Repurposing of antimycobacterium drugs for COVID-19 treatment by targeting SARS CoV-2 main protease: An in-silico perspective

The global mortality rate has been significantly impacted by the COVID-19 pandemic, caused by the SARS CoV-2 virus. Although the pursuit for a potent antiviral is still in progress, experimental therapies based on repurposing of existing drugs is being attempted. One important therapeutic target for COVID-19 is the main protease (Mpro) that cleaves the viral polyprotein in its replication process. Recently minocycline, an antimycobacterium drug, has been successfully implemented for the treatment of COVID-19 patients. But it's mode of action is still far from clear. Furthermore, it remains unresolved whether alternative antimycobacterium drugs can effectively regulate SARS CoV-2 by inhibiting the enzymatic activity of Mpro. To comprehend these facets, eight well-established antimycobacterium drugs were put through molecular docking experiments. Four of the antimycobacterium drugs (minocycline, rifampicin, clofazimine and ofloxacin) were selected by comparing their binding affinities towards Mpro. All of the four drugs interacted with both the catalytic residues of Mpro (His41 and Cys145). Additionally, molecular dynamics experiments demonstrated that the Mpro-minocyline complex has enhanced stability, experiences reduced conformational fluctuations and greater compactness than other three Mpro-antimycobacterium and Mpro-N3/lopinavir complexes. This research furnishes evidences for implementation of minocycline against SARS CoV-2. In addition, our findings also indicate other three antimycobacterium/antituberculosis drugs (rifampicin, clofazimine and ofloxacin) could potentially be evaluated for COVID-19 therapy.

Role of ATP-Small Heat Shock Protein Interaction in Human Diseases

Adenosine triphosphate (ATP) is an important fuel of life for humans and Mycobacterium species. Its potential role in modulating cellular functions and implications in systemic, pulmonary, and ocular diseases is well studied. Plasma ATP has been used as a diagnostic and prognostic biomarker owing to its close association with disease’s progression. Several stresses induce altered ATP generation, causing disorders and illnesses. Small heat shock proteins (sHSPs) are dynamic oligomers that are dominantly β-sheet in nature. Some important functions that they exhibit include preventing protein aggregation, enabling protein refolding, conferring thermotolerance to cells, and exhibiting anti-apoptotic functions. Expression and functions of sHSPs in humans are closely associated with several diseases like cataracts, cardiovascular diseases, renal diseases, cancer, etc. Additionally, there are some mycobacterial sHSPs like Mycobacterium leprae HSP18 and Mycobacterium tuberculosis HSP16.3, whose molecular chaperone functions are implicated in the growth and survival of pathogens in host species. As both ATP and sHSPs, remain closely associated with several human diseases and survival of bacterial pathogens in the host, therefore substantial research has been conducted to elucidate ATP-sHSP interaction. In this mini review, the impact of ATP on the structure and function of human and mycobacterial sHSPs is discussed. Additionally, how such interactions can influence the onset of several human diseases is also discussed.

Dual-function theranostic nanoparticles for drug delivery and medical imaging contrast: perspectives and challenges for use in lung diseases

Theranostic nanoparticles with both therapeutic and imaging abilities have the promise to revolutionize diagnosis, therapy, and prognosis. Early and accurate detection along with swift treatment are the most important steps in the successful treatment of any disease. Over the last decade, a variety of nanotechnology-based platforms have been created in the hope of improving the treatment and diagnosis of a wide variety of diseases. However, significant hurdles still remain before theranostic nanoparticles can bring clinical solutions to the fight against chronic respiratory diseases. Some fundamental issues such as long-term toxicity, a precise understanding of the accumulation, degradation and clearance of these particles, and the correlation between basic physicochemical properties of these nanoparticles and their in vivo behavior have to be fully understood before they can be used clinically. To date, very little theranostic nanoparticle research has focused on the treatment and diagnosis of chronic respiratory illnesses. Nanomedicine approaches incorporating these theranostic nanoparticles could potentially be translated into clinical advances to improve diagnosis and treatment of these chronic respiratory diseases and enhance quality of life for the patients.

Isatin down-regulates expression of atrial natriuretic peptide receptor A and inhibits airway inflammation in a mouse model of allergic asthma

Isatin, an endogenous indole compound, prevents atrial natriuretic peptide (ANP) from signaling through its cell-surface receptor, NPRA. Allergic airway inflammation has been linked to natriuretic peptide signaling and blocking this signaling axis in the lung prevents allergen-induced pathology. In this study we encapsulated isatin in chitosan nanoparticles and tested them in a mouse model of allergic asthma by intranasal delivery to the lung. Isatin nanocapsules reduced lung pathology by blocking ANP signaling, but surprisingly also by reducing the expression of NPRA. Ovalbumin-allergic mice were treated intranasally with isatin-containing chitosan nanocapsules either before or after allergen challenge, and lung function, cytokine levels, histopathology and cellular infiltration were determined. ANP activity was quantitated by measuring changes in intracellular cyclic GMP and changes in NPRA levels were determined. For comparison with isatin's effects, the expression of the receptor was inhibited with small interfering RNA against NPRA mRNA. Isatin nanocapsules administered locally to the lung reduced cGMP production and NPRA expression and protected allergic mice from airway hyperreactivity and lung inflammation when given either before or after allergen challenge. Leukocyte infiltration was reduced and lung cytokine profiles showed a repolarization from a Th2-like to a Th1-like phenotype. Isatin nanocapsules administered locally to the lung inhibit NPRA signaling but also are capable of lowering the expression of NPRA, thus effectively reducing inflammation in a mouse model of allergic asthma. Pharmacological intervention to reduce NPRA activity through the inflammatory natriuretic peptide axis in the lung may be a useful adjunct therapy for treating lung disease.

Cationic poly(lactide-co-glycolide) nanoparticles as efficient in vivo gene transfection agents

Poly(lactide-co-glycolide) (PLGA), a biocompatible and biodegradable polyester co-polymer of PLA and PGA, has been recognized for its ability to deliver genes. However, gene delivery by PLGA nanoparticles is limited by their negative charge and their poor transport through mucosal barriers. In this study, PLGA nanoparticles were surface modified with cationic chitosan in an effort to improve their gene delivery capability. PLGA nanoparticles were synthesized by emulsion-diffusion-evaporation technique using PVA-chitosan (PLGA1) or PVA-chitosan-PEG (PLGA2) blend as stabilizers. This method is reproducible and produces nanoparticles with hydrodynamic diameter <200 nm. The nanoparticles were characterized by zetasizer, photon correlation spectroscopy and atomic force microscopy. A549 epithelial cells were transfected in vitro with PLGA particles complexed with a reporter plasmid encoding green fluorescent protein. PLGA particles transferred EGFP gene, but were less efficient than the lipofectamine control. The nanoparticles were also tested for their ability to transport across the nasal mucosa in vivo in mice. The results show that both PLGA1 and PLGA2 facilitate gene delivery and expression in vivo with increased efficiency and without causing inflammation, as measured by IL-6. Together, these results indicate that chitosan-modified PLGA nanoparticles have greater potential as gene carriers.

