Samuel Rodrigues Felix

Recombinant vaccines against Leptospirosis

Leptospirosis is an important neglected infectious disease that occurs in urban environments, as well as in rural regions worldwide. Rodents, the principal reservoir hosts of pathogenic Leptospira spp., and other infected animals shed the bacteria in their urine. During occupational or even recreational activities, humans that come into direct contact with infected animals or with a contaminated environment, particularly water, are at risk of infection. Prevention of urban leptospirosis is largely dependent on sanitation measures that are often difficult to implement, especially in developing countries. Vaccination with inactivated whole-cell preparations (bacterins) has limited efficacy due to the wide antigenic variation of the pathogen. Intensive efforts towards developing improved recombinant vaccines are ongoing. During the last decade, many reports on the evaluation of recombinant vaccines have been published. Partial success has been obtained with some surface-exposed protein antigens. The combination of protective antigens and new adjuvants or delivery systems may result in the much-needed effective vaccine.

Protection against lethal leptospirosis after vaccination with LipL32 coupled or coadministered with the B subunit of Escherichia coli heat-labile enterotoxin.

ABSTRACT Leptospirosis, a worldwide zoonosis, lacks an effective, safe, and cross-protective vaccine. LipL32, the most abundant, immunogenic, and conserved surface lipoprotein present in all pathogenic species of Leptospira, is a promising antigen candidate for a recombinant vaccine. However, several studies have reported a lack of protection when this protein is used as a subunit vaccine. In an attempt to enhance the immune response, we used LipL32 coupled to or coadministered with the B subunit of the Escherichia coli heat-labile enterotoxin (LTB) in a hamster model of leptospirosis. After homologous challenge with 5× the 50% lethal dose (LD50) of Leptospira interrogans, animals vaccinated with LipL32 coadministered with LTB and LTB::LipL32 had significantly higher survival rates (P < 0.05) than animals from the control group. This is the first report of a protective immune response afforded by a subunit vaccine using LipL32 and represents an important contribution toward the development of improved leptospirosis vaccines.

Subunit Approach to Evaluation of the Immune Protective Potential of Leptospiral Antigens

ABSTRACT Leptospirosis is the most widespread zoonosis in the world. Current vaccines are based on whole-cell preparations that cause severe side effects and do not induce satisfactory immunity. In light of the leptospiral genome sequences recently made available, several studies aimed at identification of protective recombinant immunogens have been performed; however, few such immunogens have been identified. The aim of this study was to evaluate 27 recombinant antigens to determine their potential to induce an immune response protective against leptospirosis in the hamster model. Experiments were conducted with groups of female hamsters immunized with individual antigen preparations. Hamsters were then challenged with a lethal dose of Leptospira interrogans. Thirteen antigens induced protective immune responses; however, only recombinant proteins LIC10325 and LIC13059 induced significant protection against mortality. These results have important implications for the development of an efficacious recombinant subunit vaccine against leptospirosis.

LigB subunit vaccine confers sterile immunity against challenge in the hamster model of leptospirosis

Neglected tropical diseases, including zoonoses such as leptospirosis, have a major impact on rural and poor urban communities, particularly in developing countries. This has led to major investment in antipoverty vaccines that focus on diseases that influence public health and thereby productivity. While the true, global, impact of leptospirosis is unknown due to the lack of adequate laboratory diagnosis, the WHO estimates that incidence has doubled over the last 15 years to over 1 million cases that require hospitalization every year. Leptospirosis is caused by pathogenic Leptospira spp. and is spread through direct contact with infected animals, their urine or contaminated water and soil. Inactivated leptospirosis vaccines, or bacterins, are approved in only a handful of countries due to the lack of heterologous protection (there are > 250 pathogenic Leptospira serovars) and the serious side-effects associated with vaccination. Currently, research has focused on recombinant vaccines, a possible solution to these problems. However, due to a lack of standardised animal models, rigorous statistical analysis and poor reproducibility, this approach has met with limited success. We evaluated a subunit vaccine preparation, based on a conserved region of the leptospiral immunoglobulin-like B protein (LigB(131–645)) and aluminium hydroxide (AH), in the hamster model of leptospirosis. The vaccine conferred significant protection (80.0–100%, P < 0.05) against mortality in vaccinated animals in seven independent experiments. The efficacy of the LigB(131–645)/AH vaccine ranged from 87.5–100% and we observed sterile immunity (87.5–100%) among the vaccinated survivors. Significant levels of IgM and IgG were induced among vaccinated animals, although they did not correlate with immunity. A mixed IgG1/IgG2 subclass profile was associated with the subunit vaccine, compared to the predominant IgG2 profile seen in bacterin vaccinated hamsters. These findings suggest that LigB(131–645) is a vaccine candidate against leptospirosis with potential ramifications to public and veterinary health.

Preliminary Characterization of Mus musculus–Derived Pathogenic Strains of Leptospira borgpetersenii Serogroup Ballum in a Hamster Model

Human and animal leptospirosis caused by Leptospira spp. belonging to serogroup Ballum has increased worldwide in the past decade. We report the isolation and serologic and molecular characterization of four L. borgpetersenii serogroup Ballum isolates obtained from Mus musculus, and preliminary virulence studies. These isolates are useful for diagnosis of leptospirosis and for epidemiologic studies of its virulence and pathogenic mechanisms.

Comparison of systemic interleukin 10 concentrations in healthy dogs and those suffering from recurring and first time Demodex canis infestations.

