Prozone effects in microscopic agglutination tests for leptospirosis in the sera of mice infected with the pathogenic Leptospira interrogans serovar Canicola

Mice experimentally infected with a pathogenic strain of Leptospira interrogans serovar Canicola produced false negative results (prozone effect) in a microscopic agglutination test (MAT). This prozone effect occurred in several serum samples collected at different post-infection times, but it was more prominent in samples collected from seven-42 days post-infection and for 1:50 and 1:100 sample dilutions. This phenomenon was correlated with increased antibody titres in the early post-infection phase. While prozone effects are often observed in serological agglutination assays for the diagnosis of animal brucellosis and human syphilis, they are not widely reported in leptospirosis MATs.

Detection of reactive canines to Leptospira in Campeche City, Mexico / Detection of reactive canines to Leptospira in Campeche City, Mexico.

Leptospira reactivity in stray and household dogs in Campeche as well as associated risk factors to the seropositivity in household dogs have been herein determined. The survey included 323 dogs, 142 of which were stray dogs and 181 household dogs. Nine Leptospira interrogans serovars were tested by the microagglutination test. Reactivity was 21.3

corresponded to household dogs and 26.7

), and Leptospira Icterohaemorrhagiae (16.12

) were the most common serovars reacting against the serum of household animals, while Leptospira Canicola (15.78

), and Leptospira Pomona (7.89

) were those reacting in stray dogs. Results showed that all dogs have been in contact with different Leptospira serovars and outdoor exposure is the main infection risk factor.

Inmunogenicidad y capacidad protectora en hamsters de vacunas antileptospirósicas monovalentes de células enteras del serogrupo Ballum / Immunogenicity and protective capacity of leptospiral whole-cell monovalent serogroup Ballum vaccines in hamsters

El serogrupo Ballum de Leptospira constituye en la actualidad la primera causa de leptospirosis humana en Cuba. Vacunas de células enteras químicamente inactivadas fueron formuladas a partir de dos cepas clínicas de Leptospira interrogans serogrupo Ballum empleando como adyuvante hidróxido de aluminio. Los niveles de aglutininas inducidos en hamsters por una u otra preparación vacunal fueron estimados mediante aglutinación microscópica y la actividad IgG específica fue cuantificada mediante ELISA. La capacidad de protección homóloga y heteróloga contra la infección letal y subletal se determinó mediante el desafío con 100 y 10 000 DL50 de cinco cepas virulentas pertenecientes a los serogrupos Ballum, Canicola, Icterohaemorrhagiae y Pomona. Las evaluaciones realizadas demostraron que ambas vacunas fueron inmunogénicas e indujeron una completa protección homóloga en el modelo animal empleado. La protección cruzada frente a serogrupos heterólogos solo fue significativa en una de las preparaciones monovalentes frente al desafío con 100 DL50 de Canicola. Como resultado de este estudio se pudo comprobar la alta inmunogenicidad y capacidad protectora en hamsters de vacunas monovalentes de células enteras formuladas a partir de dos cepas candidatas vacunales del serogrupo de Leptospira de mayor circulación en humanos en Cuba no incluido en la vacuna actualmente disponible.

Leptospira serogroup Ballum is at present the first cause of human leptospirosis in Cuba. Killed whole-cell vaccines were formulated with two clinical isolates of Leptospira interrogans serogroup Ballum using aluminum hydroxide as adjuvant. Agglutinins levels induced by each vaccine in hamsters were estimated by microscopic agglutination test and specific IgG activities were quantified by a whole cell-based enzyme-linked immunosorbent assay. Homologous and cross protective capacity against lethal and sublethal infection were determined in vaccinated animals by challenge with 100 and 10 000 LD50 of five virulent strains belonging to serogroups Ballum, Canicola, Icterohaemorrhagiae and Pomona. Both monovalent serogroup Ballum vaccines were immunogenic and induced complete homologous protection in the animal model. Cross-protection was only significant in one of the two vaccines against challenge with 100 LD50 of serogroup Canicola. The results of this study demonstrate the high immunogenicity and protective capacity in hamsters of whole-cell monovalent vaccines formulated with two vaccine candidate strains belonging to the most prevalent serogroup of Leptospira in Cuba.

