Alessandra D'Avila da Silva

Partial protection induced by a BHV-1 recombinant vaccine against challenge with BHV-5

Abstract: Bovine herpesvirus type 5 (BHV‐5) is the causative agent of bovine herpetic encephalitis, a major concern for cattle farming in Brazil and Argentina. We recently developed a differential, gE‐negative vaccine (265 gE‐), based on a Brazilian BHV‐1 strain. The present study was carried out to examine whether such a vaccine would confer protection to BHV‐5 infections. It was concluded that the recombinant BHV‐1 vaccine tested here is not capable of conferring full protection to BHV‐5 challenge.

Caracterização antigênica e molecular de oito amostras do vírus da doença de Aujeszky isoladas no estado do Rio Grande do Sul em 2003

Pseudorabies or Aujeszkys disease (AD), caused by pseudorabies virus (PRV) is a major concern in swine production. In the state of Rio Grande do Sul, Brazil, AD was only detected in 1954, in cattle. In 2003 two outbreaks of encephalitis occurred on the northern region of the state, close to the border with the state of Santa Catarina. Pseudorabies virus (PRV) was isolated from distinct farms within the region and subjected to antigenic and genomic analyses. These isolates were compared with prototype strains NIA-3 and NP. Antigenic characterization with a panel of monoclonal antibodies (Mabs) directed to viral glycoproteins (gB, gC, gD and gE,) was performed by an imunoperoxidase monolayer assay (IPMA) on infected cell monolayers. Genomic characterization was carried out by restriction enzyme analysis (REA) of the whole DNA viral genome with Bam HI. The antigenic profile of the eight isolates from Rio Grande do Sul as well as strains NIA-3 and NP were similar. REA analysis revealed that all isolates from Rio Grande do Sul displayed a genomic type II arrangement, a genotype often found in other outbreaks of AD previously reported in other Brazilian states. The results obtained suggest that the eight isolates examined here were similar.

Experimental infection of rabbits with a recombinant bovine herpesvirus type 5 (BoHV-5) gI, gE and US9-negative

Bovine herpesvirus type 5 (BoHV-5) is a major cause of viral meningoencephalitis in cattle. The expression of different viral proteins has been associated with BoHV-5 neuropathogenesis. Among these, gI, gE and US9 have been considered essential for the production of neurological disease in infected animals. To evaluate the role of gI, gE and US9 in neurovirulence, a recombinant from which the respective genes were deleted (BoHV-5 gI-/gE-/US9-) was constructed and inoculated in rabbits of two age groups (four and eight weeks-old). When the recombinant virus was inoculated through the paranasal sinuses of four weeks-old rabbits, neurological disease was observed and death was the outcome in 4 out of 13 (30.7 %) animals, whereas clinical signs and death were observed in 11/13 (84.6%) of rabbits infected with the parental virus. In eight weeks-old rabbits, the BoHV-5 gI-/gE-/US9- did not induce clinically apparent disease and could not be reactivated after dexamethasone administration, whereas wild type BoHV-5 caused disease in 55.5% of the animals and was reactivated. These findings reveal that the simultaneous deletion of gI, gE and US9 genes did reduce but did not completely abolish the neurovirulence of BoHV-5 in rabbits, indicating that other viral genes may also play a role in the induction of neurological disease.

Field evaluation of safety during gestation and horizontal spread of a recombinant differential bovine herpesvirus 1 (BoHV-1) vaccine

Infeccoes pelo herpesvirus bovino tipo 1 (BoHV-1) sao importantes causas de doenca respiratoria, reprodutiva e abortos em bovinos. A vacinacao e frequentemente empregada para minimizar as perdas produzidas pela infeccao. Todavia, a imunizacao de vacas durante a prenhez com algumas vacinas contendo virus vivo modificado (MLV) pode ocasionalmente causar abortos. Em trabalho previo, nosso grupo desenvolveu uma vacina recombinante de BoHV-1 construida a partir de um isolado brasileiro de BoHV-1 (Franco et al., 2002a) do qual o gene que codifica para a glicoproteina E (gE) foi artificialmente deletado. Tal recombinante (gE-) vem sendo avaliado como vacina diferencial, isto e, capaz de permitir a diferenciacao entre animais vacinados e infectados. No presente estudo, o potencial de disseminacao do virus recombinante foi avaliado em um rebanho de gado de corte, em condicoes de campo. Para tanto, a seguranca da vacina gE- quando aplicada durante a prenhez foi avaliada pela inoculacao intramuscular de 107,4 doses infectantes para 50% dos cultivos celulares (DICC50) do virus em 22 femeas prenhes (14 previamente soronegativas e 8 previamente soropositivas para BoHV-1) em diferentes fases da gestacao. Outras 15 vacas prenhes foram mantidas como controles nao-vacinados. Nao ocorreram abortos, natimortos ou anormalidades fetais em nenhum dos grupos. Soroconversao foi observada nas femeas vacinadas previamente soronegativas. Em um segundo experimento, 4 novilhas foram inoculadas pela via intranasal com 107,6 DICC50 do virus recombinante, sendo mantidos em contato com 16 novilhas em uma area de campo, a uma densidade de 1 animal por hectare. Os animais foram monitorados quanto a presenca de sinais clinicos; amostras de soro foram coletadas nos dias 0, 30, 60 e 180 apos a vacinacao. Soroconversao foi observada apenas nos animais vacinados e nao nos contatos. Estes resultados indicam que, nas condicoes do presente estudo, a vacina gE- nao tem efeitos deleterios para femeas gestantes nem para seus fetos e nao se dissemina horizontalmente no rebanho.

Efficacy of a gE-deleted, bovine herpesvirus 1 (BoHV-1) inactivated vaccine.

Bovine herpesvirus type 1 (BoHV-1) is recognized as a major cause of economic losses in cattle. Vaccination has been widely applied to minimize losses induced by BoHV-1 infections. We have previously reported the development of a differential BoHV-1 vaccine, based on a recombinant glycoprotein E (gE)-deleted virus (265gE-). In present paper the efficacy of such recombinant was evaluated as an inactivated vaccine. Five BoHV-1 seronegative calves were vaccinated intramuscularly on day 0 and boostered 30 days later with an inactivated, oil adjuvanted vaccine containing an antigenic mass equivalent to 107.0 fifty per cent cell culture infectious doses (CCID50) of 265gE-. Three calves were kept as non vaccinated controls. On day 60 post vaccination both vaccinated and controls were challenged with the virulent parental strain. No clinical signs or adverse effects were seen after or during vaccination. After challenge, 2/5 vaccinated calves showed mild clinical signs of infection, whereas all non vaccinated controls displayed intense rhinotracheitis and shed virus for longer and to higher titres than vaccinated calves. Serological responses were detected in all vaccinated animals after the second dose of vaccine, but not on control calves. Following corticosteroid administration in attempting to induce reactivation of the latent infection, no clinical signs were observed in vaccinated calves, whereas non vaccinated controls showed clinical signs of respiratory disease. In view of its immunogenicity and protective effect upon challenge with a virulent BoHV-1, the oil adjuvanted preparation with the inactivated 265gE- recombinant was shown to be suitable for use as a vaccine.