Serologic diagnosis of whooping cough by an enzyme-linked immunosorbent assay using fimbrial hemagglutinin as antigen

Salmonella enterica serovar Typhi exposure elicits ex vivo cell-type-specific epigenetic changes in human gut cells

Salmonella enterica serovar Typhi (S. Typhi) causes substantial morbidity and mortality worldwide, particularly among young children. Humans develop an array of mucosal immune responses following S. Typhi infection. Whereas the cellular mechanisms involved in S. Typhi infection have been intensively studied, very little is known about the early chromatin modifications occurring in the human gut microenvironment that influence downstream immune responses. To address this gap in knowledge, cells isolated from human terminal ileum exposed ex vivo to the wild-type S. Typhi strain were stained with a 33-metal-labeled antibody panel for mass cytometry analyses of the early chromatin modifications modulated by S. Typhi. We measured the cellular levels of 6 classes of histone modifications, and 1 histone variant in 11 major cell subsets (i.e., B, CD3 + T, CD4 + T, CD8 + T, NK, TCR-γδ, Mucosal associated invariant (MAIT), and NKT cells as well as monocytes, macrophages, and epithelial cells). We found that arginine methylation might regulate the early-differentiation of effector-memory CD4+ T-cells following exposure to S. Typhi. We also found S. Typhi-induced post-translational modifications in histone methylation and acetylation associated with epithelial cells, NKT, MAIT, TCR-γδ, Monocytes, and CD8 + T-cells that are related to both gene activation and silencing.

Laboratory Diagnosis of Pertussis

The introduction of vaccination in the 1950s significantly reduced the morbidity and mortality of pertussis. However, since the 1990s, a resurgence of pertussis has been observed in vaccinated populations, and a number of causes have been proposed for this phenomenon, including improved diagnostics, increased awareness, waning immunity, and pathogen adaptation. The resurgence of pertussis highlights the importance of standardized, sensitive, and specific laboratory diagnoses, the lack of which is responsible for the large differences in pertussis notifications between countries. Accurate laboratory diagnosis is also important for distinguishing between the several etiologic agents of pertussis-like diseases, which involve both viruses and bacteria. If pertussis is diagnosed in a timely manner, antibiotic treatment of the patient can mitigate the symptoms and prevent transmission. During an outbreak, timely diagnosis of pertussis allows prophylactic treatment of infants too young to be (fully) vaccinated, for whom pertussis is a severe, sometimes fatal disease. Finally, reliable diagnosis of pertussis is required to reveal trends in the (age-specific) disease incidence, which may point to changes in vaccine efficacy, waning immunity, and the emergence of vaccine-adapted strains. Here we review current approaches to the diagnosis of pertussis and discuss their limitations and strengths. In particular, we emphasize that the optimal diagnostic procedure depends on the stage of the disease, the age of the patient, and the vaccination status of the patient.

Diagnosis of pertussis: a historical review and recent developments

The accurate and timely diagnosis of pertussis continues to be challenging. The widespread use of pertussis vaccines has dramatically altered the epidemiology and clinical presentation of pertussis disease, such that many cases do not present with the hallmark symptoms, such as inspiratory whoop, post-tussive vomiting and paroxysmal cough. A variety of laboratory tools are available to aid in the diagnosis of pertussis, including culture, direct fluorescent antibody testing, PCR, and paired and single serology techniques. This article reviews the strengths and limitations, including the sensitivity and specificity, of each of these diagnostic tools.

Immunogenicity and safety of human papillomavirus-16/18 AS04-adjuvanted vaccine coadministered with tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis vaccine and/or meningococcal conjugate vaccine to healthy girls 11 to 18 years of age: results from a randomized open trial

BACKGROUND

A combined immunization strategy for administration of human papillomavirus (HPV) vaccine with other routine vaccines may lead to better compliance. Reactions and immunologic interference with concomitantly administered vaccines are unpredictable, necessitating clinical evaluation.

METHODS

This was a randomized, open study conducted at 48 centers in the United States (NCT00369824). Healthy girls 11 to 18 years of age were randomized equally to 1 of 6 groups to receive 3 doses of HPV-16/18 AS04-adjuvanted vaccine administered at 0, 1, and 6 or 1, 2, and 7 months, with or without 1 dose of tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis vaccine (Tdap) and/or 1 dose of meningococcal polysaccharide diphtheria toxoid conjugate vaccine (MCV4) in different coadministration regimens (1283 girls vaccinated). Coadministered vaccines were injected at separate sites. Antibodies were measured for all vaccine components. Reactogenicity and safety were monitored.

RESULTS

The prespecified criteria for noninferiority were met for all primary and secondary immunogenicity end points, demonstrating similar immunogenicity of Tdap and MCV4 when given alone or coadministered with the HPV vaccine. Immunogenicity of the HPV vaccine (in terms of seroconversion rates and geometric mean antibody titers to HPV antigens) was similar, regardless of whether it was given alone or coadministered with Tdap and/or MCV4. No differences were observed in the reactogenicity profile of the HPV vaccine administered alone or coadministered with either Tdap and/or MCV4 in different regimens.

CONCLUSIONS

Concomitant administration of HPV-16/18 AS04-adjuvanted vaccine with Tdap and/or MCV4 in different regimens did not interfere with the immune response to any of the vaccines and had an acceptable safety profile.

The diagnosis of pertussis: which method to choose?

