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

Abstract

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 TCID 50 ) 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 TCID 50 /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 TCID 50 ). 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 RESUMO.-[Cepa recombinante do herpesvírus bovino tipo 5 defectiva na timidina quinase e glicoproteína E é atenuada e imunogênica para bezerros.] O herpesví-rus bovino tipo 5 (BoHV-5) é um importante patógeno de bovinos na América do Sul e tem suscitado esforços para o desenvolvimento de vacinas mais seguras e eficazes. Além de conferirem proteção, vacinas contra os herpesví-rus animais devem permitir a diferenciação sorológica entre animais vacinados e infectados naturalmente. Foi recentemente relatada a construção e caracterização in vitro de um recombinante do BoHV-5 defectivo na enzima timidina quinase (tk) para atenuação e, na glicoproteína E (gE) como marcador antigênico, como potencia...

Reativação e distribuição do DNA latente do herpesvírus bovino tipo 5 no encéfalo de ovinos infectados experimentalmente

“…O fenótipo desses recombinantes tem sido estudado em coelhos (Silva et al 2010) e em bezerros (Santos et al 2010). Os recombinantes defectivos na gE, TK e ambos gE/TK também tem sido avaliados como candidatos a cepas vacinais (Anziliero et al 2011). Assim, um modelo animal teria uma grande utilidade para estudos de fenótipos de recombinantes do BoHV-5 defectivos em genes especíϐicos; (iii) a maior proximidade ϐilogenéti-ca entre ovinos e bovinos, hospedeiros naturais do BoHV-5.…”

A glycoprotein E gene-deleted bovine alphaherpesvirus 1 strain is attenuated and immunogenic for calves with passive immunity upon intranasal immunization

“…The daily clinical score of each group consisted of the mean of individual clinical scores. The clinical scoring was adapted from a previous study (ANZILIERO et al, 2011).…”