Ontogeny of the immune response as a basis of childhood disease

The Long-term Effect of Bacille Calmette-Guérin Vaccination on Tuberculin Skin Testing: A 55-Year Follow-Up Study

BACKGROUND

Bacille Calmette-Guérin (BCG) vaccination is known to cause false-positive tuberculin skin test (TST) results from cross-reactions with mycobacterial antigens. However, the duration of BCG vaccination influence on the TST is poorly characterized. The objective of this study was to assess the long-term effect of BCG vaccination on TST reactivity.

METHODS

Data on TST reactivity were prospectively collected during 1935 to 1947 as part of a clinical trial among Native Americans/Alaskan Natives and were retrospectively collected thereafter between 1948 and 1998. TST induration of ≥ 10 mm was defined as a positive reaction. Kaplan-Meier analysis and multivariate Cox regression were used to compare the time to TST conversion and reversion between the BCG and placebo groups.

RESULTS

BCG vaccination after infancy was associated with an increased risk of TST reactivity in the first 15 years after vaccination (adjusted hazard ratio [HR], 2.33). This association remained during the interval 16 to 55 years after vaccination, although the effect was attenuated (adjusted HR, 1.26). Age at vaccination modestly impacted the effect of BCG on TST results in the first 15 years. Positive TST results among the BCG-vaccinated group were more likely to revert to negative results during the first 15 years but not in the latter period.

CONCLUSIONS

This study provides evidence that BCG vaccination after infancy may influence TST results beyond the 10-year period conventionally accepted by the Centers for Disease Control and Prevention (CDC), extending up to 55 years after vaccination. This suggests that BCG vaccination should be taken into account when interpreting TST results regardless of the time elapsed since vaccination.

Overview of Infections in the Immunocompromised Host

Understanding the components of the immune system that contribute to host defense against infection is key to recognizing infections that are more likely to occur in an immunocompromised patient. In this review, we discuss the integrated system of physical barriers and of innate and adaptive immunity that contributes to host defense. Specific defects in the components of this system that predispose to particular infections are presented. This is followed by a review of primary immunodeficiency diseases and secondary immunodeficiencies, the latter of which develop because of a specific illness or condition or are treatment-related. The effects of treatment for neoplasia, autoimmune diseases, solid organ and stem cell transplants on host defenses are reviewed and associated with susceptibility to particular infections. In conclusion, an approach to laboratory screening for a suspected immunodeficiency is presented. Knowledge of which host defects predispose to specific infections allows clinicians to prevent, diagnose, and manage infections in their immunocompromised patients most effectively.

Tuberculin skin test and ELISPOT/T. SPOT.TB in children and adolescents with juvenile idiopathic arthritis

BACKGROUND

There are controversies regarding the accuracy of the tuberculin skin test (TST) and methods based on the production of interferon gamma by sensitized T cells for the diagnosis of latent tuberculosis infection (LTBI) in pediatrics and immunosuppressed patients. Our objectives are to study TST and ELISPOT/T. SPOT.TB in the diagnosis of LTBI in children and adolescents with JIA undergoing methotrexate, the correlation between both and the sensitivity and specificity of T. SPOT.TB.

METHODS

This is an observational prospective longitudinal study in which children and adolescents with JIA undergoing methotrexate therapy were assessed for clinical and epidemiological data for LTBI, in addition to performing TST and T. SPOT.TB at baseline and after 3 and 12months.

RESULTS

There were 24 patients. The prevalence of LTBI at inclusion was 20.8%, the incidence after initiation of immunosuppressions 26.3% and the prevalence at the end of the study 41.6%. Epidemiological history positive for TB showed a relative risk of 2.0 for the development of LTBI. Only 2 patients had positive T. SPOT.TB but only in one it was useful for detecting early LTBI. T. SPOT.TB presented a sensitivity of 10%, specificity of 92.8%, and low correlation with TST. No patient developed TB disease at a mean follow-up of 47months.

CONCLUSIONS

We found a high prevalence of ILTB that doubled with immunosuppression and that epidemiological history was an important relative risk. T. SPOT.TB showed low sensitivity and high specificity, and no superiority over TST. There was low agreement and little influence of immunosuppression on the results of both tests.

