Levels Of Serum Bactericidal Activity Research Articles

A preliminary study on the application of PspA as a carrier for group A meningococcal polysaccharide.

This study aimed to explore the feasibility of pneumococcal surface protein A (PspA) as a carrier protein. Three recombinant pneumococcal surface proteins from three different clades were expressed by the prokaryotic expression system and conjugated to group A meningococcal polysaccharide (GAMP) to generate three polysaccharide-protein conjugates. The conjugates, unconjugated proteins, GAMP, and GAMP-TT vaccine bulk (used as positive control) were immunized into mice, and their immune effects were assessed by the methods of enzyme-linked immunosorbent assay (ELISA), flow cytometry (FCM), and serum bactericidal assay (SBA). The results showed that the polysaccharide-protein conjugates could produce higher levels of anti-GAMP IgG titers (P < 0.05), higher ratios of Th1/Th2 (P < 0.05), and higher levels of serum bactericidal activity (P < 0.05), compared with the unconjugated GAMP. The conjugation of PspAs to GAMP also enhanced the anti-PspA responses compared with unconjugated PspAs except for PspA3. In conclusion, the results indicated that the three PspAs were appropriate carrier proteins, as demonstrated by the characteristics of T-cell dependent responses to the GAMP, and might protect against group A of epidemic cerebrospinal meningitis.

Vaccine-induced antibody level as the parameter of the influence of environmental salinity on vaccine efficacy in Nile tilapia

To effectively increase production and improve economic returns, the co-culture of Nile tilapia (Oreochromis niloticus) and marine shrimp has been adopted in many countries, including China. Although O. niloticus is an euryhaline fish that can tolerate elevated salinities and even full-strength seawater, fluctuations in salinity levels can undoubtedly induce stress and affect the immune response of this fish. Therefore, this study assessed the impact of salinity on vaccine efficacy in Nile tilapia, which used serum antibody level as a surrogate marker to detect vaccine efficacy. Nile tilapia were acclimatized to 0, 10, 20, or 30 ppt salinity, and then immunized with a formalin-inactivated Streptococcus agalactiae vaccine. Significantly lower levels of antibody in vaccinated fish were found at 20 and 30 ppt salinity compared to 0 and 10 ppt salinity. White blood cell counts, absolute blood lymphocyte counts, and serum bactericidal activity levels were all significantly lower in vaccinated fish at 20 and 30 ppt salinity. Elevated cortisol levels were detected in all of the fish exposure to salinity. Concentrations of serum electrolytes (Na+ and Cl−) were significantly higher in fish at 30 ppt salinity, as compared to fish at lower salinities. Furthermore, the mRNA transcription levels of three of the immune-related genes analyzed (IgM, IL-1β, and IFN-γ, but not Hsp70) were significantly inhibited in the vaccinated fish at 20 and 30 ppt salinity. A suppressed immune response and decreased vaccine efficacy were also indicated by the lower survival rate of vaccinated fish at 20 ppt salinity when challenged with S. agalactiae. Therefore, salinities ≥20 ppt negatively affected antibody production in Nile tilapia, ultimately affecting vaccine efficacy.

Comparison of serum bactericidal and antibody titers induced by two Haemophilus influenzae type b conjugate vaccines: A phase III randomized double-blind study

Haemophilus influenzae type b (Hib) conjugate vaccines have drastically reduced disease incidence worldwide. Protection against Hib infection has relied on the serum bactericidal activity (SBA) of antibodies to the Hib capsular polysaccharide (polyribosylribitol phosphate). However, licensure usually relies on measuring induction of antibodies to PRP as a surrogate for SBA. In a phase III clinical trial we compared a PRP-conjugate vaccine using the nontoxic diphtheria toxin mutant, CRM197, as carrier protein with the licensed tetanus toxoid conjugate when administered subcutaneously as a three dose primary series in Japanese infants. As an addition to the phase III study, we have now evaluated SBA and show PRP-CRM197 induces higher levels of SBA than PRP-T four weeks after the primary series, with a statistically significant correlation with anti-PRP titers. This data confirms the superior immunogenicity of PRP-CRM197 compared with PRP-T assessed as SBA following a three-dose primary series by subcutaneous administration.Clinical trial registry: Registered on ClinicalTrials.gov (NCT01379846).

Loss of Humoral and Cellular Immunity to Invasive Nontyphoidal Salmonella during Current or Convalescent Plasmodium falciparum Infection in Malawian Children.

