Recombinant Engineered Antibodies Against Anthrax

Anthrax is a highly contagious bacterial infection and a persistent global threat, both as a deadly zoonotic disease and potential weapon in the hands of bioterrorists (Kamal et al, 2011). It is easy to spread, its spores can survive for a long time under various conditions, and it can be engineered to become antibiotic resistant. It is by no means an imaginary threat – in 2001, anthrax spores were mailed to news reporters and senators in the US causing multiple infections and five deaths (CDC).

This makes the establishment of effective therapies against anthrax an important task for the biomedical industry. Moreover, there is a dire need for quick and effective diagnostic assays for anthrax, in order to detect the infection as early as possible and prevent disease development. To aid in this research, Absolute Antibody now offers a suite of highly effective antibodies directed against two major antigens of the anthrax toxin – protective antigen (PA) and lethal factor (LF).

Anthrax toxin is the main factor causing the deadly effects of the infection. It is composed of the following three elements: protective antigen (PA), lethal factor (LF), and edema factor (EF). Anthrax toxin enters the cells using the PA, which binds to a cellular receptor and is then cleaved to create a multimer associating with LF and EF, introducing them to the intracellular environment where they mediate the toxin’s pathological effects (Chen et al, 2006). Antibodies inhibiting various steps of this process can provide powerful protection against anthrax. Such passive immunization can be particularly important when vaccination or antibiotic treatments are not practical or effective, as well as when the accumulation of the toxin is very high and the inhibition of bacterial growth is not sufficient (Chen et al, 2006).

Absolute Antibody offers a whole range of highly effective anti-anthrax antibodies, including four anti-PA clones (W1, W2, W5, and A63-6) and two anti-LF clones (F3-6 and F5-1). In particular, W1 and W2 display very strong neutralizing capacity, with W1’s neutralizing capabilities demonstrated to be 15-fold higher than those of the popular murine anti-PA clone 14B7 (Chen et al, 2006). It also had one of the highest affinities against anthrax PA ever reported (Kd = 4e-11 mol/L). In addition, the human IgG1 versions of W1 and W2 fully protected rats from the anthrax toxin challenge, even when the antibody had been injected one week before the toxin challenge, demonstrating a slow dissociation rate crucial in potential clinical use (Chen et al, 2006). The ELISA graphs below show the binding curves of both the anti-PA (Figure 1) and anti-LF (Figure 2) clones, tested against anthrax antigens from our sister company Kerafast.

Absolute Antibody provides all the anti-anthrax antibodies in engineered recombinant formats. We turned the original scFvs into potent neutralizing versions, such as human IgG1 or mouse IgG2a. The antibodies are also available as IgMs, which can be used as components of serological tests in vaccination and exposure studies, as positive controls and in antibody protection studies. Finally, we offer the antibodies in recombinant rabbit IgG format, allowing for the use of different secondary antibodies for detection purposes. Combined all together, these can be used as fundamental research, diagnostic, or potential therapeutic agents.

Figure 1. ELISA using anti-anthrax PA antibodies. The plate was coated with anthrax protective antigen (PA) protein (Kerafast catalog number ENH003-LT) at 2.5 µg/mL. Serial dilutions of Ab02352 (W1), Ab02353 (W2) or Ab02354 (W5) were prepared over a range of 3000 ng/mL to 0.0169 ng/mL. For detection, HRP-labelled anti-rabbit IgG antibody was used.

Figure 2. ELISA using anti-anthrax LF antibodies. The plate was coated with anthrax lethal factor (LF) protein (Kerafast catalog number ENH016-LT) at 2.5 µg/mL. Serial dilutions of Ab02356 (F3-6) or Ab02357 (F5-1) were prepared over a range of 3000 ng/mL to 0.0169 ng/mL. For detection, HRP-labelled anti-rabbit IgG antibody was used.

Catalog NumberClone NameSpecies ReactivityAvailable Isotypes/ Formats
Ab02352Anti-PA anthrax [W1]Bacillus anthracisHuman IgG1, IgG1 Fc Silent™, IgM; Mouse IgM, IgG2a, IgG2a Fc Silent™; Rabbit IgG
Ab02353Anti-PA anthrax [W2]Bacillus anthracisHuman IgG1, IgG1 Fc Silent™, IgM; Mouse IgM, IgG2a, IgG2a Fc Silent™; Rabbit IgG
Ab02354Anti-PA anthrax [W5]Bacillus anthracisHuman IgG1, IgG1 Fc Silent™, IgM; Mouse IgM, IgG2a, IgG2a Fc Silent™; Rabbit IgG
Ab02355Anti-PA anthrax [A63-6]Bacillus anthracisHuman IgG1, IgG1 Fc Silent™, IgM; Mouse IgM, IgG2a, IgG2a Fc Silent™; Rabbit IgG
Ab02356Anti-LF anthrax [F3-6]Bacillus anthracisHuman IgG1, IgG1 Fc Silent™, IgM; Mouse IgM, IgG2a, IgG2a Fc Silent™; Rabbit IgG
Ab02357Anti-LF anthrax [F5-1]Bacillus anthracisHuman IgG1, IgG1 Fc Silent™, IgM; Mouse IgM, IgG2a, IgG2a Fc Silent™; Rabbit IgG