Comparative studies of BHV-1 variants by in vivo--in vitro tests

Neutralizing antibodies to bovine and bubaline alphaherpesviruses in water buffaloes (Bubalus bubalis)

Water buffaloes (Bubalus bubalis) have been introduced in many regions of the world as a source of animal protein. In many instances, bubaline cattle are reared close to or mixed with bovine or zebuine cattle. However, little is known about infectious diseases of bubaline and the interactions that may arise involving the microbiota of those species. Alphaherpesviruses of ruminants (bovine alphaherpesviruses types 1 and 5, BoHV-1, BoHV-5; bubaline alphaherpesvirus 1, BuHV-1) are highly cross-reactive in serological assays performed with bovine or zebuine sera. However, the profile of reactivity of bubaline cattle sera to alphaherpesviruses remains unknown. As such, it is not known which virus strain (or strains) would be most appropriate to be used as the challenge virus in the laboratory in search for alphaherpesvirus-neutralizing antibodies. In this study, the profile of neutralizing antibodies to alphaherpesviruses in bubaline sera was determined against different types/subtypes of bovine and bubaline alphaherpesviruses. Sera (n=339) were screened in a 24-h serum neutralization test (SN) against 100 TCID50 of each of the challenge viruses. From those, 159 (46.9 %) neutralized at least one of the viruses assayed; 131 (38.6%) sera neutralized the three viral strains used for screening. The viral strain that was neutralized by the largest number of sera was BoHV-5b A663 (149/159; 93.7%). A few sera neutralized only one of the challenge viruses: four sera neutralized BoHV-1 LA only; another neutralized BoHV-5 A663 only and four others neutralized BuHV-1 b6 only. SN testing with two additional strains gave rise to similar results, where maximum sensitivity (defined here as the largest number of sera that neutralized the challenge viruses) was obtained by adding positive results attained with three of the challenge strains. Differences in neutralizing antibody titers were not significant to allow inferences on which would be the most likely virus that induced the antibody responses detected here.

Comparison between DNA Detection in Trigeminal Nerve Ganglia and Serology to Detect Cattle Infected with Bovine Herpesviruses Types 1 and 5

Bovine herpesviruses (BoHVs) types 1 (BoHV-1) and 5 (BoHV-5) are alphaherpesviruses of major importance to the bovine production chain. Such viruses are capable of establishing latent infections in neuronal tissues. Infected animals tend to develop a serological response to infection; however, such response—usually investigated by antibody assays in serum—may eventually not be detected in laboratory assays. Nevertheless, serological tests such as virus neutralization (VN) and various enzyme-linked immunosorbent assays (ELISAs) are widely employed to check individual or herd status of BoHV infections. The correlation between detection of antibodies and the presence of viral nucleic acids as indicatives of infection in infected cattle has not been deeply examined. In order to investigate such correlation, 248 bovine serum samples were tested by VN to BoHV-1 and BoHV-5, as well as in a widely employed (though not type-differential) gB ELISA (IDEXX IBR gB X2 Ab Test) in search for antibodies to BoHVs. Immediately after blood withdrawal, cattle were slaughtered and trigeminal ganglia (TG) excised for DNA extraction and viral nucleic acid detection (NAD) by nested PCR. Neutralizing antibodies to BoHV-1 and/or BoHV-5 were detected in 44.8% (111/248) of sera, whereas the gB ELISA detected antibodies in 51.2% (127/248) of the samples. However, genomes of either BoHV-1, BoHV-5, or both, were detected in TGs of 85.9% (213/248) of the animals. These findings reveal that the assays designed to detect antibodies to BoHV-1 and/or BoHV-5 employed here may fail to detect a significant number of latently infected animals (in this study, 35.7%). From such data, it is clear that antibody assays are poorly correlated with detection of viral genomes in BoHV-1 and BoHV-5-infected animals.

