Comparative histopathological and immunological study of two field strains of chicken anemia virus.

Infection of poultry with chicken anemia virus (CAV) is implicated in several field problems in broiler flocks due to the immunosuppression generated and, consequently, the increased susceptibility to secondary infections. Recently, we have reported an increased occurrence of clinical cases caused by CAV strains distantly related to those commonly used for vaccination. In order to understand the behavior of two Argentinean CAV strains (CAV-10 and CAV-18) in two-week-old chickens, an immune and histopathological study was performed. Neither mortality nor clinical signs were observed in the infected or control groups. Thymus lobes from chickens infected with both CAV viruses were smaller compared to the negative control group. At 14 days post-infection (dpi), only chickens inoculated with CAV-10 show a severe depletion of lymphocytes in the thymus cortex and in follicles from the bursa of Fabricius. Also thymopoiesis disorders, such as reduction in the percentage of total DP (CD4 + CD8α+) thymocytes and alteration in the percentages of DP subpopulations, were more important in animals inoculated with the CAV-10 than the CAV-18 strain. In addition, only animals infected with CAV-10 show a decrease in CD8αß splenocytes. Altogether our results show that, although both Argentinean CAV strains produce subclinical infections in chickens causing immunosuppression at 14 dpi, they might differ in their in vivo pathogenicity.

Evasion of maternal antibody protection by an IBDV Argentine variant.

Infectious bursal disease (IBD) is a viral disease that affects the ability of chickens to produce humoral immune responses. One way to prevent the disease is the passage of maternally derived antibodies (MDA) from dams to offsprings via the yolk. Despite sanitary measures, which include immunization with genogroup 1 (G1) vaccines, infections with IBDV genogroup 4 (G4) in young animals have been detected. The aim of this study was to determine whether a local IBDV isolate belonging to G4 could evade the immunity generated by MDAs. Twelve-day-old animals positive for MDA, were inoculated with G1 or G4 isolates or phosphate buffered saline (PBS) as a control. After 1 wk, the animals were sacrificed and the following parameters were evaluated: bursa-body (BB) ratio, viral load, and histologic damage in the bursa of Fabricius. Results showed that G4-infected animals had significant differences in the BB ratio compared to the PBS group. In addition, viral load was significantly higher in the G4 group than in the G1 group. Histologic damage in the bursa of Fabricius was detected only in G4-infected MDA chickens. Our results suggest that infection with G4 local isolate can circumvent the immunity generated by MDA and, furthermore, that G4 isolate does not differ in its pathogenicity from G1 isolate, which underlines the need to include variant strains in vaccine formulations to reduce potential losses caused by these viruses.

Study of coinfection with local strains of infectious bursal disease virus and infectious bronchitis virus in specific pathogen-free chickens.

Immunosuppressive diseases cause great losses in the poultry industry, increasing the susceptibility to infections by other pathogens and promoting a suboptimal response to vaccination. Among them, infectious bursal disease virus (IBDV) arises as one of the most important around the world. IBDV infects immature B lymphocytes, affecting the immune status of birds and facilitating infections by other pathogens such as avian infectious bronchitis virus (IBV). Although it has been reported that the interaction between these viruses increases IBV clinical signs, there are no actual studies about the interaction between regional circulating isolates that validate this statement. In this context, the objective of our work was to evaluate the effect of the interaction between local isolates of IBDV (belonging to genogroup 4) and IBV (lineage GI-16) in chickens. Thus, specific pathogen-free chickens were orally inoculated with IBDV genogroup (G) 4 or with PBS at 5 d of age. At 14-days postinoculation (dpi) the animals were intratracheally inoculated with a GI-16 IBV or with PBS. At multiple time points, groups of birds were euthanized and different parameters such as histological damage, viral load, lymphocyte populations and specific antibodies were evaluated. The success of IBDV infection was confirmed by the severity of bursal atrophy, viral detection, and presence of anti-IBDV antibodies. In IBV-infected animals, the presence of viral genome was detected in both kidney and bursa. The coinfected animals showed higher degree of lymphocyte infiltration in kidney, higher rate of animals with IBV viral genome in bursa at 28 dpi, and a clear decrease in antibody response against IBV at 28, 35, and 40 dpi. The results indicate that the infection with the local isolate of IBDV affects the immune status of the chickens, causing major severe damage, in response to IBV infection, which could consequently severely affect the local poultry industry.

Comparative Study of the Immune Response Induced by an Argentinian Classical Strain of IBDV in Two Chicken Breeds.

