The complex relationship between respiratory syncytial virus and allergy in lung disease

Pulmonary IL-33 orchestrates innate immune cells to mediate respiratory syncytial virus-evoked airway hyperreactivity and eosinophilia

BACKGROUND

Respiratory syncytial virus (RSV) infection is epidemiologically linked to asthma. During RSV infection, IL-33 is elevated and promotes immune cell activation, leading to the development of asthma. However, which immune cells are responsible for triggering airway hyperreactivity (AHR), inflammation and eosinophilia remained to be clarified. We aimed to elucidate the individual roles of IL-33-activated innate immune cells, including ILC2s and ST2⁺ myeloid cells, in RSV infection-triggered pathophysiology.

METHODS

The role of IL-33/ILC2 axis in RSV-induced AHR inflammation and eosinophilia were evaluated in the IL-33-deficient and YetCre-13 Rosa-DTA mice. Myeloid-specific, IL-33-deficient or ST2-deficient mice were employed to examine the role of IL-33 and ST2 signaling in myeloid cells.

RESULTS

We found that IL-33-activated ILC2s were crucial for the development of AHR and airway inflammation, during RSV infection. ILC2-derived IL-13 was sufficient for RSV-driven AHR, since reconstitution of wild-type ILC2 rescued RSV-driven AHR in IL-13-deficient mice. Meanwhile, myeloid cell-derived IL-33 was required for airway inflammation, ST2⁺ myeloid cells contributed to exacerbation of airway inflammation, suggesting the importance of IL-33 signaling in these cells. Local and peripheral eosinophilia is linked to both ILC2 and myeloid IL-33 signaling.

CONCLUSIONS

This study highlights the importance of IL-33-activated ILC2s in mediating RSV-triggered AHR and eosinophilia. In addition, IL-33 signaling in myeloid cells is crucial for airway inflammation.

Respiratory syncytial virus infection: from biology to therapy: a perspective

Respiratory syncytial virus (RSV) is responsible for significant morbidity and mortality, particularly in infants younger than 18 months and in the elderly. To date, there are few effective treatment options available to prevent or treat RSV infections. Attractive therapeutic strategies include targeting host epithelial adhesion molecules required for RSV infection, enhancing localized cell-mediated immunity, interfering with RSV viral gene expression and developing a multigene DNA vaccine. The most recent data supporting the advantages and limitations of each of these approaches are discussed in detail. Several promising strategies offer hope for safe and effective prophylaxis and treatment of RSV infection.

T Cell receptor clonotype influences epitope hierarchy in the CD8+ T cell response to respiratory syncytial virus infection

CD8+ T cell responses are important for recognizing and resolving viral infections. To better understand the selection and hierarchy of virus-specific T cell responses, we compared the T cell receptor (TCR) clonotype in parent and hybrid strains of respiratory syncytial virus-infected mice. K(d)M2(82-90) (SYIGSINNI) in BALB/c and D(b)M(187-195) (NAITNAKII) in C57Bl/6 are both dominant epitopes in parent strains but assume a distinct hierarchy, with K(d)M2(82-90) dominant to D(b)M(187-195) in hybrid CB6F1/J mice. The dominant K(d)M2(82-90) response is relatively public and is restricted primarily to the highly prevalent Vβ13.2 in BALB/c and hybrid mice, whereas D(b)M(187-195) responses in C57BL/6 mice are relatively private and involve multiple Vβ subtypes, some of which are lost in hybrids. A significant frequency of TCR CDR3 sequences in the D(b)M(187-195) response have a distinct "(D/E)WG" motif formed by a limited number of recombination strategies. Modeling of the dominant epitope suggested a flat, featureless structure, but D(b)M(187-195) showed a distinctive structure formed by Lys(7). The data suggest that common recombination events in prevalent Vβ genes may provide a numerical advantage in the T cell response and that distinct epitope structures may impose more limited options for successful TCR selection. Defining how epitope structure is interpreted to inform T cell function will improve the design of future gene-based vaccines.

