A CRISPR activation screen identifies MUC-21 as critical for resistance to NK and T cell-mediated cytotoxicity

BACKGROUND

Immunotherapy has significantly advanced cancer treatments, but many patients do not respond to it, partly due to immunosuppressive mechanisms used by tumor cells. These cells employ immunosuppressive ligands to evade detection and elimination by the immune system. Therefore, the discovery and characterization of novel immunosuppressive ligands that facilitate immune evasion are crucial for developing more potent anti-cancer therapies.

METHODS

We conducted gain-of-function screens using a CRISPRa (CRISPR activation) library that covered the entire human transmembrane sub-genome to identify surface molecules capable of hindering NK-mediated cytotoxicity. The immunosuppressive role and mechanism of MUC21 were validated using NK and T cell mediated cytotoxicity assays. Bioinformatics tools were employed to assess the clinical implications of mucin-21 (MUC21) in cancer cell immunity.

RESULTS

Our genetic screens revealed that MUC21 expression on cancer cell surfaces inhibits both the cytotoxic activity of NK cells and antibody-dependent cellular cytotoxicity, but not affecting complement-dependent cytotoxicity. Additionally, MUC21 expression hinders T cell activation by impeding antigen recognition, thereby diminishing the effectiveness of the immune checkpoint inhibitor, anti-PD-L1. Moreover, MUC21 expression suppress the antitumor function of both CAR-T cells and CAR-NK cells. Mechanistically, MUC21 facilitates immune evasion by creating steric hindrance, preventing interactions between cancer and immune cells. Bioinformatics analysis revealed elevated MUC21 expression in lung cancer, which correlated with reduced infiltration and activation of cytotoxic immune cells. Intriguingly, MUC21 expression was higher in non-small cell lung cancer (NSCLC) tumors that were non-responsive to anti-PD-(L)1 treatment compared to responsive tumors.

CONCLUSIONS

These findings indicate that surface MUC21 serves as a potent immunosuppressive ligand, shielding cancer cells from NK and CD8+T cell attacks. This suggests that inhibiting MUC21 could be a promising strategy to improve cancer immunotherapy.

LAG-3xPD-L1 bispecific antibody potentiates antitumor responses of T cells through dendritic cell activation

Several preclinical studies demonstrate that antitumor efficacy of PD-1/PD-L1 blockade can be improved by combination with other checkpoint inhibitors. Lymphocyte-activation gene 3 (LAG-3) is an inhibitory checkpoint receptor involved in T cell exhaustion and tumor immune escape. Here, we describe ABL501, a bispecific antibody targeting LAG-3 and PD-L1 in modulating immune cell responses against tumors. ABL501 that efficiently inhibits both LAG-3 and PD-L1 pathways enhances the activation of effector CD4⁺ and CD8⁺ T cells with a higher degree than a combination of single anti-LAG-3 and anti-PD-L1. The augmented effector T cell responses by ABL501 resulted in mitigating regulatory T cell-mediated immunosuppression. Mechanistically, the simultaneous binding of ABL501 to LAG-3 and PD-L1 promotes DC activation and tumor cell conjugation with T cells that subsequently mounts effective CD8⁺T cell responses. ABL501 demonstrates its potent in vivo antitumor efficacy in a humanized xenograft model and with knock-in mice expressing human orthologs. The immune profiling analysis of peripheral blood reveals an increased abundance of LAG-3^hiPD-1^hi memory CD4⁺T cell subset in relapsed cholangiocarcinoma patients after gemcitabine plus cisplatin therapy, which are more responsive to ABL501. This study supports the clinical evaluation of ABL501 as a novel cancer immunotherapeutic, and a first-in-human trial has started (NCT05101109).

PBK/TOPK Is a Favorable Prognostic Biomarker Correlated with Antitumor Immunity in Colon Cancers

Immune checkpoint inhibitor therapy has proven efficacy in a subset of colon cancer patients featuring a deficient DNA mismatch repair system or a high microsatellite instability profile. However, there is high demand for more effective biomarkers to expand the colon cancer population responding to ICI therapy. PBK/TOPK, a serine/threonine kinase, plays a role in cell cycle regulation and mitotic progression. Here, we investigated the correlation between PBK/TOPK expression and tumor immunity and its prognostic value in colon cancer. Based on large-scale bioinformatics analysis, we discovered that elevated PBK/TOPK expression predicted a favorable outcome in patients with colon cancer and was positively associated with immune infiltration levels of CD8+ T cells, CD4+ T cells, natural killer cells, and M1 macrophages. In contrast, a negative correlation was found between PBK/TOPK expression and immune suppressor cells, including regulatory T cells and M2 macrophages. Furthermore, the expression of PBK/TOPK was correlated with the expression of T-cell cytotoxicity genes in colon cancer. Additionally, high PBK/TOPK expression was associated with mutations in DNA damage repair genes, and thus with increased tumor mutation and neoantigen burden. These findings suggest that PBK/TOPK may serve as a prognostic and predictive biomarker for immunotherapy in colon cancer.

