TABLE 1.

Ability of OspA vaccination to block the transmission of B. burgdorferi from nymphs to mice in the absence of complement^a

Vaccine antigen	Result for mouse group:
	WT		CD
	Tick infection (nymph)b	Mouse infectionc	Tick infection (nymph)b	Mouse infectionc
GST	+	4/4	+	5/5
OspA-GST	−	0/4	−	0/5

^aMice deficient and sufficient in complement were immunized with OspA-GST or GST alone and challenged with infected nymphal ticks.

^bTo assess the survival of spirochetes within the ticks that fed on immunized mice, homogenates of the ticks were stained with anti-Borrelia FITC-conjugated antibodies and counted under immunofluorescence. No spirochetes were observed in the ticks that fed on OspA-GST-immunized mice, while the ticks that fed on the GST-immunized mice were all found to be positive for the spirochetes.

^cResults are number of mice infected/total number of mice.