Treatment of respiratory syncytial virus infection with recombinant interferon alfa-2a

Broad-Spectrum Antiviral Activity of Influenza A Defective Interfering Particles against Respiratory Syncytial, Yellow Fever, and Zika Virus Replication In Vitro

New broadly acting and readily available antiviral agents are needed to combat existing and emerging viruses. Defective interfering particles (DIPs) of influenza A virus (IAV) are regarded as promising options for the prevention and treatment of IAV infections. Interestingly, IAV DIPs also inhibit unrelated viral infections by stimulating antiviral innate immunity. Here, we tested the ability of IAV DIPs to suppress respiratory syncytial, yellow fever and Zika virus infections in vitro. In human lung (A549) cells, IAV DIP co-infection inhibited the replication and spread of all three viruses. In contrast, we observed no antiviral activity in Vero cells, which are deficient in the production of interferon (IFN), demonstrating its importance for the antiviral effect. Further, in A549 cells, we observed an enhanced type-I and type-III IFN response upon co-infection that appears to explain the antiviral potential of IAV DIPs. Finally, a lack of antiviral activity in the presence of the Janus kinase 1/2 (JAK1/2) inhibitor ruxolitinib was detected. This revealed a dependency of the antiviral activity on the JAK/signal transducers and activators of transcription (STAT) signaling pathway. Overall, this study supports the notion that IAV DIPs may be used as broad-spectrum antivirals to treat infections with a variety of IFN-sensitive viruses, particularly respiratory viruses.

Interferons-Implications in the Immune Response to Respiratory Viruses

Interferons (IFN) are an assemblage of signaling proteins made and released by various host cells in response to stimuli, including viruses. Respiratory syncytial virus (RSV), influenza virus, and SARS-CoV-2 are major causes of respiratory disease that induce or antagonize IFN responses depending on various factors. In this review, the role and function of type I, II, and III IFN responses to respiratory virus infections are considered. In addition, the role of the viral proteins in modifying anti-viral immunity is noted, as are the specific IFN responses that underly the correlates of immunity and protection from disease.

Anti-G protein antibodies targeting the RSV G protein CX3C chemokine region improve the interferon response

Background

Respiratory syncytial virus (RSV) is a poor inducer of antiviral interferon (IFN) responses which result in incomplete immunity and RSV disease. Several RSV proteins alter antiviral responses, including the non-structural proteins (NS1, NS2) and the major viral surface proteins, that is, fusion (F) and attachment (G) proteins. The G protein modifies the host immune response to infection linked in part through a CX3 C chemokine motif. Anti-G protein monoclonal antibodies (mAbs), that is, clones 3D3 and 2D10 that target the G protein CX3C chemokine motif can neutralize RSV and inhibit G protein-CX3CR1 mediated chemotaxis.

Objectives

Determine how monoclonal antibodies against the RSV F and G proteins modify the type I and III IFN responses to RSV infection.

Design

As the G protein CX3 C motif is implicated in IFN antagonism, we evaluated two mAbs that block G protein CX3C-CX3CR1 interaction and compared responses to isotype mAb control using a functional cellular assay and mouse model.

Methods

Mouse lung epithelial cells (MLE-15 cells) and BALB/c mice were infected with RSV Line19 F following prophylactic mAb treatment. Cell supernatant or bronchoalveolar lavage fluid (BALF) were assayed for types I and III IFNs. Cells were interrogated for changes in IFN-related gene expression.

Results

Treatment with an anti-G protein mAb (3D3) resulted in improved IFN responses compared with isotype control following infection with RSV, partially independently of neutralization, and this was linked to upregulated SOCS1 expression.

Conclusions

These findings show that anti-G protein antibodies improve the protective early antiviral response, which has important implications for vaccine and therapeutic design.

