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Leptospirosis is a public health concern with lethality around 15% of the total cases. The current vaccines against Leptospira infection based on bacterins have several limitations, which require urgent development of new ones. In this context, groundbreaking approaches such as peptide-vaccines could be used to come around with promising results. Our goal was to identify conserved and immunogenic epitopes from the lipoprotein LruC that could interact with Major Histocompatibility Complex (MHC) I and II. LruC is a conserved lipoprotein expressed during leptospirosis that is considered among vaccine candidates and can be used as source for development of peptide-based vaccines. We searched for peptides that would be recognized by antibodies from either serum of hamsters previously immunized with low-LPS bacterin vaccines or from serum of patients diagnosed with leptospirosis. Immuno properties of seven peptides from LruC protein were evaluated in silico and by Dot Blot assay, and validate by ELISA. Preliminary results pointed one promising peptide that was recognized by the sera. In conclusion, the immunoinformatic approach helps the search and screening of peptides, while the Dot Blot assay, a simple and effective tool, helps to test and validate them. Thus, these prospective techniques together were validated to identify and validate potential peptides for further investigation as peptide-based vaccines or diagnostic methods., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Mariano et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Leptospirosis is a worldwide zoonosis and a serious public health threat in tropical and subtropical areas. The etiologic agents of leptospirosis are pathogenic spirochetes from the genus Leptospira. In severe cases, patients develop a pulmonary hemorrhage that is associated with high fatality rates. Several animal models were established for leptospirosis studies, such as rodents, dogs, and monkeys. Although useful to study the relationship among Leptospira and its hosts, the animal models still exhibit economic and ethical limitation reasons and do not fully represent the human infection. As an attempt to bridge the gap between animal studies and clinical information from patients, we established a three-dimensional (3-D) human lung cell culture for Leptospira infection. We show that Leptospira is able to efficiently infect the cell lung spheroids and also to infiltrate in deeper areas of the cell aggregates. The ability to infect the 3-D lung cell aggregates was time-dependent. The 3-D spheroids infection occurred up to 120 h in studies with two serovars, Canicola and Copenhageni. We standardized the number of bacteria in the initial inoculum for infection of the spheroids and we also propose two alternative culture media conditions. This new approach was validated by assessing the expression of three genes of Leptospira related to virulence and motility. The transcripts of these genes increased in both culture conditions, however, in higher rates and earlier times in the 3-D culture. We also assessed the production of chemokines by the 3-D spheroids before and after Leptospira infection, confirming induction of two of them, mainly in the 3-D spheroids. Chemokine CCL2 was expressed only in the 3-D cell culture. Increasing of this chemokine was observed previously in infected animal models. This new approach provides an opportunity to study the interaction of Leptospira with the human lung epithelium in vitro., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Pathogenic spirochetes from genus Leptospira are etiologic agents of leptospirosis. Cellular vaccines against Leptospira infection often elicit mainly response against the LPS antigen of the serovars present in the formulation. There is no suitable protein candidate capable of replacing whole-cell vaccines, thus requiring new approaches on vaccine development to improve leptospirosis prevention. Our goal was to develop a whole-cell vaccine sorovar-independent based on LPS removal and conservation of protein antigens exposure, to evaluate the protective capacity of monovalent or bivalent vaccines against homologous and heterologous virulent Leptospira in hamster. Leptospire were subjected to heat inactivation, or to LPS extraction with butanol and in some cases further inactivation with formaldehyde. Hamsters were immunized and challenged with homologous or heterologous virulent serovars, blood and organs were collected from the survivors for bacterial quantification, chemokine evaluation, and analysis of sera antibody reactivity and cross-reactivity by Western blot. Immunization with either heated or low LPS vaccines with serovar Copenhageni or Canicola resulted in 100% protection of the animals challenged with homologous virulent bacteria. Notably, different from the whole-cell vaccine, the low LPS vaccines produced with serovar Canicola provided only partial protection in heterologous challenge with the virulent Copenhageni serovar. Immunization with bivalent formulation results in 100% protection of immunized animals challenged with virulent serovar Canicola. All vaccines produced were able to eliminate bacteria from the kidney of challenged animals. All the vaccines raised antibodies capable to recognize antigens of serovars not present in the vaccine formulation. Transcripts of IFNγ, CXCL16, CCL5, CXCL10, CXCR6, and CCR5, increased in all immunized animals. Conclusion: Our results showed that bivalent vaccines with reduced LPS may be an interesting strategy for protection against heterologous virulent serovars. Besides the desirable multivalent protection, the low LPS vaccines are specially promising due to the expected lower reatogenicity., Competing Interests: The author(s) declare(s) that they have no competing interests.

