On the other hand, ME-49 (type II), PB-r (recombinant), and VEG (type III) were capable of avoiding NO production during the initial hours of infection but probably did not sustain NO production inhibition because they could not avoid the IRG microbicidal system causing their death, return of macrophage response to IFN-γ and LPS, and re-expression of iNOS and NO production. This evidence concerns the gene NOS2 and infection.