Parasite cultures were distributed in six well plates (2 ml per well) and pharmacological inhibitors were added at desired concentration. Plates were placed in small gas chambers, gassed and immediately returned to 37°C incubator. The lysates were prepared after ~30 min of the addition of inhibitors

Intracellular Na + measurement was performed using the fluorescent Na + indicator Sodium Green TM tetracetate. THP-1 macrophages were resuspended in phenol-red free RPMI-1640 medium and incubated with Sodium Green™ at a final concentration of 1 JiM for 20 min at room temperature. The cells were washed once with fresh serum-free media to remove excess probe following which kinetic fluorescent measurements were commenced in a spectrofluorimeter (BMG Fluostar Optima) at an excitation of 480 nm and emission of 520 nm. In situ calibration to determine the dissociation constant (Kct) of the dye at 3 7°C was accomplished by using the indicator dye in solutions of precisely known free Na+ concentration in the presence of the pore forming antibiotic gramicidin (10 J,tM). Intracellular Na+ was calculated using the following formula: where, Kct of the dye is 5.7 mM at 37°C, F is the fluorescence of the experimental sample, Fmin is the fluorescence in the absence of Na+ and Fmax is the fluorescence under saturating concentrations ofNa+ in the presence of gramicidin (10 J.i.M)

Circular Dichroic spectra of various proteins were recorded at room temperature, using a JASCO J7i0 spectropolarimeter fitted with a thermostated cell holder. I 50 J..Lg protein was dissolved in 3 ml of I 0 mM sodium phosphate buffer (pH 7.0), and the samples were scanned in the far-UV range (200-250 nm). A cell with a 1 em optical path was used to acquire the spectra at a scan speed of 50 nrn/min. with a. sensitivity of 50 mdeg and a response time of I sec. The sample compartment was purged with nitrogen, and spectra were averaged over I 0 accumulations. The CD spectra were normalized to mean residue ellipticity curves using Jasco software. Yang's reference parameters were used to perform secondary structure analyses from CD measurements using Jasco Secondary Structure Estimation Programme (Yang et al., 1986).

transferred to another plastic box containing 2 X sse, 1 % SDS and washed at room temperature by gentle rocking for 15 minutes. The buffer was then changed and the washing continued at 60 in a shaking water bath for 30 minutes. Depending on the homology between the probe and the immobil ised DNA, the washing conditions were varied. The stringency ranged from 1 X sse, 1 % SDS, at 65°e to 0.2 X sse, 1 % SDS, at 65°e. After the washing, the filters were immediately sealed into plastic bags and put for autoradiography. Special care was taken to not to allow the filters to dry during any stage which might otherwise cause permanent binding of the probe to the filter preventing the reprobing of the same filter with a different probe at a later time. For autoradiography, the plastic bag containing the washed filter was fixed on a 3 MM Whatman sheet and placed securely ins ide a X ray cassette with one or two intensifying screens, and a X -ray film was placed over the filter in a dark room. The cassette was kept at -7o0e for the desired length of exposure. The film was taken out in the dark room, developed for approximately 3 minutes, washed in water for one minute to wash off all the developer adhering to the film, and fixed for 5 minutes. Finally, the film was washed in cold water for 10 minutes and air dried

The prehybridisation and hybridisation of the Southern filters was carried out as described by Maniatis et al., ( 1982 ), with some modifications. In all stages, the SDS concentration was maintained at 1 % to minimise the background likely to occur on the nylon membrane. Prehybridisation was done at 68°C, for 4 - 6 hours, with 0.1 ml of prehybridisation buffer for each square centimeter of the membrane. The probe was denatured by immersing the eppendorf tube in a boiling water bath for 10 minutes and added directly to the bag containing prehybridisation mix. Hybridisation was done in aqueous system, at 68°e, without the use of formam ide, for 18 - 2 4 hours, in a plastic bag kept submerged in a water bath, without any shaking. At the end of hybridisation, the filter was taken out of the bag and quickly immersed in a plastic box containing 5 X sse, 1 % SDS at room temperature. After 15 minutes, the filter was

hours. The NC filters having bound DNA liberated from bacterial colonies, were set up for hybridisation with radioactive probes as described by Maniatis et al., ( 1982 ). The filters were washed thoroughly with a solution containing 50 mM Tris.Cl, pH 8.0, 1 M NaCl, 1 mM EDTA, 1 % SDS, at 42°C, for 1 hour, to wash off any residual bacterial debris and agar etc. Prehybridisation and hybridisation was performed in aqueous solution without formamide in 5 X SSPE. The filters were washed up to a stringency of 0.2 X sse at 65°e.

