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

Abstract

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.

Anti-Lipid IgG Antibodies Are Produced via Germinal Centers in a Murine Model Resembling Human Lupus

“…The percentage of plasma cells that produce anti-NPA IgG antibodies increased gradually in the three organs analyzed (lymph nodes, spleen, and bone marrow), while the percentage of IgG-negative NPA-specific plasma cells decreased in these same organs at 10, 20, and 35 days after the first administration of NPA. This plasma-cell response is similar to that described for protein antigens ( 26 ). A larger number of plasma cells specific to NPA was found in the spleen, compared to the draining lymph node, and this may be attributed to the populations of B cells (B1 cells and marginal zone B cells) that are present in the spleen, but not in the lymph nodes, and which could generate such plasma cells ( 25 ).…”

Evidence of extensive renewed Schmallenberg virus circulation in Belgium during summer of 2016 - increase in arthrogryposis-hydranencephaly cases expected

“…This is clearly lower than the previously reported overall seroprevalence and between‐herd seroprevalence of, respectively, 65% and 100% reported at the end of the vector season of 2012 (Méroc, Poskin, Van Loo, Van Driessche et al., ). This seems to be in line with the general assumption that the SBV circulation in Belgium and other European countries has ceased since 2012, leading to a decline in the proportion of sheep that have been into contact with the virus and harbor SBV‐specific antibodies (Collins, Barrett, Doherty, Larska, & Mee, ; Gache et al., ; Poskin et al., ; Stokes, Baylis, & Duncan, ; Wernike, Holsteg, Sasserath, & Beer, ).…”

Schmallenberg virus detection in Culicoides biting midges in Spain: First laboratory evidence for highly efficient infection of Culicoides of the Obsoletus complex and Culicoides imicola

“…The transmission cycle of SBV seems to be ephemeral at individual herd level. This would result from interaction of two factors influencing SBV transmission dynamics: short viremia in hosts (Poskin et al., ; Wernike, Eschbaumer, Breithaupt, Hoffmann, & Beer, ) and early appearance of long‐lasting host immunity (Poskin et al., ). However, the disease spread rapidly from North to South Europe suggesting either, rapid movement of host and/or vectors or/and a high SBV infection (see Table ) and transmission rates for certain Culicoides species.…”