Cationic silica nanoparticles as gene carriers: synthesis, characterization and transfection efficiency in vitro and in vivo

The potential of cationic SiO2 nanoparticles was investigated for in vivo gene transfer in this study. Cationic SiO2 nanoparticles with surface modification were generated using amino-hexyl-amino-propyltri-methoxysilane (AHAPS). The zeta potential of the nanoparticles at pH = 7.4 varied from -31.4 mV (unmodified particles; 10 nm) to +9.6 mV (modified by AHAPS). Complete immobilization of DNA at the nanoparticle surface was achieved at a particle ratio of 80 (w/w nanoparticle/DNA ratio). The surface modified nanoparticle had a size of 42 nm with a distribution from 10-100 nm. The ability of these particles to transfect pCMVbeta reporter gene was tested in Cos-1 cells, and optimum results were obtained in the presence of FCS and chloroquine at a particle ratio of 80. These nanoparticles were tested for their ability to transfer genes in vivo in the mouse lung, and a two-times increase in the expression levels was found with silica particles in comparison to EGFP alone. Very low or no cell toxicity was observed, suggesting silica nanoparticles as potential alternatives for gene transfection.

Elimination of iodine deficiency disorders by 2000 and its bearing on the people in a district of Orissa, India: a knowledge-attitude-practices study

A knowledge-attitude-practices (KAP) study was conducted along with a prevalence study of iodine deficiency disorders (IDD) between 1998-99 in the district of Bargarh, Orissa state, India. A total of 635 people were interviewed by a pretested structured questionnaire, adopting the probability proportional to size cluster sampling method. The aim was to assess the baseline information on the KAP of the people regarding IDD. Only 37% of the males and 29.3% of the females perceived goitre as a disease. Less than 5% of both sexes knew how goitre is caused. Only 16.4% used iodised salt regularly. The awareness and perception of IDD does not correspond with the time and effort we have spent in education of this disease. The implications of this poor knowledge about IDD and consequent poor use of iodised salt is contrasted to the optimistic target of elimination of IDD. This aspect is discussed in this paper, at a time when we are at the beginning of the new millennium.

IFN-gamma and IL-12 plasmid DNAs as vaccine adjuvant in a murine model of grass allergy

BACKGROUND

Plasmids encoding cytokines such as IFN-gamma and IL-12 are potential genetic adjuvants that might increase the effectiveness of allergen vaccines.

OBJECTIVE

The role of plasmids expressing the cytokines IFN-gamma (pIFN-gamma) and/or IL-12 (pIL-12) as adjuvants in modulating allergic immune responses, inflammation, and asthma was investigated in a murine model of Kentucky blue grass (KBG) allergy.

METHODS

Groups of naive B6D2F1 mice were vaccinated subcutaneously with KBG allergens and administered intramuscularly with pIFN-gamma, pIL-12, pIFN-gamma plus pIL-12, or a vector control. Mice were then sensitized with KBG allergens in alum (intraperitoneally) and later challenged intranasally. Mice were examined for modulation of specific immunity, prevention of the development of airway hyperresponsiveness, and inflammation.

RESULTS

Mice vaccinated with cytokine plasmid adjuvants had relatively lower levels of total serum IgE and higher levels of grass allergen-specific IgG2a in comparison with control mice. The lowest IgE and highest IgG2a levels were found in mice vaccinated with the combination of pIFN-gamma and pIL-12 as an adjuvant. The vaccination of mice with both pIFN-gamma and pIL-12 as an adjuvant induced the highest level of T(H)1 cytokines, IFN-gamma, and IL-2 in comparison with mice given either of the plasmids alone. The most profound decrease in airway hyperresponsiveness and pulmonary inflammation was observed in mice receiving both pIFN-gamma and pIL-12 as an adjuvant.

CONCLUSION

These results demonstrate that pIFN-gamma and pIL-12 together provide an effective adjuvant to parenteral grass allergen vaccines and show that this adjuvant can significantly enhance the effectiveness of allergen immunotherapy in human beings.

Blocking intercellular adhesion molecule-1 on human epithelial cells decreases respiratory syncytial virus infection

The respiratory syncytial virus (RSV) causes potentially fatal lower respiratory tract infection in infants. The molecular mechanism of RSV infection is unknown. Our data show that RSV colocalizes with intercellular adhesion molecule-1 (ICAM-1) on the HEp-2 epithelial cell surface. Furthermore, a neutralizing anti-ICAM-1 mAb significantly inhibits RSV infection and infection-induced secretion of proinflammatory chemokine RANTES and mediator ET-1 in HEp-2 cells. Similar decrease in RSV infection is also observed in A549, a type-2 alveolar epithelial cell line, and NHBE, the normal human bronchial epithelial cell line when pretreated with anti-ICAM-1 mAb prior to RSV infection. Incubation of virus with soluble ICAM-1 also significantly decreases RSV infection of epithelial cells. Binding studies using ELISA indicate that RSV binds to ICAM-1, which can be inhibited by an antibody to the fusion F protein and also the recombinant F protein can bind to soluble ICAM-1, suggesting that RSV interaction with ICAM-1 involves the F protein. It is thus concluded that ICAM-1 facilitates RSV entry and infection of human epithelial cells by binding to its F protein, which is important to viral replication and infection and may lend itself as a therapeutic target.

Allergology and clinical immunology--XVII International Congress

A quarter of the world's population has a genetic predisposition to atopy and suffers from one kind of allergy or another. Allergic diseases, including allergic rhinitis, atopic dermatitis, asthma, and anaphylaxis, were first identified as being important at the beginning of the 20th century. Since the discovery of allergens as agents that induce 'reaginic' (now known as IgE) antibodies, there have been spectacular advances in our knowledge of the various effector cells and molecules involved in allergic diseases. This international meeting, held every three years, provides a forum for the discussion of major advances in the field. There was no unifying theme, and the topics covered range from epidemiology and genetics, effector cells and molecules, to immunomodulatory and pharmacotherapeutic treatment.