Plain Language Summary

RSV is a leading cause of respiratory disease in infants and the elderly. The only Food and Drug Administration-approved prophylactic treatment is limited to an anti-F protein monoclonal antibody (mAb), that is, palivizumab which has modest efficacy against RSV disease. Accumulating evidence suggests that targeting the RSV attachment (G) protein may provide improved protection from RSV disease. It is known that the G protein is an IFN antagonist, and IFN has been shown to be protective against RSV disease. In this study, we compared IFN responses in mouse lung epithelial (MLE-15) cells and in mice infected with RSV Line19 F treated with anti-G protein or anti-F protein mAbs. The levels of type I and III IFNs were determined. Anti-G protein mAbs improved the levels of IFNs compared with isotype-treated controls. These findings support the concept that anti-G protein mAbs mediate improved IFN responses against RSV disease, which may enable improved treatment of RSV infections.

Treatment of respiratory viral infections through inhalation therapeutics: Challenges and opportunities

Respiratory viral infections are the leading cause of death worldwide. The current pandemic of coronavirus infection (COVID-19) challenged human beings for the treatment and prevention of this respiratory viral infection since its outbreak in 2019. Despite advancements in the medical field, scientists were helpless to give timely treatment and protection against this viral infection. Several drugs, whether antiviral or not, were given to the patients to reduce mortality and morbidity rate. Vaccines from various pharmaceutical manufacturers are now available to give immunization against covid-19. Still, coronavirus is continuously affecting people in the form of variants after mutation. Each new variant increases the infection risk and forces scientists to develop some innovative and effective treatments for this infection. The virus uses the host's cell machinery to grow and multiply in numbers. Therefore, scientists are facing challenges to develop antivirals that stop the virus without damaging the host cells too. The production of suitable antivirals or vaccines for the new virus would take several months, allowing the strain to cause severe damage to life. Inhalable formulation facilitates the delivery of medicinal products directly to the respiratory system without causing unwanted side effects associated with systemic absorption. Scientists are focusing on developing an inhaled version of the existing antivirals for the treatment of respiratory infections. This review focused on the inhalable formulations of antiviral agents in various respiratory viral infections including the ongoing covid-19 pandemic and important findings of the clinical studies. We also reviewed repurposed drugs that have been given through inhalation in covid-19 infection.

Immunopathology of RSV: An Updated Review

RSV is a leading cause of respiratory tract disease in infants and the elderly. RSV has limited therapeutic interventions and no FDA-approved vaccine. Gaps in our understanding of virus-host interactions and immunity contribute to the lack of biological countermeasures. This review updates the current understanding of RSV immunity and immunopathology with a focus on interferon responses, animal modeling, and correlates of protection.

Transcriptome of airway neutrophils reveals an interferon response in life-threatening respiratory syncytial virus infection

BACKGROUND

Neutrophils are the most abundant cell type infiltrating the airways during severe respiratory syncytial virus (RSV) infection. Their exact role in disease pathophysiology remains enigmatic. Therefore, we determined genome-wide RNA expression profiles of local and systemic neutrophils in RSV bronchiolitis to provide further insight into local neutrophil biology.

METHODS

We performed a single-center analysis, in 16 infants, admitted to the pediatric intensive care unit with severe RSV bronchiolitis. Neutrophils were isolated from blood and tracheobronchial aspirates (sputum). After low input RNA sequencing, differential expression of genes was determined followed by gene set analysis.

RESULTS

Paired transcriptomic analysis of airway versus blood neutrophils showed an inflammatory phenotype, characterized by NF-kB signaling and upregulated expression of IL-6 and interferon pathways. We observed distinct expression of neutrophil activation genes (TNFSF13B, FCER1G).

DISCUSSION

Our data indicate that airway neutrophils regulate their function at the transcriptional level in response to viral infection. It also suggests that local interferon drives the neutrophil response of severe RSV bronchiolitis.

Human Type I Interferon Antiviral Effects in Respiratory and Reemerging Viral Infections

Type I interferons (IFN-I) are a group of related proteins that help regulate the activity of the immune system and play a key role in host defense against viral infections. Upon infection, the IFN-I are rapidly secreted and induce a wide range of effects that not only act upon innate immune cells but also modulate the adaptive immune system. While IFN-I and many IFN stimulated genes are well-known for their protective antiviral role, recent studies have associated them with potential pathogenic functions. In this review, we summarize the current knowledge regarding the complex effects of human IFN-I responses in respiratory as well as reemerging flavivirus infections of public health significance and the molecular mechanisms by which viral proteins antagonize the establishment of an antiviral host defense. Antiviral effects and immune modulation of IFN-stimulated genes is discussed in resisting and controlling pathogens. Understanding the mechanisms of these processes will be crucial in determining how viral replication can be effectively controlled and in developing safe and effective vaccines and novel therapeutic strategies.