Sequence analysis of the 5' third of glycoprotein C gene of South American bovine herpesviruses 1 and 5

Bovine herpesviruses 1 (BoHV-1) and 5 (BoHV-5) share high genetic and antigenic similarities, but exhibit marked differences in tissue tropism and neurovirulence. The amino-terminal region of glycoprotein C (gC), which is markedly different in each of the viruses, is involved in virus binding to cellular receptors and in interactions with the immune system. This study investigated the genetic and antigenic differences of the 5′ region of the gC (5′ gC) gene (amino-terminal) of South American BoHV-1 (n=19) and BoHV-5 (n=25) isolates. Sequence alignments of 374 nucleotides (104 amino acids) revealed mean similarity levels of 97.3 and 94.2% among BoHV-1 gC (gC1), respectively, 96.8 and 95.6% among BoHV-5 gC (gC5), and 62 and 53.3% between gC1 and gC5. Differences included the absence of 40 amino acid residues (27 encompassing predicted linear epitopes) scattered throughout 5′ gC1 compared to 5′ gC5. Virus neutralizing assays testing BoHV-1 and BoHV-5 antisera against each isolate revealed a high degree of cross-neutralization between the viruses, yet some isolates were neutralized at very low titers by heterologous sera, and a few BoHV-5 isolates reacted weakly with either sera. The virus neutralization differences observed within the same viral species, and more pronounced between BoHV-1 and BoHV-5, likely reflect sequence differences in neutralizing epitopes. These results demonstrate that the 5′ gC region is well conserved within each viral species but is divergent between BoHV-1 and BoHV-5, likely contributing to their biological and antigenic differences.

Comparative study on the in vitro and in vivo properties of two bovine herpesvirus-5 reference strains

BACKGROUND

Bovine herpesvirus 5 (BoHV-5) is an alphaherpesvirus responsible for meningoencephalitis in young cattle and it is antigenically and genetically related to bovine herpesvirus 1. BoHV-5 outbreaks are sporadic and restricted in their geographical distribution, being mostly detected in the Southern hemisphere. The N569 and A663 strains are prototypes of the "a" and "b" subtypes of BoHV-5, however, scarce information about their in vitro and in vivo properties is currently available.

METHODS

For the in vitro comparison between BoHV-5 A663 and N569 strains, viral growth kinetics, lysis and infection plaque size assays were performed. Additionally, an experimental infection of cattle with BoHV-5 A663 and N569 strains was carried out. Viral excretion, development of neurological signs, presence of specific antibodies in serum and nasal swabs and presence of latent BoHV-5 DNA in trigeminal ganglion, were analyzed. Histopathological examination of samples belonging to inoculated animals was also performed.

RESULTS

The lytic capacity and the cell-to-cell spread was lower for the A663 strain compared to the N569 strain, however, the production of total infectious viral particles was similar between both strains. Concerning the in vivo properties, the A663 and N569 strains are able to induce similar degrees of pathogenicity in cattle.

CONCLUSIONS

Our results show that the A663 strain used in this study is less adapted to in vitro replication in MDBK cells than the N569 strain and, although slight differences were observed, both strains are able to induce a similar degree of virulence in the natural host.

A recombinant bovine herpesvirus 5 defective in thymidine kinase and glycoprotein E is immunogenic for calves and confers protection upon homologous challenge and BoHV-1 challenge

A recombinant bovine herpesvirus 5 lacking thymidine kinase and glycoprotein E genes (BoHV-5gEΔTKΔ) was evaluated as a live experimental vaccine. In a first experiment, ten-months-old calves were vaccinated intramuscularly (n=9) or remained as controls (n=8) and 42 days later were challenged with BoHV-5 or BoHV-1 intranasally. The four control calves challenged with BoHV-5 developed severe depression and neurological signs and were euthanized in extremis at days 13 and 14 pos-infection (pi); the five vaccinated animals challenged with BoHV-5 remained healthy. The titers of virus shedding were reduced (p<0.01) from days 3 to 7 post-infection (pi) in vaccinated animals. Control and vaccinated calves challenged with BoHV-1 presented mild transient respiratory signs; yet the magnitude of virus shedding was reduced (p<0.05) in vaccinated animals (days 5, 9 and 11pi). In a second experiment, young calves (100-120 days-old) were vaccinated (n=15) or kept as controls (n=5) and subsequently challenged with a BoHV-1 isolate. Control calves developed moderate to severe rhinitis and respiratory distress; two were euthanized in extremis at days 5 and 9 pi, respectively. In contrast, vaccinated animals were protected from challenge and only a few developed mild and transient nasal signs. The duration and titers of virus shedding after challenge were reduced (p<0.05) in vaccinated animals comparing to controls. In both experiments, vaccinated animals developed antibodies to gE only after challenge. These results demonstrate homologous and heterologous protection and are promising towards the use of the recombinant BoHV-5gEΔTKΔ in vaccine formulations to control BoHV-5 and BoHV-1 infections.

