title: Immunoprotective potential of in silico predicted Acinetobacter baumannii outer membrane nuclease, NucAb.
abstract: Acinetobacter baumannii is an emerging multi-drug resistant pathogen causing significant mortality in hospitalized ICU patients which demands developing new methods for prevention and treatment. A. baumannii 19606 proteome was analysed in silico through the online tool Vaxign for finding potential vaccine candidates. The selected nuclease (NucAb) was predicted to possess all the attributes of a promising vaccine candidate like outer membrane localization, high adhesin probability (0.53), one transmembrane helix only, non-homology to human proteins and presence of B-cell and T-cell epitopes binding with high affinity (percentile rank≤1) to HLA alleles prevalent at high frequency in North Indian populations. nucAb gene was highly prevalent (100%) among the clinical isolates (40/40) and conserved (>98%) among NCBI sequenced Acinetobacter strains. It was cloned in pET28a, purified and its immunoprotective potential was validated in murine pneumonia model. Immunization of BALB/c mice with recombinant NucAb (25μg) elicited high antibody titre (1-5×10(5)) which reduced bacterial load by 5 log cycles in lungs of mice challenged with optimized lethal dose (10(8)CFU). Lung histopathology revealed marked suppression of inflammation. Pro-inflammatory cytokines (TNF-α and IL-6) levels were reduced significantly and anti-inflammatory (IL-10) cytokine increased in lungs and serum leading to decreased severity and slow progression of disease. Though active immunization showed low survival rate (20%), passive immunization improved the survival (40%). This is the first study reporting an outer membrane nuclease as a vaccine candidate in Gram negative bacterium, A. baumannii through reverse vaccinology approach.
authors.affiliation: Department of Microbiology, Basic Medical Sciences Building, South Campus, Panjab University, Chandigarh, India.
authors.forename: Nisha
authors.initials: N
authors.lastname: Garg
authors.affiliation: Department of Microbiology, Basic Medical Sciences Building, South Campus, Panjab University, Chandigarh, India.
authors.forename: Ravinder
authors.initials: R
authors.lastname: Singh
authors.affiliation: Department of Microbiology, Basic Medical Sciences Building, South Campus, Panjab University, Chandigarh, India.
authors.forename: Geeta
authors.initials: G
authors.lastname: Shukla
authors.affiliation: Department of Biotechnology, Basic Medical Sciences Building, South Campus, Panjab University, Chandigarh, India.
authors.forename: Neena
authors.initials: N
authors.lastname: Capalash
authors.affiliation: Department of Microbiology, Basic Medical Sciences Building, South Campus, Panjab University, Chandigarh, India. Electronic address: princess@pu.ac.in.
authors.forename: Prince
authors.initials: P
authors.lastname: Sharma
mesh_terms: D000151:Acinetobacter Infections / Q000517:prevention & control*; D040981:Acinetobacter baumannii / Q000235:genetics / Q000276:immunology*; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D058491:Bacterial Load; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000276:immunology*; D001428:Bacterial Vaccines / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology*; D019295:Computational Biology; D017124:Conserved Sequence; D003851:Deoxyribonucleases / Q000235:genetics / Q000276:immunology*; D004195:Disease Models, Animal; D018985:Epitopes, B-Lymphocyte / Q000235:genetics; D018984:Epitopes, T-Lymphocyte / Q000235:genetics; D005260:Female; D006680:HLA Antigens / Q000235:genetics; D006651:Histocytochemistry; D006801:Humans; D007116:Immunization, Passive; D008168:Lung / Q000382:microbiology / Q000473:pathology; D008807:Mice, Inbred BALB C; D018410:Pneumonia, Bacterial / Q000517:prevention & control; D016019:Survival Analysis; D014614:Vaccines, Synthetic / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001428:Bacterial Vaccines; D018985:Epitopes, B-Lymphocyte; D018984:Epitopes, T-Lymphocyte; D006680:HLA Antigens; D014614:Vaccines, Synthetic; D003851:Deoxyribonucleases
keywords: Acinetobacter baumannii; Cytokines; Epitopes; Outer membrane nuclease; Reverse vaccinology; Vaccine