Respuesta inmune y alergia a vacunas / Immune response and allergies to vaccines

Las vacunas son altamente efectivas en prevenir enfermedades infecciosas a través del desarrollo en el individuo de una respuesta inmune protectora, sin desarrollar la enfermedad. Los distintos tipos de vacunas producen diferentes tipos de respuestas inmunes y variadas estrategias se han desarrollado para mejorar esta respuesta. El sistema inmune sufre cambios con la edad y esta inmunosenecencia altera la capacidad de responder frente a ellas. Por otro lado, si bien el sistema inmune puede reconocer elementos presentes en las vacunas y montar respuestas de hipersensibilidad ante ellos, las alergias a las vacunas son raras, teniendo que distinguirlas adecuadamente de otro tipo de reacciones. En caso que un paciente presente una reacción compatible con alergia, es importante conocer todos los componentes de la vacuna para realizar un estudio adecuado.

Vaccines are highly effective in preventing infectious diseases through the development in the individual a protective immune response, without developing the disease. Different types of vaccines produce different types of immune responses, and varied strategies have been developed to improve this response. The immune system undergoes changes with age, and this inmunosenescence alters the ability to respond to them. On the other hand, although the immune system can recognize elements present in vaccines and establish hypersensitivity responses to them, vaccine allergies are rare, having to properly distinguish them from other types of reactions. In the event that a patient has an allergy-compatible reaction, it is important to know all the components of the vaccine to conduct a proper study.

Genómica de rotavirus. Impacto en salud pública / Rotavirus genomics. Public health impact

Resumen: Con la introducción de las vacunas de rotavirus Rotarix (RV1) o RotaTeq (RV5) en programas nacionales de vacunación de diversos países, surgió la preocupación de que la presión inmune generada condujera al aumento en la prevalencia de genotipos virales no incluidos en las vacunas, o bien del surgimiento de nuevas cepas que pudieran escapar a la respuesta inmune protectora inducida por la vacunación. La variación natural de los rotavirus ha hecho que sea muy difícil distinguir si el cambio en las cepas circulantes se debe a la presión selectiva impuesta por las vacunas o bien a la fluctuación natural de las cepas. Si acaso ha habido una presión selectiva, ésta ha sido hasta ahora baja. Sin embargo, es importante mantener la vigilancia epidemiólogica y poner atención al surgimiento de cepas resistentes a la inmunidad, en particular en países en desarrollo en los que se ha descrito una mayor diversidad viral.

Abstract: With the introduction of rotavirus vaccines Rotarix (RV1) or RotaTeq (RV5) in the immunization programs of an increasing number of countries, there is concern that the immune selection pressure induced will cause an increase in the prevalence of virus genotypes not included in the vaccine formulation, or to the appearance of novel rotavirus strains that could evade the protective immune response. The natural fluctuation of rotaviruses makes it difficult to distinguish if the change in the circulating strains is due to the vaccine selective pressure or to the natural diversity fluctuation of viruses. If there has been a selective pressure, it has been low so far. However, it is important to keep an epidemiological surveillance and pay attention to the emergence of strains that are resistant to the vaccine, in particular in those countries where the viral diversity has been shown to be higher.

Estabilidad de la vacuna Candid#1 para prevenir la fiebre hemorrágica Argentina / Stability of Candid#1 vaccine to prevent Argentine Hemorrhagic Fever