TSLP from RSV-stimulated rat airway epithelial cells activates myeloid dendritic cells

The respiratory syncytial virus (RSV) is a primary cause of lower respiratory tract infections in children, the elderly and in people who are immune suppressed, and is also the cause for the development of asthma primarily in infants. However, the immunological mechanisms by which RSV enhances allergic sensitization and asthma remain unclear. The aim of this study was to examine the influence of RSV-infected airway epithelial cells on the activation and functions of rat myeloid dendritic cells (mDCs).We found that the exposure of primary rat airway epithelial cells (PRAECs) to RSV induced a rapid (6 h), high (12 h) and persistent (18 h) increase in thymic stromal lymphopoietin (TSLP) mRNA compared with untreated PRAECs. TSLP protein expression was also enhanced by RSV infection. Functional maturation of mDCs was induced by RSV-treated PRAECs, as shown by their enhanced levels of OX40L and thymus- and activation-regulated chemokine (TARC) mRNAs, which increased the expressions of major histocompatibility complex II (MHCII) and CD86 costimulatory molecules and promoted enhanced T-cell proliferation in mixed lymphocyte reactions. These activities were inhibited in cocultures with RSV-infected RTECs (rat tracheal epithelial cells, an immortalized cell strain) that had been pretreated with TSLP-targeted small interfering RNA. These results suggest that RSV can induce epithelial cells to produce TSLP, which in turn promotes the maturation of mDCs that might support Th2 cell polarization.

Respiratory syncytial virus infection provokes airway remodelling in allergen-exposed mice in absence of prior allergen sensitization

BACKGROUND

The mechanisms underlying exacerbation of asthma induced by respiratory syncytial virus (RSV) infection have been extensively studied in human and animal models. However, most of these studies focused on acute inflammation and little is known of its long-term consequences on remodelling of the airway tissue.

OBJECTIVE

The aim of the study was to use a murine model of prolonged allergen-induced airway inflammation to investigate the effect of RSV infection on allergic airway inflammation and tissue remodelling.

METHODS

We subjected mice to RSV infection before or during the chronic phase of airway challenges with OVA and compared parameters of airway inflammation and remodelling at the end-point of the prolonged allergen-induced airway inflammation protocol.

RESULTS

RSV infection did not affect the severity of airway inflammation in any of the groups studied. However, RSV infection provoked airway remodelling in non-sensitized, allergen-challenged mice that did not otherwise develop any of the features of allergic airways disease. Increased collagen synthesis in the lung and thickening of the bronchial basal membrane was observed in non-sensitized allergen-challenged mice only after prior RSV infection. In addition, fibroblast growth factor (FGF)-2 but not TGF-beta(1) was increased in this group following RSV infection.

CONCLUSION

Our data show for the first time that RSV infection can prime the lung of mice that are not previously systemically sensitized, to develop airway remodelling in response to allergen upon sole exposure via the airways. Moreover, our results implicate RSV-induced FGF-2 in the remodelling process in vivo.

Respiratory syncytial virus and innate immunity: a complex interplay of exploitation and subversion

Respiratory syncytial virus causes significant disease in infants, the elderly and select groups of immunocompromised patients. Healthy individuals are also naturally infected with respiratory syncytial virus repeatedly throughout life. Therefore, safe and effective vaccines and therapies are needed. However, a number of factors have prevented development of such antiviral interventions to date. These include a failed vaccine trial, the very young age of the primary target population (neonates), the inability of natural infection to induce long-term protective immunity, and an incomplete understanding of virus-host interactions. The identification of pattern recognition receptors has led to significant increases in our understanding of induction and regulation of innate immune responses. This review will address the impact of these findings on respiratory syncytial virus research.

