Comparative human and mouse antibody responses against tetanus toxin at clonal level

Abstract

Tetanus is a highly fatal disease caused by tetanus neurotoxin (TeNT) and remains a major threat to human and animal health, despite preventive strategies. TeNT is composed of heavy and light chain linked by a disulfide bond. The antibody response to TeNT is polyclonal and directed to multiple epitopes within both the light and heavy chains, leading to toxin neutralization. This study was undertaken to localize and compare neutralizing epitopes recognized by human and mouse TeNT-specific antibodies at a clonal level. In the present study, 22 murine hybridoma clones and 50 human lymphoblastoid cell lines secreting monoclonal antibodies (mAb) were generated against TeNT. The specificity of these mAb was determined using different recombinant fragments of tetanus toxin. Moreover, this study investigated the in vitro toxin neutralizing activity of these mAb by a ganglioside GT1b assay. The results showed that tetanus toxoid immunization in humans and BALB/c mice induced a vigorous humoral immune response against different fragments of TeNT, particularly the carboxyl-terminal fragment of the heavy chain (known as fragment C). The fragment C-specific human and mouse mAb could largely neutralize TeNT. However, while all fragment C-specific human mAb reacted with the carboxyl-terminal part of this fragment (H CC ), the majority of the mouse mAb failed to recognize this region. These results suggested that fragment C is the major target for the TeNT neutralizing antibodies, although different epitopes seem to be targeted by human and mouse antibodies.

Characterization of neutralizing chimeric heavy-chain antibodies against tetanus toxin

“…Numerous reports have described either murine or human TeNT neutralizing antibodies. 8 , 37 Some of the neutralizing antibodies, when used alone, did not completely neutralize TeNT, but only prolonged the survival of the mice, 8 , 15 , 38 unless used in combination or at high doses. 15 , 39 , 40 The tetanus-neutralizing antibodies 4E12, 3A7, and 4C1, which were developed by Li et al, could completely neutralize 10 × LD 50 using 18 μg of antibody (6 μg each) when used in combination.…”

“… 8 , 37 Some of the neutralizing antibodies, when used alone, did not completely neutralize TeNT, but only prolonged the survival of the mice, 8 , 15 , 38 unless used in combination or at high doses. 15 , 39 , 40 The tetanus-neutralizing antibodies 4E12, 3A7, and 4C1, which were developed by Li et al, could completely neutralize 10 × LD 50 using 18 μg of antibody (6 μg each) when used in combination. 13 The human monoclonal antibodies 8A7, 17F7, 8D8, and 16E8 could completely neutralize 1 × LD 50 using 37.5 μg of single antibody.…”

“… 8–14 However, some neutralizing antibodies reported to date are unable to completely neutralize TeNT when used alone. 8 , 15 Meanwhile, a few nanobodies against tetanus toxin have been reported. 11 Nanobodies, corresponding to the variable heavy-chain domain of heavy-chain-only IgGs from camelids, can bind to antigens with affinities similar to those of conventional antibodies.…”

Tetanus Toxin Fragment C: Structure, Drug Discovery Research and Production

“…Ghafari et al [60] suggested that TTFC may be the immunodominant part of the toxin, i.e., that the fragment may elicit the humoral immune response. Moreover, TT neutralizing antibodies were shown to be mainly directed against TTFC in mouse and human models (100% for mouse models and 75% in a human model) [61]. It is important to note that the many neutralizing antibodies described since the 1980s [62][63][64] cannot individually neutralize TT in vivo.…”