Candid#1 es la primera vacuna a virus vivo atenuado producida y registrada en Argentina. Se produce en el INEVH desde 2003 para prevenir la fiebre hemorrágica argentina y se obtiene mediante cosecha de sobrenadantes de cultivos de células diploides infectadas con una cepa atenuada del virus Junín, formulación y posterior liofilización. Su estabilidad es crucial para asegurar su efectividad. El objetivo de este trabajo fue evaluar la estabilidad de Candid#1 exponiéndola a distintas condiciones de temperatura y tiempo. Tres lotes producidos en 2003 fueron sometidos al siguiente esquema de almacenamiento: (a) vacuna reconstituida conservada entre 2 °C y 8 °C durante 8 días, (b) vacuna liofilizada conservada entre 2 °C y 8 °C durante 6 meses, y (c) vacuna liofilizada conservada entre -18 °C y -20 °C durante 10 años. La potencia fue evaluada en monocapa de células Vero bajo agar. Los resultados fueron: (a) Candid#1 reconstituida fue estable 8 días entre 2 °C y 8 °C, (b) Candid#1 liofilizada fue estable 2 meses entre 2 °C y 8 °C y (c) Candid#1 liofilizada fue estable 9 años entre -18 °C y -20 °C manteniendo todos sus atributos. Estos resultados permitieron establecer las siguientes condiciones de almacenamiento: reconstituida 12 horas entre 2 °C y 8 °C, liofilizada 30 días entre 2 °C y 8 °C y 9 años entre -18 °C y -20 °C. A la luz de estos resultados, se generaron cambios favorables en las condiciones de transporte, almacenamiento y distribución de la vacuna. Se implementó la instalación de freezers domésticos en centros estratégicamente distribuidos, permitiendo preservar stocks de vacuna y distribuir las dosis necesarias a vacunatorios.

Candid#1 is the first live attenuated vaccine produced and registered in Argentina. Produced since 2003 at the INEVH to prevent Argentine hemorrhagic fever, it is obtained by harvesting supernatants of diploid cells infected with an attenuated strain of Junin virus and subsequent lyophilization. The stability of this vaccine is crucial to ensure its effectiveness. This study was aimed to evaluate the stability of Candid#1 by exposing it to different time and temperature conditions. Three vaccine batches produced in 2003 were analysed according to the following storage scheme: (a) reconstituted vaccine at 2 °C to 8°C for 8 days; (b) lyophilized vaccine at 2 °C to 8 °C for 6 months; (c) lyophilized vaccine at -18 °C to -20 °C for 10 years. The potency was assessed in Vero cell monolayers under agar. The results were: (a) reconstituted vaccine was stable between 2 °C and 8 °C for 8 days, (b) lyophilized vaccine was stable between 2 °C and 8 °C for 2 months, and (c) lyophilized vaccine was stable 9 years between -18 °C and -20 °C, keeping all its properties. These results allowed us to establish the following storage conditions and expiration times for Candid#1: (a) reconstituted: 12 hours between 2 °C and 8 °C, (b) lyophilized: 30 days between 2 °C and 8 °C and (c) lyophilized: 9 years between -18 °C and -20 °C. Based on our results, favorable changes were made in the conditions of transport, storage and distribution of the vaccine. Domestic freezers in strategically located centers were installed, allowing the preservation of vaccine stocks for distribution to secondary vaccination centers.

Assessment of the pathogenicity of cell-culture-adapted Newcastle disease virus strain Komarov

Newcastle disease vaccines hitherto in vogue are produced from embryonated chicken eggs. Egg-adapted mesogenic vaccines possess several drawbacks such as paralysis and mortality in 2-week-old chicks and reduced egg production in the egg-laying flock. Owing to these possible drawbacks, we attempted to reduce the vaccine virulence for safe vaccination by adapting the virus in a chicken embryo fibroblast cell culture (CEFCC) system. Eighteen passages were carried out by CEFCC, and the pathogenicity was assessed on the basis of the mean death time, intracerebral pathogenicity index, and intravenous pathogenicity index, at equal passage intervals. Although the reduction in virulence demonstrated with increasing passage levels in CEFCC was encouraging, 20% of the 2-week-old birds showed paralytic symptoms with the virus vaccine from the 18^th(final) passage. Thus, a tissue-culture-adapted vaccine would demand a few more passages by CEFCC in order to achieve a complete reduction in virulence for use as a safe and effective vaccine, especially among younger chicks. Moreover, it can be safely administered even to unprimed 8-week-old birds.

