Tissue-specific transcription profile of cytokine and chemokine genes associated with flavivirus control and non-lethal neuropathogenesis in rabbits

We previously showed that New Zealand White (NZWRs) and cottontail rabbits (CTRs) are a suitable model for studying immune mechanisms behind virus control and non-lethal neuropathogenesis associated with West Nile virus (WNV) and Murray Valley encephalitis virus (MVEV) infections. In the current study, we observed that MVEV infection induced high IFNα, TNFα, IL6, and CXCL10 transcript levels in the brains of weanling NZWRs, unlike infection with the less virulent WNVNSW2011. These transcript levels also correlated with encephalitis severity. Widespread STAT1 protein expression in brain with moderate neuropathology suggests that IFN-I signaling is crucial for limiting neural infection and mediating non-lethal neuropathogenesis. Unlike NZWRs, CTRs limit neuroinvasion without upregulation of many cytokine/chemokine transcripts, suggesting a species-dependent virus control mechanism. However, the common IFNγ, TNFα and IL6 transcript upregulation in specific lymphoid organs suggest some conserved elements in the response against flaviviruses, unique to all rabbits

Transcriptome of peripheral blood mononuclear cells in West Nile virus infection of horses and rabbits

Following severe flooding in eastern Australia in 2011 an equine West Nile virus (WNV) induced encephalitis epidemic ensued with ~1000 horses affected and mortality of 10-15%. A new strain, WNVNSW2011 was isolated. Infections with WNV are mostly (>80%) mild to subclinical, likely because of a virus-limiting innate response in the peripheral blood leukocytes and draining lymph nodes. Therefore, we have investigated the transcripts of peripheral blood mononuclear cells (PBMCs) that might restrict the virus as the first line defence. PBMCs were collected from intra-dermally WNVNSW2011-infected rabbits (n=12) and horses (n=3) on the day before infection (D-1), and various days post infection (DPI). Blood cells were also collected from control (n=3) rabbits and horses. Transcripts of interest including cytokines, Toll-like receptors (TLR), and TLR-associated downstream genes were quantified using quantitative RT- PCR. Interferon α & β, IL6, IL22, CXCL10, PTX3, TLR1, TLR3, TLR6, STAT1, MyD88, TRAF3, IRF7, IRF9, IFIT2, and NOD2 mRNA expressions were upregulated on 1 DPI, and TLR3 and IRF3 remained highly upregulated till 3 DPI in rabbits. IFNα & β, IL22, PTX3, TLR7 mRNA expression was upregulated on days 1-7 DPI in horses. TLR1-3, TLR8 & TRAF3 mRNA expression was upregulated between 11-18 DPI, while MyD88, STST1, STAT2 & ISG15 mRNA expression was upregulated at 7 DPI in horses. Both infection pathobiology in vivo, and transcriptome responses of PBMCs to WNV infection in vitro already established rabbit as an appropriate model for subclinical WNV-infection1-6. This study further showed that transcriptome kinetics of experimentally infected-rabbit PBMC were similar to that of horse cells. Furthermore, immediate recognition of virus by TLRs and rapid response of IFNs might be the limiting peripheral cellular factors contributing in subclinical features of the Australian WNV-strain

Essential oil spray reduces clinical signs of insect bite hypersensitivity in horses

To assess the efficacy of an herbal spray combining various essential oils, with a claim of mast cell stabilisation, antipruritic, anti-inflammatory, and insect repellent effects on the clinical presentation of insect bite hypersensitivity (IBH) in horses.Double-blinded, placebo-controlled, randomised, cross-over clinical trial.Twenty adult horses with clinical IBH were treated with a daily application of herbal spray or placebo for 28 days in a randomised, cross-over fashion, separated by a>28-day washout period. Horses were examined and scored prior to and after the completion of each treatment. Histopathology was performed on four horses. Owners kept daily diaries of observations.The herbal spray significantly reduced the severity of all assessed parameters (pruritus, excoriations, lichenification and alopecia; P < 0.05) compared with baseline values (pretreatment) and with placebo. Owners reported improvement of pruritus in 19/20 horses (95%) with complete resolution in 17 horses (85%) following treatment. Skin biopsies showed resolution of orthokeratosis in 4/4 horses, reduced thickness of the stratum spinosum in 2/4 horses and complete resolution of histopathological abnormalities in 1/4 horses after treatment, compared with either no change or deterioration of histopathologic lesions after placebo. No side effects were observed.The tested herbal spray may be an effective treatment for the management of equine IBH

A chimeric vaccine protects farmed saltwater crocodiles from West Nile virus-induced skin lesions

West Nile virus (WNV) causes skin lesions in farmed crocodiles leading to the depreciation of the value of their hides and significant economic losses. However, there is no commercially available vaccine designed for use in crocodilians against WNV. We tested chimeric virus vaccines composed of the non-structural genes of the insect-specific flavivirus Binjari virus (BinJV) and genes encoding the structural proteins of WNV. The BinJV/WNV chimera, is antigenically similar to wild-type WNV but replication-defective in vertebrates. Intramuscular injection of two doses of BinJV/WNV in hatchling saltwater crocodiles (Crocodylus porosus) elicited a robust neutralising antibody response and conferred protection against viremia and skin lesions after challenge with WNV. In contrast, mock-vaccinated crocodiles became viraemic and 22.2% exhibited WNV-induced lesions. This suggests that the BinJV/WNV chimera is a safe and efficacious vaccine for preventing WNV-induced skin lesions in farmed crocodilians

Characterization of non-lethal West Nile Virus (WNV) infection in horses: Subclinical pathology and innate immune response

Most natural West Nile virus (WNV) infections in humans and horses are subclinical or sub-lethal and non-encephalitic. Yet, the main focus of WNV research remains on the pathogenesis of encephalitic disease, mainly conducted in mouse models. We characterized host responses during subclinical WNV infection in horses and compared outcomes with those obtained in a novel rabbit model of subclinical WNV infection (Suen et al. 2015. Pathogens, 4: 529). Experimental infection of 10 horses with the newly emerging WNV-strain, WNVNSW2011, did not result in neurological disease in any animal but transcriptional upregulation of both type I and II interferon (IFN) was seen in peripheral blood leukocytes prior to or at the time of viremia. Likewise, transcript upregulation for IFNs, TNFα, IL1β, CXCL10, TLRs, and MyD88 was detected in lymphoid tissues, while IFNα, CXCL10, TLR3, ISG15 and IRF7 mRNA was upregulated in brains with histopathological evidence of mild encephalitis, but absence of detectable viral RNA or antigen. These responses were reproduced in the New Zealand White rabbits (Oryctolagus cuniculus) experimentally infected with WNVNSW2011, by intradermal footpad inoculation. Kinetics of the anti-WNV antibody response was similar in horses and rabbits, which for both species may be explained by the early IFN and cytokine responses evident in circulating leukocytes and lymphoid organs. Given the similarities to the majority of equine infection outcomes, immunocompetent rabbits appear to represent a valuable small-animal model for investigating aspects of non-lethal WNV infections, notably mechanisms involved in abrogating morbidity