Evaluation of Haemophilus influenzae type b carrier status among children 10 years after the introduction of Hib vaccine in Brazil

The aim of the present study was to assess the prevalence of Haemophilus influenzae type b (Hib) nasopharyngeal (NP) colonisation among healthy children where Hib vaccination using a 3p+0 dosing schedule has been routinely administered for 10 years with sustained coverage (> 90%). NP swabs were collected from 2,558 children who had received the Hib vaccine, of whom 1,379 were 12-< 24 months (m) old and 1,179 were 48-< 60 m old. Hi strains were identified by molecular methods. Hi carriage prevalence was 45.1% (1,153/2,558) and the prevalence in the 12-< 24 m and 48-< 60 m age groups were 37.5% (517/1,379) and 53.9% (636/1,179), respectively. Hib was identified in 0.6% (16/2,558) of all children in the study, being 0.8% (11/1,379) and 0.4% (5/1,179) among the 12-< 24 m and 48-< 60 m age groups, respectively. The nonencapsulate Hi colonisation was 43% (n = 1,099) and was significantly more frequent at 48-< 60 m of age (51.6%, n = 608) compared with that at 12-< 24 m of age (35.6%, n = 491). The overall resistance rates to ampicillin and chloramphenicol were 16.5% and 3.7%, respectively; the co-resistance was detected in 2.6%. Our findings showed that the Hib carrier rate in healthy children under five years was very low after 10 years of the introduction of the Hib vaccine.     

Transmission of Haemophilus influenzae type b strains among children attending day-care centers and orphanages

Goal of the work was to evaluate the differences level among H. influenzae strains of b serotype isolated from children attending day-care centres and orphanages and among strains isolated from invasive infections. In the work PFGE in Hib strains transmission examination and for epidemiological studies among three sources of invasive infection was applied. Among 35 Hib strains tested and control strain 8 different pulsotyped were found. Among 21 strains colonising the nasopharynx of healthy children, and among 13 Hib strains isolated from cerebrospinal fluid, 6 and 1 pulsotypes were found, respectively. Results obtained show that healthy children might be colonizing with genotypes characteristic for Hib strains isolated from invasive infections. In this view wider Hib vaccination seems be expected, as Hib circulation is common.     

Haemophilus influenzae meningitis in Manitoba and the Keewatin District,NWT: potential for mass vaccination.

A community-based surveillance study of all central nervous system infections was carried out in Manitoba and the Keewatin District, NWT, between Apr. 1, 1981, and Mar. 31, 1984. There were 201 cases of bacterial meningitis in Manitoba over the study period, 81 (40%) caused by Haemophilus influenzae; all but one isolate tested were type b (Hib). There were nine cases of H. influenzae meningitis in the Keewatin District. The overall annual incidence rate of H. influenzae meningitis in Manitoba was 2.5/100,000; for children under 5 years the rate was 32.1/100,000. For the Keewatin District the corresponding rates were 69.6/100,000 and 530/100,000. A total of 85% and 100% of the cases of H. influenzae meningitis occurred by 24 months of age in Manitoba and the Keewatin District respectively. The age at onset was earlier in native Indian children (22 cases) and Inuit children (9 cases) than in non-native children (59 cases) (p less than 0.005); thus, vaccine prevention of Hib meningitis will likely be more difficult in native Indian and Métis children. Without evaluating the increased potential of H. influenzae vaccines to prevent nonmeningitic forms of disease, we concluded that mass childhood vaccination with polyribosylribitolphosphate (PRP) vaccine is not warranted in Manitoba or the Keewatin District. Immunogenicity studies suggest that administration of conjugated Hib vaccines such as PRP-D in infancy may prevent approximately one-third to two-thirds of cases of H. influenzae meningitis; these vaccines warrant consideration for use in mass childhood vaccination programs.     

Recent trends in pediatric Haemophilus influenzae type B infections in Canada. Immunization Monitoring Program,Active (IMPACT) of the Canadian Paediatric Society and the Laboratory Centre for Disease Control.