Respiratory syncytial virus (RSV) evades the human adaptive immune system by skewing the Th1/Th2 cytokine balance toward increased levels of Th2 cytokines and IgE, markers of allergy--a review

Infection of infants in their first year of life, children and elderly people with the respiratory syncytial virus (RSV) endangers the life of the patient. An attempt to develop a formalin-inactivated RSV (FI-RSV) vaccine during the 1960s resulted in an aggravated infection in immunized children, leading to hospitalization, while infection of non-immunized children produced much milder symptoms. The reason for this remained an enigma, one which was gradually solved over the last decade by many researchers who studied the molecular biology of RSV infection of respiratory ciliary cells. Clinical studies of RSV-infected patients indicated increased levels of Th2 cytokines and IgE in the patients' sera, suggesting that an allergy-like condition developed during infection. The biomarkers of allergy caused by endogenous or environmental allergens include a marked increase of the Th2 cytokine IL-4 and IgE non-neutralizing antibodies to the allergen. The way allergens trigger allergy was deciphered recently, and will be discussed later. Studies of RSV infection led to the suggestion that RSV patients suffer from allergy prior to RSV infection, a concept that was later abandoned. Studies on HIV-1 [Y. Becker, Virus Genes 28, 319-331 (2005)] research led me to the hypothesis that since HIV-1 infection induces a marked increase of IL-4 and IgE in serum, an allergy-like condition, the AIDS stage is the result of an allergen motif that is embedded in the shed viral gp120 molecules. It is hypothesized that the viral-soluble G glycoprotein (sG) contains a T cell superantigen (Tsag) that is capable of binding to the V(H)3 domain of IgE/FcepsilonRI(+) hematopoietic cells, basophils, mast cells and monocytes, similar to the case of allergens, and that this aggregation causes these innate system cells to degranulate and release large amounts of Th2 cytokines (IL-4, IL-5, IL-10, IL-13) into the blood. The way these Th2 cytokines skew the Th1/Th2 balance toward Th2 > Th1 will be discussed. The aim of the present review is to base RSV pathogenicity on the numerous very good analyses of the virus genes and to suggest a therapeutic approach to treatment that is directed at preventing the inhibitory effects of Th2 cytokines on the adaptive immune system of the patients, instead of inhibiting RSV replication by antivirals. The review of the molecular research on the role of the viral fusion (F) and attachment (G) glycoproteins of RSV provided information on their role in the virus infection: early in infection the F glycoprotein induces Th1 cells to release the Th1 cytokines IL-2, IL-12 and IFN-gamma to activate precursors CTLs (pCTLs) to become anti-RSV CTLs. The G and sG glycoproteins attach to FKNR1(+) ciliary respiratory epithelial cells as well as directly to eosinophils to the lungs. The sG T cell antigen can also induce the release of large amounts of Th2 cytokines from CD4(+) T cells and from FCepsilonRI(+) mast cells, basophils and monocytes. By comparison to HIV-1 gp120 it is possible to show that in the G and sG proteins the T cell antigen resembles the CD4(+) T cell superantigen (=allergen) domain of HIV-1 gp120 which aggregates with IgE/FCepsilonRI(+) hematopoietic cells. The increased IL-4 level in the serum inhibits the adaptive immune response: IL-4Ralpha(+) Th1 cells stop Th1 cytokine synthesis and IL-4Ralpha(+) B cells stop the synthesis of antiviral IgG and IgA and switch to IgE synthesis. In addition, the hematopoietic cells release histamine and prostaglandin which induce wheezing. The gradual increase of sG molecules creates a gradient of fractalkine (FKN) which directs IL-5-activated eosinophils to the lungs of the patient.

