Varella Rafael B, Zalona Ana Carolina J, Diaz Nuria C, Zalis Mariano G, Santoro-Lopes Guilherme
Laboratory of Virology, Department of Microbiology and Parasitology, Universidade Federal Fluminense, Brazil.
Departments of Preventive Medicine, Hospital Universitário Clementino Fraga Filho, Universidade Federal do Rio do Janeiro, Brazil.
Virus Res. 2018 Jan 2;243:65-68. doi: 10.1016/j.virusres.2017.10.018. Epub 2017 Oct 26.
BK polyomavirus (BKV) is an opportunist agent associated with nephropathy (BKVAN) in 1-10% of kidney transplant recipients. BKV is classified into genotypes or subgroups according to minor nucleotidic variations with unknown biological implications. Studies assessing the possible association between genotypes and the risk of BKVAN in kidney transplant patients have presented conflicting results. In these studies, genotype Ia, which is highly prevalent in Brazil, was less frequently found and, thus, comparative data on the biological properties of this genotype are lacking. In this study, BKV Ia and Ib1 genotypes were compared according to their viral load, genetic evolution (VP1 and NCCR) - in a cohort of renal transplant recipients. The patients infected with Ia (13/23; 56.5%) genotype exhibited higher viral loads in urine [>1.4 log over Ib1 (10/23; 43.5%); p=0.025]. In addition, genotype Ia was associated with diverse mutations at VP1 loops and sites under positive selection outside loops, which were totally absent in Ib1. Although the number of viremic patients was similar, the three patients who had BK nephropathy (BKVAN) were infected with Ia genotype. NCCR architecture (ww or rr) were not distinctive between Ia and Ib1 genotypes. Ia genotype, which is rare in other published BKV cohorts, presented some diverse biological properties in transplanted recipients in comparison to Ib1.
BK多瘤病毒（BKV）是一种机会致病菌，在1%至10%的肾移植受者中与肾病（BKVAN）相关。BKV根据微小核苷酸变异分为基因型或亚组，其生物学意义尚不清楚。评估基因型与肾移植患者BKVAN风险之间可能关联的研究结果相互矛盾。在这些研究中，在巴西高度流行的基因型Ia较少被发现，因此缺乏关于该基因型生物学特性的比较数据。在本研究中，对BKV Ia和Ib1基因型的病毒载量、基因进化（VP1和NCCR）进行了比较——研究对象为一组肾移植受者。感染Ia（13/23；56.5%）基因型的患者尿液中的病毒载量更高[>1.4 log，高于Ib1（10/23；43.5%）；p = 0.025]。此外，基因型Ia与VP1环以及环外正选择位点的多种突变相关，而Ib1中完全没有这些突变。尽管病毒血症患者的数量相似，但三名患有BK肾病（BKVAN）的患者感染的是Ia基因型。Ia和Ib1基因型之间的NCCR结构（ww或rr）并无差异。与Ib1相比，在其他已发表的BKV队列中罕见的Ia基因型在移植受者中呈现出一些不同的生物学特性。
