Brazilian avian metapneumovirus subtypes A and B: experimental infection of broilers and evaluation of vaccine efficacy / Metapneumovirus aviário subtipos A e B brasileiros: infecção experimental em frangos de corte e eficácia vacinal

Avian metapneumovirus (aMPV) is a respiratory pathogen associated with the swollen head syndrome (SHS) in chickens. In Brazil, live aMPV vaccines are currently used, but subtypes A and, mainly subtype B (aMPV/A and aMPV/B) are still circulating. This study was conducted to characterize two Brazilian aMPV isolates (A and B subtypes) of chicken origin. A challenge trial to explore the replication ability of the Brazilian subtypes A and B in chickens was performed. Subsequently, virological protection provided from an aMPV/B vaccine against the same isolates was analyzed. Upon challenge experiment, it was shown by virus isolation and real time PCR that aMPV/B could be detected longer and in higher amounts than aMPV/A. For the protection study, 18 one-day-old chicks were vaccinated and challenged at 21 days of age. Using virus isolation and real time PCR, no aMPV/A was detected in the vaccinated chickens, whereas one vaccinated chicken challenged with the aMPV/B isolate was positive. The results showed that aMPV/B vaccine provided a complete heterologous virological protection, although homologous protection was not complete in one chicken. Although only one aMPV/B positive chicken was detected after homologous vaccination, replication in vaccinated animals might allow the emergence of escape mutants.

O Metapneumovírus aviário (aMPV) é um patógeno respiratório associado à síndrome da cabeça inchada (SHS) em galinhas. Apesar de vacinas vivas contra o aMPV serem utilizadas no Brasil, os subtipos A e B (aMPV/A e aMPV/B) são ainda encontrados no país, com predominância do subtipo B. Este estudo foi conduzido com o intuito de estudar dois isolados brasileiros de aMPV (subtipos A e B) isolados de frango. Para isto, um desafio experimental em frangos foi conduzido com o intuito de explorar a capacidade de replicação dos subtipos A e B Brasileiros. Posteriormente, a protecção virológica conferida por uma vacina do subtipo B em pintos foi realizada com os mesmos isolados. Após o desafio experimental demonstrou-se, por isolamento viral e PCR em tempo real, que o isolado do subtipo B replicou por maior período de tempo e em quantidades maiores, em comparação com o subtipo A. Para o estudo de proteção, 18 pintos de um dia de idade foram vacinados e desafiados aos 21 dias. Usando isolamento viral e PCR em tempo real, em nenhuma ave vacinada e desafiada com aMPV/A foi detectado o vírus, ao passo que uma ave vacinada e desafiada com o aMPV/B foi positiva. Os resultados mostraram que a vacina do subtipo B forneceu protecção heteróloga completa, embora a protecção homóloga não tenha sido conferida em uma ave. Apesar de o aMPV/B ter sido detectado em apenas um frango após vacinação homóloga, a replicação viral em aves vacinadas pode resultar em emergência de mutantes de escape.

Vacina experimental produzida em cultivo celular confere proteção parcial contra o ectima contagioso em ovinos / Experimental vaccine produced in tissue culture confers partial protection against contagious ecthyma in sheep

O ectima contagioso (também conhecido como orf), é uma doença debilitante de ovinos e caprinos causada pelo vírus do orf (ORFV). A vacinação tem sido usada com relativo sucesso no controle da doença. No entanto, as vacinas atuais contêm amostras virulentas do agente, são produzidas por escarificação cutânea de animais, e apresentam eficácia questionável. Assim, o presente trabalho teve como objetivo produzir e testar a eficácia de uma vacina experimental produzida em cultivo celular. A cepa IA-82 do ORFV foi submetida a 21 passagens em cultivo de células BHK-21 e usada para vacinar ovinos jovens (n=30), por escarificação cutânea na face interna da coxa. A vacinação produziu pústulas e crostas em 16 dos 30 ovinos vacinados, indicando imunização adequada. Noventa dias após a vacinação, ovinos vacinados (n=16) e controles (n=16) foram inoculados com uma cepa virulenta do ORFV (10(6,9)DICC50/mL) após escarificação na comissura labial. Todos os animais desenvolveram lesões típicas de ectima, incluindo hiperemia, vesículas, pústulas e crostas. No entanto, os animais vacinados desenvolveram lesões mais leves e passageiras do que os controles, e os escores clínicos foram estatisticamente diferentes (p<0,05) entre os dias 10 e 22 pós-desafio. Além disso, o tempo de duração da doença foi significativamente inferior (p<0,05) nos animais vacinados. Os animais vacinados também excretaram menor quantidade de vírus (p<0,05) e por um período significativamente mais curto do que os controles (13 dias versus 22 dias, p<0,001). Esses resultados demonstram a proteção parcial conferida pela vacina experimental e, dependendo da melhoria dos índices de imunização e proteção, são promissores no sentido da utilização de vacinas contra o ORFV produzidas em cultivo celular.

