Antibody fragments can be expressed at a high level in microbial systems, but they may have limited therapeutic value because they are rapidly eliminated from the body. We demonstrate here that site-specific conjugation or binding of bacterially derived Fab' to the long-lived protein serum albumin allows full retention of the antibody's binding characteristics while imparting the albumin's longevity in vivo. In rats the area under the curve for Fab' conjugated to rat serum albumin was 17-fold greater than for the control of Fab' conjugated to cysteine. Again, a bispecific F(ab')(2) with specificity for rat serum albumin showed an area under the curve about 8-fold greater than did a F(ab')(2) without specificity to albumin. Genetic fusions of scFv to albumin were similarly long-lived and could be expressed in yeast to provide the basis of a cost-effective production system.

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SummaryImmune complexes containing human gamma (g)l or murine g2a antibodies generate secondary erector mechanisms via Fc receptor binding or complement activation, whereas those containing human g4 or murine gl antibodies generally do not. Therefore, isotype selection of therapeutic antibodies may have important clinical consequences. In a rabbit model of recombinant human tumor necrosis factor (rhuTNF)-induced pyrexia, a murine/human chimeric g4 anti-human TNF-ot mcnoclonal antibody (mAb) (cCB0011) showed a dose-dependent inhibition ofpyrexia, whereas a gl isotype variant of the same mAb gave a marked pyrexia that was seen at all doses indicative of an immune complex-mediated response. To investigate whether isotype difference could influence mAb efficacy in pathological disease states, hamster/murine chimeric gl and g2a anti-murine TNF-o~ mAbs (TN3gl, TN3g2a) were studied in experimental shock in mice and rats. In lipopolysaccharide-induced shock in mice, treatment with TN3gl mAb at 30 and 3 mg/kg resulted in 90% survival by 72 h 00 ~< 0.004), and prolonged survival to 45 h (p ~< 0.05), respectively, compared with 100% mortality by 27 h in controls. In contrast, a g2a isotype variant of the same mAb (30 mg/kg) resulted in only 10% survival by 72 h (p ~< 0.05). In a neutropenic sepsis model in rats there was greater survival in animals receiving the gl isotype of TN3 compared with g2a isotype variant (70 vs. 27%; p ~< 0.005) with 100% mortality in the controls. These differences were not due to the pharmacokinetic profiles of the mAbs. In models of experimental shock antibody isotype can affect outcome with inactive isotypes (human g4 and murine gl) being more efficacious than active isotypes (human gl and murine g2a).

SUMMARYSteroid hormones, such as glucocorticoids (GC ), influence immune and inflammatory responses through their suppressive actions. Recent evidence suggests that another steroid hormone, dehydroepiandrosterone (DHEA), provides an immunostimulatory influence opposing the eÂect of GC. DHEA circulates in its inactive sulphated form, DHEAS, requiring conversion to DHEA by a steroid sulphatase (SS) enzyme for biological activity. Therefore, inhibition of SS activity may aÂect immune responses, allowing endogenous GC eÂects to predominate. We have shown that administration of DHEA and DHEAS in contact sensitization (CS ) augments ear swelling by 39 and 46% respectively (P<0·001). DHEAS at doses of 0·5, 5 and 50 mg/kg reverses the inhibitory eÂect of corticosterone ( 5 mg/kg) (P<0·01). In CS, CT2251 (SS inhibitor) at 10 and 0·1 mg/kg inhibited ear swelling by 61 and 38% (P<0·05) respectively. In addition, it inhibited DHEAS-augmented responses by 49 and 35% respectively (P<0·05), with no eÂect on DHEAaugmented responses. DHEAS reversed CT2251 inhibition of the CS response with complete reversal at 50 mg/kg (P<0·05). DHEAS and CT2251 appear to aÂect cellular infiltration into the ear, since DHEAS increased the number of lymphocytes by 63·8% and macrophages by 107% (P<0·001), whereas CT2251 at 0·1 mg/kg decreased the number of lymphocytes by 65% (P<0·001) and macrophages by 80% (P<0·001). DHEAS, CT2251 and dexamethasone had no eÂect on oedema in the ear. From our data we have shown that steroid hormones, such as DHEA, have the potential to act as immunostimulatory factors in vivo. Inhibiting the conversion of DHEAS to DHEA by SS enzyme leads to an anti-inflammatory eÂect.