ABSTRACTInvasive nontyphoidal Salmonella (iNTS) infections are commonly associated with Plasmodium falciparum infections, but the immunologic basis for this linkage is poorly understood. We hypothesized that P. falciparum infection compromises the humoral and cellular immunity of the host to NTS, which increases the susceptibility of the host to iNTS infection. We prospectively recruited children aged between 6 and 60 months at a Community Health Centre in Blantyre, Malawi, and allocated them to the following groups; febrile with uncomplicated malaria, febrile malaria negative, and nonfebrile malaria negative. Levels of Salmonella enterica serovar Typhimurium-specific serum bactericidal activity (SBA) and whole-blood bactericidal activity (WBBA), complement C3 deposition, and neutrophil respiratory burst activity (NRBA) were measured. Levels of SBA with respect to S. Typhimurium were reduced in febrile P. falciparum-infected children (median, −0.20 log10 [interquartile range {IQR}, −1.85, 0.32]) compared to nonfebrile malaria-negative children (median, −1.42 log10 [IQR, −2.0, −0.47], P = 0.052). In relation to SBA, C3 deposition on S. Typhimurium was significantly reduced in febrile P. falciparum-infected children (median, 7.5% [IQR, 4.1, 15.0]) compared to nonfebrile malaria-negative children (median, 29% [IQR, 11.8, 48.0], P = 0.048). WBBA with respect to S. Typhimurium was significantly reduced in febrile P. falciparum-infected children (median, 0.25 log10 [IQR, −0.73, 1.13], P = 0.0001) compared to nonfebrile malaria-negative children (median, −1.0 log10 [IQR, −1.68, −0.16]). In relation to WBBA, S. Typhimurium-specific NRBA was reduced in febrile P. falciparum-infected children (median, 8.8% [IQR, 3.7, 20], P = 0.0001) compared to nonfebrile malaria-negative children (median, 40.5% [IQR, 33, 65.8]). P. falciparum infection impairs humoral and cellular immunity to S. Typhimurium in children during malaria episodes, which may explain the increased risk of iNTS observed in children from settings of malaria endemicity. The mechanisms underlying humoral immunity impairment are incompletely understood and should be explored further.

The rate of liver impairment, character of bacteremia and serum bactericidal activity in patients with cirrhosis.

Dependence of prevalence and severity of bacteremia on the rate of liver impairment, serum bactericidal activity (SBA), and serum concentrations of C-reactive protein (CRP) and granulocyte colony-stimulating factor (G-CSF) in 80 hospitalized patients with liver cirrhosis (LC) have been studied. It was shown that risk factors associated with the development of bacteremia are high by Child-Pugh score and low SBA, CRP and G-CSF levels. Patients with LC, class A had the highest SBA, CRP and G-CSF levels. Still 14,3% of them developed less severe bacteremia associated with one type of microorganisms isolated from blood. Patients with LC, class B had intermediate SBA, CRP and G-CSF levels. They developed severe bacteremia in 52,6% of cases and less severe bacteremia – in 21,1% of cases. Patients with LC, class C had low SBA, CRP and G-CSF levels. They developed severe bacteremia in 62,5% of cases and less severe bacteremia – in 25% of cases.

The Adhesin Complex Protein (ACP) of Neisseria meningitidis Is a New Adhesin with Vaccine Potential

ABSTRACTThe acp gene encoding the 13-kDa adhesin complex protein (ACP) from Neisseria meningitidis serogroup B strain MC58 was cloned and expressed in Escherichia coli, and the purified recombinant ACP (rACP) was used for immunization studies. Analysis of the ACP amino acid sequences from 13 meningococcal strains, isolated from patients and colonized individuals, and 178 strains in the Bacterial Isolate Genome Sequence (BIGS) database showed the presence of only three distinct sequence types (I, II, and III) with high similarity (>98%). Immunization of mice with type I rACP in detergent micelles and liposomes and in saline solution alone induced high levels of serum bactericidal activity (SBA; titers of 1/512) against the homologous strain MC58 and killed strains of heterologous sequence types II and III with similar SBA titers (1/128 to 1/512). Levels of expression of type I, II, or III ACP by different meningococcal strains were similar. ACP functioned as an adhesin, as demonstrated by reduced adherence of acp knockout (MC58 ΔACP) meningococci to human cells in vitro and the direct surface binding of rACP and by the ability of anti-rACP sera to inhibit adherence of wild-type bacteria. ACP also mediated the invasion of noncapsular meningococci into human epithelial cells, but it was not a particularly impressive invasin, as the internalized bacterial numbers were low. In summary, the newly identified ACP protein is an adhesin that induces cross-strain bactericidal activity and is therefore an attractive target antigen for incorporation into the next generation of serogroup B meningococcal vaccines.