Colonies bound to nitrocellulose filter ( NC ) were lysed to liberate the DNA which was hybridised as described by Maniatis et al., 1982 ) . To obtain sharper autoradiography signals, the nitrocellulose filter bearing colonies was first overlaid on a 3 MM Whatman paper impregnated with 10 % SDS till the NC wetted evenly. The NC was peeled off and overlaid on another 3 MM paper impregnated with the denaturing solution. In this manner, the NC was successively treated with denaturing and neutralising solutions. Finally, the NC filter was air dried, sandwiched between two sheets of 3 MM paper and baked at 80°C for two

The antibody isotypes in the immune sera were determined, by indirect ELISA, using mouse MAb isotyping reagents (Sigma). The microtitration plates coated with r-dZP3 (400 ng/well) and blocked with 1% BSA, were incubated with doubling dilution of pooled serum samples of a group of immunized animals. All the incubations were carried out at 37°Cand were followed by three washings with PBST. The incubation was followed by addition of goat anti-mouse isotype specific antibodies at 1:1000 dilution. The binding was revealed by rabbit anti-goat lgG-HRPO conjugate (Pierce) at an optimized dilution of I: 10,000 and processed for enzymatic activity estimation as described earlier.

492 run with 620 nm as the reference filter. The antibody response generated was represented as the geometric mean of the absorbance of individual mice sera in a group of immunized animals. b1 addition, the antibody titer against r-dZP3 was also determined by ELISA. The assay was carried out as described above except that 100 ~l of doubling dilutions of the serum samples (dilutions made in PBST supplemented with 0.1% BSA) were added per well in duplicate. For each serum sample tested, a reciprocal of dilution giving an absorbance of 1.0 was calculated by regression analysis and represented as antibody units (AU).

Microtitration plates were coated with optimized concentration of r-bmZP1 (250 ng/well), r-dZP3 (400 ng/well) or r-rG (500 ng/well) in 50 mM PBS, pH 7.4, at 37°C for 1 h and then at 4°C, 0/N. The plates were washed once with PBS and incubated with 1% BSA, (200 Jll/ well) in PBS for 2 h at 37°C for blocking the non-specific sites. All subsequent incubations were carried out for 1 h at 37°C and each incubation was followed by three washings with PBS containing 0.05% Tween-20 (PBST). Post-blocking, the plates were incubated with 1 :50 dilution of either the preimmune or the immune serum samples obtained from mice immunized with the respective plasmid DNA. Antibodies bound tor-bmZP 1, r-dZP3 and r-rG were revealed with 1:2000 dilution of goat anti-mouse IgG (whole molecule) HRPO (Dako). Estimation of the enzymatic activity was carried out with 0.05% OPD in 50 mM citrate phosphate buffer, pH 5.0, containing 0.06% H202 as the substrate. The reaction was stopped with 50 Jll of 5 N H2S04 and the absorbance read at

d) Particle delivery using the Helios gene gun A day prior to immunization, hair were removed from the abdominal region of mice using a commercial depilatory agent (Anne French cream). Two cartridges/mouse ( ~ 2 Jlg DNA) were shot under pressurized helium gas ( 400 psi) intradermally at the shaven area of the abdomen of mice using the Helios gene gun. Two boosters comprising of two cartridges each were given on days 21 and 35. On day 45, mice in each group received i.m. injection of E. coli expressed recombinant protein (20 Jlglmouse in saline). Mice were bled retro-orbitally on days 0, 45 and 52 for analysis of antibody response.

