Cloning, expression and characterization of recombinant human Fc receptor like 1, 2 and 4 molecules

The Fc receptor like [FCRL] molecules belong to the immunoglobulin [Ig] superfamily with potentially immunoregulatory function. Among the FCRL family FCRL2 and 4 are predominantly expressed on memory B cells and FCRL1 is a pan- B cell marker. To date, no ligand has been identified for the human FCRL1, 2 and 4 molecules. Cloning, expression, purification and structural analysis of the extracellular domain of human FCRL1, 2 and 4 proteins. In this study, the extracellular part of human FCRL1, 2 and 4 were subcloned into prokaryotic expression vectors pET-28b [+] and transformed into BL21-DE3 E.coli strain. Protein expression was optimized by fine adjustments such as induction time, incubation temperature and expression hosts. Recombinant FCRL proteins were purified by metal affinity chromatography using Ni-NTA resin. Purified FCRL proteins were further characterized by SDS-PAGE and immunoblotting using His-tag and FCRL specific polyclonal antibodies. Our results demonstrated that FCRL1, 2 and 4 were successfully expressed in pET-28b [+] vector. Optimization of the expression procedure showed that IPTG induction at OD600 = 0.9 and overnight incubation at 37[degree]C resulted in the highest expression levels of FCRL proteins ranging from approximately 15% [FCRL1] to 25% [FCRL2 and 4] of the total bacterial lysate proteins. These purified recombinant proteins are potentially a valuable tool for investigating the immunoregulatory function of FCRL molecules and the production of specific mAbs for immunotherapeutic interventions.

Expression, purification and characterization of three overlapping immunodominant recombinant fragments from Bordetella pertussis filamentous hemagglutinin

Filamentous hemagglutinin [FHA] is one of the most important immunoprotective antigens of Bordetella pertussis [B. pertussis] and a major component of the acellular pertussis vaccine. In the present study, three overlapping recombinant fragments from the immunodominant region of FHA were produced and their immunogenicity was investigated. Three overlapping coding sequences of FHA antigen were amplified from B. pertussis genomic DNA by PCR. Amplified fragments were expressed in Escherichia coli [E. coli] BL21[DE3] strain and purified through His-tag using Nickel-based chromatography. Purified fragments were characterized by SDS-PAGE and Western blotting techniques. In vitro peripheral blood mononuclear cells [PBMC] proliferation and IFN- gamma production were assessed in a limited number of healthy adults vaccinated with a commercial acellular pertussis vaccine in response to all purified FHA fragments by H3-Thymidine incorporation and ELISA, respectively. Recombinant FHA segments were successfully cloned and produced at high levels in E. coli BL21[DE3]. SDS-PAGE and Western blot analyses confirmed their purity and reactivity. All three recombinant fragments together with a commercial native FHA were able to induce in vitro PBMC proliferation and IFN- gamma production. Our preliminary results suggest that these overlapping recombinant FHA fragments are immunogenic and may prove to be immunoprotective

Production and characterization of mouse monoclonal antibodies recognizing human Pan-IgG specific conformational or linear epitopes

Pan-IgG specific monoclonal antibodies [MAbs] are essential tools for assessment of humoral immunity, immune deficiency and gammopathy. In this study, four hybridoma clones producing MAbs with different specificities for human IgG isotypes were established. Splenocytes from Balb/c mice immunized with Fc fractions of human IgG were fused with SP2/0 myeloma cells. Hybridoma cells were selected in HAT selective medium and cloned by limiting dilution assay. Antibody-secreting cells were screened by enzyme-linked immunosorbent assay [ELISA] and the specificity of secreted MAbs was further analyzed using a panel of purified myeloma IgG proteins by ELISA and immunoblotting. Cross-reactivity to immunoglobulins [Igs] of other species was studied by indirect ELISA using serum samples collected from 9 animals. Immunoblotting studies revealed recognition of either linear or conformational epitopes by these MAbs. The most abundant cross-reactivity [100%] was observed with monkey Igs, while no cross-reactivity was detected with rabbit, guinea pig, sheep, goat, cat and hen sera. Two of the MAbs crossreacted with either dog or horse sera. The affinity constant of two MAbs was measured by ELISA and found to be 0.74×10[8] M[-1] and 0.96×10[7] M[-1]. Our results indicate that these pan-IgG specific MAbs recognize restricted linear or conformational epitopes located on all human IgG subclasses with no cross-reactivity to IgG from most species studied. These MAbs are potentially useful tools for quantification of total or antigen-specific IgG levels