Diversity of disease in childhood pulmonary tuberculosis

Many factors can influence the dynamic balance that exists between the host and the pathogen (M. tuberculosis), but the host immune response seems to be the most important. This is illustrated by the vulnerability of immune-compromised individuals to develop tuberculosis and by the age-related spectrum of disease witnessed in immune-competent children. This age-related spectrum of disease reflects the ontogeny of the host immune response towards M. tuberculosis. Renewing our focus on the ontogeny of the immune response in children might provide valuable insights to direct future research regarding tuberculosis prevention, vaccine development and treatment.

Systemic reduction of soluble complement receptor II/CD21 during pregnancy to levels reminiscent of autoimmune disease

Complement receptor type II/CD21 is the functional receptor for complement fragments such as C3d, iC3b and the Epstein Barr Virus. A soluble form of CD21 (sCD21) is shed from lymphocytes surface and is able to bind to its ligands found in the plasma. The amount of sCD21 in serum may modulate immunity as the plasma levels are correlated with autoimmune conditions, such as Systemic Lupus Erythematosus, Rheumatoid Arthritis and Sjoegren's Syndrome. Because of the fact that pregnancy may lead to remission of autoimmune diseases we determined the serum levels of sCD21 during pregnancy and postpartum. The serum sCD21 levels during pregnancy are significantly lower as compared to that of the healthy controls. There were no significant differences in sCD21 levels between the mother and the cord blood also immediately after parturition. Restoration of sCD21 levels to normal values takes between 6 weeks and 1 year after childbirth. Our study indicates that CD21-shedding is affected during pregnancy comparable to that of autoimmunity.

Exanthème maculo-papuleux néonatal révélateur d’une septicémie à Klebsiella pneumoniae par infection maternofœtale

BACKGROUND

Neonatal exanthema of bacterial origin is caused very rarely by Gram-negative bacilli. We report a case of neonatal maculopapular exanthema evocative of Klebsiella pneumoniae septicemia resulting from maternofetal infection.

OBSERVATION

On the fourth day of life, a newborn infant presented incipient morbilliform maculopapular exanthema on the face. During delivery, the mother had presented hyperthermia and meconium was found in the amniotic fluid. Clinical examination of the newborn was normal. No clinically obvious site of entry of infection was seen. Laboratory tests revealed major inflammatory syndrome. Blood cultures were positive for K. pneumoniae, which was also found in blood cultures from the mother. Screening for other causes of infection was negative. Parenteral antibiotics for 10 days yielded favorable results with simultaneous resolution of the exanthema, normalization of laboratory values and negative blood cultures.

DISCUSSION

Exanthemas of infectious origin are not associated with any specific organism. The most common causative micro-organisms are Listeria monocytogenes, B streptococci, colibacilli, and more rarely, staphylococci. There have been reports of a number of cases of neonatal septicemia due to Gram-negative bacilli responsible for maculopapular exanthemas but the causative organism was not identified. To our knowledge, Klebsiella pneumoniae has never been incriminated in the appearance of this type of rash via maternofetal transmission. Consequently, the presence of neonatal exanthema should prompt screening for sepsis, even in the absence of other evocative signs, and in particular in settings of apyrexia.

Follow-up of infants given measles vaccine at 6 months of age: antibody and CMI responses to MMRII at 15 months of age and antibody levels at 27 months of age

The worldwide elimination of measles is an important target. In developed countries, to control measles outbreaks, immunization from 6 months of age is recommended. In this study, infants (n = 290) who were (1) born to mothers with natural immunity or to vaccinated mothers and (2) previously immunized with Connaught (CLL) or AIK-C measles vaccine at 6 months of age, were evaluated for measles immunity before and after measles-mumps-rubella (MMRII at 15 months of age. Eight weeks after MMRII, 98.9% of infants were seropositive by enzyme immunoassay (EIA) and 70% demonstrated measles specific cellular immunity by blast transformation (BT) of lymphocytes. At 27 months of age, 98.4% of infants had protective antibody levels by plaque reduction neutralization (PRN) test. These results suggest that AIK-C and CLL vaccines elicit durable protective immunity in young infants when used in early immunization programs.