892 ABL503 (TJ-L14B), PD-L1x4–1BB bispecific antibody induces superior anti-tumor activity by PD-L1-dependent 4–1BB activation with the increase of 4–1BB+CD8+ T cells in tumor microenvironment

Background

PD-(L)1 inhibitor has revolutionized cancer treatment, but there are unmet clinical needs for PD-(L)1 inhibitor-resistant/refractory patients. Activation of T cells in tumor microenvironment by 4-1BB agonist antibodies is one of the promising approaches to complement the current limitation of PD-(L)1 inhibitors. Although 4-1BB is a promising target for immunotherapy, clinical studies using 4-1BB agonist antibodies showed systemic immune cell activation resulting in dose-limiting hepatotoxicity. We generated ABL503 (TJ-L14B), a bispecific antibody that combines PD-(L)1 blockade and PD-L1-dependent 4-1BB agonistic activity by binding both PD-L1 and 4-1BB to limit unwanted toxicities while exerting a potent anti-tumor efficacy. Here, we reported the pre-clinical properties of ABL503 (TJ-L14B) in various studies.

Methods

The activity of ABL503 (TJ-L14B) was characterized and evaluated in 1) PD-1 and 4-1BB signaling reporter cells cocultured with various tumor cells and PBMCs, 2) hPD-L1/h4-1BB knock-in mice implanted with MC38 tumor expressing different level of hPD-L1, 3) patient-derived lung cancer organoids cocultured with autologous PBMCs, and 4) PBMCs from healthy donors to measure cytokine release.

Results

Functional evaluation of ABL503 (TJ-L14B) indicates the activation of 4-1BB signaling was solely dependent on engagement of hPD-L1 expressed on immune cells as well as on tumor cells, pointing to pivotal roles of PD-L1 on both immune cells and tumor cells for the activity of ABL503 (TJ-L14B). In vivo anti-tumor activity of ABL503 (TJ-L14B) across different hPD-L1 levels showed prominent anti-tumor effect with significantly increased number of CD8+ cells and 4-1BB+ cells in the tumor. This anti-tumor activity was correlated with the proliferation (Ki-67+) of CD8+ T cells in the tumor microenvironment. Ex vivo assays utilizing patient-derived lung cancer organoids revealed that ABL503 (TJ-L14B) exhibits superior tumor-killing activity than that by benchmark PD-L1 antibody, Atezolizumab. In addition, cytokine release assay demonstrated that ABL503 (TJ-L14B) did not induce non-specific pro-inflammatory cytokine release by human PBMCs.

Conclusions

Our data indicate that PD-L1 and 4-1BB dual targeting bispecific antibody, ABL503 (TJ-L14B), shows potent 4-1BB agonistic activity and anti-tumor effect in a PD-L1-dependent fashion concomitant with 4-1BB+/CD8+ T cell activation and proliferation to overcome limitations of PD-(L)1-targeted therapy while minimizing the risk of peripheral toxicity. The phase 1 clinical trial in the U.S. is currently ongoing in patients with locally advanced or metastatic solid tumors (NCT04762641).

Genome wide CRISPR screening reveals a role for sialylation in the tumorigenesis and chemoresistance of acute myeloid leukemia cells