OBJECTIVE: To describe changes in the number of cases of Haemophilus influenzae type b (Hib) infections among Canadian children before and after the introductory phases of Hib vaccination. DESIGN: Multicentre case series. SETTING: All 10 pediatric tertiary care centres across Canada participating in the Immunization Monitoring Program, Active (IMPACT) of the Canadian Paediatric Society and the Laboratory Centre for Disease control. PATIENTS: Children with a Hib infection admitted to any of the participating hospitals from 1985 to 1994. Annual case totals from 1985 to 1990 were determined from records of hospital laboratories or coded discharge diagnoses, or both. From 1991 to 1994 intensive case surveillance was conducted on the wards in addition to thorough record searches as above. OUTCOME MEASURES: Estimated annual case totals for 1985-90. For 1991-94 intensive surveillance for quarterly case totals, yearly age distribution of cases, and proportion of recent cases that represent vaccination failures or missed opportunities to prevent infection. RESULTS: The total number of Hib cases from 1985 to 1990 was 2095; from 1991 to 1994, there were 326 laboratory-confirmed cases and 15 probably cases supported by Hib antigen detection. The annual number of cases declined from an estimated 485 in 1985 to 24 in 1994, a decrease of 95.1%. The steepest interannual decrease (63.7%) occurred between 1992 and 1993, following the introduction of infant-based vaccination programs across Canada. The number of Hib cases involving children most at risk (those 6 to 18 months old) decreased from 78 in 1991 to 4 in 1994. Of the 24 cases in 1994, 6 were categorized as preventable, 1 was fatal, and 8 were vaccine failures (2 of which involved currently used vaccines). CONCLUSION: The prevalence of Hib infections reported by the IMPACT centres has declined greatly since the introduction of vaccination programs. However, deaths and complications continue to occur, attesting to the need to vaccinate all eligible infants and children against this virulent pathogen.     

Clinical and immunological effect of vaccination against Haemophilus influenzae, type B, in children with disorders of the nervous system

Observations on 277 children aged 3 months to 4 years with lesions of the nervous system, immunized with vaccine Act-HIB (Aventis Pasteur, France), were carried out in groups of children. The significant decrease of the level of Hib nasopharyngeal carrier state in 3.3 times and the decrease of total morbidity in acute infections of respiratory and ENT organs in 2.7 times occurred after immunization was revealed. The immunological effect of immunization on the level of protective titers against H. influenzae, type b, in children with organic CNS lesions in children was shown.     

Diagnostic value of different laboratory methods in the diagnosis of pneumonia caused by Haemophilus influenzae type B

Comparative analysis of the diagnostic value of different laboratory methods in the diagnosis of H. influenzae b (Hib) pneumonia in children (bacteriological method, latex agglutination, counter immunoelectrophoresis, the passive hemagglutination test and the enzyme immunoassay (EIA) was carried out. EIA proved to be the most informative method for the diagnosing Hib pneumonia. EIA makes it possible to detect specific Hib antigens in different clinical materials in 48.8% of cases, as well as high titers of antibodies to mis infective agent in 61.7% of cases. The authors propose the unified criteria of the laboratory diagnosis of Hib infection in children.     

Restricted Ig H chain V gene usage in the human antibody response to Haemophilus influenzae type b capsular polysaccharide

The mechanisms that govern the content of the human antibody repertoire are poorly understood. To investigate the antibody response to a clinically relevant Ag, we have produced heterohybridomas secreting human antibodies directed against the capsular polysaccharide of Haemophilus influenzae type b (Hib PS). Immune lymphocytes were harvested 7 days after immunization with either of two vaccine formulations, a plain polysaccharide vaccine (Hib PS) or a polysaccharide-protein conjugate of Hib PS and diphtheria toxoid (Hib PS-D). H chain V region gene nucleic acid sequences were determined for five stable hybridomas. All use members of the VHIII gene family and are 83% to 98% homologous to two candidate germ-line sequences. A variety of D and JH segments are used. Thus the Ig H chain repertoire appears to be restricted to a limited group of VHIII family members. The previously reported expression of homologous sequences in the human fetal repertoire suggests that the inability of young children to respond to this Ag is not caused by deficiencies of these important elements early in development. The restricted use of VHIII gene segments suggests that this gene family plays a pivotal role in the immune response to this important childhood pathogen.     

