Disease manifestations of canine distemper virus infection in ferrets are modulated by vitamin A status

Ferret Pediatrics

Ferrets are bred to be pets, utilized for hunting, and as laboratory models. Despite the fact that ferrets in some areas of the world are neutered by the breeder before entering the pet trade, the importance of pediatric management should not be overlooked. Pregnant, whelping, and lactating jills should be closely monitored and kept in a quiet, stress-free environment. Hand-rearing baby kits is very challenging due to their requirement for ferret milk. Minimizing maternal stress and disease can prevent the need to hand rear kits. Infectious diseases in juvenile ferrets include canine distemper virus, rotavirus, coccidiosis, feline panleukopenia virus (experimental only), and Toxoplasma-like disease. All juvenile ferrets should be vaccinated against canine distemper and rabies. Congenital diseases are reported to affect the auditory, ocular, cardiovascular, urogenital, central nervous, and musculoskeletal systems. Early detection of these diseases is important to prevent the progression of curable diseases.

Death comes for us all: relating movement-integrated habitat selection and social behavior to human-associated and disease-related mortality among gray wolves

Avoiding death affects biological processes, including behavior. Habitat selection, movement, and sociality are highly flexible behaviors that influence the mortality risks and subsequent fitness of individuals. In the Anthropocene, animals are experiencing increased risks from direct human causes and increased spread of infectious diseases. Using integrated step selection analysis, we tested how the habitat selection, movement, and social behaviors of gray wolves vary in the two months prior to death due to humans (being shot or trapped) or canine distemper virus (CDV). We further tested how those behaviors vary as a prelude to death. We studied populations of wolves that occurred under two different management schemes: a national park managed for conservation and a provincially managed multi-use area. Behaviors that changed prior to death were strongly related to how an animal eventually died. Wolves killed by humans moved slower than wolves that survived and selected to be nearer roads closer in time to their death. Wolves that died due to CDV moved progressively slower as they neared death and reduced their avoidance of wet habitats. All animals, regardless of dying or living, maintained selection to be near packmates across time, which seemingly contributed to disease dynamics in the packs infected with CDV. There were no noticeable differences in behavior between the two management areas. Overall, habitat selection, movement, and sociality interact to put individuals and groups at greater risks, influencing their cause-specific mortality.

First demonstration of giant panda's immune response to canine distemper vaccine

The Canine Distemper Virus (CDV) is a high fatal virus to the giant panda (Ailuropoda melanoleuca), where CDV vaccination is a key preventative measure in captive giant pandas. However, the immune response of giant pandas to CDV vaccination has been little studied. In this study, we investigated the blood transcriptome expression profiles of five giant panda cubs after three inoculations, 21 days apart. Blood samples were collected before vaccination (0 Day), and 24 h after each of the three inoculations; defined here as 1 Day, 21  Day, and 42  Day. Compared to 0 Day, we obtained 1262 differentially expressed genes (DEGs) during inoculations. GO and KEGG pathways enrichment analysis of these DEGs found 222 GO terms and 40 pathways. The maximum immune-related terms were enriched by DEGs from comparisons of 21  Day and 0 Day. In the PPI analysis, we identified RSAD2, IL18, ISG15 immune-related hub genes from 1 Day and 21 Day comparison. Compared to 0 Day, innate immune-related genes, TLR4 and TLR8, were up-regulated at 1 Day, and the expressions of IRF1, RSAD2, MX1, and OAS2 were highest at 21  Day. Of the adaptive immune-related genes, IL15, promoting T cell differentiation into CD8⁺T cells, was up-regulated after the first two inoculations, IL12β, promoting T cell differentiation into memory cells, and IL10, promoting B cell proliferation and differentiation, were down-regulated during three inoculations. Our results indicated that the immune response of five giant panda cubs was strongest after the second inoculation, most likely protected against CDV infection through innate immunity and T cells, but did not produce enough memory cells to maintain long-term immunity after CDV vaccination.

In vitro inhibition of mumps virus by retinoids

BACKGROUND

Mumps virus (MuV) is a highly infectious paramyxovirus closely related to measles virus (MeV). Despite the availability of a mumps vaccine, outbreaks continue to occur and no treatment options are available. Vitamin A and other naturally occurring retinoids inhibit the replication of MeV in vitro.

METHODS

Anti-viral effects of retinoids were observed in cell culture using the myelomonocytic U937, NB4/R4, and Huh7/7.5 cells. Observations of anti-viral effect were quantified using TCID50 analysis. Molecular properties of the antiviral effect were analysed using quantitative RT-PCR and western blot.

