E coli LT

E coli diarrhea

Boyce Thompson

Phase l/ll

and well tolerated. The long-term protection could therefore not be accounted for by persistence of MAb on the teeth but may be due to a shift in the microbial balance in which other bacteria occupy the ecological niche vacated by S. mutans, resulting in resistance to recolonization by S. mutans (Fig. 4).

The antigen-binding V regions of the best murine Mab identified by Ma and Lehner, Guy's 13, has been used to create an SIgA plantibody produced in tobacco-designated CaroRx (details in Ma et al., 1995, 1998). Levels of production of CaroRx in tobacco are up to 0.5 mg/g fresh weight. Future plans call for production of CaroRx in corn and other cereal grains.

CaroRx has been produced and purified from tobacco under GMP conditions for clinical testing in the United Kingdom and the United States. CaroRx was engineered with an additional IgG CH2 domain to facilitate purification of the antibody by protein G affinity chromatography. A Poros™ protein G affinity purification was used to obtain >95% pure CaroRx from green plant tissue.

Clinical evaluation of CaroRx in a pilot phase II trial has been completed at Guy's Hospital (Ma et al., 1998). In this trial a functional comparison was made between CaroRx and the parent IgG monoclonal antibody Guy's 13. BIACORE analysis revealed that the affinity of the antibodies for purified S. mutans SA I/II was similar (KD = 0.5-1.3 X 10~9 M); however, CaroRx had fourfold higher avidity (functional affinity), a not unexpected result given the tetravalent binding of the SIgA.

Using an experimental design similar to that used to demonstrate activity of the parent Mab, CaroRx gave specific protection against colonization by oral streptococci for over 4 months (details in Ma et al., 1998). In addition to this therapeutic end point, pharmacokinetic studies showed that in the human oral cavity, CaroRx survived for >3 days versus 1 day for the fO O lA t A 0 AO t A

Complex dental flora is reduced by Chlorhexidine treatment

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