The hybrid chicken Negra INTA, which originated at the National Institute of Agricultural Technology (INTA), is the product of the cross between Barred Plymouth Rock females and Rhode Island Red males, and it is used as a laying hen for egg consumption. It has been characterized by productive parameters, but the characterization from an immunological perspective has not been done yet. Infectious bursal disease virus (IBDV) causes a highly contagious viral disease that affects the bursa of Fabricius. Although most chickens are regularly vaccinated against IBDV, this virus still generates negative impacts on production with significant economic losses. The aim of the present work was to compare the immune responses of the Negra INTA hybrid and the White Leghorn layer line to the infection with a field isolate of IBDV. Four-week-old chickens were infected with a single dose of IBDV and at 3, 5, 7, and 30 days postinfection (dpi), bursae were removed, and different parameters were evaluated. Results showed that the reduction of the bursa body (BB) ratio and the histopathological damage were maximum on day 7 postinfection (pi). The viral load was greater in the hybrid Negra INTA at 5 dpi. The humoral immune response between both breeds was similar, although more animals from the commercial line showed higher titers of neutralizing antibodies. Flow cytometry analysis revealed that Bu+ bursal lymphocytes reached a minimum at 7 dpi. Meanwhile, T cell infiltration measured by the percentage of CD3+, CD4+, and CD8+ cells in the bursa was at its maximum at 5 dpi. To our knowledge, this work describes for the first time the pathogenesis and the immune response caused by an Argentinian IBDV isolate in two different chicken lines.

Oral Immunization With Plant-Based Vaccine Induces a Protective Response Against Infectious Bursal Disease.

Infectious bursal disease virus (IBDV) is the etiological agent of an immunosuppressive and highly contagious disease that affects young birds causing important economic losses in the poultry industry worldwide. We have previously developed a plant-based vaccine candidate for infectious bursal disease (IBD) that is able to protect against infection with IBDV when administered through intramuscular (im) route. Given that oral vaccination is non-invasive and stimulates the immunity of the mucosal gastrointestinal surface, the initial site of contact and entry of IBDV, the aim of this work was to study if our immunogen was also able to elicit a protective immune response when orally administered. We demonstrated that 85% of the animals that received two oral doses of the vaccine formulation and all animals that were orally boosted after an im prime scheme developed virus neutralizing antibodies and were protected against IBDV infection, evidenced by the bursa/body weight (BB) ratio, absence of T-cell infiltration, and low viral load in bursa. Although mild to moderate bursal damage was observed in some of these animals, these lesions were not as severe as the ones observed in challenged control groups, which also presented signs of acute inflammation, bursal atrophy, T-cell infiltration, and absence of viral clearance. These results show that two immunizations with our recombinant immunogen are able to induce a specific and protective immune response in chicken against IBDV when orally administered in a prime/boost scheme or when the oral boost follows an im prime scheme. In conclusion, our oral plant-based vaccine candidate could represent a viable alternative to conventional vaccines and is of great interest to the poultry industry.

Evaluation of the Efficiency of Commercial Vaccines Against Infectious Bronchitis Virus (IBV) Belonging to the GI-16 Lineage Isolated in an Argentinean Outbreak.

In this study we evaluated the effectiveness of adding serotype 793B vaccine to an immunization program in order to control the infectious bronchitis virus (IBV) GI-16 lineage. Therefore, two different experiments were performed. First, a virus cross-neutralization test was carried out, which indicated that neither the Massachusetts (Mass) nor 793B serotypes are antigenically related to the field isolate A13 (GI-16). We also performed a challenge trial to evaluate if the Mass/793B combination is more efficient than Mass/Connecticut (Conn) to protect chickens against the Argentinian variant A13. Thus, 40 chickens were organized in four groups. Chickens in Group A were vaccinated at 1 day of age with Mass serotype and then at 14 days old with Mass plus Conn serotypes. Chickens in Group B received Mass and 793B serotypes at 1 and 14 days old, respectively. Groups C and D remained unvaccinated. At 28 days of age, Groups A, B, and C were challenged with the A13 isolate, while Group D remained as the negative control. The statistical analysis of the ciliostasis evaluation, performed at 7 days postchallenge (dpch), indicated that the difference between Mass/793B and Mass/Conn was not significant (p > 0.05). However, the comparison against the negative control showed that only Group A was significantly different, suggesting a slightly better performance on blocking ciliostasis for the Mass/793B combination. On the other hand, no significant differences were observed in the viral load, quantified by reverse-transcription quantitative real-time PCR (RT-qPCR) in tracheal swabs and kidneys (at 3 and 7 dpch, respectively) between vaccinated groups. Furthermore, some amounts of the viral genome were found in both vaccinated groups that could indicate that neither the Mass/793B nor the Mass/Conn combinations totally inhibited the viral replication. Such viral replication in vaccinated chickens should seriously be taken into consideration because it could promote the selection of new variants in the future.

