Enhancement of basophil chemotaxis in vitro by virus-induced interferon

The role of hematological parameters in asymptomatic and non-severe cases of Omicron variant infection

BACKGROUND

Omicron variants are currently the predominant circulating lineage worldwide and most cases are mild or asymptomatic. The Omicron variant is characterized by high transmissibility and immune evasion. Early identification of Omicron cases in clinical settings is crucial for controlling its spread. Previous studies have indicated that changes in hematological parameters can be used to predict the severity of coronavirus disease 2019 (COVID-19). However, the role of hematological parameters in non-severe and asymptomatic cases remains unknown. This study aimed to investigate the role of hematological parameters in non-severe and asymptomatic Omicron variant infections.

METHODS

Hematological parameters and results were analyzed and compared in symptomatic (n = 356) and asymptomatic (n = 171) groups respectively, and between these two groups with positive COVID-19 tests. The utility of hematological parameters for predicting positive COVID-19 tests was analyzed using receiver operating characteristic curves.

RESULTS

Individuals with non-severe cases exhibited decreased levels of platelets, lymphocytes, eosinophils, basophils, lymphocytes (%), eosinophils (%), and basophils (%), while exhibiting elevated counts of monocytes, neutrophils (%), monocytes (%), neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio (PLR), and C-reactive protein (CRP) when compared to suspected cases or asymptomatic carriers. In asymptomatic patients, positive carriers had lower leukocyte, neutrophil, and lymphocyte counts but higher monocyte, monocyte (%), PLR, and CRP levels than negative carriers. Basophil counts combined with lymphocytes or the PLR demonstrated a more significant predictive value in screening non-severe cases earlier compared to other parameters. The combined assessment of the monocyte (%) and the PLR had the highest area under the curve for diagnosing asymptomatic carriers.

CONCLUSIONS

Circulating basophils, alone or in combination with other hematological parameters, may be used as efficient biomarkers for early screening of non-severe Omicron cases.

Basophils and Mast Cells in COVID-19 Pathogenesis

Basophils and mast cells are among the principal inducers of Th2 responses and have a crucial role in allergic and anti-parasitic protective immunity. Basophils can function as antigen-presenting cells that bind antigens on their surface and boost humoral immune responses, inducing Th2 cell differentiation. Their depletion results in lower humoral memory activation and greater infection susceptibility. Basophils seem to have an active role upon immune response to SARS-CoV-2. In fact, a coordinate adaptive immune response to SARS-CoV-2 is magnified by basophils. It has been observed that basophil amount is lower during acute disease with respect to the recovery phase and that the grade of this depletion is an important determinant of the antibody response to the virus. Moreover, mast cells, present in a great quantity in the nasal epithelial and lung cells, participate in the first immune response to SARS-CoV-2. Their activation results in a hyperinflammatory syndrome through the release of inflammatory molecules, participating to the “cytokine storm” and, in a longer period, inducing pulmonary fibrosis. The literature data suggest that basophil counts may be a useful prognostic tool for COVID-19, since their reduction is associated with a worse prognosis. Mast cells, on the other hand, represent a possible therapeutic target for reducing the airway inflammation characteristic of the hyperacute phase of the disease.

A basophil-neuronal axis promotes itch

Itch is an evolutionarily conserved sensation that facilitates expulsion of pathogens and noxious stimuli from the skin. However, in organ failure, cancer, and chronic inflammatory disorders such as atopic dermatitis (AD), itch becomes chronic, intractable, and debilitating. In addition to chronic itch, patients often experience intense acute itch exacerbations. Recent discoveries have unearthed the neuroimmune circuitry of itch, leading to the development of anti-itch treatments. However, mechanisms underlying acute itch exacerbations remain overlooked. Herein, we identify that a large proportion of patients with AD harbor allergen-specific immunoglobulin E (IgE) and exhibit a propensity for acute itch flares. In mice, while allergen-provoked acute itch is mediated by the mast cell-histamine axis in steady state, AD-associated inflammation renders this pathway dispensable. Instead, a previously unrecognized basophil-leukotriene (LT) axis emerges as critical for acute itch flares. By probing fundamental itch mechanisms, our study highlights a basophil-neuronal circuit that may underlie a variety of neuroimmune processes.