tubing, which was cut into 0.5 inch pieces (cartridges). These cartridges were used to deliver DNA into epidermis of male/female mice. a) Preparation of DNA-gold microcarrier suspension Twenty five mg of gold microcarriers were weighed in a 1.5 ml eppendorf tube to which 100 J..Ll of 0.05 M spermidine was added and vortexed for 10 sec. To the above mixture 100 J..Ll of DNA (0.5 mg/ml) was added and vortexed for another 10 sec. While vortexing, 100 J..Ll of 1 M CaCh was added dropwise to the mixture and left at RT for 10 min to allow precipitation of DNA onto gold microcarriers. The DNA-gold pellet was collected by centrifuging at 12,000 X g for 1 min at RT. The pellet was washed thrice with 100% ethanol (freshly opened bottle), resuspended in 3 ml of 0.1mg/ml polyvinylpyrollidone (PVP) in ethanol and stored at -20°C till further use. b) Loading the DNA/microcarrier suspension into gold-coat tubing using the tubing prep station A 25 inch length of tubing was cut and fixed on tubing prep station, air dried by passing nitrogen gas through it for 15 min. The DNA/microcarrier suspension was vortexed and injected into the tubing using a 5 ml syringe and the microcarriers allowed to settle in the tubing for 3 min. Ethanol from the tubing was removed by slowly sucking into the syringe. The tubing was rotated, while passing the nitrogen gas, using the tubing prep station, for 20-30 sec to allow the microcarriers to evenly coat the inside of the tubing. c) Preparation of cartridges using the tubing cutter The tubing was cut into 0.5 inch long pieces (cartridges) by using the tubing cutter and cartridges stored at 4°C in vials containing desiccant pellets till further use.

Suspension of DNA adsorbed onto gold microcarriers at 0.5 Microcarrier Loading Quantity (MLQ; 50 J.lg DNA/25 mg gold microcarriers) was prepared and coated inside Tefzel

A day prior to immunization, hair were removed from both the hind limbs of the mice using a commercial depilatory agent (Anne French cream, Geoffrey Manners & Co. Ltd, Mumbai, India). Mice were immunized in a similar way as in the saline group but in addition, ten very short electric pulses were given at the site of injection immediately after DNA administration using a gas igniter (Upadhyay, 2001). Voltage delivered in each trigger was 18kV for 10-7s.

Inbred male BALB/c.T mice (6-8 week, Small Experimental Animal Facility, National Institute of Immunology, New Delhi, India) were immunized intramuscularly (i.m.) with 100 J.lg of respective plasmid DNA or VR1020 vector in 100 J.ll saline (0.9% NaCl) in the anterior tibialis muscle in the hind limbs (each receiving 50 J.ll). Two booster injections of 100 J.lg DNA in saline were given on day 21 and 35. On day 45, mice in each group received i.m. injection of E. coli expressed recombinant protein (20 J.lg/mouse in saline). Mice were anesthetized and bled retro-orbitally on days 0, 45 and 52 for analysis of respective antibody responses.

IV. IN-VIVO IMMUNIZATION STUDIES These experiments were carried out with the approval of Institutional Animal Ethics Committee. Three different modes of administration were used:

a) Purification oLin elusion bodies For the purification of inclusion bodies, the bacterial cell pellet from 1 liter culture was resuspended in 10 ml of Tris-HCl buffer (50 mM; pH 8.5) containing 5 mM EDTA and sonicated using Branson sonifier-450 for 8 cycles of 90 sec each (30 watt output; Branson Ultrasonic Corp., Danbury, CT, USA) on ice. The inclusion bodies were collected by centrifugation of the sonicate at 8000 X g for 30 min at 4°C. The pellet was washed twice with 15 ml of 50 mM Tris-HCl buffer with 5 mM EDTA containing 2% sodium deoxycholate in order to remove loosely bound E. coli proteins from the inclusion bodies. Subsequently, the inclusion body pellet was washed with 50 mM Tris-HCI buffer (pH 8.5), followed by a washing with the double distilled water. All the buffers used for the purification contained 20 mM of phenylmethyl sulphonyl fluoride (PMSF). b) Solubilization and renaturation The purified inclusion bodies were solubilized in 100 mM Tris-HCl (pH 12.0) containing 2M urea at RT for 30 min, and centrifuged at 8000 X g for 30 min at 4°C. The pH ofthe supernatant was brought down immediately to 8.5 with 1 N HCl and then extensively dialyzed against renaturation buffer (50 mM Tris-HCl buffer; pH 8.5, 1 mM EDT A, 0.1 mM reduced glutathione, 0.01 mM oxidized glutathione and 10% sucrose). The protein was finally dialyzed against 20 mM Tris-HCl, pH 8.5 and its concentration estimated using BCA.