Comparative expression profile of orphan receptor tyrosine kinase ROR1 in Iranian patients with lymphoid and myeloid leukemias

It has recently been shown that ROR1, a member of the receptor tyrosine kinase family, is overexpressed in leukemic B cells of Chronic Lymphocytic Leukemia [CLL] and a subset of Acute Lymphoblastic Leukemia [ALL]. In this comparative study the expression profile of ROR1 mRNA was investigated in Iranian patients with CLL and Acute Myelogenous Leukemia [AML] and the results were compared with those previously reported in our Iranian ALL patients. RT-PCR was performed on bone marrow and/or peripheral blood samples of 84 CLL and 12 AML patients. CLL samples were classified into immunoglobulin heavy chain variable region [IGHV] gene mutated [n=55] and unmutated [n=29] and also indolent [n=42] and progressive [n=39] subtypes. ROR1 expression was identified in 94% of our CLL patients, but none of the AML patients expressed ROR1. No significant differences were observed between different CLL subtypes for ROR1 expression. Taken together the present data and our previous results on ROR1 expression in ALL, our findings propose ROR1 as a tumor-associated antigen overexpressed in a large proportion of lymphoid [CLL and ALL], but not myeloid [AML] leukemias. Expression of ROR1 seems to be associated to lineage and differentiation stages of leukemic cells with a potential implication for immunotherapy

Lymphocyte cytotoxicity of oxLDL in patients with atherosclerosis

Atherosclerosis, a chronic inflammatory disease of the vessel wall is characterized by local and systemic immune responses to a variety of antigens. Oxidized low-density lipoprotein [oxLDL] is considered as an important determining factor in the pathogenesis of atherosclerosis. The purpose of this study was to investigate the degree of peripheral blood mononuclear cells [PBMC] vulnerability to in vitro oxLDL-induced cytotoxicity from atherosclerotic patients in comparison to healthy individuals. Thirty patients with atherosclerotic lesions, confirmed by angiography, and 30 matched healthy individuals were investigated. PBMC was prepared from individuals' blood samples which were further stimulated with low dose [1 micro g/mL] and high dose [50 micro g/mL] of extensively oxidized LDL. MTT assay was utilized to measure cell viability and proliferation. Stimulation index [SI] was calculated as mean ratio of optical density [OD] of the stimulated cells divided by OD of untreated cells. Low dose oxLDL treatment caused no significant proliferative or cytotoxic effect in the control group; however, similar treatment caused significant cytotoxic effect in the patient group compared to the controls [p=0.026]. High dose oxLDL treatment induced more significant cytotoxicity in the patient compared to the control group [p=0.006]. Comparison of the SI between the two groups of patients and controls showed significantly lower index by either the low [p=0.03] or the high dose [p<0.001] oxLDL in the patients compared to the controls. PBMC from patients with atherosclerosis showed increased susceptibility to oxLDL-induced cytotoxicity. Our results imply that prolonged exposure to elevated levels of circulating oxLDL could weaken the cellular defense mechanisms by progressive depletion of the pool of antiapoptotic proteins, rendering the cells more vulnerable to oxLDL-induced cell death

Development of a sensitive enzyme-linked immunosorbent assay for detection of hepatitis B surface antigen using novel monoclonal antibodies

Hepatitis B virus [HBV] infection is the 10th leading cause of death worldwide. The most important diagnostic and screening marker for HBV infection is Hepatitis B surface antigen [HBsAg], and the most widely used HBsAg screening test is Enzyme-linked Immunosorbent Assay [ELISA]. In this study, an ELISA assay has been developed for detection of HBsAg using two novel monoclonal antibodies [mAb] as capture layer and a polyclonal biotinylated Ab as detector phase. We evaluated the sensitivity, specificity, detection limit, seroconversion time, positive and negative predictive values and reproducibility of our assay with standard panels and different serum samples. The results were compared with a well established commercial kit. Both assays showed similar detection limit values of 0.5 to 0.7 ng/ml and the same seroconversion periods of 42 and 65 days for [ad] and [ay] serotypes of HBsAg, respectively. Sensitivity and specificity of the assay were 98.98% and 99.6%, respectively. The positive and negative predictive values of our assay were also calculated as 99.49% and 99.2%, respectively. Analysis of reproducibility of the present assay demonstrated 3.96% and 5.85% intra-and inter-assay coefficient of variations, respectively, which were less than those obtained by the commercial kit. There was a highly significant correlation between our designed assay and the commercial ELISA kit [p < 0.0001, r = 0.957]. Altogether, our results indicate that the designed assay is comparable to the commercial kit in terms of sensitivity, specificity, positive and negative predictive values and reproducibility and could be employed for diagnosis of HBV infection in blood samples