Function and Modulation of Type I Interferons during Respiratory Syncytial Virus Infection

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory infections in infants and young children, accounting for an estimated 3 million hospitalizations annually worldwide. Despite the major health burden, there is currently no licensed RSV vaccine. RSV is recognized by a range of cellular receptors including both toll-like receptors (TLR) and retinoic acid-inducible gene-I-like receptors (RIG-I). This interaction initiates signaling through mitochondrial antiviral signaling (MAVS) and interferon regulatory factor (IRF) proteins, resulting in the induction of type I interferons (IFN). Early viral control is mediated by either IFN-α or IFN-β signaling through the IFN receptor (IFNAR), inducing the production of antiviral interferon-stimulating genes (ISGs). Type I IFNs also initiate the early production of proinflammatory cytokines including interleukin 6 (IL-6), tumor necrosis factor (TNF), and IFN-γ. Type I IFN levels correlate with age, and inadequate production may be a critical factor in facilitating the increased RSV disease severity observed in infants. Here, we review the current literature on the function of type I IFNs in RSV pathogenesis, as well as their involvement in the differential immune responses observed in infants and adults.

Role of Type I Interferon (IFN) in the Respiratory Syncytial Virus (RSV) Immune Response and Disease Severity

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract disease in children <2 years of age. Increased morbidity and mortality have been reported in high-risk patients, such as premature infants, patients with cardiac disease, and severely immune compromised patients. Severe disease is associated with the virulence of the virus as well as host factors specifically including the innate immune response. The role of type I interferons (IFNs) in the response to RSV infection is important in regulating the rate of virus clearance and in directing the character of the immune response, which is normally associated with protection and less severe disease. Two RSV non-structural proteins, NS1 and NS2, as well as the envelope G glycoprotein are known to suppress type I IFN production and a robust type I IFN response to RSV does not occur in human infants or neonatal mouse models of RSV infection. Additionally, presence of type I IFNs are associated with mild symptoms in infants and administration of IFN-α prior to infection of neonatal mice with RSV reduces immunopathology. This evidence has driven RSV prophylaxis and therapeutic efforts to consider strategies for enhancing type I IFN production.

Enteric helminth-induced type I interferon signaling protects against pulmonary virus infection through interaction with the microbiota

BACKGROUND

Helminth parasites have been reported to have beneficial immunomodulatory effects in patients with allergic and autoimmune conditions and detrimental consequences in patients with tuberculosis and some viral infections. Their role in coinfection with respiratory viruses is not clear.

OBJECTIVE

Here we investigated the effects of strictly enteric helminth infection with Heligmosomoides polygyrus on respiratory syncytial virus (RSV) infection in a mouse model.

METHODS

A murine helminth/RSV coinfection model was developed. Mice were infected by means of oral gavage with 200 stage 3 H polygyrus larvae. Ten days later, mice were infected intranasally with either RSV or UV-inactivated RSV.

RESULTS

H polygyrus-infected mice showed significantly less disease and pulmonary inflammation after RSV infection associated with reduced viral load. Adaptive immune responses, including T_H2 responses, were not essential because protection against RSV was maintained in Rag1^-/- and Il4rα^-/- mice. Importantly, H polygyrus infection upregulated expression of type I interferons and interferon-stimulated genes in both the duodenum and lung, and its protective effects were lost in both Ifnar1^-/- and germ-free mice, revealing essential roles for type I interferon signaling and microbiota in H polygyrus-induced protection against RSV.

CONCLUSION

These data demonstrate that a strictly enteric helminth infection can have remote protective antiviral effects in the lung through induction of a microbiota-dependent type I interferon response.

