Evaluation of the viability of the Bulgarian BCG vaccine by the adenosine triphosphate assay

Abstract

We applied a modified assay for the measurement of the intracellular ATP content as an alternative biochemical method for estimating the viability of the BCG vaccine instead of the standard cultural microbiological assay. Eight lyophilized BCG ampoule samples (Lot 287-2 and Lot 254-2, Bulgarian BCG strain SL222 Sofia) were tested on different days. Each calibration curve was measured for the following range of ATP concentrations: 100, 10, 5, 2.5, 1.25, 0.625, 0.3125, and 0.1562 pmol. The obtained results were compared to the traditional cultural colony counting method for evaluating the viability of the BCG vaccine. The NCP of Lot 287-2 (min 2.325–max 3.300) was higher in comparison to Lot 254-2 (min 1.438–max 3.330). That result corresponded to higher ATP-content registered for Lot 287-2 (min 0.409–max 1.338) than Lot 254-2 (min 0.18–max 1.104). Our results confirmed the observation made by other researchers that the modified ATP assay is a reliable, simple, and quick method for the evaluation of the viability of the BCG vaccine. Additional compiled data about all BCG strains are needed to perform studies on the correlation between the luciferin-luciferase bioluminescent ATP assay and the cultural method for viability and enumeration of the units in the lyophilized BCG vaccine.

Keywords:

• Luminescence
• ATP
• CFU
• BCG
• vaccine
• method

Author contributions

The authors have contributed substantially to the work reported. E.P.: conceptualization and design of the study, performance of the ATP luminescent assays, calculations and data analysis, visualization, conclusions, and writing the major part of the draft manuscript. A.M.: performance of the microbiological assays and calculations. T.S.: conceptualization and design of the study, writing–review and editing; funding acquisition. All three authors discussed together the obtained results and conclusions and made corrections to the text. All authors have read and approved the final version of the paper.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data are available on request from the corresponding author [E.P.] upon reasonable request.

Additional information

Funding

The authors acknowledge the financial support of BB-NCIPD Ltd., Bulgaria.