Improvement and optimization of a T-cell-dependent antibody response (TDAR) method for BALB/c mice using keyhole limpet hemocyanin (KLH) as specific antigen

Preclinical Pharmacokinetics and Pharmacology Study of RC98: A Programmed Cell Death Ligand 1 Monoclonal Antibody in Cynomolgus Monkeys

INTRODUCTION

RC98 is the monoclonal antibody against Programmed Cell Death Ligand 1 (PD-L1). Relevant reports have confirmed that the influence of PD-L1 expressed by tumor cells on antitumor CD8+ T cell responses is well characterized, but the impact of PD-L1 expressed by immune cells has not been well defined.

OBJECTIVE

This study aimed to design a Pharmacokinetics/Pharmacology (PK/PD) study of RC98 in normal cynomolgus monkeys to research the effect on the immune system.

METHODS

RC98 and vehicle were administered to cynomolgus monkeys at 15 mg/kg via intravenous infusion once a week for 4 weeks to evaluate the relationship between PK and PD. The pharmacodynamic activity was measured by the PD-L1 receptor occupancy (RO) in CD3+ T cells, A T-cell-dependent antibody response (TDAR), and the concentration of soluble PD-L1.

RESULTS

The pharmacokinetic result showed that the exposure from the last administration was lower than that of the first administration, probably due to immunogenicity production. There was a strong correlation between systemic exposure and RO in CD3+ T cells but decreased RO levels after the last dose, which indirectly reflected the activation of T cells. The keyhole limpet hemocyanin (KLH)-induced TDAR in the RC98 group was higher than in the vehicle group. The concentration of soluble PD-L1 had increased feedback with RC98, and the concentration of soluble PD-L1 was maintained at a higher level after multiple doses than before dosing.

CONCLUSION

These data indicate that the immune system was clearly activated. In addition, the non-clinical data could provide a basis for its efficacy evaluation in clinical trials.

The Outer Membrane Proteins and Their Synergy Triggered the Protective Effects against Pathogenic Escherichia coli

Colibacillosis caused by pathogenic Escherichia coli (E. coli) is one of the most serious infectious diseases, causing an extensive burden on animal husbandry and the human healthcare system. Vaccination is one of the ideal ways to prevent E. coli infection. In this work, recombinant outer membrane protein A (rOmpA), outer membrane protein C (rOmpC) and BamA (rBamA) from E. coli O78 (CVCC CAU0768) were expressed in a prokaryotic expression system with the concentration of 1–2 mg/mL after purification. Considerable immune responses could be triggered in mice that were immunized with these recombinant proteins, high antibody titers, high total IgG level and various antibody isotypes were detected in antisera after booster immunizations. Moreover, mice immunized with several recombinant proteins in combination showed a higher survival rate with the challenge of homologous strain E. coli O78 and a more significant cross-protection effect against heterologous strain E. coli O157:H7 (CICC 21530) in vivo than those of immunized alone. The antisera from immunized mice showed high affinity to multiple strains of Escherichia, Shigella and Salmonella in vitro, indicating that recombinant outer membrane proteins from E. coli O78 had the potential to be developed into universal antigenic substances against not only E. coli but also a variety of Gram-negative bacteria. rOmpA was considered as the most immunogenic protein in this work and the combination of different proteins could further enhance the immune response of immunized mice, which provided the reference for the construction of novel antigens with higher efficiency.

A T-cell-dependent antibody response (TDAR) method in BALB/c mice based on a cytometric bead array

Most current methods to assess T-cell-dependent antibody responses (TDAR) are semi-quantitative and based on measures of antibody titer generated against a standard antigen like keyhole limpet hemocyanin (KLH). The precision, sensitivity, and convenience of TDAR assays might be improved by applying rapid, sensitive, specific cytometric bead assays (CBA). In the study here, KLH antigen was covalently coupled onto the surface of cytometric beads using immune microsphere technology, and IgM antibody capture spheres were prepared for use in pretreatment processing of samples. The working parameters associated with this novel TDAR-CBA system were optimized in orthogonal experiments. The optimal concentration of the KLH coating solution in this system was 160 μg/ml, that of the anti-KLH IgG capture spheres 6.0 × 10⁵/ml, and the optimal dilution of fluorescein isothiocyanate (FITC)-conjugated Affini-Pure Goat Anti-Mouse IgG (H + L) was 60 μg/ml. Repeated tests indicated that this approach yielded good linearity (r² = 0.9937) method, with a within-run precision of 3.1-4.9%, and a between-run precision of 4.4-4.9%. This new approach had a limit of detection of 113.43 ng/ml (linear range = 390.63-50 000), and an interference rate of just 0.04-3.51%. Based on these findings, it seems that a new mouse TDAR assay based on CBA can be developed that would appear to be more sensitive, accurate, and precise than the current TDAR assay approaches based on traditional ELISA.