Detection of Campylobacter PCR DNA by hybridization with a microtiter plate immobilized RNA probe

Quantitative method to determine mRNA levels by reverse transcriptase-polymerase chain reaction from leukocyte subsets purified by fluorescence-activated cell sorting: application to peripheral cannabinoid receptors

BACKGROUND

While cytometry is widely used in the detection of cell proteins, its application to quantitative evaluation remains problematic when target proteins or receptors are weakly expressed in cells. Reverse transcriptase-polymerase chain reaction (RT-PCR) is a technique whose sensitivity and specificity make it appropriate for analyzing nucleic acids and thus genes expressed in cells. Combining these two techniques, we developed a method to quantify the transcript expression of the peripheral cannabinoid receptor (CB2-r) in peripheral blood lymphocyte subpopulations and in tonsillar B-cell subpopulations.

METHODS

This strategy first involves quantitative RT-PCR performed kinetically, followed by enzyme detection of PCR products using an oligonucleotide probe sandwich-hybridization assay onto microplates.

RESULTS

B cells exhibit CB2-receptor mRNA levels 10 times higher than those of other lymphocyte subsets. Using this technique, we observed a modulation of CB2-r mRNA level following tonsillar B-cell differentiation. Lastly, this new technology was validated by comparing the mRNA levels of CB2-r with the expression of CB2-r proteins assayed by flow cytometry, using specific CB2-r antibody labelling.

CONCLUSIONS

This method allows precise measurement of the mRNA of CB2-r performed on cell numbers as low as 10(5) after sorting. Its performance, high accuracy, reproducibility, and reliability make it a valuable tool for assaying proteins weakly expressed in cells.

Microtitre plate riboprobe system for detection of ultrasonicated Campylobacter jejuni genomic DNA

Microtitre plate nucleic acid probe hybridization systems were developed for the detection of thermophilic Campylobacter and Campylobacter jejuni. Specific RNA probes obtained by in vitro transcription of DNA templates synthesized by polymerase chain reaction using two sets of specific primers incorporating bacteriophage T7 promoter sequences were immobilized on a microtitre plate. The hybridizations were carried out on samples of genomic DNA sheared by ultrasonication. Optimum conditions for the ultrasonic treatment were determined in order to obtain the highest degree of hybridization with immobilized RNA probe. Finally, detection of RNA-DNA hybrids in the wells was accomplished by an immunoenzymatic assay using a monoclonal anti-RNA-DNA hybrid antibody. This rapid, simple hybridization and immunoenzymatic assay system will facilitate the detection of Campylobacter in foods and clinical samples.