Spatiotemporal regulation of type I interferon expression determines the antiviral polarization of CD4+ T cells.

Differentiation of CD4+ T cells into either follicular helper T (TFH) or type 1 helper T (TH1) cells influences the balance between humoral and cellular adaptive immunity, but the mechanisms whereby pathogens elicit distinct effector cells are incompletely understood. Here we analyzed the spatiotemporal dynamics of CD4+ T cells during infection with recombinant vesicular stomatitis virus (VSV), which induces early, potent neutralizing antibodies, or recombinant lymphocytic choriomeningitis virus (LCMV), which induces a vigorous cellular response but inefficient neutralizing antibodies, expressing the same T cell epitope. Early exposure of dendritic cells to type I interferon (IFN), which occurred during infection with VSV, induced production of the cytokine IL-6 and drove TFH cell polarization, whereas late exposure to type I IFN, which occurred during infection with LCMV, did not induce IL-6 and allowed differentiation into TH1 cells. Thus, tight spatiotemporal regulation of type I IFN shapes antiviral CD4+ T cell differentiation and might instruct vaccine design strategies.

Oncolytic Recombinant Vesicular Stomatitis Virus (VSV) Is Nonpathogenic and Nontransmissible in Pigs, a Natural Host of VSV.

Vesicular stomatitis virus (VSV) is a negative-stranded RNA virus that naturally causes disease in livestock including horses, cattle and pigs. The two main identified VSV serotypes are New Jersey (VSNJV) and Indiana (VSIV). VSV is a rapidly replicating, potently immunogenic virus that has been engineered to develop novel oncolytic therapies for cancer treatment. Swine are a natural host for VSV and provide a relevant and well-established model, amenable to biological sampling to monitor virus shedding and neutralizing antibodies. Previous reports have documented the pathogenicity and transmissibility of wild-type isolates and recombinant strains of VSIV and VSNJV using the swine model. Oncolytic VSV engineered to express interferon-beta (IFNß) and the sodium iodide symporter (NIS), VSV-IFNß-NIS, has been shown to be a potent new therapeutic agent inducing rapid and durable tumor remission following systemic therapy in preclinical mouse models. VSV-IFNß-NIS is currently undergoing clinical evaluation for the treatment of advanced cancer in human and canine patients. To support clinical studies and comprehensively assess the risk of transmission to susceptible species, we tested the pathogenicity and transmissibility of oncolytic VSV-IFNß-NIS using the swine model. Following previously established protocols to evaluate VSV pathogenicity, intradermal inoculation with 107 TCID50 VSV-IFNß-NIS caused no observable symptoms in pigs. There was no detectable shedding of infectious virus in VSV-IFNß-NIS in biological excreta of inoculated pigs or exposed naive pigs kept in direct contact throughout the experiment. VSV-IFNß-NIS inoculated pigs became seropositive for VSV antibodies, while contact pigs displayed no symptoms of VSV infection, and importantly did not seroconvert. These data indicate that oncolytic VSV is both nonpathogenic and not transmissible in pigs, a natural host. These findings support further clinical development of oncolytic VSV-IFNß-NIS as a safe therapeutic for human and canine cancer.

Subcapsular sinus macrophages prevent CNS invasion on peripheral infection with a neurotropic virus.

Lymph nodes (LNs) capture microorganisms that breach the body's external barriers and enter draining lymphatics, limiting the systemic spread of pathogens. Recent work has shown that CD11b(+)CD169(+) macrophages, which populate the subcapsular sinus (SCS) of LNs, are critical for the clearance of viruses from the lymph and for initiating antiviral humoral immune responses. Here we show, using vesicular stomatitis virus (VSV), a relative of rabies virus transmitted by insect bites, that SCS macrophages perform a third vital function: they prevent lymph-borne neurotropic viruses from infecting the central nervous system (CNS). On local depletion of LN macrophages, about 60% of mice developed ascending paralysis and died 7-10 days after subcutaneous infection with a small dose of VSV, whereas macrophage-sufficient animals remained asymptomatic and cleared the virus. VSV gained access to the nervous system through peripheral nerves in macrophage-depleted LNs. In contrast, within macrophage-sufficient LNs VSV replicated preferentially in SCS macrophages but not in adjacent nerves. Removal of SCS macrophages did not compromise adaptive immune responses against VSV, but decreased type I interferon (IFN-I) production within infected LNs. VSV-infected macrophages recruited IFN-I-producing plasmacytoid dendritic cells to the SCS and in addition were a major source of IFN-I themselves. Experiments in bone marrow chimaeric mice revealed that IFN-I must act on both haematopoietic and stromal compartments, including the intranodal nerves, to prevent lethal infection with VSV. These results identify SCS macrophages as crucial gatekeepers to the CNS that prevent fatal viral invasion of the nervous system on peripheral infection.

Experimental infection of Didelphis marsupialis with vesicular stomatitis New Jersey virus.

Although vesicular stomatitis has been present for many years in the Americas, many aspects of its natural history remain undefined. In this study, we challenged five adult Virginia opossums (Didelphis marsupialis) with vesicular stomatitis New Jersey serotype virus (VSNJV). Opossums had no detectable antibodies against VSNJV prior to being inoculated with 10(6.5) median tissue culture infective doses (TCID(50)) of VSNJV by two routes; intraepithelial/subepithelial (IE/SE) inoculation and scarification in the muzzle (SM). Clinical response was monitored daily and animals were tested for viral shedding. All infected animals developed vesicles and ulcers on the tongue and inflammation of the nasal alar folds. Virus was isolated from esophagus-pharynx, nasal, and from ocular swabs and lesions samples. The failure to detect viremia in these animals indicates that a source other than blood may be required for transmission to insect vectors. Our results suggest that D. marsupialis could play a role in the maintenance of VSNJV outside of domestic animal populations and could provide a model to study vesicular stomatitis virus pathogenesis.