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The avidity maturation and immunoglobulin G (IgG) isotype distribution of antibodies after vaccination with a meningococcal B outer membrane vesicle (OMV) vaccine were evaluated as indicators of protective immunity. Pre- and postvaccination sera from 134 healthy toddlers (ages, 2 to 3 years) immunized with a monovalent meningococcal B OMV (serosubtype P1.7-2,4) vaccine adsorbed with AlPO(4) or Al(OH)(3) were analyzed by enzyme-linked immunosorbent assay (ELISA) methods. The children were vaccinated three times with intervals of 3 to 6 weeks between vaccinations or twice with an interval of 6 to 10 weeks between vaccinations. A booster was given after 20 to 40 weeks. The avidity index (AI) of antibodies increased significantly during the primary series of vaccinations and after the booster was given. No differences in AIs were found when the results obtained with the two vaccination schedules or with the two adjuvants were compared. After vaccination, IgG1 was the predominant IgG isotype, followed by IgG3. No IgG2 or IgG4 was detected. There was a strong correlation between serum bactericidal activity (SBA) and ELISA titers. When two subgroups with similar anti-OMV IgG levels were compared before and after the booster vaccination, the higher AI after the booster vaccination was associated with significantly increased SBA. We concluded that avidity maturation occurs after vaccination with a monovalent meningococcal B OMV vaccine, especially after boosting, as indicated by a significant increase in the AI. Vaccination with the monovalent OMV vaccine induced mainly IgG1 and IgG3 isotypes, which are considered to be most important for protection against meningococcal disease. An increase in the AI of antibodies is associated with increased SBA, independent of the level of specific IgG and the IgG isotype distribution. Measuring the AI and IgG isotype distribution of antibodies after vaccination can be a supplementary method for predicting protective immunity for evaluati

In the present study we investigated the role of the fibronectin (FN)- and fibrinogen (FGN)-binding protein (FBPS) in the pathogenesis of Streptococcus suis serotype 2 in piglets. The complete gene encoding FBPS from S. suis serotype 2 was cloned in Escherichia coli and sequenced. The occurrence of the gene in various serotypes was analyzed by hybridization studies. The FBPS protein was expressed in E. coli and purified, and binding to human FN and FGN was demonstrated. The induction of antibodies in piglets was studied upon infection. An isogenic mutant unable to produce FBPS was constructed, and the levels of virulence of the wild-type and mutant strains were compared in a competitive infection model in young piglets. Organ cultures showed that FBPS was not required for colonization of the tonsils but that FBPS played a role in the colonization of the specific organs involved in an S. suis infection. Therefore, the FBPS mutant was considered as an attenuated mutant.

The occurrence of 36 environmentally regulated genes of Streptococcus suis strain 10 among all 35 S. suis serotypes was determined by using hybridization with the amplified genes as probes. In addition, the distribution of these genes among the virulence phenotypes of serotypes 1 and 2 was assessed. Hybridization was also performed with various other streptococcal species and nonstreptococcal bacterial species which may be present in pigs. Interestingly, probe ivs-25/iri-1, similar to agrA and sapR, hybridized only with S. suis serotype 1 and 2 strains with virulent phenotypes and is therefore suitable as a diagnostic parameter. Only one probe was specific for S. suis. This probe's sequence was identical to the epf gene, a putative virulence factor of S. suis. Probe ivs-31 was similar to a virulence factor of S. suis, namely, a gene encoding a fibronectin- and fibrinogen-binding protein. This probe hybridized only with oral streptococci. Nearly half of the probes (45%) hybridized with the oral streptococci (S. oralis, S. milleri, S. sanguis, S. gordonii, and S. mitis) and with Streptococcus pneumoniae. This indicates a close relationship between S. suis, the oral streptococci, and S. pneumoniae with respect to the selected environmentally regulated genes. One probe only hybridized with gram-negative species and therefore seems to be obtained by S. suis from a gram-negative organism by horizontal transfer