IL-13 is associated with reduced illness and replication in primary respiratory syncytial virus infection in the mouse

The role of IL-13 in respiratory syncytial virus (RSV) immunopathogenesis is incompletely described. To assess the effect of IL-13 on primary RSV infection, transgenic mice which either overexpress IL-13 in the lung (IL-13 OE) or non-transgenic littermates (IL-13 NT) were challenged intranasally with RSV. IL-13 OE mice had significantly decreased peak viral titers four days after infection compared to non-transgenic littermates. In addition, IL-13 OE mice had significantly lower RSV-induced weight loss and reduced lung IFN-γ protein expression compared with IL-13 NT mice. In contrast, primary RSV challenge of IL-13 deficient mice resulted in a small, but statistically significant increase in viral titers on day four after infection, no difference in RSV-induced weight loss compared to wild type mice, and augmented IFN-γ production on day 6 after infection. In STAT1-deficient (STAT1 KO) mice, where primary RSV challenge produced high levels of IL-13 production in the lungs, treatment with an IL-13 neutralizing protein resulted in greater peak viral titers both four and six days after RSV and greater RSV-induced weight loss compared to mice treated with a control protein. These results suggest that IL-13 modulates illness from RSV-infection.

Differential immune responses and pulmonary pathophysiology are induced by two different strains of respiratory syncytial virus

In this study we performed comparisons of pulmonary responses between two different respiratory syncytial virus (RSV) antigenic subgroup A strains, A2 and Line 19. Line 19 strain induced significant dose-responsive airway hyperreactivity (AHR) in BALB/c mice at days 6 and 9 after infection, whereas the A2 strain induced no AHR at any dose. Histological examination indicated that A2 induced no goblet cell hyper/metaplasia, whereas the Line 19 induced goblet cell expansion and significant increases in gob5 and MUC5AC mRNA and protein levels in vivo. When examining cytokine responses, A2 strain induced significant interleukin (IL)-10 expression, whereas Line 19 strain induced significant IL-13 expression. When IL-13-/- mice were infected with Line 19 RSV, the AHR responses were abrogated along with gob5 gene expression. There was little difference in viral titer throughout the infection between the line 19- and A2-infected mice. However, the A2 strain grew to significantly higher titers than the Line 19 strain in HEp-2 cells in vitro. Thus, RSV Line 19-induced airway dysfunction does not correlate with viral load in vivo. These data demonstrate that different RSV strains of the same antigenic subgroup can elicit differential immune responses that impact the phenotypic expression of RSV-induced illness.

Deletion of TLR3 alters the pulmonary immune environment and mucus production during respiratory syncytial virus infection

The detection of a viral infection by pattern recognition receptors (PAMPs) is an integral part of antiviral immunity. In these studies we have investigated the role of TLR3, which recognizes dsRNA, in Respiratory Syncytial virus (RSV) infection using B6 background mice with a TLR3 deletion. Although we observed no changes in viral growth, we did find that TLR3-/- mice demonstrated significant increases in mucus production in the airways of RSV-infected mice. The qualitative assessment was observed by examining differentially stained lungs, followed by immunohistochemical staining for gob5, a mucus-associated protein. The histopathologic observations were verified using quantitative gene expression analyses examining gob5 gene expression. Changes in pulmonary mucus production were accompanied by an increase in pulmonary IL-13 as well as IL-5 expression and eosinophils in the airways of TLR3-/- mice. Examining leukocytes in the airway indicated an accumulation of eosinophils in TLR3-/- mice, but not wild-type mice, after RSV infection. Isolated lung draining lymph node cells from TLR3-/- mice produced significant increases in Th2-type cytokines, IL-5, and IL-13, compared with wild-type TLR3+/+ mice only after RSV infection. To demonstrate a causative link, we depleted TLR3-/- mice of IL-13 during RSV infection and found that mucus and gob5 expression in the lungs was attenuated. Together, these studies highlight that although TLR3 may not be required for viral clearance, it is necessary to maintain the proper immune environment in the lung to avoid developing pathologic symptoms of disease.

