A marked decrease in L-selectin expression by leucocytes in infants with Bordetella pertussis infection: leucocytosis explained?

Normal B cell ranges in infants: A systematic review and meta-analysis

BACKGROUND

During the first year of life, B cell level is a valuable indicator of whether external factors, such as exposure to B cell depleting therapies, have an adverse impact on immune system development. However, there are no standard reference ranges of B cell levels in healthy infants by age.

OBJECTIVE

To estimate the normal range of B cell levels in infants, by age, during the first year of life, by pooling data from published studies.

METHODS

Studies reporting B cell levels measured using flow cytometry and CD19 markers in healthy infants were identified via a systematic literature review. Quality and feasibility assessments determined suitability for inclusion in meta-analyses by age group and/or continuous age. Means and normal ranges (2.5th-97.5th percentile) were estimated for absolute and percentage B cell levels. Sensitivity analyses assessed the impact of various assumptions.

RESULTS

Of 37 relevant studies identified, 28 were included in at least 1 meta-analysis. Means and normal ranges of B cell levels were found to be 707 (123-2324) cells/μL in cord blood, 508 (132-1369) cells/μL at age 0-1 month, 1493 (416-3877) cells/μL at age 1-6 months and 1474 (416-3805) cells/μL at age >6 months. The continuous age model showed that B cell levels peaked at week 26. Trends were similar for the percentage B cell estimates and in sensitivity analyses.

CONCLUSION

These meta-analyses provide the first normal reference ranges for B cell levels in infants, by week of age, during the first year of life.

Pertussis in early life: underdiagnosed, severe, and risky disease. A seven-year experience in a pediatric tertiary-care hospital

AIM

Pertussis continues to be a common worldwide infection in pediatric and adult populations.We aimed to study epidemiological and clinical characteristics of infants and children admitted for pertussis to a tertiary-care hospital and to investigate the risk factors for pediatric intensive care unit (PICU) admission.

MATERIALS AND METHODS

With a retrospective study, we analyzed all medical reports of patients admitted to Bambino Gesù Children's Hospital in Rome from January 2011 to December 2018 with a diagnosis of pertussis.

RESULTS

We examined 195 patients. The majority of hospitalized children (66.15%) were <3 months of age. No mother had received pertussis containing vaccine during pregnancy. Ten cases required admission in PICU. The age at admission was lower in PICU patients with respect to ward patients (42.8 vs 240 days; p < .0007), length of hospital stay was longer in PICU group (24.7 vs 7.52 days; p < .003). Patients who needed PICU admission had greater white blood cell count at hospital admission compared with those hospitalized in the pediatric ward. One infant died and one had encephalitis.

CONCLUSIONS

Pertussis is a remerging disease. In infants, it is associated with significant morbidity and mortality. In recent years, many countries have implemented different vaccination strategies and public health measures to prevent the increase in pertussis cases. Maternal vaccination has been shown to be highly protective for infants <3 months of age before they can develop their own immunity via vaccination.

Neurologic alterations in an HIV adult patient with pertussis: a case report

Background

Pertussis is a highly contagious disease of public health interest caused by the bacterium Bordetella pertussis. Although its incidence has decreased substantially after the introduction of a vaccination, the burden of the disease remains high. Although the paroxysmal phase is highly disabling, complications are uncommon and more prevalent in children than in adults. The most frequent neurological complication is encephalopathy, but seizures, paresis, paraplegia, ataxias, aphasias, and decerebration postures have also been described. The complication of decerebration postures has not been previously reported in adults.

Case presentation

We present a video case of an adult HIV patient with severe coughing paroxysms, post-tussive emesis and syncope, whose workup confirmed the diagnosis of a B. pertussis respiratory infection. During hospitalization, he had fluctuant encephalopathy and post-tussive decerebration postures following paroxysms. He was treated with antibiotic therapy and finally sent home without residual neurological deficits.

