Abstract
Different mycobacteria carrying cloned genes for heterologous protective antigens have been proposed as vaccine vehicles. In this study, the stability of the expression of β-galactosidase was studied in Mycobacterium smegmatis using integrative (pMV361:: lacZ) and replicative (pMV261:: lacZ) vectors. Recombinant M. smegmatis forms blue colonies on X-gal plates. Occasional white mutants encountered while plating on X-gal plates were genetically analysed. The loss of lacZ phenotype was due to insertion of an IS element in lacZ gene of integrative vector whereas in case of replicative vectors, loss of lacZ phenotype was due to deletions of different sizes in the lacZ gene and the P hsp60 promoter region. The frequency of such events was rare, 1.7 × 10 −5 in integrative vector and 2 × 10 −3 in the case of replicative vector. The integrative vector seemed more stable in terms of expression of foreign genes in mycobacteria. Hence, the rearrangements reported in the present study warrant serious consideration before implementing mycobacteria as recombinant vaccines.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have