Production of monoclonal antibodies binding to the VP7 protein of African horse sickness virus

Production and Characterization of Monoclonal Antibodies Against the VP7 Protein of Epizootic Hemorrhagic Disease Virus

Monoclonal antibodies (MAbs) against epizootic hemorrhagic disease virus (EHDV) were produced by immunizing BALB/c mice with rec-VP7-EHDV2; 66 clones producing MAbs able to recognize the VP7-EHDV with a strong reaction were obtained and tested in indirect enzyme-linked immunosorbent assay (i-ELISA) against the whole epizootic hemorrhagic disease (EHD) virus serotype 2; potential cross-reactions with related orbiviruses, as Bluetongue virus (BTV) and African horse sickness virus (AHSV), were investigated as well by i-ELISA, Western blot, and immunofluorescence. Fifty-three MAbs were specific for EHDV (VP7 recombinant protein and whole virus) and 13 reacted also with the VP7 of BTV. None of the MAbs reacted with AHSV. MAbs specific for EHDV were further characterized in a competitive ELISA (c-ELISA): 20 among them were found useful to develop a c-ELISA for the detection of antibodies against EHDV in bovine sera. The availability of this extensive set of MAbs provides the opportunity to develop a c-ELISA for the serological diagnosis of EHDV and to tune new methods for the isolation and identification of the virus in biological samples and cell cultures. The experimentation protocol was approved by the Italian Ministry of Health (number 639/2018-PR, Resp. to Prot. BDF16.13#295833199#).

Bluetongue virus viral protein 7 stability in the presence of glycerol and sodium chloride

Purpose

The Orbivirus Bluetongue virus (BTV) is an economically significant disease that affects mainly wild and domestic ruminants. BTV is most often seen symptomatically in sheep, but is easily carried by goats, cattle, and wild ruminants. To date there are several problems with the vaccines currently available for BTV, and one of the most promising candidates to increase vaccine efficacy is a protein-based vaccine, for which viral protein 7 (VP7) is a great candidate to be included in it. In order to further these studies, the stability of BTV VP7 in common vaccine additives needs to be investigated.

Materials and Methods

Recombinant BTV VP7 was expressed in a bacterial cell system and purified before being analysed using spectroscopic techniques including far-ultraviolet (UV) circular dichroism and intrinsic tryptophan fluorescence. BTV was analysed in a number of different buffer conditions.

Results

We report here that BTV VP7 maintains its native secondary structure until at least 52℃ and native-like tertiary structure to at least 80℃. Far-UV circular dichroism and intrinsic tryptophan fluorescence emission spectra indicate significant secondary and tertiary structure remaining even at 90℃, respectively. Six M guanidinium chloride is able to unfold BTV VP7 while 8 M urea could not.

Conclusion

Twenty percent glycerol and 300 mM sodium chloride appear to have a protective effect on BTV VP7's structure, as significantly more structure is seen at 90℃ when compared to BTV VP7 without the addition of these chemicals. Both glycerol and sodium chloride are common vaccine additives.