Conclusion

This case illustrates the biological plausibility of neurologic complications of pertussis in adults, which, albeit rare, can cause important morbidities. Future research should explore whether there are differences in the clinical presentation, risk factors and pathophysiology of the disease among adults or interventions aimed at preventing or treating pertussis encephalopathy.

Association of Pertussis Toxin with Severe Pertussis Disease

Pertussis, caused by respiratory tract infection with the bacterial pathogen Bordetella pertussis, has long been considered to be a toxin-mediated disease. Bacteria adhere and multiply extracellularly in the airways and release several toxins, which have a variety of effects on the host, both local and systemic. Predominant among these toxins is pertussis toxin (PT), a multi-subunit protein toxin that inhibits signaling through a subset of G protein-coupled receptors in mammalian cells. PT activity has been linked with severe and lethal pertussis disease in young infants and a detoxified version of PT is a common component of all licensed acellular pertussis vaccines. The role of PT in typical pertussis disease in other individuals is less clear, but significant evidence supporting its contribution to pathogenesis has been accumulated from animal model studies. In this review we discuss the evidence indicating a role for PT in pertussis disease, focusing on its contribution to severe pertussis in infants, modulation of immune and inflammatory responses to infection, and the characteristic paroxysmal cough of pertussis.

Role of Major Toxin Virulence Factors in Pertussis Infection and Disease Pathogenesis

Bordetella pertussis produces several toxins that affect host-pathogen interactions. Of these, the major toxins that contribute to pertussis infection and disease are pertussis toxin, adenylate cyclase toxin-hemolysin and tracheal cytotoxin. Pertussis toxin is a multi-subunit protein toxin that inhibits host G protein-coupled receptor signaling, causing a wide array of effects on the host. Adenylate cyclase toxin-hemolysin is a single polypeptide, containing an adenylate cyclase enzymatic domain coupled to a hemolysin domain, that primarily targets phagocytic cells to inhibit their antibacterial activities. Tracheal cytotoxin is a fragment of peptidoglycan released by B. pertussis that elicits damaging inflammatory responses in host cells. This chapter describes these three virulence factors of B. pertussis, summarizing background information and focusing on the role of each toxin in infection and disease pathogenesis, as well as their role in pertussis vaccination.

Fatal Pertussis in the Neonatal Mouse Model Is Associated with Pertussis Toxin-Mediated Pathology beyond the Airways

In infants, Bordetella pertussis can cause severe disease, manifested as pronounced leukocytosis, pulmonary hypertension, and even death. The exact cause of death remains unknown, and no effective therapies for treating fulminant pertussis exist. In this study, a neonatal mouse model of critical pertussis is characterized, and a central role for pertussis toxin (PT) is described. PT promoted colonization, leukocytosis, T cell phenotypic changes, systemic pathology, and death in neonatal but not adult mice. Surprisingly, PT inhibited lung inflammatory pathology in neonates, a result which contrasts dramatically with observed PT-promoted pathology in adult mice. Infection with a PT-deficient strain induced severe pulmonary inflammation but not mortality in neonatal mice, suggesting that death in these mice was not associated with impaired lung function. Dissemination of infection beyond the lungs was also detected in neonatal mice, which may contribute to the observed systemic effects of PT. We propose that it is the systemic activity of pertussis toxin and not pulmonary pathology that promotes mortality in critical pertussis. In addition, we observed transmission of infection between neonatal mice, the first report of B. pertussis transmission in mice. This model will be a valuable tool to investigate causes of pertussis pathogenesis and identify potential therapies for critical pertussis.

Pertussis leukocytosis: mechanisms, clinical relevance and treatment

The significant and sometimes dramatic rise in the number of circulating white blood cells (leukocytosis) in infants suffering from pertussis (whooping cough) has been recognized for over a century. Although pertussis is a disease that afflicts people of all ages, it can be particularly severe in young infants, and these are the individuals in whom leukocytosis is most pronounced. Very high levels of leukocytosis are associated with poor outcome in infants hospitalized with pertussis and modern treatments are often aimed at reducing the number of leukocytes. Pertussis leukocytosis is caused by pertussis toxin, a soluble protein toxin released by Bordetella pertussis during infection, but the exact mechanisms by which this occurs are still unclear. In this minireview, I discuss the history of clinical and experimental findings on pertussis leukocytosis, possible contributing mechanisms causing this condition and treatments aimed at reducing leukocytosis in hospitalized infants. Since recent studies have detailed significant associations between specific levels of pertussis leukocytosis and fatal outcome, this is a timely review that may stimulate new thinking on how to understand and combat this problem.