Aberrant activation of cytokine and growth factor signal transduction pathways confers enhanced survival and proliferation properties to acute myeloid leukemia (AML) cells. However, the mechanisms underlying the deregulation of signaling pathways in leukemia cells are unclear. To identify genes capable of independently supporting cytokine-independent growth, we employed a genome-wide CRISPR/Cas9-mediated loss-of-function screen in GM-CSF-dependent human AML TF-1 cells. More than 182 genes (p < 0.01) were found to suppress the cytokine-independent growth of TF-1 cells. Among the top hits, genes encoding key factors involved in sialylation biosynthesis were identified; these included CMAS, SLC35A1, NANS, and GNE. Knockout of either CMAS or SLC35A1 enabled cytokine-independent proliferation and survival of AML cells. Furthermore, NSG (NOD/SCID/IL2Rγ^-/-) mice injected with CMAS or SLC35A1-knockout TF-1 cells exhibited a shorter survival than mice injected with wild-type cells. Mechanistically, abrogation of sialylation biosynthesis in TF-1 cells induced a strong activation of ERK signaling, which sensitized cells to MEK inhibitors but conferred resistance to JAK inhibitors. Further, the surface level of α2,3-linked sialic acids was negatively correlated with the sensitivity of AML cell lines to MEK/ERK inhibitors. We also found that sialylation modulated the expression and stability of the CSF2 receptor. Together, these results demonstrate a novel role of sialylation in regulating oncogenic transformation and drug resistance development in leukemia. We propose that altered sialylation could serve as a biomarker for targeted anti-leukemic therapy.

Harnessing NK cells for cancer immunotherapy: immune checkpoint receptors and chimeric antigen receptors

Natural killer (NK) cells, key antitumor effectors of the innate immune system, are endowed with the unique ability to spontaneously eliminate cells undergoing a neoplastic transformation. Given their broad reactivity against diverse types of cancer and close association with cancer prognosis, NK cells have gained considerable attention as a promising therapeutic target for cancer immunotherapy. NK cell-based therapies have demonstrated favorable clinical efficacies in several hematological malignancies but limited success in solid tumors, thus highlighting the need to develop new therapeutic strategies to restore and optimize antitumor activity while preventing tumor immune escape. The current therapeutic modalities yielding encouraging results in clinical trials include the blockade of immune checkpoint receptors to overcome the immune-evasion mechanism used by tumors and the incorporation of tumor-directed chimeric antigen receptors to enhance NK cell antitumor specificity and activity. These observations, together with recent advances in the understanding of NK cell activation within the tumor microenvironment, will facilitate the optimal design of NK cell-based therapy against a broad range of cancers and, more desirably, refractory cancers.

GSK3 Restrains Germinal Center B Cells to Form Plasma Cells

B cells in the germinal center (GC) are programmed to form plasma cells (PCs) or memory B cells according to signals received by receptors that are translated to carry out appropriate activities of transcription factors. However, the precise mechanism underlying this process to complete the GC reaction is unclear. In this study, we show that both genetic ablation and pharmacological inhibition of glycogen synthase kinase 3 (GSK3) in GC B cells of mice facilitate the cell fate decision toward PC formation, accompanied by acquisition of dark zone B cell properties. Mechanistically, under stimulation with CD40L and IL-21, GSK3 inactivation synergistically induced the transcription factors Foxo1 and c-Myc, leading to increased levels of key transcription factors required for PC differentiation, including IRF4. This GSK3-mediated alteration of transcriptional factors in turn facilitated the dark zone transition and consequent PC fate commitment. Our study thus reveals the upstream master regulator responsible for interpreting external cues in GC B cells to form PCs mediated by key transcription factors.

The deubiquitinase CYLD controls protective immunity against helminth infection by regulation of Treg cell plasticity

BACKGROUND

Type 2 immunity can be modulated by regulatory T (Treg) cell activity. It has been suggested that the deubiquitinase cylindromatosis (CYLD) plays a role in the development or function of Treg cells, implying that it could be important for normal protective immunity, where type 2 responses are prevalent.

OBJECTIVE

We sought to investigate the role of CYLD in Treg cell function and T_H2 cell immune responses under steady-state conditions and during helminth infection.

METHODS

Foxp3-restricted CYLD conditional knockout (KO) mice were examined in mouse models of allergen-induced airway inflammation and Nippostrongylus brasiliensis infection. We performed multiplex magnetic bead assays, flow cytometry, and quantitative PCR to understand how a lack of CYLD affected cytokine production, homing, and suppression in Treg cells. Target genes regulated by CYLD were identified and validated by microarray analysis, coimmunoprecipitation, short hairpin RNA knockdown, and transfection assays.