ISG15 Is Upregulated in Respiratory Syncytial Virus Infection and Reduces Virus Growth through Protein ISGylation

Human respiratory syncytial virus (RSV), for which neither a vaccine nor an effective therapeutic treatment is currently available, is the leading cause of severe lower respiratory tract infections in children. Interferon-stimulated gene 15 (ISG15) is a ubiquitin-like protein that is highly increased during viral infections and has been reported to have an antiviral or a proviral activity, depending on the virus. Previous studies from our laboratory demonstrated strong ISG15 upregulation during RSV infection in vitro. In this study, an in-depth analysis of the role of ISG15 in RSV infection is presented. ISG15 overexpression and small interfering RNA (siRNA)-silencing experiments, along with ISG15 knockout (ISG15(-/-)) cells, revealed an anti-RSV effect of the molecule. Conjugation inhibition assays demonstrated that ISG15 exerts its antiviral activity via protein ISGylation. This antiviral activity requires high levels of ISG15 to be present in the cells before RSV infection. Finally, ISG15 is also upregulated in human respiratory pseudostratified epithelia and in nasopharyngeal washes from infants infected with RSV, pointing to a possible antiviral role of the molecule in vivo. These results advance our understanding of the innate immune response elicited by RSV and open new possibilities to control infections by the virus.

IMPORTANCE

At present, no vaccine or effective treatment for human respiratory syncytial virus (RSV) is available. This study shows that interferon-stimulated gene 15 (ISG15) lowers RSV growth through protein ISGylation. In addition, ISG15 accumulation highly correlates with the RSV load in nasopharyngeal washes from children, indicating that ISG15 may also have an antiviral role in vivo. These results improve our understanding of the innate immune response to RSV and identify ISG15 as a potential target for virus control.

Inhaled anti-infective chemotherapy for respiratory tract infections: successes, challenges and the road ahead

One of the most common causes of illnesses in humans is from respiratory tract infections caused by bacterial, viral or fungal pathogens. Inhaled anti-infective drugs are crucial for the prophylaxis and treatment of respiratory tract infections. The benefit of anti-infective drug delivery via inhalation is that it affords delivery of sufficient therapeutic dosages directly to the primary site of infection, while minimizing the risks of systemic toxicity or avoiding potential suboptimal pharmacokinetics/pharmacodynamics associated with systemic drug exposure. This review provides an up-to-date treatise of approved and novel developmental inhaled anti-infective agents, with particular attention to effective strategies for their use, pulmonary pharmacokinetic properties and safety.

Limited type I interferons and plasmacytoid dendritic cells during neonatal respiratory syncytial virus infection permit immunopathogenesis upon reinfection

Respiratory syncytial virus (RSV) infection is the number one cause of bronchiolitis in infants, yet no vaccines are available because of a lack of knowledge of the infant immune system. Using a neonatal mouse model, we previously revealed that mice initially infected with RSV as neonates develop Th2-biased immunopathophysiologies during reinfection, and we demonstrated a role for enhanced interleukin-4 receptor α (IL-4Rα) expression on T helper cells in these responses. Here we show that RSV infection in neonates induced limited type I interferon (IFN) and plasmacytoid dendritic cell (pDC) responses. IFN alpha (IFN-α) treatment or adoptive transfer of adult pDCs capable of inducing IFN-α prior to neonatal RSV infection decreased Th2-biased immunopathogenesis during reinfection. A reduced viral load and downregulation of IL-4Rα on Th2 cells were observed in IFN-α-treated neonatal mice, suggesting dual mechanisms of action.

IMPORTANCE

Respiratory syncytial virus (RSV) is the most significant cause of lower respiratory tract infection in infancy worldwide. Despite the dire need, we have failed to produce efficacious RSV vaccines or therapeutics. Part of the reason for this failure is our lack of understanding of how RSV interacts with the infant immune system to suppress the development of protective immunity. In the study described in the present paper, we used a neonatal mouse model, which more closely mimics human infants, to study the role of the innate immune system, particularly type I interferons (IFNs) and plasmacytoid dendritic cells (pDCs), in the pathogenesis of RSV infection. RSV infection in neonates induced limited type I IFN and pDC responses. IFN-α treatment or adoptive transfer of adult pDCs capable of producing IFN-α prior to neonatal RSV infection decreased Th2-biased immunopathogenesis during reinfection. These data suggest that IFN-α is a promising target for future RSV vaccine design.