Despite the introduction of routine vaccination against pertussis for more than a half century, leading to a drastic decline in the number of reported cases, pertussis continues to be an important respiratory disease afflicting unvaccinated infants and previously vaccinated children as well as adults in whom immunity has waned. The diagnosis of pertussis is challenging and accurate laboratory identification of Bordetella infections remains problematic. Common laboratory diagnostic methods used for pertussis diagnosis include culture, direct-fluorescent-antibody testing (DFA), serology and polymerase chain reaction (PCR). Culture of Bordetella pertussis is highly specific but fastidious and has limited sensitivity. DFA provides a much more rapid result, but has the disadvantage of poor sensitivity and specificity. Serology is not useful in infants. In older persons, it is hampered by the limitations of paired sera and it provides mainly a retrospective diagnosis. Such limitations of conventional diagnosis testing have led to the development of PCR assays. Notwithstanding its lack of standardization, PCR has been found to be more sensitive and more specific than other methods. In this report, we aimed to review current knowledge about the available diagnostic methods and tests that accurately diagnose pertussis.

Molecular pathogenesis, epidemiology, and clinical manifestations of respiratory infections due to Bordetella pertussis and other Bordetella subspecies

Bordetella respiratory infections are common in people (B. pertussis) and in animals (B. bronchiseptica). During the last two decades, much has been learned about the virulence determinants, pathogenesis, and immunity of Bordetella. Clinically, the full spectrum of disease due to B. pertussis infection is now understood, and infections in adolescents and adults are recognized as the reservoir for cyclic outbreaks of disease. DTaP vaccines, which are less reactogenic than DTP vaccines, are now in general use in many developed countries, and it is expected that the expansion of their use to adolescents and adults will have a significant impact on reducing pertussis and perhaps decrease the circulation of B. pertussis. Future studies should seek to determine the cause of the unique cough which is associated with Bordetella respiratory infections. It is also hoped that data gathered from molecular Bordetella research will lead to a new generation of DTaP vaccines which provide greater efficacy than is provided by today's vaccines.

Evaluation of PCR for diagnosis of Bordetella pertussis and Bordetella parapertussis infections

PCR, using primers Plp1 and Plp2, was evaluated for the detection of DNA from Bordetella pertussis in bacterial strains and in nasopharyngeal samples from patients with a cough lasting at least 7 days. The assay could detect DNA from 6 CFU of B. pertussis/10 microl of sample. Results of the PCR assay were compared with those of cultures, a determination of serum antibodies against pertussis toxin and filamentous hemagglutinin, and a clinical evaluation of 2,442 coughing episodes. The overall sensitivity of PCR was 65% (623 of 956), which was higher than the sensitivity of cultures (58%) (P < 0.001). Factors influencing the sensitivity of PCR were the interval between the onset of symptoms and sampling and the vaccination status of the patient. The specificity of PCR was 98% (1,451 of 1,486). The positive and negative predictive values were 95 and 81%, respectively. Parapertussis PCR, using primers BPPA and BPPZ, was positive in 11 of 18 culture-positive cases and was confirmed by serology in another 4 cases. In conclusion, PCR is a valuable complement to cultures and can probably replace cultures for diagnosis of B. pertussis and Bordetella parapertussis infections.

Response and decline of serum IgG antibodies to pertussis toxin, filamentous hemagglutinin and pertactin in children with pertussis

The serum IgG antibody response and decrease to 3 Bordetella pertussis antigens was compared in children with pertussis. Sera were obtained at the first clinical visit and 1, 3 and 12 months later from 89 children with > or = 3 weeks of paroxysmal cough. IgG antibodies to pertussis toxin (PT), to filamentous hemagglutinin (FHA) and to pertactin were determined with ELISA. Of 54 children with culture-confirmed pertussis or culture-confirmed familial exposure, 45 (83%) had a significant (> or = 3 fold) increase in PT IgG and 40 (74%) in FHA IgG antibodies, while only 29 (54%) had a significant increase in pertactin IgG antibodies. Significant decreases in PT, FHA and pertactin IgG antibodies were found in 34 (63%), 9 (17%) and 28 (52%) children, respectively. In the remaining 35 who did not have culture-confirmed disease, significant PT and/or FHA IgG antibody increases (criteria for pertussis according to the WHO definition) were found in 17 (49%). Only 6 of these 17 children had a significant pertactin IgG antibody increase. Of the remaining 18 children (who did not fulfil WHO criteria for pertussis), significant decreases in PT and/or FHA IgG antibodies were found in 13. We conclude that a serum IgG reaction to PT and FHA occurs in almost all children with pertussis. An increase in pertactin IgG antibodies occurs less frequently than against PT and FHA. Significant decreases in PT or FHA IgG antibodies in children with clinical pertussis might be of use as a diagnostic criterion in children brought late for examination.

Bordetella pertussis adenylate cyclase activity in nasopharyngeal aspirates for rapid diagnosis of whooping cough in relation to culture and serology

Adenylate cyclase activity, measured in 201 nasopharyngeal aspirates from patients presenting with own or parental suspicion of whooping cough, was compared to diagnosis made by culture and by serology in the culture negative cases. The median amount of cyclic AMP in samples from culture negative patients (n = 145) was 0.60 pmoles which differed significantly (p less than 0.001) from the median value 3.28 in samples from culture positive patients (n = 56). The median value 0.70 pmoles of cyclic AMP in samples from culture negative patients who were positive by serology (n = 54) did not differ significantly from the value of 0.57 pmoles in samples from serology negative patients (n = 91). With a limit for positive cyclic AMP set at 2 pmoles, 45 samples were positive. The sensitivity of the assay was 66% (37/56) in culture positive patients while the specificity was 93% (85/91) in the serology negative patients. The positive predictive value for the c-AMP test was 82% (37/45) in relation to culture and 87% (39/45) in relation to culture and/or serology. The results confirmed that measurement of adenylate cyclase activity in nasopharyngeal aspirates by an 1-h incubation method can serve as an early and rapid diagnostic method of pertussis infection. The low sensitivity of the c-AMP assay in samples from serology positive but culture negative patients indicates however, that this assay will have to be supplemented by serology for a high diagnostic sensitivity in all cases of pertussis.