RESULTS

Treg cell-specific CYLD KO mice showed severe spontaneous pulmonary inflammation with increased migration of Treg cells into the lung. CYLD-deficient Treg cells furthermore produced high levels of IL-4 and failed to suppress allergen-induced lung inflammation. Supporting this, the conditional KO mice displayed enhanced protection against N brasiliensis infection by contributing to type 2 immunity. Treg cell conversion into IL-4-producing cells was due to augmented mitogen-activated protein kinase and nuclear factor κB signaling. Moreover, Scinderin, a member of the actin-binding gelsolin family, was highly upregulated in CYLD-deficient Treg cells, and controlled IL-4 production through forming complexes with mitogen-activated protein kinase kinase/extracellular receptor kinase. Correspondingly, both excessive IL-4 production in vivo and the protective role of CYLD-deficient Treg cells against N brasiliensis were reversed by Scinderin ablation.

CONCLUSIONS

Our findings indicate that CYLD controls type 2 immune responses by regulating Treg cell conversion into T_H2 cell-like effector cells, which potentiates parasite resistance.

Has-miR-17 increases the malignancy of gastric lymphoma by HSP60/TNFR2 pathway

The purpose of this study was to investigate the expression and mechanism of miR-17 in gastric lym-phoma. miR-17mimics, miR-17 inhibitors and negative controls were transfected into human gastric lymphoma cell line cyp6d. The proliferation, invasion and apoptosis of cyp6d cells were detected by CCK-8, Transwell and TUNEL methods, respectively. The expression and clinicopathological features of miR-17 in gastric lymphoma were analyzed by real-time quantitative PCR. The target gene of miR-17 was predicted by targetscan 7.2, and the expression of miR-17 related protein was detected by Western blot. The results showed that the expression of miR-17 in gastric lymphoma was significantly higher than that in normal tissues (P < 0.05), which was closely related to lymph node metastasis, tumor size and distant metastasis (P < 0.05). The high expression of miR-17 significantly promoted the proliferation and invasion of cyp6d cells and inhibited apoptosis (P < 0.05). The high expression of miR-17 can regu¬late the expression of HSP60 and TNFR2. It has been found that miR-17 can promote the development of gastric lymphoma by regulating HSP60/TNFR2 pathway, which is a potential molecular target for the diagnosis and treatment of gastric lymphoma.

CD226hiCD8+ T Cells Are a Prerequisite for Anti-TIGIT Immunotherapy

Clinical trials are evaluating the efficacy of anti-TIGIT for use as single-agent therapy or in combination with programmed death 1 (PD-1)/programmed death-ligand 1 blockade. How and whether a TIGIT blockade will synergize with immunotherapies is not clear. Here, we show that CD226^loCD8⁺ T cells accumulate at the tumor site and have an exhausted phenotype with impaired functionality. In contrast, CD226^hiCD8⁺ tumor-infiltrating T cells possess greater self-renewal capacity and responsiveness. Anti-TIGIT treatment selectively affects CD226^hiCD8⁺ T cells by promoting CD226 phosphorylation at tyrosine 322. CD226 agonist antibody-mediated activation of CD226 augments the effect of TIGIT blockade on CD8⁺ T-cell responses. Finally, mFOLFIRINOX treatment, which increases CD226^hiCD8⁺ T cells in patients with pancreatic ductal adenocarcinoma, potentiates the effects of TIGIT or PD-1 blockade. Our results implicate CD226 as a predictive biomarker for cancer immunotherapy and suggest that increasing numbers of CD226^hiCD8⁺ T cells may improve responses to anti-TIGIT therapy.

Extracellular pH modulating injectable gel for enhancing immune checkpoint inhibitor therapy

Clinical data from diverse cancer types shows that the increased T cell infiltration in tumors correlates with improved patient prognosis. Acidic extracellular pH is a major attribute of the tumor microenvironment (TME) that promotes immune evasion and tumor progression. Therefore, antagonizing tumor acidity can be a powerful approach in cancer immunotherapy. Here, Pluronic F-127 is used as a NaHCO₃ releasing carrier to focally alleviate extracellular tumor acidity. In a mouse tumor model, intratumoral treatment with pH modulating injectable gel (pH_e-MIG) generates immune-favorable TME, as evidenced by the decrease of immune-suppressive cells and increase of tumor infiltrating CD8+T cells. The combination of pH_e-MIG with immune checkpoint inhibitors, anti-PD-1 and anti-TIGIT antibodies, increases intratumoral T cell function, which leads to tumor clearance. Mechanistically, extracellular acidity was shown to upregulate co-inhibitory immune checkpoint receptors and inhibit mTOR signaling pathways in memory CD8+T cells, which impaired effector functions. Furthermore, an acidic pH environment increased the expression and engagement of TIGIT and its ligand CD155, which suggested that the extracellular pH can regulate the suppressive function of TIGIT pathway. Collectively, these findings suggest that pH_e-MIG holds potential as a new TME modulator for effective immune checkpoint inhibitor therapies.

