Basic research for establishing molacular diagnosis of insecticide-resistance in humanlouse

从一株对杀虫剂敏感的体虱株NIID中，新测定了副同源钠通道和乙酰胆碱酯酶的cDNA序列。采用连续浸渍法测定NIID家鼠对杀虫剂的敏感性，并于处理3 h后对击倒家鼠进行评分。成家鼠KCl和KC99浓度分别为20mg/m2和54 mg/m2。以KC99值作为最小判别浓度，以KC1值作为估计耐药率的参考值。在东京埼玉县、神奈川县采集了10个头虱菌落，进行了对苯氰菊酯的敏感性测定，其中3个为抗性菌落。在低估情况下，抗性菌落表现出最高的抗性比为160倍。对一种对吩氰菊酯敏感的头虱与NIID体虱的钠通道基因的完整编码序列进行了比较，两者之间存在一个同义碱基替换。一个抗药性虱有23个核苷酸取代，其中4个可能导致氨基酸取代，抗性钠通道的结构变化可能与这些突变有关。这些氨基酸替换中的两种，T952I和L955P，至少在先前报道的美国和英国的抗拟除虫菊酯头虱菌落（Lee et al. 2000）和现在的日本头虱中是相同的。根据这些抗性特异性点突变，我们可以用比活虱更容易获得的卵和死虱进行拟除虫菊酯类杀虫剂抗性的分子诊断。

The cDNA sequences encoding for para-orthologous sodium channel and acetylcholinesterase were newly determined from an insecticide-susceptible bodylice strain, NIID. Insecticide susceptibility of NIID louse were assayed by continuous phenothrin-impregnated filter-contact method and knockdown louse were scored after 3 hours treatment. KCl and KC99 of adult louse were 20mg/m2 and 54 mg/m2, respectively. The KC99 value was used for a minimum resistant-discriminating concentration while the KC1 value was used for a reference in estimating resistance ratio of torelent louse. Ten headlice colonies collected in Saitama Pref. , Tokyo, Kanagawa Pref. were assayed for phenothrin susceptibility and three were resistant. A resistant colony showing the highest resistance ratio in underestimation was 160-fold. The complete coding sequence of sodium channel gene from a phenothrin-susceptible headlice was compared to that from the NIID bodylice and there was a single synonymous base substitution between them. A phenothrin-resistant headlice had 23 nucleotide substitutions in which four resulted in putative amino acid substitutions, structural change in resistant sodium channel should be involved in some of these mutations. The two out of these amino acid substitutions, T952I and L955P, were at least shared among the pyrethroid-resistant headlice colonies in the US and UK reported previously (Lee et al. 2000) and the present Japanese leadlice. Bsed on these resistant-specific point mutations, we would be possible to excute molecular diagnosis of pyrethroid-rsistance with eggs and dead louse which are obtained more easily than alived louse.