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

Hybridisation of southern filters.

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.

Antibody isotyping

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

Plasmid DNA adsorbed onto gold microcarriers

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.

Plasmid DNA administered by electroporation

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.

Plasmid DNA administered in saline

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.

Purification in refolded form