Therapy with radio-attenuated vaccine in experimental murine visceral leishmaniasis showed enhanced T cell and inducible nitric oxide synthase levels, suppressed tumor growth factor-beta production with higher expression of some signaling molecules

Background: Visceral leishmaniasis (VL) or Kala-Azar (KA) is one of the most deadly forms of disease among all neglected tropical diseases. There are no satisfactory drugs or vaccine candidates available for this dreaded disease. Our previous studies showed promising therapeutic and prophylactic efficacy of the live, radio-attenuated parasites through intramuscular (I.M.) and intraperitoneal (I.P.) route in BALB/c mice model. Methods: The T-cell proliferation level, the mRNA expression level of inducible nitric oxide synthase (iNOS) and tumor growth factor-beta (TGF-β) genes and finally the phosphorylation levels of phosphoinositide dependent kinase 1 (PDK1), phosphoinositide 3 kinase (PI3K) and p38 mitogen activated protein kinase (p38MAPK) molecules were checked in BALB/c mice model immunized with radio-attenuated Leishmania donovani parasites through I.M. route. Results: Higher T-cell proliferation, increased iNOS level, and suppressed TGF-β level were found in treated infected animal groups (100 and 150 Gy) in relation to untreated infected animals. Likewise, phosphorylation levels of PDK1, PI3K and p38MAPK of these two groups were increased when compared to untreated infected controls. Conclusion: The clearance of the parasites from treated infected groups of animals may be mediated by the restoration of T-cell due to therapy with radio-attenuated L. donovani parasites. The killing of parasites was mediated by increase in nitric oxide release through PDK1, PI3K and p38MAPK signaling pathways. A lower TGF-β expression has augmented the restored Th1 ambience in the 100 and 150 Gy treated animal groups proving further the efficacy of the candidate vaccine. .

Detection of Rotavirus Genotypes in Korea 5 Years after the Introduction of Rotavirus Vaccines

Rotavirus (RV) is one of the most important viral etiologic agents of acute gastroenteritis (AGE) in children. Although effective RV vaccines (RVVs) are now used worldwide, novel genotypes and outbreaks resulting from rare genotype combinations have emerged. This study documented RV genotypes in a Korean population of children with AGE 5 yr after the introduction of RVV and assessed potential genotype differences based on vaccination status or vaccine type. Children less than 5-yr-old diagnosed with AGE between October 2012 and September 2013 admitted to 9 medical institutions from 8 provinces in Korea were prospectively enrolled. Stool samples were tested for RV by enzyme immunoassay and genotyped by multiplex reverse-transcription polymerase chain reaction. In 346 patients, 114 (32.9%) were RV-positive. Among them, 87 (76.3%) patients were infected with RV alone. Eighty-six of 114 RV-positive stool samples were successfully genotyped, and their combinations of genotypes were G1P[8] (36, 41.9%), G2P[4] (12, 14.0%), and G3P[8] (6, 7.0%). RV was detected in 27.8% of patients in the vaccinated group and 39.8% in the unvaccinated group (P=0.035). Vaccination history was available for 67 of 86 cases with successfully genotyped RV-positive stool samples; RotaTeq (20, 29.9%), Rotarix (7, 10.4%), unvaccinated (40, 59.7%). The incidence of RV AGE is lower in the RV-vaccinated group compared to the unvaccinated group with no evidence of substitution with unusual genotype combinations.

The Immunogenicity and Safety of the Live-attenuated SA 14-14-2 Japanese Encephalitis Vaccine Given with a Two-dose Primary Schedule in Children

Effective and tolerable vaccination is an essential strategy to prevent Japanese encephalitis (JE) in endemic areas. Although the live attenuated SA 14-14-2 JE vaccine (LAJEV) has been widely used since its introduction, the systemic data of LAJEV was very rarely available in Korea. We conducted the open-label, prospective cohort study to assess the immunogenicity and safety of this vaccine. Ninety subjects were enrolled, and LAJEV in a 2-dose primary series was given with a 12-month interval. Neutralizing antibody titers were measured before and after each vaccination, and active monitoring for adverse events was performed. After the first dose, 91.1% of subjects had seroprotection with a geometric mean titer (GMT) of 40.9. Seroprotection rate after the second dose was 97%, and GMT showed an increase of 6.5-fold. Most adverse events following immunization were self-limited, and no serious adverse events were reported until 42 days after each dose. The 2-dose administration of LAJEV in the primary immunization schedule appeared to be highly immunogenic and safe.