Infection by the respiratory syncytial virus in infants and young children at high risk

The respiratory syncytial virus is the most common cause of infection of the lower respiratory tract in infants and young children, and is the leading cause of hospitalisation and death due to viral illness during the first year of life. In otherwise healthy infants, the virus usually causes only mild respiratory illness, but premature babies and infants with chronic lung disease, those with congenitally malformed hearts, or those who are immunodeficient, are at increased risk of serious illness, hospitalisation, and death. Recent infection with the virus is also associated with increased postoperative complications after corrective surgery for congenitally malformed hearts. No effective vaccine is currently available, and treatment is limited to supportive therapy. Prevention in groups deemed to be at high-risk, therefore, is essential. In addition to measures for control of infection, prophylactic immunotherapy is indicated in selected patients. Palivizumab (Synagis) is a monoclonal antibody indicated for the prevention of serious viral disease of the lower respiratory tract in premature infants, those with chronic lung disease, and those with haemodynamically significant congenital cardiac lesions. Palivizumab is given intramuscularly, usually as a monthly injection during the so-called "season". In a recent international, randomised, double-blind, placebo-controlled trial in 1,287 children less than or equal to 2 years old with haemodynamically significant congenital cardiac malformations, prophylaxis achieved a relative reduction of 45 per cent in the incidence of antigen-confirmed viral-related hospitalisation, and reduced the duration of hospital stay by 56 per cent. National and international guidelines, therefore, now recommend routine prophylaxis in the first year of life in children with haemodynamically significant congenital cardiac disease.

Relationship between atopic status and nasal interleukin 10 and 11 levels in infants with respiratory syncytial virus bronchiolitis

BACKGROUND

Interleukin 10 (IL-10) and IL-11 are known to have anti-inflammatory activities, and they have been implicated in the pathogenesis of respiratory syncytial virus (RSV) infection.

OBJECTIVES

To determine IL-10, IL-11, and myeloperoxidase levels in nasal secretions of infants with acute RSV bronchiolitis and to investigate whether there are any differences in these levels in patients with vs without atopy.

METHODS

We measured IL-10, IL-11, and myeloperoxidase levels in nasal secretions of 44 infants (20 were atopic) with acute RSV bronchiolitis. The nasal secretion samples were obtained from patients at hospital admission and were stored immediately at -70 degrees C until analysis. Atopy was defined as having at least 1 positive skin prick test reaction to common allergens, a history of atopic dermatitis, or a high serum IgE level compared with age-matched controls.

RESULTS

Levels of IL-10, IL-11, and myeloperoxidase increased significantly in samples from infants with acute RSV bronchiolitis. Levels of IL-10 and IL-11 were significantly lower in patients with vs without atopy (P < .05). Myeloperoxidase levels showed no significant difference in patients with vs without atopy (P = .18). Patients with severe symptoms tended to have lower IL-10 levels (P = .09), but no relationship was shown between symptom severity and IL-11 levels. Nasal myeloperoxidase levels were significantly higher in patients with severe symptoms (P < .05).

CONCLUSIONS

Production of IL-10 and IL-11 was significantly lower in patients with vs without atopy during acute RSV bronchiolitis. The airway inflammation induced by RSV infection may be different in patients with vs without atopy, and this is associated with lower induction of these immunoregulatory cytokines in children with atopy.

Inhibition of respiratory viruses by nasally administered siRNA

Respiratory syncytial virus (RSV) and parainfluenza virus (PIV) are two respiratory pathogens of paramount medical significance that exert high mortality. At present, there is no reliable vaccine or antiviral drug against either virus. Using an RNA interference (RNAi) approach, we show that individual as well as joint infection by RSV and PIV can be specifically prevented and inhibited by short interfering RNAs (siRNAs), instilled intranasally in the mouse, with or without transfection reagents. The degree of protection matched the antiviral activity of the siRNA in cell culture, allowing an avenue for quick screening of an efficacious siRNA. When targeting both viruses in a joint infection, excess of one siRNA moderated the inhibitory effect of the other, suggesting competition for the RNAi machinery. Our results suggest that, if properly designed, low dosages of inhaled siRNA might offer a fast, potent and easily administrable antiviral regimen against respiratory viral diseases in humans.

