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@#Objective To screen an effective method for removing free polysaccharides in polysaccharide-protein conjugate of pneumococcus type 9V(Pn9V),and to optimize the process and verify its stability,so as to use it in the preparation of multivalent conjugate vaccine against pneumococcus.Methods Pn9V-CRM_(197) conjugate was prepared,of which the free polysaccharides were removed by molecular sieve(Sepharose 4FF),ion exchange chromatography(DEAE Sepharose FF),hydrophobic chromatography(GP-Butyl)and ammonium sulfate(AS)salting out. The optimal method was selected by comparing the percentage of free polysaccharides,the recovery rate of polysaccharides and the recovery rate of proteins,and the determined method was optimized for the process. Three batches of conjugates were prepared continuously to verify the stability of the process.Results Both hydrophobic chromatography and ion exchange chromatography reduced the free polysaccharides in Pn9V-CRM197 conjugate to less than 5%. The recovery rates of polysaccharide and protein by hydrophobic chromatography were 34. 7% and 50. 1%,respectively,which were higher than those by ion exchange chromatography(16. 2% and 25. 7%). Hydrophobic chromatography was determined with the optimized process including 1. 1 mol/L AS as the loading buffer,water for injection used for elution,and the conjugate loading of 1. 81 mg protein/mL filler. The free polysaccharide removal rate,polysaccharide recovery rate and protein recovery rate of the conjugates prepared continuously in three batches were good,and the consistency among batches was high. The conjugates had good stability when stored at 2-8 ℃ for 6 months,and the percentage of free polysaccharides increased significantly(F = 5. 83 e~(-32),P = 0. 003)and was more than25% when stored at(25 ± 2)℃ for 6 months,indicating that high temperature storage was not suitable for the conjugates.Conclusion A hydrophobic chromatography process was established to effectively remove free polysaccharides from Pn9V polysaccharide-protein conjugate,which has good stability and provides a reference for the removal of free polysaccharides in other pneumococcal polysaccharide-protein conjugates.
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@#Objective To develop and verify a method for determination of cyanide residues in polysaccharide-protein conjugate vaccines based on flow injection analysis(FIA)with amperometric detector.Methods After removing macromolecular substances in the samples by ultrafiltration,the cyanide residues were determined by a 3700 automatic chemical analyzer with the injection time of 35 s,injection volume of 200 μL,pump speed of 40%,sample cycle time of 140 s,ultraviolet wavelength of 312 nm and an Ampere detector.The developed method was verified for the specificity,matrix effect,linear range,limit of detection(LOD),limit of quantitation(LOQ),accuracy,presicion and stability.The cyanide residues in the polysaccharide derivative bulk(13 batches)and conjugate bulk(21 batches)of Haemophilus influenzae type b conjugate vaccine and group A and C meningococcal conjugate vaccine produced by 5 manufacturers were determined by the developed method.Results Blank samples showed no interference to detection;The recoveries of the matrix effector solution of Haemophilus influenzae type b conjugate vaccine polysaccharide derivative and conjugate bulk,group A and C meningococcal conjugate vaccine polysaccharide derivative and conjugate bulk were 97.4%,102.4%,96.8% and 99.8% respectively,with all CV values less than 15%;In the range of 0.312 5 ～ 80 ng/mL,cyanogroup concentration showed a good linear relationship with peak height with a regression equation of y = 133.13 x + 57.556,R2= 0.999 1;The LOD was 0.2 ng/mL,and the LOQ was 0.6 ng/mL.The average recoveries of the control solution were 108.9%,106.5%,103.5% respectively with RSD value of 6.4% in the groups added with 5,10 and 20 ng/mL of cyanogroup and the CV values of precision verification were all less than 15%;The average concentrations of the control solution injected 20 times continuously were 76,38,18and 5 ng/mL with all CV values less than 15%,when cyanogroup concentration was 80,40,20 and 5 ng/mL,respectively.Cyanide residues were detected in 13 batches of derivative bulk samples,while not in 2 batches of 21 batches of polysaccharide conjugate bulk samples,and were detected in the others.Conclusion The developed method had good accuracy,precision and stability,which might be applied to the quantitative determination of cyanide residues in polysaccharideprotein conjugate vaccines.
