Development of effective
topical microbicides for the prevention of HIV-1 sexual transmission represents a primary goal for the control of the
AIDS pandemic. The viral coreceptor CCR5, used by the vast majority of primary HIV-1 isolates, is considered a primary target molecule.
RANTES and its derivatives are the most suitable
protein-based compounds to fight HIV-1 via CCR5 targeting. Yet, receptor activation should be avoided to prevent pro-inflammatory effects and possibly provide anti-inflammatory properties. C1C5
RANTES is a
chemokine mutant that exhibits high anti-HIV-1 potency coupled with CCR5 antagonism. However, the need for the formation of an N-terminal intramolecular
disulfide bridge between non-natural
cysteine residues at positions 1 and 5 represents a challenge for the correct folding of this
protein in recombinant expression systems, a crucial step towards its development as a
microbicide against HIV-1. We report here a rare case of superior folding in a prokaryote as compared to an eukaryotic expression system. Production of C1C5
RANTES was highly impaired in CHO cells, with a dramatic yield reduction compared to that of wild type
RANTES and secretion of the molecule as
disulfide-linked dimer. Conversely, a human vaginal isolate of Lactobacillus jensenii engineered to secrete C1C5
RANTES provided efficient delivery of the monomeric
protein. This and other reports on successful secretion of complex
proteins indicate that lactic acid bacteria are an excellent system for the expression of therapeutic
proteins, which can be used as a platform for the engineering of conceptually novel
RANTES mutants with potent anti-HIV-1 activity.