Potency testing of a mixture of eight recombinant proteins in Mycobacterium bovis-sensitized guinea pigs as an alternative of bovine purified protein derivative

Intradermal test (IDT) was used as an official diagnosis of bovine tuberculosis (bTB), mainly caused by Mycobacterium bovis. Test-and-slaughter policy was implemented by many countries for control of bTB due to human health as well as, the health of cattle. Purified protein derivative (PPD) was used as IDT diagnostics, which is the native protein complex from culture supernatant of M. bovis. However, false positive reactors occurred in PPD and IDT due to crossreaction. Furthermore, the procedure of PPD production is bio-hazardous, timeconsuming and laborious. To overcome this, an alternative of PPD is urgently needed. In this study, a mixture of eight (8) recombinant proteins (Remix) ESAT6, HspX, PhoS, MPB70, MPB64, MPB83, Ag85 and SahH was evaluated as an alternative of PPD in M. bovis-sensitized guinea pigs. The skin reaction of Remix (14.7±1.8) was equivalent to that of PPD (15.6±2.8), but those of single recombinant proteins – ESAT6, HspX, and PhoS – were 2.3 ± 3.2, 1.2 ± 2.0, and 1.6 ± 2.0, respectively. In addition, that of Remix in M. avium-sensitized guinea pigs (n = 5) was lower than that of PPD-B. Therefore, Remix could be used as an alternative of PPD for simple and safe production of IDT reagent.