Interference of freeze-dried Hepatitis A vaccine (H2 strain) on testing bovine serum albumin content by ELISA

Abstract

Objective To carry on preliminary research on interference effects of freeze-dried attenuated Hepatitis A vaccine（H2 strain）on testing residual Bovine Serum Albumin content by ELISA kit. Methods Interference test was conducted according to Appendix VIII, Chinese Pharmacopoeia (Vol III,2010 edi), and the interference level and its possible resources were explored. Results The protective additives of HAV live vaccine do have certain interference on determining residual BSA content by ELISA kit, among which Cysteine and Glutamic acid might play the leading roles. The general BSA recovery rate is 54% to 85%. We assessed the interference degree by using series of different concentration of single amino acid ingredient: cysteine (0 to 0.2%),glutamic acid(0 to 0.8%). We found BSA recovery rate always higher than 70% with 0 to 2mg/ml (0.2%) cysteine, lower with 0.5 to 2mg/ml than with 0 to 0.5mg/ml and did not differ between 0.5 and 2mg/ml cysteine; And the BSA recovery rates were up to 100% if we applied Glutamic acid (concentration not higher than 0.1%) as an interference. It deserves to be mentioned that the interference effects of Glutamic acid become more stronger along with concentration rising from 0.1% to the peak 0.8%(8mg/ml),the test results showed to be not higher than 2.5ng/ml when we set 20ng/ml BSA standards as a target sample, so that the recovery rate is not more than 12.5%. Conclusion The real value of residual BSA content of HAV vaccine should be reported based on the extent of interference. Here when the result appeared to be negative by ELISA we would report as <2.5 ng/ml and as < 5ng/ml if the testing value showed between 0 and 3ng/ml. And what we have done might be a reference to the other enterprises on optimizing the protocol for cryopreservation or evaluating the residual BSA content results.