Eric B. Austin

Suppression of antibody responses to ricin A chain (RTA) by monoclonal anti-RTA antibodies

Balb/c mice treated with an immunotoxin constructed by conjugation of murine monoclonal antibody 791T/36 via a disulfide linker to ricin A chain generate a pronounced antibody response to peptide epitopes on ricin A chain. Monoclonal anti-RTA antibodies which recognize peptide epitopes have been developed and these have been used to down-regulate anti-RTA antibody responses in 791T/36-RTA immunotoxin-treated Balb/c mice. Of the five MAB tests, two (608/7 and 596/134) proved most effective, inhibiting anti-RTA antibody formation by up to 73%. MAB treatment was effective when initiated up to 3 days after immunotoxin treatment. Pharmacokinetic studies with 791T/36-RTA have shown that the immunotoxin is rapidly eliminated from the circulation, with no more than 4% remaining in blood after 24 hr. It is proposed that the down-regulation of anti-RTA antibodies is effected by MAB interfering with antigen processing.

Regulation of the contact sensitivity response to urushiol with anti-urushiol monoclonal antibody ALG 991.

Abstract The objective of the studies was to demonstrate that the contact sensitivity (CS) response to poison ivy/oak could be downregulated following treatment with a monoclonal antibody (mAb) reacting with the allergen urushiol. Conjugation of urushiol and its synthetic analogue 3-n-pentadecylcatechol (PDC) to ¶ N -acetylcysteine yielded hydrosoluble derivatives which induced humoral immune responses in BALB/c mice. Hybridomas secreting monoclonal antibodies (mAbs) reacting with urushiol and PDC were generated by fusion of B lymphocytes from immunized mice with mouse myeloma P3NS0 cells. The specificity of mAb ALG 991 (IgM isotype) was defined by inhibition of antibody binding by PDC analogues. This demonstrated that mAb ALG 991 reacted with the catechol moiety of urushiol, the region of the allergen being critically important in the induction of contact dermatitis. The CS response to urushiol in BALB/c mice was suppressed by stimulation with mAb ALG 991 and the role of sensitized T cells, including suppressor T cells, has been considered. Suppression of CS was most effective with low doses (1 μg) of mAb incorporated into a vaccine with Freund’s adjuvant. This treatment suppressed CS responses in BALB/c mice already sensitized to urushiol.

Evaluation of intratumoral immunostimulants in the treatment of a transplantable rat mammary carcinoma.

Abstract One C. parvum preparation and two BCG (Bacillus Calmette-Guerin) strains have been evaluated for their effects, when injected intratumorally, on established growths of a transplantable rat mammary carcinoma of spontaneous origin. It was found that whilst the anti-tumor effect of intratumoral injection varied from experiment to experiment certain conclusions could be drawn. Thus for maximal effect the injection should be given as early as possible and at a high dose; furthermore, multiple intratumoral injections appeared to offer no advantage over a single injection. It was also apparent that the anti-tumor effect following intratumoral injection of C. parvum or BCG was not improved when the tumor-bearing animals were presensitised to these immunostimulants. Intratumoral C. parvum was also used as an adjunct to surgery in the treatment of metastases; however, in this model it did not improve the effect of surgery alone. It is concluded that under certain defined circumstances intratumoral injection can bring about tumor regression. However, the conditions under which it is effective may render this form of treatment of limited application.

Production of a human monoclonal antibody recognising a determinant on mouse IgG2b from a patient receiving mouse monoclonal antibody for diagnostic imaging

SummaryThe development of human antibodies recognising mouse immunoglobulins represents an obstacle to effective antibody therapy. This study shows that patients produce modest titres of antibodies (predominantly antimouse rather than anti-idiotypic) after a single low-dose injection for immunoscintigraphy, suggesting that repeated imaging with the same or a different antibody could be a problem. Fusion of the lymphocytes from a patient who had been imaged twice previously resulted in a monoclonal antibody that specifically binds to an IgG2b isotypic determinant. Anti-IgG2b antibodies predominated in this patients serum. Production of human monoclonal antibodies from patients given mouse monoclonal antibodies not only allows a finer dissection of the immune repertoire but also provides possible reagents for controlling the human anti-(mouse Ig) response, for selection of class-switch variants of mouse monoclonal antibodies and enhancing tumour imaging.