The expression of three desaturase genes of Spirulina platensis in Escherichia coli DH5α – Heterologous expression of Spirulina-desaturase genes

The genes from a cyanobacterium--Spirulina platensis strain C1--that encode the acyl-lipid desaturases (desC, desA and desD) involved in gamma-linolenic (GLA) synthesis have been successfully expressed for the first time in Escherichia coli by employing a pTrcHisA expression system. In this report, the authors describe the expression of the three Spirulina N-terminal 6xHis-desaturases as well as the functional analysis of these recombinant proteins. The gene products of desC, desA and desD have approximate molecular masses of 37, 45, and 47 kDa, respectively. Enzymatic activity measurement of these products was carried out in vivo to demonstrate that (i) the expressed proteins are in functional form, and (ii) the cofactors of the host system can complement the system of Spirulina platensis. The study demonstrated that the gene products of desC and desA catalyzed the reactions in vivo where the enzyme substrates were provided in appropriate concentration. This indicates that the delta9 and delta12 desaturases were expressed in the heterologous host in their active form, and that these two reactions can be carried out in an E. coli host cell using its cofactors system. In contrast, delta6 desaturase activity can be detected only in vitro where electron carriers are provided. This suggests that while this enzyme is expressed in the heterologous host in its active form, its function in vivo is suppressed, as the electron carriers of the host system cannot complement the system of Spirulina platensis.     

Adjuvant-free immunization with hemagglutinin-Fc fusion proteins as an approach to influenza vaccines

The hemagglutinins (HAs) of human H1 and H3 influenza viruses and avian H5 influenza virus were produced as recombinant fusion proteins with the human immunoglobulin Fc domain. Recombinant HA-human immunoglobulin Fc domain (HA-HuFc) proteins were secreted from baculovirus-infected insect cells as glycosylated oligomer HAs of the anticipated molecular mass, agglutinated red blood cells, were purified on protein A, and were used to immunize mice in the absence of adjuvant. Immunogenicity was demonstrated for all subtypes, with the serum samples demonstrating subtype-specific hemagglutination inhibition, epitope specificity similar to that seen with virus infection, and neutralization. HuFc-tagged HAs are potential candidates for gene-to-vaccine approaches to influenza vaccination.