Leukocytosis

An increased white blood cell count, or leukocytosis, is a common laboratory finding. Appropriate specimen evaluation depends on which lineages are increased and the morphologic findings on peripheral blood smear review to guide further testing. The presence of blasts is concerning for acute leukemia and may require bone marrow biopsy. Lymphocytosis may be morphologically divided into polymorphic and monomorphic populations. Polymorphic lymphocytosis is most consistent with a reactive process, while monomorphic populations are concerning for lymphoproliferative neoplasm. The differential can be further narrowed based on morphologic findings. Myeloid leukocytosis can occur in a number of reactive conditions as well as myeloid malignancies. The types of cells present and morphology can help to guide additional workup. This study provides guidance for the appropriate evaluation and further workup of leukocytosis.

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.

Longitudinal analysis of activation markers on monocyte subsets during the development of simian immunodeficiency virus encephalitis

Lentiviral encephalitis has been hypothesized to be associated with altered monocyte migration into the brain. CD14(hi)/CD16(lo) and CD14(lo)/CD16(hi) monocytes were expanded during acute infection; however, this expansion was not unique or greater in macaques that developed encephalitis. The proportion of monocytes that expressed CD62L, HLA-DR, CD16, CD64, and CD40 varied during the course of infection in macaques that eventually developed encephalitis. Taken together, these results suggest that changes in the proportion of circulating activated monocytes are not predictive of development of encephalitis, but this does not rule out the importance of activated monocytes in the development of encephalitis.

Diagnostic markers for neonatal sepsis

PURPOSE OF REVIEW

To review the current evidence on the use of infection markers for diagnostic evaluation of sepsis in neonates.

RECENT FINDINGS

Recent research in immunology has led to the discovery of cell surface antigens, chemokines, cytokines and acute phase proteins that can potentially be used to 'rule in' or 'rule out' sepsis. The diagnostic utilities of key inflammatory mediators, including CD11b, CD64, interleukin-6 and interleukin-8, are promising and likely to become increasingly used as markers of infection for both diagnostic and prognostic purposes.

SUMMARY

Serial measurements and use of combinations of markers have been reported to improve sensitivity and negative predictive value of these tests. Current markers are not infallible, however, and do not permit neonatologists to withhold antibiotics in sick infants with suspected infection. Thus, many have emerged as useful indicators for early discontinuation of unnecessary antimicrobial therapy. Some infection markers are also useful for identifying infants with severe infection and adverse prognosis. Advances in flow cytometry have allowed simultaneous measurement of key markers using only minimal blood volume. Judicious selection of a panel of markers with complementary properties could greatly increase the ability of neonatologists to diagnose infection and discern valuable prognostic information.

Increased intracellular pro- and anti-inflammatory cytokines in bronchoalveolar lavage T cells of stable lung transplant patients

BACKGROUND

Allograft rejection remains a major cause of morbidity and mortality following lung transplantation and is associated with an increased expression of T-cell proinflammatory cytokines. We have recently shown that peripheral blood T-cell proinflammatory cytokine production was significantly reduced in stable lung transplant patients consistent with immunosuppression therapy. However, analysis of inflammatory cytokine profiles in bronchoalveolar lavage (BAL) T cells may be more relevant than peripheral blood T cells for assessing graft status.

METHODS

To investigate the immunomodulatory effects of currently used immunosuppressive regimens on BAL T-cell cytokine production, whole blood and BAL from stable lung transplant patients and control volunteers was stimulated in vitro and cytokine production by CD8+ and CD4+ T-cell subsets determined using multiparameter flow cytometry.

