TonB-dependent receptor epitopes expressed in M. bovis BCG induced significant protection in the hamster model of leptospirosis

Abstract

Leptospirosis is an emerging infectious disease caused by pathogenic Leptospira spp. A universal vaccine against leptospirosis is likely to require highly conserved epitopes from pathogenic leptospires that are exposed on the bacterial surface and that generate a protective and sterilizing immune response. Our group recently identified several genes predicted to encode TonB-dependent receptors (TBDR) in Leptospira interrogans using a reverse vaccinology approach. Three leptospiral TBDRs were previously described and partially characterized as ferric-citrate, hemin, and cobalamin transporters. In the current study, we designed a fusion protein composed of predicted surface-exposed epitopes from three conserved leptospiral TBDRs. Based on their three-dimensional structural models and the prediction of immunogenic regions, nine putative surface-exposed fragments were selected to compose a recombinant chimeric protein. A Mycobacterium bovis BCG strain expressing this chimeric antigen encoded in the pUP500/P pAN mycobacterial expression vector was used to immunize Syrian hamsters. All animals (20/20) vaccinated with recombinant BCG survived infection with an endpoint dose of L. interrogan s ( p < 0.001). No animal survived in the negative control group. Immunization with our recombinant BCG elicited a humoral immune response against leptospiral TBDRs, as demonstrated by ELISA and immunoblot. No leptospiral DNA was detected by lipL32 qPCR in the kidneys of vaccinated hamsters. Similarly, no growth was observed in macerated kidney cultures from the same animals, suggesting the induction of a sterilizing immune response. Design of new vaccine antigens based on the structure of outer membrane proteins is a promising approach to overcome the impact of leptospirosis by vaccination. Key points • Predicted surface-exposed epitopes were identified in three leptospiral TBDRs. • An M. bovis BCG strain expressing a chimeric protein (rTBDRchi) was constructed. • Hamsters vaccinated with rBCG:TBDRchi were protected from lethal leptospirosis. Graphical abstract Supplementary Information The online version contains supplementary material available at 10.1007/s00253-021-11726-9.

A New Recombinant Multiepitope Chimeric Protein of Leptospira interrogans Is a Promising Marker for the Serodiagnosis of Leptospirosis

“…Some other Leptospira spp. chimeric constructions have been designed and explored for vaccine [34][35][36][37], but their potential as a diagnostic marker has not been explored yet. Other published dry lab studies explored possible new chimeric construction by using a combination of epitope prediction and molecular docking for vaccine and/or diagnostic goals [38,39].…”

Challenges and Strategies for Developing Recombinant Vaccines against Leptospirosis: Role of Expression Platforms and Adjuvants in Achieving Protective Efficacy

“…Dorneles et al (2020) [ 51 ] investigated the same antigens used in different chimeric constructs to transform BCG. Recently, Bettin et al (2022) [ 52 ] developed an rBCG vectored vaccine expressing a chimeric antigen based on the TonB-dependent receptor (TBDR) epitopes (LIC10896, LIC10964, and LIC12374) from L. interrogans . Hamsters vaccinated with the rBCG:TBDRchi construct were fully protected from lethal leptospirosis, whereas the same recombinant protein as a subunit vaccine failed to protect animals (44.4% survival, p > 0.05; data not published).…”

“…Hamsters vaccinated with the rBCG:TBDRchi construct were fully protected from lethal leptospirosis, whereas the same recombinant protein as a subunit vaccine failed to protect animals (44.4% survival, p > 0.05; data not published). In studies performed by Oliveira et al (2019) [ 50 ], Dorneles et al (2020) [ 51 ], and Bettin et al (2022) [ 52 ], it was shown that rBCG constructs were able to induce immune protection and prevent renal colonization against challenge with virulent L. interrogans . The combination of rBCG and chimeric multiepitope proteins appears to be a promising alternative against leptospirosis [ 53 ].…”

Chimeric vaccine design against the conserved TonB-dependent receptor-like β-barrel domain from the outer membrane tbpA and hpuB proteins of Kingella kingae ATCC 23330

“…TonB-dependent receptors (TBDRs) are outer membrane proteins found in many Gram-negative bacteria that play a key role in the uptake of essential nutrients, such as iron and vitamin B12, from the host environment ( Blanvillain et al, 2007 ; Moynié et al, 2017 ). TBDRs are highly conserved among bacteria and are essential for bacterial survival and growth, making them attractive targets for the development of vaccines ( Grassmann et al, 2017 ; Bettin et al, 2022 ). One advantage of targeting TBDRs is that they are expressed on the outer surface of the bacterial cell, making them accessible to antibodies and other immune system components.…”

“…For example, a vaccine based on the TBDR of the pathogenic bacterium Haemophilus influenzae was shown to be highly effective in preventing infection in a mouse model ( Webb and Cripps, 1999 ). Other studies have focused on the development of vaccines targeting TBDRs in pathogenic bacteria such as Aeromonas hydrophila ( Abdelhamed et al, 2017 ) , Mycobacterium bovis ( Bettin et al, 2022 ), Pseudomonas fluorescens ( Hu et al, 2012 ), and Acinetobacter baumannii ( Yang et al, 2017 ).…”