Comparative study of LAL Lps detection method and mouse weight gain test for assessment of non toxicity of pertussis vaccine

Whooping cough or pertussis is an infectious disease of the upper respiratory tract caused by the gramnegative coccobacillus Bordetella pertussis and a major cause of childhood morbidity and mortality. It is characterized by paroxysmal cough, whoop and vomiting. Spread takes place through air droplets produced with cough or sneezes. The most severe disease occurs in infants and young children, and it is usually milder in adolescents and adults who constitute a reservoir and are a source of spread to young children. Pertussis is therefore still one of the world's leading causes of vaccine-preventable deaths. In Iran, active immunization was done for prevention of whooping cough that vaccine includes killed bacteria. This vaccine is combination of diphtheria, tetanus and pertussis vaccine. The mouse weight gain (MWG) test was evaluated for its value in toxicity testing for pertussis vaccines. This test is a qualitative and general. Mouse weight gain test has some disadvantages including many laboratory animal usage, low repeatability and long time consuming. The medical and scientific communities have previously reported that the presence of endotoxin in commercial vaccines may have negative effects on vaccine recipients. According to the high concentrations of lopopolysacharide (LPS) or endotoxin may be present in whole-cell pertussis vaccine, endotoxin contents should be determined by Limulus amebocyte lysate (LAL) assay that is recommended test for safety and toxicity evaluation of pertussis vaccine. The vaccines analyzed with the LAL assay were whole-cell pertussis vaccine lots manufactured by Razi vaccine and serum institute. Doing this test is essential before MWG test because reduce laboratory animals' consumption and increase toxicity determination speed. On the other hand, world health organization (WHO) does not determine an acceptable international cut off for pertussis vaccine. However, this responsibility should be done by vaccine production institutes. In the present study here, endotoxin cut off for pertussis vaccine was determined and LAL assay also was applied as prescreening model. In addition, relation of MWG test results with LAL assay results was investigated for toxicity evaluation of pertussis vaccine. For this purpose, simultaneously, MWG and LAL assay were done on 44 pertussis vaccine (detoxified by formaldehyde and hyamin) lot. Endotoxin contents of suspensions were measured and endotoxin cut off for these vaccines was determined. The results of these assays show endotoxin cut off for Razi institute pertussis vaccine 40 OU/ml is 758472 EU/ml and 11559 EU/ml is for vaccine 32 EU/ml. Hence, endotoxin cut off for vaccine 40 OU/ml is about 65 fold more than endotoxin cut off of vaccine 32 OU/ml. In addition, detoxification time of pertussis suspension with formaldehyde was 5.5 to 6 month. This time is about 2 to 3 fold more than expected time (about 1.5 to 2 month). In conclusion, according to the findings of this investigation, LAL assay should apply on Razi institute pertussis vaccine. If the endotoxin contents of vaccine were less than determined cut off, MWG assay will be applied on vaccine. Finally, if MWG assay also will be passed, vaccine will be passed.