Recurrent respiratory syncytial virus infections in allergen-sensitized mice lead to persistent airway inflammation and hyperresponsiveness

Respiratory syncytial virus (RSV) infection is considered a risk factor for bronchial asthma; however, the synergy between allergen sensitization and RSV infection in the development of pulmonary inflammation and asthma has been controversial. In this study the effects of primary and recurrent RSV infection on allergic asthma were examined in a group of control, RSV-infected, Dermatophagoides farinae (Df) allergen-sensitized, and Df allergen-sensitized plus RSV-infected BALB/c mice. Primary RSV infection in Df-sensitized mice transiently increases airway responsiveness, which is accompanied by increases in eosinophilic infiltration, the expression of ICAM-1, and macrophage inflammatory protein-1alpha (MIP-1alpha) in the lung tissue. A secondary RSV infection persistently enhances airway responsiveness in Df-sensitized mice, with a concomitant increase in MIP-1alpha and RSV Ag load in lung tissues. Bulk cultures of thoracic lymph node mononuclear cells demonstrate that acute RSV infection augments both Th1- and Th2-like cytokines, whereas secondary and tertiary infections shift the cytokine profile in favor of the Th2-like cytokine response in Df-sensitized mice. The elevated total serum IgE level in the Df-sensitized mice persists following only RSV reinfection. Thus, recurrent RSV infections in Df-sensitized mice augment the synthesis of Th2-like cytokines, total serum IgE Abs, and MIP-1alpha, which are responsible for persistent airway inflammation and hyperresponsiveness, both of which are characteristics of asthma.

Differential cytokine mRNA expression in Dermatophagoides farinae allergen-sensitized and respiratory syncytial virus-infected mice

The interaction between mite allergen sensitization and respiratory syncytial virus (RSV) infection at the level of cytokine mRNA expression was examined in a murine model in the present study. Primary RSV infection enhances expression of inflammatory cytokines such as IL-6, IFN-gamma, and eotaxin in the lung and upregulates the expression of Th2-like cytokines IL-10 and IL-13 in the spleen in BALB/c mice. Mite antigen-sensitized and RSV-infected (ASRSV) mice show enhanced (P < 0.05) total serum IgE compared to antigen-sensitized mice. However, the levels of viral mRNA in the lung tissues are comparable between RSV-infected and ASRSV mice. It is concluded that compartmentalization of cytokine expression following RSV infection plays a role in the augmentation of Th2-like and IgE antibody response to RSV.

Intranasal IFN-gamma gene transfer protects BALB/c mice against respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is a major respiratory pathogen in infants, young children and the elderly and causes severe bronchiolitis and asthma. In an effort to develop a preventive IFN-gamma therapy against RSV infection, an intranasal gene transfer strategy was utilized. Intranasal administration of a plasmid expressing the IFN-gamma cDNA (pIFN-gamma) resulted in the expression of IFN-gamma in murine lungs and decreased RSV replication. The mice administered with pIFN-gamma and then infected with RSV exhibited a significant decrease in broncho-alveolar lavage lymphocyte and neutrophil counts. A significant reduction in epithelial cell damage, infiltration of mononuclear cells in the peribronchiolar and perivascular regions, and thickening of the septa was observed in the lungs of mice treated with pIFN-gamma when compared to controls. These results suggest that intranasal IFN-gamma gene transfer results in decreased RSV replication and pulmonary inflammation and may be useful against RSV infection.

A recombinant BCG vaccine generates a Th1-like response and inhibits IgE synthesis in BALB/c mice

The tubercle vaccine, bacille Calmette-Guérin (BCG), is a strong inducer of T-helper type 1 (Th1) responsiveness, and it has been suggested that recombinant BCG (rBCG), which produces and secretes antigens, may be used to prevent allergic diseases. The effects of rBCG vaccination on allergic responses in a murine model were examined in this study. A BCG-Escherichia coli shuttle vector was developed with the promoter and signal sequence of the alpha-antigen of Mycobacterium bovis, and the vector was tested using E. coli beta-galactosidase as the model antigen and allergen. This vector enabled the expression of the E. coli beta-galactosidase gene in BCG, which was detected in its protein extract by immunoblotting analysis. Vaccination of mice with a single dose of 106 recombinant BCG generated a beta-galactosidase-specific antibody response. The splenocytes of vaccinated mice compared with controls produced significantly higher amounts of interferon-gamma (IFN-gamma) (P<0. 01) and interleukin-2 (IL-2) (P<0.05) and lower amounts of IL-5 (P<0. 01). Mice vaccinated with rBCG had significantly less (P<0.01) serum IgE compared with controls. These results together demonstrate that rBCG secreting antigens or allergens may be utilized for the induction of a Th1-like response and the down-regulation of IgE antibody response.

Respiratory syncytial virus induces the expression of 5-lipoxygenase and endothelin-1 in bronchial epithelial cells

Respiratory syncytial virus (RSV) infection causes and exacerbates asthma, yet the mechanism by which RSV triggers asthma is poorly understood. Herein, an in vitro model of RSV infection was established using HEp-2 and BEAS-2B bronchial epithelial cell lines, and the expression of 5-lipoxygenase (5-LO), and endothelin-1 (ET-1) was examined. RSV infection increased the expression of 5-LO mRNA and protein in both cell lines, as detected by RT-PCR and western blot analysis, respectively. The levels of leukotrienes also increased in the supernatants of RSV infected cells. Furthermore, RSV infection increased the expression of ET-1 mRNA and protein following RSV infection in a time-dependent manner. It is concluded that RSV infection upregulates the expression of ET-1 and 5-LO in the epithelial cells leading to the production of leukotrienes, which may mediate the consequent exacerbation of asthma.