The proteins were purified by nickel affinity chromatography. The cell pellet ( ~ 1 g) of each clone was solubilized in 5 ml ofbuffer A (6 M guanidine hydrochloride, 0.1 M NaH2P04, 0.01 M Tris, pH 8.0). The suspension was centrifuged at 8000 X g for 15 min at 4°C and the supernatant containing the recombinant protein was mixed with Ni-NT A resin (Nickel-Nitrilotriacetic acid equilibrated with buffer A) and kept for gentle end-to-end shaking for 1 hat RT. The resin was loaded on a column and washed with 10 bed-volumes of buffer A. The column was subsequently washed with 5 bed-volumes each of buffers B, and C, which contained 8 M urea, 0.1 M NaH2P04 and 0.01 M Tris and had successively reducing pH values of 8.0 and 6.3 respectively. The protein was eluted with buffers D and E (composition same as buffer B) in which the pH was further reduced to 5.9 and 4.5 respectively. Five fractions of 4 ml each were collected during elution with buffer D and buffer E respectively. The eluted proteins were analysed by 0.1% SDS-1 0% PAGE (gels stained with Coomassie blue) and Western blot. The fractions showing the purified recombinant protein were pooled and concentrated in an Amicon concentrator using a YM30 membrane and dialyzed against 100 mM phosphate buffer, pH 7.4, containing 4 M urea. The concentration of each purified protein was estimated by bicinchoninic acid (BCA).

reached a value of 0.5-0.6. The cultures were then induced with 1 mM IPTG for 2 h at 37°C. Cells were pelleted at 4000 X g for 30 min at 4°C and stored at -70°C until used.

BloodglucosewasestimatedbyFolin-Wumethod(KlontzandSmith,1968).Glucoseonboilingwithalkalinecoppersolution,reducescopperfromthecuprictothecuprousstate(cuprousoxide).Thecuprousoxidesoformedreducesphosphomolybdicacidtothebluecoloredmolybdenumblue,whichismeasuredcolorimeterically.TheintensityofthebluecolorisproportionaltoglucoseconcentrationanditiscolorimetricallydeterminedinaBoschandLombSpectrophotometerat620nm

After transfection the cells were harvested and protein was isolated from the celllysates. The cells from each well were pelleted at 2000 rpm for 10 min at 40C. The supernatant was carefully removed and the pellet was incubated on ice for 1 hr after adding 50pl of lysis buffer (1% triton X100, 0.1mM EDTA, 0.1mM EGTA, 1mM DTT, 1X PI, all in 1X PBS) with intermittent vortexing. The tubes were centrifuged at maximum rpm for 10 min at 40C and the supernatant, containing the proteins, was collected and stored at -700C. The purified protein fractions were quantitated using the BCA protein assay kit and the O.D. was taken at 562nm

A bioluminescent ATP determination kit from Invitrogen (Carlsbad, CA) was used to quantitate ATP levels. The assay is based on luciferase' s requirement for ATP for producing light (emission maxima at 560nm). The assay was carried out as described previously (Mukherjee et al., 2002). Briefly, a standard reaction mix was prepared-1X reaction buffer, 0.1p.M DTT, O.Sp.M Luciferin and 12.5 p.g/ mL Luciferase. 100 p.L was aliquoted into each well of a 96 well white plate and a base line reading measured using Fluostar Omega using the luminometer adaptor. Then either 106 parasites or different concentrations of A TP (prepared from the stock solution provided in the kit) were added to these wells as test and standard curve samples respectively. Again luminescence was measured and the baseline subtracted from the readings. The different dilutions of ATP were used to plot the standard curve which was then used to calculate the ATP levels in cells expressed as nmol/106 cells.

run on an agarose gel and band size determined by comparison against DNA ladder with bands of known sizes. Clones that were positive for the presence of gene/ plasmid were further checked by restriction digestion. For restriction digestion, plasmid was first isolated by Miniprep as described below. The digestion reactions were set according to manufacturer's protocol appropriate for the enzymes used. The products were run on an agarose gel and band size determined by comparison against DNA ladder with bands of known sizes. Clones with the desired pattern of digestion were propagated further and used

Bacterial colonies obtained by transformation were checked for the presence of plasmid or gene inserted into the plasmid by colony PCR and restriction digestion. For PCR, a master mix for all the PCR reactions to be performed was made, aliquoted into PCR vials and stored on ice. Individual colonies were picked up, numbered and streaked onto an LB agar plate followed by deposition of a few cells into the PCR mix. PCR was carried out as described above for the respective primer pairs with the exception that the initial denaturation was carried out for 7 min at 94 °C. The products were