INDUCTION OF T-CELL RESPONSE BY BLUETONGUE VIRUS CORE-LIKE PARTICLES EXPRESSING A T-CELL EPITOPE OF THE M1 PROTEIN OF INFLUENZA-A VIRUS

A CD4(+) T cell epitope of the influenza virus matrix protein correspo nding to the C terminus (QAYQKRMGVQMQRFK) was inserted into the VP7 ge ne of bluetongue virus (BTV). The chimeric protein was expressed by a dual recombinant Autographa californica polyhedrosis virus (AcNPV), wh ich encodes the two inner capsid proteins VP3 and VP7 of BTV. When Spo doptera frugiperda cells (Sf9 cells) were infected with this recombina nt BTV, core-like particles (CLPs) were formed as demonstrated by elec tron microscopy. To study the immunogenicity of a foreign epitope depr ived of its natural flanking sequences in vitro, purified CLPs express ing the T cell epitope were used to stimulate two different MHC class II-restricted CD4(+) human T cell clones. One of these T cell clones, ALF 3.7 was specific for the inserted epitope, whereas the other T cel l clone ALF 4.4 recognized shorter derivates of the given epitope. CLP s with the inserted epitope were presented as efficiently as purified influenza virus matrix protein to the clone ALF 3.7, whereas clone ALF 4.4 showed no proliferative response.