RESUMO
Infectious Bovine Rhinothracheitis (IBR) caused by bovine herpesvirus 1 (BoHV-1) infection is distributed worldwide. BoHV-1 either alone or in association with other respiratory cattle pathogens causes significant economic losses to the livestock industry. The aim of this work was to validate a guinea pig model as an alternative method to the current BoHV-1 vaccine potency testing in calves. Guinea pigs were immunized with two doses of vaccine, 21 days apart and sampled at 30 days post vaccination (dpv). BoHV-1 antibody (Ab) response to vaccination in guinea pigs, measured by ELISA and virus neutralization (VN), was statistically compared to the Ab response in cattle. The guinea pig model showed a dose-response relationship to the BoVH-1 antigen concentration in the vaccine and it was able to discriminate among vaccines containing 1log(10) difference in its BoHV-1 concentration with very good repeatability and reproducibility (CV < or = 20%). A regression analysis of the Ab titers obtained in guinea pigs and bovines at 30 and 60dpv, respectively, allowed us to classify vaccines in three potency categories: "very satisfactory", "satisfactory" and "unsatisfactory". Bovines immunized with vaccines corresponding to each of these three categories were experimentally challenged with BoVH-1 virus, the level of protection, as measured by reduction of virus shedding and disease severity, correlated well with the vaccine category used. Data generated by 85 experiments, which included vaccination of calves and guinea pigs with 18 reference vaccines of known potency, 8 placebos and 18 commercial vaccines, was subjected to statistical analysis. Concordance analysis indicated almost perfect agreement between the model and the target species for Ab titers measured by ELISA and almost perfect to substantial agreement when Ab titers were measured by VN. Taken together these results indicate that the developed guinea pig model represents a novel and reliable tool to estimate batch-to-batch vaccine potency and to predict efficacy of killed BoHV-1 veterinary vaccines.
Assuntos
Modelos Animais de Doenças , Herpesvirus Bovino 1/imunologia , Herpesvirus Bovino 1/patogenicidade , Rinotraqueíte Infecciosa Bovina/prevenção & controle , Vacinas Virais/imunologia , Animais , Anticorpos Neutralizantes/sangue , Anticorpos Antivirais/sangue , Bovinos , Relação Dose-Resposta Imunológica , Ensaio de Imunoadsorção Enzimática , Feminino , Cobaias , Rinotraqueíte Infecciosa Bovina/imunologia , Masculino , Testes de Neutralização , Reprodutibilidade dos Testes , Índice de Gravidade de Doença , Estados Unidos , Eliminação de Partículas Virais/imunologiaRESUMO
The use of foot-and-mouth disease (FMD) vaccines that do not induce antibodies against non-structural proteins (NSP) is extremely relevant for the demonstration of regions "free of FMDV infection" and control strategies. In this study cattle were primed and boosted with five doses of oil vaccines containing high antigenic payloads on days 0, 90, 130, 160 and 200. The serological response against NSP was measured using four commercially available assays: two 3ABC-ELISAs; one 3B-ELISA (and complementary 3A-ELISA) and an enzyme-immunotransfer blot assay (EITB). Additionally, locally produced NSP antibodies detection reagents and VIAA antibodies were evaluated. A high level of specific immune response against vaccine strains was shown. After four doses of vaccine, non-reactive animals were detected by any of the NSP assays. After the fifth immunization, 2 of 17 animals were reactive in one ELISA kit, but these samples proved negative by confirmatory tests. Antibodies against NSP were not detected in single dose immunized cattle. The principle of the NSP-ELISA used as a screening test for large sero-surveys in South America is established and this paper emphasizes the importance of using vaccines that have demonstrated no interference with NSP antibodies detection assays.
Assuntos
Anticorpos Antivirais/sangue , Aphthovirus/imunologia , Doenças dos Bovinos/imunologia , Proteínas não Estruturais Virais/imunologia , Vacinas Virais/imunologia , Animais , Bovinos , Doenças dos Bovinos/epidemiologia , Doenças dos Bovinos/virologia , Ensaio de Imunoadsorção Enzimática/veterinária , Febre Aftosa/prevenção & controleRESUMO
This paper describes the antigenic and molecular characterisation of foot-and-mouth disease virus (FMDV) strains isolated during the 2000-2002 epidemic in Argentina, and the strategy implemented for disease control. Two different FMDV serotypes, O and A, were involved. Of the various field isolates studied, two distinct O1 lineages (strains Corrientes/00 and Misiones/00) and two serotype A lineages (A/Argentina/00 and A/Argentina/01 prototypes) were identified. The genome sequences of these strains were compared with sequences of previous regional isolates and sequences of vaccine strains. O1 strains were found to be related to regional strains while serotype A strains were found to be more distanced from them. The updating of the antigenic composition of the vaccines used in the emergency was a key issue, since the outbreaks stopped shortly after the implementation of the vaccination programs. The O1 strains quickly disappeared from the field following strict control measures and the use of vaccines containing O1/Campos strain. However, in the case of the A serotype strains, the situation was different, since the use of a vaccine containing strain A24/Cruzeiro yielded acceptable levels of protection only after re-vaccination. Therefore, the new field strains A/Argentina/00 and A/Argentina/01 were incorporated into the vaccine, leading to an effective control of the disease. Viral circulation greatly diminished, as indicated by the significant reduction in the number of outbreaks and in the number of animals with antibodies against non-structural proteins. Satisfactory levels of protective antibodies were subsequently detected in the cattle population (above 75% protection). The absence of outbreaks after January 2002 indicated that the epidemic was controlled.