International Bordetella pertussis assay standardization and harmonization meeting report. Centers for Disease Control and Prevention, Atlanta, Georgia, United States, 19-20 July 2007

An international meeting on Bordetella pertussis assay standardization and harmonization was held at the Centers for Disease Control and Prevention (CDC), Atlanta, GA, 19–20 July 2007. The goal of the meeting was to harmonize the immunoassays used for pertussis diagnostics and vaccine evaluation, as agreed upon by academic and government researchers, regulatory authorities, vaccine manufacturers, and the World Health Organization (WHO).

The primary objectives were (1) to provide epidemiologic, laboratory, and statistical background for support of global harmonization; (2) to overview the current status of global epidemiology, pathogenesis and immunology of pertussis; (3) to develop a consensus opinion on existing gaps in understanding standardization of pertussis assays used for serodiagnosis and vaccine evaluation; and (4) to search for a multicenter process for addressing these priority gaps. Presentations and discussions by content experts addressed these objectives. A prioritized list of action items to improve standardization and harmonization of pertussis assays was identified during a group discussion at the end of the meeting. The major items included: (1) to identify a group that will organize, prepare, maintain, and distribute proficiency panels and key reagents such as reference and control sera; (2) to encourage the development and identification of one or more reference laboratories that can serve as an anchor and resource for other laboratories; (3) to define a performance-based assay method that can serve as a reference point for evaluating laboratory differences; (4) to develop guidance on quality of other reagents, e.g., pertussis toxin and other antigens, and methods to demonstrate their suitability; (5) to establish an international working group to harmonize the criteria to evaluate the results obtained on reference and proficiency panel sera; (6) to create an inventory to determine the amount of appropriate and well-characterized sera that are available globally to be used as bridging reagents for vaccine licensure; and (7) to seek specific guidance from regulatory authorities regarding the expectations and requirements for the licensure of new multicomponent pertussis vaccines.

Is Chlamydia pneumoniae found in spinal fluid samples from multiple sclerosis patients? Conflicting results

Cerebrospinal fluid samples from controls and patients with multiple sclerosis (MS) were split and sent to laboratories with different experiences for the detection of Chlamydia pneumoniae by polymerase chain reaction. Vanderbilt investigators identified C. pneumoniae in the majority of patients with MS and uncommonly in controls. Laboratories at Johns Hopkins University, University of Umeå, and the Centers for Disease Control and Prevention did not identify C. pneumoniae in any of the samples. Conflicting reports of C. pneumoniae detection in the some samples from patents with MS highlight the need to exchange detection techniques among laboratories involved in this controversy.

Standardizing Chlamydia pneumoniae assays: recommendations from the Centers for Disease Control and Prevention (USA) and the Laboratory Centre for Disease Control (Canada)

Chlamydia pneumoniae has been associated with atherosclerosis and several other chronic diseases, but reports from different laboratories are highly variable and "gold standards" are lacking, which has led to calls for more standardized approaches to diagnostic testing. Using leading researchers in the field, we reviewed the available approaches to serological testing, culture, DNA amplification, and tissue diagnostics to make specific recommendations. With regard to serological testing, only use of microimmunofluorescence is recommended, standardized definitions for "acute infection" and "past exposure" are proposed, and the use of single immunoglobulin (Ig) G titers for determining acute infection and IgA for determining chronic infection are discouraged. Confirmation of a positive culture result requires propagation of the isolate or confirmation by use of polymerase chain reaction (PCR). Four of 18 PCR assays described in published reports met the proposed validation criteria. More consistent use of control antibodies and tissues and improvement in skill at identifying staining artifacts are necessary to avoid false-positive results of immunohistochemical staining. These standards should be applied in future investigations and periodically modified as indicated.

Evaluation of pulsed-field gel electrophoresis in epidemiological investigations of meningococcal disease outbreaks caused by Neisseria meningitidis serogroup C

Since 1990, the frequency of Neisseria meningitidis serogroup C (NMSC) outbreaks in the United States has increased. Based on multilocus enzyme electrophoresis (MEE), the current molecular subtyping standard, most of the NMSC outbreaks have been caused by isolates of several closely related electrophoretic types (ETs) within the ET-37 complex. We chose 66 isolates from four well-described NMSC outbreaks that occurred in the United States from 1993 to 1995 to evaluate the potential of pulsed-field gel electrophoresis (PFGE) to identify outbreak-related isolates specific for each of the four outbreaks and to differentiate between them and 50 sporadic isolates collected during the outbreak investigations or through active laboratory-based surveillance from 1989 to 1996. We tested all isolates collected during the outbreak investigations by four other molecular subtyping methods: MEE, ribotyping (ClaI), random amplified polymorphic DNA assay (two primers), and serotyping and serosubtyping. Among the 116 isolates, we observed 11 clusters of 39 NheI PFGE patterns. Excellent correlation between the PFGE and the epidemiological data was observed, with an overall sensitivity of 85% and specificity of 71% at the 95% pattern relatedness breakpoint using either 1.5 or 1.0% tolerance. For all four analyzed outbreaks, PFGE would have given public health officials additional support in declaring an outbreak and making appropriate public health decisions.

