Leptospirosis is a zoonosis of multisystem involvement caused by pathogenic strains of the genus Leptospira.In the last few years, intensive studies aimed at the development of a vaccine have provided important knowledge about the nature of the immunological mechanisms of the host. The purpose of this study was to analyze the immune responses to two recombinant proteins, MPL17 and MPL21 (encoded by the genes LIC10765 and LIC13131, respectively) of Leptospira interrogans serovar Copenhageni in individuals during infection. The recombinant proteins were expressed in Escherichia coli as six-His tag fusion proteins and were purified from the soluble bacterial fraction by affinity chromatography with Ni 2؉ -charged resin. The recombinant proteins were used to evaluate their ability to bind to immunoglobulin G (IgG) (and IgG subclass) or IgM antibodies in serum samples from patients in the early and convalescent phases of leptospirosis (n ‫؍‬ 52) by enzyme-linked immunosorbent assays. The prevalences of total IgG antibodies against MPL17 and MPL21 were 38.5% and 21.2%, respectively. The titers achieved with MPL17 were statistically significantly higher than those obtained by the reference microscopic agglutination test. The specificity of the assay was estimated to be 95.5% for MPL17 and 80.6% for MPL21 when serum samples from individuals with unrelated febrile diseases and control healthy donors were tested. The proteins are conserved among Leptospira strains that cause human and animal diseases. MPL17 and MPL21 are most likely new surface proteins of leptospires, as revealed by liquid-phase immunofluorescence assays with living organisms. Our results demonstrate that these recombinant proteins are highly immunogenic and, when they are used together, might be useful as a means of diagnosing leptospirosis.

A collection of 101 Leptospira isolates was tested by multilocus sequence typing (MLST) and by traditional serotyping. MLST divided the isolates into 4 sequence types (STs), while serotyping classified them into 6 serogroups. Two isolates failed to generate products for some genes by MLST. MLST was less discriminatory than serotyping for uncommonly occurring isolates from humans in Brazil.Leptospirosis, caused by pathogenic leptospires, is one of the most widespread zoonotic diseases known. The genus Leptospira is divided into 20 species with more than 200 pathogenic serovars organized into 24 serogroups on the basis of antigenic relatedness (2,9,13,30). The disease occurs in wild and domesticated animals, both of which can be a source of human infection. Exposures that occur during flooding events are the main risk factors of human leptospirosis in Brazil (1,3,14,22). In São Paulo State, Brazil, 13,620 cases have been reported in the last 20 years (ftp://ftp.cve.saude.sp.gov.br/doc_tec/zoo /lepto09_perfil.pdf). However, information about circulating isolates of Leptospira spp. in Brazil is limited. Identification of isolates to the serovar level is essential for understanding the epidemiology of the disease in both humans and animals.Since certain serovars are often associated with specific mammalian hosts and with the symptoms and severity of the disease, the identification of the serovar usually permits the prediction of sources of infection, thereby enabling control of the spread of the disease (17). Monitoring the serovars and genetic profiles of strains collected over time and from different regions is also important to better understand the current circulating Leptospira population worldwide. Isolate discrimination can be performed by a microagglutination test (MAT) at the serogroup level and by a cross-agglutinin absorption test (CAAT) at the serovar level (5). However, performing those methods is tedious, as live cultures of collection strains must be maintained for use as antigens and rabbit hyperimmune sera are required. Although identification by serotyping is valuable, molecular methods with higher reproducibility and discriminatory power may be more useful in epidemiological investigations.New molecular methods such as multilocus sequence typing (MLST) have been recently developed and applied to the study of many bacterial species (4,6,7,15,18). MLST is a simple PCR-based technique that makes use of automated DNA sequencers to assign and characterize the alleles present in different target genes. The method allows one to generate sequence data on a low-to high-throughput scale that is unambiguous and suitable for epidemiological and population studies. The selected loci are generally housekeeping genes, which evolve very slowly over an evolutionary time scale (8).Our goal was to evaluate the discriminatory power of MLST compared to serotyping using a set of Brazilian human isolates. A total of 101 Leptospira clinical strains (95 from blood, 5 from cerebrospinal fluid, and 1 from urine) isolated fro...

Leptospirosis is a zoonotic infection caused by pathogenic members of the genus Leptospira spp. Knowledge of the prevalent serovars and their maintenance hosts is essential to understand the disease. The aim of this study was to evaluate the ability of serology by the microscopic agglutination test (MAT) to predict the serogroups compared with results of identification of leptospires in São Paulo, Brazil. MAT correctly assigned the serogroup of the infecting isolate in 49/52 cases (94.23%). The serogroup Icterohaemorrhagiae was the predominant serogroup (88.46%). This study showed the usefulness of the MAT to correctly identify the infecting serogroup with a good overall agreement between the serologically-identified infecting serogroup and by identification of the isolate and can be used in epidemiological surveys in São Paulo. However, it should be complemented by the identification of Leptospira isolates.