Background: Gardnerella vaginalis
is a bacterial vaginosis (BV)-associated vaginal bacterium that produces the
toxin vaginolysin (VLY). VLY is a pore-forming toxin that is suggested to be the main virulence factor of
G. vaginalis. The high recurrence rate of BV and the emergence of antibiotic-resistant bacterial species
demonstrate the need for the development of recombinant antibodies as novel therapeutic agents for disease
treatment. Single-chain variable fragments (scFvs) generated against VLY exhibited reduced efficacy to
neutralize VLY activity compared to the respective full-length antibodies. To improve the properties of scFvs,
monospecific dimeric scFvs were generated by the genetic fusion of two anti-VLY scFv molecules connected by
an alpha-helix-forming peptide linker.
Results: N-terminal hexahistidine-tagged dimeric scFvs were constructed and produced in
Escherichia coli
and
purified using metal chelate affinity chromatography. Inhibition of VLY-mediated human erythrocyte lysis by
dimeric and monomeric scFvs was detected by
in vitro hemolytic assay. The circulating half-life of purified
scFvs in the blood plasma of mice was determined by ELISA. Dimeric anti-VLY scFvs showed higher
neutralizing potency and extended circulating half-life than parental monomeric scFv.
Conclusions: The protein obtained by the genetic fusion of two anti-VLY scFvs into a dimeric molecule exhibited
improved properties in comparison with monomeric scFv. This new recombinant antibody might implement
new possibilities for the prophylaxis and treatment of the diseases caused by the bacteria
G. vaginalis.
