The expression of soluble and active recombinant Haemophilus influenzae IgA1 protease in E. coli

IgA1 Protease as a Vaccine Basis for Prevention of Bacterial Meningitis

Abstract

The review covers the study of the protective properties of IgA1 protease and the possibility of creating a vaccine preparation for the prevention of bacterial meningitis of various origins on its basis. Bacterial meningitis belongs to the group of socially dangerous diseases and is characterized by a severe course, numerous complications and high mortality. The approaches used at present in world practice to create antimicrobial vaccines are based on a narrow targeting against a specific pathogen. The development of a monocomponent vaccine against a wide range of bacterial pathogens with a common virulence factor is still relevant. IgA1 protease, a protein that is one of the main virulence factors of a number of gram-negative and gram-positive bacteria, can serve as such an antigen. Bacterial IgA1 protease is uniquely specific for immunoglobulins A1 (IgA1), cleaving peptide bonds in the hinge regions of the IgA1 in humans and other higher primates. Bacteria, getting on the mucous membrane, destroy IgA1, which acts as the first barrier to protect the body from infections. Neutralization of IgA1 protease at this stage can become an obstacle to the development of infection, hindering the adhesion of a number of pathogens that produce this protein. The data available in the literature on the mechanism of antibacterial protection are scattered and ambiguous. The review considers the literature data and the results of our own experiments on the protective activity of IgA1 protease. We have shown that the recombinant meningococcal IgA1 protease and some of its fragments protect mice from infection with a live virulent culture not only of meningococci of the main epidemic serogroups (A, B, C, and W135), but also of some of the most common virulent pneumococcal serotypes. The data obtained indicate the possibility of creating a monocomponent vaccine against these and, possibly, other bacterial infections. Currently, significant progress has been made in studying the structure and functions of secreted proteins in the bacteria Neisseria meningitidis and Haemophilus influenzae. In this review we describe protein translocation systems of N. meningitidis, which are related to the secretion of proteins in these bacteria, and also present modern data on the functions of these proteins. Analysis of experimental data on the structure of IgA1 protease of N. meningitidis and the formation of immunity during vaccination is of key importance in the development of prophylactic preparations.

Perspectives on how mucosal immune responses, infections and gut microbiome shape IgA nephropathy and future therapies

Infections have been considered to play a critical role in the pathogenesis of IgA nephropathy (IgAN) because synpharyngitic hematuria is a common feature in IgAN. However, how infections participate in this process is still debated. More recent studies have also revealed that the alteration of the gut microbiome exerts a profound effect on host immune responses, contributing to the etiology or progression of autoimmunity. Considering IgA as the first line of defense against bacterial and viral antigens, this review evaluates the relationships among intestinal infections, gut microbiome, and IgA for a better understanding of the pathogenesis of IgAN. Moreover, as a prototype of IgA immunity, we provide detailed clarification of IgAN pathogenesis to shed light on other diseases in which IgA plays a role. Finally, we discuss potential therapies focusing on microbes and mucosal immune responses in IgAN.

Cloning and Expression of H. influenzae 49247 IgA Protease in E. coli

IgA protease is secreted by various mucosal pathogenic bacteria which can cleave human immunoglobulin A1 (IgA1) in its hinge region. In addition to be considered as a virulence factor, it's reported that IgA protease can also be used for IgA nephropathy (IgAN) treatment. Our previous study identified bacteria H. influenzae 49247 expressed high activity of IgA protease with promised application in IgAN therapy. In this study, we cloned the IgA protease gene of H. influenzae 49247 with degenerate primers. Alignment analysis indicated that H. influenzae 49247 IgA protease showed unique DNA and amino acid sequence but with typical endopeptidase domain and beta transporter domain compared with known IgA proteases from the same species. To facilitate expression and purification, the H. influenzae 49247 IgA protease gene was sub-cloned into the pET28-A(+) vector with insertion of a 6xHis tag downstream of the endopeptidase domain and upstream of the potential autocleavage site. The recombined IgA protease can be constitutively expressed in E. coli and secreted into the culture medium. With a simple nickel affinity binding, the secreted IgA protease can be purified with high purity (95%) and a molecular weight of about 130 kDa. The identity of the IgA protease was validated by the presence of 6xHis tag in the purified protein by western blotting and its ability to cleave human IgA1 molecule. Collectively, the successful cloning, expression and purification of H. influenzae 49247 IgA protease will augment its therapeutic study in IgAN treatment.

IgA1 Protease Treatment Reverses Mesangial Deposits and Hematuria in a Model of IgA Nephropathy

IgA nephropathy (IgAN), characterized by mesangial IgA1 deposits, is a leading cause of renal failure worldwide. IgAN pathogenesis involves circulating hypogalactosylated IgA1 complexed with soluble IgA Fc receptor I (sCD89) and/or anti-hypogalactosylated-IgA1 autoantibodies, but no specific treatment is available for IgAN. The absence of IgA1 and CD89 homologs in the mouse has precluded in vivo proof-of-concept studies of specific therapies targeting IgA1. However, the α1KI‑CD89Tg mouse model of IgAN, which expresses human IgA1 and human CD89, allows in vivo testing of recombinant IgA1 protease (IgA1‑P), a bacterial protein that selectively cleaves human IgA1. Mice injected with IgA1‑P (1-10 mg/kg) had Fc fragments of IgA1 in both serum and urine, associated with a decrease in IgA1-sCD89 complexes. Levels of mesangial IgA1 deposits and the binding partners of these deposits (sCD89, transferrin receptor, and transglutaminase 2) decreased markedly 1 week after treatment, as did the levels of C3 deposition, CD11b(+) infiltrating cells, and fibronectin. Antiprotease antibodies did not significantly alter IgA1‑P activity. Moreover, hematuria consistently decreased after treatment. In conclusion, IgA1‑P strongly diminishes human IgA1 mesangial deposits and reduces inflammation, fibrosis, and hematuria in a mouse IgAN model, and therefore may be a plausible treatment for patients with IgAN.