Passive immunization via neutralizing scFv-Mab to specific antigen of Aggregatibacter actinomycetemcomitans ameliorates periodontal infection and destruction in vivo (VAC5P.1120)

Aggregatibacter actinomycetemcomitans-Aa, a G(-) anaerobe, is involved in medical/dental infection, i.e., aggressive periodontitis, & systemic disorders. To explore anti-bacterial immunity & therapeutics, its genomic library was screened by expression-cloning using disease-associated CD4+T-cells of HuPBL- NOD/SCID mice. Such cloning yielded one novel gene, designated cagE-homologue, encoding a bacterial type-IV secretion system homologous to Helicobacter pylori cagE & Agrobacterium tumefaciens virB4. We showed that: i) Aa-CagE induced apoptosis of targets, based on biochemical & genetic studies; ii) anti-CagE IgG-response was significantly correlated with disease progression. By CagE immunization in HuPBL-SCID mice and the recombinatorial phage-display library, we screened to develop therapeutics for Aa. The screening yielded human sc-Fv-Mabs to CagE (CagE-scFv-Mabs), as confirmed by binding assay & sequencing. To this end, our latest studies showed that human CagE-scFv-Mabs were manifested by: i) high binding activity (>108~9M-1); ii) strong neutralizing capability by inhibiting CagE-induced caspase3-mediated apoptosis (>80%); iii) possessing anti-toxin-like Ig-CDR sequences; iv) significantly reduced Aa colonization in biofilm and reduced alveolar bone loss in mice. It is concluded that CagE-scFv-Mabs capable of inhibiting apoptosis, Aa colonization and bone destruction via immunization exhibit the potential to ameliorate periodontal & medical infections associated with Aa.