Executive Summary : | Cell surface carbohydrates are extremely important as they act as the first point of contact to other cells and extracellular entities like microbes, proteins, toxins and pathogens like bacteria, virus, fungi and other parasites. Thus, in one hand the external carbohydrate architecture often becomes responsible for the interactions with other hosts and on the other hand as gate-keeper towards the entry of various extracellular objects. It acts as the determining factor for assigning unique physiological and pathological identity to the organisms. Carbohydrates have also been recognised as differential markers and as antigenic determinants. The glycan-based information of the pathogens thus plays a vital role in the process of pathogenic invasion and helps to activate and modulate the immune system of the host organisms. Proper and systemic study of these glycan-mediated life processes thus has been the need of the hour. Fundamental understanding of these the processes may provide insights towards the design, development and implementation of various carbohydrate based therapeutic tools. Acinetobacter baumannii is a pleomorphic, non-motile, aerobic Gram-negative bacillus. This opportunistic pathogen is primarily associated with hospital acquired infections targeting immunocompromised individuals having long stay in hospitals. Recently A. baumannii has been designated as “red alert” human pathogen for its extensive antibiotic resistance spectrum. It has been incorporated in the list of most common and serious Multi Drug Resistant (MDR) pathogens under the acronym “ESKAPE” (standing for Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter spp.). A. baumannii produces a thick capsular polysaccharide (CPS) on the cell surface that is majorly responsible for its virulence. The CPS is composed of long oligosaccharide repeating units known as K units. The CPS varies widely between strains in terms of its sugar contents, linkage pattern and additional modifications. Recently, Knirel et. al determined the structures of the repeating units from the CPS of A. baumannii K5, K90 and ACICU. The present proposal will deal with the synthesis of the oligosaccharide repeating units associated with the CPS of these bacterial strains and explore the possibility of further conjugation of the oligosaccharide with carrier protein to design potential vaccine candidates. |