Nota de investigación­Evaluación de la eficacia de vacunas comerciales contra el virus de la bronquitis infecciosa (IBV) perteneciente al linaje GI-16 aislado durante un brote argentino. En este estudio se evaluó la efectividad de agregar la vacuna del serotipo 793B a un programa de inmunización para controlar al virus de la bronquitis infecciosa (con las siglas en inglés IBV) linaje GI-16. Por tanto, se realizaron dos experimentos diferentes. Primeramente, se llevó a cabo una prueba de neutralización cruzada de virus, que indicó que ni los serotipos Massachusetts (Mass) ni 793B están antigénicamente relacionados con el aislado de campo A13 (GI-16). También se realizó una prueba de desafío para evaluar si la combinación Massachussets/793B era más eficiente que Massachussets/Connecticut (Conn) para proteger a los pollos contra la variante argentina A13. De esta forma, 40 pollos se organizaron en cuatro grupos. Los pollos del Grupo A se vacunaron al día de edad con el serotipo Massachussets y luego a los 14 días con los serotipos Massachussets más Connecticut. Los pollos del Grupo B recibieron los serotipos Massachussets y 793B a los 1 y 14 días de edad, respectivamente. Los grupos C y D permanecieron sin vacunar. A los 28 días de edad, los Grupos A, B y C fueron desafiados con el aislado A13, mientras que el Grupo D permaneció como control negativo. El análisis estadístico de la evaluación de la ciliostasis, realizada a los 7 días después del desafío (dpch), indicó que la diferencia entre el tratamiento Massachussets/793B y Massachussets/Connecticut no fue significativa (P> 0.05). Sin embargo, la comparación con el control negativo mostró que solo el Grupo A fue significativamente diferente, lo que sugiere un desempeño ligeramente mejor en el bloqueo de la ciliostasis para la combinación Massachussets/793B. Por otro lado, no se observaron diferencias significativas (P> 0.05) en la carga viral, cuantificada mediante transcripción reversa y PCR cuantitativa en tiempo real de hisopos traqueales y riñones (a 3 y 7 días después del desafío, respectivamente) entre los grupos vacunados. Además, se encontraron algunas cantidades del genoma viral en ambos grupos vacunados que podrían indicar que ni las combinaciones Massachussets/793B ni Massachussets/Connecticut inhibieron totalmente la replicación viral. Esta replicación viral en pollos vacunados debe tenerse muy en cuenta porque podría promover la selección de nuevas variantes en el futuro.

Plant-based vaccine candidate against Infectious bursal disease: An alternative to inactivated vaccines for breeder hens.

Infectious bursal disease (IBD) is an acute, highly contagious immunosuppressive disease that affects young birds causing important economic losses in the poultry industry worldwide. Strict hygiene management together with effective vaccination programs are the most important strategies to prevent Infectious bursal disease virus entry in poultry production facilities. Hyperimmunisation of dams with inactivated vaccines just before the laying period provides passive immunity to the progeny that protects them during the critical first few weeks after hatching before vaccination with live attenuated virus takes place. In the present study, a safe and economic plant-based vaccine candidate against IBD intended for breeder hens was evaluated. We demonstrated that the recombinant immunogen is effective as booster for previously primed hens since it increases specific antibodies against VP2 that are transmitted to the offspring with titres and decay rate similar to those achieved by inactivated vaccine. Moreover, these maternally derived antibodies have virus neutralising activity and are able to confer protection against challenge in progeny, as evidenced by absence of bursal damage and low viral titres in this organ. Taking into account the disadvantages of inactivated vaccines as well as the benefits of plants as expression systems, such as time and cost efficiency, lower risk of contamination from animal pathogens and nearly unlimited scalability, a plant-based subunit IBD vaccine represents a viable alternative in the veterinary field.

Hospitalizaciones pediátricas por infecciones respiratorias agudas durante la pandemia por SARS-CoV-2. Hospital Británico, Uruguay / Hospitalizations due to acute respiratory infections during SARS-CoV-2 Pandemic. British Hospital, Uruguay / Hospitalizações pediátricas por infecções respiratórias agudas durante a pandemia de SARS-CoV-2 no Hospital Britânico, Uruguai