Novel microtechnique for assessment of postnatal maturation of the phagocytic function of neutrophils and monocytes

We describe a simple test for the evaluation of phagocytosis and provide a chart of reference values to evaluate normal phagocytosis by age. We assessed the postnatal maturation of phagocytic function of neutrophils and monocytes. Phagocytosis was evaluated in newborn children delivered vaginally or by cesarean section, infants, preschool children, schoolchildren, and adult subjects. Two drops of blood were placed on a microscope slide and incubated with Saccharomyces cerevisiae yeasts, and phagocytosis was evaluated by microscopy. Our technique showed results comparable to or better than those obtained by other usual techniques. The neutrophils of newborn children delivered by cesarean section showed a phagocytic capacity 45% higher than those of neonates delivered vaginally, whereas neutrophils from children in the latter group showed the lowest phagocytic capacity of all age groups. Phagocytosis by neutrophils reached the levels seen in adults at about the first year of life, while there were no important variations in phagocytosis by monocytes in the different age groups. The technique described is reliable and fast, uses only a few drops of blood, and allows better preservation of cell function due to the minimal manipulation to which the cells are submitted. The delayed maturation of the phagocytic function by neutrophils may account for the high levels of susceptibility of newborn and infant children to bacterial infections. This practical method of assessment of phagocytosis may allow the diagnosis of primary or secondary phagocytic deficiencies to be made more easily and may allow better monitoring and treatment of those with dysfunctions of these cells.

Deficient IgA and IgG2 anti-pneumococcal antibody levels and response to vaccination in otitis prone children

OBJECTIVE

To evaluate the isotype and IgG subclass distribution of anti-pneumococcal antibodies and response to polysaccharide vaccination in otitis prone children.

METHODS

IgG1, IgG2 and IgA antibodies to pneumococcal serotypes 3, 4, 6B, 9V, 14, 19F and 23F were determined in otitis prone children and in an age-matched healthy control population. Patients were immunized with a 23-valent pneumococcal polysaccharide vaccine. The antibody response was measured 4 weeks later.

RESULTS

Geometric mean IgA and IgG2 antibody levels for all seven pneumococcal serotypes tested were significantly lower in otitis prone children than in the control population. After immunization, there was no significant increase in geometric mean IgG2 anti-serotype 6B, 19F and 23F pneumococcal polysaccharide (weak immunogenic), but also no increase for IgG2 anti-serotype 4 and 14. Post immunization IgG2 antibody titers for serotypes 6B, 9V and 19F even remained below titers of non-vaccinated controls. Nine out of 29 otitis prone children were colonized nasopharyngeally with Streptococcus pneumoniae during the time of vaccination; these children had an even more severely impaired systemic antibody response.

CONCLUSIONS

Otitis prone children, while having normal IgG1 antibody levels, have low IgG2 and IgA anti-polysaccharide antibody levels and fail to respond in these subclasses upon vaccination with pneumococcal polysaccharide vaccine.

The nasopharynx and the middle ear. Inflammatory reactions in middle ear disease

The host-parasite interactions in the nasopharynx with bacterial colonization and antigen uptake in the lymphoid tissue, the adenoid, has an impact on the maturation of local and systemic immunity. The adenoid is a part of mucosa associated lymphoid tissue and is responsible for both effector and inductor functions in the nasopharynx. Increasing evidence supports the role of serum antibody in protecting the middle ear cavity from disease. There is evidence for a minor immunologic defect in a number of children with recurrent episodes of AOM.

Correlation of susceptibility of immature mice to fungal infection (blastomycosis) and effector cell function

Immature mice are highly susceptible to blastomycosis, which is similar to other mycoses and has parallels in humans. The murine susceptibility is noteworthy in that it persists beyond the development of resistance to other, nonfungal pathogens and the maturation of most immune functions. As the susceptibility to blastomycosis appeared to be related to an early event after infection, primary effector cell function was studied. We found that peritoneal inflammatory cells, enriched for neutrophils, from immature (3-week-old) mice killed nonphagocytizable Blastomyces dermatitidis cells less (25%) than did cells from mature (8-week) mice (70%) (P<0.01), a defect intrinsic to the neutrophils. This correlated with an impaired immature cell oxidative burst. Killing of phagocytizable Candida albicans was not significantly different, 73 versus 87%. Thioglycolate-elicited cells were more impaired; killing of B. dermatitidis was insignificant, and killing of C. albicans was more impaired in immature (16% killing) than in mature (45%) cells (P<0.02). Peripheral blood neutrophils from mature animals killed B. dermatitidis (41%) more than did those from immature animals (10%) (P<0.02); C. albicans was killed efficiently by both. Resting or activated peritoneal macrophages from both types of animals showed no differences in B. dermatitidis killing. These results suggest that the susceptibility of immature mice is related at least in part to the depressed capacity of their neutrophils to kill B. dermatitidis.