TSC1 regulates the balance between effector and regulatory T cells

Mammalian target of rapamycin (mTOR) plays a crucial role in the control of T cell fate determination; however, the precise regulatory mechanism of the mTOR pathway is not fully understood. We found that T cell-specific deletion of the gene encoding tuberous sclerosis 1 (TSC1), an upstream negative regulator of mTOR, resulted in augmented Th1 and Th17 differentiation and led to severe intestinal inflammation in a colitis model. Conditional Tsc1 deletion in Tregs impaired their suppressive activity and expression of the Treg marker Foxp3 and resulted in increased IL-17 production under inflammatory conditions. A fate-mapping study revealed that Tsc1-null Tregs that lost Foxp3 expression gained a stronger effector-like phenotype compared with Tsc1-/- Foxp3+ Tregs. Elevated IL-17 production in Tsc1-/- Treg cells was reversed by in vivo knockdown of the mTOR target S6K1. Moreover, IL-17 production was enhanced by Treg-specific double deletion of Tsc1 and Foxo3a. Collectively, these studies suggest that TSC1 acts as an important checkpoint for maintaining immune homeostasis by regulating cell fate determination.

A novel inhibitor of apoptosis protein (IAP)-interacting protein, Vestigial-like (Vgl)-4, counteracts apoptosis-inhibitory function of IAPs by nuclear sequestration

The inhibitors of apoptosis proteins (IAP), which include cIAP1, cIAP2 and XIAP, suppress apoptosis through the inhibition of caspases, and the activity of IAPs is regulated by a variety of IAP-binding proteins. Herein, we report the identification of a Vestigial-like 4 (Vgl-4), which functions as a transcription cofactor in cardiac myocytes, as a new IAP binding protein. Vgl-4 is expressed predominantly in the nucleus and its overexpression triggers a relocalization of IAPs from the cytoplasm to the nucleus. cIAP1/2-interacting protein TRAF2 (TNF receptor-associated factor 2) prevented the Vgl-4-driven nuclear localization of cIAP2. Accordingly, the forced relocation of IAPs to the nucleus by Vgl-4 significantly reduced their ability to prevent Bax- and TNFα-induced apoptosis, which can be recovered by co-expression with TRAF2. Our results suggest that Vgl-4 may play a role in the apoptotic pathways by regulating translocation of IAPs between different cell compartments.

Cell cycle-dependent expression of cIAP2 at G2/M phase contributes to survival during mitotic cell cycle arrest

cIAP2 (cellular inhibitor of apoptosis protein 2) is induced by NF-kappaB (nuclear factor kappaB) when cells need to respond quickly to different apoptotic stimuli. A recent study using cDNA microarray technology has suggested that cIAP2 transcription is regulated in a cell cycle-dependent manner, although the mechanism for such regulation is unknown. In this study, we confirmed the cell cycle-dependent regulation of cIAP2 expression at both the mRNA and protein levels. Additionally, we found that a bipartite CDE (cell cycle-dependent element)/CHR (cell cycle gene homology region) element in the cIAP2 promoter mediates cIAP2 gene activation in G2/M phase. Cell cycle-dependent G2/M-phase-specific cIAP2 expression is enhanced by NF-kappaB activation, and selective down-regulation of cIAP2 causes cells blocked in mitosis with nocodazole to become susceptible to apoptosis, indicating that the G2/M-phase-specific expression of cIAP2 contributes to the survival of mitotically arrested cells. Our studies describing the NF-kappaB-independent G2/M-phase-specific expression of cIAP2 will help in further understanding the molecular basis of cIAP2 over-expression in a variety of human cancers.

