TREATMENT OF EXPERIMENTAL GROUP B STREPTOCOCCAL INFECTION WITH MONOCLONAL ANTIBODY

Abstract

Monoclonal antibody(AB) may eventually have a role in the treatment of life-threatening infection. In our previous study, mortality fell from 90% to 0% when neonatal rats, inoculated with Group B Streptococci (GBS), were injected with AB. However, AB was administered simultaneously with GBS and at the same site, unlike the situation which would exist clinically. In the present study, we gave AB intraperitoneally 2 hrs after transthoracic GBS, & 76 of 76 lived. When AB was delayed for 4, 5 or 6 hrs, survival was 92% (11/12), 60% (15/25) and 29% (5/17). When delayed for 7, 8, or 9 hrs, none of 39 lived. Failure of AB to protect after 6 hrs coincided temporally with depletion of the animals' neutrophil storage pool (NSP=PMN+bands+metamylocytes in the marrow+liver+spleen, 12.0 1.2×10⁶/gm control vs 1.5±2×10⁶/gm infected, X±SD, p <0.001). Other studies were performed to determine if NSP depletion, produced by a separate mechanism (subcutaneous polyvinyl disc implant) would similarly impair the ability of AB to protect from GBS. Six hrs after disc implantation, the NSP was reduced to 2.5±0.4×10⁶/gm. AB given with GBS or 4 or 6 hrs after GBS, did not protect 40 animals. Increasing AB by 10 fold did not improve survival. AB has potential therapeutic use because it can prevent death even when administered hours after bacterial inoculation. The neutrophil is a critical factor in the mechanisms by which AB produces protection, but AB is less likely to benefit infected neonates with profound NSP depletion.

Log in or create a free account to read this content

Gain free access to this article, as well as selected content from this journal and more on nature.com

Access through your institution

or

Sign in or create an account

Continue with Google

Continue with ORCiD