Diagnostic value of clinical and bacteriological findings in pertussis

Clinical and bacteriological findings in the diagnosis of pertussis were evaluated in 300 consecutive patients with parental or the patient's own suspicion of the disease. Serology was used as a reference method. Of the 285 (95%) patients fully sampled, 163 (57%) were diagnosed as having pertussis while the remaining 122 patients constituted the non-pertussis control group. The clinical and epidemiological data were collected at the first visit made on median day seven of illness. In this population of mainly unimmunised children, the highest predictive values were obtained for the physician's diagnosis of pertussis (100%) and for the physician's diagnosis of some other illness (93%). The only clinical symptom with a high predictive value for pertussis was the report of whoops (92%). Among epidemiological data the highest predictive value (90%) was obtained for reported household exposure in unimmunised children more than 1 year of age. Culture of Bordetella pertussis was found to have an overall 50% sensitivity. Isolation of other bacteria had no predictive value in the differential diagnosis of pertussis.

Immunoglobulin A antibodies to pertussis toxin and filamentous hemagglutinin in saliva from patients with pertussis

Immunoglobulin A (IgA) antibodies against pertussis toxin (PT) and filamentous hemagglutinin (FHA) in 181 saliva samples obtained during various stages of pertussis from 112 patients were determined. Saliva samples obtained within 5 days after the onset of symptoms did not have detectable IgA antibodies against either of the two antigens. Of the samples obtained between 6 and 50 days after the onset of symptoms, 72% had antibodies against FHA but only 40% had antibodies against PT. With few exceptions, saliva samples obtained more than 50 days after the onset of symptoms contained antibodies against both antigens. In the 59 patients from whom paired saliva samples were obtained at intervals of 2 to 5 weeks, a significant increase in the geometric mean FHA antibody titers but not PT antibody titers occurred. However, increases that were fourfold or greater were observed against FHA in only 19 patients and against PT in 14 patients. Thus, IgA antibodies against FHA and PT in saliva develop during pertussis, and the importance of secretory IgA antibodies for protection against infection and disease should be investigated. Determination of these antibodies in paired saliva samples is, however, of little value for the laboratory diagnosis of pertussis.

Use of a Chinese hamster ovary cell cytotoxicity assay for the rapid diagnosis of pertussis

A cytotoxicity assay with Chinese hamster ovary cells (CHO) capable of detecting 750 pg of pertussis toxin was assessed for use as a rapid test for the diagnosis of pertussis and compared with direct immunofluorescence (DFA). With pure bacterial cultures and simulated clinical specimens, the CHO assay detected as few as two colonies of Bordetella pertussis; no cytotoxicity occurred with other respiratory tract microorganisms. Next, nasopharyngeal aspirate secretions and nasopharyngeal cultures harvested after 72 h of incubation from 57 culture-positive and 201 culture-negative patients were examined. The CHO assay with nasopharyngeal secretions was positive in 25 (45%) of 55 culture-positive cases; DFA was positive in 15 (26%) of 57 cases (P = 0.05). The CHO assay with 72-h culture washes was positive in 42 (75%) of 57 culture-positive cases (P less than 0.001 compared with DFA). The CHO assay was more specific than DFA; all five CHO-positive, culture-negative cases were confirmed as true positives by serologic or toxin neutralization assays. In contrast, only 4 (36%) of 11 DFA-positive, culture-negative cases were confirmed as pertussis by serologic methods (P = 0.03). Combining the CHO assay with culture significantly decreased the delay in laboratory diagnosis of pertussis (3.30 versus 4.54 days; P = 0.01). The CHO assay is a sensitive and specific assay for the rapid diagnosis of pertussis.

Serum antibody response to B. pertussis Tn5 mutants, purified PT and FHA in two different mouse strains and passive protection in the murine intranasal infection model

The protective capacities of antibodies to pertussis toxin (PT) were compared with antibodies to several other pertussis antigens in an experimental murine model of intranasal infection with Bordetella pertussis. Protection from lethal challenge was achieved by passive immunization with mouse antisera to whole cells of the virulent B. pertussis BP338(Vir+) and its Tn5-generated mutants, BP353(Fha-), BP348(Adc-Hly-) and to a lesser extent of BP347(Vir-). The immune sera were produced in two different mouse strains, a good PT antibody responder (NIH) and a poor responder (F1 of CBA x C57BL/6). The antisera produced in the F1 mice contained no detectable neutralizing antibodies to PT as measured by the CHO cell assay. In spite of this the anti-BP353(Fha-) and BP348(Adc-Hly-) sera of the F1 mice seemed as protective as those of the NIH mice. A strong dependence between PT neutralizing antibody and protection was seen only when comparing sera of NIH and F1 mice immunized with purified active PT. The protective capacity of sera of both mouse strains immunized with purified filamentous hemagglutinin (FHA) correlated with their anti-FHA titers measured by enzyme immunoassay. The data thus confirm the protective capacity of anti-PT and anti-FHA, but also show that antibodies of other specificities can confer protection.