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Objective To prepare a conjugate vaccine by linking Haemophilus influenzae type b (Hib)polysaccharide to PsaA protein carrier and evaluate the immunogenicity and efficacy of the conjugate vaccine. Methods A recombinant protein rPsaA,expressed by using the genetic engineering technology, was used as a protein carrier to prepare conjugate vaccine together with Hib polysaccharide. Ten mice at age of 3 weeks were immunized with the conjugate vaccine,while another 10 age-matched mice were immunized with Hib-tetanus toxoid(Hib-TT)vaccine which was produced formerly as a control. The mice treated with equal volume of PBS were set up as the negative control. The IgG antibodies in serum samples against PsaA and Hib polysaccharide were detected in two weeks after the final immunization. A suspension of Pneumococ-cus was injected into the middle ears of mice from experiment and control group. Histopathological analysis was performed to measure the clearance of bacteria in the middle ears and the severity of infection on days 3 and 7 after bacterial challenge. Results The rPsaA protein was prepared by the genetic engineering tech-nology and purified successfully with anion-exchange column. The Hib polysaccharide-PsaA protein conju-gate vaccine was prepared through a series of amide condensation reactions. The detection of IgG antibodies against PsaA protein and Hib polysaccharide in the immunized mice demonstrated that there was no signifi-cant difference with the titer of IgG against Hib polysaccharide between the mice immunized with the Hib-PsaA conjugate vaccine and those immunized with the Hib-TT vaccine. Less Pneumococcus strains were de-tected in the middle ears of mice immunized with the conjugate vaccine than those mice immunized with the Hib-TT vaccine three days after challenge. The mice from control group showed severe inflammation in the middle ears than those from experiment group. The Hib polysaccharide-PsaA protein conjugate vaccine im-proved protection against Pneumococcus infections as compared with the Hib-TT vaccine. Conclusion The rPsaA protein could be produced by genetic engineering technology and purified by anion-exchange column. The Hib polysaccharide was successfully conjugated with the rPsaA protein through amide condensation reac-tion. Both anti-PsaA and anti-Hib immune responses were induced in young mice by the injection of Hib pol-ysaccharide-PsaA protein conjugate vaccine. Apart from providing protection against Hib infection,the con-jugate vaccine might also be used for the prevention of acute otitis media caused by Pneumococcus infection.
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Objective To analyze the feasibility of the recombinant cholera toxin B subunit (rCTB) as a carrier protein candidate for the preparing of polysaccharide-protein conjugate, and to discuss the immune effects of tetanus toxoid (TT) as the carrier protein in mucosal delivery vaccine. Methods The refolded pentrumer protein, rCTB was obtained by genetic engineering methods. Then conjugated the refold-ed protein with group A meningococcal polysaccharide (GAMP) using the chemical method(ADH) ,the pol-ysaccharide-protein conjugates(GAMP-rCTB) were prepared. BALB/c mice were immunized either intraper-itoneally ( i. p. ) or intranasally ( i. n. ) with GAMP-rCTB. Moreover, GAMP-TT vaccine that TT as carrier proteins was i.n. immunized to the mice. The evaluation of immunology is performed. Results The conju-gates of polysaccharide-potein with the rCTB and TT as protein carrier both are able to elicit high level of GAMP specific IgG antibody in serum after i.n. immunization, and the conjugates can also elicit specific IgA antibody in lung lavage and intestinal mucosa. Conclusion rCTB and TT can both as the protein carri-er for polysaccharide-protein conjugate as mucosal vaccine. The route of intranasal may be more ways for im-mune function than i.p. immunization when rCTB is used as the carrier of the polysaccharide-protein conju-gates.