Respiratory syncytial virus-induced immunoprotection and immunopathology

Respiratory syncytial virus (RSV), a member of the Paramyxoviridae family, is a major clinical problem causing yearly epidemics of severe lower airway disease in both infants and the elderly. Attempts at vaccination have been frustrated by both the poor immunogenicity of this virus, and the severe immunopathology observed in early vaccine trials. Primary infection generally occurs in infancy, with approximately 5% of infected infants requiring hospitalization. Equally problematic is the apparent link between severe RSV disease and the later development of allergy and asthma. While there is no evidence that natural infection promotes Th2 predominance, development of enhanced eosinophilic disease in children receiving inactivated virus administered with a commonly used adjuvant demonstrated how easily the balance between immune-mediated protection and immune-mediated pathology can be perturbed. In this review we have focused on studies carried out in the mouse model aimed at determining the correlates of RSV protection and explaining the mechanism of vaccine enhanced immunopathology.

Vbeta14(+) T cells mediate the vaccine-enhanced disease induced by immunization with respiratory syncytial virus (RSV) G glycoprotein but not with formalin-inactivated RSV

Mice immunized with respiratory syncytial virus (RSV) G glycoprotein or with formalin-inactivated RSV (FI-RSV) exhibit severe disease following RSV challenge. This results in type 2 cytokine production and pulmonary eosinophilia, both hallmarks of vaccine-enhanced disease. RSV G-induced T-cell responses were shown to be restricted to CD4(+) T cells expressing Vbeta14 in the T-cell receptor (TCR), and the deletion of these T cells resulted in less severe disease. We therefore examined the role of Vbeta14(+) T cells in FI-RSV-induced disease. BALB/c mice were immunized with vaccinia virus expressing secreted RSV G (vvGs) or with FI-RSV. At the time of challenge with live RSV, mice were injected with antibody to the Vbeta14 component of the TCR. vvGs-immunized mice treated with anti-Vbeta14 had reduced cytokine levels in the lung. Eosinophil recruitment to the lung was also significantly reduced. In contrast, depletion of Vbeta14(+) T cells in FI-RSV-immunized mice had little impact on cytokine production or pulmonary eosinophilia. An analysis of TCR Vbeta chain usage confirmed a bias toward Vbeta14 expression on CD4(+) T cells from vvGs-immunized mice, whereas the CD4(+) T cells in FI-RSV-immunized mice expressed a diverse array of Vbeta chains. These data show that although FI-RSV and vvGs induce responses resulting in similar immunopathology, the T-cell repertoire mediating the response is different for each immunogen and suggest that the immune responses elicited by RSV G are not the basis for FI-RSV vaccine-enhanced disease.

Pathogenesis of Respiratory Syncytial Virus Infection

Respiratory syncytial virus (RSV) is recognized as the most important cause of serious lower respiratory tract illness in infants and young children worldwide causing repeat infections throughout life with serious complications occurring in the elderly and immune compromised patient. The level of disease pathogenesis associated with RSV infection is balanced between virus elimination and the nature of the immune response to infection. The innate and adaptive immune responses to RSV infection are not fully elucidated; however, significant progress has been made in understanding the virus-host relationship and mechanisms associated with disease pathogenesis. This review summarizes important aspects of these findings, and provides current perspective on processes that may contribute to RSV disease pathogenesis.