Activation of the gut-associated lymphoid tissue with expression of interleukin-2 receptors that peaks during weaning in the rat

BACKGROUND

Weaning exposes the intestinal mucosa to food and bacterial antigens at an age when the immune system is believed to be immature and functionally defective. The purpose of this study was to investigate changes in activation and phenotype of immune cells of the gut-associated lymphoid tissue during weaning.

METHODS

Litters of infant rats were studied from pre- to postweaned life. The activation status, assessed by interleukin-2 receptor (IL-2R) expression, and phenotype of cells in the gut-associated lymphoid tissue were examined by immunostaining.

RESULTS

Interleukin-2 receptor expression peaked two to four-fold at midweaning (day 21) in mesenteric lymph nodes, jejunal lamina propria, Peyer's patches, and intraepithelial lymphocytes, compared with adult animals (day 70). CD45+ cells expanded in the lamina propria, epithelium, and lymphocyte-filled villi. With CD45 as the denominator, 10% to 50% of lymphocytes in the lamina propria and epithelium were alphabetaT-cell receptor (TCR)+, but the remaining cells had a null phenotype, because there were low numbers of gammadeltaTCR+ T cells, B cells, and macrophages. Natural killer cells peaked at midweaning in the lamina propria (9%) and epithelium (20%) but were less than 5% of CD45+ cells after weaning.

CONCLUSIONS

Rather than being immature or functionally inactive, the gut-associated lymphoid tissue reacts appropriately during weaning with expression of IL-2R and expansion of alphabetaTCR+ T-cells.

Tuberculin skin testing: determinants and reaction

Mantoux purified protein derivative (PPD) skin testing was performed in schoolchildren who were grouped according to positive (Group I, n = 205) and negative (Group II, n = 79) exposure to recent acid-fast bacilli (AFB) smear-positive tuberculosis (TB) family contact. A prospective case-control study was undertaken to evaluate whether repeat bacille Calmette-Guérin (BCG) vaccination, nutritional state, presence/absence of BCG scar, and degree of AFB positivity of sputum of adult TB cases affect PPD skin reactivity in these two groups. Group I with TB contacts had larger induration (13.00 +/- 11.29 mm) than the Group II control group of 4.52 +/- 6.20; P = 0.000. Purified protein derivative reaction as to the number of BCG vaccination(s) received showed an increase in size as the BCG vaccination is repeated with significantly larger induration in Group I than in Group II (P = 0.048). The nutritional status was subgrouped into A (weight < 10 percentile), B (weight 50-75 percentile), and C (weight > 90 percentile), which were comparable for both groups. The mean PPD induration of subgroup A in Groups I and II was not statistically different. However, the mean PPD induration was highly significant between Groups I and II in subgroup B (12.46 +/- 10.70 vs 3.80 +/- 5.71 mm; P = 0.000) and subgroup C (14.31 +/- 11.54 vs 5.42 +/- 6.70 mm; P = 0.000). Children in group I with the BCG scar were noted to have significantly greater PPD induration size than in group II (14.14 +/- 11.23 vs 5.05 +/- 6.24 mm; P = 0.000). The degree of AFB positivity of sputum of TB adult cases (1+ to 4+ and cavitary TB) has no effect on PPD size (P = 0.766). Close contact with individuals with active TB (AFB smear positive) is a very important factor for PPD skin conversion. Repeat BCG vaccination, malnutrition, and BCG with scars present difficulties in making a diagnosis of TB infection but did not affect PPD reactivity and did highlight the need for thorough clinical evaluation.