Opposing roles of membrane and soluble forms of the receptor for advanced glycation end products in primary respiratory syncytial virus infection

Respiratory syncytial virus (RSV), a common respiratory pathogen in infants and the older population, causes pulmonary inflammation and airway occlusion that leads to impairment of lung function. Here, we have established a role for receptor for advanced glycation end products (RAGE) in RSV infection. RAGE-deficient (ager(-/-)) mice were protected from RSV-induced weight loss and inflammation. This protection correlated with an early increase in type I interferons, later decreases in proinflammatory cytokines, and a reduction in viral load. To assess the contribution of soluble RAGE (sRAGE) to RSV-induced disease, wild-type and ager(-/-) mice were given doses of sRAGE following RSV infection. Of interest, sRAGE treatment prevented RSV-induced weight loss and neutrophilic inflammation to a degree similar to that observed in ager(-/-) mice. Our work further elucidates the roles of RAGE in the pathogenesis of respiratory infections and highlights the opposing roles of membrane and sRAGE in modulating the host response to RSV infection.

A randomized controlled trial of low-dose recombinant human interferons alpha-2b nasal spray to prevent acute viral respiratory infections in military recruits

The military population has a high disease burden of acute viral respiratory infections in China. To assess the efficacy and safety of a low-dose recombinant human interferon α-2b (rIFNα-2b) nasal spray in preventing acute viral respiratory infections in military population, we performed this randomized controlled trial. The results showed that application of the rIFNα-2b nasal spray had the benefits in prevention of infections caused by influenza A virus, influenza B virus parainfluenza viruses 1–3 and adenovirus species B. However, no benefit was seen in preventing respiratory syncytial virus. No severe adverse events were reported. Therefore, the rIFNα-2b nasal spray was effective and well tolerated for preventing common viral respiratory infections in the military recruits.

Activity and regulation of alpha interferon in respiratory syncytial virus and human metapneumovirus experimental infections

Respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) cause a similar spectrum of respiratory infections in humans. Classified within the Paramyxoviridae family, Pneumovirinae subfamily, RSV and hMPV present a significant degree of divergence in genome constellation, organization, and protein sequences. RSV has been reported to be a poor inducer of alpha/beta interferons (IFN-alpha/beta) and partially resistant to its antiviral activity. The nature of the innate immune response to hMPV is currently unknown. Herein, an experimental mouse model was used to investigate the interplay between RSV and hMPV infections and IFN-alpha in the airways. RSV-infected BALB/c mice treated intranasally with either poly-ICLC, a potent inducer of IFN-alpha, or directly with recombinant IFN-alpha showed significantly reduced lung viral titers, inflammation, and clinical disease than untreated controls. However, RSV was significantly less sensitive to the antiviral activity of IFN-alpha than hMPV. Similarly, when the ability to directly induce IFN-alpha production was assessed, RSV was clearly a weaker inducer of IFN-alpha than hMPV, as shown by both kinetics and the absolute amount of IFN-alpha secreted into the bronchoalveolar lavage. To further investigate the putative inhibitory effect of these viruses on IFN-alpha production, mice were infected for 48 h prior to treatment with poly-ICLC or a specific Toll-like receptor 9 ligand, CpG oligodeoxynucleotides. Strikingly, both poly-ICLC- and CpG-mediated IFN-alpha production was abrogated by either RSV or MPV infection. These results suggest that a complex interplay between virus-specific and host-mediated responses regulates IFN-alpha in the lung during infection by members of the Pneumovirinae family.