Live bacterial vaccine vectors: An overview

Genetically attenuated microorganisms, pathogens, and some commensal bacteria can be engineered to deliver recombinant heterologous antigens to stimulate the host immune system, while still offering good levels of safety. A key feature of these live vectors is their capacity to stimulate mucosal as well as humoral and/or cellular systemic immunity. This enables the use of different forms of vaccination to prevent pathogen colonization of mucosal tissues, the front door for many infectious agents. Furthermore, delivery of DNA vaccines and immune system stimulatory molecules, such as cytokines, can be achieved using these special carriers, whose adjuvant properties and, sometimes, invasive capacities enhance the immune response. More recently, the unique features and versatility of these vectors have also been exploited to develop anti-cancer vaccines, where tumor-associated antigens, cytokines, and DNA or RNA molecules are delivered. Different strategies and genetic tools are constantly being developed, increasing the antigenic potential of agents delivered by these systems, opening fresh perspectives for the deployment of vehicles for new purposes. Here we summarize the main characteristics of the different types of live bacterial vectors and discuss new applications of these delivery systems in the field of vaccinology.

Marcadores fenotípicos de atenuación en cepas de virus Junín recuperadas de individuos vacunados con la cepa Junín Candid#1 / Phenotypic markers of attenuation in Junin virus strains recently isolated from individuals vaccinated with Junin Candid#1 strain

La Fiebre Hemorrágica Argentina es una enfermedad producida por el virus Junín. Para la prevención de esta enfermedad se obtuvo una vacuna efectiva denominada Candid#1. Durante un ensayo clínico realizado en el INEVH, dos cepas de virus Junín fueron aisladas de sangre periférica de dos voluntarios mediante co-cultivo de células mononucleares. El objetivo de este trabajo fue comparar las características fenotípicas de atenuación de esas dos cepas recuperadas de humanos con las de la vacuna Candid#1 utilizando los indicadores de atenuación desarrollados por Contigiani y Sabattini en 1977. A tal fin se midieron los índices de letalidad, infección y protección en cobayos y ratones de diferentes edades. Las tres cepas investigadas resultaron letales para ratones recién nacidos pero no para ratones de 10 a 12 días, ratones adultos ni cobayos, aun a la más baja dilución inoculada. Los cobayos inoculados con las cepas recuperadas de humanos y con la cepa Candid#1 no presentaron síntomas de enfermedad y mostraron estar protegidos cuando fueron desafiados con una cepa patógena. Los índices de infección y de protección hallados indican que estas cepas poseen elevada capacidad infectante y protectora en las especies animales aquí estudiadas. Estos resultados demuestran que las cepas de virus Junín aisladas de voluntarios inmunizados con Candid#1 mantienen el mismo fenotipo atenuado de la vacuna Candid#1 después de un pasaje por humanos.

Argentine hemorrhagic fever is a severe acute disease caused by Junin virus. For prevention of this disease an effective vaccine called Candid#1 has been developed, composed of a live attenuated Junin virus strain. During a clinical trial conducted at Instituto Nacional de Enfermedades Virales Humanas (INEVH) in 2005, Junin virus was isolated from two vaccinated volunteers by co-culture of peripheral mononuclear blood cells. The aim of this study was to compare the strains isolated from these human volunteers with Candid#1 strain regarding phenotypic characteristics of attenuation according to the indicators developed by Contigiani and Sabattini in 1977. The three strains were lethal to suckling mice but not to 10-12 days old mice and guinea pigs. Surviving guinea pigs from primary infection were protected when challenged by intra-muscular inoculation with lethal doses of a virulent strain. Infection and protection rates indicate that these strains are highly infective and protective in the hosts studied herein. These results demonstrate that Junin virus strains isolated from volunteers immunized with Candid#1 maintain the same attenuated phenotype of Candid#1 vaccine after one passage in humans.

Oral live attenuated human rotavirus vaccine (RotarixTM) offers sustained high protection against severe G9P[8] rotavirus gastroenteritis during the first two years of life in Brazilian children

In a large Phase III trial conducted in 10 Latin American countries, the safety and efficacy of the live attenuated monovalent rotavirus vaccine RIX4414 was evaluated in 15,183 healthy infants followed up during the first two years of life. Belém was the only site in Brazil included in this multicentre trial. The study in Belém included a subset of 653 infants who were followed up until 24 months of age for protection against severe rotavirus gastroenteritis. These subjects were randomly assigned in a 1:1 ratio to receive two doses of vaccine (n = 328) or two doses of placebo (n = 325) at approximately two and four months of age. Of the 653 enrolled infants, 23 dropped out during the study period. For the combined two-year period, the efficacy of RIX4414 was 72.3% [95% confidence interval (CI) 37.5-89.1%] against severe rotavirus-related gastroenteritis, reaching a protection rate of 81.8% (95% CI 36.4-96.6%) against circulating wild-type G9 rotavirus strains. It is concluded that two doses of RIX4414 are highly efficacious against severe rotavirus gastroenteritis in Belém during the first two years of life and provide high protection against the worldwide emergence and spread of G9P[8] strains.

