Deletion of the thymidine kinase gene attenuates Caprine alphaherpesvirus 1 in goats.

Caprine alphaherpesvirus 1 (CpHV-1) is a pathogen associated with systemic infection and respiratory disease in kids and subclinical infection or reproductive failure and abortions in adult goats. The enzyme thymidine kinase (TK) is an important viral product involved in nucleotide synthesis. This property makes the tk gene a common target for herpesvirus attenuation. Here we deleted the tk gene of a CpHV-1 isolate and characterized the recombinant CpHV-1ΔTKin vitro and in vivo. In vitro characterization revealed that the recombinant CpHV-1ΔTK replicated to similar titers and produced plaques of similar size to the parental CpHV-1 strain in BT and CRIB cell lines. Upon intranasal inoculation of young goats, the parental virus replicated more efficiently and for a longer period than the recombinant virus. In addition, infection with the parental virus resulted in mild systemic and respiratory signs whereas the kids inoculated with the recombinant CpHV-1ΔTK virus remained healthy. Goats inoculated with the parental virus also developed higher neutralizing antibody titers when compared to CpHV-1ΔTK inoculated animals. Dexamethasone (Dx) administration on days 35-39 post-inoculation did not result in virus shedding in nasal secretions, indicating lack of reactivation from latency. However, viral DNA was detected in the trigeminal ganglia of animals euthanized at 14 days post-Dx, indicating that both viruses successfully established latent infection. Our results show that the recombinant CpHV-1ΔTK presents an attenuated phenotype when compared to the parental virus, and hence may represent a promising vaccine candidate to prevent CpHV-1 disease in goats.

Vaccinia viruses isolated from cutaneous disease in horses are highly virulent for rabbits.

Two genotypically distinct Vaccinia viruses (VACV), named P1V and P2V, were isolated from an outbreak of cutaneous disease in horses in Southern Brazil. We herein investigated the susceptibility of rabbits, a proposed animal model, to P1V and P2V infection. Groups of weanling rabbits were inoculated intranasally (IN) with P1V or P2V at low (10(2.5) TCID50), medium (10(4.5)TCID50), or high titer (10(6.5)TCID50). Rabbits inoculated with medium and high titers shed virus in nasal secretions and developed serous to hemorrhagic nasal discharge and severe respiratory distress, followed by progressive apathy and high lethality. Clinical signs appeared around days 3-6 post-inoculation (pi) and lasted up to the day of death or euthanasia (around days 5-10). Virus shedding and clinical signs were less frequent in rabbits inoculated with low virus titers. Viremia was detected in all groups, with different frequencies. Viral DNA was detected in the feces of a few animals inoculated with P1V and P2V, low titer, and with P2V at high titer. Gross necropsy findings and histological examination showed diffuse interstitial fibrousing pneumonia with necrosuppurative bronchopneumonia and intestinal liquid content. Neutralizing antibodies were detected in all inoculated animals surviving beyond day 9 pi. These results show that rabbits are highly susceptible to VACV isolated from horses, and develop severe respiratory and systemic disease upon IN inoculation. Thus, rabbits may be used to study selected aspects of VACV infection and disease.

Detecção de anticorpos contra o vírus da diarréia viral bovina (BVDV) em amostras de tanques de leite de rebanhos do Rio Grande do Sul

Uma técnica de soro-neutralização rápida (SNR), anteriormente adaptada para a detecção de anticorpos contra o vírus dadiarréia viral bovina (BVDV) no leite foi utilizada para a pesquisa de anticorpos anti-BVDV em amostras de recipientes coletivosde leite de propriedades leiteiras no Rio Grande do Sul. Inicialmente, a SNR foi comparada com um teste comercial do tipoELISA, na pesquisa de anticorpos em amostras de leite de 430 vacas de status sorológico conhecido. Das 430 amostrastestadas, as duas técnicas concordaram em 368 (85,6%), sendo 266 positivas (61,9%) e 102 negativas (23,8%). Comparando-se com os resultados do ELISA, a SNR apresentou uma sensibilidade de 90,8%, especificidade de 74,4% e precisão de85,5%. O grau de concordância (k) foi de 0,65, que significa uma boa associação entre as técnicas. A técnica de SNR foi entãoutilizada para testar amostras de recipientes coletivos de leite de 11.711 rebanhos do estado do Rio Grande do Sul. Anticorposcontra o BVDV foram detectados no leite de 1.028 rebanhos (8,8%), sendo que 180 propriedades (1,5% do total) apresentaramtítulos altos (³80) de anticorpos no leite, sugerindo possuírem infecção ativa. Esses resultados demonstraram que a técnica deSNR é adequada para a detecção de anticorpos anti-BVDV no leite e pode ser utilizada em triagens para a identificação derebanhos positivos para o BVDV.