Background: Leptospirosis is a widespread zoonosis caused by pathogenic prokaryotic microbes of the genus Leptospira. Although there are several reports in the literature, host-pathogen interaction is still poorly understood. The role of chemokine expression is important on the chemotaxis, activation and regulation of immune cells. Recent studies have shown that their expression profiles play an important role on the severity of leptospirosis outcome. We evaluated the phagocytosis of Leptospira by spleens cells from C3H/HeJ, C3H/HePas and BALB/c mouse strains, respectively susceptible, intermediate and resistant to leptospirosis, and by RAW 264.7 macrophages. Besides, we evaluated the effects of CCL2 treatment on the phagocytosis. The cells were incubated with or without CCL2 chemokine, and infected with virulent L. interrogans sv Copenhageni. Cells and culture supernatants were collected for subsequent analysis., Results: The number of leptospires was higher in BALB/c cells, CCL2 pre-treated or only infected groups, when compared to C3H/HeJ and C3H/HePas cells. Indeed, CCL2 activation did not interfere in the phagocytosis of Leptospira. Expression of chemokines CXCL5 and CCL8 levels were significantly inhibited in infected BALB/c cells when compared to the non-infected control., Conclusions: Higher ability to phagocytosis and early modulation of some chemokines correlated with the resistance to leptospirosis disease. Exposure to CCL2 did not interfere on phagocytosis of Leptospira in our experimental conditions, but acted in the modulation of chemokines expression during Leptospira infection.

Leptospirosis is globally widespread neglected disease, affecting most mammalian species. Clinical signs can be confused with other diseases which make the diagnosis and treatment difficult. Chemokines and cytokines are known for their role in the inflammatory and immune response to infections. The profile determination of chemokines' expressions in the course of infection may elucidate the defense mechanisms of the host and support the search for effective treatment strategies. We investigated the mechanisms of innate immunity through the comparison of chemokines induced during infection with L. interrogans in mice with different levels of susceptibility. We used lung and spleen tissues samples of mice from C3H/HeJ, C3H/HePas and Balb/c, respectively sensitive, intermediate susceptibility and resistant to the pathogen. The inoculation of L. interrogans in C3H/HeJ mice led a comparatively smaller change in chemokines expression in both spleen and lung tissues. In samples from spleens and lungs of C3H/HePas and Balb/c the higher increases occurred on CXCL9, CXCL16, CXCL5, CCL8 and CCL5 in Balb/c. Given the same genetic background, the differences in the responses of C3H/HePas compared to C3H/HeJ mice strongly suggest the role of chemokines for the survival of parental strain. Therefore, the greatest increase in CXC chemokines appears to be efficient to induce migration of cells to the secondary lymphoid organs and affected tissues, which is important to control infection. Overall, CXC chemokines are important for the activation and attraction of T cell and may influence the course and control of the infection in resistant Balb/c mice., (Copyright © 2017 Elsevier GmbH. All rights reserved.)

Leptospirosis is an emerging zoonosis with important economic and public health consequences and is caused by pathogenic leptospires. The genus Leptospira belongs to the order Spirochaetales and comprises saprophytic (L. biflexa), pathogenic (L. interrogans) and host-dependent (L. borgpetersenii) members. Here, we present an in silico search for DNA repair pathways in Leptospira spp. The relevance of such DNA repair pathways was assessed through the identification of mRNA levels of some genes during infection in animal model and after exposition to spleen cells. The search was performed by comparison of available Leptospira spp. genomes in public databases with known DNA repair-related genes. Leptospires exhibit some distinct and unexpected characteristics, for instance the existence of a redundant mechanism for repairing a chemically diverse spectrum of alkylated nucleobases, a new mutS-like gene and a new shorter version of uvrD. Leptospira spp. shares some characteristics from Gram-positive, as the presence of PcrA, two RecQ paralogs and two SSB proteins; the latter is considered a feature shared by naturally competent bacteria. We did not find a significant reduction in the number of DNA repair-related genes in both pathogenic and host-dependent species. Pathogenic leptospires were enriched for genes dedicated to base excision repair and non-homologous end joining. Their evolutionary history reveals a remarkable importance of lateral gene transfer events for the evolution of the genus. Up-regulation of specific DNA repair genes, including components of SOS regulon, during infection in animal model validates the critical role of DNA repair mechanisms for the complex interplay between host/pathogen.

The role of innate immune response in protection against leptospirosis is poorly understood. We examined the expression of the chemokine CXCL2/MIP-2 and the cytokine TNF-α in experimental resistant and susceptible mice models, C3H/HeJ, C3H/HePas and BALB/c strains, using a virulent strain of Leptospira interrogans serovar Copenhageni. Animals were infected intraperitoneally with 10(7) cells and the development of the disease was followed. Mortality of C3H/HeJ mice was observed whereas C3H/HePas presented jaundice and BALB/c mice remained asymptomatic. The infection was confirmed by the presence of leptospiral DNA in the organs of the animals, demonstrated by PCR. Sections of the organs were analyzed, after H&E stain. The relative expression of mRNA of chemokine CXCL2/MIP-2 and cytokine TNF-α was measured in lung, kidney and liver of the mice by qPCR. The concentrations of these proteins were measured in extracts of tissues and in serum of the animals, by ELISA. Increasing levels of transcripts and protein CXCL2/MIP-2 were detected since the first day of infection. The highest expression was observed at third day of infection in kidney, liver and lung of BALB/c mice. In C3H/HeJ the expression of CXCL2/MIP-2 was delayed, showing highest protein concentration in lung and kidney at the 5th day. Increasing in TNF-α transcripts were detected after infection, in kidney and liver of animals from the three mice strains. The expression of TNF-α protein in C3H/HeJ was also delayed, being detected in kidney and lung. Our data demonstrated that Leptospira infection stimulates early expression of CXCL2/MIP-2 and TNF-α in the resistant strain of mice. Histological analysis suggests that the expression of those molecules may be related to the influx of distinct immune cells and plays a role in the naturally acquired protective immunity., (Copyright © 2012 Elsevier Ltd. All rights reserved.)