Sendai virus induces protective immune responses in ovine cells

Abstract

Introduction Small Ruminant Lentiviruses (SRLV) affect the production and health of sheep and goats in the absence of therapeutic or prophylactic measures. Immunization strategies assayed so far employing recombinant proteins, attenuated virus or DNA have induced adaptive immune responses, but faint levels of protection were achieved. Sendai virus (SeV)-engineered vectors are strong inducers of innate antiviral responses and recombinant vaccines are being tested against human lentivirus infection. Here, we use a SeV non-replicative vector expressing GFP to infect different ovine cell types. Induced activation and resistance to a subsequent SRLV infection were evaluated. Material & Methods Ovine skin fibroblasts (OSF), alveolar macrophages (AM) and blood-derived macrophages (BDM) were infected with a SeV-GFP vector (Dr. Garcin, University of Geneva) at different MOI. Infectivity was evaluated under fluorescence microscopy and by flow cytometry. OSF and BDM isolated from uninfected animals were infected in vitro at a MOI of 0.5. Instead, AM were isolated from SRLV naturally infected animals. SRLV infectivity was quantified by q-PCR and RT activity (SG-PERT). mRNA transcript levels were evaluated by RT-PCR. Results The SeV-GFP vector infected all ovine cells very efficiently reaching 100% of GFP-positive events. Macrophage polarization towards the proinflammatory pathway was evidenced. SRLV infection was restricted in naturally infected AM as well as in experimentally infected BDM and OSF. However, restriction pattern differed among cell types. While BDM exhibited a preintegration blockade, OSF showed reduced virus production without affecting viral DNA or RNA. Accordingly, increased mRNA expression of restriction factors acting at pre-integration steps in BDM and those acting after integration in OSF was found upon SeV-GFP infection. Furthermore, supernatants from AM infected with the SeV-GFP vector contained detectable levels of type-I IFN that restricted viral infection in subsequent infection cycles. Discussion & Conclusion The SeV-GFP vector infected ovine cells very efficiently and programmed them to an antiviral state preventing SRLV infection in myeloid or fibroblastic cells, respectively. This antiviral state was characterized by the induction of type-I IFN responses likely exerting paracrine as well as wide-spectrum responses, useful in SRLV control programs.