Effects of recombinant ovine interferon-tau on ovine lentivirus replication and progression of disease

The antiviral effects of recombinant ovine interferon-tau (roIFN-tau) were studied in 26 lambs inoculated with ovine lentivirus (OvLV) or mock-infecte d. Six of the OvLV-infected lambs and three of the mock-infected lambs were treated with 10(6) antiviral units (AVU) per kg roIFN-tau daily for 30 day s starting at day 0 post-inoculation (p.i.) and twice a week thereafter (ea rly treatment). Six of the OvLV-infected lambs and three of the mock-infect ed lambs were treated with 10(6) AVU/kg roIFN-tau daily for 30 days startin g at day 150 p.i. and twice a week thereafter (late treatment). Six OvLV-in fected and two mock-infected lambs were treated either early or late with p lacebo. Cell-associated viraemia was quantified by an end-point dilution me thod. The weekly antibody response against OvLV proteins was studied by ELI SA. All experimental animals were killed at 27 weeks p.i. and histological sections of lung were scored for the degree of lymphoid interstitial pneumo nia (LIP). A 90% reduction in OvLV titres was detected at 4 weeks post-trea tment in lambs that received early roIFN-tau treatment (P < 0.01). Differen ces in virus titres were also found at weeks 2 and 6 (P < 0.05). Scores for LIP degree were higher in infected lambs treated with placebo or late roIF N-tau than in the mock-infected lambs or in the infected lambs that receive d early roIFN-tau (P < 0.05). LIP scores were not different between mock-in fected lambs and infected lambs that received early roIFN-tau. These result s indicate that roIFN-tau curtails OvLV replication in vivo and reduces the likelihood of development of lentivirus-induced LIP when infected lambs ar e treated during the initial phases of OvLV infection.