CD8+ T cells inhibit immunoglobulin E synthesis in low responder SJL/J mice

In an effort to examine the basis for low IgE responsiveness of SJL/J strain mice, we analysed the profiles of cytokines, such as interleukin-2 (IL-2), IL-4 and interferon-gamma (IFN-gamma), in SJL/J and A.SW/SnJ mice following immunization. Splenocytes of ovalbumin (OVA)-immunized SJL/J mice, secreted significantly higher levels of IL-4 and lower levels of IFN-gamma than those of A.SW/SnJ mice. A time-course analysis of cytokine expression in in vitro cultures of spleen cells indicated that the levels of IL-4 and IL-2 remained persistently high throughout in the cultures of SJL/J splenocytes as opposed to those of A.SW/SnJ. Depletion of CD4+ T cells in vivo suppressed the production of IL-2, IL-4 and IFN-gamma suggesting that CD4 T cells are the producers of most cytokines in both SJL/J and A.SW/SnJ mice. Depletion of CD8+ T cells in vivo not only induced productive epsilon transcript but also enhanced IgE production in SJL/J mice. Moreover, CD8 depletion in SJL/J mice led to decreased production of IFN-gamma, resulting in a net decrease in the ratio of IFN-gamma to IL-4. A similar shift in the IFN-gamma/IL-4 ratio was found in splenocytes of SJL/J mice following irradiation, which is known to enhance IgE synthesis in these mice. Taken together, it is concluded that low IgE responsiveness in SJL/J mice is not due to a defect in IL-4 production per se. Increased IFN-gamma production by the CD8+ T cells inhibits class switch and suppresses IgE antibody production in SJL/J mice.

Airway responsiveness in two inbred strains of mouse disparate in IgE and IL-4 production

The mouse provides an excellent model for genetic studies of asthma, which is characterized by airway hyperexcitability and hyperreactivity. The former is a function of the properties of the membrane of the airway smooth muscle (ASM), whereas the latter is a function, albeit indirectly, of the mechanical properties of the muscle contractile apparatus. The very small size of the muscle has in the past hampered its study. We report herein that contractile properties of tracheal smooth muscle (TSM) can be measured in mice. We examined TSM strips from two inbred strains of mouse, ASW and SJL, which are high and low IgE responders, respectively. Force-velocity relationships were measured in four groups of mice, two ASW (control and sensitized)/and two SJL (control and sensitized). Muscle strips from sensitized SJL mice exhibited shortening velocities (V0) and maximum shortening capacities (deltaLmax), that were significantly greater than those of the other groups. However, no difference was found between the two strains in maximal isometric force (P0). The two strains also showed differences in their potential to express cytokines such as interleukin-4 (IL-4) and IL-5 in ex vivo splenocyte cultures, as measured by the cytokines' messenger RNA (mRNA) and protein expression. The SJL strain, which exhibited TSM hyperreactivity, was found to produce significantly greater amounts of IL-4 than the ASW strain. We conclude that the altered contractile properties of TSM in sensitized SJL mice are independent of IgE response, but linked to increased amounts of IL-4.

Vaccination with a multi-epitopic recombinant allergen induces specific immune deviation via T-cell anergy

Prophylactic vaccination has recently emerged as a major paradigm toward the prevention and therapy of allergies and asthma; however, the immunological basis of this approach remains to be elucidated. We examined the potential and mechanism of prophylaxis of allergic response in B6D2F1 mice with a multi-epitopic recombinant allergen, rKBG8.3 (MERA-8.3), which represents a major group of allergens of grass pollens, used herein as a model of MERA vaccine. Vaccination (subcutaneous) with soluble MERA-8.3, prior to immunization with the MERA-8.3 in alum, led to suppression of the IgE antibody response and a concomitant increase in IgG2a antibody response specific to the MERA-8.3 in a dose-dependent manner. Analysis of cytokine patterns in spleen and lymph node cells revealed a marked decrease of interleukin-2 (IL-2) and IL-4 production and to a lesser extent a decrease of interferon-gamma (IFN-gamma) synthesis, resulting in an increased ratio of IFN-gamma: IL-4 in vaccinated-immunized mice compared with untreated-immunized control mice. Furthermore, splenocytes of mice treated with the MERA-8.3 alone proliferated to MERA-8.3 in vitro with reduced capacity compared with the splenocytes of MERA-8.3-alum immunized mice, owing to a markedly reduced level of IL-2 production in the former. Collectively, these results suggest that vaccination with the MERA-8.3 induces T-cell anergy, which is pivotal to deviation of specific immunity from Th2- to Th1-like, and may serve as an important approach to prevention and therapy of allergic disorders.

Host genetic and adjuvant factors influence epitope specificity to a major recombinant grass allergen

The role of host genetic and adjuvant factors in the induction of immune responses to a major recombinant Kentucky bluegrass allergen was examined utilizing five strains of mice and two different adjuvants. Analysis of the recombinant allergen-specific antibodies induced in these strains indicated that the antibodies of various isotypes were differentially regulated. In terms of IgE antibody response, BDF1 and DBA/2 were characterized as high responder, whereas BALB/C, CBA/J and C57BL/6 were intermediate and SJL was a low responder. In different strains, both dextran sulfate (DS) and complete Freund's adjuvant (CFA), as adjuvants, induced recombinant allergen-specific IgE antibodies of similar titer, however, CFA induced higher IgG2a and lower IgM antibodies compared to DS. Further, analysis of T cell proliferative responses of the splenocytes of different strains demonstrated that these strains varied also in their capacity to respond to synthetic peptides. Furthermore, utilizing a panel of synthetic peptides corresponding to the recombinant allergen, we demonstrated that the antibodies induced by the recombinant allergen with CFA in different strains vary with respect to their epitope specificity. In the BDF1 strain, compared to DS, CFA as adjuvant induced recombinant allergen-specific antibodies of additional peptide specificity. Taken together, these results suggest that both host genetic background and adjuvants govern the fine specificity of antibodies produced against this recombinant Kentucky bluegrass allergen.

Multiple B- and T-cell epitopes on a major allergen of Kentucky Bluegrass pollen

The B- and T-cell epitopes of a recombinant grass allergen, rKBG60, were delineated using a set of overlapping synthetic peptides. Direct binding by enzyme-linked immunosorbent assay (ELISA) utilizing serum pools led to the identification of 13 murine immunoglobulin-, and nine to 13 human IgG- and five to seven human IgE-reactive overlapping peptides. Of the peptides which bound to human IgE antibodies, all but three peptides bound to human and/or murine IgG antibodies. Furthermore, eight out of 12 synthetic peptides induced antigen-specific antibodies in mice, suggesting that these peptides contained epitopes that recognized and/or induced T cells. These results, in conjunction with cross-recognition of different peptides at the C-terminus of rKBG60 by antibodies to neighbouring or non-overlapping peptides suggest that the C-terminus of this antigen represents a dominant antigenic and allergenic site. Peripheral blood mononuclear cell (PBMC) proliferation studies using these synthetic peptides for 13 grass allergic individuals indicated that seven potential human T-cell epitopes exist on this allergen. Taken together, the results demonstrate that multiple B- and T-cell epitopes exist on this major group of grass allergens, the majority of which are localized at the C-terminus of this antigen.