Development of a real-time RT-PCR assay for detection and quantitation of parainfluenza virus 3

A TaqMan-based real-time RT-PCR assay was developed to detect and quantify human parainfluenza virus 3 (PIV3). Two sets of primer-probe pairs were designed based on the nucleotide (nt) sequence of the nucleocapsid (N) gene. The primer-probe pairs were derived from the 3' end of the N gene (set 1) and the 5' region of the gene (set 2), respectively. Using real-time RT-PCR, the sensitivity of set 1 was determined to be about 9 copies of PIV3 genome, while the sensitivity of set 2 was about 93 copies of PIV3 genome. Set 1 was chosen for subsequent experiments. This primer-probe pair detected PIV3, but not any of several other respiratory viruses, indicating that the assay is PIV3 specific. For clinical evaluation, the assay was employed to test 80 nasopharyngeal aspirates from children with respiratory symptoms. The results confirmed the presence of PIV3 in 12 specimens previously identified as positive by culture confirmation, and showed all of which contained more than 100 copies of PIV3 genome. In addition, the method also detected PIV3 genomes in specimens found negative by culture confirmation, indicating the value of this RT-PCR assay. These data thus demonstrate the application of the real-time RT-PCR assay for the detection and quantification of PIV3 in clinical specimens.

New developments in the treatment of viral respiratory tract infections

Most respiratory tract infections are viral in origin, yet until recently only a few effective therapies had been developed. This reflected the large number of causative agents and the generally benign course of most infections. However, increasing numbers of serious respiratory infections have been seen in recent years, due to the rising prevalence of immunodeficient patients and the emergence of previously unrecognised pathogens. Better understanding of viral structure, and novel methods of drug design and discovery are leading to the development of potentially valuable new treatments, particularly for influenza and respiratory syncytial virus infection.

Current treatment for acute viral bronchiolitis in infants

This paper provides an update and critical review of available data on the treatment of acute viral bronchiolitis in previously healthy infants, with special focus on new or promising therapies. The main potential benefits of medical assistance in these patients reside in the careful monitoring of their clinical status, the maintenance of adequate hydration and oxygenation, the preservation of the airway opened and cleared of secretions and the option to perform parental education. There is no convincing evidence that any other form of therapy will reliably provide beneficial effects in infants with bronchiolitis and currently, any treatment beyond supportive care should be prescribed on a case-by-case basis with watchful appraisal of its effects. Therapies such as ribavirin, IFN, vitamin A, antibiotics, mist therapy or anticholinergics, have not demonstrated any measurable clinical effect. Several studies and meta-analyses with beta(2)-agonists and corticosteroids have failed to show any benefit of significant extent, however, physicians keep favouring their use. Presently, adrenaline has received rather consistent support from clinical trials but it is not yet widely prescribed. There are other therapeutic strategies, for instance, heliox, hypertonic saline, noninvasive ventilation, physical therapy techniques, thickened feeds or palivizumab that have shown promising potential benefits, but evidence supporting its use is still limited and further studies should be warranted. In the meantime, infants with acute viral bronchiolitis should be treated following evidence-based clinical practice guidelines, keeping the patient central in the process and being sensitive to social, cultural and familiar influences on their treatment strategy.

Simultaneous detection, subgrouping, and quantitation of respiratory syncytial virus A and B by real-time PCR

Timely diagnosis of respiratory syncytial virus (RSV) infection is critical for appropriate treatment of lower respiratory infection in young children. To facilitate diagnosis, we developed a rapid, specific, and sensitive TaqMan PCR method for detection of RSV A and RSV B. Two sets of primer-probe pairs were selected from the nucleotide sequences encoding the nucleocapsid protein--one targeting RSV A and the other targeting RSV B. The specificity of the TaqMan reverse transcription-PCR assay was evaluated by testing each primer-probe pair against various viruses derived from laboratory virus stocks, as well as clinical respiratory specimens. Fluorescent signals were observed only in the presence of RSV A and/or RSV B. The sensitivity of our quantitative PCR assay was determined on the basis of PFU and virus particle counts. The resulting assay sensitivity was found to be 0.023 PFU, or two copies of viral RNA, for RSV A and 0.018 PFU, or nine copies of viral RNA, for RSV B. This quantitative TaqMan PCR assay was utilized to diagnose 175 nasopharyngeal aspirates obtained from children in Hong Kong with respiratory symptoms during the winter of 2000 and 2001. Among these specimens, TaqMan PCR detected 36 RSV-positive samples, 10 of which were identified as RSV A and 26 of which were identified as RSV B, whereas culture confirmation identified 21 RSV-positive specimens and immunofluorescence identified 32 RSV-positive specimens, all of which were among those identified by PCR. The results confirmed the accuracy of our TaqMan PCR assay and demonstrated its improved sensitivity versus classical methods.

