Genetic Characterization of Diphtheria B to Evaluate Vaccine Efficacy in Indonesia

Background And Objectives: Blocking the attachment of diphtheria toxins to host cells through the intact receptor binding site ( B) was the initial mechanism of action of the diphtheria vaccine. Diphtheria outbreaks in populations with good vaccination coverage can be caused by mutations or changes in the genetic structure of the B protein. The aim of this study was to characterize the Tox B protein produced by isolated from 2018 to 2019 in patients in Jakarta who had already received the diphtheria vaccine.

Materials And Methods: Of the 89 throat swab specimens of patients with a clinical diagnosis of diphtheria, 10 were positive for diphtheria and toxin. PCR was used to amplify the B DNA fragment in the 10 positive isolates. DNA sequencing was conducted with overlapping primers and the DNA sequences were analysed by using SeqScape V2.7.

Results: Of the 10 isolates, nine isolate showed a DNA mutation (G30A), but the mutation did not change the amino acid encoding arginin (silent mutation). Our findings indicate that the efficacy of the diphtheria vaccine used in Indonesia has not decreased because of mutations in the B genes not change the amino acid.

Conclusion: Overall, there are no amino acid changes in the B protein, indicating that the outbreaks are not affected by mutation in B. Another possible mechanism - overexpression of the toxin - is likely responsible for causing diphtheria in patients who have a complete history of immunization in Indonesia.