Analysis of Tcrvb8, Il4, and Ifg as genetic predisposition factors for atopic IgE response in a murine model

Allergen-induced synthesis of lgE Abs in genetically predisposed individuals constitutes the hallmark of allergic diseases; however, the molecular basis of this genetic predisposition remains unknown. T cell cytokines lL-4 and IFN-gamma reciprocally regulate lgE synthesis and are potential genetic factors governing atopy. To examine the inheritance patterns of IgE responsiveness and address the role of these cytokines as genetic predisposition factors, in this study we established a MHC-identical mouse colony comprising crosses between two inbred strains of mouse, A.SW and SJL, respectively representing high and low IgE responder phenotypes. Segregation analysis with 149 [(A.SW x SJL)F1 x SJL] backcross and 148 [(A.SW x SJL)F1 x F1]F2 mice suggested that persistent high IgE responsiveness was inherited as a simple Mendelian dominant trait under the control of a single non-MHC, autosomal gene of major effect in these strains. Since SJL lacked Tcrvb8 genes, we examined the possibility of Tcrvb8 as a candidate gene for IgE responsiveness. The results suggested association of neither the Tcrvb8 gene nor its expression with allergen-induced IgE phenotype. Furthermore, microsatellite marker and gene sequencing analyses revealed that neither of the ll4 and lfg genes was associated with IgE phenotype. Moreover, correlation studies between IgE and cytokine levels in splenocyte cultures indicated that IgE levels were moderately to poorly correlated with IL-4 and IFN-gamma levels. It is concluded that even though expression of Tcrvb8, II4, and Ifg genes may play pivotal roles in IgE regulation, these genes per se do not contribute to genetic predisposition of allergen-induced IgE hyperresponsiveness in these strains of mice.

Analysis of Tcrvb8, Il4, and Ifg as genetic predisposition factors for atopic IgE response in a murine model

Allergen-induced synthesis of lgE Abs in genetically predisposed individuals constitutes the hallmark of allergic diseases; however, the molecular basis of this genetic predisposition remains unknown. T cell cytokines lL-4 and IFN-gamma reciprocally regulate lgE synthesis and are potential genetic factors governing atopy. To examine the inheritance patterns of IgE responsiveness and address the role of these cytokines as genetic predisposition factors, in this study we established a MHC-identical mouse colony comprising crosses between two inbred strains of mouse, A.SW and SJL, respectively representing high and low IgE responder phenotypes. Segregation analysis with 149 [(A.SW x SJL)F1 x SJL] backcross and 148 [(A.SW x SJL)F1 x F1]F2 mice suggested that persistent high IgE responsiveness was inherited as a simple Mendelian dominant trait under the control of a single non-MHC, autosomal gene of major effect in these strains. Since SJL lacked Tcrvb8 genes, we examined the possibility of Tcrvb8 as a candidate gene for IgE responsiveness. The results suggested association of neither the Tcrvb8 gene nor its expression with allergen-induced IgE phenotype. Furthermore, microsatellite marker and gene sequencing analyses revealed that neither of the ll4 and lfg genes was associated with IgE phenotype. Moreover, correlation studies between IgE and cytokine levels in splenocyte cultures indicated that IgE levels were moderately to poorly correlated with IL-4 and IFN-gamma levels. It is concluded that even though expression of Tcrvb8, II4, and Ifg genes may play pivotal roles in IgE regulation, these genes per se do not contribute to genetic predisposition of allergen-induced IgE hyperresponsiveness in these strains of mice.

Comparison of IgE and IgG antibody responses of atopic individuals with sensitization to tree and grass pollens

Sera of atopic individuals with predominant sensitization to either tree pollen (TAs) or tree and grass pollens (TGAs) as well as of nonatopic subjects (NAs) were analyzed for IgE, IgG, and IgG4 antibodies specific for grass pollens allergens. Of 600 atopic individuals with serum IgE antibodies specific for birch pollen allergens, 54% also had serum IgE antibodies specific for grass pollen. The mean titers of IgG antibodies specific for grass pollen proteins were about 10 times higher in the sera of TGAs than those in the TAs and NAs. SDS-PAGE immunoblotting analysis of grass pollen proteins using sera of TGAs, TAs, and NAs with respect to the binding of these proteins with IgE and IgG antibodies in these sera exhibited a similar pattern of variation. Quantitation by enzyme immunoassay of the antibody binding to a recombination grass pollen allergen, rKBG8.3, further demonstrated the elevated IgG antibody levels in TGAs are mainly due to a broader range of specificities, and not to high specific binding to the individual protein. Statistically significant correlation was found between IgE and IgG4 antibodies specific for the Kentucky bluegrass (KBG) extract, but not for the isolated recombinant allergen. These results indicate that the grass pollens elicit a complex array of antibody specificities in both atopics and nonatopics, and that the profile of antibodies specific to the pollen extract and pure allergens differs, suggesting that single grass allergens may be inadequate for replacing grass pollen extracts for immunotherapy.

Pollen allergen homologues in barley and other crop species

Pollen from 10 agricultural plant species was surveyed for the presence of proteins crossreactive with group I, group IV and group IX allergens. Barley (Hordeum vulgare), maize (Zea mays), rye (Secale cerale), triticale (xTriticosecale cereale), oats (Avena sativa), Canola (Brassica napus) and sunflower (Helianthus annus) pollens contained numerous allergen cognate proteins. Northern blot analysis of barley pollen RNA revealed the presence of group I and group IX allergen transcripts. The barley pollen cDNA hvp9742, and three other cloned allergens: phlenum protense (Phl p) V, Phl p Va and Lolium perenne (Lol p) 1b, were demonstrated to have extensive nucleotide and amino acid sequence similarity to the Poa p IX isoallergens. It was concluded that hvp9742 represents a Poa p IX isoallergen homologue expressed by barley pollen, and was therefore designated Hor v IX. It is further shown that the most highly conserved domains of all seven proteins, including Hor v IX, map to previously defined Poa p IX antibody binding epitopes.

Arbitrary single short primers identify polymorphic DNA markers that distinguish inbred strains of mice

The inbred mouse strains, Balb/c and SJL/J, have been widely used in biomedical research to unravel the genetic basis of susceptibility to tumors, viral diseases, autoimmune encephalitis, atopic disorders and neuro-retinopathies. In this study we attempted to identify DNA polymorphisms that distinguish them using RAPD assay. Screening of the genomic DNA of mice with a panel of 100 random decamer primers led to the identification of 36 primers which amplified 204 strain specific RAPD markers. On an average each of the selected primer amplified 11 bands of which 5.6 were strain specific. Segregation of RAPD markers in a (Balb/c x SJL/J) F1 x SJL/J backcross progeny (n = 6) suggested that the markers are potentially suitable for molecular genetic linkage studies.