The quest for an efficacious antiviral for respiratory syncytial virus

Respiratory syncytial virus (RSV) continues as an emerging infectious disease not only among infants and children, but also for the immune-suppressed, hospitalized and the elderly. To date, ribavirin (Virazole) remains the only therapeutic agent approved for the treatment of RSV. The prophylactic administration of palivizumab is problematic and costly. The quest for an efficacious RSV antiviral has produced a greater understanding of the viral fusion process, a new hypothesis for the mechanism of action of ribavirin, and a promising antisense strategy combining the 2'-5' oligoadenylate antisense (2-5A-antisense) approach and RSV genomics.

Respiratory syncytial virus (RSV) nonstructural (NS) proteins as host range determinants: a chimeric bovine RSV with NS genes from human RSV is attenuated in interferon-competent bovine cells

Bovine respiratory syncytial virus (BRSV) escapes from cellular responses to alpha/beta interferon (IFN-alpha/beta) by a concerted action of the two viral nonstructural proteins, NS1 and NS2. Here we show that the NS proteins of human RSV (HRSV) are also able to counteract IFN responses and that they have the capacity to protect replication of an unrelated rhabdovirus. Even combinations of BRSV and HRSV NS proteins showed a protective activity, suggesting common mechanisms and cellular targets of HRSV and BRSV NS proteins. Although able to cooperate, NS proteins from BRSV and HRSV showed differential protection capacity in cells from different hosts. A chimeric BRSV with HRSV NS genes (BRSV h1/2) was severely attenuated in bovine IFN competent MDBK and Klu cells, whereas it replicated like BRSV in IFN-incompetent Vero cells or in IFN-competent human HEp-2 cells. After challenge with exogenous IFN-alpha, BRSV h1/2 was better protected than wild-type BRSV in human HEp-2 cells. In contrast, in cells of bovine origin, BRSV h1/2 was much less resistant to exogenous IFN than wild-type BRSV. These data demonstrate that RSV NS1 and NS2 proteins are major determinants of host range. The differential IFN escape capacity of RSV NS proteins in cells from different hosts provides a basis for rational development of attenuated live RSV vaccines.

RSV: Management of the acute episode

Bronchiolitis is the most common lower respiratory tract infection in infants and is responsible for the majority of paediatric hospital admissions in the winter. Despite significant advances in pharmacotherapy, the management of infants with bronchiolitis has changed little over the years from supplemental oxygen and good fluid management. This paper reviews current treatment options for bronchiolitis, including the use of bronchodilators, adrenaline, steroids and ribavirin. More recent advances, including immunotherapy and intensive care, are discussed.

Systemic corticosteroids in infant bronchiolitis: A meta-analysis

OBJECTIVE

To determine whether corticosteroids are efficacious in treating bronchiolitis in hospitalized infants.

METHODS

Online bibliographic databases (Medline, Embase, and Cochrane Clinical Trials Registry) were searched for: 1) bronchiolitis or respiratory syncytial virus, and 2) corticosteroid or glucocorticoid or steroidal antiinflammatory agents or adrenal cortex hormones. Reference lists from all selected articles were also examined. Randomized, placebo-controlled trials of systemic corticosteroids in treatment of infants hospitalized with bronchiolitis were selected by 2 investigators. Of 12 relevant publications identified in the literature search, 6 met the selection criteria and had relevant data available. Investigators independently extracted data for 3 outcomes: length of stay (LOS), duration of symptoms (DOS), and clinical scores.