A recombinant bovine herpesvirus 5 defective in thymidine kinase and glycoprotein E is attenuated and immunogenic for calves

Bovine herpesvirus 5 (BoHV-5) is an important pathogen of cattle in South America and efforts have been made to produce safer and more effective vaccines. In addition to afford protection, herpesvirus vaccines should allow serological differentiation of vaccinated from naturally, latently infected animals. We previously reported the construction and characterization in vitro of a double mutant BoHV-5 (BoHV-5gE/TK Δ) lacking the genes encoding thymidine kinase (tk) for attenuation, and glycoprotein E (gE) as the antigenic marker, as a vaccine candidate strain (Brum et al. 2010a). The present article reports an investigation on the attenuation and immunogenicity of this recombinant in calves. In a first experiment, 80 to 90-day-old seronegative calves (n=6) inoculated intranasally with the recombinant (titer of 10(7.5)TCID50) shed virus in low to moderate titers in nasal secretions for up to 6 days, yet did not develop any respiratory, systemic or neurological signs of infection. At day 30 post-infection (pi) all calves had BoHV-5 specific neutralizing (VN) antibodies in titers of 4 to 8 and were negative for anti-gE antibodies in a commercial ELISA test. Administration of dexamethasone (0.1mg/kg/day during 5 days) to four of these calves at day 42 pi did not result in virus shedding or increase in VN titers, indicating lack of viral reactivation. Secondly, a group of 8-month-old calves (n=9) vaccinated intramuscularly (IM) with the recombinant virus (10(7.5)TCID50/animal) did not shed virus in nasal secretions, remained healthy and developed VN titers from 2 to 8 at day 42 post-vaccination (pv), remaining negative for gE antibodies. Lastly, 21 calves (around 10 months old) maintained under field conditions were vaccinated IM with the recombinant virus (titer of 10(7.3)TCID50). All vaccinated animals developed VN titers from 2 to 16 at day 30 pv. A boost vaccination performed at day 240 pv resulted in a rapid and strong anamnestic antibody response, with VN titers reaching from 16 to 256 at day 14 post-booster. Again, serum samples remained negative for gE antibodies. Selected serum samples from vaccinated animals showed a broad VN activity against nine BoHV-5 and eight BoHV-1 field isolates. These results show that the recombinant virus is attenuated, immunogenic for calves and induces an antibody response differentiable from that induced by natural infection. Thus, the recombinant BoHV-5gE/TKΔ is an adequate candidate strain for a modified live vaccine.

Identificação e diferenciação de herpesvírus bovino tipos 1 e 5 isolados de amostras clínicas no Centro-Sul do Brasil, Argentina e Uruguai (1987-2006)

Os herpesvírus bovino tipos 1 e 5 (BoHV-1; BoHV-5) são genética e antigenicamente muito semelhantes e por isso são indistinguíveis pela maioria dos testes diagnósticos. Como o BoHV-1 tem sido classicamente associado com doença respiratória e genital, os herpesvírus isolados dessas enfermidades têm sido provisoriamente - e às vezes definitivamente - identificados como BoHV-1. Da mesma forma, os casos de infecção neurológica por herpesvírus em bovinos têm sido atribuídos em sua totalidade ao BoHV-5. Este trabalho relata a identificação de 40 amostras de herpesvírus isoladas de diferentes casos clínicos na região Centro-Sul do Brasil, Argentina e Uruguai entre 1987 e 2006, pelo uso de um PCR capaz de diferenciar esses vírus. As amostras identificadas como BoHV-1 (n=16) foram isoladas de doença respiratória (n=3), balanopostite e/ou vulvovaginite (n=3), do sêmen de touros saudáveis (n=5) e de casos doença neurológica (n=5). As amostras virais identificadas como BoHV-5 (n=24) foram em sua maioria isoladas de doença neurológica (n=21), mas também do sêmen de touros saudáveis (n=2) e do baço de um bezerro com doença sistêmica (n=1). Esses resultados demonstram que tanto o BoHV-1 como o BoHV-5 não estão estritamente associados às suas respectivas síndromes clínicas e que podem estar freqüentemente envolvidos em casos clínicos classicamente atribuídos ao outro vírus. Esses achados também reforçam a necessidade de se identificar corretamente os isolados de herpesvírus para um melhor conhecimento da sua patogenia e epidemiologia.