Diversity and prevalence of PorA types in Neisseria meningitidis serogroup B in the United States, 1992-1998

Two hundred eighty-one sporadic Neisseria meningitidis serogroup B isolates, collected through active laboratory-based surveillance, were selected to be analyzed by PorA variable region (VR) typing to determine the prevalence of PorA types in the United States. A substantial number of distinct VR types were identified, 31 in VR1 and 41 in VR2. A total of 73 different PorA types were found, and 76. 7% of these types comprise nonprototype sequences in VR1, VR2, or both. The most prevalent PorA types were P1.7,16-20 (previously P1.7, 16i), P1.22,14, P1.22-1,14 (previously P1.22a,14), P1.7,16, P1.7-1,1 (previously P1.7d,1), P1.19,15, and P1.17,16-3 (previously P1.B,16d). No correlation was observed between the PorA types and geographic origin of the isolates. These data may aid in the design of an efficacious outer membrane protein-based vaccine by identifying the most appropriate PorA types for vaccine formulation. Studies are needed to fully evaluate the extent of cross-protection in humans among the variants and prototypes in each PorA VR family.

Distribution of Neisseria meningitidis serogroup B serosubtypes and serotypes circulating in the United States. The Active Bacterial Core Surveillance Team

Because the Neisseria meningitidis serogroup B (NMSB) capsule is poorly immunogenic in humans, immunization strategies have focused on noncapsular antigens. Both PorA and to a lesser extent PorB are noncapsular protein antigens capable of inducing protective bactericidal antibodies, and vaccines based on the outer membrane protein (OMP) components of serogroup B meningococci have been shown to be effective in clinical trials. Multiple PorA antigens seem to be needed to prevent endemic meningococcal disease around the world, and a hexavalent PorA-based meningococcal vaccine has recently been developed in The Netherlands. To evaluate the distribution of NMSB PorA and PorB antigens in the United States, serosubtyping and serotyping were done on 444 NMSB strains isolated in the active surveillance areas of the United States (total population, 32 million) during the period 1992 to 1998. A total of 244 strains were isolated from sporadic cases of meningococcal disease, and 200 strains were isolated from an epidemic in Oregon. A panel of 16 mouse monoclonal antibodies reactive with PorA and 15 monoclonal antibodies reactive with PorB were used. Among the NMSB isolates obtained from sporadic cases, the most prevalent serosubtypes were P1.7,16 (14.3%), P1.19,15 (9.8%), P1.7,1 (8.6%), P1.5,2 (7.8%), P1. 22a, 14 (7.8%), and P1.14 (5.3%) and the most prevalent serotypes were 4,7 (27.5%), 15 (16%), 14 (8.6%), 10 (6.1%), 1 (4.9%), and 2a (3.7%). A multivalent PorA-based OMP vaccine aimed at the six most prevalent serosubtypes could have targeted about half of the sporadic cases of NMSB disease that occurred between 1992 and 1998 in the surveillance areas. Twenty serosubtypes would have had to be included in a multivalent vaccine to achieve 80% coverage of strains causing sporadic disease. The relatively large number of isolates that did not react with murine monoclonal antibodies indicates that DNA sequence-based variable region typing of NMSB will be necessary to provide precise information on the distribution and diversity of PorA antigens and correlation with nonserosubtypeable isolates. The high degree of variability observed in the PorA and PorB proteins of NMSB in the United States suggests that vaccine strategies not based on OMPs should be further investigated.