Haemophilus influenzae Type b Polysaccharides-Protein Conjugate Vaccine Elicits a More Diverse Antibody Repertoire in Infants Than in Adults

Conjugation of bacterial polysaccharides (PS) to protein carriers confers the ability to elicit protective serum Ab in infants, who respond poorly to plain PS. The serum Ab of young children immunized with Haemophilus influenzae type b (Hib) PS conjugate vaccine varies with age and Ag formulation. To understand these age-related changes in human anti-Hib PS immune responses we determined the variable region gene sequences encoding anti-Hib PS mAbs of infants immunized with Hib oligosaccharide-diphtheria toxin vaccine. The anti-Hib PS repertoire of children differs from that of adults. A smaller proportion of mAbs from children have high affinity for Hib PS, and the overall variable region gene repertoire of infants is more diverse than that in adults. Variable region genes encoding high affinity mAbs of infants are similar to the restricted repertoire described in adults. Low affinity anti-Hib PS mAbs of infants are encoded by a heterogeneous group of genes that are uncommonly observed in the adult repertoire. Abs with high affinity for Hib PS from infants, like most mAbs from adults, react only with Hib PS and the structurally similar PS of Escherichia coli K100, whereas low affinity mAbs of infants are polyreactive. The low affinity anti-Hib PS mAbs of infants immunized with Hib oligosaccharide-diphtheria toxin vaccine vaccine are not reflected in serum Ab. However, the differences between the variable region gene repertoires of adults and infants may account for the distinct immunologic characteristics of the anti-Hib PS responses in young children immunized with other vaccine formulations.

Infant B cell responses to polysaccharide determinants

Newborns and infants up to the age of 1.5-2 years of age are unable to produce antibodies to bacterial capsular polysaccharides. As a consequence, children up to the age of 2 years have an increased susceptibility for infections with encapsulated bacteria. Capsular polysaccharides are classified as so-called T cell independent type 2 antigens and induce IgG2 antibodies. The mechanism of B lymphocyte activation by polysaccharides differs from that of protein antigens and involves co-stimulation by CD21 (type 2 complement receptor). Reduced expression of CD21 on neonatal B lymphocytes can explain unresponsiveness to polysaccharides. Polysaccharide protein conjugates have the ability to overcome unresponsiveness to polysaccharides early in life. The response induced is predominant IgGl.

Characterization of early activation events in cord blood B cells after stimulation with T cell-independent activators

Human neonates are immunologically immature, particularly in their humoral antibody responses to T cell-independent antigens, as exemplified by their increased susceptibility to infections with polysaccharide-encapsulated bacteria. To clarify the mechanism(s) underlying the unresponsiveness of neonates to polysaccharide antigens, we used an in vitro model with neonatal cord blood cells that has been shown to mimic surface Ig-dependent signaling in the adult by T cell-independent antigens. We studied the ability of cord blood human B cells to become activated after ligation of their surface Ig by unconjugated anti-Ig, dextran-conjugated anti-Ig, and Staphylococcus aureus Cowan A1, and compared their response with that of adult B cells. After the addition of nanogram concentrations of anti-Ig-dextran, neonatal cord blood B cells proliferated at levels comparable to that observed with adult B cells. The majority of cord blood B cells showed a marked rise in intracellular calcium, increased surface expression of human leukocyte antigen DR, and an increase in cell size. Direct activation of protein kinase C by phorbol esters in neonatal B cells led to cellular proliferation, and when combined with anti-Ig, a synergistic effect on proliferation was observed. These data suggest that the unresponsiveness of human neonates to polysaccharide antigens does not represent an inability of these antigens to induce early activation events in circulating B cells.

Postnatal changes in mucosal immune response: a physiological perspective of breast feeding and weaning

There are profound changes of immune activity during infancy from suppression during breast feeding, activation with weaning, and later intrinsic down-regulation after weaning. Breast feeding, as well as protecting against infections, seems to have a fundamental role in modifying the immune system against certain disease states. Transforming growth factor (TGF)beta in breast milk may mediate this immunosuppressive effect. Although the infant immune system is not in an adult state, the notion that the infant immune system is immature is difficult to reconcile with evidence that most infants respond appropriately to immunization and to infections. The systemic immune system of neonates may be subject to Th2 immune deviation, while the mucosal immune system, particularly of the gastrointestinal tract and probably the respiratory tract, is up-regulated with physiological inflammation during infancy. Weaning is associated with a peak of intestinal immune activation which includes mucosal mast cells and T cells. The physiological effects of this activation are promotion of epithelial growth of the small intestine and initial activation of mechanisms leading to subsequent down-regulation of the physiological heightened immune activity. This coincides with the development of mucosal (oral) tolerance to food and bacterial antigens.

