Variability in total serum IgE over 1 year in severe asthmatics.

BACKGROUND: Immunoglobulin E (IgE) is the treatment target of omalizumab, a monoclonal antibody indicated in the treatment of severe allergic asthma. Long-term variability of serum total IgE (sIgEtot) in asthmatics remains poorly documented. METHODS: In this prospective study, sIgEtot levels were measured over 1 year at 7 time points in 41 severe asthmatics treated with high-dose of inhaled corticosteroids and long-acting ß2 agonists. 33 patients were atopic based on at least one positive RAST to common aeroallergens. Patients were divided into three groups according to their baseline sIgEtot level: low (< 76 IU/mL; n = 10), intermediate (76-700 IU/mL; n = 20) or high (> 700 IU/mL; n = 11). Patients also completed the six-item Juniper Asthma Control Questionnaire (ACQ6). The sIgEtot variability and factors predictive for this variability were studied, as well as ACQ6 outcomes. RESULTS: The variation in sIgEtot level was mostly the consequence of between patient-variability, which represented 96%, 71% and 96% of the total variability in the low, intermediate and high sIgEtot subgroups, respectively. The residual within-patient variability was therefore limited. In 10/41 patients, sIgEtot levels increased or decreased, for at least one visit, beyond the predefined range of the subgroups to which they were assigned (< 76 IU/mL; 76-700 IU/mL; > 700 IU/mL). There was a significant but weak correlation between sIgEtot and ACQ6 score over all time points (r = 0.15, p = 0.02), but sIgEtot failed to associate with severe exacerbation. sIgEtot decreased by 3% with any additional year of age for the whole group (p = 0.01) and increased by 5% per one unit of allergen exposure score in atopic patients (p = 0.002). CONCLUSION: In severe asthmatics, limited within-patient variability of sIgEtot levels was observed over 1 year as opposed to marked between-subject variability. sIgEtot decreases with age. Variation in sIgEtot weakly associates with asthma control but not with exacerbation.

Genetically stable infectious Schmallenberg virus persists in foetal envelopes of pregnant ewes.

Schmallenberg virus (SBV) is a recently emerged vector-borne virus, inducing congenital defects in bovines, ovines and caprines. Here we have shown that infectious SBV is capable of persisting until the moment of birth in the foetal envelopes of ewes infected with SBV-infectious serum at day 45 (1/5 positive) and 60 (4/6 positive) of gestation. This persistence of at least 100 days is a new aspect of the SBV pathogenesis that could help to explain how SBV overwinters the cold season in temperate climate zones. Furthermore, sequencing of the M segment shows that the persisting virus in the foetal envelopes is genetically stable since only a few mutations compared to the inoculum were found. This supports the hypothesis that persisting virus could start the infection of new hosts. Finally, neutralization tests showed that infectious SBV present in the foetal envelopes at birth can be neutralized by the humoral immunity present in the infected ewes.

Reconstruction of the Schmallenberg virus epidemic in Belgium: Complementary use of disease surveillance approaches.

Schmallenberg virus (SBV) emerged across Europe in 2011 and Belgium was among the first countries affected. In this study, published findings are combined with new data from veterinary surveillance networks and the Belgian reference laboratory for SBV at the Veterinary and Agrochemical Research centre (CODA-CERVA) to reconstruct the epidemic in Belgium. First retrospective cases of SBV were reported by veterinarians that observed decreased milk yield and fever in dairy cattle in May 2011. The number of SBV suspicions subsequently increased in adult cattle in August 2011. That month, first SBV positive pools of Culicoides were detected and extensive virus circulation occurred in Belgium during late summer and autumn 2011. As a consequence, most pregnant ruminants were infected and their fetuses exposed to the virus. This resulted in an outbreak of abortions, still-births and malformed new-borns observed between January and April 2012. The number of cases drastically diminished in 2012-2013, although multiple lines of evidence obtained from cross-sectional serological surveys, analyses on aborted foetuses, sentinel herd surveillance and surveillance of SBV in vectors prove that SBV was still circulating in Belgium at that time. Virus circulation was then probably strongly reduced in 2013-2014, while increasing evidence indicates its recirculation in 2014-2015 in Belgium. Based on the experience gathered with the closely related Akabane virus, recurrent outbreaks of congenital events can be expected for a long period. Vaccination of seronegative animals before the first mating could be used to prevent the deleterious effects of SBV. During this epidemic, different surveillance approaches including syndromic surveillance, sentinel herd surveillance, cross-sectional seroprevalence studies and pathogen surveillance in vectors have proven their utility and should be considered to continue in the future.

Persistence of the protective immunity and kinetics of the isotype specific antibody response against the viral nucleocapsid protein after experimental Schmallenberg virus infection of sheep.

