Evaluation of the ELISA technique to search for anti-Toxoplasma gondii IgG in juices from sun dried meat

Abstract Toxoplasmosis is an important waterborne and foodborne zoonosis, whose agent is Toxoplasma gondii, and it affects both humans and production animals. This zoonosis is cosmopolitan and its prevalence is related to the consumption of raw or undercooked meat, this habit being considered one of the main risk factors. The control of the potential transmission of toxoplasmosis by meat is relevant, especially in artisanal products such as sun dried meats, which are handcrafted and may be consumed raw or undercooked. In this study, we proposed to evaluate the presence of immunoglobulins of the IgG anti T. gondii class by an ELISA immunoassay technique, standardizing a dilution of the meat juice obtained by defrosting sun dried meat produced from the muscles of experimentally infected animals and also from sun dried meats commercialized in shops in the north of Brazil. The results showed that the potential of the meat juice as a biological material was limited in processed meats, and the test was only possible in samples that showed an optical density (OD) equal to or greater than 0.116, a range that guaranteed the presence of sufficient blood for the ELISA assay, allowing for the measurement of specific anti-T. gondii immunoglobulins. Of the 32 samples of beef obtained from cuts from experimental cattle, only 9 (28%) presented sufficient blood to be tested, as measured by an OD equal to or greater than 0.116, 7 being positive, obtained from cuts from infected experimental animals, and 2 negative, obtained from cuts from control animals. Of the 42 samples of juice from retail sun dried meat, only 6 (14.28%) presented enough blood for the tests and only one presented anti T. gondii immunoglobulins, in agreement with data from the literature. The results were promising and demonstrated the importance of developing research and new approaches in the sanitary control of food offered to the population.

摘要：弓形虫病（Toxoplasmosis）是一类重要的经水、经食物传播的人兽共患病，其病原体为刚地弓形虫（Toxoplasma gondii），可感染人类及养殖动物。该人兽共患病呈全球分布，其流行与生食或半生食肉类的行为密切相关，该习惯被视为主要风险因素之一。通过肉类传播弓形虫病的防控工作具有重要意义，尤其针对风干肉这类手工制作、可生食或半生食用的手工食品。
本研究采用酶联免疫吸附试验（ELISA，enzyme-linked immunosorbent assay）技术检测抗刚地弓形虫IgG类免疫球蛋白，对实验感染动物肌肉制备的风干肉解冻所得肉汁进行稀释度标准化，并同时对巴西北部地区商铺售卖的市售风干肉样本开展检测。
结果显示，肉汁作为生物材料在加工肉制品中的检测潜力有限，仅当样本光密度（OD）值大于或等于0.116时，方可开展检测——该阈值可保证样本中含有足够的血液成分以满足ELISA检测需求，从而实现抗弓形虫特异性免疫球蛋白的定量检测。在32份实验肉牛肌肉组织样本中，仅9份（28%）的OD值达标，其中7份来自感染实验动物的肌肉组织，呈阳性反应；2份来自对照动物的肌肉组织，呈阴性反应。在42份市售风干肉汁样本中，仅6份（14.28%）的OD值达标，且仅1份样本检出抗刚地弓形虫免疫球蛋白，这与现有文献报道的数据相符。
本研究结果具有积极意义，证实了针对供民众食用的食品开展卫生防控相关研究与新方法探索的重要性。