Salmonella meningitis: clinical experience of third-generation cephalosporins

Fifteen paediatric patients with Salmonella meningitis were retrospectively reviewed. Presenting symptoms and signs included fever, vomiting, seizures, poor activity, diarrhoea and bulging anterior fontanelle in most patients. Seven out of eight patients with prolonged fever for > 10 days had neurologic sequelae; therefore, prolonged fever is a significant prognostic factor of a poor outcome (p < 0.005). All 15 patients had a brain ultrasound or computed tomography in the acute stage and 11 patients had abnormal findings. The 14 surviving patients were treated with a third-generation cephalosporin for at least 3 weeks. Seven patients (47%) made complete recoveries; two of them were treated solely with a third-generation cephalosporin. Only one mortality (6%) occurred and there were no relapses. In conclusion, high frequencies of prolonged fever, neuroimaging abnormalities and neurologic sequelae were seen in patients with Salmonella meningitis treated with third-generation cephalosporins.

Role of interleukin-2 and interferon-gamma in inducing production of IgG subclasses in lymphocytes of human newborns

Unlike lymphocytes from adults, lymphocytes from cord blood of neonates cannot synthesize immunoglobulin G (IgG) in response to pokeweed mitogen (PWM). By using this mitogen in concert with interferon-gamma (IFN-gamma), interleukin-2 (IL-2), or interleukin-6 (IL-6), we studied the induction of IgG subclass molecules in lymphocytes of human neonates. IFN-gamma induced a limited, but substantial, enhancement of IgG2 production by neonatal lymphocytes. IL-2 dose dependently increased the production of each neonatal IgG subclass, whereas IL-6 did not. However, in adult lymphocytes, and under specific conditions, IL-6 or IL-2 each increased the production of all four IgG subclasses. Early in the culture IFN-gamma synergized with IL-2 during the latter or whole culture period to enhance cord blood IgG2 levels. This finding contrasted with the adult IgG2 synthesis synergistically up-regulated by IFN-gamma and IL-6. IL-2 caused a graded increase in immunoglobulin production in neonatal lymphocytes with IgG3 being the highest and IgG2 the lowest, thus corresponding to the differential increase of serum levels of IgG3/IgG1 and IgG4/IgG2 early in childhood. Results suggest that IL-2, but not IL-6, is critical to the development of human IgG subclass production.

Mycobacterial infections: are the observed enigmas and paradoxes explained by immunosuppression and immunodeficiency?

The enigmas and paradoxes observed in tuberculous patients, in Bacille Calmette-Guérin-vaccinated people and in Bacille Calmette-Guérin-treated cancer patients have been examined, in an attempt to explain them through the mechanisms of immunodeficiency and immunosuppression. A dual effect is postulated: an immunosuppression induced by the infecting mycobacteria that adds to a pre-existing or emerging state of immunodeficiency of the infected individual. The immunological cellular and humoral anergies observed at the beginning of a tuberculous therapy are usually lifted after the first two weeks of treatment. This restoration of immune responsiveness may be attributed to the destruction or to the growth inhibition of immunosuppressive mycobacteria. The observation that drugs cytocidal in vitro do not always sterilize the patients under treatment whereas bacteriostatic drugs do, may find an explanation in the dual immunosuppression induced by cytocidal drugs and mycobacteria. The fact that Bacille Calmette-Guérin applied as an immunotherapy to residual cancer has either a favorable or an unfavorable action may be due to the immunosuppressive activity attached to some Bacille Calmette-Guérin strains and to some cancers. The variable protective activity of Bacille Calmette-Guérin vaccines may be due to the immunological status of the vaccinated people and the compositional differences between strains. The protective activity of subunit vaccines in experimental models can be attributed to the elimination of immunosuppressive factors present in whole killed mycobacteria.

