Abstract
BackgroundStaphylococcal enterotoxins are considered potential biowarfare agents that can be spread through ingestion or inhalation. Staphylococcal enterotoxin B (SEB) is a widely studied superantigen that can directly stimulate T-cells to release a massive amount of proinflammatory cytokines by bridging the MHC II molecules on an antigen presenting cell (APC) and the Vβ chains of the T-cell receptor (TCR). This potentially can lead to toxic, debilitating and lethal effects. Currently, there are no preventative measures for SEB exposure, only supportive therapies.MethodsTo develop a potential therapeutic candidate to combat SEB exposure, we have generated three human B-cell hybridomas that produce human monoclonal antibodies (HuMAbs) to SEB. These HuMAbs were screened for specificity, affinity and the ability to block SEB activity in vitro as well as its lethal effect in vivo.ResultsThe high-affinity HuMAbs, as determined by BiaCore analysis, were specific to SEB with minimal crossreactivity to related toxins by ELISA. In an immunoblotting experiment, our HuMAbs bound SEB mixed in a cell lysate and did not bind any of the lysate proteins. In an in vitro cell-based assay, these HuMAbs could inhibit SEB-induced secretion of the proinflammatory cytokines (INF-γ and TNF-α) by primary human lymphocytes with high potency. In an in vivo LPS-potentiated mouse model, our lead antibody, HuMAb-154, was capable of neutralizing up to 100 μg of SEB challenge equivalent to 500 times over the reported LD50 (0.2 μg) , protecting mice from death. Extended survival was also observed when HuMAb-154 was administered after SEB challenge.ConclusionWe have generated high-affinity SEB-specific antibodies capable of neutralizing SEB in vitro as well as in vivo in a mouse model. Taken together, these results suggest that our antibodies hold the potential as passive immunotherapies for both prophylactic and therapeutic countermeasures of SEB exposure.
Highlights
Staphylococcus aureus is a Gram-positive bacterium responsible for skin, soft-tissue, respiratory, bone, joint, and endovascular disorders, and has potentially lethal effects due to endocarditis, sepsis, and toxic shock syndrome [1]
Generation of human monoclonal antibodies targeting Staphylococcal enterotoxin B (SEB) Healthy volunteers whose sera showed pre-existing high immune reactivity to SEB were identified by ELISA
We screened the conditioned media produced by these hybridomas by ELISA for reactivity to STEB, an SEB vaccine which is a recombinant and attenuated form of SEB [9]
Summary
Staphylococcus aureus is a Gram-positive bacterium responsible for skin, soft-tissue, respiratory, bone, joint, and endovascular disorders, and has potentially lethal effects due to endocarditis, sepsis, and toxic shock syndrome [1]. Virulence for a number of the pathogenic manifestations of S. aureus is caused by a handful of toxins produced and secreted by the bacterium, which include among others the toxins responsible for toxic through ingestion. Staphylococcal enterotoxin B (SEB) is a widely studied superantigen that can directly stimulate T-cells to release a massive amount of proinflammatory cytokines by bridging the MHC II molecules on an antigen presenting cell (APC) and the Vb chains of the T-cell receptor (TCR). This potentially can lead to toxic, debilitating and lethal effects. There are no preventative measures for SEB exposure, only supportive therapies
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