Molecular and antigenic characterization of Brazilian bovine herpesvirus type 1 isolates recovered from the brain of cattle with neurological disease

Bovine herpesviruses type 1 and 5 (BoHV-1 and BoHV-5) are closely related yet differ markedly in their neuropathogenic potential. BoHV-1 isolates have been associated with respiratory and genital disease whereas BoHV-5 has been consistently isolated from neurological infection. We report the characterization of five Brazilian BoHV-1 isolates associated with neurological disease, an unusual finding. All five viruses were isolated from the brain of cattle presenting neurological disease, yet prominent histological encephalitis was not observed in three cases. The isolated viruses were identified as BoHV-1 by a glycoprotein C gene-based PCR able to differentiate BoHV-1 from BoHV-5. The identity of the isolates was confirmed by nucleotide sequencing of the amplicons and by restriction analysis of PCR products from another gC region. Monoclonal antibody binding and cross-neutralization assays with BoHV-1 and BoHV-5 antisera showed a typical BoHV-1 antigenic profile. Lastly, inoculation of rabbits with these five BoHV-1 isolates did not result in neurological disease, contrasting with fatal meningoencephalitis produced by BoHV-5. Thus, the involvement of BoHV-1 in neurological disease of cattle is more frequent than previously reported, indicating the need for fast and precise means of differentiating it from BoHV-5. Likewise, the potential role of BoHV-1 in neurological infection in cattle should be further investigated.

BHV-1 vaccine induces cross-protection against BHV-5 disease in cattle

Protection against BHV-5 disease induced by inactivated BHV-1 or BHV-5 based vaccines was analysed. Two groups of calves were subcutaneously immunized with an inactivated BHV-1 or BHV-5 based vaccine. A third group was not vaccinated and used as control. In the post-vaccination period, we studied the humoral and cellular immune response resulting similar to both groups. The efficacy of the vaccines was tested after intranasal challenge of the calves with a virulent Argentinean BHV-5 isolate (A-663). All control animals developed neurological signs associated with BHV-5 infection and high levels of virus shedding. Calves immunized with the BHV-1 and BHV-5 inactivated vaccines were protected against BHV-5 disease. Our study provides evidence that strongly support the existence of cross-protection between BHV-1 and BHV-5 in calves. Even though this has already been suggested by previous works, this is the first time an exhaustive study of the immune response is performed and typical clinical BHV-5 meningoencephalitis signs are reproduced in an experimental BHV-5 challenge trial.

Partial Protection Induced by a BHV-1 Recombinant Vaccine against Challenge with BHV-5

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.

Neurovirulência e neuroinvasividade de herpesvírus bovinos tipos 1 e 5 em coelhos

Com o objetivo de avaliar a capacidade dos herpesvírus bovinos tipos 1 e 5 (BHV-1 e BHV-5) de invadir e replicar no sistema nervoso central (SNC) (neuroinvasividade), bem como sua capacidade de induzir doença neurológica (neurovirulência), coelhos com 30 a 35 dias de idade foram inoculados com uma amostra do Herpesvírus da Encefalite Bovina (BHV-5; amostra EVI 88/95) ou com amostras de BHV-1 (Los Angeles ou Cooper), pelas vias intratecal (IT) e intranasal (IN). A inoculação da amostra de BHV-5, tanto pela via IT como IN, induziu sinais clínicos neurológicos em 100% (12/12) dos coelhos inoculados. Os exames histopatológicos revelaram um quadro de meningoencefalite não-purulenta multifocal, caracterizada por gliose multifocal e infiltrados perivasculares. O vírus foi isolado de várias áreas do SNC desses animais. As amostras de BHV-1, quando inoculadas pela via IT, não foram neurovirulentas. A amostra Los Angeles de BHV-1, quando administrada pela via IN, induziu sinais respiratórios severos, além de sinais neurológicos em 57% (4/7) dos animais inoculados. Entretanto, o exame histopatológico destes quatro animais revelou vasculite e trombose no pulmão e cérebro, este último apresentando focos de necrose neuronal, porém sem lesões indicativas de encefalite. Isso sugere que os sinais neurológicos foram, provavelmente, conseqüentes a prejuízos no fluxo sangüíneo encefálico, e não a danos neuronais provocados pela inoculação desse vírus. A amostra Cooper de BHV-1, quando inoculada pela via IN, induziu apenas sinais leves de infecção respiratória. Estes resultados indicam que apenas a amostra de BHV-5 foi capaz de invadir e replicar no encéfalo dos coelhos quando inoculada tanto por via IN como IT, apresentando neuroinvasividade e neurovirulência. É possível que estas observações tenham relação com o fato de amostras de BHV-5 freqüentemente causarem encefalites, em contraposição a infecções pelo BHV-1, onde encefalites são raramente observadas.