Preparation of filamentous hemagglutinin from Bordetella pertussis and assay for serum antibodies to filamentous hemagglutinin and pertussis toxin for clinical and public health laboratories

A procedure that is sufficiently simple and economical for use in clinical and public health laboratories for producing and purifying filamentous hemagglutinin (FHA) and determining antibodies to this major antigen of Bordetella pertussis in serum is described. High yields of FHA (40 to 80 mg/liter) were obtained in the supernatant by cultivating B. pertussis in modified CL medium. The FHA antigen was separated from pertussis toxin (PT) and other antigens by chromatography on hydroxylapatite. Removal of residual PT activity in the FHA fraction was effected by affinity absorption of PT with Fetuin immobilized to Sepharose 4B. The FHA was used as the antigen for determining titers of immunoglobulin G (IgG), IgA, and IgM to FHA in sera of patients with pertussis by an improved enzyme-linked immunosorbent assay. Development of the interfering background color commonly observed in conventional FHA enzyme-linked immunosorbent assay procedures was eliminated by washing the reaction wells with a buffer of high ionic strength before adding the peroxidase conjugates. In the absence of nonspecific background color, the reaction endpoints were easy to read. The FHA prepared by the procedure described was identical to a reference preparation of purified FHA in sodium dodecyl sulfate-polyacrylamide gel electrophoresis profiles and serological specificity assays. High yields of FHA were obtained from all four strains of B. pertussis tested in this study, indicating that the procedure for enhanced production of FHA may be generally applicable to other strains of B. pertussis. Results from tests of 50 serum specimens with clinical information on pertussis for FHA and PT antibodies by the assay procedures described exemplified the usefulness and caveats of serodiagnosis for pertussis.

Adverse reactions and antibody response to an acellular pertussis toxoid vaccine in adult volunteers

A monovalent pertussis toxoid vaccine (JNIH-7, Biken, Japan) was evaluated for reactogenicity and immunogenicity in 20 healthy adults (phase 1 study). Fever of greater than or equal to 38 degrees C was recorded in 2/20; local reactions started in 2/20 on day 1 (early onset) and in 3/20 on day 7 (late onset). All 15/15 subjects tested showed a significant antibody response to pertussis toxin by neutralization or enzyme-linked immunosorbent assay. Significantly elevated antibodies were still detected in 12/13 subjects 32 months after the single subcutaneous dose of vaccine.

Outbreak of pertussis in a residential facility for handicapped people

An outbreak of pertussis was recognized and investigated in a home for neurologically impaired people. Of 66 residents, 44 (67%) had evidence of recent pertussis infection, although only 12 (27%) had respiratory symptoms. Pertussis was diagnosed by culture, direct fluorescent antibody testing of nasal secretions, agglutinating antibody titer, pertussis antitoxin titer, IgG antibody to pertussis toxin, IgA antibody to pertussis toxin, IgA antibody to filamentous hemagglutinin, or IgG antibody to filamentous hemagglutinin. No single test identified more than 66% of people with pertussis. Of those with positive serologic findings, 95% had a positive test result for IgA antibody to filamentous hemagglutinin or for IgG antibody to pertussis toxin or for both. Pertussis occurred in both immunized and unimmunized residents. Seven carriers were identified; these residents had positive cultures or positive direct fluorescent antigen test results but negative serologic findings. Treatment of residents and caretakers with erythromycin halted the outbreak.

Evaluation of culture, immunofluorescence, and serology for the diagnosis of pertussis

Nasopharyngeal culture, direct immunofluorescence, and serology of acute-phase and paired serum specimens were compared for the laboratory diagnosis of infections due to Bordetella pertussis in a community-based pediatric population with both high vaccine usage and high pertussis incidence. In 77 (37%) of 210 patients evaluated, one or more tests were positive for pertussis. A clinical illness compatible with pertussis was present in 52 (71%) of 73 pertussis test-positive and 42 (35%) of 119 test-negative patients (P less than 0.001). Nasopharyngeal culture was of low sensitivity (20 [26%] of 77 positive tests) but was most commonly confirmed by another positive pertussis test (85%). Direct immunofluorescence was both insensitive and nonspecific; only 6 (30%) of 20 cases positive by culture were positive by immunofluorescence, and only 4 (33%) of 12 of the culture-negative, immunofluorescence-positive cases could be confirmed by another positive pertussis test. Although serology by enzyme immunoassay proved to be the most sensitive of the laboratory tests (87%), this sensitivity could be achieved only by assaying both acute-phase and paired serum specimens and measuring immunoglobulin G (IgG), IgA, and IgM antibodies to two pertussis antigens (pertussis toxin and filamentous hemagglutinin). Loss of sensitivity occurred with any reduction in the number of these serologic assays performed. Optimal laboratory diagnosis of endemic pertussis in a pediatric population requires both nasopharyngeal culture and serology by enzyme immunoassay.

Serum antibody response to filamentous hemagglutinin in patients with clinical pertussis measured by an enzyme-linked immunosorbent assay

Titers of antibodies to filamentous hemagglutinin (FHA) were determined by enzyme-linked immunosorbent assay in acute and convalescent phase serum samples from 158 patients with clinical symptoms typical of whooping-cough. In 96 of the patients the diagnosis was verified by culture. Significant changes in serum levels of IgG, IgM and/or IgA antibodies against FHA were demonstrated in 126 patients (80%). Thus, demonstration of significant changes in FHA antibody titers in serum can be used for serological diagnosis of pertussis. The results also show that high levels of IgG, IgM and/or IgA antibodies in a single serum sample suggest current pertussis infection, but if the diagnosis is based on determinations of FHA antibody titers in a single serum sample the sensitivity is low. The levels of antibody to FHA were compared with previously determined levels of antibodies to pertussis toxin. A significant antibody response against both FHA and pertussis toxin was seen in 111 patients (70%) while 147 patients (93%) developed a significant increase in antibodies against one or both antigens.