Systemic activation of basophils and eosinophils: markers and consequences

Basophils and eosinophils are important effector cells in human allergic diseases; they play a significant role in promoting allergic inflammation through the release of proinflammatory mediators (such as histamine, leukotriene C(4), major basic protein, eosinophil cationic protein, IL-4, and IL-13, among others). Notably, in allergic subjects, these cells exist in higher numbers and in a more activated state compared with nonatopic control subjects. Evidence for the greater activation state includes increased expression of intracellular and surface markers and hyperreleasability of allergy mediators. We have been interested in the phenotypic markers of effector-cell activation for many years. There is considerable overlap among activation markers, and few activation markers have been found that define a unique phenotype that is quantifiable in the assessment of the presence and severity of allergic disease. This review summarizes the existing evidence for systemic activation of human basophils and eosinophils in allergic diseases. The potential mechanisms responsible for functional and morphologic alterations in these effector cells and the specificity and utility of surface markers in the assessment of allergic disease activity or severity are also discussed.

Airway inflammation, bronchial reactivity and asthma

Asthma is a common disease of children the basis of which is a state of chronic immunological inflammation which causes bronchial hyperreactivity and renders the patient liable to develop widespread airways obstruction in response to a variety of stimuli. In many instances it is likely that the immunological inflammation results from ongoing antigenic stimuli with the release of chemical mediators responsible for short term bronchospasm and cytokines responsible for the ongoing inflammatory process. Other insults can apparently result in very similar immunological events in asthmatics, particularly viral infections and a similar process can be initiated in children without asthma, including those with chronic bacterial infections of the lungs. There are differences in the bronchial hyperreactivity of asthma and other diseases which suggest that in the asthmatic the mast cell is either different structurally or functionally and this renders the patient susceptible to exercise induced asthma in addition to the bronchial hyperreactivity to chemical mediators common to a number of diseases with hyperreactivity. There is good evidence of direct genetic control of atopy and the large majority of children with asthma are atopic but there is no direct genetic link between atopy and asthma and twin studies strongly suggest the existence of a 'permissive' asthma gene which will allow the disease to develop if there is an appropriate external trigger. The only drugs which have been shown to significantly reduce bronchial reactivity are the corticosteroids with a lesser effect noted for sodium cromoglycate and nedocromil. Inhaled corticosteroids can reverse the immunologic inflammatory process and reduce bronchial reactivity, sometimes to normal levels, but on stopping treatment the patient reverts back to the asthmatic state. At the present time it appears that controlled longterm inhaled corticosteroid therapy is the most rational treatment for significant perennial childhood asthma.

The impact of respiratory infections on asthma

It is apparent that the effects of viral respiratory infections on the development of airway hyperresponsiveness are multiple and interrelated and involved the production of viral specific IgE, upregulation of leukocyte inflammatory activity, enhancement of the factors involved in the generation of late phase allergic responses, altered beta-adrenergic and cholinergic nervous system activity, and damage to the airway epithelium. The summation of these effects is the development of airway inflammation rather than a direct effect on bronchial smooth muscle, per se. An understanding of this pathogenesis underscores the relative importance of anti-inflammatory rather than antimicrobial therapy in viral-induced exacerbations in asthma symptoms.

Effects of cytokines on human basophil chemotaxis

Basophil chemotactic activity (BCA) of eight recombinant human (rh) cytokines was examined. Highly purified basophils were obtained by Percoll discontinuous gradients, followed by negative selection using flow cytometry. Then BCA was measured by means of modified Boyden chamber method. Both interleukin (IL)-3 and granulocyte-macrophage colony-stimulating factor (GM-CSF) had much more potent BCA than complement C5a, leukotriene B4 and platelet activating factor, well known as granulocyte chemotactic factors. Chemotaxis rather than chemokinesis was shown in chequerboard analysis of basophil migration induced by IL-3 and GM-CSF. Relatively high concentrations of IL-5 also induced basophil migration, although predominantly chemokinetic. IL-8 had apparent BCA, which was not so high as that of C5a. In contrast, IL-2, IL-4, interferon(IFN)-gamma and granulocyte colony-stimulating factor (G-CSF) had no significant BCA. These findings suggest that IL-3, IL-5, GM-CSF and, perhaps, IL-8 have an effect on basophil migration as well as modulation of basophil mediator release and may provide some insight into the basophil accumulation observed in late-phase allergic responses.

