Baculovirus expression system

A process for preparing, in an insect cell, a recombinant baculovirus comprising n exogenous gene expression cassettes each to be expressed at a different locus, the process comprising introducing a replication-deficient recombinant baculovirus genome and n transfer vectors into an insect cell and thereby allowing multiple homologous recombination between:

• a) a replication-deficient baculovirus genome in which n genes essential for viral replication are distributed in n different loci of the viral DNA and are all non-functional, wherein the n non-functional genes essential for viral replication are each adjacent to a different gene non-essential for viral replication;
• and
• b) n transfer vectors each restoring the function of only one of the n non-functional genes essential for viral replication and each comprising:
• i) a nucleotide sequence that restores the function of only one of the n non-functional genes essential for viral replication, and
• ii) only one of the n exogenous gene expression cassettes, each of the n expression cassettes to be expressed at a different locus,
• the set of nucleotide sequences i) of the n transfer vectors being able to restore replication of the replication-deficient baculovirus genome;
• wherein all n being the same and being an integer at least equal to 2, and
• wherein the replication-deficient baculovirus genome and the n transfer vectors are all present in the same insect cell simultaneously, prior to the multiple homologous recombination with all n transfer vectors.