Outer surface of Gram-negative bacteria are covered by an extra outer membranous structure present outside the cytoplasmic membrane and the peptidoglycan layer of the cell wall. Outer Membrane proteins (OMPs) are distinctive to grame negative bacteria (Zha et al., 2016) and used as carrier proteins to foreign peptide epitopes present on the bacterial cell surface. The major function of the bacterial outer membrane is to act as permeability barrier to remove many of the harmful molecules that present in their external medium, such as antibiotics, disinfectants, and detergents (Nikaidoi and Vaara, 1985). Porins, OmpC, PhoE, LamB lipoproteins as well as the OmpA protein are members of OMPs (Lång, 2000) and all having a common structural pattern. They consist with number of transport proteins which are open path to a limited range of solutes. (Nikaido and Saier, 1992). Thus OMPs function as molecular sieves to permit diffusion of hydrophilic molecules into periplasmic space (Jeanteur et al., 1991; Lång, 2000). As they present on the bacterial cell surface they are identified as an ideal targets for bactericidal and protective anti-bodies. More over their characteristics such as surface exposure, conservation among strains and ability to induce immune responses make them to be a good target for vaccine and drug development against grame negative bacterial infections. Thus OMPs are identified as an attractive component as vaccine antigen as well as immunotherapeutics.