Detection of enhanced neutrophil adhesion to parainfluenza-infected airway epithelial cells using a modified myeloperoxidase assay in a microtiter format

Despite growing evidence that respiratory virus infections precipitate episodes of airway obstruction and airway hyper-responsiveness in young children and in asthma, little information is available on the mechanisms by which virus infections alter the airway physiology. Airway inflammatory changes (including influx of inflammatory cells such as neutrophils) have been described during episodes of airway hyper-responsiveness in both animal models and human subjects. Neutrophil damage to several cell types has been shown to require adhesion as a primary step. In order to examine the potential interactions between virus-infected airway epithelial cells and neutrophils, we have studied the ability of neutrophils to adhere to virus-infected airway epithelial cell cultures. Neutrophil adherence was determined indirectly, using myeloperoxidase as a marker for adherent neutrophils in an assay system described here. Airway epithelial cell cultures (both primary human tracheal epithelial cells, and two permanent cell lines, A549 and BEAS-2B) were grown in 96-well tissue culture plates and infected with human parainfluenza virus type 2. Infected airway epithelial cell cultures supported significantly enhanced levels of neutrophil adherence (up to 50-75% of neutrophils added to the wells) compared to uninfected control cultures. Moreover, this adherence occurred in a virus dose-dependent fashion, with increasing levels of adherence noted at increasing viral multiplicities of infection. The assay system described allows the detection of small numbers of adherent neutrophils (as few as 1000 neutrophils) in a 96-well format.

Viruses as precipitants of asthma symptoms. II. Physiology and mechanisms

The upper and lower airways have complimentary roles in the ultimate object of supplying the body with oxygen whilst removing waste products of metabolism. Pathology in one area may trigger a response in another, the physiology of which, in the case of virus-induced asthma exacerbations remains poorly characterized. Viral infection of the upper airways by common cold viruses frequently triggers a response in the lower airways leading to prolonged morbidity, especially in subjects with significant pre-existing airway disease. The induction or amplification of BHR may be an important mechanism whereby asthmatic symptoms are produced although the cellular and tissue events or reflex mechanisms activated by viral illnesses and underlying BHR changes are poorly defined and may be dependent on the type and the severity of infection. Children and asthmatics tend to develop frequent colds setting in motion a sequence of events culminating in airway obstruction and symptoms of wheezing, coughing and chest tightness. This may reflect independent inflammatory changes caused by a simply additive effect of viral damage to the mucosa superimposed upon pre-existing allergic inflammation (Fig. 1). Few if any symptoms will develop in normal subjects with a mild cold whereas significant symptoms may ensue if the cold is severe and induces marked lower airway swelling, secretions and smooth muscle contraction; pathology to which children who have small calibre airways may be particularly susceptible. In asthmatics even a mild cold frequently induces exacerbation of symptoms, while serious life-threatening asthma attacks may occur associated with a severe cold. Some studies have suggested that this effect is not only additive but also synergistic and brought about by release of the mediators already present in increased quantities, the induction of IgE synthesis, or by the potentiation of neural and epithelial damage. The combined effect of both asthma and viruses may thus be amplified and result in a sustained and refractory period of airway obstruction, severe symptoms and unstable asthma. As most hospital admissions for asthma occur over the winter months and soon after the start of the school terms [115], spread of viruses through the community to susceptible individuals may be the single most important cause of sustained exacerbations of asthma. Definition of the pathological and physiological mechanisms involved will lead to better understanding and may thus provide a basis for prevention and the development of effective forms of treatment for virus-induced asthma.

Respiratory infections and asthma

Airway responsiveness is increased during respiratory virus infections, both in subjects with asthma and without underlying pulmonary disease. Furthermore, the airway hyperresponsiveness is altered for a prolonged period of time, weeks or months after the viral illness has subsided. This article reviews the possible mechanisms of virus-associated airway hyperresponsiveness, including the complex interplay of IgE-dependent reactions, changes in autonomic nervous system function and inflammation, epithelial damage, effects of viruses on the cellular immune response, and enhanced late-phase response.