Development of anticancer gene vaccine interact with human papillomavirus oncoprotein inhibition

Adeno-associated virus (AAV) Rep 78 protein is known to inhibit the promoter site of several oncogenes and viral genes, including the human papillomavirus (HPV) type 16 E6 transforming genes. The biochemical studies of Rep 78 have been reported, but the effects of Rep 78 gene-mediated inhibition of HPV 16 E6 promoter activity on the various human cervical carcinoma cells have not been characterized. pEGFP-N1 vector, cloned by AAV-mediated Rep 78, is transfected into cervical carcinoma cells. Transfection efficiency of Rep 78 was approximately 30-60% different. Messenger RNA (mRNA) and protein expression of Rep 78 gene was significantly higher on day 1 of the transfection of Rep 78 DNA in CaSki cells, and DNA level of HPV 16 E6 was decreased on day 1 of the transfection. The growth of CaSki cervical cancer cells was only 10-15% inhibited by Rep 78, and the other cervical cells, HeLa, HeLaS3, HT3, and QGU, were unaffected by Rep 78 transfection. In spite of the high efficiency of Rep 78 gene transformation and expression rate, we could not show the significant growth inhibition in various cervical cancer cell lines. Taken together, long-term expression of Rep 78 strategy might be needed for cervical carcinoma gene therapy using AAV vector.

Proteome Analysis Associated with Cadmium Adaptation in U937 Cells

Cadmium is a well known environmental toxicant and carcinogen. To identify proteins involved in cellular adaptive responses to cadmium, we established cadmium-adapted U937 cells that exhibit resistance to cadmium-induced apoptosis, and we performed comparative proteome analysis of these cells with parental cells that were either untreated or treated with cadmium. Newly identified proteins that were changed in expression level in both adapted cells and cadmium-treated parental cells included proteins implicated in cell proliferation and malignant transformation. Most interesting, a calcium-binding protein calbindin-D(28k) was increased only in the adapted cells but not in cadmium-exposed parental cells. The level of calbindin-D(28k) increased by the degree of cadmium adaptation and was stably maintained without selective pressure of cadmium. Cadmium-adapted U937 cells were resistant to the toxic effects of cytosolic calcium rise by cadmium treatment and by depletion of intracellular calcium stores, suggesting that enhanced calcium buffering by up-regulated calbindin-D(28k) may be responsible for acquiring resistance to cadmium-induced apoptosis. We demonstrated that overexpression of calbindin-D(28k) in MN9D neuronal cells resulted in reduced cadmium-induced apoptosis. Our study documents for the first time that cells respond to long term cadmium exposure by increasing calbindin-D(28k) expression, thereby attenuating cadmium-induced apoptosis.

Der p 2 isoallergens have different allergenicity, and quantification with 2-site ELISA using monoclonal antibodies is influenced by the isoallergens

BACKGROUND

Der p 2 isoallergens have been reported and the possibility of different allergenicity has also been suggested. In addition, the quantification with 2-site ELISA may be affected by the isoallergens.

OBJECTIVES

Two different recombinant Der p 2 (rDer p 2) isoallergens were compared in terms of human IgE responses and the reliability of quantification of them with two-site ELISA kits which use monoclonal antibodies (mAbs) as capture and detection of Der p 2.

METHODS

Seven different Der p 2 cDNA from the cultured Dermatophagoides pteronyssinus (DP) were cloned and polymorphism in nine amino acid residues was found. Two different recombinant isoallergens (rDer p 2A and rDer p 2B) were expressed and compared to their human IgE immune responses by ELISA and the ELISA inhibition test with 23 sera of DP-allergic patients. The reliability of quantification of two different available 2-site ELISA kits, which used mAbs for capture and detection of Der p 2, was evaluated.

RESULTS

The ELISA optical density of rDer p 2B-specific IgE (sIgE) was higher than that of rDer p 2A (P < 0.001). The ELISA inhibition curve of rDer p 2B sIgE in pool I sera (n = 5; high sIgE both to rDer p 2A and rDer p 2B) did not show any differences in the 50% inhibition concentration and maximum inhibitory percentage of rDer p 2A and rDer p 2B sIgE. However, with pool II sera (n = 5; markedly higher sIgE to rDer p 2B than rDer p 2A), the 50% inhibitory concentrations (10 microg/mL vs. 40 ng/mL) and maximum inhibitory percentage (61% vs. 99%) of rDer p 2B sIgE with the two recombinant isoallergens were quite different. rDer p 2B could be quantified with two different 2-site ELISA kits, but rDer p 2A was detected by only one kit.

CONCLUSION

We conclude that isoallergens of Der p 2 may have different IgE immune responses. Quantification of Der p 2 with 2-site ELISA kits that adopted mAbs, might be affected by the prevalent form of the isoallergens in reservoir dust.

