Particulate delivery systems for vaccination against bioterrorism agents and emerging infectious pathogens

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135287/1/wnan1403.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135287/2/wnan1403_am.pd

Neutralising Antibodies against Ricin Toxin

The Centers for Disease Control and Prevention have listed the potential bioweapon ricin as a Category B Agent. Ricin is a so-called A/B toxin produced by plants and is one of the deadliest molecules known. It is easy to prepare and no curative treatment is available. An immunotherapeutic approach could be of interest to attenuate or neutralise the effects of the toxin. We sought to characterise neutralising monoclonal antibodies against ricin and to develop an effective therapy. For this purpose, mouse monoclonal antibodies (mAbs) were produced against the two chains of ricin toxin (RTA and RTB). Seven mAbs were selected for their capacity to neutralise the cytotoxic effects of ricin in vitro. Three of these, two anti-RTB (RB34 and RB37) and one anti-RTA (RA36), when used in combination improved neutralising capacity in vitro with an IC50 of 31 ng/ml. Passive administration of association of these three mixed mAbs (4.7 µg) protected mice from intranasal challenges with ricin (5 LD50). Among those three antibodies, anti-RTB antibodies protected mice more efficiently than the anti-RTA antibody. The combination of the three antibodies protected mice up to 7.5 hours after ricin challenge. The strong in vivo neutralising capacity of this three mAbs combination makes it potentially useful for immunotherapeutic purposes in the case of ricin poisoning or possibly for prevention

LT-IIb(T13I), a Non-Toxic Type II Heat-Labile Enterotoxin, Augments the Capacity of a Ricin Toxin Subunit Vaccine to Evoke Neutralizing Antibodies and Protective Immunity

Currently, there is a shortage of adjuvants that can be employed with protein subunit vaccines to enhance protection against biological threats. LT-IIb(T13I) is an engineered nontoxic derivative of LT-IIb, a member of the type II subfamily of heat labile enterotoxins expressed by Escherichia coli, that possesses potent mucosal adjuvant properties. In this study we evaluated the capacity of LT-IIb(T13I) to augment the potency of RiVax, a recombinant ricin toxin A subunit vaccine, when co-administered to mice via the intradermal (i.d.) and intranasal (i.n.) routes. We report that co-administration of RiVax with LT-IIb(T13I) by the i.d. route enhanced the levels of RiVax-specific serum IgG antibodies (Ab) and elevated the ratio of ricin-neutralizing to non-neutralizing Ab, as compared to RiVax alone. Protection against a lethal ricin challenge was also augmented by LT-IIb(T13I). While local inflammatory responses elicited by LT-IIb(T13I) were comparable to those elicited by aluminum salts (Imject®), LT-IIb(T13I) was more effective than aluminum salts at augmenting production of RiVax-specific serum IgG. Finally, i.n. administration of RiVax with LT-IIb(T13I) also increased levels of RiVax-specific serum and mucosal Ab and enhanced protection against ricin challenge. Collectively, these data highlight the potential of LT-IIb(T13I) as an effective next-generation i.d., or possibly i.n. adjuvant for enhancing the immunogenicity of subunit vaccines for biodefense

Activation of the Cholinergic Antiinflammatory Pathway Reduces Ricin-Induced Mortality and Organ Failure in Mice

Exposure to ricin, either by accident through ingestion of castor oil plant seeds or intentionally through its use as a bioweapon, invariably leads to multiple organ damage and death. Currently there is only a vaccine in advanced development to ricin, but no other antidote. Ricin causes systemic inflammation with increased proinflammatory cytokine release and subsequent multiple organ failure, particularly kidney and liver dysfunction. Activation of the cholinergic antiinflammatory pathway, specifically through the alpha7 nicotinic acetylcholine receptor (either indirectly through vagus nerve stimulation or directly through nicotine treatment) reduces proinflammatory gene expression. This activation also increases release of proinflammatory chemokines and cytokines, and has proven effective in a variety of inflammatory diseases. The aim of this study was to investigate whether nicotine treatment protected against ricin toxicity in mice. Male Balb/c mice exposed to ricin had increased serum levels of the inflammatory cytokine tumor necrosis factor-α and markers of both kidney (blood urea nitrogen, creatine) and liver (alanine tranaminase) dysfunction, with a subsequent increase in mortality. Nicotine administration 2 h after ricin injection significantly delayed and reduced ricin-induced mortality, an effect coupled with reduced serum levels of tumor necrosis factor-α and markers of kidney and liver dysfunction. Both the kidney and liver had markedly increased cellular oxidative stress following ricin exposure, an effect attenuated by nicotine administration. In conclusion, these data demonstrate that in cases of ricin poisoning, activation of the cholinergic antiinflammatory pathway may prove beneficial by reducing organ damage, delaying mortality, and allowing for a greater chance of survival