How to fight pertussis?

Oral fluid-based lateral flow point-of-care assays for pertussis serology

Introduction. Current serological diagnosis of pertussis is usually performed by ELISA, which is typically performed in larger diagnostic or reference laboratories, requires trained staff, and due to sample batching may have longer turnaround times.Hypothesis and Aim. A rapid point-of-care (POC) assay for pertussis serology would aid in both the diagnosis and surveillance of the disease.Methodology. A quantitative lateral flow (LF)-based immunoassay with fluorescent Eu-nanoparticle reporters was developed for the detection of anti-pertussis toxin (PT) and adenylate cyclase toxin (ACT) antibodies from oral fluid samples (N=100), from suspected pertussis cases with respiratory symptoms.Results. LF assay results were compared to those obtained with anti-PT IgG oral fluid ELISA. For an ELISA cut-off value of 50 arbitrary units, the overall agreement between the assays was 91/100 (91 %), the sensitivity was 63/70 (90 %) and the specificity was 28/30 (93 %). No ACT-specific antibodies were detected from oral fluid samples; however, the signal readout positively correlated to those patients with high anti-PT IgG antibodies.Conclusion. The developed LF assay was a specific, sensitive and rapid test for serological diagnosis of pertussis with anti-PT antibodies and is a suitable POC test using oral fluid samples.

Whole blood based point-of-care assay for the detection of anti-pertussis toxin IgG antibodies

Current serological diagnosis of pertussis is usually done by ELISA to determine serum specific anti-pertussis toxin (PT) IgG antibodies. However, the ELISAs are often central-laboratory based, require trained staff, and have long turnaround times. A rapid point-of-care (POC) assay for pertussis serology would aid in both diagnosis and surveillance of the disease. In this study, a quantitative lateral flow assay (LFA) with fluorescent Eu-nanoparticle reporters was used for the detection of anti-PT antibodies from whole blood. The assay was evaluated by testing overall 141 samples including 25 before and 116 one month after acellular pertussis booster vaccination. LFA results were compared to those obtained with standardized anti-PT IgG ELISAs with paired serum samples. Correlation between the assays was high (Pearson R = 0.832), and the achieved analytical sensitivity of the LFA was 29 IU/mL, which would be sufficient for clinically relevant cutoffs for determining recent infections. The paired samples, collected pre- and post-booster, demonstrated a significant increase in anti-PT IgG antibodies similar to that detected by ELISA. The developed LFA opens up several alternatives for a suitable POC test also in middle- and low-income countries.

Pertussis: New preventive strategies for an old disease

In the last twenty years, despite high vaccination coverage, epidemics of pertussis are occurring in both developing and developed countries. Many reasons could explain the pertussis resurgence: the increasing awareness of the disease, the availability of new diagnostic tests with higher sensitivity, the emergence of new Bordetella pertussis (B. pertussis) strains different from those contained in the current vaccines, the asymptomatic transmission of B. pertussis in adolescents and adults and the shorter duration of protection given by the acellular pertussis (aP) vaccine. New preventive strategies have already been implemented, such as booster doses of aP vaccine in adolescents and adults, maternal immunisation during pregnancy and the "cocooning" strategy, but more are still needed. Knowing what is new about this old disease is necessary to reduce its incidence and to protect infants too young to be vaccinated, which have the highest risk of complications and death.

Promoting Adult Pertussis Vaccination in the Workplace

Vaccines are an important disease prevention strategy among individuals of all age groups. Despite the success of vaccinations in preventing communicable diseases, adults, in particular, often have sub-optimal vaccination rates. Consequently, some vaccine-preventable diseases, such as pertussis, are still on the rise in the United States despite the availability of the Tdap vaccine. As most adults can be found in the workplace, occupational and environmental health nurses are in a unique position to encourage employers to promote adequate Tdap vaccination among their employees. As specific resources regarding Tdap vaccination are lacking, the Pertussis Prevention Toolkit was developed to help occupational health nurses promote Tdap vaccination in the workplace.

Study on Toxicity Reduction and Potency Induction in Whole-cell Pertussis Vaccine by Developing a New Optimal Inactivation Condition Processed on Bordetella pertussis

Background

Whooping cough is caused by Bordetella pertussis, and it remains a public health concern. Whole-cell pertussis vaccines have been commonly employed for expanded immunization. There is no doubt of the efficacy of whole cell pertussis vaccine, but it is necessary to improve the vaccine to decrease its toxicity.

Objectives

In this study, an inactivation process of dealing with pertussis bacteria is optimized in order to decrease the bacteria content in human doses of vaccines and reduce the vaccine’s toxicity.

Materials and Methods

The bacterial suspensions of pertussis strains 509 and 134 were divided into 21 sample parts from F₁ to F₂₁ and inactivated under different conditions. The inactivated suspensions of both strains were tested for opacity, non-viability, agglutination, purity, and sterility; the same formulation samples that passed quality tests were then pooled together. The pool of inactivated suspensions were analyzed for sterility, agglutination, opacity, specific toxicity, and potency.

