A High-Affinity Native Human Antibody Disrupts Biofilm from Staphylococcus aureus Bacteria and Potentiates Antibiotic Efficacy in a Mouse Implant Infection Model

Abstract

Many serious bacterial infections are difficult to treat due to biofilm formation, which provides physical protection and induces a sessile phenotype refractory to antibiotic treatment compared to the planktonic state. A key structural component of biofilm is extracellular DNA, which is held in place by secreted bacterial proteins from the DNABII family: integration host factor (IHF) and histone-like (HU) proteins. A native human monoclonal antibody, TRL1068, has been discovered using single B-lymphocyte screening technology. It has low-picomolar affinity against DNABII homologs from important Gram-positive and Gram-negative bacterial pathogens. The disruption of established biofilm was observed in vitro at an antibody concentration of 1.2 g/ml over 12 h. The effect of TRL1068 in vivo was evaluated in a murine tissue cage infection model in which a biofilm is formed by infection with methicillin-resistant Staphylococcus aureus (MRSA; ATCC 43300). Treatment of the established biofilm by combination therapy of TRL1068 (15 mg/kg of body weight, intraperitoneal [i.p.] administration) with daptomycin (50 mg/kg, i.p.) significantly reduced adherent bacterial count compared to that after daptomycin treatment alone, accompanied by significant reduction in planktonic bacterial numbers. The quantification of TRL1068 in sample matrices showed substantial penetration of TRL1068 from serum into the cage interior. TRL1068 is a clinical candidate for combination treatment with standard-of-care antibiotics to overcome the drug-refractory state associated with biofilm formation, with potential utility for a broad spectrum of difficult-to-treat bacterial infections.T he understanding of bacterial physiology has fundamentally changed since the discovery of biofilms in the bacterial life cycle (1-3). Biofilms provide an anchor and physical protection for bacterial cells and the physiology and genetic programming of the bacteria shift from the planktonic (free-floating) to a sessile (adherent) state. This shift can result in a substantial reduction of antibiotic sensitivity in the biofilm (4). As much as 65 to 80% of clinically significant bacterial infections resistant to antibiotics are associated with biofilm (5, 6), including those of implants and catheters, infective endocarditis, lung infections associated with cystic fibrosis and chronic obstructive pulmonary disease (COPD), persistent infections of the ears and urinary tract, osteomyelitis, and surgery-associated nosocomial infections. Accordingly, a promising approach to treatment is to disrupt biofilms so that the freed bacteria become sensitive to available antibiotics as well as more fully subject to immune control (7).Biofilms are not simply random assemblies of bacterial and host components. Rather, the polymers in a biofilm form a multinode scaffolding with a semirigid, three-dimensional web-like architecture (8) which serves to exclude host immune cells while allowing the diffusion of nutrients and waste. Comparative genomic studies have identified tens of proteins a...

Targeting microbial biofilms: current and prospective therapeutic strategies

“…When combined with antibiotic therapy, immunotherapy targeting DNABII has shown efficacy in vivo against biofilms in numerous types of bacteria, including oral bacteria 56 , uropathogenic E. coli 57 and P. aeruginosa in a mouse lung infection model 58 . This approach has also shown efficacy against MRSA biofilms compared with antibiotic treatment alone in mouse models 59,60 . In a combinatorial approach without using antibiotics, DNABII antibodies were combined with a vaccine strategy.…”

High affinity anti-TIM-3 and anti-KIR monoclonal antibodies cloned from healthy human individuals

“…Using CellSpot we have previously cloned antibodies that bind to the gB viral glycoprotein of Human Cytomegalovirus (HCMV) [3], to hemagglutinin (HA) proteins from diverse strains of influenza A and B viruses [4], to the G glycoprotein of Respiratory Syncytial Virus (RSV) [5], and to bacterial proteins of the DNABII family implicated in biofilms [6]. For each of these targets, mAbs have been selected as therapeutic candidates and are currently in preclinical development.…”

A Human Biofilm-Disrupting Monoclonal Antibody Potentiates Antibiotic Efficacy in Rodent Models of both Staphylococcus aureus and Acinetobacter baumannii Infections

“…Nonetheless, in combination with TRL1068, the efficacy of imipenem was significantly improved compared to those in untreated animals and animals treated with imipenem plus the isotype control (Ϫ0.8 and Ϫ0.5 log 10 CFU/ catheter, respectively; P Յ 0.009). In our previous study (26), similar dosing of TRL1068 (15 mg/kg of body weight intraperitoneally [i.p.]) in mice resulted in peak serum levels of Ͼ50 mg/liter, with serum levels being maintained well above the effective concentration in vitro for over a week ( Fig.…”

“…The disruption of biofilms in vitro by polyclonal sera raised against a DNABII protein has been shown to work by the extraction of the protein from the biofilm (30), for which the high affinity of TRL1068 is a favorable property. TRL1068 activity against biofilms of both P. aeruginosa and S. aureus was previously demonstrated by scanning electron microscopy (SEM) examination of biofilm-coated surfaces; also, the efficacy in vivo of this MAb was demonstrated in a murine implant infection model (26).…”

“…As we have described previously (26), TRL1068 is a high-affinity MAb directed against the DNABII protein family discovered by screening ϳ5 million human B lymphocytes using CellSpot technology (27). The conformational epitope on DNABII proteins was determined by high-resolution peptide mapping, including alanine scanning (26). This epitope is in the region implicated in DNA binding (28), which may account for the high degree of conservation.…”