Viral life cycle and the diagnosis of BK polyomavirus-associated nephropathy.

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K11066
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Urology
• Research Institution: Fukuoka University (2017-2018); Kyushu University (2016)
• Principal Investigator: Masutani Kosuke 福岡大学, 医学部, 准教授 (30419593)
• Co-Investigator(Kenkyū-buntansha): 鶴屋 和彦 奈良県立医科大学, 医学部, 教授 (20372740) ; 土本 晃裕 九州大学, 大学病院, 助教 (50572103)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: BK polyomavirus / 腎移植 / 病理

Outline of Final Research Achievements

We performed immunohistochemical staining for SV40 TAg and VP1 in 28 biopsies of BKPyVAN, and compared the patterns of positivity and the percentage of positive tubules. We investigated the correlation between Cr increase and the percentage of positive tubules for both markers. In VP1 staining, positive findings were observed not only in the nuclei of tubular epithelial cells, but also in the cytoplasm, cells shedding into the lumen, intratubular casts. Two of 28 biopsies (7.1%) showed TAg-positive and VP1-negative results. The median percentage of positive tubules was 2.8% for TAg, and 1.4% for VP1 staining (P=0.2). Cr increases significantly correlated with the percentage of VP1-positive tubules (r=0.49, P=0.02), while this correlation revealed borderline significance in TAg staining. VP1 expression showed various patterns, but was detected in half as many tubules as TAg staining, which might lead to false negatives in the samples with minimal viral replication.

Free Research Field

腎臓内科学

Academic Significance and Societal Importance of the Research Achievements

VP1染色は多彩な陽性所見を呈し、視認性も良好であったが、陽性尿細管数で見ると古典的なSV40 TAg染色の半数の尿細管を検出し、感染尿細管が非常に少ない検体では偽陰性の可能性もある。従って腎症の診断の感度としてはSV40 TAg染色を超えることはないと考えられる。ただし、VP1陽性尿細管が多い症例ほど血清Cr値の上昇が大きいことから、治療経過や予後をより反映する可能性がある。Banff Working GroupがTAg染色をベースとした新しいBKウイルス腎症のステージ分類を発表しているが、予後予測能力については染色法も含め更なる検討が必要と考えられる。