Cleavase fragment length polymorphism analysis of Neisseria meningitidis basic metabolic genes

Cleavase fragment length polymorphism (CFLP) is a subtyping system based on the property of the enzyme cleavase to recognize junctions between single- and double-stranded regions of DNA formed after denaturation and cooling. To assess the capacity of CFLP for discriminating Neisseria meningitidis serogroup B strains belonging to the electrophoretic type (ET) 5 (ET-5) complex from other serogroup B strains, 30 serogroup B N. meningitidis isolates were subtyped by CFLP with internal fragments of five housekeeping genes, adk, aspC, carA, dhp, and glnA. Two genes (glnA and carA) which demonstrated a high degree of diversity for the serogroup B isolates were then used to further evaluate the suitability of CFLP for screening 50 serogroup C N. meningitidis outbreak-associated and sporadic-case isolates with a single metabolic gene. The results were compared to those from multilocus enzyme electrophoresis (MEE), the current standard subtyping method. CFLP was able to distinguish the ET-5 complex isolates from other serogroup B isolates as efficiently as MEE. Furthermore, CFLP analysis of a single gene was sufficient to identify and cluster the serogroup C isolates belonging to the ET-37 complex from other, unrelated serogroup C isolates but was not capable of differentiating between the isolates of the major individual ETs of this complex (ET-17 and ET-24) causing most serogroup C meningococcal disease outbreaks in the United States. CFLP based on a single gene with a high degree of diversity but not under selective pressure can be applied to the rapid screening of a large number of isolates related to the recognized epidemic complex ET-5 or ET-37. Additionally, CFLP can be used as an initial screening tool to survey the amount of diversity in genes that might be used to develop a DNA sequence-based subtyping system.

Suspected Brazilian purpuric fever in a toddler with overwhelming Epstein-Barr virus infection

We describe a toddler from Connecticut who developed purulent conjunctivitis, fever, and a morbilliform rash. Blood cultures were positive for Haemophilus influenzae biogroup aegyptius; further investigation was performed to assess the possibility that the illness was consistent with Brazilian purpuric fever, which, to our knowledge, has not been reported in the United States. This isolate shared morphological and some biochemical characteristics with previously studied H. influenzae biogroup aegyptius strains but differed according to slide agglutination testing, plasmid characterization, and ribotyping. Blood and tissue samples obtained during his hospitalization were also positive for Epstein-Barr virus. The child died 8 days after hospitalization. Fifty other cases of invasive H. influenzae infection were identified by active surveillance studies. Of the 49 viable surveillance isolates, 10 were biotype III (two of which had the same ribotype as the strain from our case.

Genetic structure of Neisseria meningitidis serogroup C epidemic strains in south Brazil

In the present study we report the results of an analysis, based on serotyping, multilocus enzyme electrophoresis (MEE), and ribotyping of N. meningitidis serogroup C strains isolated from patients with meningococcal disease (MD) in Rio Grande do Sul (RS) and Santa Catarina (SC) States, Brazil, as the Center of Epidemiology Control of Ministry of Health detected an increasing of MD cases due to this serogroup in the last two years (1992-1993). We have demonstrated that the MD due to N.meningitidis serogroup C strains in RS and SC States occurring in the last 4 years were caused mainly by one clone of strains (ET 40), with isolates indistinguishable by serogroup, serotype, subtype and even by ribotyping. One small number of cases that were not due to an ET 40 strains, represent closely related clones that probably are new lineages generated from the ET 40 clone referred as ET 11A complex. We have also analyzed N.meningitidis serogroup C strains isolated in the greater São Paulo in 1976 as representative of the first post epidemic year in that region. The ribotyping method, as well as MEE, could provide useful information about the clonal characteristics of those isolates and also of strains isolated in south Brazil. The strains from 1976 have more similarity with the actual endemic than epidemic strains, by the ribotyping, sulfonamide sensitivity, and MEE results. In conclusion, serotyping with monoclonal antibodies (C:2b:P1.3), MEE (ET 11 and ET 11A complex), and ribotyping by using ClaI restriction enzyme (Rb2), were useful to characterize these epidemic strains of N.meningitidis related to the increased incidence of MD in different States of south Brazil. It is mostly probable that these N.meningitidis serogroup C strains have poor or no genetic correlation with 1971-1975 epidemic serogroup C strains. The genetic similarity of members of the ET 11 and ET 11A complex were confirmed by the ribotyping method by using three restriction endonucleases.

Brazilian purpuric fever caused by Haemophilus influenzae biogroup aegyptius strains lacking the 3031 plasmid

Brazilian purpuric fever (BPF) is a life-threatening pediatric infection caused by Haemophilus influenzae biogroup aegyptius (Hae), an organism formerly associated with only self-limited purulent conjunctivitis. Strains of Hae causing BPF have a 24-MDa plasmid with a specific AccI restriction pattern designated 3031. This plasmid was thought to code for a virulence factor because it had been detected only among Hae strains isolated from BPF cases or their contacts. From 3 typical BPF cases recently identified in São Paulo State, sterile-site Hae isolates were obtained; these isolates were similar to earlier BPF-associated Hae except they did not possess a 3031 plasmid. HindIII restricted chromosomal DNA from these strains was probed with purified 3031 plasmid DNA under high-stringency conditions. There was no evidence that 3031 plasmid DNA had become chromosomally integrated. It appears that the 3031 plasmid does not code for BPF-specific virulence factors.