Histamine-releasing factors and inhibitors: historical perspectives and possible implications in human illness

The initiation of allergic reactions with the bridging of surface-bound IgE antibodies on mast cells and basophils by allergens is well recognized. However, it is clear that other factors most likely play a role in regulating these cells. A number of cytokines have been identified that modulate the secretory response of mast cells and basophils. Among the well-characterized cytokines, interleukin-3 and connective tissue-activating peptide III (or its degradation product, neutrophil-activating peptide 2) can increase the secretory response, whereas interleukin-8 specifically inhibits the response to cytokines. Additional factors are currently under investigation. Preliminary studies suggest an important role for these histamine-releasing factors in atopic disorders, as well as in other conditions in which an IgE-dependent mechanism is not demonstrable. Furthermore, these cytokines may modulate the response of basophils and mast cells in physiologic conditions, such as tissue repair and host defense.

In vitro incubation with influenza virus primes human polymorphonuclear leukocyte generation of superoxide

Viral respiratory illnesses exacerbate asthma, increase airway responsiveness, and enhance the frequency of late asthmatic reactions. A number of mechanisms have been identified to explain how respiratory viral illnesses provoke wheezing, including enhanced inflammatory activity of leukocytes. To further understand how respiratory virus-caused illnesses promote leukocyte-dependent airway injury, the following study evaluated the effect of an in vitro incubation of influenza A virus on human polymorphonuclear leukocyte (PMN) generation of superoxide (O2-). PMNs were isolated from anticoagulated human blood following density gradient centrifugation; purified PMNs were then incubated (37 degrees C x 30 min) with influenza virus (PMN:virus ratio of 5:1 [egg-infective dose 50%] and 10:1) in the presence of 10% autologous serum. After incubation, the viable PMNs (greater than 95% exclusion of trypan blue) were activated, by the chemotactic peptide formyl-methionine-leucine-phenylalanine (fMLP), calcium ionophore A23187, or phorbol myristate acetate (PMA), and O2- generation was then measured. Generation of O2- to fMLP and A23187 was significantly enhanced from PMNs that had been incubated with influenza virus. Although influenza virus itself did not generate O2-, it caused a transient increase in intracellular calcium ([Ca2+]i), when measured with Indo-1-loaded cells. These results suggest that influenza virus primes PMNs to generate increased amounts of O2- and that the priming effect is associated with a transient increase in [Ca2+]. Consequently, we postulate that influenza virus priming produces PMNs of enhanced inflammatory potential to cause greater airway injury, obstruction, and responsiveness during a viral respiratory infection.

Immune cells in periapical granuloma: morphological and immunohistochemical characterization

Samples of periapical granulomas obtained from 12 patients were examined using light and electron microscopes and monoclonal antibodies. Monocytes/macrophages, lymphocytes, and plasma cells were nearly always the most abundant cell populations. Ultrastructural analysis showed close contacts between macrophages and cells of the lymphoid lineage, with the lymphoid cells frequently demonstrating blastic features. Immunohistochemical staining with the anti-interleukin 2 receptor antibody showed that the concentration of labeled cells was quite low. The vast majority were lymphocytes, though some mast cells were also labeled. Mast cells were chiefly located in perivascular areas and interleukin 2 receptor-positive mast cells were frequently associated with lymphoid cells. mast cells could be part of a negative feedback mechanism in the immune response. By releasing histamine, they would block the immune response and by absorbing interleukin 2 they would remove it as an immune system stimulant.

Viral infections and allergic disease

Respiratory viruses have profound effect on airway function and the development of allergic reactions. We are particularly interested in the ability of respiratory viruses to promote the development of the inflammatory LAR. Present evidence suggests that the virus effects on LAR are multi-factorial including changes in inflammatory cell mediator release and the tissue-injurious properties of leukocytes. The end-result of these changes is reflected in the development of the late-phase allergic reaction. When this occurs in the airways, airway obstruction and reactivity will be greater. Uncovering the mechanisms of these effects will lead to a greater understanding of asthma and its pathogenesis.