Enzyme-linked immunosorbent assay to evaluate the immunogenicity of a polyvalent Klebsiella capsular polysaccharide vaccine in humans

A highly sensitive enzyme-linked immunosorbent assay was developed for Klebsiella capsular polysaccharide (CPS) and used to evaluate the immunoglobulin G (IgG) antibody response to a 24-valent CPS vaccine in seven adult volunteers. The median rise in titer to all vaccine antigens in samples from the volunteers was significant (twofold or greater). Significant IgG responses to 11 immunologically related serotypes not included in the vaccine were also noted. The mean cross-reacting IgG titer of 127.2 was only slightly lower than the mean titer of 175.7 to the serotypes in the vaccine (P less than 0.05). The mean 29.9-fold increase in titer to the serotypes in the vaccine was significantly higher than the mean 13.5-fold increase in titer to the additional antigens (P less than 0.001). The difference was partly because of the significantly lower (P less than 0.01) natural antibody titers in the preimmune sera to the serotypes in the vaccine, compared with those to serotypes not included in the vaccine. The selection of vaccine serotypes was based on the frequency of serotype isolation from cases of Klebsiella bacteremia. The above findings, which show low levels of natural antibody to these serotypes, support the hypothesis that anti-CPS antibody is protective against bacteremic disease.

Clinical, metabolic, and antibody responses of adult volunteers to an investigational vaccine composed of pertussis toxin inactivated by hydrogen peroxide

A toxoid vaccine, composed of purified pertussis toxin inactivated with H2O2 (NICHD-Ptxd), was developed on the basis of evidence that serum neutralizing antibodies (antitoxin) would confer immunity to pertussis. In vivo and in vitro assays of NICHD-Ptxd showed only trace or nondetectable levels of pyrogenic, adenosine diphosphate-ribosyltransferase, binding and pharmacologic activities. Nevertheless, about 40% of the antigenicity of pertussis toxin was retained. Adult volunteers were injected, two times 6 weeks apart, with either 10 (n = 21), 50 (n = 25), or 75 (n = 30) micrograms/dose of one lot, Ptx-06, adsorbed onto AI(OH)3. Neither fever nor changes in the levels of leukocytes, lymphocytes, fasting blood glucose, or insulin were observed in the volunteers. The optimal immunizing dose, 50 micrograms, induced levels of antitoxin (geometric mean (GM) 302 U) comparable to those found in eight adults convalescent from pertussis (GM 269 U) and greater than those found in 18-month-old children after their fourth dose of diphtheria and tetanus toxoids and pertussis vaccine (GM 20.0 U, p less than 0.001). These data indicate that NICHD-Ptxd is safe and immunogenic in adults, and they justify its evaluation in infants and children.

Pertussis: the disease and new diagnostic methods

Bordetella pertussis, the causative agent of whooping cough, produces an acute and chronic respiratory infection in infants and young children. B. pertussis is still a major health problem of young children throughout the world even though effective immunization against whooping cough is available. While predominantly a childhood disease, it has been reported also to be a cause of persistent cough in adults. This review discusses the numerous bacterial virulence factors that may play roles in the pathogenesis of pertussis and in immunity to infection. The present problems with pertussis diagnosis, recent advances, and future prospects for new and improved rapid diagnostics tests also are explored.

Monoclonal antibody-based sandwich enzyme-linked immunosorbent assay for detection of Bordetella pertussis filamentous hemagglutinin

Hybrid cell lines producing monoclonal antibodies against Bordetella pertussis filamentous hemagglutinin (FHA) were established. The specificity of the antibodies was ascertained by enzyme-linked immunosorbent assay (ELISA), sandwich ELISA, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by electroblotting. The monoclonal antibody-based sandwich ELISA was developed for detection of B. pertussis FHA. The assay had a detection limit of B. pertussis FHA in concentrations ranging from 7 to 15 ng/ml. The assay was also able to detect whole B. pertussis, Bordetella parapertussis, and Bordetella bronchiseptica bacteria. No cross-reactions were observed with strains of Branhamella catarrhalis, Neisseria meningitidis, Haemophilus influenzae, Klebsiella pneumoniae, Legionella pneumophila, Streptococcus miteor, or Streptococcus pneumoniae. The monoclonal antibodies might be useful for the detection of soluble antigens and whole bacteria in clinical samples and for studies of the immunochemical structure of B. pertussis FHA.