Ribotyping as an additional molecular marker for studying Neisseria meningitidis serogroup B epidemic strains

The molecular method of ribotyping was used as an additional epidemiological marker to study the epidemic strains of Neisseria meningitidis serogroup B, referred to as the ET-5 complex, responsible for the epidemic which occurred in greater São Paulo, Brazil. Ribotyping analysis of these strains showed only a single rRNA gene restriction pattern (Rb1), obtained with ClaI restriction enzyme. This method, as well as multilocus enzyme electrophoresis, provided useful information about the clonal characteristics of the N. meningitidis serogroup B strains isolated during this epidemic. The N. meningitidis serogroup B isolates obtained from epidemics which occurred in Norway, Chile, and Cuba also demonstrated the same pattern (Rb1). Ribotyping was a procedure which could be applied to a large number of isolates and was felt to be appropriate for routine use in laboratories, especially because of the convenience of using nonradioactive probes.

Characterization of epidemic Neisseria meningitidis serogroup C strains in several Brazilian states

Epidemic strains of the Neisseria meningitidis C:2b:P1.3 electrophoretic type 11 complex were responsible for an outbreak in Curitiba, Parana State, Brazil, from 1990 to 1991. Strains of this complex were also isolated in other Brazilian states and were responsible for a meningococcal disease epidemic in São Paulo State in 1990. Serotyping both with monoclonal antibodies and by multilocus enzyme electrophoresis was useful for typing these epidemic strains related to the increased incidence of meningococcal disease. The genetic similarity of members of the electrophoretic type 11 complex was confirmed by the ribotyping method by using EcoRI or ClaI endonuclease restriction enzymes.

[Isolation of Haemophilus aegyptius associated with Brazilian purpuric fever, of Chloropidae (Diptera) of the genera Hippelates and Liohippelates]

The recognition of the Brazilian purpuric fever (BPF) in 1984 led to a number of studies which showed a relation between this disease and conjunctivitis caused by Haemophilus aegyptius. The increase in cases of conjunctivitis in children associated with higher population density of eye gnats (Chloropidae: Hippelates) has been reported since last century. This phenomenon is related to the attraction that those flies show for the eyes, secretions and wounds, from where they feed on. Although there are evidences on the role of these flies in the mechanical transmission of seasonal bacterial conjunctivitis, the isolation of Haemophilus aegyptius from them in their natural habitat had not been demonstrated yet. In this study Haemophilus aegyptius associated to BPF was isolated from two pools of chloropids collected around the eyes of children with conjunctivitis which were identified as Liohippelates peruanus (Becker) and a new species Hippelates neoproboscideus.

[Brazilian purpuric fever, virulence in an animal model of Haemophilus aegyptius (H. influenzae biogroup aegyptius). Grupo de Estudo da Febre Purpúrica Brasileira]

Brazilian purpuric fever (BPF) is caused by invasive strains of Haemophilus aegyptius (H. influenzae biogroup aegyptius, Hae). These strains were differentiated from Hae strains associated only with conjunctivitis (non-invasive Hae strains) through specific molecular markers. Complement-depleted infant rat model was used to study the invasive and non-invasive Hae strains to compare their virulence potential. Inoculating 10(5) bacteria in the rats, the invasive strains caused 80 to 100% bacteremia and the intensity of bacteremia was 10(2.5 +/- 0.49) to > 10(4.69) cfu/ml of blood. Using the same infectious dose, the non-invasive strains did not cause frequent bacteremia (0 to 50%) and the intensity was 0 to 10(3.69 +/- 0.53) cfu/ml of blood. The infectious doses able to cause 50% of bacteremia in the rats (BD 50%) varied from < 10(3) to 10(4.2) bacteria for the invasive strains, whereas the BD 50% were 10(6.2) to > 10(7.3) bacteria for non-invasive strains. Passive immunization using antisera to invasive strains protected rats against bacteremia caused by homologous strains, but not by heterologous strain. By comparing the bacteremia caused by Hae and bacteremia caused by H. influenzae b (Eagan strain, Hib), it was demonstrated that Hib had higher virulence potential. This animal model was useful to clarify the virulence potential of invasive Hae strains.