Trends in adjuvant development for vaccines: DAMPs and PAMPs as potential new adjuvants

Aluminum salts have been widely used in vaccine formulations and, after their introduction more than 80 years ago, only few vaccine formulations using new adjuvants were developed in the last two decades. Recent advances in the understanding of how innate mechanisms influence the adaptive immunity opened up the possibility for the development of new adjuvants in a more rational design. The purpose of this review is to discuss the recent advances in this field regarding the attempts to determine the molecular basis and the general mechanisms underlying the development of new adjuvants, with particular emphasis on the activation of receptors of innate immune recognition. One can anticipate that the use of these novel adjuvants will also provide a window of opportunities for the development of new vaccines.

Acute diarrhoea in a community cohort of children who received an oral rotavirus vaccine in Northeast Brazil

Rotavirus is an important cause of childhood diarrhoea. A monovalent rotavirus vaccine (Rotarix®) was introduced into the Immunization Program of Brazil in 2006. In this study, we describe the incidence and burden of disease of rotavirus diarrhoea in two cohorts of children (vaccinated and unvaccinated). We followed two groups of 250 children under one year old, who were enrolled in December 2006 from a low-income residential area in Northeast Brazil. The children were monitored every two weeks for two years. Stool samples from children with diarrhoea were examined for the presence of rotavirus. Rotaviruses were genotyped using real time-polymerase chain reaction. The mean numbers of all-cause diarrhoea episodes/child (adjusted for age) in the first year were 0.87 and 0.84, in vaccinated and unvaccinated children, respectively. During the second year, the number of episodes/child decreased to 0.52 and 0.42. Only 16 (4.9 percent) of 330 stool samples were rotavirus-positive (10 vaccinated and 6 unvaccinated children) and only P[4]G2 rotaviruses were identified. All-cause diarrhoea episodes were more severe in unvaccinated children in the first year of age (p < 0.05), while vaccinated children had more severe episodes 18 months after vaccination. Rotavirus diarrhoea incidence was very low in both groups.

Vacuna contra la fiebre hemorrágica argentina Candid#1 producida en la Argentina: Inmunogenicidad y seguridad / Candid#1 vaccine against Argentine Hemorrhagic Fever produced in Argentina: Immunogenicity and safety

Se realizó un estudio clínico en 946 voluntarios humanos sanos, donde se comparó la vacuna Candid#1 producida en Argentina con la elaborada en EE.UU., que había sido utilizada en estudios previos. Como objetivo primario se evaluó la equivalencia en la eficacia utilizando como marcador subrogante a la inmunogenicidad medida por detección de anticuerpos neutralizantes. Como objetivo secundario se evaluó la equivalencia en inocuidad comparando las tasas de reacciones adversas. Ambas vacunas mostraron una tasa equivalente de inmunogenicidad ligeramente superior al 95.5%, que es la eficacia estimada para Candid #1 en estudios previos. No se observaron eventos adversos graves relacionados con la vacuna. Los eventos adversos generales considerados relacionados fueron de escasa significación clínica y de resolución espontánea o con tratamiento sintomático; se presentaron en los receptores de ambas vacunas en tasas equivalentes (29.9% para la vacuna fabricada en la Argentina y 35.0% para la fabricada en EE.UU.), e incluyeron: cefalea, decaimiento, mialgias, plaquetopenia leve (< 150 000 plaquetas/mm³), náuseas y/o vómitos, leucopenia leve (< 4 000 blancos/mm³), fiebre, dolor retroocular, mareos, microhematuria, lumbalgia y exantema. Estos resultados indican que la vacuna Candid #1 elaborada en la Argentina es equivalente a la elaborada en los EE.UU. Este estudio permitió el registro del biológico producido en la Argentina ante la autoridad regulatoria del país (ANMAT).