Evaluation of serologic assays for diagnosis of whooping cough

An enzyme-linked immunosorbent assay (ELISA) for the immunoglobulin G (IgG), IgM, and IgA response to Bordetella pertussis filamentous hemagglutinin (FHA) and pertussis toxin (PT) and a neutralization test (NT) in a microplate tissue culture assay for neutralizing antibodies to PT were evaluated in paired sera from 90 patients with culture-confirmed pertussis. Eighty patients were children (age, less than 15 years), and 6 of 80 children had been immunized with three doses of diphtheria-tetanus-pertussis vaccine as infants. A significant titer rise (greater than or equal to twofold), determined by ELISA, of IgG, IgM, and IgA to FHA was recorded in 75 (83%), 28 (31%), and 47 (52%) of the patients, respectively. A significant titer rise to PT in IgG was found in 83 (92%), IgM in 29 (32%), and IgA in 44 (49%) of the patients. A significant titer rise to FHA or PT in IgG was found in 88 (98%) of the patients, in combination with a significant rise in the titer of IgA to FHA. These data were obtained in a single serum dilution of 1:500. Titrations performed later showed that the titer rise to FHA in IgG was a mean of 6.5-fold, which was significantly lower than the mean 67.0-fold rise in IgG to PT (P less than 0.001). The mean titer of IgG to FHA in convalescent-phase serum was 270, which was also significantly lower than the mean PT titer of 2,943 (P less than 0.001). A significant rise (greater than or equal to fourfold) in PT titer by NT was found in 58 of 83 (70%) of the patients. The NT was significantly less sensitive than the ELISA for the determination of the IgG titer to PT ( P< 0.001). Results showed that a 100% (90 of 90) sensitivity in terms of titer rises was achieved in the serologic diagnosis of pertussis by ELISA in a single-point determination of the IgG and IgA responses to FHA and of the IgG response to PT.

Immunoblot analysis of humoral immune responses following infection with Bordetella pertussis or immunization with diphtheria-tetanus-pertussis vaccine

To help develop better diagnostic tests for pertussis, we examined the serologic response to whole-cell proteins of Bordetella pertussis after natural infection or vaccination with diphtheria-tetanus-pertussis vaccine. Serum specimens collected during a pertussis outbreak investigation and from uninfected persons were used in Western blot (immunoblot) analyses to determine the presence of immunoglobulin G (IgG) and IgA antibodies to specific B. pertussis proteins. IgG antibodies to proteins of molecular masses 220 and 210 kilodaltons (kDa) were detected in 14 of 18 serum samples obtained from patients with culture-confirmed pertussis greater than or equal to 40 days after the onset of coughing. IgA antibodies were detected in 15 of the 18 samples. Of 19 serum samples obtained from patients who had not been ill with pertussis, 6 contained IgG antibodies to these proteins and 1 contained IgA antibodies. The two proteins bound antiserum specific for filamentous hemagglutinin and comigrated with purified filamentous hemagglutinin. IgG antibodies to two additional protein bands of molecular masses 84 and 75 kDa were associated with previous vaccination. Antibody to the 84-kDa protein was detected in 15 of 17 vaccinated, never-infected persons, and antibody to the 75-kDa protein was detected in 16 of the 17. None of 11 nonvaccinated, never-infected persons tested had antibodies to either protein. All seven fully vaccinated persons with culture-documented infection had antibodies to both proteins. Antibodies to the 84-kDa protein were detected in 6 of 22 nonvaccinated and infected persons, and antibodies to the 75-kDa protein were detected in 8 of the 22. Use of Western blot analysis in this study allowed us to distinguish antibody responses to infection and immunization.

Protective effect of acellular pertussis vaccines

Two acellular pertussis vaccines, a mono-component toxoid of pertussis toxin and a two-component vaccine containing both the toxoid and filamentous haemagglutinin, were used for primary immunization of infants 5 1/2 to 10 months of age in two clinical trials in Sweden. Over a follow-up period of 12 to 17 months, 37 children were exposed to pertussis in the household or a daycare centre. Only one child developed mild, culture-confirmed pertussis as opposed to the expected number of 30 to 33 cases based on an assumed attack rate of 80-90% in non-immunized children. These preliminary findings indicate that, given as primary immunization to infants, the vaccines provide protection against pertussis.

Specific immunoglobulin A to Bordetella pertussis antigens in mucosal secretion for rapid diagnosis of whooping cough

Specific immunoglobulin A (IgA) to Bordetella pertussis filamentous hemagglutinin (FHA) and pertussis toxin (PT) was determined in mucosal secretions by an enzyme-linked immunosorbent assay (ELISA). It took 3 to 4 h to complete the ELISA. The upper limits of normal values for age were determined in nasopharyngeal (NPH) secretions from 23 patients with viral infections and in 10 healthy adults working with pertussis patients or cultures. A significant IgA response to FHA was found in 38 of 54 (70%) and to PT in 28 of 54 (52%) NPH secretions from patients with pertussis confirmed by culture, serology, or both. The rate of positive responses to either antigen (44 of 54 [81%]) was significantly higher than that by culture alone (29 of 54 [54%]; P less than 0.01). The rate of positive responses increased from 65% in patients with symptoms for 1 week or less to 87 to 92% in patients with symptoms for 2 or more weeks. The specific IgA response to PT was found in 100% of NPH samples from 17 unimmunized children less than 3 years of age and in only 30% of adults and immunized children greater than 3 years of age. A response to FHA was found in 65 to 73% of the NPH secretions in all age groups. Saliva samples were found to contain specific IgA to FHA and PT in all age groups, but these were of diagnostic value in 50% (11 of 22) of the adult patients. The specificity of the ELISA was 100% (10 of 10 negatives) in NPH secretions from patients with pertussis-like cough who had negative cultures and serology. The results indicate that determination of specific IgA to PT and FHA in NPH aspirates represents a sensitive and rapid diagnostic method for the detection of pertussis.

Rapid diagnosis of whooping cough using monoclonal antibody

A counterimmunoelectrophoresis (CIE) method for antigen detection using monoclonal antibody was assessed for its ability to aid in the rapid diagnosis of Bordetella pertussis in 59 patients. A positive diagnosis from a combination of results from tests of serum and urine was obtained in 51 (87%) of cases. For sera, CIE had a sensitivity of 85% and a specificity of 94%; for urine samples the sensitivity was 81% and a specificity of 100%. Antigen detection by CIE is simple to perform and yields results on the same day, thus allowing treatment to begin at an early stage.

