ABSTRACT
Objective:To evaluate the potential of a previously identified CDR3 only single-domain antibodies (sdAbs) fragment, NBL42, as a general framework for affinity transfer.Methods:The H3 loops of VHH-A4(A4), VHH-H5(H5), cAb-Lys3(L3) and B6H12 which bind with alliinase, PD-1, lysozyme and CD47, respectively, were grafted into the corresponding loop of NBL42. The genes of the reconstituted CDR3 only sdAbs were synthesized, expressed in E. coliand purified with Ni 2+ column affinity chromatography. The antigen binding and stability of the recombinant CDR3 only sdAbs were assayed by ELISA. Results:The recombinant NBL42-A4CDR3, NBL42-H5CDR3, NBL42-L3CDR3 and NBL42-B6H12CDR3 ran as a single peak at 15, 15, 28 and 16 kDa, respectively, in SDS-PAGE as expected molecular weight. Grafted sdAbs NBL42-A4CDR3 and NBL42-H5CDR3 expressed in a soluble form and specifically bind with alliinase and PD-1, respectively, but lost about 50% of their binding activity. In contrast, the grafted sdAbs NBL42-Lys3CDR3 and NBL42-B6H12CDR3 completely lost their antigen binding capacity. NBL42 sdAbs and grafted sdAbs NBL42-A4CDR3 and NBL42-H5CDR3 retain roughly half of their binding activity after 90 ℃ heat treatment, indicating high stability. The C88Y mutation in NBL42 and the Swiss Mode 3D model predicted that the C88Y residue in FR3 may play a key role in NBL42 stability and CDR3 affinity transfer.Conclusions:The structure of NBL42 has potential as a framework for CDR3 transplantation and affinity transfer.
ABSTRACT
BACKGROUND: Saliva is considered an important vector for the Helicobacter pylori infection. The presence of the babA2 gene, encoding for BabA (blood-group antigen binding adhesin), in the H. pylori genome is crucial for H. pylori-related pathogenesis. METHODS: The study was performed in the group of 215 patients. The detection of H. pylori and babA2 in saliva and gastric tissue was done by PCR (polymerase chain reaction). Moreover, gastric tissues were stained with hematoxylin-eosin as well as with modified Giemsa methods for the analysis of Helicobacter pylori density. RESULTS: The positive rate of H. pylori by nested PCR was 78.6% in gastric tissue and 72.7% in saliva. In addition, the positive rate of H. pylori was 55.5% by the histological analysis of Helicobacter pylori density in gastric tissue. The positive rate of babA2 by PCR was 33.9% in gastric tissue, and 8.2% in saliva. CONCLUSION: We revealed that the H. pylori PCR results obtained in gastric tissue correlated well with those obtained in saliva. As saliva is more available specimen, it is more suitable for clinical application of H. pylori detection by PCR. However, clinical use of - BabA PCR seems to be limited because of its low-sensitivity.