Recombinant allergens and diagnosis of grass pollen allergy

To evaluate the use of recombinant allergens for the diagnosis of grass pollen allergies, we examined the levels of IgE antibodies specific for grass pollen as by immunoassays. SDS-PAGE analysis of two batches of Kentucky bluegrass pollen extracts demonstrated that there was considerable variability in allergen content of extracts, which in turn affected quantitation of specific IgE antibodies by different immunoassay procedures. Furthermore, the levels of IgE antibodies in human sera specific for a recombinant grass pollen allergen, rKBG8.3, were examined by enzyme immunoassay. The results demonstrated that quantitation of IgE antibodies specific for even one single allergen may be used to discriminate sera of allergic individuals with respect to IgE specific for grass pollen in general. A positive correlation, r = .82, was found for IgE binding of the recombinant allergen and the crude extracts of grass pollens. It is concluded from these results that a single recombinant allergen or a combination of a few major recombinant allergens can substitute the crude extract for in vitro as well as in vivo diagnostic purposes.

The suppressor factor of T suppressor cells induced by tolerogenic conjugates of ovalbumin and monomethoxypolyethylene glycol is serologically and physicochemically related to the alpha beta heterodimer of the T cell receptor

Ovalbumin-specific, H-2Kd restricted, CD8+ Ts cells of clone 17.2 were shown to produce an OVA-specific Ts cell factor (TsF17.2) possessing the same Ag specificity and MHC restriction as those of the intact Ts cells. The Ts cell clone was generated from a single cell of the spleen of a mouse which had been immunosuppressed by injection of tolerogenic OVA(mPEG)12 conjugate. For the elucidation of the nature of TsF17.2, it was characterized by serologic, physicochemical, and Western blot analyses. It was found that 1) the OVA-specific suppression of in vitro antibody production by TsF17.2 could be blocked by mAb H28-710 which binds to an epitope of the constant region of the alpha-chain of TCR; 2) the TsF17.2 could be sequestered by, and eluted from, immunosorbents prepared by coupling to Affi-Gel Hz the H28-710 mAb or the mAb H57-597 and F23.1 which are specific, respectively, for an epitope of the constant region of the beta-chain and an epitope of the V beta 8 region of the TCR; and 3) the TsF17.2 had a pl of 7.0, m.w. of 84,000, and consisted of two disulfide-linked subunits of 42,000 each. After electroelution from the SDS-PAGE gel, the m.w. 84,000 molecule retained its capacity to suppress in vitro antibody production in an OVA-specific manner. From all these results it was concluded that this Ts cell factor may represent a soluble form of the alpha beta heterodimer of TCR of cloned Ts cells.

The suppressor factor of T suppressor cells induced by tolerogenic conjugates of ovalbumin and monomethoxypolyethylene glycol is serologically and physicochemically related to the alpha beta heterodimer of the T cell receptor

Ovalbumin-specific, H-2Kd restricted, CD8+ Ts cells of clone 17.2 were shown to produce an OVA-specific Ts cell factor (TsF17.2) possessing the same Ag specificity and MHC restriction as those of the intact Ts cells. The Ts cell clone was generated from a single cell of the spleen of a mouse which had been immunosuppressed by injection of tolerogenic OVA(mPEG)12 conjugate. For the elucidation of the nature of TsF17.2, it was characterized by serologic, physicochemical, and Western blot analyses. It was found that 1) the OVA-specific suppression of in vitro antibody production by TsF17.2 could be blocked by mAb H28-710 which binds to an epitope of the constant region of the alpha-chain of TCR; 2) the TsF17.2 could be sequestered by, and eluted from, immunosorbents prepared by coupling to Affi-Gel Hz the H28-710 mAb or the mAb H57-597 and F23.1 which are specific, respectively, for an epitope of the constant region of the beta-chain and an epitope of the V beta 8 region of the TCR; and 3) the TsF17.2 had a pl of 7.0, m.w. of 84,000, and consisted of two disulfide-linked subunits of 42,000 each. After electroelution from the SDS-PAGE gel, the m.w. 84,000 molecule retained its capacity to suppress in vitro antibody production in an OVA-specific manner. From all these results it was concluded that this Ts cell factor may represent a soluble form of the alpha beta heterodimer of TCR of cloned Ts cells.

Molecular basis of cross-reactivity among allergen-specific human T cells: T-cell receptor V alpha gene usage and epitope structure

Cross-reactivities between the major grass pollen allergens, at the level of T-cell recognition was examined employing several Lolium perenne I (Lol p I)-specific human T-cell clones. Nine of these Lol p I-specific T-cell clones exhibited cross-recognition of the recombinant Poa pratensis IX (Poa p IX) allergen, rKBG7.2, indicating that these two major antigens of a grass pollen share T-cell epitopes. Furthermore, proliferative responses of two other T-cell clones demonstrated that individual allergens of diverse grass pollens also possess common T-cell epitopes. Examination of the T-cell receptor (TcR) V alpha genes of these T-cell clones indicated that these cloned cells utilized distinct J alpha genes and that nine out of 10 clones possessed V alpha 13 gene. Furthermore, sequence comparisons of several allergenic molecules indicated that this cross-reactivity may be due to the presence of epitope(s) with structure(s) similar to the major T-cell epitope of Poa p IX allergens. Taken together, these results suggest for the first time that the major grass pollen allergens share cross-reacting T-cell epitope(s), and that this cross-reactivity is due to the structural homologies among allergens and restricted usage of TcR V alpha genes.

