Robyn Cassan

Protective mAbs and Cross-Reactive mAbs Raised by Immunization with Engineered Marburg Virus GPs

The filoviruses, which include the marburg- and ebolaviruses, have caused multiple outbreaks among humans this decade. Antibodies against the filovirus surface glycoprotein (GP) have been shown to provide life-saving therapy in nonhuman primates, but such antibodies are generally virus-specific. Many monoclonal antibodies (mAbs) have been described against Ebola virus. In contrast, relatively few have been described against Marburg virus. Here we present ten mAbs elicited by immunization of mice using recombinant mucin-deleted GPs from different Marburg virus (MARV) strains. Surprisingly, two of the mAbs raised against MARV GP also cross-react with the mucin-deleted GP cores of all tested ebolaviruses (Ebola, Sudan, Bundibugyo, Reston), but these epitopes are masked differently by the mucin-like domains themselves. The most efficacious mAbs in this panel were found to recognize a novel “wing” feature on the GP2 subunit that is unique to Marburg and does not exist in Ebola. Two of these anti-wing antibodies confer 90 and 100% protection, respectively, one hour post-exposure in mice challenged with MARV.

Novel Clostridium difficile Anti-Toxin (TcdA and TcdB) Humanized Monoclonal Antibodies Demonstrate In Vitro Neutralization across a Broad Spectrum of Clinical Strains and In Vivo Potency in a Hamster Spore Challenge Model

Clostridium difficile (C. difficile) infection (CDI) is the main cause of nosocomial antibiotic-associated colitis and increased incidence of community-associated diarrhea in industrialized countries. At present, the primary treatment of CDI is antibiotic administration, which is effective but often associated with recurrence, especially in the elderly. Pathogenic strains produce enterotoxin, toxin A (TcdA), and cytotoxin, toxin B (TcdB), which are necessary for C. difficile induced diarrhea and gut pathological changes. Administration of anti-toxin antibodies provides an alternative approach to treat CDI, and has shown promising results in preclinical and clinical studies. In the current study, several humanized anti-TcdA and anti-TcdB monoclonal antibodies were generated and their protective potency was characterized in a hamster infection model. The humanized anti-TcdA (CANmAbA4) and anti-TcdB (CANmAbB4 and CANmAbB1) antibodies showed broad spectrum in vitro neutralization of toxins from clinical strains and neutralization in a mouse toxin challenge model. Moreover, co-administration of humanized antibodies (CANmAbA4 and CANmAbB4 cocktail) provided a high level of protection in a dose dependent manner (85% versus 57% survival at day 22 for 50 mg/kg and 20 mg/kg doses, respectively) in a hamster gastrointestinal infection (GI) model. This study describes the protective effects conferred by novel neutralizing anti-toxin monoclonal antibodies against C. difficile toxins and their potential as therapeutic agents in treating CDI.

MICE IMMUNIZED WITH CYCLIC-SER-ASN-LYS (CSNK) PEPTIDE GENERATE POLYCLONAL ANTIBODIES SELECTIVE FOR Aβ OLIGOMERS: A VACCINE STRATEGY FOR ALZHEIMER'S DISEASE

Plasma anti-Ab antibody levels, and plasma and brain Ab levels were measured by ELISA. In cynomolgus monkeys, DT (500 m L/head, s.c.) were administered, and three weeks later, peptide (0.5 or 2.5 mg/head, s.c.) were administered at intervals of two weeks. Serum anti-Ab antibody levels and plasma Ab levels were measured by ELISA. Results: Ab peptide vaccination produced an increase in the plasma antiAb antibody level and reduction of the brain Ab40 level in guinea pigs. A negative correlation between the plasma antiAb antibody level and brain Ab40 level, and a positive correlation between the plasma antiAb antibody level and plasma Ab level were observed. In monkeys treated with the Ab peptide vaccine, the levels of serum antiAb antibody and plasma Ab42 increased. The binding profiles of the anti-Ab antibodies produced in guinea pigs and monkeys were similar. Conclusions: These results suggested that our Ab peptide vaccine alone, in the absence of any adjuvant, produced antiAb antibody in guinea pigs and monkeys. We propose that this peptide would be a possible therapeutic candidate for AD.