RESULTS

The current work demonstrates that retinoids inhibit MuV in vitro due to up-regulation of type I interferon (IFN) and IFN stimulated genes. This effect is mediated by nuclear retinoid receptor signalling and RIG-I is required. The antiviral retinoid-induced state makes cells less permissive to viral replication from subsequent challenge with either MuV or MeV for less than 12 hours.

CONCLUSIONS

These results demonstrate that retinoids inhibit MuV replication in uninfected bystander cells through a retinoid inducible gene I (RIG-I), retinoic acid receptor (RAR) and IFN dependent manner making them refractory to subsequent rounds of viral replication. These observations raise the possibility that pharmacological doses of retinoids might have clinical benefit in MuV infection.

In vitro inhibition of canine distemper virus by flavonoids and phenolic acids: implications of structural differences for antiviral design

Infection caused by canine distemper virus (CDV) is a highly contagious disease with high incidence and lethality in the canine population. Antiviral activity of flavonoids quercetin, morin, rutin and hesperidin, and phenolic cinnamic, trans-cinnamic and ferulic acids were evaluated in vitro against the CDV using the time of addition assay to determine which step of the viral replicative cycle was affected. All flavonoids displayed great viral inhibition when they were added at the times 0 (adsorption) and 1h (penetration) of the viral replicative cycle. Both quercetin and hesperidin presented antiviral activity at the time 2h (intracellular). In the other hand, cinnamic acid showed antiviral activity at the times 0 and 2h while trans-cinnamic acid showed antiviral effect at the times -1h (pre-treatment) and 0 h. Ferulic acid inhibited CDV replicative cycle at the times 0 and 1h. Our study revealed promising candidates to be considered in the treatment of CDV. Structural differences among compounds and correlation to their antiviral activity were also explored. Our analysis suggest that these compounds could be useful in order to design new antiviral drugs against CDV as well as other viruses of great meaning in veterinary medicine.

RIG-I is required for the inhibition of measles virus by retinoids

Vitamin A can significantly decrease measles-associated morbidity and mortality. Vitamin A can inhibit the replication of measles virus (MeV) in vitro through an RARα- and type I interferon (IFN)-dependent mechanism. Retinoid-induced gene I (RIG-I) expression is induced by retinoids, activated by MeV RNA and is important for IFN signaling. We hypothesized that RIG-I is central to retinoid-mediated inhibition of MeV in vitro. We demonstrate that RIG-I expression is increased in cells treated with retinoids and infected with MeV. The central role of RIG-I in the retinoid-anti-MeV effect was demonstrated in the Huh-7/7.5 model; the latter cells having non-functional RIG-I. RAR-dependent retinoid signaling was required for the induction of RIG-I by retinoids and MeV. Retinoid signaling was also found to act in combination with IFN to induce high levels of RIG-I expression. RIG-I promoter activation required both retinoids and MeV, as indicated by markers of active chromatin. IRF-1 is known to be regulated by retinoids and MeV, but we found recruitment of IRF-1 to the RIG-I promoter by retinoids alone. Using luciferase expression constructs, we further demonstrated that the IRF-1 response element of RIG-I was required for RIG-I activation by retinoids or IFN. These results reveal that retinoid treatment and MeV infection induces significant RIG-I. RIG-I is required for the retinoid-MeV antiviral response. The induction is dependent on IFN, retinoids and IRF-1.

Variation in European harbour seal immune response genes and susceptibility to phocine distemper virus (PDV)

Phocine distemper virus (PDV) has caused two mass mortalities of European harbour seals (Phoca vitulina) in recent decades. Levels of mortality varied considerably among European populations in both the 1988 and 2002 epidemics, with higher mortality in continental European populations in comparison to UK populations. High levels of genetic differentiation at neutral makers among seal populations allow for the possibility that there could be potential genetic differences at functional loci that may account for some of the variation in mortality. Recent genome sequencing of carnivore species and development of genomic tools have now made it possible to explore the possible contribution of variation in candidate genes from harbour seals in relation to the differential mortality patterns. We assessed variation in eight genes (CD46, IFNG, IL4, IL8, IL10, RARa, SLAM and TLR2) encoding key proteins involved in host cellular interactions with Morbilliviruses and the relationship of variants to disease status. This work constitutes the first genetic association study for Morbillivirus disease susceptibility in a non-model organism, and for a natural mortality event. We found no variation in harbour seals from across Europe in the protein coding domains of the viral receptors SLAM and CD46, but SNPs were present in SLAM intron 2. SNPs were also present in IL8 p2 and RARa exon 1. There was no significant association of SLAM or RARa polymorphisms with disease status implying no role of these genes in determining resistance to PDV induced mortality, that could be detected with the available samples and the small number of polymorphisms indentified. However there was significant differentiation of allele frequencies among populations. PDV and other morbilliviruses are important models for wildlife epidemiology, host switches and viral evolution. Despite a negative result in this case, full sequencing of pinniped and other 'non-model' carnivore genomes will help in refining understanding the role of host genetics in disease susceptibility for these viruses.

