A fragment (called frg#11,
amino acids, aa 56-110) of the
protein G (pG) of
viral haemorrhagic septicaemia virus (VHSV) was designed after previous results showed it to be recognised by approximately 40% of the trout immunised to VHSV [Dis. Aquat. Organ. 34 (1999) 167]. frg#11 was then cloned, expressed, purified and used to study the production of
antibodies to its
epitopes in trout immunised to VHSV. Anti-frg#11 trout
antibodies could be detected in serum from individual trout surviving VHSV exposure, immunised by injection with purified VHSV or
DNA-immunised with its pG gene whereas it was not detected in non-infected and non-immunised trout. The trout serum
antibodies which reacted more strongly by ELISA using solid-phase frg#11 (continuous or linear
epitopes on the sequence of the pG) had the lowest VHSV-neutralising activity (
epitopes which are pG conformation-dependent). Because
antibodies recognising continuous as well as conformation-dependent
epitopes of the pG seem to be involved in protective trout immunological responses to VHSV, the estimation of anti-frg#11
antibodies could help to the dissection of the complex trout antibody response to VHSV
infections. In addition, these preliminary results suggest that the determination of anti-frg#11
antibodies might also be used to
complement in vitro viral neutralising assays which seem to be restricted to pG conformation-dependent
epitopes.