Constant domains influence binding of mouse–human chimeric antibodies to the capsular polypeptide of Bacillus anthracis

Figures & data

Figure 1. Binding of anti-capsular antibodies to PGA-coated sensor surface. The total RU that was achieved following a 180 sec pulse is given as a function of antibody concentration. The K_D of each antibody was determined using the steady-state equilibrium model in BIAevaluation software, where the theoretical RU_max is determined and the apparent K_D is equal to the antibody concentration that is necessary to reach ½ RU_max.

Table 1. Immunochemical activities of murine and mouse–human anti-PGA F26G3 antibodies

IgG subclass	Affinity (nM)	RUmax	Ab:Ag	Capsule pattern	Charge
Mu IgG3	9 ± 2	8400	2.1	Rim	+4.5
Ch IgG1	140 ± 26	4100	0.89	Puffy	+4.5
Ch IgG2	77 ± 7	6700	1.7	Puffy	+1.1
Ch IgG3	180 ± 16	4100	0.89	Puffy	+3.9
Ch IgG4	130 ± 22	2900	0.73	Puffy	+0.6

Figure 2. Capsule reaction produced by antibody binding. Top panel: Visualization of capsular polypeptide following the addition of F26G3 MuAbs IgG3 or PBS. Addition of the F26G3 MuAb IgG3 (100–150 μg/mL) produces a rim-type reaction with deposition both proximal to the cell wall and at the capsular edge. The capsule is not visible in the absence of specific antibody (PBS). Bottom panel: Visualization of capsular polypeptide following the addition of F26G3 ChAbs IgG1–4 (100 μg/mL). The addition of F26G3 ChAbs produces a puffy-type reaction that occurs uniformly throughout the capsule.