Caracterização de herpesvírus bovinos tipos 1 (BHV-1) e 5 (BHV-5) com anticorpos monoclonais

O perfil antigênico de 45 herpesvírus (44 de bovinos, sendo seis amostras de referência de BHV-1 e 15 prováveis BHV-1; três amostras de referência de BHV-5 e 20 prováveis BHV-5) e uma amostra de herpesvírus bubalino (BuHV) foi examinado com um painel de anticorpos monoclonais (Acms) produzidos contra antígenos de herpesvírus bovinos. Para os exames, foi utilizada a prova de imunoperoxidase (IPX) sobre cultivos de células infectadas, tendo os Acms como anticorpos primários. A determinação dos padrões de reatividade das amostras de vírus frente aos Acms permitiu a diferenciação entre os tipos 1 e 5. Todas as amostras isoladas de casos de encefalite apresentaram perfil de BHV-5. Quatro amostras de BHV-5 isoladas de áreas geograficamente distintas apresentaram perfís de reatividade diferenciados em relação às demais amostras do tipo 5. Duas amostras de vírus com perfil antigênico de BHV-5 foram isoladas de sêmen de animais infectados. Estes resultados comprovam a utilidade da caracterização antigênica com este painel de Acms na tipagem de amostras de BHV-1 e BHV-5.

Antibodies against bovine herpesvirus (BHV) 5 may be differentiated from antibodies against BHV1 in a BHV1 glycoprotein E blocking ELISA

We examined whether antibodies against bovine herpesvirus (BHV) 5 cross-react with BHV1 antigens and whether they could interfere with BHV1 eradication programmes. Six calves were experimentally infected with different doses of BHV5 strain N569; homologous antibodies were first detectable on day 11 post infection; they cross-reacted in a BHV1 virus neutralisation test, in a BHV1-glycoprotein (g)-B blocking ELISA and in a BHV1-gE ELISA, but not in a BHV1-gE blocking ELISA. This study indicates that, in ongoing BHV1 eradication programmes, based on vaccines that lack gE, BHV5 infections may not lead to false-positive serological reactions in case cattle are tested for BHV1-gE antibodies by the BHV1-gE blocking ELISA; antibodies against BHV5 may be differentiated from antibodies against BHV1. The BHV1-gE blocking ELISA may, therefore, offer opportunities for the serological differentiation between BHV1 and BHV5 infections.

Infecção e enfermidade neurológica pelo herpesvírus bovino tipo 5 (BHV-5): coelhos como modelo experimental