RIVM rapport:Ter voorkoming van sterfte, morbiditeit en blijvende schade als gevolg van invasieve Hib-infecties heeft de Gezondheidsraad geadviseerd vaccinatie tegen Hib in het Rijksvaccinatieprogramma op te nemen, hetgeen in 1993 is gerealiseerd. Vaccinatie wordt aangeboden aan alle kinderen geboren sinds 1 april 1993. Om de effectiviteit van deze immunisatie te beoordelen is surveillance geindiceerd. In dit rapport over de surveillance van invasieve infecties door Haemophilus influenzae (Hi) door het Nederlands Surveillance-Centrum Kindergeneeskunde (NSCK) en het Nederlands Referentie Laboratorium voor Bacteriele Meningitis (RBM) in de periode 1994-1996 wordt het voortschrijdende effect van Hib vaccinatie duidelijk. Het aantal gevallen van invasieve Hi-infectie was 179 in 1994, 68 in 1995 en 40 in 1996. Dit betekent een belangrijke vermindering vergeleken met de geschatte aantallen van voor de start van vaccinatie. De daling vond plaats bij alle klinische ziektebeelden. Een verschuiving in de leeftijdsverdeling vond plaats, wat verklaard kan worden door de geleidelijke invoering van immunisatie vanaf april 1993. In 1994 manifesteerde nog drie kwart van de invasieve Hi-infecties zich als meningitis, in 1996 was dit nog de helft van het totale aantal aan het RBM gerapporteerde gevallen. Vanaf 1 januari 1995 werd de casus-definitie voor de NSCK surveillance veranderd naar invasieve Hi-infecties ongeacht het serotype. Als gevolg hiervan werd het ook mogelijk om invasieve Hi-ziektebeelden veroorzaakt door niet serotype b stammen te bestuderen. Serotypering werd door het RBM verricht bij alle ingestuurde stammen. Het deel van de gevallen in het NSCK systeem waarbij serotypering plaatsvond steeg van 84% in 1994 tot ruim 90% in 1996. De gegevens van het RBM tonen een duidelijke daling in het deel van de invasieve Hi-infecties veroorzaakt door serotype b. Zeven gevallen van echt vaccin-falen, 4 van schijnbaar- en 2 van mogelijk vaccin-falen werden geregistreerd. In de toekomst zal het, To prevent mortality, severe morbidity and permanent disability due to invasive Hib infection, the National Health Council had recommended including immunisation against Hib in the National Immunisation Programme , which was realised in 1993. The vaccine is offered to all children born after 1 April 1993. To assess the effectiveness of this immunisation, surveillance of invasive infections caused by Haemophilus influenzae (Hi) was carried out from 1994-96 by the Dutch Paediatric Surveillance Unit (NSCK) and the Netherlands Reference Laboratory for Bacterial Meningitis (RBM). The progressive effect of Hib vaccination was evident in the decreasing number of cases of invasive Hi infection registered by the surveillance systems: 179 in 1994, 68 in 1995 and 40 in 1996. This trend resulted in a substantial reduction compared to the estimated numbers before the start of vaccination. The decrease was also evident in the individual clinical pictures. The observed shift in the age distribution is explained by the gradual introduction of immunisation from April 1993 onwards. In 1994 three-quarters of the invasive Hi infections presented as meningitis, in 1996 meningitis accounted for half the total number of cases reported to the RBM. Since January 1995 the case definition used for the NSCK surveillance was changed to invasive Hi disease, irrespective of serotype. This made it possible to study invasive Hi disease caused by non-serotype b strains as well. Serotyping was performed by the RBM on all strains submitted. The proportion of cases in the NSCK unit where serotyping is performed increased from 84% in 1994 to more than 90% in 1996. The RBM data show a clear decrease in the proportion of invasive Hi infection caused by serotype b. Seven cases of true vaccine failure, 4 of apparent and 2 of possible vaccine failure occurred. In future the RBM will collect additional immunological data for evaluating cases of vaccine failure.