A clinical study in 946 human volunteers was done to compare Candid #1 vaccine manufactured in Argentina with the vaccine produced in USA that had been previously used. The efficacy was evaluated using immunogenicity measured by the detection of neutralizing antibodies as a subrogate marker. Safety was evaluated comparing the rate of adverse events. Both vaccines showed a comparable rate of seroconversion, slighty higher than the efficacy estimated from previous studies (95.5%). There were no severe adverse events related to the vaccines. The general events considered related to the vaccines were not clinically relevant and disappeared either spontaneously or with symptomatic treatment. Similar rates of adverse events (29.9% for the Argentine vaccine and 35.0% for the USA vaccine) were found for both vaccines. These included: headache, weakness, myalgias, mild low blood cell (< 4 000/mm³) and platelet (< 150 000/mm³) counts, nausea and/or vomiting, fever, retroocular pain, dizziness, microhematuria, low backache and exantema. These results indicate that the vaccine Candid#1 manufactured in Argentina is equivalent to the manufactured in USA. These results allowed the National Institute of Human Viral Diseases (INEVH) to register the vaccine produced locally under the National Regulatory Authority (ANMAT).

Preparation of a working seed lot of BCG and quality control by PCR genotyping / Preparación de un lote semilla de trabajo de BCG y control de calidad por genotipificación por PCR

The bacillus Calmette-Guérin (BCG) was obtained in 1920 after successive passages leading to the attenuation of a Mycobacterium bovis strain. For the following 40 years, BCG had been replicated, resulting in substrains with genotypic and phenotypic differences. Several genomic studies have compared two BCG strains, M. bovis and Mycobacterium tuberculosis, and observed that deleted regions in the different strains could be related to differences in antigenic properties. In this work, a working seed lot was obtained from a lyophilized secondary seed lot from the BCG Pasteur strain 1173 P2 and genetically characterized. The genome was analyzed by PCR directed to five regions (RD1, RD2, RD14, RD15, DU2), using the seed lot and different available strains as templates. No genetic differences were found in the fragments studied as compared to the Pasteur strain. A total of 20 passages were carried out and no differences were found in the size of the fragments amplified by PCR. In conclusion, this method allows to control a working seed lot genotypically and to assess the stability of the BCG genome.

El bacilo de Calmette-Guérin (BCG) se obtuvo en 1920, después de sucesivos pasajes que llevaron a la atenuación de una cepa de Mycobacterium bovis. A lo largo de los 40 años subsiguientes la cepa BCG fue replicada y surgieron subcepas con diferencias fenotípicas y genotípicas. Se realizaron varios estudios de comparación genómica de diferentes cepas de BCG, M. bovis y Mycobacterium tuberculosis, y se observó que las deleciones de regiones en las diferentes cepas podrían estar relacionadas con diferencias en las propiedades antigénicas. En este trabajo se describe la preparación y caracterización genética de un lote semilla de trabajo obtenido a partir de un lote semilla secundaria liofilizado de la cepa BCG Pasteur 1173 P2. Se analizaron por PCR cinco regiones (RD1, RD2, RD14, RD15, DU2) en el lote semilla de trabajo utilizando como control las diferentes cepas disponibles. No se hallaron diferencias genéticas en los fragmentos estudiados al comparar el lote semilla de trabajo con la cepa BCG Pasteur 1173 P2. Asimismo, se efectuaron hasta 20 pasajes y no se encontraron diferencias en el tamaño de los fragmentos amplificados por PCR. En conclusión, se ha puesto a punto un método que permite controlar el genotipo de un lote semilla de trabajo y evaluar la estabilidad del genoma del BCG.

