Virulence of the Lyme disease spirochete before and after the tick bloodmeal: a quantitative assessment

Parasites & Vectors

Table 2 Infectivity of tick-derived spirochetes engineered to constitutively produce OspC

Spirochete source and strain		Mouse infection
	Inoculum^a (spirochetes/mouse)	Sero-conversion^b (infected/no. inoculated)	Tissue isolation^c (infected/no. inoculated)
UNFED Ticks
WT	~90	0/5	0/5
	8,900	0/5	0/5
A3/flaB _p::ospC ^d	~70	0/5	0/5
	7,300	0/5	0/5
After Cultivation^e
WT	~10	0/5	0/5
	1,000	5/5	5/5
FED Ticks
WT	~190	5/5	5/5
	18,800	5/5	5/5
A3/flaB _p::ospC	~90	5/5	5/5
	8,800	5/5	5/5

^aGroups of 5-10 infected ticks were ground in medium before or immediately after feeding to repletion on naïve mice, and homogenates frozen at -80 °C. Homogenates were thawed for inoculation of mice, and aliquots plated to determine the number of viable spirochetes in each inoculum
^bMice were bled 3 weeks post-challenge and sero-conversion to B. burgdorferi whole cell lysates assessed by immunoblot analysis
^cMice were euthanized 5 – 6 weeks post-challenge and infection assessed by attempted isolation of spirochetes from the ear, joint and bladder tissues of each mouse
^dA3/flaB _p::ospC refers to WT spirochetes engineered to constitutively produce OspC [15]
^eSpirochetes in unfed tick homogenates previously frozen at -80 °C were thawed and cultivated in BSK II medium for 4 days at 35 °C prior to mouse inoculation. The number of viable bacteria injected was determined by plating an aliquot of each inoculum

ISSN: 1756-3305