Lack of suppression of IgE production by recombinant interferon gamma: a controlled trial in patients with allergic rhinitis

Recent evidence suggests that interferon-gamma (IFN-gamma) is a potent inhibitor of IgE synthesis in rodents. We conducted a randomized, placebo-controlled, two-period clinical trial of human recombinant IFN-gamma in the treatment of allergic rhinitis. Forty-five adults with well-documented ragweed-allergic rhinitis were randomized into three groups of 15 adults each and received subcutaneous injections three times weekly. The first treatment period (4 weeks during the off season) began on April 18, 1988; the second treatment period (6 weeks during ragweed pollination) began on August 15, 1988. All subjects received the same treatment in both periods. Group 1 received 0.2 mg per injection of IFN, group 2 received 0.02 mg of IFN, and group 3 received placebo. One subject in group 1 and three subjects in group 2 withdrew because of adverse reactions, and three subjects withdrew for personal reasons. There were no significant differences in mean weekly symptom scores or supplemental medication scores among the three groups in either treatment period. Furthermore, there were no significant differences in the changes of serum IgE antibody to crude ragweed extract or in serum total IgE among the three groups during or before the ragweed-pollination season. These results indicate that this treatment regimen with IFN-gamma does not alter IgE production in patients with ragweed hay fever and indicate the need for further clinical research of lymphokine modulation of IgE production.

Respiratory infections: their role in airway responsiveness and the pathogenesis of asthma

The effects of RVIs on airway reactivity are multiple but do not necessarily include direct changes in the intrinsic contractile properties of airway smooth muscle. Rather, respiratory viruses influence bronchial smooth muscle function through a variety of other mechanisms: production of virus-specific IgE antibodies, epithelial injury, polymorphonuclear-dependent inflammation, and enhanced mediator release. Thus, a common pathway to airway hyper-reactivity during respiratory viral illnesses is an overall enhancement of factors that cause or lead to inflammation. When the airways become the target of enhanced inflammation, bronchial reactivity and obstruction are accentuated. Although many questions remain to be answered, future studies to evaluate the biology of respiratory virus effects on mechanisms of allergic sensitization and airway responsiveness promise to provide a greater understanding of the pathogenesis of asthma.

Stimulation of mast cell chemotaxis by interleukin 3

PWM-activated spleen cell-conditioned medium (SCCM) and a variety of purified hematopoietic growth factors were tested for their ability to stimulate chemotaxis of mouse connective tissue mast cells (CTMC). Of the agents tested, only IL-3 and SCCM promoted mast cell chemotaxis. Neither IL-2, IL-4, GM-CSF, nor endotoxin had any significant mast cell chemotactic activity. Neutralizing antibodies to mouse IL-3 blocked greater than 90% of the chemotactic activity of SCCM, suggesting that IL-3 is the predominant mast cell chemotactic factor produced by activated spleen cells. Our results demonstrate that mature connective tissue type mast cells are capable of moving toward a gradient of spleen cell-derived IL-3 and suggest that movement of mature mast cells toward lymphokines may influence the accumulation of mast cells at sites of inflammatory or immune reactions.

The relationship between viral infections and onset of allergic diseases and asthma

The pathogenesis of both allergic diseases and asthma remains an unsolved mystery. Of considerable interest, and perhaps insight, into this problem are clinical observations that viral illnesses play an important role in the allergic diathesis. Conclusive evidence to establish a relationship linking viral illnesses to clinical allergy has yet to be established. Nonetheless, recent observations in this arena are intriguing to scientist and clinician alike. The following discussion reviews recent investigations that evaluate the relationship between viral illnesses and development of allergic disease and asthma.