Coelhos são susceptíveis à infecção pelo herpes-vírus bovino tipo 5 (BHV-5) e freqüentemente desenvolvem enfermidade neurológica aguda fatal após inoculação intranasal. A cinética da invasão do sistema nervoso central (SNC) de coelhos pelo BHV-5 foi estudada através de pesquisa de vírus em secções do SNC a diferentes intervalos pós-inoculação. Após inoculação intranasal, o vírus foi inicialmente detectado no bulbo olfatório às 48h, seguido do córtex olfatório às 48/72h. Às 72/96h o vírus foi detectado também no gânglio trigêmeo, ponte e córtex cerebral. Dois experimentos foram realizados para avaliar a importância do sistema olfatório na invasão do SNC de coelhos pelo BHV-5. No primeiro experimento, coelhos foram inoculados com duas amostras do BHV-5 no saco conjuntival. Coelhos inoculados por essa via também desenvolveram a enfermidade neurológica, porém com menor freqüência com curso clínico tardio. No segundo experimento, doze coelhos foram submetidos à ablação cirúrgica do bulbo olfatório e posteriormente inoculados com o BHV-5 pela via intranasal. Onze de 12 coelhos controle (91,6%), não submetidos à cirurgia, desenvolveram a doença neurológica, contra quatro de 12 (33,3%) dos animals submetidos à remoção cirúrgica do bulbo olfatório. Esses resultados demonstram que o sistema olfatório constitui-se na principal via de acesso do BHV-5 ao encéfalo de coelhos após inoculação intranasal. No entanto, o desenvolvimento de infecção neurológica em coelhos inoculados pela via conjuntival e em coelhos sem o bulbo olfatório indica que o BHV-5 pode utilizar outras vias para invadir o SNC, provavelmente as fibras sensoriais e autonômicas que compõe o nervo trigêmeo. Os efeitos da imunização com vírus homólogo (BHV-5) e heterólogo (BHV-1) na proteção à infecção neurológica foram investigados. Cinco entre 10 coelhos (50%) imunizados com o BHV-5 apresentaram sinais neurológicos discretos e transitórios e um morreu após o desafio com o BHV-5. Curiosamente, o grau de proteção foi superior nos coelhos imunizados com o BHV-1: apenas dois animais apresentaram sinais clínicos passageiros e recuperaram-se. Portanto, proteção da enfermidade neurológica pelo BHV-5 em coelhos pode ser obtida por imunização com o BHV-5 ou BHV-1, provavelmente devido à extensa reatividade sorológica cruzada entre esses vírus. Estudos adicionais em coelhos podem auxiliar no esclarecimento da patogênese e resposta imunológica a infecção pelo BHV-5.

Experimental infection of sheep with bovine herpesvirus type-5 (BHV-5): acute and latent infection

We demonstrated that sheep are susceptible to acute and latent infection by bovine herpesvirus type-5 (BHV-5). Lambs inoculated intranasally with two South American BHV-5 isolates replicated the virus with titers up to 10(7.1) TCID50/ml for up to 15 days and showed mild signs of rhinitis. Four lambs in contact with the inoculated animals acquired the infection and excreted virus for up to seven days. One lamb developed progressive signs of neurological disease and was euthanized in extremis. Clinical signs consisted of tremors of the face, bruxism, ptyalism, incoordination, lateral flexion of the neck and head, circling, walking backwards, recumbency and paddling. The virus was detected in the anterior and posterior cerebrum, dorso- and ventro-lateral cortex, cerebellum, pons, midbrain and olfactory bulb. Viral nucleic acids were demonstrated in neurons and astrocytes of the anterior and ventro-lateral cortex by in situ hybridization. Histological changes consisting of non-suppurative meningitis, perivascular mononuclear cuffing, focal gliosis, neuronal necrosis and intranuclear inclusions were observed in the anterior cerebrum, ventro-lateral cortex and midbrain. Dexamethasone treatment at Day 50 pi resulted in reactivation of the latent infection and virus shedding in 13/16 (81%) of the lambs. Together with previous reports of BHV-5 antibodies in sheep, these findings show that sheep are fully susceptible to BHV-5 suggesting that infection by BHV-5 in sheep may occur naturally.

Pathogenesis of meningoencephalitis in rabbits by bovine herpesvirus type-5 (BHV-5)

This article describes the main aspects of bovine herpesvirus type-5 (BHV-5) neurologic infection and disease in rabbits, a candidate animal model for studying BHV-5 neuropathogenesis. Intranasal inoculation of weanling rabbits with a Brazilian BHV-5 isolate produced neurological disease and death in 78.8% (26/33) of the animals. Neurological signs started as early as 5 days post-inoculation and lasted from 10-12 hours up to several days. Most animals evolved to a moribund state or death within 24 (69.2%) to 48 hours (88.5%). Neurological disease was characterized by excitability or depression, tremors, bruxism, walking or running in circles, backward arching of the head and body, incoordination, backward and sideways falling, paddling, profound depression and death. Moderate levels of infectivity were detected in several areas of the brain, most consistently in the ventro-lateral hemisphere (in 16 out of 20 animals), anterior cerebrum (15/20), midbrain (11/20), dorso-lateral hemisphere (10/20) and pons (12/26). Infectious virus was also recovered from the olfactory bulb (9/20), medulla oblongata (10/26), cerebellum (7/20), posterior cerebrum (5/20) and trigeminal ganglia (4/20). No gross lesions were observed. Microscopic lesions were mild and consisted of non-suppurative meningitis, mononuclear perivascular cuffing and focal gliosis. These changes were observed most consistently in the ventro-lateral hemisphere and anterior cerebrum. Passive immunity partially protected rabbits from BHV-5-induced encephalitis. Rabbits born to immunized dams showed a significative delay in the onset of clinical disease and reduced morbidity and mortality rates compared to rabbits born to unvaccinated dams. These results demonstrate that BHV-5-induced neurological disease can consistently be reproduced in rabbits and point towards the use of this species as an animal model to study BHV-5 neuropathogenesis.