RESULTS

There was a significant decrease in T-cell proinflammatory cytokine production in BAL compared with blood from control subjects but not transplant patients. Anti-inflammatory cytokine IL-4 was increased in BAL compared with blood from both groups. There was a significant increase in IFNgamma, IL-2, IL-4, TGFbeta, and TNFalpha production by CD8 T cells and IFNgamma and TNFalpha production by CD4 T cells in BAL from transplant patients compared with controls.

CONCLUSIONS

We have shown decreased T-cell pro- and anti-inflammatory cytokine production in BAL compared with blood in control subjects but not in stable lung transplant patients. Current immunosuppression protocols have limited effect on T-cell proinflammatory cytokine production in BAL but do upregulate anti-inflammatory cytokines IL-4 and TGFbeta. Drugs that effectively reduce T-cell proinflammatory cytokine production in BAL may improve current protocols for reducing graft rejection in these patients.

Infection of newborn piglets with Bordetella pertussis: a new model for pertussis

Bordetella pertussis is the causative agent of pertussis or whooping cough. This bacterium is a human pathogen that under experimental conditions also infects selected rodents and primates. Here, we show for the first time that newborn piglets can be infected with B. pertussis when it is delivered intrapulmonarily. Infected piglets displayed fever and respiratory symptoms, such as nasal discharge, nonparoxysmal coughing, and breathing difficulties. Eventually, all infected animals developed severe bronchopneumonia, which in some cases was combined with a fibrinous pleuritits. Immunohistochemical staining revealed the presence of large numbers of B. pertussis cells within airways, adhering to the epithelial lining or phagocytosed by macrophages and neutrophils. Viable bacteria were reisolated from bronchoalveolar lavages and lung lesions for more than 10 days postinfection. The systemic presence of pertussis toxin was shown by hypoglycemia, lymphocytosis, and induction of a clustered pattern of CHO cells by serum and bronchoalveolar lavage samples. Thus, a large-animal model for pertussis was developed, which should complement existing rodent models for identifying the immune responses relevant to the design of new vaccines. In particular, this model should help researchers analyze the roles of both maternal and mucosal immunity in disease protection against pertussis and should ultimately assist in the design of new vaccines for early life protection.

Rapid simultaneous measurement of multiple cytokines using 100 microl sample volumes--association with neonatal sepsis

Early diagnosis of neonatal infection has proved problematic due to the inadequacy of currently available laboratory tests. Neonatal sepsis is associated with an increase in plasma-derived cytokine levels, but an increase of a single cytokine cannot identify neonatal sepsis specifically and multiple cytokine levels are required. The time constraints and relatively large volume of plasma required to measure multiple cytokines from newborn infants by conventional enzyme-linked immunosorbent assay (ELISA) techniques is prohibitive. We therefore applied cytometric bead array (CBA) technology for simultaneous measurement of multiple cytokines from a group of 18 term neonates with infection confirmed by culture and a control group. 'Normal' ranges were established for each cytokine from 1-7-, 8-14- and 15-21-day-old newborns. There was no significant change in the levels of cytokines from infants in different control age groups, suggesting that basal cytokine levels are unchanged in the first 3 weeks of life. In the patient groups, however, there was a significant difference in several cytokines between the different age groups. Interleukin (IL)-6, IL-10 and IL-12 were increased significantly in the 1-7-day-old patient group compared to either the 8-14 and 15-21 age group, suggesting that infection in utero is associated with increased levels of these cytokines compared to infection acquired following birth. When individual patient cytokine levels were compared to normal control reference ranges, two patients failed to show significant elevation of any cytokine tested. All other patients showed elevated levels of between one and nine cytokines tested (mean of 4.6). There was no correlation between elevated cytokine levels and types of infective organism or patient age. In conclusion, neonatal sepsis is associated with the elevation of multiple plasma cytokines. The use of CBA kits is a rapid, easy, low sample volume and sensitive method to measure multiple plasma cytokines.

