The yitA and yipA genes were cloned into Champion pET300/NT-DEST vector (Life Technologies) and electroporated into E. coli BL21 (Life Technologies). Production of YitA and

YipA after IPTG induction and 4 hours of growth at 37°C was verified by SDS-PAGE and by Western blot using anti-6-His antibody (Covance, Princeton, NJ). YitA and YipA proteins were separated by SDS-PAGE and the appropriate-sized bands were excised from the gel, electroeluted and concentrated by centrifugation at 3,200 x g in centrifugal filters (Amicon Ultra Ultracel 3 K, Millipore). Eluted proteins were further purified by affinity chromatography on nickel-nitrilotriacetic acid (Ni-NTA) resin columns Entinostat order (Qiagen Inc., Valencia, CA). Rabbit polyclonal antiserum was generated against purified YitA (anti-YitA) and YipA (anti-YipA) (Lampire Biological Laboratories, Inc., Pipersville, PA). Non-specific antibodies present in the sera were PFT�� supplier removed by absorption with Y. pestis KIM6+ΔyitA-yipB cells [35]. Flea infections and determination

of proventricular blockage All animals were handled in strict accordance with Savolitinib mw good animal practice as defined by NIH animal care and use policies and the Animal Welfare Act, USPHS; and all animal work was approved by the Rocky Mountain Laboratories (RML) Animal Care and Use Committee. Fresh mouse blood was obtained from adult RML Swis-Webster mice by cardiac puncture. X. cheopis fleas were allowed to feed on an infected blood meal containing ~1 x 107 to ~1 x 108 CFU/mL of Y. pestis KIM6+ΔyitA-yipB or KIM6+ in 5 mL of fresh heparinized mouse blood. For each infection, 95 female fleas and 55 male fleas that had taken a blood meal were selected. Samples of 20 female fleas were collected immediately after infection (day 0) and at 7 and 28 days postinfection and

stored at −80°C. Throughout the 28 days following infection, fleas were maintained at 22°C and fed Celecoxib twice weekly on normal uninfected mice. Immediately after each feeding, fleas were checked by microscopy for blockage of the proventriculus as previously described [4, 36]. Fleas stored at −80°C were later surface sterilized and individually triturated and plated to determine Y. pestis infection rate and mean bacterial load per infected flea as previously described [4]. Western blot analysis of YitA and YipA levels in fleas and liquid media 2 to 4 weeks after an infectious blood meal containing 2 x 109 Y. pestis/mL, flea midguts were dissected and pooled in lysing matrix H tubes (MP Biomedicals, Solon, OH) with 1 mL Dulbecco’s phosphate-buffered saline (DPBS). Tubes containing infected flea midguts were placed in a FastPrep FP120 (Qbiogene, Inc., Carlsbad, CA) homogenizer for 15 s to triturate midguts and disrupt bacterial aggregates.