Abstract
Vaccination would be preferred to leptospirosis control measures. However, current vaccines are heat killed whole-cell bacterins that generate serovar specific protection and several side effects. Modern molecular assays have revealed antigens that may replace traditional whole-cell vaccines. Among these, LigB protein is surface-exposed outer membrane protein of virulent leptospires and therefore potential target of a protective immune response. Some unsuccessful attempts at using these antigens as vaccines have been reported. However, we believe that immune modulation through alternative adjuvants and co-adjuvants may overcome previous setbacks. In this light, our study aimed to evaluate the protective immune response in hamsters vaccinated with 40 µg of rLigBNI using oil adjuvant (OA), with or without green propolis (GP) as co-adjuvant. Upon a challenge, all groups immunized with rLigBNI, coupled or not with GP, were highly immunogenic and revealed statistically significant (p<0.05) protection of hamsters from lethal leptospirosis. Additional studies are being carried out to assess the optimum dose, protection against heterologous challenge, and vaccine dynamics.
Highlights
In the last decades, leptospirosis has been recognized as an emergent global public health issue (Costa et al, 2015).The disease is mostly an occupational hazard in developed countries
This study aimed to assess the protective immune response with a lethal challenge assay in the hamster model vaccinated with recombinant LigBNI antigen using oil adjuvant (OA), with or without green propolis (GP), which only found in Brazil and produced from a plant commonly known as “Alecrim do Campo” (Baccharis dracunculifolia) (Banskota et al, 2001), as a co-adjuvant
We assessed the effect of propolis associated with recombinant subunit vaccine on the immune response and protection against lethal leptospirosis challenge
Summary
Leptospirosis has been recognized as an emergent global public health issue (Costa et al, 2015). The disease is mostly an occupational hazard in developed countries. In underdeveloped or developing countries, lack of sanitation, favorable climate conditions, and the presence of reservoir hosts, especially Rattus norvegicus, makes tropical regions ideal for the development of leptospirosis (Hartskeerl et al, 2014; Haake, 2015). The initial infection occurs when leptospires in the environment (soil or water) penetrate abraded skin or mucosal membranes. The bacteria migrate through tissue barriers until it reaches the bloodstream, quickly establishing a systematic infection and compromising several organs, especially the kidney, liver, and lungs (CDC, 2020). The immune response can be jeopardous, secreting pro-inflammatory cytokines, leading to inflammation and tissue damage, a reaction known as Jarish-Herxheimer (Dhakal et al, 2021)
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