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Articles by M. Nejati
Total Records ( 5 ) for M. Nejati
  D. Norouzian , A. Akbarzadeh , L. Teimoori , M. Nejati and A. Faranghi
  The effects of pH on the activity of tyrosinase (EC 1.14.18.1) leading to the formation of l-3, 4-dihydroxyphenylalanine (l-dopa) by using l-tyrosine as a substrate in the presence of ascorbic acid were studied. The reaction obeyed Eq. (1) and (2). The values of KEB and PKEB were calculated to be -1x10-6 and 6 and those of KESB, PKESB were -2x10-6 and 6.7, respectively. Hydrogen ions inhibited tyrosinase activity competitively.
  S.D. Siadat , M. Kheirandish , D. Norouzian , Q. Behzadiyannejad , S. Najar Peerayeh , M. Zangeneh and M. Nejati
  Opsonophagocytosis mediated by antibody and complement is the major defense mechanism for clearing Neisseria meningitidis from the host. Therefore, a newly developed phagocytosis assay based on flow cytometry (flow assay) was using sera obtained from rabbit postvaccination with outer membrane vesicle of N. meningitidis serogroup B, was done in order to evaluation of the potential efficacy of (experimental) meningococcal vaccines. The Outer Membrane Vesicles (OMVs) and control were injected intramuscularly into groups of five rabbit with boosters on 14, 28 and 42 days after the primary immunization. The serum on 0, 14, 28, 42 and 56 days were collected and stored at -20°C for next analysis. Phagocytic function of and intracellular oxidative burst generation by rabbit polymorphonuclear (PMN), against N. meningitidis serogroup B, was measured with flow cytometer, using dihydrorhodamine-123 as probes, respectively. We use a Coulter Epics XL-profile (USA) with an argon laser operating at 488 nm. The results of quantitative flow cytometric analysis of rabbit PMN function in hyperimmun sera with OMVs revealed a highly significant increase in opsonophagocytic responses against serogroup B meningococci after 56 day in comparison with the control group (p<0.05). Present results indicated that OMVs could be as a candidate for vaccine toward serogroup B meningococci and a new standard flow cytometric method to measure the opsonophagocytosis activity by rabbit PMNs was shown by this study.
  S.D. Siadat , D. Norouzian , B. Tabaraie , H. Ahmadi , Q. Behzadiyannejad , S.N. Pirayeeh , M. Nejati and B.A. Motlagh
  In this study, polysaccharide obtained from Neisseria meningitidis serogroup A was purified according to published protocol of World Health Organization. The outer Membrane Vesicle (OMV) of meningococcal serogroup B was also extracted by ultracentrifuge employing deoxycholate reagent. The derivatives of polysaccharide of meningococcal serogroup A (GAMP) was conjugated to OMV of meningococcal serogroup B which was treated by 1-ethyl-3- (3 dimethylaminopropyl) carbodiimide (EDAC).The obtained polysaccharide was activated by cyanogen bromide (CNBr) and 1-cyano-4-dimethy laminopyridinium tetrafluoroborate (CDAP) separately. First Adipic acid dihydrazide (ADH) with EDAC was bound to GAMP activated with CNBr to form GAMPCNBr AH. Second ADH with EDAC was bound to GAMP activated with CDAP to form GAMPCDAP AH. Then these derivatives were conjugated to OMV by EDAC to form GAMPCNBr AH-OMV and GAMPCDAP AH-OMV. The yields of GAMPCDAPAH-OMV was 45 to 48% which was higher than that of the other prepared conjugate (15-17%). The glycoconjugates were shown to induce hyper immunity in rabbits and formed antibodies against the above mentioned conjugates were detected by immunodiffusion technique.
  S.D. Siadat , Q. Behzadiyannejad , B. Tabaraie , H. Ahmadi , D. Norouzian , S.N Pirayeeh , M. Nejati and M. Zangeneh
  Bacterial meningitis caused by different groups of Neisseria meningitidis is still one of the serious health problems world wide. The Serum Bactericidal Assay (SBA) to meningococci is the most important test in immunological evaluation of meningococcal infection after vaccination. The SBA has been adapted as the gold standard for immunity against different serogroups of Neisseria meningitidis after immunization. Capsular polysaccharide of serogroup A meningococci (CPSA) was conjugated to Outer Membrane Vesicle (OMV) from a serogroup B in order to test the possibility of obtaining a bivalent serogroup A and B meningococcus immunogen. The conjugate was prepared with adipic acid hydrazide (ADH) and 1-ethyl-3-(3-dimethylamino-propyl) carbodiimide (EDAC). The conjugate and control were injected intramuscularly into groups of five rabbit with boosters on days 14, 28 and 42 after the primary immunization. The following groups were used as control: 1-CPSA plus OMV; 2-CPSA; 3-OMV and 4-normal saline. The serum collected on days 0, 14, 28, 42 and 56 were tested by complement mediated bactericidal assay according to the world health organization protocol. The results of SBA in the glycoprotein conjugate group revealed a significant increase in serum bactericidal titer against serogroup A meningococci after 56 day in comparison with the CPSA and OMV control group. Bactericidal titer against serogroup B meningococci of the conjugate showed no significant difference in comparison with the OMV containing control. The results indicate that when polysaccharide A and OMV are in a covalent conjugate form, the complex is able to induce a high level of bactericidal antibody response. Therefore, this study shows that the CPSA--OMV conjugate could be a candidate for bivalent vaccine toward serogroup A and B meningococci.
  Q. Behzadiyannejad , S.D. Siadat , M. Kheirandish , B. Tabaraiee , H. Ahmadi , D. Norouzian , S. Najar Peerayeh , M. Nejati and M.H. Hedayati
  Production of effective vaccine formulations is dependent on the availability of assays for the measurement of protective immune responses. Antibody- and complement-mediated phagocytosis is the main defense mechanism against Neisseria meningitidis. Therefore, a newly developed phagocytosis assay based on flow cytometry (flow assay) and the Serum Bactericidal Activity (SBA) assay were using sera obtained from rabbit postvaccination with the Outer Membrane Vesicles (OMVs) of Neisseria meningitidis serogroup B was done in order to evaluation of the potential efficacy of (experimental) meningococcal vaccines. The OMVs were injected intramuscularly into of rabbits with boosters on days 14, 28 and 42 after the primary immunization. Phagocytic function of and intracellular oxidative burst generation by rabbit PMN, against Neisseria meningitidis serogroup B, was measured with flow cytometer (Coulter Epics-XL-Profile USA), using dihydrorhodamine-123 as probes, respectively. SBA titers are given as reciprocal Log 2 values of the dilution giving at least 50% killing of the inoculum measured as colony forming units. The results of SBA titers and quantitative flow cytometric analysis of rabbit PMN function in hyperimmun sera with the OMVs revealed a highly significant increase in opsonophagocytic responses and bactericidal antibody against serogroup B meningococci after 56 day (p< 0.05). Both SBA and opsonic activity are crucial for the protection against meningococcal disease. In conclusion, we have shown a very high correlation between opsonic activity and SBA (r = 0.91). Present results indicated that the OMVs could be as a candidate for vaccine toward serogroup B meningococci.
 
 
 
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