Hyperproliferation of B Cells Specific for a Weakly Immunogenic PorA in a Meningococcal Vaccine Model

Highly homologous meningococcal porin A (PorA) proteins induce protective humoral immunity against Neisseria meningitidis group B infection but with large and consistent differences in the levels of serum bactericidal activity achieved. We investigated whether a poor PorA-specific serological outcome is associated with a limited size of the specific B-cell subpopulation involved. The numbers of PorA-specific splenic plasma cells, bone marrow (BM) plasma cells, and splenic memory B cells were compared between mice that received priming and boosting with the weakly immunogenic PorA (P1.7-2,4) protein and those that received priming and boosting with the highly immunogenic PorA (P1.5-1,2-2) protein. Immunoglobulin G (IgG) titers (except at day 42), bactericidal activity, and the avidity of IgG produced against P1.7-2,4 were significantly lower at all time points after priming and boosting than against P1.5-1,2-2. These differences, however, were not associated with a lack of P1.7-2,4-specific plasma cells. Instead, priming with both of the PorAs resulted in the initial expansion of comparable numbers of splenic and BM plasma cells. Moreover, P1.7-2,4-specific BM plasma cells, but not P1.5-1,2-2-specific plasma cells, expanded significantly further after boosting. Likewise, after a relative delay during the priming phase, the splenic P1.7-2,4-specific memory B cells largely outnumbered those specific for P1.5-1,2-2, upon boosting. These trends were observed with different vaccine formulations of the porins. Our results show for the first time that B-cell subpopulations involved in a successfully maturated antibody response against a clinically relevant vaccine antigen are maintained at smaller population sizes than those associated with poor affinity maturation. This bears consequences for the interpretation of immunological memory data in clinical vaccine trials.

Neonatal immune response and serum bactericidal activity induced by a meningococcal conjugate vaccine is enhanced by LT-K63 and CpG2006

Neonates have a poorly developed immune system. Therefore it is important to develop vaccination strategies that induce protective immunity and immunological memory against pathogens early in life. The immunogenicity of a meningococcal serogroup C polysaccharide conjugate (MenC-CRM 197) was assessed in neonatal mice, and effects of LT-K63 and CpG2006 and immunisation routes were compared. Neonatal mice were primed subcutaneously (s.c.) or intranasally (i.n.) with MenC-CRM 197 with or without LT-K63 or CpG2006 and re-immunised 16 and 30 days later by the same route and formulation. Antibody levels were measured and generation of immunological memory assessed by affinity maturation and kinetics of the Ab response. Serum bactericidal activity (SBA) was measured to evaluate protective efficacy. The second and third dose of MenC-CRM 197 mixed with either LT-K63 or CpG2006 induced a rapid increase in MenC-specific IgG antibodies, to levels higher than elicited by MenC-CRM 197 alone ( P < 0.01) and in unimmunised mice ( P < 0.001), indicating efficient generation of memory by priming through both s.c. and i.n. routes. SBA was detected after three s.c. immunisations with MenC-CRM 197 s.c. alone. However, only two doses of MenC-CRM 197+LT-K63 or MenC-CRM 197+CpG2006 were needed to induce SBA levels > 16. LT-K63 and CpG2006 enhanced neonatal antibody responses, affinity maturation, immunological memory to the conjugate MenC-CRM 197 and protective immunity. These results encourage the development of neonatal vaccination strategies to induce protective immunity and immunological memory against meningococcal disease.

Protection by Natural Human Immunoglobulin M Antibody to Meningococcal Serogroup B Capsular Polysaccharide in the Infant Rat Protection Assay Is Independent of Complement-Mediated Bacterial Lysis