Contagious ecthyma, also known as orf, is a debilitating disease of sheep and goats caused by the parapoxvirus, orf virus (ORFV). Vaccination has been used with relative success to reduce the losses caused by the disease, yet the current vaccines contain virulent virus, are empirically produced through skin scarification of live lambs, and present questionable efficacy. Therefore, the present study aimed at developing and testing an experimental ORFV vaccine produced in tissue culture. The ORFV strain IA-82 was submitted to 21 passages in BHK-21 cells and then used to immunize lam bs (n=30) through skin scarification of the internal face of the hind limb. Vaccination produced localized pustules and scabs lesions in 16 out of 30 animals, indicating an adequate replication of the vaccine virus. Ninety days after vaccination, vaccinated (n=16) and control lambs (n=16) were inoculated with a virulent ORFV strain (10(6,9)TCID50/ml) in the labial commissure. Vaccinated and control lambs developed typical orf lesions, characterized by hyperemia, vesicles, pustules and scab formation. Nonetheless, vaccinated animals developed milder lesions compared to controls and the clinical scores were significantly lower (p<0.05) between days 10 and 22 post-challenge. In addition, the mean duration of clinical disease was significantly reduced in vaccinated animals (p<0.05). Furthermore, vaccinated animals excreted much less virus (p<0.05) and for a significantly shorter period of time than did the controls (13 days versus 22 days, p<0.001). These results demonstrate partial protection by the experimental vaccine and, upon improvement of immunization and protection indices, are promising towards the use of tissue culture-based ORFV vaccines.

Rhipicephalus (Boophilus) microplus: expression and characterization of Bm86-CG in Pichia pastoris / Rhipicephalus (Boophilus) microplus: expressão e caracterização da Bm86-CG em Pichia pastoris

The cattle tick Rhipicephalus (Boophilus) microplus is responsible for great economic losses. It is mainly controlled chemically, with limitations regarding development of resistance to the chemicals. Vaccines may help control this parasite, thereby reducing tick pesticide use. In this light, we performed subcloning of the gene of the protein Bm86-GC, the homologue protein that currently forms the basis of vaccines (GavacTM and TickGardPLUS) that have been developed against cattle ticks. The subcloning was done in the pPIC9 expression vector, for transformation in the yeast Pichia pastoris. This protein was characterized by expression of the recombinant Mut+ strain, which expressed greater quantities of protein. The expressed protein (rBm86-CG) was recognized in the Western-blot assay using anti-Gavac, anti-TickGard, anti-larval extract and anti-rBm86-CG polyclonal sera. The serum produced in cattle vaccinated with the antigen CG rBm86 presented high antibody titers and recognized the native protein. The rBm86-GC has potential relevance as an immunogen for vaccine formulation against cattle ticks.