Antibody response to pertussis toxin in patients with clinical pertussis measured by enzyme-linked immunosorbent assay

Serum antibody response to pertussis toxin was measured by enzyme-linked immunosorbent assay in 172 patients with clinical symptoms typical of whooping cough. The diagnosis was verified by culture in 100 patients. Serum antibodies were either not detectable or present only at low levels in sera obtained in the early stage of disease. Significant changes in serum levels of IgG, IgM and/or IgA were demonstrated in 143 patients (83%). The lack of comparable increases in most of the other patients may be due to inappropriate timing of serum collection. Thus, detection of antibodies against pertussis toxin in paired serum samples can be used for serological diagnosis of pertussis. However, the presence of IgM and/or IgA in a single serum sample does not confirm a diagnosis of pertussis, since such antibodies were found in healthy adults as well as in patients two years after the disease. High levels of these antibodies are, however, suggestive of on-going or recent disease.

Management of pregnant women with contagious infections at delivery

Since 1970 pregnant women with contagious infections in the country of Stockholm have been delivered at the Danderyd Hospital, the only hospital in the area which has departments of obstetrics and pediatrics as well as infectious diseases. This paper presents data from a prospective study carried out during a period of 10 years (1975-1984). The study includes 303 women and their newborns who for various reasons were transferred to the Department of Infectious Diseases (DID) before or after delivery. A comprehensive microbiological investigation was made in order to establish an etiological diagnosis in all women included in the study. A possible transmission of the infection from the mother to her fetus/child before or after delivery was also investigated. Only 0.17% of the pregnant women in the area needed care at the DID at delivery or in the puerperal period. 9% of the deliveries occurred at another hospital, 32% at the DID and the remaining at the obstetrical department, Danderyd Hospital. The rate of complications, including cesarean sections, was 12%. Of the 165 women suffering from an infectious disease at the time of delivery, 40% had a verified viral disease--in most cases varicella or mumps, 28% had a bacterial infection and for 32% no etiology of the disease could be established. The study population also includes women suspected either to be incubated with a contagious disease or to be carriers of infectious agents, as well as healthy mothers whose newborns were expected to be carriers of infectious agents such as rubella and varicella. None of the women died during the study period but 5 were seriously ill and 3 needed intensive care. The rate of stillbirths was the same as reported among all births in the country of Stockholm but the perinatal mortality rate was significantly higher (see also a following article, ref. 27). Our routines prove the necessity to take special care of pregnant women carrying a contagious infectious agent at term.

Efficacy of enzyme-linked immunosorbent assay for rapid diagnosis of Bordetella pertussis infection

We examined the diagnostic efficacy of an enzyme-linked immunosorbent assay (ELISA) for class-specific antibodies to Bordetella pertussis in acute-phase sera collected from 1,240 patients with suspected pertussis. A total of 833 serum specimens (67%) yielded positive results. The proportion of positive results increased to 77% if a second (convalescent-phase) serum was also tested. By comparison, a bacterial agglutination test for B. pertussis antibodies was positive in only 21% of acute-phase specimens and 50% of paired specimens. The high proportion of acute-phase sera which were ELISA positive indicates that a measurable serologic response has usually occurred by the time the diagnosis is suspected. Thus, the ELISA is potentially the most rapid means of laboratory confirmation of B. pertussis infection.

Acellular pertussis vaccine in adults: adverse reactions and immune response

An acellular pertussis vaccine JNIH-6 containing pertussis toxin and filamentous hemagglutinin was evaluated in adult volunteers with regard to adverse reactions and antibody response. Adverse reactions were few and mild. A late onset local reaction was seen in 22 of the 47 vaccinees (47%) as compared to none of the 20 subjects receiving a placebo, the carrier solution of aluminium phosphate of the vaccine. The reaction, which manifested itself on the 6th to 8th day after vaccination, consisted in all cases of an induration and/or swelling considered insignificant by the majority of the subjects. The reaction was only found in vaccinees receiving a first dose of vaccine and was independent of the prevaccination antitoxin level. The vaccine induced a highly satisfactory antibody response to both filamentous hemagglutinin and pertussis toxin.

Adverse reactions and antibody responses to acellular pertussis vaccine

Two types of acellular pertussis vaccine are used in Japan: the filamentous hemagglutinin (F-HA) predominant type and the pertussis toxin (PT)-F-HA type. We tested one lot of vaccine from each of three manufacturers (lots A and B, F-HA predominant type; lot C, PT-F-HA type). One hundred fifteen healthy children between the ages of 3 months and 23 months were immunized with one of the three lots of acellular pertussis vaccine to assess adverse reactions and antibody responses. The incidence of fever (temperature greater than or equal to 38 degrees C) was 2.6% for lot A, 1.2% for lot B, and 2.5% for lot C. The incidence of local reactions greater than 5 cm in diameter was 1.9% for lot A, 2.4% for lot B, and 3.3% for lot C. Thus no significant differences in adverse reaction were observed. The anti-PT antibody responses in the tested vaccines were equal to or greater than those in patients with pertussis in the convalescent stage, and the anti-F-HA antibody responses were far higher than those of convalescing patients. Lot C produced the highest anti-PT antibody, and Lot A the highest anti-F-HA antibody.

