Biomedical subjects

R H Sandin

Publications and source records attributed to R H Sandin.

7 recordsLinked to original sources

PubMed2004

Selection and characterization of cyclic peptides that bind to a monoclonal antibody against meningococcal L3,7,9 lipopolysaccharides.

There is still no general vaccine for prevention of disease caused by group-B meningococcal strains. Meningococcal lipopolysaccharides (LPSs) have received attention as potential vaccine candidates, but concerns regarding their safety have been raised. Peptide mimics of LPS epitopes may represent safe alternatives to immunization with LPS. The monoclonal antibody (MoAb) 9-2-L3,7,9 specific for Neisseria meningitidis LPS immunotype L3,7,9 is bactericidal and does not cross-react with human tissue. To explore the possibility of isolating peptide mimics of the epitope recognized by MoAb 9-2-L3,7,9, we have constructed two phage display libraries of six and nine random amino acids flanked by cysteines. Furthermore, we developed a system for the easy exchange of peptide-encoding sequences from the phage-display system to a hepatitis B core (HBc) expression system. Cyclic peptides that specifically bound MoAb 9-2-L3,7,9 at a site overlapping with the LPS-binding site were selected from both libraries. Three out of four tested peptides which reacted with MoAb 9-2-L3,7,9 were successfully presented as fusions to the immunodominant loop of HBc particles expressed in Escherichia coli. However, both peptide conjugates to keyhole limpet haemocyanin and HBc particle fusions failed to give an anti-LPS response in mice.

Animals↗

PubMed2003

Comparison of functional immune responses in humans after intranasal and intramuscular immunisations with outer membrane vesicle vaccines against group B meningococcal disease.

A serogroup B meningococcal outer membrane vesicle (OMV) vaccine was delivered either intranasally or intramuscularly to 12 and 10 volunteers, respectively. The mucosal vaccine was given as four weekly doses followed by a fifth dose after 5 months; each dose consisted of OMVs equivalent to 250 microg of protein. The intramuscular (i.m.) vaccine, consisting of the same OMVs but adsorbed to Al(OH)(3), was administered as three doses each of 25 microg of protein, with 6 weeks interval between first and second doses and the third dose after 10 months. Both groups of vaccinees demonstrated significant immune responses when measured as specific IgG antibodies against live meningococci, as serum bactericidal activity (SBA) and as opsonophagocytic activity. Two weeks after the last dose, the anti-meningococcal IgG concentrations were significantly higher in the i.m. group (median IgG concentration: 43.1 microg/ml) than in the intranasal group (10.6 microg/ml) (P=0.001). The corresponding opsonophagocytic activity was 7.0 and 3.0 (median log(2) titre) (P=0.001), and the SBA was 5.0 and 2.0 (median log(2) titre) (P=0.005), for the i.m. and intranasal groups, respectively. The last immunisation induced an enhanced immune response in the i.m. group, whereas the intranasal group showed no significant booster response. Accordingly, affinity maturation of anti-OMV-specific IgG antibodies was seen only after i.m. vaccination. The IgG1 subclass dominated the responses in both groups, whereas the significant IgG3 responses observed in the i.m. group were absent in the intranasal group. Although the intranasal OMV vaccination schedule used here induced functional immune responses relevant to protection, an improved vaccine formulation and/or a modified mucosal immunisation regimen may be needed to achieve a systemic effect comparable to that seen after three doses of intramuscular vaccination.

Administration, Intranasal↗

PubMed2003

Binding properties and anti-bacterial activities of V-region identical, human IgG and IgM antibodies, against group B Neisseria meningitidis.

We have constructed chimaeric (ch) mouse/human antibodies with identical binding regions isolated from the V-genes of two mouse parent hybridoma cell lines, with specificity against the P1.7 and P1.16 epitopes on the outer-membrane protein PorA on meningococci. The chimaeric antibodies can be used to analyse relationships between specificity, binding activity (avidity and kinetics), isotype (antibody class and antibody subclass) and in vitro anti-bacterial activity of meningococcal antibodies. The antibody sets represented the human isotypes IgG1, IgG3 and IgM, which dominate during immune response against protein antigens. The binding activities were quite similar for all these isotypes, surprisingly also for the pentameric IgM. Interestingly, monomeric IgM, prepared from pentameric IgM by partially reduction and alkylation, had similar binding activities as the original pentameric IgM. Regarding in vitro anti-bacterial activity, chIgG1 was superior in SBA (serum bactericidal activity) compared with chIgG3, while chIgG3 was more efficient in OP (opsonophagocytosis; measured by flow cytometry) than chIgG1. ChIgM showed slightly higher SBA than chIgG1 on molar basis, and much higher OP than chIgG3 and chIgG1. A lower concentration of antibodies was needed against the P1.16 than against the P1.7 epitope to induce SBA, but this was not the case for OP.

Anti-Bacterial Agents↗

PubMed2000

Awareness during anaesthesia: a prospective case study.

