Resumen de Stability of the B. abortus S19 vaccine strain with a eukaryotic expression plasmid encoding the G glycoprotein from the rabies virus
Nidia G. Pazos Salazar, Juan C. Benítez Serrano, José L. Calderón Chamorro, Rigoberto Hernández Castro, Efrén Díaz Aparicio, Álvaro Aguilar Setién
Brucella abortus S19 is an intracellular vaccine strain against bovine brucellosis. Rabies is a lethal disease in cattle. Plasmids encoding the G glycoprotein from the rabies virus induce a protective immune response in different animal species. A vector called pBBR4-CMV-Ggp-SV40+, which encodes the G gene, regulated by the cytomegalovirus eukaryotic expression promoter, and which can be used to transform the B. abortus S19 vaccine strain, was constructed. The stability of the transformant strain was tested both in vitro and in vivo. In the in vitro assays, B. abortus S19 pBBR4-CMV-Ggp-SV40+ was grown for 5 sequential passages, and for the in vivo assays, female BALB/c mice were infected. Colony-forming unit counting and plasmid identification were performed in each passage and in the spleens at 7 days post-infection.
To test the plasmid stability in the strain, all parameters were determined with and without antibiotic. The bacterial concentration was lower with antibiotic than without it, but the bacterial growth was more homogeneous.
The plasmid was identified in antibiotic- and non-antibiotic-treated isolated colonies under both in vitro and in vivo conditions. The plasmid construct was also transfected into BHK-21 cells, which express the G glycoprotein. The B. abortus S19 pBBR4-CMV-Ggp-SV40+ strain showed stability, representing a suitable candidate vector for developing a bivalent vaccine against brucellosis and rabies. This is the first time that a Brucella species has been transformed with a eukaryotic expression plasmid.