Neisseria meningitidis, an important cause of bacterial meningitis and septicemia worldwide, is associated with high mortality and serious sequelae. Natural immunity against meningococcal disease develops with age, but the specificity and functional activity of natural antibodies associated with protection are poorly understood. We addressed this question by using a selected subset of prevaccination sera (n = 26) with convergent or discrepant serum bactericidal activity (SBA) and infant rat protective activity (IRPA) against the serogroup B meningococcal strain 44/76-SL (B:15:P1.7,16) from Icelandic teenagers. The sera were analyzed by opsonophagocytic activity (OPA) assay, immunoblotting, immunoglobulin G (IgG) quantitation against live meningococcal cells by flow cytometry, and enzyme immunosorbent assay (EIA). High levels of SBA and OPA were reflected in distinct IgG binding to major outer membrane proteins and/or lipopolysaccharide in immunoblots. However, we could not detect any specific antibody patterns on blots that could explain IRPA. Only IgM antibody to group B capsular polysaccharide (B-PS), measured by EIA, correlated positively (r = 0.76, P < 0.001) with IRPA. Normal human sera (NHS; n = 20) from healthy Finnish children of different ages (7, 14, and 24 months and 10 years) supported this finding and showed an age-related increase in IRPA that coincided with the acquisition of B-PS specific IgM antibody. The protection was independent of complement-mediated bacterial lysis, as detected by the inability of NHS to augment SBA in the presence of human or infant rat complement and the equal protective activity of NHS in rat strains with fully functional or C6-deficient complement.

Serum bactericidal activity correlates with the vaccine efficacy of outer membrane vesicle vaccines against Neisseria meningitidis serogroup B disease

For evaluation of serum bactericidal activity (SBA) as surrogate for the efficacy of outer membrane vesicle (OMV) vaccines against Neisseria meningitidis serogroup B disease, we have reanalyzed data from a randomized double blind placebo-controlled efficacy trial involving 172,000 secondary school students (aged 13–14 years) in Norway (1988–1991). A cohort of the efficacy trial consisting of 880 individuals was selected for immunogenicity studies. An efficacy of 87% was calculated for a 10-month observation period. However, after an observation period of 29 months, the estimated efficacy against group B disease induced by vaccination was 57%. The immunogenicity study showed that the SBA geometric mean titer (GMT) for the vaccinees was 2.4 before vaccination and 19.0 six weeks after the second vaccine dose. One year after vaccination the GMT was reduced to 2.8. A separate three-dose study with 304 adolescents showed that with a third dose at 10 months after the second dose (i.e. when cases of disease started to appear) a strong booster response was induced. Ten months after the second dose the SBA was reduced to near pre-immunization level. Following the third dose the SBA geometric mean titer of 2.7 increased to 62.3. One year after the third dose, the GMT was markedly higher than 6 weeks after the second dose (12.6 versus 8.8). Thus, protection after vaccination corresponds with the level of SBA. In order to reach lasting protective levels of SBA in a population, three vaccine doses are probably required. Measurements of SBA are likely to be useful for evaluating various upcoming formulations and improvements of immunization regimens for OMV vaccines.

Potential of clindamycin in addition to vancomycin for the treatment of oxacillin-resistant Staphylococcus aureus septicemia persisting under vancomycin therapy

We observed seven patients with persistent fever and staphylococcemia under vancomycin-containing antimicrobial regimens who promptly improved as clindamycin was added to the initial antibiotics. Moreover, in all these patients a striking increase in peak and trough serum inhibitory activity (SIR) and serum bactericidal activity (SBA) levels was observed after addition of clindamycin. SIA and SBA levels after administration of a single dose of vancomycin (500 mg), clindamycin (600 mg) or vancomycin + clindamycin were also measured in three healthy volunteers against six ORSA isolates. Unsatisfactory peak SBA levels (0% of cases ⩾ 1:8) were obtained after vancomycin administration. Vice versa, peak SBA levels ⩾ 1:8 were obtained in 94% of the cases after clindamycin and in 100% of cases after vancomycin + clindamycin. Time-kill studies showed a borderline or incomplete bactericidal activity of vancomycin against three ORSA isolates from infections that manifested poor or slow response to vancomycin therapy. The combination with clindamycin did not result in a synergistic interaction between the two drugs. It is concluded that addition of clindamycin may be useful in some cases of ORSA septicemia that show poor or slow response to vancomycin therapy. The recommendation for a wider use of this combination of antibiotics requires further documentation of efficacy.

Characterization of some parameters of non-specific immunity in beef cattle (II).

Serum protein, immunoglobulins, complement, lysozyme, serum bactericidal activity and blast transformation of peripheral blood lymphocytes were tested in beef cattle in different herds and age groups. These parameters were evaluated in their time-kinetics, in comparison with age-matched groups of dairy cattle. Like dairy calves, beef calves up to 4 months of age were shown to have low levels of serum bactericidal activity and haemolytic complement; besides, a worse profile was detected in serum protein and gamma 2 globulin levels. Al(OH)3 and oil-adjuvanted vaccines had a favourable influence on immunoglobulin and lysozyme synthesis. An acute stressing event like transportation was shown to decrease mitogen-driven lymphocyte stimulation for at least 10 days after arrival.