major impact on public health. Influenza A virus (IAV) usually causes mild transitory disease in humans. However, in specific groups of individuals such as severely obese, the elderly, and individuals with underlying inflammatory conditions, IAV can cause severe illness or death. In this review, relevant small and large animal models for human IAV infection, including the pig, ferret, and mouse, are discussed. The focus is on the pig as a large animal model for human IAV infection as well as on the associated innate immune response. Pigs are natural hosts for the same IAV subtypes as humans, they develop clinical disease mirroring human symptoms, they have similar lung anatomy, and their respiratory physiology and immune responses to IAV infection are remarkably similar to what is observed in humans. The pig model shows high face and target validity for human IAV infection, making it suitable for modeling many aspects of influenza, including increased risk of severe disease and impaired vaccine response due to underlying pathologies such as low-grade inflammation. Comparative analysis of proteins involved in viral pattern recognition, interferon responses, and regulation of interferon-stimulated genes reveals a significantly higher degree of similarity between pig, ferret, and human compared with mice. It is concluded that the pig is a promising animal model displaying substantial human translational value with the ability to provide essential insights into IAV infection, pathogenesis, and immunity.

Combination Therapy with Oseltamivir and Favipiravir Delays Mortality but Does Not Prevent Oseltamivir Resistance in Immunodeficient Mice Infected with Pandemic A(H1N1) Influenza Virus

Immunosuppressed individuals can shed influenza virus for prolonged periods of time, leading to the frequent emergence of antiviral resistance. We evaluated the benefits of oseltamivir and favipiravir combination therapy compared to single antiviral agents and monitored the emergence of drug-resistant variants in a pharmacologically immunosuppressed mouse model infected with the A(H1N1) pandemic influenza virus. C57BL/6 mice were immunosuppressed with cyclophosphamide and infected with a lethal dose of pandemic influenza A(H1N1) virus. Forty-eight hours post-infection, mice were treated with oseltamivir (20 mg/kg), favipiravir (20 or 50 mg/kg) or both agents BID for 5 or 10 days. Body weight losses, survival rates, lung viral titers, cytokine levels and emergence of resistant viruses were evaluated. Treatment of immunosuppressed mice with high (50 mg/kg) but not low (20 mg/kg) doses of favipiravir in combination with oseltamivir (20 mg/kg) significantly delayed mortality and reduced lung viral titers compared to treatment with a single drug regimen with oseltamivir but did not prevent the emergence of oseltamivir-resistant H275Y neuraminidase variants. Combination therapy with oseltamivir and favipiravir should be considered for evaluation in clinical trials.