Virulence of the Lyme disease spirochete before and after the tick bloodmeal: a quantitative assessment.
Virulence of the Lyme disease spirochete before and after the tick bloodmeal: a quantitative assessment.
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滴答滴答之前和之后的莱姆病螺旋体的毒力：定量评估。
DOI：
10.1186/s13071-016-1380-1
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发表时间：
2016-03-07
影响因子：
3.2
通讯作者：
Rosa PA
中科院分区：
文献类型：
--
作者：
Kasumba IN;Bestor A;Tilly K;Rosa PA
Borrelia burgdorferi, the tick-transmitted agent of Lyme disease, adapts to different environments as it cycles between an arthropod vector and vertebrate host. Signals encountered during nymphal tick feeding prior to transmission activate a regulon that is controlled by the alternative sigma factors RpoN and RpoS, which are required for mammalian infection. The ingested bloodmeal also provides nutrients that stimulate spirochete replication. Although the influence of tick feeding on spirochete growth and gene expression is well documented, a quantitative assessment of spirochete virulence before and after tick feeding has not been made. Homogenates were prepared from unfed and fed infected Ixodes scapularis nymphs that had acquired B. burgdorferi as larvae. Serially diluted tick homogenates were needle-inoculated into mice to determine the infectious dose of tick-derived spirochetes before and after the bloodmeal. Mouse infection was assessed by sero-reactivity with B. burgdorferi whole cell lysates on immunoblots and attempted isolation of spirochetes from mouse tissues. Viable spirochetes in tick-derived inocula were quantified by colony formation in solid media. We found that an inoculum containing as many as 104B. burgdorferi from unfed ticks is largely non-infectious, while the calculated ID50 for spirochetes from fed ticks is ~30 organisms. Engineered constitutive production of the essential virulence factor OspC by spirochetes within unfed ticks did not confer an infectious phenotype. Conditional priming of B. burgdorferi during tick feeding induces changes in addition to OspC that are required for infection of the mammalian host.