Antigen- and isotype-specific immune responses to a recombinant antigen-allergen chimeric (RAAC) protein

Ag-specific IgE and IgG antibody responses to a recombinant Ag-allergen chimeric (RAAC) protein were examined in B6D2F1 mice. The RAAC protein consisted of the truncated beta-galactosidase (beta-gal), linked at its C terminus to a polypeptide representing the conserved region of the recombinant Kentucky Bluegrass allergen encoded by the cDNA clone KBG8.3(rKBG8.3). Immunization of the mice with the RAAC protein in dextran sulfate as adjuvant led to the differential production of antibodies to the two constituents of RAAC protein with respect to their isotypic classes. Most of the antibody responses to both sets of determinants on the fusion protein were IgG1. In addition, the allergenic polypeptide of RAAC protein induced IgE antibodies, whereas the beta-gal elicited IgG2a antibodies. The same pattern of antibody isotypes was produced when the individual components, rKBG8.3 and beta-gal were separately used for immunization with dextran sulfate. On the other hand, immunization of mice with either RAAC or the beta-gal in CFA induced primarily a IgG response, and no IgE antibodies; however, under the same conditions of immunization rKBG8.3 induced IgG1 antibodies and also low levels of IgE antibodies. In contrast, the RAAC and the beta-gal induced IgG2a antibodies, whereas rKBG8.3 induced no detectable IgG2a antibodies. Furthermore, high titers of IgE antibodies were induced by the rKBG8.3 and not by the RAAC protein in dextran sulfate after the mice had been immunized twice with the same polypeptide in CFA. It is inferred from these results that the induction of isotype-specific immune responses in the animals with the same genetic background is dependent upon the Ag in question as well as the adjuvant; the latter, however, influences the magnitude but does not determine the isotype of the immune responses.

Analysis of T-cell receptor alpha beta chains of CD8+ suppressor T cells induced by tolerogenic conjugates of antigen and monomethoxypolyethylene glycol. Involvement of TCR alpha-CDR3 domain in immunosuppression

A number of investigators have demonstrated that there exists a relationship between Ag receptors of Ts cells (TCR) and their soluble suppressor factors. With a view to elucidating this relationship, the primary structures of receptors of Ts cells, induced in mice by tolerogenic conjugates of Ag and monomethoxypolyethylene glycol, were characterized in this study. The cDNA encoding the alpha and beta chains of TCR of cloned Ts cells specific for (i) OVA and (ii) human monoclonal (myeloma) IgG (HIgG) were produced by polymerase chain reaction. From the analysis of the V alpha genes of TCR of Ts cells it was deduced that these receptors utilized a new member of the V alpha 15 gene family, which was productively joined to the J alpha genes that differed for each of the Ts cells of the two distinct specificities. Similarly, sequence analysis of the beta chain cDNA of the two Ts cell clones revealed that both clones utilized the V beta 8.2 gene, and that their J beta gene differed from each other. It is inferred that the Ts cells generated in response to the different tolerogenic Ag(mPEG)n conjugates belonged to a subset of T cells utilizing similar TCR alpha beta chains and differed only in their J alpha/J beta regions. Most importantly, pretreatment of mice with a mixture of pentadecapeptides comprising the TCR alpha chain of the OVA-Ts cells, down-regulated the immune response specific to OVA, but not to HIgG. Moreover, injection of mice with a pentadecapeptide corresponding to the CDR3 region of the TCR alpha chain of either OVA-Ts or HIgG-Ts suppressed specifically the Ab response to OVA or HIgG, respectively. On the basis of all these results, it is concluded that the CDR3 of the TCR-alpha chain of Ts cells plays a pivotal role in the Ts network underlying the specific down-regulation of the immune responses induced by tolerogenic Ag(mPEG)n conjugates.

Analysis of T-cell receptor alpha beta chains of CD8+ suppressor T cells induced by tolerogenic conjugates of antigen and monomethoxypolyethylene glycol. Involvement of TCR alpha-CDR3 domain in immunosuppression

A number of investigators have demonstrated that there exists a relationship between Ag receptors of Ts cells (TCR) and their soluble suppressor factors. With a view to elucidating this relationship, the primary structures of receptors of Ts cells, induced in mice by tolerogenic conjugates of Ag and monomethoxypolyethylene glycol, were characterized in this study. The cDNA encoding the alpha and beta chains of TCR of cloned Ts cells specific for (i) OVA and (ii) human monoclonal (myeloma) IgG (HIgG) were produced by polymerase chain reaction. From the analysis of the V alpha genes of TCR of Ts cells it was deduced that these receptors utilized a new member of the V alpha 15 gene family, which was productively joined to the J alpha genes that differed for each of the Ts cells of the two distinct specificities. Similarly, sequence analysis of the beta chain cDNA of the two Ts cell clones revealed that both clones utilized the V beta 8.2 gene, and that their J beta gene differed from each other. It is inferred that the Ts cells generated in response to the different tolerogenic Ag(mPEG)n conjugates belonged to a subset of T cells utilizing similar TCR alpha beta chains and differed only in their J alpha/J beta regions. Most importantly, pretreatment of mice with a mixture of pentadecapeptides comprising the TCR alpha chain of the OVA-Ts cells, down-regulated the immune response specific to OVA, but not to HIgG. Moreover, injection of mice with a pentadecapeptide corresponding to the CDR3 region of the TCR alpha chain of either OVA-Ts or HIgG-Ts suppressed specifically the Ab response to OVA or HIgG, respectively. On the basis of all these results, it is concluded that the CDR3 of the TCR-alpha chain of Ts cells plays a pivotal role in the Ts network underlying the specific down-regulation of the immune responses induced by tolerogenic Ag(mPEG)n conjugates.

Antigen- and isotype-specific immune responses to a recombinant antigen-allergen chimeric (RAAC) protein

Ag-specific IgE and IgG antibody responses to a recombinant Ag-allergen chimeric (RAAC) protein were examined in B6D2F1 mice. The RAAC protein consisted of the truncated beta-galactosidase (beta-gal), linked at its C terminus to a polypeptide representing the conserved region of the recombinant Kentucky Bluegrass allergen encoded by the cDNA clone KBG8.3(rKBG8.3). Immunization of the mice with the RAAC protein in dextran sulfate as adjuvant led to the differential production of antibodies to the two constituents of RAAC protein with respect to their isotypic classes. Most of the antibody responses to both sets of determinants on the fusion protein were IgG1. In addition, the allergenic polypeptide of RAAC protein induced IgE antibodies, whereas the beta-gal elicited IgG2a antibodies. The same pattern of antibody isotypes was produced when the individual components, rKBG8.3 and beta-gal were separately used for immunization with dextran sulfate. On the other hand, immunization of mice with either RAAC or the beta-gal in CFA induced primarily a IgG response, and no IgE antibodies; however, under the same conditions of immunization rKBG8.3 induced IgG1 antibodies and also low levels of IgE antibodies. In contrast, the RAAC and the beta-gal induced IgG2a antibodies, whereas rKBG8.3 induced no detectable IgG2a antibodies. Furthermore, high titers of IgE antibodies were induced by the rKBG8.3 and not by the RAAC protein in dextran sulfate after the mice had been immunized twice with the same polypeptide in CFA. It is inferred from these results that the induction of isotype-specific immune responses in the animals with the same genetic background is dependent upon the Ag in question as well as the adjuvant; the latter, however, influences the magnitude but does not determine the isotype of the immune responses.