Reactogenicidad e inmunogenicidad de la primera vacuna cubana contra la leptospirosis humana

Se realizó un ensayo clínico controlado, a doble ciegas, con la participación de 80 voluntarios adultos, de los 2 sexos, sanos en apariencia, que fueron distribuidos de forma aleatoriamente en 2 grupos de 40 cada uno, se constituyó un grupo de estudio (que recibió la vacuna) y un grupo control (que recibió un placebo) para conocer la seguridad, el comportamiento de la reactogenicidad y comenzar los estudios de inmunogenicidad de la primera vacuna cubana contra la leptospirosis humana. La vacuna utilizada en el grupo de estudio fue una vacuna inactivada y trivalente en cuya composición se encuentran cepas de Leptospira canicola, icterohaemorrhagiae y pomona, por ser las de mayor circulación en el país. Los resultados obtenidos demostraron la inocuidad de la vacuna, al no presentarse reacciones adversas graves. La sintomatología general observada fue baja, la febrícula fue el síntoma general encontrado en mayor proporción. Aparece durante los primeros 3 d de observación, sin encontrarse diferencias significativas entre el grupo vacunado y el placebo. Como síntoma local sólo fue referido el dolor ligero en el sitio de la inyección, en el grupo vacunado se presentó con mayor frecuencia que en el grupo control (7,8 contra 1,5 %, respectivamente). La seroconversión obtenida fue de 29 % mediante la microaglutinación, y 34,2 % por la técnica de ELISA. Los resultados obtenidos permiten concluir que ésta es segura para adultos humanos en las edades comprendidas en el estudio y permiten continuar otros estudios es fases más avanzadas para completar los requerimientos para su licenciamiento.

A controlled double blind trial was conducted with the participation of 80 adult volunteers of both sexes, who were randomly divided into groups of 40 individuals each one. The case-base study received the vaccine and the control group was administered placebo to know the safety, the behaviour of reactogenecity, and to star the immunogenecity studies of the first Cuban vaccine against human leptospirosis. The vaccine used in the case-base study was an inactivated and trivalent vaccine containing strains of Leptospira canicola, incterohaemorrhagiae and pomona, since they have the highest circulation in the country. The results obtained showed the inocuity of the vaccine as no adverse severe reactions were detected. The general symptomatology observed was low, where as febricula was the most common general symptom. It appeared during the first 3 days of observation and there were no significant differences between the 2 group. Only a mild pain at the site of the injection was reported as a local symptom, which was more frequent in the vaccinated group than in the control group (7,8 against 1,5 %, respectively). The seroconversion obtained was of 29 % by microagglutination, and of 34,2 % by ELISA. The final results allowed to conclude that this vaccine is safe for human adults at the ages under study, and give the possibility to continue other studies in more advanced stages to complete the requierements for obtaining its license.

Immunological properties of cellular and whole-culture leptospiral bacterins

Two bivalent leptospiral bacterins were compared for safety in guinea pigs and for potency in hamsters. One bacterin [Bacterin A] was prepared from the cellular material of Leptospiral icterohaemorrhagjae and Leptospira canicola cultures propagated in Stuart's modified medium with 7% rabbit serum. The 2[nd] bacterin [Bacterin B] contained whole leptospiral cultures grown in synthetic medium. Neither bacterin induced adverse local or systemic reactions when injected intraperitoneally [I/P] in guinea pigs. In hamsters, 1/400 and 1/800 of the recommended dose of bacterin B for cattle protected 100% of the vaccinated hamsters against challenge exposure of either virulent leptospiral serotype A dose representing 1/400 of the recommended dose of bacterin A for cattle protected 80% of vaccinated hamsters against challenge exposure to L. icterohaemorrhagjae and 90% against challenge exposure to L. canicola, whereas the 1/800 dose level protected only 10% of the vaccinated hamsters challenge exposed to virulent culture of L. icterohaemorrhagjae or canicola. The Possibility was demonstrated that at least one soluble antigen of strong immunogenic properties is produced in cultures of L. icterohaemorrhagjae and L. canicola

Comprometimento pulmonar na leptospirose / Pulmonary compromise in leptospirosis

Em 23 pacientes com leptospirose apresentando comprometimento pulmonar, internados no Hospital Universitário Antônio Pedro da UFF, Niterói, hemoptise e hemoptóicos foram observados em 21.7 por cento e 30, 4 por cento, respectivamente. Gasometria arterial revelou hipoxemia e hipocapnia na maioria dos casos. Radiografia de tórax em 15 pacientes mostrou comprometimento alveolar em 60 por cento, comprometimento intersticial-reticular em 6 por cento, padräo misto (alveolar e intersticial) em 20 por cento e ausências de alteraçöes radiológicas em 14 por cento. A necrópsia de 13 pacientes mostrou edema, congestäo e hemorragia nos pulmöes em 100 por cento dos casos. A hemorragia foi focal em 46 por cento e difusa em 54 por cento dos casos. Houve formaçäo de membrana hialina em 30 por cento e trombos de fibrina em 46 por cento dos pulmöes estudados, o que estabelece o diagnóstico da coagulaçäo intravascular e a ocorrência da síndrome de angústia respiratória na leptospirose