Anti-respiratory syncytial virus (RSV) neutralizing antibody decreases lung inflammation, airway obstruction, and airway hyperresponsiveness in a murine RSV model

Numerous studies have described a strong association between respiratory syncytial virus (RSV) infection in infancy and the development of recurrent wheezing and airway hyperresponsiveness. We evaluated the effect of an anti-RSV neutralizing monoclonal antibody (palivizumab) on different aspects of RSV disease by using a murine model. BALB/c mice were intranasally inoculated with RSV A2. Palivizumab or an isotype-matched control antibody was administered once at 24 h before inoculation, 1 h after inoculation, or 48 h after inoculation. Regardless of the timing of administration, all mice treated with the neutralizing antibody showed significantly decreased RSV loads in bronchoalveolar lavage (BAL) and lung specimens compared with those of infected controls. Pulmonary histopathologic scores, airway obstruction measured by plethysmography, and airway hyperresponsiveness after methacholine challenge were significantly reduced in mice treated with the anti-RSV antibody 24 h before inoculation compared with those for untreated controls. Concentrations of interferon-gamma, interleukin-10, macrophage inflammatory protein 1alpha, regulated on activation normal T-cell expressed and secreted (RANTES), and eotaxin in BAL fluids were also significantly reduced in mice treated with palivizumab 24 h before inoculation. This study demonstrates that reduced RSV replication was associated with significant modulation of inflammatory and clinical markers of acute disease severity and significant improvement of the long-term pulmonary abnormalities. Studies to determine whether strategies aimed at preventing or reducing RSV replication could decrease the long-term morbidity associated with RSV infection in children should be considered.

Regulation of Mite Allergen-pulsed Murine Dendritic Cells by Respiratory Syncytial Virus

Dendritic cells (DCs) are the only antigen-presenting cells that determine T-cell differentiation and play an important role in both allergy and viral infection. Respiratory syncytial virus (RSV) can infect DCs and affect their functions. The aim of this study was to determine the interaction between RSV infection and Dermatophagoides farinae allergen (D. farinae) sensitization on the development of allergy at the DC level. Murine bone marrow-derived DCs were prepared and treated as: control; D. farinae-pulsed DCs (D. farinae-DCs); ultraviolet-inactivated RSV challenged; RSV-infected, D. farinae-pulsed plus ultraviolet-inactivated RSV-challenged; and D. farinae-pulsed plus RSV-infected. In in vitro experiments, we compared the expression of costimulatory molecules and cytokine production between the six groups of DCs. Another group of naive mice were then intranasally inoculated with these DCs, after which intranasal challenge with D. farinae was performed to develop allergic airway inflammation in vivo. In comparison with D. farinae-DCs, D. farinae-pulsed plus RSV-infected DCs showed helper T cell (Th) 1-favored expression of costimulatory molecules and cytokine production. Allergic airway inflammation induced by intranasal instillation of D. farinae-DCs was abrogated when infected with RSV, which was associated with a concomitant suppression of Th2 response in the lung. Our results indicated that RSV suppresses D. farinae-DCs to induce Th2 response both in vitro and in vivo through regulation of expression of surface markers and production of immunoregulatory cytokines.

Role of allergy in rhinosinusitis

PURPOSE OF REVIEW

Allergic rhinitis and rhinosinusitis are common diseases occurring in both children and adults that consume enormous amounts of health care dollars. In addition to its own costs, allergic rhinitis is considered a major predisposing factor for the development of rhinosinusitis. Whereas many authors suggest a clinical association between these two diseases, the mechanism of how allergic rhinitis predisposes to rhinosinusitis or affects the course of rhinosinusitis remains unclear.

RECENT FINDINGS

Limited progress has been made in understanding the pathophysiologic mechanism involved in the interaction. Progress in immunologic technique emphasizes the importance of inflammatory cells, especially eosinophils, mast cells, and T lymphocytes, and their mediators. Some authors have proposed a role for neurogenic pathways, whereas others have focused on systemic involvement. Little progress has been made in intervention studies that support the importance of allergic rhinitis in altering the course of acute or chronic rhinosinusitis.

SUMMARY

This paper reviews the limited new literature available to update knowledge that supports the association of allergic rhinitis with rhinosinusitis, mechanisms potentially underlying the association, and implications of this knowledge for therapy.