Resumen: Introducción: el 11 de marzo la enfermedad COVID-19, causada por SARS-CoV-2, fue declarada pandemia. En Uruguay el Plan Nacional Coronavirus desde el 16 de marzo suspendió actividades presenciales educativas y espectáculos públicos; recomendó confinamiento voluntario, adoptar distanciamiento físico, uso de tapaboca y lavado de manos. Objetivo: describir hospitalizaciones por infecciones respiratorias agudas (IRA) de niños de 0 a 14 años entre el 1/1/2020 y el 31/5/2020 durante la pandemia comparadas con aquellas en igual período en 2018 y 2019 y los resultados de la investigación de SARS-CoV-2 en casos sospechosos. Metodología: se incluyeron egresos por IRA, bronquiolitis, neumonía viral y neumonía en unidades de cuidados moderados e intensivos. Se describen: egresos totales, casos, tasa por 1.000 egresos (intervalo de confianza 95% = IC95%) y la distribución por grupos etarios (< 2, 2 a 4 y 5 a 14 años). En 2020 se promovió la atención telefónica, por telemedicina o en domicilio para pacientes sin criterios de hospitalización; se describen hallazgos microbiológicos en casos de IRA y sospechosos de SARS-CoV-2. Resultados: la tasa promedio de egresos por IRA en cuidados moderados en 2018 y 2019 que fue 94 (IC95%: 72-117), en 2020 fue 15 (IC95%: 3-27), con una reducción significativa de 85%. Se investigó SARS-CoV-2 en 30 niños, los resultados fueron negativos. En 2020 no se hospitalizaron niños menores de 1 año, ni casos de infección por influenza, VRS o SARS-CoV-2. Conclusión: las medidas adoptadas contribuyeron a la reducción significativa de hospitalizaciones por IRA.

Summary: Introduction: on March 11th, COVID-19 caused by SARS CoV-2 was declared a pandemic. The Uruguayan National Coronavirus Plan was set up on March 16th and suspended in-person educational activities and public shows; set a voluntary quarantine, social distancing, face masks and hand washing as main recommendations. The British Hospital Contingency Committee approved the healthcare modifications established by Department of Pediatrics. Objective: describe hospitalizations for acute respiratory infection (ARI) in children of 0-14 years of age between 1/1/2020 and 5/31/2020 during the pandemic, compare them to those in the same period in 2018 and 2019, and describe the microbiological findings in children with IRA and suspected cases of SARS CoV-2 infection during 2020. Methodology: we included all discharges from Moderate Care Unit due to ARI, bronchiolitis, viral pneumonia and pneumonia and described total discharges, cases and rates per 1000 discharges (Confidence Interval 95%=CI95%). In 2020, we described healthcare modifications at all levels of care (telephone or telemedicine assistance and home care was promoted) and seasonal respiratory virus cases and SARS CoV-2 nucleic acid detection results. Results: the average rate of discharges due to ARI in Moderate Care Units in 2018 and 2019 was 94 (95% CI: 72-117). In 2020, the rate was 15 (95% CI: 3-27), and showed a significant reduction of 85%. SARS CoV-2 was researched in 30 children, all results were negative. There were no hospitalizations of children of under one year of age due to influenza, RSV or SARS CoV-2 Conclusion: the measures adopted contributed to the significant reduction in hospitalizations due to ARI.

Resumo: Introdução: o dia 11 de março de 2020 a COVID-19 causada pelo SARS CoV-2 foi declarada pandêmica. No Uruguai, as autoridades do Plano Nacional do Coronavírus suspenderam atividades educativas presenciais e shows públicos desde o dia 16 de março e recomendaram o confinamento voluntário, adotando distanciamento físico, uso de máscara e lavagem das mãos. Objetivo: descrever as hospitalizações por infecções respiratórias agudas (IRA) em crianças de 0 a 14 anos de idade entre 01/01/2020 e 31/05/2020 durante a pandemia em comparação com as do mesmo período em 2018 e 2019 e os resultados da Pesquisa do SARS CoV-2 em casos suspeitos. Metodologia: incluíram-se altas das Unidades de Terapia Moderada e Intensiva por IRA, bronquiolite, pneumonia viral e pneumonia. Descrevemos altas totais, casos, totais, taxa por 1000 altas (intervalo de confiança de 95% = IC 95%) e distribuição por grupos de idade (<2, 2 a 4 e 5 a 14 anos). Descrevemos as mudanças promovidas para o caso de atendimento telefónico, telemedicina e atendimento domiciliar para pacientes sem critérios de internação e os achados microbiológicos para casos de IRA e suspeitos de SARS CoV-2. Resultados: a taxa média de alta por IRA em cuidados moderados em 2018 e 2019 foi de 94 (IC 95%: 72-117), em 2020 foi de 15 (IC 95%: 3-27), mostrando uma redução significativa de 85 %. O SARS CoV-2 foi pesquisado em 30 crianças e os resultados foram negativos. Em 2020, nenhuma criança de menos de um ano foi hospitalizada, nem houve casos de infecção por influenza, RSV ou SARS CoV-2. Conclusão: As medidas adotadas contribuíram para redução significativa das internações por IRA.