RESULTS

In the pooled analysis, infants who received corticosteroids had a mean LOS or DOS that was.43 days less than those who received the placebo treatment (95% confidence interval: -.81 to -.05 days). The effect size for mean clinical score was -1.60 (95% confidence interval: -1.92 to -1.28), favoring treatment. Secondary analyses of mean LOS or DOS were performed on 5 trials that had clearly identified methods of randomization, 5 trials that measured LOS, and 4 trials that clearly excluded infants with previous wheezing. The estimates of effect were similar to the primary analysis but were not statistically significant.

CONCLUSIONS

Combined, published reports of the effect of systemic corticosteroids on the course of bronchiolitis suggest a statistically significant improvement in clinical symptoms, LOS, and DOS.

Respiratory syncytial virus strain A2 is resistant to the antiviral effects of type I interferons and human MxA

Respiratory syncytial virus (RSV) belongs to Paramyxoviridae family of enveloped negative-strand RNA viruses and causes severe bronchiolitis and pneumonia in children younger than 2 years of age. As members of Paramyxoviridae family, RSV and parainfluenza type 3 (PIV3) have similar modes of infection and replication. A variety of negative-strand RNA virus infections, including that of PIV3, are inhibited by human MxA protein, a type I interferon (IFN)-inducible GTPase. We tested whether the MxA protein, induced either by type I human IFNs or by stable transfection of human MxA gene in human (U-87) or simian (Vero) cells, confers resistance to these cells against infection by RSV strain A2. RSV infection was resistant to antiviral effects induced by 0-10,000 U/ml type I IFNs (IFN-alpha or -beta) in both human lung epithelial, A549, and fibroblast, MRC-5 cells. RSV virus yield was reduced only by 10- to 20-fold, and viral protein synthesis was not significantly affected under conditions of IFN treatment where PIV3 yield was reduced by 1000- to 10,000-fold. Human or simian cell lines constitutively expressing MxA were protected against infection by PIV3 but not by RSV. Our results indicate that RSV A2 is resistant to the antiviral effects of MxA, even though RSV and PIV3 have similar replication strategies. In IFN-treated coinfected cultures, IFN-resistant RSV A2 did not prevent the IFN-mediated inhibition of PIV3 multiplication. Hence the resistance of RSV A2 to type I IFNs does not appear to be due to soluble factors released into the medium or a disruption in the cellular antiviral machinery brought about by RSV A2 infection.

Chemotherapy of respiratory viruses: prospects and challenges

Billions of people are infected with respiratory viruses annually. Infants and young children, the elderly, immunocompromised individuals and those debilitated by other diseases or nutritional deficiencies are most at risk for serious disease. There are few vaccines available for use against these viruses, and even where there are (influenza, measles and adenovirus), infections remain common. The continued prevalence of respiratory virus infections has lead to renewed efforts to find safe agents effective against the most medically important respiratory viruses: influenza, respiratory syncytial, parainfluenza, measles, rhino- and adenovirus. Copyright 1999 Harcourt Publishers Ltd.

Respiratory syncytial virus (RSV) disease and prospects for its control

Respiratory syncytial virus (RSV) is a major virus pathogen of infants and young children, an important cause of disease in adults and is responsible for a significant amount of excess morbidity and mortality in the elderly. It also can be devastating in immunosuppressed populations. Vaccines are being developed, but none are currently licensed. Moreover, even if one or more are approved, they may not be suitable for some populations vulnerable to RSV (e.g. very young infants and the immunosuppressed). Ribavirin and immunoglobulin preparations with high titers of RSV-specific neutralizing antibodies are currently approved for use to treat and prevent RSV infection. However, neither of these is cost-effective or simple to administer. New agents are needed to reduce the impact of RSV. This review is concerned with the means currently available for controlling RSV, the search for new agents effective against this virus, and future prospects for preventing and treating RSV infections.

Respiratory syncytial virus infection: clinical presentation and management

RSV infection continues to be a major cause of morbidity and mortality throughout the world. Despite advances in the understanding of its pathogenesis, limited progress has been made in prevention and treatment of RSV infection. Based on the experiences thus far it seems that control of RSV infection will be a difficult and complex task.