Kenji Oyama

ABR Audiometry in the Diagnosis of Cerebellopontine Angle Tumors

Auditory brain-stem responses (ABR) examination with simultaneous lobe-vertex (L-V) and membrane-vertex cm-v) recording was performed in 34 ears with cerebellopontine angle tumors. The detectability of wave I was better in M-V recording than in L-V recording, whereas L-V recording exhibited better detectability of wave V. ABR waveforms were classified into three groups, and the relations between the waveforms and the size of tumor or the degree of hearing loss were analyzed. Positive finding in ABR were obtained in 25 out of 34 ears in the present study. It was stressed that this dual recording in ABR was extremely useful in the diagnosis of cerebellopontine angle tumors.

Affinity maturation of humanized anti-epidermal growth factor receptor antibody using a modified phage-based open sandwich selection method

Affinity maturation is one of the cardinal strategies for improving antibody function using in vitro evolutionary methods; one such well-established method is phage display. To minimise gene deletion, we previously developed an open sandwich (OS) method wherein selection was performed using only phage-displaying VH fragments after mixing with soluble VL fragments. The decrease in anti-EGFR antibody 528 affinity through humanization was successfully recovered by selecting VH mutants using this OS method. However, the affinity was not similar to that of parental 528. For further affinity maturation, we aimed to isolate VL mutants that act in synergy with VH mutants. However, the OS method could not be applied for selecting VL fragments because the preparation of soluble VH fragments was hampered by their instability and insolubility. Therefore, we initially designed a modified OS method based on domain-swapping of VH fragments, from added soluble Fv fragments to phage-displaying VL fragments. Using this novel Fv-added OS selection method, we successfully isolated VL mutants, and one of the Fv comprising VH and VL mutants showed affinity almost equivalent to that of parental 528. This method is applicable for engineering other VL fragments for affinity maturation.