Multilocus sequence-typing for characterization of Moscow strains of Haemophilus influenzae type b

Haemophilius influenzae, type b (Hib) bacteria, were genotyped by multilocus sequence typing (MLST) using 5 loci (adk, fucK, mdh, pgi, recA). 42 Moscow Hib strains (including 38 isolates form cerebrospinal fluid of children, who had purulent meningitis in 1999-2001, and 4 strains isolated from healthy carriers of Hib), as well as 2 strains from Yekaterinburg were studied. In MLST a strain is characterized, by alleles and their combinations (an allele profile) referred to also as sequence-type (ST). 9 Sts were identified within the Russian Hib bacteria: ST-1 was found in 25 strains (57%), ST-12 was found in 8 strains (18%), ST-11 was found in 4 strains (9%) and ST-15 was found in 2 strains (4.5%); all other STs strains (13, 14, 16, 17, 51) were found in isolated cases (2.3%). A comparison of allelic profiles and of nucleotide sequences showed that 93% of Russian isolates, i.e. strain with ST-1, 11, 12, 13, 15 and 17, belong to one and the same clonal complex. 2 isolates from Norway and Sweden from among 7 foreign Hib strains studied up to now can be described as belonging to the same clonal complex; 5 Hib strains were different from the Russian ones.     

b型流感嗜血杆菌结合疫苗中载体蛋白质的效力研究

考察b型流感嗜血杆菌(Hib)结合疫苗的载体蛋白质—破伤风类毒素(TT)的免疫原性,为百白破与Hib四联疫苗中TT的使用提供参考。方法:将小鼠随机分为四组,分别注射Hib结合疫苗、Hib与百白混合疫苗、Hib与百白破混合疫苗、破伤风类毒素,比较它们在NIH小鼠体内所诱导产生的特异性抗体水平,并对这四组疫苗进行破伤风效力保护试验。结果表明,破伤风类毒素组,Hib与百白破混合疫苗组刺激的TT抗体水平远大于Hib结合疫苗组和Hib与百白混合疫苗组。效力试验虽四组间没有差异,只说明一定的抗体量就可以对小鼠提供保护。认为Hib结合疫苗中的载体蛋白并不能替代百白破疫苗中的破伤风类毒素。     

Surveillance of Haemophilus influenzae serotypes and antimicrobial resistance in Colombia, 1994-2002

Invasive disease caused by Haemophilus influenzae serotype b results in high rates of morbidity and mortality among children. In 1994, the Microbiology Group at the Instituto Nacional de Salud (Colombia) initiated a program to detect antimicrobial resistance in H. influenzae. Invasive isolates were collected by hospitals and public health laboratories as part of surveillance programs for acute respiratory infections and acute bacterial meningitis. To determine the evolution of serotypes and antimicrobial resistance patterns, invasive H. influenzae isolates collected from 1994 to 2002 were compared, and the impact of Hib conjugated vaccine in Colombia was reassessed. The analysis included 683 isolates, 379 (55.5%) were recovered from male patients, 370 (54.2%) from children under one year, 227 (33.2%) from children aged 1 to 5, 19 (2.8%) from children aged 6 to 14, and 38 (5.6%) from children over 14 years; 29 (4.2%) with no age data. Clinical classification recorded 493 (72.2%) of the samples were from patients with meningitis, 181 (26.5%) with pneumonia, and 9 (0.9%) with other diseases. Eighty five percent of isolates corresponded to H. influenzae serotype b, 12.9% were non capsular, and 2.0% corresponded to other serotypes (10 a, 1 d, 1 e and 2 f). Of the total number of isolates, 12.0% produced beta lactamase, 13.9% were resistant to ampicillin, 12.7% to trimethoprim sulfamethoxazole (SXT), 5.4% to chloramphenicol, 1% to cefuroxime. All isolates were susceptible to ceftriaxone. During the 10-year period, resistance to SXT increased from 5% to 13%. A significant decrease in meningitis cases was detected among children under one-year old and in the 1 to 5 age group. Before introducing the vaccine, an annual average of 43 and 23 isolates for each of these groups were received. During 2002, 10 and 6 isolates, respectively, were received for each group. Surveillance of invasive H. influenzae isolates has allowed the evaluation of Hib vaccine impact, as well as the detection of an increase of non-capsular isolates, and changes in resistance patterns.     