O carrapato-do-boi Rhipicephalus (Boophilus) microplus é responsável por grandes perdas econômicas. Seu controle é principalmente químico e apresenta limitações quanto ao desenvolvimento de resistência aos princípios ativos. As vacinas podem auxiliar no controle deste parasita diminuindo as aplicações de carrapaticidas. Considerando isso, foi realizada a subclonagem do gene da proteína Bm86-CG, proteína homologa a que atualmente é a base das vacinas desenvolvidas (GavacTM e TickGardPLUS) contra o carrapato-do-boi, no vetor de expressão pPIC9, para ser transformado em levedura, Pichia pastoris. Esta proteína foi caracterizada pela expressão da cepa recombinante Mut+ que expressou maior quantidade de proteína. A proteína expressa, rBm86-CG, foi reconhecida no ensaio de Western-blot pelos soros policlonais anti-Gavac, anti-TickGard, anti-Extrato de larva e anti-rBm86-CG. O soro produzido em bovinos vacinados com o antígeno rBm86-CG apresentou altos títulos de anticorpo e reconheceu a proteína nativa. A rBm86-CG possui potencial relevância como imunógeno para formulação vacinal contra o carrapato de bovinos.

simple and cost-effective method for rapid purification of alkyl hydroperoxide reductase [AhpC] from helicobacterpylori and its antibody production

Helicobacter pylori express abundant amounts of AhpC enzyme that functions to reduce organic hydroperoxides [ROOH] into the corresponding non-toxic alcohols [ROH]. This conserved antigen has been earlier described as specific and unique for H. pylori and therefore, both H. pylori AhpC and Anti-AhpC could be useful in the development of serologic and stool antigen tests, to detecting and monitoring H. pylori infection. AhpC may also serves as a potential target for an antimicrobial agent or for vaccine development. The aim of this study was to simplify isolation and purification of the AhpC and production of a highly specific polyclonal antibody against it. In this paper a simple method was used for protein purification and antibody production which avoids both the long term AhpC protein purification procedure and the addition of Freund's adjuvant. One-dimensional preparative gel electrophoresis allows a single and short purification step and the high resolution capacity of this technique leads to a high level of purity of the protein and consequently to a very high specificity of the antibody. Moreover, it avoids contamination by other non-specific proteins which often appear during protein purification by column chromatographic techniques. The present method is simple, rapid and cost-effective and makes it possible to produce antibody for stool antigen enzyme immunoassay in short time and at low cost

Allelic diversity at the Merozoite surface protein-1 (MSP-1) locus in natural Plasmodium falciparum populations: a brief overview

The merozoite surface protein-1 (MSP-1) locus of Plasmodium falciparum codes for a major asexual blood-stage antigen currently proposed as a major malaria vaccine candidate. The protein, however, shows extensive polymorphism, which may compromise its use in sub-unit vaccines. Here we compare the patterns of allelic diversity at the MSP-1 locus in wild isolates from three epidemiologically distinct malaria-endemic areas: the hypoendemic southwestern Brazilian Amazon (n=54), the mesoendemic southern Vietnam (n=238) and the holoendemic northern Tanzania (n=79). Fragments of the variable blocks 2, 4a, 4b and 6 or 10 of this single-copy gene were amplified by the polymerase chain reaction, and 24 MSP-1 gene types were defined as unique combinations of allelic types in each variable block. Ten different MSP-1 types were identified in Brazil, 23 in Vietnam and 13 in Tanzania. The proportion of genetically mixed infections (isolates with carrying more one MSP-1 version) ranged from 39 per cent in Brazil to 44 per cent in Vietnam and 60 per cent in Tanzania. The vast majority (90 per cent) of the typed parasite populations from Brazil and Tanzania belonged to the same seven most frequent MSP-1 gene types. In contrast, these seven types corresponded to only 61 per cent of the typed parasite populations from Vietnam. Non-random associations were found between allelic types in blocks 4a and 6 among Vietnamese isolates, the same pattern being observed in independent studies performed in 1994, 1995 and 1996. These results suggest that MSP-1 is under selective pressure in the local parasite population. Nevertheless, the finding that similar MSP-1 type frequencies were found in 1994 and 1996 argues against the prominence of short-term frequency-dependent immune selection of MSP-1 polymorphisms. Non-random associations between MSP-1 allelic types, however, were not detected among isolates from Brazil and Tanzania. A preliminary analysis of the distribution od MSP-1 gene types per host among isolates from Tanzania, but not among those from Brazil and Vietnam, shows significant deviation from that expected under the null hypothesis of independent distribution of parasites carrying different gene types in the human hosts. Some epidemiological consequences of these findings are discussed.

