| Toxoplasma gondii is a protozoan obligate intracellular parasite that causes the disease toxoplasmosis. Although the infection is generally asymptomatic or results in a clinical disease that is not recognized, it can cause severe health problems in individuals who are immunocompromised such as congenitally infected infants, transplant recipients, and AIDS patients. Infection of pregnant woman can lead to abortion, hydrocephalus, cerebral calcification, and/or chorioretinitis. Serologic diagnosis, based on the detection of Toxoplasma-specific immunoglobulin (Ig) G and IgM antibodies in the serum, is often used to determine the immune status of patients, and prenatal screening for antibodies is routine practice in clinical laboratories, Quality assurance of serologic testing is important to ensure accurate and reliable screening of susceptible individuals and quality control material is essential.Our previous study prepared the anti-T. gondii human-mice chimeric IgM antibody by genetic engineering, splicing the anti-P30 antigen IgG antibody variable region gene and human IgM constant region gene.As expected, this kind of chimeric antibody had pvovided information about the surrogate for IgM quality control. However, the chimeric IgM antibody could not completely simulate the natural IgM antibody because it reacts with one antigen (P30), not with the whole antigen. Thus, in the present study, we immuned rabbits with nature T. gondii antigen and extracted the PBMC, then amplified variable region genes libraries of light chain and heavy chain using cDNA as template. The libraries were re combinated with human antibody constant gende of light chain and heavy chain. If the chimeric gene libraries were expressed in mammalian cell, polyclonal antibodies chould be expressed and the high affinity chimeria antibody could also be screened out and they could used as the surrogates for anti-pathogen IgM quality control.In conclusion, the preparation of human-rabbit chimeric antibody gene libraries described in this part not only shows a new way in the high affinity anti-T. gondii chimeria antibody screening, but also has great value in research for T. gondii quality control material production.There is wide variety of assays available for the detection of toxoplasma-specific IgG.ELISA and CIA were the most commonly used methods in the laboratories.There are many manufactures producing toxoplasma-specific IgG testing kits and indirect method is the most used detection principle. No matter to any kit or any method, the comparability of the resuts for different laboratories or kits is very important, which is the aim of standardization for clinical detection. To realize the aim, the traceability of value is the most basic premise. In 2004, the National Institute for Biological Standards and Control (NIBSC) established international standard for human anti-Toxoplasma IgG(Code number:01/600), with an assigned potency of 20 IU per ampoule of total anti-Toxoplasma antibodies and it’s the first IS provided by World Health Orgnization.However, the IS could not be widely used in China because it’s difficult to get and the price is very high.To meet the demand of clinical detection, the present study developed reference material for human anti-Toxoplasma IgG tracing back to 01/600 and the reference material was approved as national level standard material (Code number:GBW09192). The usage of the reference material could realize the results comparability of anti-Toxoplasma IgG testing.The reference is intended for use as a standard or reference material in laboratory work in relation to biological research, manufacturing or quality control testing of biological products. This material can be used as internal quality control or working reagent in routine laboratory. The reference is also can be used in external quality assessment (EQA) schemes of anti-Toxoplasma IgG testing. It allows for participating laboratories assess whether their testing results are comparable with other clinical laboratories testing results, and the participating laboratories should monitor the results of EQA and implement correctives action to improve its performance levels when their results are discrepant with expected results, which accelerate the progress of standardization for anti-Toxoplasma IgG detection.
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