Makonnen Abebe

Isolation and characterization of a cDNA clone encoding one IgE-binding fragment of Penicillium brevicompactum.

Background:The abundance of allergenic Penicillium species has been associated with an increased incidence of childhood asthma and pulmonary bleeding. Penicillium brevicompactum has been identified as the most prevalent indoorspecies of this genus. However, detailed studies on the allergens of the ubiquitous Penicillium species are still lacking. For the characterization of allergens of prevalent Penicillium species, molecular cloning of the allergen genes of P. brevicompactum was performed in the present study. Methods:A phage cDNA library of P. brevicompactum was constructed in Uni-ZAP® XR vector using mRNA isolated from the organism. The cDNA library of P.brevicompactum was screened using pooled atopic sera. Results: Screening of P. brevicompactum cDNA library resulted in one positive clone encoding an estimated molecular weight of 11 kDa polypeptide, rich in acidic residues (>20%), with a pI of 3.87. This clone was designated as Pen b 26 and found to be reactive only against the atopic sera obtained from individuals sensitive to P. brevicompactum. The amino acid sequence analysis of Pen b 26 revealed that it had strong homology to the 60S acidic ribosomal protein P1 family from different eukaryotic sources, predominantly fungal aero-allergens. Other features of Pen b 26 including having high alpha-helical content (>50%), alanine-rich residues (>20%), and a well-conserved C-terminal epitope region fits well into the common properties of 60S acidic ribosomal proteins. Conclusions:The results obtained suggest that the allergenic clone, Pen b 26 is a 60S acidic ribosomal protein P1 of P. brevicompactum and shows strong similarity to other P1 family proteins.

Expression and characterization of Pen b 26 allergen of Penicillium brevicompactum in Escherichia coli

Pen b 26 is one of the allergens produced by Penicillium brevicompactum which is one of the most prevalent in door airborne fungi and a major source of respiratory problems, including asthma. Pen b 26 wa scloned and expressed as an N-terminal as well as a C-terminal His6 tagged fusion protein in Escherichia coli. This allergen was purified by immobilized Ni2+-affinity chromatography. The purified Pen b 26 was characterized by immunological, biochemical and biophysical methods. C-His6 tagged Pen b 26 produced several fold greater yield than N-His6 tagged Pen b 26. The affinity of C-His6 tagged Pen b 26 for the specific antibody was also 2.75 times higher than N-His6 tagged Pen b 26

Inhibition of Cell Division in Mouse B-Cell Hybridomas: An Overlooked Property of 2-Mercaptoethanol and Its Impact on in vitro Antibody Production

Thiol 2-mercaptoethanol (2-ME) has been reported to enhance growth in lymphocytes by various investigators. Some have used 50 μM for growing hybridomas in vitro. Concentrations of 50 and 5 μM in 5% FBS supplemented D-MEM were tested to determine their effects on the growth of 5 monoclonal antibody secreting mouse B cell hybridomas and the myeloma Sp2/O-Ag14. Viability after 24 and 48 h exposure was determined by Trypan blue exclusion. Analysis by one-way ANOVA confirmed that 50 μM 2-ME has a significant negative impact (p<0.05) on hybridoma as well as on myeloma growth, whereas no significant difference (p>0.05) between the control and the 5 μM treatment group was observed after 48 h. Also, no significant difference (p>0.05) in the mortality rates between the control and the treatment groups was found. When combined with the observed protracted doubling time in the 50 μM treatment group, these results indicate that the impact of 2-ME is due to inhibition of cell division. The degree of inhibition was observed to vary between the different hybridomas as well as the myeloma. Although the impact of 2-ME on mitosis has been demonstrated in organisms such as the ciliated protozoan Tetrahymena pyriformis, the yeast Saccharomycess cerevisiae, and the egg of the echinoid the sand dollar Dendraster excentricus, this work demonstrates for the first time that 2-ME impedes the growth of mouse B cell hybridomas. We conclude that adding 2-ME to mouse B cell hybridoma growth media may not be beneficial.

The application of IgM in an xMAP suspension assay using recombinant Alt a1 as a model target protein

The potential of Immunoglobulin M (IgM) in an Multi Analyte Profiling (xMAP) multiplex suspension assay was determined using Alt a1, a major allergen of Alternaria alternata, as the model target protein. LumAvidin (LAM) and carboxylated (CAM) microspheres, from LUMINEX™ Corporation, were compared. The reproducible standard curves for concentrations between 1 pg/mL and 10 ng/mL and 3 pg/mL and 300 ng/mL of the allergen were generated by the LAM assay, allowing for the quantitation of an unknown test sample. The success of the LAM assay is dependent on avidin molecules, initially bound on the microsphere, along with the use of a phycoerythrin-coupled secondary IgM. The standard curves generated by the CAM assay for the two allergen concentrations were erratic, falling short of quantifying the test sample. This is the first time a monoclonal IgM is successfully applied as a primary and secondary antibody in the xMAP format. The routine application of this assay will be consolidated as new IgM-based xMAP diagnostics become available.