Immunophenotypic subtyping of leukemic cells from Iranian patients with acute lymphoblastic leukaemia: association to disease outcome

Immunophenotypic characterization of the leukemic cells has been widely used as a tool for diagnosis, classification, stratification and prognosis of leukaemia. To investigate the immunophenotypic subtype profiles of Iranian patients with acute lymphoblastic leukemia [ALL] and its association to disease outcome. In this study, a total of 60 Iranian patients with ALL were immunophenotyped by flow cytometry using a panel of monoclonal antibodies specific for CD2, CD3, CD5, CD10, CD13, CD14, CD19, CD20, CD33, CD34, CD45, HLA-DR and TdT molecules. The samples were initially categorized into T-ALL [n=9], B-ALL [n=50] and mixed lineage [n=1] based on the expression patterns of CD3 and CD19 molecules. B-ALL patients could further be classified into four subtypes, including Pro-B [n=7, 11.7%], Pre-B I [n=28, 46.7%], Pre-B II [n=13, 21.7%] and immature/mature B cells [n=2, 3.3%] on the basis of expression of CD10, CD19, CD20, HLA-DR and TdT. Clinical manifestations and laboratory findings of the patients did not reveal association with immunophenotypic sub-types of ALL, with the exception of mediastinal mass and WBC count at the time of diagnosis which were found to be significantly higher in patients with T-ALL compared with B-ALL [p=0.001 and 0.014], respectively. Our results indicate that overall the immunophenotypic profile of Iranian ALL patients is similar to previous reports and it might be used for monitoring of minimal residual disease and prognosis

Production and characterization of murine monoclonal antibodies recognizing conformational and linear epitopes localized on human IgA2 molecules

There are two subclasses of human IgA [IgA1 and IgA2] that differ in antigenic properties and in chemical composition. The constant domains of alpha1 and alpha2 heavy chains have >95% sequence homology though major structural differences exist in the hinge region. Quantitation of IgA subclass levels depends on the availability of monoclonal antibodies [MAbs] specific for conserved conformational or linear epitopes restricted to each subclass. To produce, select and characterize monoclonal antibodies specific for human IgA2. Splenocytes from BALB/C mice immunized with a human IgA2 myeloma protein were fused with SP2/0 myeloma cells. Fused cells were grown in hypoxanthine, aminopterine and thymidine [HAT] selective medium and cloned by limiting dilution assay. Antibody [Ab] secreting cells were screened by enzyme-linked immunosorbent assay [ELISA] and the specificity of secreted MAbs was further analyzed, using a panel of purified myeloma proteins and some animal sera by ELISA and immunoblotting. The affinity constant [K[aff]] was also determined by ELISA. Four murine hybridoma clones designated 2F20G5, 2F20B5, 3F20E3 and 6F20H11 were obtained that secreted MAbs specific for the human IgA2. 2F20G5 and 6F20H11 MAbs react with linear epitope[s] while 2F20B5 and 3F20E3 react with conformational epitope[s] located to human IgA2 subclass. 2F20G5 MAb displays a weak cross-reactivity with monkey and rabbit sera and a strong cross-reactivity with cat and dog sera while the other three MAbs showed no cross-reactivity with the animal sera tested. These MAbs, especially 6F20H11 with high affinity constant [6.03 x10[9] M[-1]] are useful tools for quantitation of human IgA2 subclass levels in various diseases. Cross-reactivity of 2F20G5 MAb with some animal sera suggests phylogenic conservation of the epitope recognized by this MAb

Down regulation of IL-12 production in healthy non-responder neonates to recombinant hepatitis B vaccine

A proportion of healthy neonates and adults fail to develop a protective antibody response to recombinant hepatitis B [HB] vaccine. Unresponsiveness to vaccination could be attributed to defect in a number of immunological regulatory mechanisms. In this study, IL-12 was quantitated in culture supernatant following in vitro stimulation of peripheral blood mononuclear cells isolated from a group of responder and non-responder neonates. Our results indicate significantly decreased production of HBsAg-induced IL-12 in non-responder subjects compared to responders [P<0.01]. Since IL-12 is produced mainly by antigen presenting cells [APC] and is considered to be crucial for initiation and polarization of CD4+ T-cell function, therefore, our findings could be interpreted to imply APC dysfunction in non-responder vaccines