The other mediator for adherence of Haemophilus influenzae organisms without involvement of fimbriae.

The number of the nontypeable Haemophilus influenzae (HiN) organisms that adhered to the primary mouse fetal lung cells was significantly more than type b Haemophilus influenzae (Hib) organisms. The average number of HiN organisms adherent to host cells was 2,291/100 host cells (range, 1,654-3,182), but that of Hib was markedly reduced to 147/100 host cells (range, 102-238). In this case, P value was less than 0.05 by using a paired Student t-test. The sonicated extract from HiN TMS11 organisms inhibited adherence of H. influenzae TMS11 organisms to monolayer at 76.3% and it inhibited adherence of Hib TMS24 organisms at 92.3%. This result indicates that a mediator existing on the surface of HiN organisms may be the same as that on type b organisms. The number of detected organisms in broncho and lung tissues 3 days after intranasal infection with HiN strains was significantly greater than that in infection with Hib strains. Therefore, in vitro adhesive capacity of H. influenzae organisms was correlative to infectivity by intranasal injection.     

Diagnostic difficulties in identification of Haemophilus influenzae colonising the nasopharynx of children

The frequency of capsulated or non-capsulated Haemophilus influenzae strains colonisation among children attending day-care centres or orphanages has been studied. Detection of capsulated or non-capsulated H. influenzae strains has been compared for agglutination test and PCR. Misdiagnosing of H. influenzae serotype with agglutination found in the study suggest that the frequency of Hib strains colonizing the nasopharynx might be lower that previously evaluated. Due to perspectives of the wider use of Hib Immunisation in the future, more efficient diagnosis scheme for identification/differentiation of capsulated and non-capsulated H. influenzae strain should be undertaken.     

ELISA方法测定血清中Hib多糖抗体含量的条件比较研究

分别以牛血清白蛋白和人血清白蛋白作为封闭液的主要成分测定7份血清中抗b型流感嗜血杆菌荚膜多糖的抗体含量,结果显示,两组数据之间没有显著性差异(P>0.05)。分别用HRP标记的羊抗人IgG和HRP标记的鼠抗人IgG测定该7份血清,结果显示两组结果无显著性差异(P>0.05)。同时,将血清反应的温度和时间由37℃1.5h改为4℃16h(过夜),结果显示两者无显著性差异(P>0.05)。从而优化了该方法。     

Polyosides (encapsulated bacteria)

The polysaccharide capsule which surrounds bacterial species such as Haemophilus influenzae, Streptococcus pneumoniae, Neisseria meningitidis and Salmonella typhi is a potent virulence factor by protecting the bacteria from phagocytosis. The host responds with antibody production and specific antibodies plus complement binding to the capsule facilitate opsonization of the micro-organism, which is phagocytized and eliminated. Purified capsular polysaccharides elicit T-independent antibody responses without a memory function, but are often poorly immunogenic in infants where much of the invasive H. influenzae type b (Hib) and pneumococcal infections is seen. Therefore purified polysaccharides have found limited use as vaccines. However, covalent linkage of the capsular polysaccharide, or fractions thereof, to immunogenic carrier proteins creates glycoconjugates which are T-dependent antigens and which elicit antibodies also in infants and which prime for boosting either with the glycoconjugate or the capsular polysaccharide. In the last decade Hib glycoconjugate vaccines have been successfully introduced and in countries with very high immunization coverage the disease has been virtually eliminated and a decline of over 95% has been seen in countries with slightly lower vaccine rates. World-wide use of Hib glycoconjugate vaccines offers the possibility of elimination of invasive Hib disease. Pneumococcal (11 serotypes with coverage of approximately 85% of invasive disease), meningococcal (A, C, W 135, Y but not B) and S. typhi glycoconjugates are in advanced development and offer the prospect of being as successful as the Hib glycoconjugates.     