Cytokine gene expression of CD8+ suppressor T cells induced by tolerogenic conjugates of antigen and mPEG

Nonhybridized CD8+ Ts cell clones were generated from individual spleen cells of a B6D2F1 mouse, which had been immunosuppressed in an antigen-specific manner by administration of tolerogenic conjugates of ovalbumin (OVA) and monomethoxypolyethylene glycol. The cloned Ts cells were shown to suppress both in vivo and in vitro anti-OVA antibody formation in an antigen-specific and isotype-nonspecific manner, i.e., IgM, IgG1, and IgG2a anti-OVA antibodies were suppressed. The cytokine profile of three Ts cell clones was determined by bioassays, Western blot, and polymerase chain reaction analyses. It was shown that all the Ts cell clones produced IL-2, IL-4, IFN-gamma, TGF-beta 1, LT, and TNF-alpha upon activation with hamster anti-CD3 monoclonal antibody (mAb) or antigen plus APC. However, neither the mAbs to IFN-gamma, TGF-beta, or LT/TNF-alpha, nor the recombinant IL-2 was able to abrogate the suppression of in vitro antibody production by cloned Ts cells. These data are taken to indicate that (i) the cloned Ts cells suppress anti-OVA antibody production both in vivo and in vitro in an isotype-nonrestricted manner, (ii) the cytokine profile of these cloned Ts cells is similar to that of Th0 cells, and (iii) the immunosuppression mediated by these T cells is not directly related to the cytokines produced by cloned Ts cells.

Mapping of antibody binding epitopes of a recombinant Poa p IX allergen

Antibody binding epitopes of a recombinant Poa p IX allergen were delineated using recombinant DNA and solid-phase peptide synthesis procedures. The full-length cDNA clone KBG60 and its four overlapping recombinant fragments, KBG60.1, KBG60.2, KBG8.3 and KBG10 which spanned the entire molecule were synthesized in E. coli with aid of the plasmid expression vector, pWR590.1. The antigenic and allergenic sites of these recombinant proteins were analyzed by ELISA using human IgE and murine IgG antibodies. It was thus demonstrated that although the epitopes were found on all the fragments tested, the majority of these were located on a C-terminal fragment, rKBG8.3. Furthermore, synthetic peptides were also employed to identify the epitopes of rKBG60 protein. The use of antisera raised against native KBG pollen extract and the recombinant KBG8.3 protein to scan a total of 56 overlapping deca-penta peptides, covering the entire rKBG60 protein, revealed that 10 positive peptides involved in the antibody-binding site(s). Taken together, the results of these studies indicate that rKBG60 protein possesses at least 10 antibody binding epitopes.

Characterization of a gene family encoding abscisic acid- and environmental stress-inducible proteins of alfalfa

The phytohormone abscisic acid (ABA) has been proposed as a common mediator controlling adaptive plant responses to a variety of environmental stresses, including water deficit, salinity, wounding, and low temperature. We have recently isolated three cDNAs, pUM90-1, pUM90-2, and pUM91-4, from a cDNA library of ABA-induced mRNAs of alfalfa. These cDNA clones exhibit a very high degree of sequence homology with one another and sequence similarities with certain regions of several stress- and ABA-inducible genes. The polypeptides encoded by these cDNAs are very rich in glycine (35-40%), histidine (7-15%), asparagine (8-14%), and tyrosine (5-10%) and have no tryptophan and proline. All of the encoded polypeptides contain characteristic tandem repeats comprising glycine residues intercepted with histidine and/or tyrosine. The RNAs corresponding to a representative cDNA, pUM90-1, were induced after treatment of seedlings with low temperature, drought, salt, and wounding stress, but not by heat; the induction was maximal under low temperature treatment. ABA and ABA analog rapidly induced the expression of these genes, whereas gibberellic acid treatment exhibited no induction whatsoever. These genes appear to be specifically induced in the shoot tissues. Analysis of ABA induction of genes corresponding to pUM90-1 in alfalfa seedlings of different age groups demonstrated that these genes were inducible in seedlings/plants of all age groups examined. Taken together these results suggest that these cDNA clones encode a group of proteins that are inducible by ABA and multiple environmental stresses and correspond to a new family of genes of plants, designated as ABA- and environmental stress-inducible genes.

Some observations on Plasmodium falciparum gametocytaemia in natural infections in an endemic area of Koraput district, Orissa

Peripheral P. falciparum gametocytaemia with respect to its minimum average time taken for appearance in peripheral blood, its peak density, duration of persistence in peripheral circulation, conversion rate and sex ratio was studied in 22 persons with natural infections in a village of Koraput district, Orissa. The minimum average time taken for the appearance of gametocytes was 9.3 days in children (below 15 years) and 8.9 days in adults (15 years and above). The peak count was low, the maximum density being 31/microliters. The duration of gametocytaemia in peripheral circulation was also short, the longest being 32 days. The gametocyte conversion rate on an average was 0.74% in children and 2.04% in adults. The mean sex ratio of micro:macro gametocytes was 1:2.6 in children and 1:6.2 in adults.

Induction of IgE antibodies in mice with recombinant grass pollen antigens

In this study, recombinant Poa pratensis (Poa p) IX allergens were examined for their in vivo allergenicity and antigenicity. Immunization of mice with a fusion protein (FP) comprising beta-galactosidase and recombinant KBG8.3 (rKBG8.3) allergen induced high titres of both IgG and IgE antibodies. By contrast, immunization with rKBG60.2, which represents the N-terminal fragment of rKBG8.3, induced only IgG antibodies. The IgE antibody titre specific to Kentucky Bluegrass (KBG) was significantly higher than that to beta-galactosidase. Moreover, KBG-specific IgE antibodies showed no apparent decrease in their titres until 60 days after immunization, whereas the beta-galactosidase-specific IgE antibodies disappeared after 40 days. The antibodies induced with rKBG8.3 in mice were capable of inhibiting the binding of human IgE antibodies to KBG pollen allergens, which indicated that rKBG8.3-specific murine antibodies recognized epitopes similar to those recognized by human IgE antibodies. Analysis of allergenic cross-reactivities of rKBG8.3 with components from five other species of grass pollens revealed that IgE antibodies induced by this allergen are capable of binding in vivo to components from other grass pollens. These results suggest that the mouse may serve as a model for the manipulation of IgE responses to recombinant allergens or their chemically modified derivatives.