Purification and characterization of arcelin seed protein from common bean

Arcelin, a seed protein originally discovered in wild bean accessions, was purified, characterized, and compared to phaseolin, the major seed protein of common bean, and to phytohemagglutinin (PHA), the major bean seed lectin. Arcelin and PHA has several characteristics in common. Both were glycoproteins having similar subunit M(r), deglycosylated M(r), and amino acid compositions. The two proteins were related antigenically and they had the same developmental timing of accumulation. Arcelin also had some hemagglutinating activity, a characteristic associated with lectins. However, several features distinguished arcelin from PHA. Arcelin had a more basic isoelectric point than PHA, greater numbers of basic amino acid residues, additional cysteine residues, and one methionine residue, which PHA lacks. Native PHA protein is a tetramer of subunits, and although a small component of native arcelin protein was also tetrameric, most of the arcelin preparation was dimeric. The hemagglutinating activity of arcelin was specific only for some pronase-treated erythrocytes. It did not agglutinate native erythrocytes, nor did it bind to thyroglobulin or fetuin affinity resins as did PHA. Although arcelin has lectin-like properties, we believe the distinctions between arcelin and PHA warrant the designation of arcelin as a unique bean seed protein.

Histamine releasing activity (HRA) produced by leukocytes co-cultured with tumor cells

Human stomach adenocarcinoma (AGS), astrocytoma (AST) and myelogenous leukemia (K562) cells were co-cultured with human peripheral blood leukocytes (PBL) through four days. Histamine releasing activity (HRA, lymphokines that stimulate degranulation of basophilic leukocytes with the release of histamine) and interferons alpha and gamma (IFN alpha and IFN gamma) were detected in the culture fluids. Maximal levels of HRA were detected by 24 hr in AST and K562-leukocyte co-culture fluids. Notably, only low levels of HRA was detected in AGS-leukocyte cultures. HRA was separated into two molecular weight species (60,000 and 25,000) by column chromatography. The IFN activity was shown to be a mixture of IFN alpha and IFN gamma (IFN alpha greater than IFN gamma). IFN did not cause histamine release from human PBL or affect HRA. Our results indicate that PBL from normal individuals produce HRA in response to tumor antigen and suggest that the basophilic leukocyte response to certain cancers may be related to HRA production.

Increase in skin mast cells following chronic house dust mite exposure

Application of inhalant allergens in high concentration to the mildly abraded skin of sensitive patients with atopic dermatitis gave rise to eczematous skin responses at 48 h. These lesions, infiltrated by basophils, eosinophils and mononuclear cells, are examples of cutaneous basophil hypersensitivity. Repeated application of allergen induced an increase in skin mast cells by 6 days, the mast cell hyperplasia replacing the earlier basophil infiltration. No electron microscopic evidence of mast cell heterogeneity among the recruited cells was found.

Histamine-releasing activity. IV. Molecular heterogeneity of the activity from stimulated human thoracic duct lymphocytes

Previous studies with the lymphokine, histamine-releasing activity (HRA), showed that HRA consisted of a heterogeneous group of molecules. The possibility of using thoracic duct lymphocytes (TDL) as a source of large quantities of HRA has been investigated. Antigen-stimulated TDL synthesize and release HRA in quantities similar to an equivalent number of peripheral blood lymphocytes (PBL). Streptokinase (SK) antigen routinely caused TDL to produce HRA approximately 15,000 Da. In contrast, staphylococcus enterotoxin B (SEB) induced the formation of a heterogeneous mixture of HRAs with apparent molecular weights of 50,000 and 15,000. Two peaks of activity (HRA I and II) were recovered when the supernatant from SK-stimulated TDL was subjected to ion-exchange chromatography. Interestingly, basophil chemotactic activity (BCA) was also eluted in these two peaks. Although interferon (IFN) is also released by antigen-stimulated TDL, the nonidentity of IFN and HRA was established by fundamental differences in chromatographic properties and specific antisera to IFN. In contrast, these studies suggest that HRA and BCA may be present on the same molecular entity.

Basophils in human disease

Hypersensitivity reactions containing significant infiltrates of basophils occur in a large proportion of allergic diseases such as contact dermatitis, atopic dermatitis, and allergic rhinitis, and are quite deleterious. However, the potential usefulness of such responses can be recognized in similar reactions in guinea pigs responding to tissue invasion by complex multicellular parasites in which interactions occur between thymic-derived T lymphocytes, antibodies, and basophils in immune resistance responses. Perhaps inappropriate and deleterious allergic responses to pollens, chemicals, and insects is the price that we must pay for the ability to reject complex parasites.