Monoclonal antibodies to recombinant Der f 2 and development of a two-site ELISA sensitive to major Der f 2 isoallergen in Korea

BACKGROUND

Der f 2 is a major sensitizing allergen in patients allergic to house dust mites worldwide. Isoforms of Der f 2 have been reported and are known to have different antigenicities. The aim of this study was to facilitate antigenic analysis and to develop an improved method for the detection of Der f 2 isoallergen, which is prevalent in Korea.

METHODS

A two-site ELISA was developed with monoclonal antibodies (mAbs) which were produced against recombinant Der f 2 (rDer f 2) and applied to assess Der f 2 in bedding samples.

RESULTS

A major isoform of Der f 2, found in Korea, was found to have amino acid variations especially at position 100 from lysine to glutamic acid, which is known to reduce significantly the binding affinity of mAbs when used to assess group 2 allergens. The detection limit of the developed two-site ELISA was determined to be about 8 ng/ml with rDer f 2 and 1 microg/ml with Derntatophagoides farinae crude extract. The average amount of Der f 2 in dust obtained from bedding samples from 89 homes in Seoul was estimated to be 25.61+/-10.70 microg/g dust.

CONCLUSIONS

Assays using mAbs for rDer f 2 could be useful for the assessment of environmental allergen exposure and mAbs could be used to further characterize the isoallergens of Der f 2.

Alterations of myoepithelial cells in the rat mammary gland during pregnancy, lactation and involution, and after estradiol treatment

Hormone-induced alterations of myoepithelial cells in the mammary gland have not been fully investigated. The aim of the present study was to examine whether myoepithelial cells are altered in response to hormonal conditions. The immunohistochemical findings of smooth muscle actin for myoepithelial cells were studied during pregnancy, lactation and involution, and after estradiol dipropionate (ED) treatment (50, 500, 1000 microg/kg per week for 1-4 weeks) using a total of 71 Wistar female rats. Myoepithelial cells showed a stratified appearance around ducts during pregnancy, extended cytoplasmic processes with wider distance during lactation, and vacuolated cytoplasm after weaning. ED treatment (50-1000 microg/kg per week) for 1 week increased myoepithelial cells to a variable degree, achieving a level similar to that in pregnancy, but ED treatment for 4 weeks reduced them as the dose elevated. The present study showed that the myoepithelial cells became hyperplastic or hypertrophic by low-dose ED treatment within the physiological range, while weaning pups, and excess high-dose ED treatment beyond the physiological range or prolonged ED treatment induced reduction of the myoepithelial cells. Results indicate that myoepithelial cells themselves are also altered by hormonal conditions coordinating the mammary gland development.

Interferon-gamma alone triggers the production of nitric oxide from serum-starved BNL CL.2, murine embryonic liver cells

A previous study has demonstrated that both interferon-gamma (IFN-gamma) and lipopolysaccharide (LPS) were needed to induce the production of nitric oxide (NO) in BNL CL.2 cells, murine embryonic liver cells. We here demonstrate that when BNL CL.2 cells were cultured with serum-free medium, they were induced to produce NO by the stimulation of IFN-gamma alone. BNL CL.2 cells were cultured with serum-free or serum-containing medium for 1-3 days and then stimulated to synthesize NO by IFN-gamma. Surprisingly, only serum-starved cells showed significant amount of nitrite accumulation and iNOS protein expression in response to IFN-gamma in dose- and time-dependent manners, but serum-supplied cells did not. When the cells were stimulated with IFN-gamma, tumor necrosis factor-alpha (TNF-alpha), or LPS in combinations, only the combination of IFN-gamma and LPS produced more NO than that produced by IFN-gamma alone. The production of NO by the cells stimulated with IFN-gamma or IFN-gamma plus LPS was blocked by the addition of N(G)-monomethyl-L-arginine (N(G)MMA), a NO synthesis inhibitor. To address the intracellular signal pathway responsible for the production of NO by the cells stimulated with IFN-gamma aloneor IFN-gamma plus LPS, we examined the effects of several protein kinase inhibitors on the production of NO from the cells. The production of NO was significantly inhibited by protein tyrosine kinase (PTK) inhibitors, genistein and herbimycin A, but not by protein kinase A or C inhibitors. These results suggest that the deprivation of serum from BNL CL.2 cell culture medium might prime the cells to induce NO synthesis when the cells are triggered by IFN-gamma and the involvement of PTK signal transduction pathway in the expression of inducible NO synthase gene in murine hepatoma cells.