Schmallenberg virus (SBV) is an Orthobunyavirus that induces abortion, stillbirths and congenital malformations in ruminants. SBV infection induces a long lasting seroconversion under natural conditions. The persistence of the protective immunity and the isotype specific antibody response upon SBV infection of sheep has however not been studied in detail. Five sheep were kept in BSL3 facilities for more than 16 months and subjected to repeated SBV infections. Blood was regularly sampled and organs were collected at euthanasia. The presence of SBV RNA in serum and organs was measured with quantitative real-time PCR. The appearance and persistence of neutralizing and SBV nucleoprotein (N) isotype specific antibodies was determined with virus neutralization tests (VNT) and ELISAs. The primo SBV infection protected ewes against clinical signs, viraemia and virus replication in organs upon challenge infections more than 15 months later. Production of neutralizing SBV specific antibodies was first detected around 6 days post primo-inoculation with VNT and correlated with the appearance of SBV-N specific IgM antibodies. These IgM antibodies remained present for 2 weeks. SBV-N specific IgG antibodies were first detected between 10 and 21 dpi and reached a plateau at 28 dpi. This plateau remained consistently high and no significant decrease in titre was found over a period of more than 1 year. Similar results were found for the neutralising antibody response. In conclusion, the SBV specific IgM response probably eliminates SBV from the blood and the protective immunity induced by SBV infection protects sheep against reinfection for at least 16 months.

Experimental Infection of Sheep at 45 and 60 Days of Gestation with Schmallenberg Virus Readily Led to Placental Colonization without Causing Congenital Malformations.

BACKGROUND: Main impact of Schmallenberg virus (SBV) on livestock consists in reproductive disorders, with teratogenic effects, abortions and stillbirths. SBV pathogenesis and viral placental crossing remain currently poorly understood. Therefore, we implemented an experimental infection of ewes, inoculated with SBV at 45 or 60 days of gestation (dg). METHODOLOGY: "Mourerous" breed ewes were randomly separated in three groups: eight and nine ewes were subcutaneously inoculated with 1 ml of SBV infectious serum at 45 and 60 dg, respectively (G45 and G60). Six other ewes were inoculated subcutaneously with sterile phosphate buffer saline as control group. All SBV inoculated ewes showed RNAemia consistent with previously published studies, they seroconverted and no clinical sign was reported. Lambs were born at term via caesarian-section, and right after birth they were blood sampled and clinically examined. Then both lambs and ewes were euthanatized and necropsied. PRINCIPAL FINDINGS/SIGNIFICANCE: No lambs showed any malformation suggestive of SBV infection and none of them had RNAemia or anti-SBV antibodies prior to colostrum uptake. Positive SBV RNA detection in organs was rare in both G45 and G60 lambs (2/11 and 1/10, respectively). Nevertheless most of the lambs in G45 (9/11) and G60 (9/10) had at least one extraembryonic structure SBV positive by RTqPCR. The number of positive extraembryonic structures was significantly higher in G60 lambs. Time of inoculation (45 or 60 dg) had no impact on the placental colonization success rate but affected the frequency of detecting the virus in the offspring extraembryonic structures by the time of lambing. SBV readily colonized the placenta when ewes were infected at 45 or 60 dg but infection of the fetuses was limited and did not lead to congenital malformations.

Experimental Schmallenberg virus infection of pigs.

Schmallenberg virus (SBV) is a newly emerged virus responsible for an acute non-specific syndrome in adult cattle including high fever, decrease in milk production and severe diarrhea. It also causes reproductive problems in cattle, sheep and goat including abortions, stillbirths and malformations. The role of pigs in the epidemiology of SBV has not yet been evaluated while this could be interesting seen their suggested role in the epidemiology of the closely related Akabane virus. To address this issue, four 12 week old seronegative piglets were subcutaneously infected with 1 ml of SBV infectious serum (FLI) and kept into contact with four non-infected piglets to examine direct virus transmission. Throughout the experiment blood, swabs and feces samples were collected and upon euthanasia at 28 dpi different organs (cerebrum, cerebellum, brain stem, lung, liver, iliac lymph nodes, kidney and spleen) were sampled. No clinical impact was observed and all collected samples tested negative for SBV in rRT-PCR. Despite the absence of viremia and virus transmission, low and short lasting amounts of neutralizing antibodies were found in 2 out of 4 infected piglets. The limited impact of SBV infection in pigs was further supported by the absence of neutralizing anti-SBV antibodies in field collected sera from indoor housed domestic pigs (n=106). In conclusion, SBV infection of pigs can induce seroconversion but is ineffective in terms of virus replication and transmission indicating that pigs have no obvious role in the SBV epidemiology.