Comparative efficacy of oral rifampin and topical chloramphenicol in eradicating conjunctival carriage of Haemophilus influenzae biogroup aegyptius. Brazilian Purpuric Fever Study Group

Persistent conjunctival carriage of the Haemophilus influenzae biogroup aegyptius (Hae) strain (BPF clone) responsible for Brazilian purpuric fever (BPF) has been documented. Topical chloramphenicol is routinely used to treat conjunctivitis in areas affected by BPF in Brazil. Although the BPF clone is susceptible to chloramphenicol, we observed a number of children treated with topical chloramphenicol for conjunctivitis who still developed BPF. During an investigation of an outbreak of BPF in Mato Grosso State, Brazil, we compared oral rifampin (20 mg/kg/day for 4 days) with topical chloramphenicol for eradication of conjunctival carriage of H. influenzae biogroup aegyptius among children with presumed BPF clone conjunctivitis. Conjunctival samples were taken for culture on the day treatment was initiated and a mean of 8 and 21 days later. At 8 days the eradication rates for oral rifampin and topical chloramphenicol were 100 and 44%, respectively (P = 0.003); at 21 days they were 100 and 50% (P = 0.01). Oral rifampin was more effective than topical chloramphenicol for eradication of the BPF clone and may be useful in prevention of BPF.

[Brazilian purpuric fever. Fast characterization of invasive strains of Haemophilus aegyptius]

Strains of H. aegyptius isolated during outbreak of Brazilian Purpuric Fever (BPF) in Brazil were characterized antigenically by slide agglutination test utilizing antiserum produced with a H. aegyptius strain isolated from blood culture from a patient with BPF. By means of this method, it were identified H. aegyptius strains responsible for outbreaks of conjunctivitis with identical antigenic characteristics to strains isolated from BPF. The sensitivity and specificity of slide seroagglutination test was 97.7% and 89.6% respectively; therefore this assay was efficient to be used as a screening method in the studies of purulent conjunctivitis for detecting high risk populations for BPF, and to implement measures that will increase the efficiency of epidemiologic surveillance.

Nucleotide sequence and structure of the mouse cytokeratin endoB gene

We report the isolation and nucleotide sequence (7878 bp) of a genomic clone encoding murine cytokeratin EndoB, a type-I intermediate filament protein that is expressed coordinately with EndoA in trophectoderm cells during blastocyst formation. This clone contains the complete endoB gene including the 5' upstream and 3' downstream flanking regions. Sequencing analysis reveals the endoB gene consists of seven exons and six introns. Although the positions of the six introns coincide exactly with those of other type-I cytokeratin genes, the endoB gene has lost the seventh intron, which resides in the sequences coding for tail domains of other type-I cytokeratins. The 5' upstream regions of endoA and endoB genes contain homologous sequences around the respective TATA-like boxes, suggesting their involvement in coordinate regulation of their transcription and/or post-transcription. Surprisingly, this clone contains at least four murine B1 repetitive sequences. One typical B1 repetitive sequence was recognized in the 5' upstream region, and the other three in the 3' flanking region.

Nucleotide sequence of mouse EndoA cytokeratin cDNA reveals polypeptide characteristics of the type-II keratin subfamily

EndoA cytokeratin (EndoA) belongs to a family of intermediate filaments (IFs) and is coordinately expressed with EndoB cytokeratin during early mouse embryogenesis. We have isolated and sequenced a cDNA from a library constructed from mRNA of parietal yolk sac-like cells, PYS-2, which are derived from mouse teratocarcinoma. Sequence analysis reveals that EndoA is composed of 490 amino acids, its Mr is 54,362, and it contains a central alpha-helical coiled-coil structure flanked by non-alpha-helical domains. The amino acid sequence of EndoA is highly homologous with human cytokeratin No. 8 (93%) and with bovine cytokeratin No. 8 (91%) not only in the central domain, but also in its tail portion, which is less conserved among other intermediate filaments. A comparison with the other cytokeratin proteins characterizes this polypeptide as a non-epidermal type of cytokeratin of the basic (type-II) subfamily. The C-terminal sequence of EndoA is identical to that of human and bovine cytokeratin No. 8 and also highly conserved in other intermediate filaments (desmin, vimentin, glial fibrillary acidic protein and EndoB). It suggests that these may be involved in interaction with some cell component(s), or in more general roles to form IFs. The N-terminal head region is rich in Ser residues including possible phosphorylation sites.