A bovine herpesvirus 5 recombinant defective in the thymidine kinase (TK) gene and a double mutant lacking TK and the glycoprotein E gene are fully attenuated for rabbits

Bovine herpesvirus 5 (BoHV-5), the agent of herpetic meningoencephalitis in cattle, is an important pathogen of cattle in South America and several efforts have been made to produce safer and more effective vaccines. In the present study, we investigated in rabbits the virulence of three recombinant viruses constructed from a neurovirulent Brazilian BoHV-5 strain (SV507/99). The recombinants are defective in glycoprotein E (BoHV-5gEÄ), thymidine kinase (BoHV-5TKÄ) and both proteins (BoHV-5gEÄTKÄ). Rabbits inoculated with the parental virus (N = 8) developed neurological disease and died or were euthanized in extremis between days 7 and 13 post-infection (pi). Infectivity was detected in several areas of their brains. Three of 8 rabbits inoculated with the recombinant BoHV-5gEÄ developed neurological signs between days 10 and 15 pi and were also euthanized. A more restricted virus distribution was detected in the brain of these animals. Rabbits inoculated with the recombinants BoHV-5TKÄ (N = 8) or BoHV-5gEÄTKÄ (N = 8) remained healthy throughout the experiment in spite of variable levels of virus replication in the nose. Dexamethasone (Dx) administration to rabbits inoculated with the three recombinants at day 42 pi did not result in viral reactivation, as demonstrated by absence of virus shedding and/or increase in virus neutralizing titers. Nevertheless, viral DNA was detected in the trigeminal ganglia or olfactory bulbs of all animals at day 28 post-Dx, demonstrating they were latently infected. These results show that recombinants BoHV-5TKÄ and BoHV-5gEÄTKÄ are attenuated for rabbits and constitute potential vaccine candidates upon the confirmation of this phenotype in cattle.

Field study on immune response and performance of maternally immune commercial broiler chickens to live intermediate infectious bursal disease vaccine

In this study, 8000 Hubbared 1-day old broiler chicks having maternal antibodies to infectious bursal disease [IBD] were reared on deep litter in a poultry farm. The chicks were received IBD [Bursine-2] intermediate vaccine at the 12[th] day of life via drinking water to investigate its immunogenicity and its effect on broiler performance. No IBD related clinical signs or mortalities or lesions were observed after vaccination till the end of the breeding period [7 weeks]. The result of serological response to IBDV vaccines using ELISA test showed that the maternal antibody titer to IBD antigen in 1 day old chicks was 5571.1 +/- 1761.8 and waned to1237.7 +/- 915.8 at 2 weeks [2 days after vaccination. At the 3[rd] and 4[th] weeks after vaccination IBD ELISA titres were increased to 2662.1 +/- 186.3 and 3394.1 +/- 768.8; respectively. This result revealed that the used live IBD vaccine was able to induce antibody levels in chickens with maternal IBD antibodies. The best weekly feed conversion rate [FCR] was recorded at the 4[th] week [1.31] and the 6[th] week [1.71] with total FCR of 1.89. Mortality rate in the susceptible age [2-6 week] was the lowest [0.4-.73%] with total mortality of 3.27 at the end of the 7[th]. These fining pointed out that live IBD intermediate Burcin-2 vaccine was save, immunogenic to maternally immune chicks and has no adverse effect on performance of vaccinate chickens

Lambs Infected with UV-Attenuated Sporocysts of Sarcocystis ovicanis Produced Abnormal Sarcocysts and Induced Protective Immunity against a Challenge Infection

The present study surveyed the prevalence of natural infection of the sheep esphagus muscle with sarcocysts of Sarcocystis ovicanis and examined induction of protective immunity using UV-attenuated sporocysts. The overall prevalence of natural infection of the sheep was 95%. Infectivity of the collected sarcocysts was confirmed by shedding of sporulated oocysts after feeding infected esophageal tissues to dogs. To induce protective immunity, lambs were immunized 3 times (once a week) with 1.5 x 10(4) sporocysts exposed to UV-light for 30 min (UV-30 group) or 60 (UV-60 group) min and then challenged with 1.5 x 10(4) normal sporocysts at the 3rd week post the 1st vaccination. These lambs showed high survival and less clinical signs of sarcocystosis than normal infected lambs. The attenuated sporocysts produced abnormal cysts; small in size and detached from the muscle fiber. These abnormalities were more obvious in UV-60 group than UV-30 group. Also, the IFN-gamma level and lymphocyte percentage were increased while the total leukocyte count was decreased in the UV-60 group compared with other groups. The high level of IFN-gamma may be an evidence for the induction of Th1 responses which may have protective effect against a challenge infection.