Measles virus infection of the CNS: human disease, animal models, and approaches to therapy

Viral infections of the central nervous system(CNS) mostly represent clinically important, often life-threatening complications of systemic viral infections. After acute measles, CNS complications may occur early (acute postinfectious measles encephalitis, APME) or after years of viral persistence (subacute sclerosing panencephalitis, SSPE). In spite of a presumably functional cell-mediated immunity and high antiviral antibody titers, an immunological control of the CNS infection is not achieved in patients suffering from SSPE. There is still no specific therapy for acute complications and persistent MV infections of the CNS. Hamsters, rats, and (genetically unmodified and modified) mice have been used as model systems to study mechanisms of MV-induced CNS infections. Functional CD4+ and CD8+ T cells together with IFN-gamma are required to overcome the infection. With the help of recombinant measles viruses and mice expressing endogenous or transgenic receptors, interesting aspects such as receptor-dependent viral spread and viral determinants of virulence have been investigated. However, many questions concerning the lack of efficient immune control in the CNS are still open. Recent research opened new perspectives using specific antivirals such as short interfering RNA (siRNA) or small molecule inhibitors. Inspite of obvious hurdles, these treatments are the most promising approaches to future therapies.

Retinoids inhibit measles virus through a type I IFN-dependent bystander effect

Measles-associated mortality can be decreased in response to treatment with vitamin A. Our goal was to understand the mechanism by which vitamin A and other retinoids reduce measles virus (MeV) replication in vitro. MeV is known to inhibit type I interferon (IFN) signaling, and retinoids are increasingly implicated in modulating innate immunity. Type I IFN blocking antibodies abrogated the inhibitory effects of all-trans retinoic acid (ATRA) on MeV replication (EC(50) of ATRA: 3.17 x 10(-8) M). IFN-stimulated genes (ISGs) are up-regulated by ATRA in MeV-infected U937 cell cultures starting at 12 h and reaching a plateau at 24 h postinfection when compared to either treatment or infection alone. We found that this increased gene expression occurs in uninfected cells by using a transwell system where the uninfected cells were separated from infected cells by a membrane with 0.02-muM pores. Uninfected bystander cells from the ATRA-treated transwells did not support substantial viral replication when subsequently infected with MeV. In the absence of ATRA, the cells from the uninfected chamber did not up-regulate ISG expression and were not protected from subsequent challenge with virus. These results demonstrate that retinoids inhibit MeV replication by up-regulating elements of the innate immune response in uninfected bystander cells, making them refractory to productive infection during subsequent rounds of viral replication.

Retinoids inhibit measles virus in vitro via nuclear retinoid receptor signaling pathways

Measles virus (MV) infects 30 million children every year, resulting in more than half a million deaths. Vitamin A (retinol) treatment of acute measles can reduce measles-associated mortality by 50-80%. We sought to determine whether or not retinoids can act directly to limit MV output from infected cells. Physiologic concentrations of retinol were found to inhibit MV output in PBMC and a range of cell lines of epithelial and endothelial origin (40-50%). Near complete inhibition of viral output was achieved in some cells/lines treated with all-trans retinoic acid (ATRA) and 9-cis RA (9cRA). Important attenuation of the anti-MV effect of retinoids in R4 cells, a subclone of a retinoid-responsive cell line (NB4) deficient in RAR signaling, demonstrates that this effect is mediated at least in part by nuclear retinoid receptor signaling pathways. Inhibition of MV replication could not be fully explained as a result of retinoid effects on cell differentiation, proliferation or viability, particularly at low retinoid concentrations (1-10nM). These data provide the first evidence that retinoids can directly inhibit MV in vitro, and raise the possibility that retinoids may have similar actions in vivo.