Results

The harvest of both bacterial strains showed purity. The opacity of various samples were lost under different treatment conditions by heat from 8% to 12%, formaldehyde 6% to 8%, glutaraldehyde 6% to 8%, and thimerosal 5% to 8%. Tests on suspensions after inactivation and on pooled suspensions showed inactivation conditions not degraded agglutinins of both strains. The samples of F₂, F₄, F₈, F₁₂, F₁₅, and F₁₇ passed the toxicity test. The potency (ED50) of these samples showed following order F₁₇ > F₁₂ > F₈ > F₁₅, F₄ > F₂, and F₁₇ revealed higher potency compared to other formulations.

Conclusions

It can be concluded that F₁₇ showed desirable outcomes in the toxicity test and good immunogenicity with a low bacterial number content. Consequently, lower adverse effects and good immunogenicity are foreseeable for vaccine preparation with this method.

Seroprevalence studies of pertussis: what have we learned from different immunized populations

Bordetella pertussis is a pathogen-causing whooping cough (pertussis) in humans. Although vaccination against the disease is effective, the bacterium is still circulating among population and can even cause death. Especially young infants, who lack protection, are vulnerable. The laboratory diagnostic methods to detect B. pertussis are culture, PCR and ELISA serology. Reported cases of the disease vary among countries but usually the incidence rates are low, <1 to 10/100 000. However, pertussis often goes unrecognized among patients as it presents itself like the common cold, especially in adults and elders who are often the source of the infection. This makes pertussis difficult to monitor and control. Serological surveillance is an easy manner to estimate the real burden of the disease among population. Furthermore, to have reliable results, anti-PT IgG antibodies should be measured, as PT is the only specific antigen to B. pertussis. This review aims to evaluate available pertussis seroprevalence studies throughout the world, and to compare the findings from countries with different vaccination histories and strategies. Estimation of the real burden of pertussis is compared to reported numbers. In addition, future aspects in seroprevalence studies are considered.

The role of Toll-like receptor 4 polymorphisms in vaccine immune response

Toll-like receptors (TLRs) are a class of pattern recognition receptors that are deputed to recognise a range of molecular structures in pathogens. One of the most studied members of this family is the TLR4, which is essential for the signalling of lipopolysaccharide. The gene encoding for TLR4 is highly polymorphic and this genetic variability may explain in part the interindividual variability observed in several clinical setting, including the response to vaccination. Herein, we review and systematise the available scientific evidence about the effect of TLR4 polymorphisms on vaccine response, including approved prophylactic, new therapeutic cancer vaccines and recently approved vaccine adjuvants. Data reviewed in this analysis indicate that TLR4 polymorphisms significantly affect vaccine response. If these results are confirmed by further analyses, the use of these genetic biomarkers may become a useful tool to tailor vaccination in specific subsets of patients.

Pertussis

Pertussis continues to be an important public-health issue. The high immunization coverage rates achieved, mainly in industrialized countries, have certainly decreased the spread of the pathogen. However, as immunity wanes, adolescents and adults play an important role in the dynamics of the infection. The surveillance system has several limitations and the underestimation of pertussis in adolescents, young adults and adults is mainly related to the atypical clinical characteristics of cases and the lack of lab confirmation. The real epidemiological impact of pertussis is not always perceived. The unavailability of comprehensive data should not hamper the adoption of active prophylactic measures designed to avoid the impact of waning immunity against pertussis. Different immunization strategies have been suggested and/or already adopted such as immunization of newborns, pre-school and school children, adolescents, adults, healthcare workers, childcare workers, pregnant women, cocoon strategy. Prevention of pertussis requires an integrated approach and the adoption of different immunization strategies, with the objective of achieving and maintaining high coverage rates.

Bordetella pertussis: an underreported pathogen in pediatric respiratory infections, a prospective cohort study

Background

The incidence of pertussis has been increasing worldwide. In the Netherlands, the seroprevalence has risen higher than the reported cases, suggesting that laboratory tests for pertussis are considered infrequently and that even more pertussis cases are missed. The objective of our study was to determine the frequency of pertussis in clinically unsuspect cases compared to suspect cases with the intention of finding clinical predictors.

Methods

The present prospective cohort study was part of a controlled clinical trial evaluating the impact of molecular diagnostics on clinical decision making in pediatric respiratory infections, performed during 2 winter seasons. For this study, in the first season pertussis was only tested in case of clinical suspicion, in the second season, pertussis was also tested without clinical suspicion. Multivariate and univariate analysis were performed using SPSS 18 and Statistical software ‘R’.

Results

In the two seasons respectively 22/209 (10,5%) and 49/373 (13,1%) cases were clinically suspected of pertussis. Bordetella pertussis was detected by real time RT-PCR in respectively 2/22 (9,1%) and 7/49 (14,3%) cases. In the second season an additional 7 cases of pertussis were found in clinically unsuspected cases (7/257 = 2,7%). These additional cases didn’t differ in clinical presentation from children without a positive test for pertussis with respect to respiratory symptoms.

Conclusions

Pertussis in children sometimes mimics viral respiratory tract infections. If pertussis diagnostics are based on clinical suspicion alone, about 1 in 5 cases (19%) is missed. Despite widely accepted clinical criteria, paroxysmal cough is not a good predictor of pertussis. To prevent spreading, physicians should include B. pertussis in routine diagnostics in respiratory tract infections.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2334-14-526) contains supplementary material, which is available to authorized users.