Inactivation of rift valley fever virus and related viral antigenicity and immunogenicity

Rift Valley Fever virus Vaccine prepared using Binary Ethylen Imine [BEl] as a chemical inactivant was characterized than that prepared using Formalin which has been used for several decades for inactivation of both bacterial and viral antigens. Its inactivation efficacy was of somewhat shorter duration than that of Formalin as inactivant since RVFV infectivity titer was declined in order of 1.8 log [10] / hr post BEl treament and 1.6 log [10] post formalin treatment. The effective potency of BEl. inactivated vaccine was double that of formalin-treated one. This was evident from the dose that protected 50% [ED[50]] of infected mice which was 0.006 for the former and 0.011 for the latter concerning three types of antibodies [H.l. ab, S.N. ab., and PRN. ab.] these types showed about the same fluctuation during the time of the experiment [7 months] while its values were higher post Immunization with BEl inactivated vaccine and long durative than post Formalin inactivated vaccine immunization

Vacunación contra la shigelosis / Vaccination against shigelosis

Se define como shigelosis a la enfermedad intestinal producida por las diferentes especies del género Shigella, de las cuales el humano es el principal hospedero. Shigella es un bacilo corto, Gram-negativo, de la familia Enterobacteriaceae. La shigelosis se manifiesta en tres formas: 1) disentería clásica (sangre, moco, pus), 2) diarrea acuosa no complicada y 3) una combinación de disentería y diarrea acuosa. La mayoría de los casos de diarrea acuosa no son distinguibles de las que son ocacionadas por otras etiologías. Concluye el documento enfatizando que, no existe hasta el momento actual ninguna vacuna contra Shigella que pueda ser recomendable para la aplicación en población general. Todos los esfuerzos hasta ahora realizados han quedado en pequeños estudios en voluntarios, en los cuales se han obtenido fracasos y en otros ensayos se han vislumbrado posibles vacunas para emplear en el futuro. Dentro de los modelos experimentales de vacunas que hasta el momento hay, se está intentando corregir los posibles errores y por otra parte conjuntar los mecanismos de acción propuestos para cada tipo de vacuna. Finalmente si la shigelosis es un problema de salud pública, principalmente en los países en vías de desarrollo, son importantes los esfuerzos para lograr obtener una vacuna que en lo futuro pueda reducir uno de los principales problemas de morbilidad infantil

Nuevos enfoques en la obtención de vacunas / New approaches in the attainment of vaccines

Las llamadas vacunas de nueva generación incluyen a aquellas que no se preparan con un enfoque tradicionalista, es decir no usan al patógeno completo: virus, bacteria, protozoario, etc. atenuado o muerto. Su desarrollo conjunta información inmunológica y los avances en las técnicas de biología molecular. Con este enfoque, las nuevas vacunas sólo incluyen algunas moléculas (nativas o recombinantes), parte de éstas (péptidos sintéticos) o en su defecto, anticuerpos anti-idiotipo que mimetizan alguna estructura original en el patógeno. Entre los factores que han aumentado el interés para este enfoque, destaca la accesibilidad a las técnicas de biología molecular, que han permitido sobrepasar las limitaciones del enfoque tradicional. Prácticamente todas las vacunas que actualmente se emplean fueron desarrolladas antes del advenimiento de la biología molecular y aunque sólo se han podido obtener un número limitado de ellas, han significado un gran logro científico, que erradicó ya una enfermedad (viruela) y está en vías de hacer lo mismo con otras (tétanos, difteria, tosferina, poliomielitis, sarampión, etc.). No obstante, aún faltan muchas vacunas para prevenir un gran número de enfermedades infecciosas cuya trascendencia en la salud puede ser muy seria como lo ejemplifica el avance epidémico del Síndrome de Inmunodeficiencia Adquirida. Se abordan los diferentes énfoques que varios investigadores han empleado para el desarrollo de las nuevas vacunas