Experimental bluetongue virus superinfection in calves previously immunized with bluetongue virus serotype 8

Abstract

The effect of a superinfection with bluetongue virus serotype 1 (BTV1) was evaluated on two groups of four calves. One group received a commercial inactivated BTV serotype 8 (BTV8) vaccine. This group and the non-vaccinated group of calves were challenged twice (4 months apart) with the European BTV8 strain isolated during the 2006–2007 epidemics. Calves were then infected with a BTV1 inoculum which was found to be unexpectedly contaminated by BTV serotype 15 (BTV15). BTV1 and BTV15 single infections were performed on two other groups of three BTV naïve calves. A severe clinical picture was obtained after superinfection with BTV1/BTV15 in both vaccinated and non-vaccinated animals and after challenge with BTV8 in non-vaccinated animals. BTV1 and BTV15 single infection caused only very slight clinical signs. After superinfection and at the viraemic peak, there were an average of above 1000 times more BTV15 genomic copies than BTV1 ones. BTV1 RNA could be detected only in the spleen of one calf whereas BTV15 RNA was found in 15 organs of seven different animals. BTV8 immunization whether it was acquired through vaccination and challenges or challenges alone did not change BTV1 or BTV15 RNA detection in superinfected animals. However in these animals a partial cross neutralization between BTV8 and BTV1 might be involved in the lower BTV1 replication versus BTV15. Infection with different serotypes can occur also in the field. Interference between virus strains, genetic reassortment and cross-protection were considered as mechanisms to explain the clinical outcomes and the other virological and immunological findings in the course of BTV1/BTV15 superinfection.Electronic supplementary materialThe online version of this article (doi:10.1186/s13567-016-0357-6) contains supplementary material, which is available to authorized users.

Recall T cell responses to bluetongue virus produce a narrowing of the T cell repertoire

“…Our results show that although an expansion of PBMC occurs after serial BTV inoculations, the infection is not completely controlled, resulting in detectable BTV RNA by RT-qPCR. Similarly, in BTV-8-immunized calves BTV1/15 replication still occurred after heterologous challenge [34]. In our study, the characterization of the expansion of CD4 + and CD8 + T cell responses during primary and secondary responses demonstrated a burst in size of the CD8 + but not the CD4 + population 15 days after each challenge.…”

Seroprevalence of Bluetongue Virus in small ruminants in Balochistan province, Pakistan

“…Notably, in many instances of such “mixed” infections, the clinical severity of particular strains shows marked variability. For instance, serotypes 1, 6, 8, 11, 14, 25 and 27 were detected in Western and Central Europe (Jenckel et al., ; Martinelle et al., ), and of these, serotype 8 was found to be the most devastating, causing the death of 5%–10% of the national flock in Belgium alone (Saegerman et al., ). However, when reported from France in 2015, serotype 8 infection had little or negligible clinical impact on the susceptible population (Sailleau et al., ).…”

Pathogenic Potential and Global Epidemiology of Bluetongue Virus that Cause Infection in Ruminants

“…To device the constrains on disease spread different strategies were applied such as constraints on animal whereabouts, disease surveillance and live vaccination of animals with locally produced live attenuated vaccine against the serotype 4 (Mellor and Wittmann, 2002). In a study BTV serotypes 1, 6, 8, 11, 14, 25, 27 were reported in Western and Central Europe ( Jenckel et al, 2015;Martinelle et al, 2016). Table 1 describe an up to date list of distribution and epidemiological pattern of various serotypes of Bluetongue virus.…”