BACKGROUND: Patients who are given general anaesthesia are not guaranteed to remain unconscious during surgery. Knowledge about the effectiveness of current protective measures is scarce, as is our understanding of patients' responses to this complication. We did a prospective case study to assess conscious awareness during anaesthesia. METHODS: 11785 patients who had undergone general anaesthesia were interviewed for awareness on three occasions: before they left the post-anaesthesia care unit, and 1-3 days and 7-14 days after the operation. FINDINGS: We identified 18 cases of awareness and one case of inadvertent muscle blockade that had occurred before unconsciousness. Incidence of awareness was 0.18% in cases in which neuromuscular blocking drugs were used, and 0.10% in the absence of such drugs. 17 cases of awareness were identified at the final interview, but no more than 11 would have been detected if an interview had been done only when the patients left the post-anaesthesia care unit. Four non-paralysed patients recalled intraoperative events, but none had anxiety during wakefulness or had delayed neurotic symptoms. This finding contrasts with anaesthesia with muscle relaxants, during which 11 of 14 patients had pain, anxiety, or delayed neurotic symptoms. After repeated discussion and information, the delayed neurotic symptoms resolved within 3 weeks in all patients. Analysis of individual cases suggests that a reduced incidence of recall of intraoperative events would not be achieved by monitoring of end-tidal anaesthetic gas concentration or by more frequent use of benzodiazepines. INTERPRETATION: The inability to prevent awareness by conventional measures may advocate monitoring of cerebral activity by neurophysiological techniques. However, the sensitivity of such techniques is not known, and in the light of our findings, at least 861 patients would need to be monitored to avoid one patient from suffering due to awareness during relaxant anaesthesia.

Adult↗

PubMed1998

Recurrent respiratory depression after total intravenous anaesthesia with propofol and alfentanil.

Since first commented upon by Lamarche in 1984, several cases of recurrent respiratory arrest after alfentanil infusions have been reported. In all these cases the alfentanil infusions have been used to supplement conventional anaesthetic techniques with nitrous oxide and/or inhalational agents and in most cases rather high total alfentanil doses have been administered. We have seen two cases of severe recurrent respiratory depression in healthy patients after relatively minor procedures performed under total intravenous anaesthesia with propofol-alfentanil infusions, air-oxygen ventilation and muscle relaxation, where the alfentanil doses administered were quite small. These cases are presented in detail and compared within a tabulated presentation with the earlier published cases of alfentanil-related recurrent respiratory depression.

Adult↗

PubMed1994

One disulfide bond in front of the second heavy chain constant region is necessary and sufficient for effector functions of human IgG3 without a genetic hinge.

We have created four IgG3 mutants without a normal hinge region: (i) m0 without a genetic hinge; (ii) m0/C131S, where Cys-131 in m0 was mutated to Ser; (iii) m0/231C232 (formerly HM-1), where a Cys residue was inserted in m0 between Ala-231 and Pro-232; (iv) m0/C131S/231C232, which is a hybrid of m0/231C232 and m0/C131S. The wild-type IgG3 and all mutants bind 5-iodo-4-hydroxy-3-nitrophenacetyl groups. The wild type and mutants, m15 (with 15 aa in the hinge), m0/231C232, and m0/C131S/231C232, were all positive for complement-mediated lysis, antibody-dependent cellular cytotoxicity mediated by peripheral blood leukocytes, and phagocytosis by U937. m0/C131S/231C232 was only weakly positive and sometimes negative for respiratory burst activity mediated by peripheral blood neutrophils (polymorphonuclear leukocytes), whereas m15, m0/231C232, and wild-type IgG3 were strongly positive. The m0 and m0/C131S mutants were mainly negative for complement-mediated lysis, antibody-dependent cell-mediated cytotoxicity, and phagocytosis by U937 and polymorphonuclear leukocytes. The results indicate that a hinge spacer region is not necessary, but the correct alignment of the two second heavy chain constant regions in the IgG3 molecule by a minimum of one disulfide bond is necessary and sufficient for effector functions.

Amino Acid Sequence↗

PubMed1994

Human IgG isotype-specific amino acid residues affecting complement-mediated cell lysis and phagocytosis.

In this report we describe the construction of anti-5-iodo-4-hydroxy-3-nitrophenacetyl (NIP) mouse/human immunoglobulin (Ig) G4 chimeric molecules with altered amino acid residues in the CH2 domain. Three mutants are described. Gln-268 is substituted by His in gamma 4 Q268H, Ser-331 is substituted by Pro in gamma 4 S331P, and in gamma 4 Q268H/S331P both residues are substituted. The ability of the mutant molecules to induce complement-mediated cell lysis (CML) and phagocytosis by Fc gamma RII- and Fc gamma RIII-bearing polymorphonuclear leukocytes (PMN) were measured. In CML, gamma 4 Q268H was inactive, but both gamma 4 S331P and gamma 4 Q268H/S331P were active provided that the antigenic density on the target cells was high. In phagocytosis mediated by PMN, the mutants gamma 4 S331P and gamma 4 Q268H/S331P were both active only when complement was introduced. gamma 4 Q268H was not active in phagocytosis under any conditions. We conclude that His-268 in human IgG molecules does not modulate CML activity or phagocytosis mediated by Fc gamma RII and/or Fc gamma RIII. Pro-331 rescues CML activity in IgG4 molecules when the epitope density on the target cells is high, but does not affect Fc gamma RII/Fc gamma RIII-mediated phagocytosis. In this manner the mutants gamma 4 S331P and gamma 4 Q268H/S331P mimic human IgG2. This could indicate a structural similarity between IgG2 and these mutant molecules that distinguish them from both IgG1 and IgG3.

Animals↗