Functional activity of different IgG subclass antibodies against type b capsular polysaccharide of Haemophilus influenzae

The biologic activity of different human IgG subclass antibodies directed against the Haemophilus influenzae type b (Hib) capsular polysaccharide (PRP) was compared by using an in vitro complement-mediated bactericidal assay and an in vivo passive protection assay in infant rats. An IgG pool was made by Sephacryl S-300 chromatography of sera from adults immunized with PRP vaccine. An IgG2 subclass fraction was prepared by column immunoabsorption of the IgG pool with anti-IgG1 monoclonal antibody. An IgG1 subclass fraction was eluted from the affinity matrix. IgG1, IgG2, IgG3, and IgG4 concentrations in the fractions were measured by solid-phase competitive radioimmunoassays, and anti-PRP antibody was measured by a modified Farr assay. Each fraction was greater than 90% pure IgG2 or IgG1, respectively. There were no significant differences in the minimal anti-PRP antibody concentrations required to kill 50% of Hib cells in vitro (IgG, 0.22; IgG1, 0.21; and IgG2, 0.42 microgram/ml). Similarly, equivalent amounts of anti-PRP antibody of the IgG1 or IgG2 fractions protected against bacteremia (IgG1, 0.12; IgG2, 0.24 microgram per rat). IgG absorbed to remove anti-PRP antibody was neither bactericidal nor protective. Thus IgG1 and IgG2 anti-PRP antibody have equivalent functional activities against Hib as determined by these biologic assays.     

A hierarchical Bayesian model to predict the duration of immunity to Haemophilus influenzae type b

A hierarchical Bayesian regression model is fitted to longitudinal data on Haemophilus influenzae type b (Hib) serum antibodies. To estimate the decline rate of the antibody concentration, the model accommodates the possibility of unobserved subclinical infections with Hib bacteria that cause increasing concentrations during the study period. The computations rely on Markov chain Monte Carlo simulation of the joint posterior distribution of the model parameters. The model is used to predict the duration of immunity to subclinical Hib infection and to a serious invasive Hib disease.     

Quantitative nuclear magnetic resonance analysis and characterization of the derivatized Haemophilus influenzae type b polysaccharide intermediate for PedvaxHIB

PedvaxHIB is a pediatric vaccine that protects children from severe disease caused by the gram-negative bacterium Haemophilus influenzae type b (Hib). The vaccine is made by chemically conjugating Hib capsular polysaccharide to the outer membrane protein complex of Neisseria meningitidis. The protein-conjugated vaccine has proven to be extremely effective in preventing invasive Hib disease in infants and young children. This paper presents the nuclear magnetic resonance (NMR) methodology for the quantitative characterization of derivatized polysaccharide and its validation closely following ICH guidelines. The assay has been shown to be precise and accurate (relative standard deviation [RSD]相似文献   

Characterization of the IgD binding site of encapsulated Haemophilus influenzae serotype b

Encapsulated Haemophilus influenzae is a causative agent of invasive disease, such as meningitis and septicemia. Several interactions exist between H. influenzae and the human host. H. influenzae has been reported to bind IgD in a nonimmune manner, but the responsible protein has not yet been identified. To define the binding site on IgD for H. influenzae, full-length IgD and four chimeric IgDs with interspersed IgG sequences and Ag specificity for dansyl chloride were expressed in stably transfected Chinese hamster ovary cells. The binding of recombinant IgD to a panel of encapsulated H. influenzae serotype b (Hib) and nontypeable strains were investigated using a whole cell ELISA and flow cytometry. IgD binding was detected in 50% of the encapsulated Hib strains examined, whereas nontypeable H. influenzae did not interact with IgD. Finally, mapping experiments using the chimeric IgD/IgG indicated that IgD CH1 aa 198-224 were involved in the interaction between IgD and H. influenzae. Thus, by using recombinant IgD and chimeras with defined Ag specificity, we have confirmed that Hib specifically binds IgD, and that this binding involves the IgD CH1 region.