Mushroom plant workers experience a shift towards a T helper type 2 dominant state: contribution of innate immunity to spore antigen

Contemporary mushroom factories are places where there is a substantial risk of the occurrence of respiratory allergy. The aims of this investigation were to estimate its causative agents and to evaluate the contribution of innate immune response in mushroom workers who cultivate Hypsizigus marmoreus (Bunashimeji). Cross-sectional and follow-up studies were performed in the factory. We investigated CD1b, CD3, CD4, CD8, CD14, CD45RO, CD62L and CD161 expression in peripheral blood mononuclear cells (PBMC) by flow cytometry, and serum levels of interleukin (IL-2), IL-4, granulocyte-macrophage colony stimulating factor (GM-CSF), IL-13 and interferon (IFN)-gamma by enzyme-linked immunosorbent assay (ELISA). Co-culture experiments of PBMC with spore extracts were also performed. Percentages of CD1b+ monocytes, natural killer (NK), NK T and CD4+ T cells were increased in the workers compared with controls. Increases in Th2 type cells, Th2/Th1 ratio and serum IL-13 and decreased IFN-gamma were detected, indicating a Th2-biased status of the workers. The follow-up study showed that monocytes and NK cells increased soon after employment while CD4+ T, Th2 and NK T cells increased gradually as employment time lengthened. Serum precipitating antibody to the mushroom antigen could be detected at a later stage. Co-cultivation of PBMC with the spore extracts induced much higher CD1b expression, and suppressed secretion of Th1 cytokine in culture supernatants. These results indicate that the mushroom antigen contains highly immunogenic substances which stimulate PBMC into a Th2-biased in vivo status, and innate immune cells might also play a critical role in developing respiratory allergy in mushroom workers.

Multiple leucocyte activation markers to detect neonatal infection

Diagnosis of congenital or neonatal infection is often based on clinical signs. However, clinical symptoms of infections may not be specific, and for this reason early diagnosis is often determined on results of laboratory tests, which may not currently be adequate. A more reliable method of detection of infection may be the demonstration of activated lymphocytes, which can be conducted rapidly and before the isolation of the infected organism. We have shown that detection of up-regulation of CD45RO, an activated/memory isoform of CD45 present on T cells, provides a reasonably sensitive screening test for neonatal infection. We also showed that dual expression of CD45RA/CD45RO was up-regulated early during the infective process in neonates with documented infection. However, other leucocytes are also activated during the infective process. To improve the sensitivity of the neonatal infection screening test and to identify the types of leucocytes involved in the immune response to the infective organism, we studied further the up-regulation of a comprehensive range of surface activation markers on T cells, monocytes and natural killer (NK) cells from a group of 17 newborn patients with positive culture, a group of 40 possibly infected patients based on clinical signs and a control group. 'Normal' ranges were established for each activation marker for each leucocyte subset from 1 to 7 and 7-14-day-old newborns <35 weeks' gestation and 35-40 weeks' gestation. There was a significant increase in the percentage of T cells expressing CD25 in the peripheral blood from infants at 2 weeks of age. Expression of HLA-DR on T cells, CD25 and CD69 on monocytes and HLA-DR on NK cells was also increased significantly in the peripheral blood from infants at 2 weeks of age and may reflect a maturation of these functional surface molecules. Up-regulation of CD69 on NK cells was the most sensitive marker for neonatal sepsis (positive in 13/16 patients). CD69 and CD25 expression was increased significantly on T cells in 11/17 and 10/17 patients, respectively. A combination of CD45RA/CD45RO and CD45RO identified 11/16 infected patients. Measurement of CD69 expression on NK cells with CD45RA, CD45RO, CD25 and CD69 expression on T cells resulted in a significant increase in at least two leucocyte activation markers from infected patients. In conclusion, this is the first report of the up-regulation of CD69 on NK cells as a sensitive marker of neonatal infection. A combination of this marker with CD45RA, CD45RO, CD25 and CD69 expression on peripheral blood derived T cells is the most sensitive and specific for neonatal infection.