Immunity induced by valine-glycine repeat protein G imparts histoprotection of vital body organs against Acinetobacter baumannii

Saeed Alipouri1, Iraj Rasooli1,2, Mohammad Hossein Ghaini3, Abolfazl Jahangiri4, Shakiba Darvish Alipour Astaneh5, Fatemeh Ramezanalizadeh6
1Department of Biology, Shahed University, Qom Expressway, Tehran, Iran
2Molecular Microbiology Research Center and Department of Biology, Shahed University, Tehran, Iran
3Department of Anatomical Sciences and Pathology, School of Medicine, Shahed University, Tehran, Iran
4Applied Microbiology Research Center, Systems Biology and Poisonings Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran
5Department of Biotechnology, Semnan University, Central Administration of Semnan University, Semnan, Iran
6Department of Microbiology, Shahed University, Tehran, Iran

Tóm tắt

Efforts toward the development of an effective vaccine against Acinetobacter baumannii, one of the most notorious nosocomial pathogens, are still ongoing. In this regard, virulence factors are interesting targets. Type VI secretion system (T6SS) participates in the pathogenicity of A. baumannii. VgrG is a crucial component of T6SS prevalent among A. baumannii strains. This study was conducted to evaluate the immunoprotectivity of recombinant VgrG (rVgrG) cloned and over-expressed in Escherichia coli BL21 (DE3). BALB/c mice were immunized with the purified rVgrG. Specific anti-VgrG IgG titers were assessed by ELISA. Actively and passively immunized mice were challenged with lethal doses of A. baumannii ATCC 19606. The survival rate, the bacterial burden, and histopathology of tissues in infected mice were examined. Anti-VgrG IgG (p < 0.0001) was significantly increased in immunized mice. No death was seen in actively immunized mice infected with the lethal dose (LD) of 1.9 × 108 CFU of A. baumannii ATCC 19606 within 72 h. Challenge with 2.4 × 108 CFU of the pathogen showed a 75% survival rate. All immunized mice infected with 3.2 × 108 CFU of the pathogen died within 12 h. In passive immunization, no death was observed in mice that received LD of the bacteria incubated with the 1:250 dilution of the immune sera. An increased number of neutrophils around the peribronchial and perivascular areas were seen in unimmunized mouse lungs while passively immunized mice revealed moderate inflammation with infiltration of mixed mononuclear cells and neutrophils. The livers of the unimmunized mice showed inflammation and necrosis in contrast to the livers from immunized mice. Hyperplasia of the white pulp and higher neutrophils were evident in the spleen of unimmunized mice as against the normal histology of the immunized group. VgrG is a protective antigen that could be topologically accessible to the host antibodies. Although VgrG is not sufficient to be assigned as a stand-alone antigen for conferring full protection, it could participate in multivalent vaccine developments for elevated efficacy.

Tài liệu tham khảo

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