An expression cassette comprising a copy of the endogenous gene encoding the transcriptional regulator as transgene under the control of a suitable promoter, wherein the transcriptional regulator is IE-1 and/or IE-0, that allows for the expression of the proteins IE-1 and/or IE-0 functioning as transcriptional regulators above endogenous levels obtained during baculovirus infection, wherein the nucleic acid is selected from the group consisting of: (a) nucleic acid sequence indicated in any of SEQ ID NO: 1-5; (b) nucleic acid sequence having a sequence identity of at least 70%, preferably at least 80%, more preferably at least 90% and most preferably at least 95% with the nucleic acid sequence indicated in any of SEQ ID NO: 1-5 and encoding a protein functioning as a transcriptional regulator in a baculovirus; (c) nucleic acid sequence encoding a protein with the amino acid sequence indicated in any of SEQ ID NO: 6-9; and (d) nucleic acid sequence encoding a protein functioning as a transcriptional regulator in a baculovirus and having a sequence similarity of at least 70%, preferably at least 80%, more preferably at least 90% and most preferably at least 95% with the amino acid sequence indicated in any of SEQ ID NO: 6-9; a nucleic acid sequence that allows for the expression of a recombinant protein, wherein the recombinant protein is a protein forming virus-like particles wherein the expression of the recombinant protein is driven by a promoter comprising the baculoviral p10 promoter, at least one recombinant homologous region (hr) as enhancer region, operably linked to the promoter that drives the expression of the recombinant protein. a copy of the endogenous gene encoding the transcriptional regulator as transgene under the control of a suitable promoter, wherein the transcriptional regulator is IE-1 and/or IE-0, that allows for the expression of the proteins IE-1 and/or IE-0 functioning as transcriptional regulators above endogenous levels obtained during baculovirus infection, wherein the nucleic acid is selected from the group consisting of: (a) nucleic acid sequence indicated in any of SEQ ID NO: 1-5; (b) nucleic acid sequence having a sequence identity of at least 70%, preferably at least 80%, more preferably at least 90% and most preferably at least 95% with the nucleic acid sequence indicated in any of SEQ ID NO: 1-5 and encoding a protein functioning as a transcriptional regulator in a baculovirus; (c) nucleic acid sequence encoding a protein with the amino acid sequence indicated in any of SEQ ID NO: 6-9; and (d) nucleic acid sequence encoding a protein functioning as a transcriptional regulator in a baculovirus and having a sequence similarity of at least 70%, preferably at least 80%, more preferably at least 90% and most preferably at least 95% with the amino acid sequence indicated in any of SEQ ID NO: 6-9; (a) nucleic acid sequence indicated in any of SEQ ID NO: 1-5; (b) nucleic acid sequence having a sequence identity of at least 70%, preferably at least 80%, more preferably at least 90% and most preferably at least 95% with the nucleic acid sequence indicated in any of SEQ ID NO: 1-5 and encoding a protein functioning as a transcriptional regulator in a baculovirus; (c) nucleic acid sequence encoding a protein with the amino acid sequence indicated in any of SEQ ID NO: 6-9; and (d) nucleic acid sequence encoding a protein functioning as a transcriptional regulator in a baculovirus and having a sequence similarity of at least 70%, preferably at least 80%, more preferably at least 90% and most preferably at least 95% with the amino acid sequence indicated in any of SEQ ID NO: 6-9; a nucleic acid sequence that allows for the expression of a recombinant protein, wherein the recombinant protein is a protein forming virus-like particles wherein the expression of the recombinant protein is driven by a promoter comprising the baculoviral p10 promoter, at least one recombinant homologous region (hr) as enhancer region, operably linked to the promoter that drives the expression of the recombinant protein.