Antitoxin in human pertussis immune globulins

The level of antitoxin i.e. neutralizing antibodies to pertussis toxin, or lymphocytosis promoting factor, was determined in six pertussis immune globulin preparations from different manufactures. A comparison with antitoxin levels after natural pertussis disease in adults showed that pertussis immune globulins did not contain more antitoxin than convalescent phase sera, i.e. they had very low antitoxin content for specific immune globulins. Agglutinin and anti-FHA titres were relatively higher in immune globulins, probably reflecting a difference between the antibody response elicited by whole cell vaccines used for hyperimmunization in immune globulin production and by natural disease. The low antitoxin content of currently available pertussis immune globulin preparations could explain the inefficacy or conflicting results obtained with these products in prophylaxis and therapy of whooping cough.

The carrier state in pertussis

In order to determine whether healthy adults can be of importance for the spread of pertussis the nasopharyngeal flora of 391 healthy individuals working in close contact with children was investigated during the height of a pertussis epidemic. Only 1 carrier of Bordetella pertussis was found, even though all individuals were exposed to the organism during the study period through their work.

Pertussis vaccine: present status and future prospects

Use of killed whole-cell Bordetella pertussis vaccines has been a major factor in control of symptomatic whooping cough (pertussis). In the UK, diminished public confidence in the safety of this vaccine led to a reduction in vaccine acceptance which correlated with an increase in the incidence of pertussis. There is a need for acellular pertussis vaccines of low toxicity which, ideally, will prevent colonization and also protect against the disease symptoms. Vaccine design can rely increasingly on knowledge of the roles of individual bacterial components in the pathogenesis of pertussis. Serotype-specific agglutinogens 2 and 3 (fimbriae) and filamentous haemagglutinin are among surface components of B. pertussis which probably mediate adhesion to the respiratory mucosa. Systemic effects of pertussis can largely be attributed to the lymphocytosis promoting factor (pertussis toxin). Vaccines containing detoxified toxin plus one or more purified adhesins are envisaged at present.

Bordetella pertussis whole cell vaccines--efficacy and toxicity

The literature concerning efficacy and side effects of pertussis vaccines is reviewed. With few exceptions, most vaccines induce a protective immunity lasting for 2 to 5 years. The large-scale use of pertussis vaccines has markedly contributed to the decrease in pertussis morbidity in small children but in some countries the incidence has increased in older children. Not even countries with immunisation rates of 90-95% have managed to eradicate pertussis or prevent disease in infants below the age of immunisation. The pertussis-associated mortality is currently very low in the industrialised countries and no differences can be discerned when countries with high, low and zero immunisation rates are compared. Local and benign systemic reactions are commonly seen after immunisation. The vaccines also sometimes cause convulsions, a shock-like state and, rarely, serious neurological reactions.

Diagnosis of pertussis

During a local outbreak of pertussis mainly involving school-children and adults, 71 patients with suspected whooping cough and 25 of their household contacts were studied in the course of 1 day so as to compare enzyme-linked immunosorbent assay (ELISA) with bacterial isolation in the diagnosis of pertussis. Serum samples and two nasopharyngeal swabs were collected from all persons. Five different culture media were used. Twenty-eight cases were diagnosed within 2 days by measuring IgM- and IgA-class antibodies to Bordetella pertussis in the first serum samples of patients. Fifty cases were identified when paired serum samples were used. Cultures were positive in only nine patients. The results show that ELISA is a valuable aid in the diagnosis of pertussis in patients with negative cultures.

Diagnosis of whooping cough--a comparison of culture, immunofluorescence and serology with ELISA

Three methods for diagnosis of whooping cough--culture, immunofluorescence (IF) technique on nasopharyngeal secretion and serology with ELISA--were compared. 52 patients with symptoms of upper respiratory tract infection, which could not exclude pertussis as a differential diagnosis, were investigated. Pertussis infection was confirmed in 30 patients. Of these 16 (53%) were found by culture, 19 (63%) by IF and 28 (93%) by serology. It is concluded that IF analysis of nasopharyngeal secretion is a valuable tool for rapid diagnosis of whooping cough with a sensitivity similar to that of culture. Serodiagnosis with ELISA added a significant number of positive patients in which culture and IF were negative.

Serological response to filamentous hemagglutinin and lymphocytosis-promoting toxin of Bordetella pertussis

Serum antibody responses to the filamentous hemagglutinin and the lymphocytosis-promoting toxin of Bordetella pertussis after vaccination with diphtheria and tetanus toxoids and pertussis vaccine, adsorbed, were assayed by using the enzyme-linked immunosorbent assay. The effect of early immunization, during the first week of life, on the antibody response also was determined. After vaccination, immunoglobulin G (IgG) and IgM directed against both the filamentous hemagglutinin and the lymphocytosis-promoting toxin were detected. Generally, antibody titers increased with subsequent injections and the age of the children. Maternal antibodies against filamentous hemagglutinin and lymphocytosis-promoting toxin were detected in cord blood. The ability of an infant to produce serum IgG anti-lymphocytosis-promoting toxin after vaccination with pertussis vaccine was inversely related to the cord blood serum IgG anti-lymphocytosis-promoting toxin titer at birth. A good antibody response was observed in infants with low cord blood titers, and a poor antibody response was seen in infants with high cord blood values. The IgM anti-lymphocytosis-promoting toxin response was good in groups with both low and high cord blood titer, with no significant difference observed between the two groups. No IgA anti-lymphocytosis-promoting toxin or IgA anti-filamentous hemagglutinin titers were observed in vaccines. IgA antibodies were observed in convalescent sera from two adults and may be presumptive evidence of infection with B. pertussis.