Lack of correlation between bcg-induced tuberculin skin test sensitisation and protective immunity in cattle

A. O. Whelan*, M. Coad, B. L. Upadhyay, D. J. Clifford, R. G. Hewinson, H. M. Vordermeier

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

37 Citations (SciVal)

Abstract

Vaccination of cattle with Mycobacterium bovis Bacille Calmette-Guérin (BCG) can provide significant protection against bovine tuberculosis (TB). However, BCG vaccination sensitises animals to respond to the tuberculin skin-test. This provides a potential operational impediment to the use of BCG as a cattle vaccine since the tuberculin skin-test is the primary surveillance tool used by many countries with 'test and slaughter' control strategies. Currently, it is also unclear what BCG-induced skin-test conversion means in respects to BCG's protective immunity. In the current study we first investigated the duration of tuberculin skin-test sensitisation in calves neonatally vaccinated with BCG. BCG vaccination induced strong skin-test responses in calves during their first 6 months. However, a rapid decay in skin-test sensitivity was observed after this time. Between 6 and 9 months this represented a reduction from 80% to 8% of calves providing a positive response in the single intradermal comparative cervical tuberculin test at standard interpretation. We next investigated the relationship between BCG induced skin-test sensitivity and retention of protective immunity. Calves were neonatally vaccinated with BCG and subsequently divided into 2 groups based on retention or loss of tuberculin skin-test responses after 6 months. In contrast to their skin-test responsiveness, these vaccinates maintained their tuberculin specific IFN-γ blood responses. Moreover, irrespective of their pre-challenge skin-test responses, following M. bovis challenge both groups of BCG vaccinated calves demonstrated comparable levels of protection, as evidenced by reduced TB-associated pathology. Therefore, we have demonstrated that following neonatal BCG vaccination of cattle, tuberculin skin-test responder frequencies waned rapidly after 6 months but importantly, loss of skin-test sensitivity did not correlate with loss of protective immunity. These findings could have implications for the practical application of BCG based cattle vaccines.

Original languageEnglish
Pages (from-to)5453-5458
Number of pages6
JournalVaccine
Volume29
Issue number33
Early online date02 Jun 2011
DOIs
Publication statusPublished - 26 Jul 2011

Keywords

  • BCG
  • Bovine tuberculosis
  • DIVA
  • Skin-test
  • Tuberculin
  • Vaccination

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