Infecção aguda e latente em ovinos inoculados com o herpesvírus bovino tipo 5 (BHV-5)

Infecção experimental de ovinos com o herpesvírus bovino tipo 5 (BHV-5) reproduziu vários aspectos da infecção pelo BHV-5 em bovinos. Inoculação intranasal foi seguida de extensiva replicação viral na cavidade nasal, excreção e transmissão do vírus a outros animais, estabelecimento e reati-vação de latência, e o desenvolvimento de meningoencefalite clínica em um animal. Ovinos inoculados com a amostra brasileira EVI-88 apresentaram hipertermia transitória, hiperemia da mucosa nasal e corrimento nasal de seroso a muco-purulento. Os animais eliminaram vírus em secreções nasais em títulos de até 107,11DICC50/ml por até 16 dias. Um cordeiro apresentou sinais clínicos de encefalite no dia 10 pós-inoculação, sendo sacrificado in extremis no início do dia 13. Infectividade foi detectada em várias regiões do encéfalo desse animal, incluindo os hemisférios anterior e posterior, córtex dorso- e ventro-lateral, ponte, pedúnculo cerebral, cerebelo e bulbo olfatório. Alterações histológicas foram observadas em várias regiões do encéfalo, principalmente no hemisfério anterior, córtex ventro-lateral e pedúnculos cerebrais, e consistiram de meningite mononuclear, manguitos perivasculares, gliose focal, necrose e inclusões intranucleares em neurônios . Quatro ovinos mantidos como sentinelas adquiriram a infecção e eliminaram vírus a partir do final do segundo dia, até 7 dias. Ovinos inoculados com a amostra argentina A663 apresentaram apenas hiperemia e umidecimento da mucosa nasal, embora eliminassem vírus nas secreções nasais por até 15 dias. Tratamento dos animais com dexametasona a partir do dia 50 pós-inoculação provocou reativação da infecção latente e eliminação viral durante até 11 dias por 76,9% (10/13) dos animais inoculados e por 100% (3/3) dos animais sentinela. Esses resultados demonstram que ovinos são susceptíveis à infecção aguda e latente pelo BHV-5 e sugerem que infecções naturais de ovinos por este vírus podem potencialmente ocorrer. Ness sentido, uma possível participação da espécie ovina como reservatório natural desse vírus deve ser melhor investigada.

Monoclonal antibodies that distinguish between encephalitogenic bovine herpesvirus type 1.3 and respiratory bovine herpesvirus type 1.1

Seven mouse hybridoma cell lines producing monoclonal antibodies (MAb) against an encephalitogenic strain of bovine herpesvirus type 1.3 (BHV-1.3) were established. The clones producing MAb were selected to be specific for BHV-1.3 by enzyme-linked immunosorbent assay. Only L1B neutralized virus without complement. With the addition of complement, five of the MAb neutralized BHV-1.3 but not the respiratory strain BHV-1.1. The anti-BHV-1.3-specific MAb Q10B, L6G, and L1B precipitated glycoproteins from BHV-1.3 that were analogous to the gI, GIII, and gIV glycoproteins of BHV-1.1, respectively. The other four MAb precipitated unknown proteins. None of the anti-BHV-1.3 MAb precipitated BHV-1.1 glycoproteins. The majority of the anti-BHV-1.3 MAb did not react with BHV-1.1 by immunoblotting, but O7E (unknown protein pattern by radioimmunoprecipitation) was reactive with five proteins (M(r)s of 33,000, 43,000, 70,000, 141,000, and 190,000) of BHV-1.3 and with a different pattern of proteins of BHV-1.1 (M(r)s of 30,000, 38,000, 83,000 and 144,000). Two of the MAb, L6G and O7E, conjugated with peroxidase were found to be useful for detecting BHV-1.3 antigen by immunochemistry in Formalin-fixed brain tissue from experimentally infected calves.