OBJECTIVE The objective of this study was to assess the interleukin 10 (IL-10) concentrations in the sera of dogs suffering from demodicosis. METHODS Twenty-six dogs were distributed into three groups: demodicosis groups G1, n=11 (recurring disease) and G2, n=6 (first time occurrence), and a control group, G3, n=9 (healthy dogs). All the animals were subjected to skin scrape tests and blood harvesting for serum extraction. In G1 and G2 only those animals with Demodex canis positive skin tests were included, while healthy dogs were included in G3. To assess IL-10 levels the commercial Quantikine Canine IL-10 Immunoassay(®) (R&D Systems) kit was used. RESULTS The mean IL-10 level obtained for G1 was 269.4 pg/ml (sd=290.8 pg/ml), for G2 it was 28.5 pg/ml (sd=19.7 pg/ml) while the mean for G3 was 11.9 pg/ml (sd=2.3 pg/ml). There was a significant difference between G1 and the other two groups. CONCLUSIONS According to our results, dogs with reoccurring demodicosis have higher IL-10 levels than healthy dogs and those suffering the disease for the first time.

Infection with Leptospira kirschneri Serovar Mozdok: First Report from the Southern Hemisphere.

Leptospirosis is a global zoonosis caused by pathogenic Leptospira spp. In this study, we characterized two Leptospira kirschneri serogroup Pomona serovar Mozdok isolates, one obtained from a dog and the other from a patient with severe leptospirosis, 4 years later. Histopathological analysis showed that both isolates caused severe tissue damage when used to infect hamsters. While L. kirschneri serogroup Pomona serovar Mozdok is endemic in animals in Europe, there is only one report of human leptospirosis in the literature. Although strains belonging to L. kirschneri serogroup Pomona have been identified in cases of human leptospirosis in Europe, serovar Mozdok has not yet been implicated. The 4-year interval between isolations and the fact that this is the first report of serovar Mozdok as the causative agent of human leptospirosis in the southern hemisphere, demonstrates its epidemiological importance to public health. Moreover, the presence of serovar Mozdok in Brazil has the potential to affect vaccine and diagnostic test development.

Highly Virulent Leptospira borgpetersenii Strain Characterized in the Hamster Model

Abstract. A recent study by our group reported the isolation and partial serological and molecular characterization of four Leptospira borgpetersenii serogroup Ballum strains. Here, we reproduced experimental leptospirosis in golden Syrian hamsters (Mesocricetus auratus) and carried out standardization of lethal dose 50% (LD50) of one of these strains (4E). Clinical disease features and histopathologic analyses of tissue lesions were also observed. As results, strain 4E induced lethality in the hamster model with inocula lower than 10 leptospires, and histopathological examination of animals showed typical lesions found in severe leptospirosis. Gross pathological findings were peculiar; animals that died early had more chance of presenting severe jaundice and less chance of presenting pulmonary hemorrhages (P < 0.01). L. borgpetersenii serogroup Ballum has had a considerable growth in human leptospirosis cases in recent years. This strain has now been thoroughly characterized and can be used in more studies, especially evaluations of vaccine candidates.

Presence of Gasterophilus (Leach, 1817) (Díptera: Oestridae) in horses in Rio Grande do Sul State, Brazil

ABSTRACT With the purpose of verify the presence of larvae from the genus Gasterophilus in the Rio Grandedo Sul State, a study was undertaken using 395 horses taken to slaughter in the city of Pelotas. Thematerial analysis revealed that 126 animals (31,90%) presented infection, with 100 animals (25,32%)infected by Gasterophilus nasalis , and 47 animals (11,90%) infected by G . intestinalis . These resultsalso represent the first report of the definite establishment of G. intestinalis as a horse parasite inBrazil. The probable implications of G. intestinalis occurrence in Brazil are discussed. Key words: Gasterophilus; G. nasalis; G. intestinalis. * Laboratorio de Doencas Parasitarias da Faculdade de Veterinaria, UFPel, Pelotas, Brasil.** Setor de Parasitologia, Departamento de Microbiologia, Instituto de Ciencias Basicas da Saude, UFRGS, PortoAlegre, Brasil. INTRODUCTIONThe genus Gasterophilus (Diptera, Oestridae)includes eight species of flies whose larvae causegastrointestinal myiasis in equids

Frequency of seropositive equines for Theileria equi in the Southern Rio Grande do Sul State, Brazil

ABSTRACT A study on equine theileriosis was carried out in the southern region of the Brazilian state of RioGrande do Sul (RS). Blood samples were collected from 113 mares from an equine breeding farmlocated in the city of Bage, latitude 31o30’ S and a longitude of 54U10’ W. The serological testing wascarried out with the use of indirect fluorescence test (IFAT) and compared with Nested PolimeraseChain Reaction (nPCR). Among the sera collected from 118 horses, 25 were found positive to Theileria equi by the IFAT, while by nPCR 17 positive for T. equi was observed, corresponding to afrequency of 22.1% and 15.0%, respectively. The racial analysis showed 15.05% (14) thoroughbredand 55% (11) Crioulo breed horses to be positive by IFAT. Key words: Theileria equi, IFAT, prevalence. INTRODUCTIONEquine piroplasmosis, caused by Theileriaequi and Babesia caballi , is considered to be themost important tick-borne disease of horse intropical and subtropical areas 1 . Clinicalmanifestation of the disease is variable includingfever, anemia, icterus, lethargy, and in somecases death