Characteristics of immune responses to native and protein conjugated pneumococcal polysaccharide type 14

The immune response to pneumococcal polysaccharide type 14 (PPS-14), induced by native PPS-14 was compared with the response induced by PPS-14 conjugated with CRM197 (PPS-14-CRM197). In our animal model, immunization with PPS-14-CRM197 gave a significant enhancement of anti-PPS-14 serum titres for IgM and IgG, but not for IgA. Also an increase in total number of anti-PPS-14 antibody-secreting cells was found. Using immunohistochemical techniques, a different distribution pattern of specific antibody-containing cells in spleen section after immunization with PPS-14-CRM197 was observed. Furthermore, a higher number of IFN-gamma producing cells was found after immunization with PPS-14-CRM197, as compared with immunization with PPS-14. This enhanced IFN-gamma production may be the cause for enhanced IgG response observed after immunization with PPS-14-CRM197. The specific immune response was less affected by splenectomy in animals immunized with PPS-14-CRM197 than with PPS-14. However, an age-related response to the native as well as the conjugated form of the PPS-14 was observed, since no effect of conjugation with CRM197 was seen in the onset of the immune response to PPS-14 in young animals. In conclusion, our results affirm the hypothesis that conjugation of polysaccharides changes the characteristics of the antigen towards a thymus-dependent antigen.

Changes in the concentration and distribution of immunoglobulin-producing cells in SIDS palatine tonsils

Seventeen sudden infant death syndrome (SIDS) cases and 9 controls, were examined immunohistochemically with regard to the presence of IgA-, IgM-, IgD, and IgG, as well as for the subtypes IgG1-, IgG2-, IgG3-, and IgG4-immunocytes. Differences in compartmentalization were also investigated. Differences were demonstrated between SIDS and controls in total number of IgG cells per 0.1 mm2 tissue area (median: 18.3, range: 12.3-30.2 versus median: 6.3, range: 2.0-14.6) (p < 0.01), and for IgA immunocytes (median: 3.9, range: 2.4-5.0 versus median: 1.5, range: 1.1-3.7) (p < 0.05), while no differences were demonstrated for IgM cells (median: 1.8, range: 1.2-3.3 versus median: 1.8, range: 0.7-5.6) or IgD cells (median: 1.9, range: 0.8-2.9 versus median: 1.6, range: 0.7-2.4). Differences were demonstrated between SIDS and control IgG plasma cells in all the four palatine tonsillar compartments; germinal centre (p < 0.01), mantle zone (p < 0.05), interfollicular area (p < 0.01) and reticular epithelium (p < 0.01). Furthermore, the number of IgA cells was higher in SIDS vs. controls in both the germinal centre (median: 1.4, range: 0.6-2.1 versus median: 0.6, range: 0.3-1.3) (p < 0.05) and in the interfollicular area (median: 2.2, range: 1.1-3.1 versus median: 0.5, range: 0.4-2.0) (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

The value of quantitative measurement of HBeAg and HBsAg before interferon-alpha treatment of chronic hepatitis B in children

Serum concentrations of HBsAg, HBeAg and hepatitis B virus DNA were measured quantitatively before interferon treatment in 23 children (17 boys, 6 girls) suffering from chronic hepatitis B, and correlated to the outcome of the treatment. Five children remained HBsAg- and HBeAg-positive throughout the treatment and 6 months after the end of the treatment (non-responders), 12 children eliminated HBeAg but not HBsAg (partial responders) and six eliminated HBeAg and HBsAg (complete responders). The five non-responders had significantly higher initial HBsAg and HBeAg concentrations and significantly lower alanine aminotransferase levels than the partial or complete responders. The six complete responders had significantly lower HBsAg concentrations than the partial or non-responders, and seemed to be younger. No significant difference in HBV DNA levels was found in the three response groups. These data suggest that quantitative assays of HBsAg and HBeAg are particularly useful in selecting patients with chronic hepatitis B for interferon therapy.

The K1 capsule is the critical determinant in the development of Escherichia coli meningitis in the rat

Although Escherichia coli strains possessing the K1 capsule are predominant among isolates from neonatal E. coli meningitis and most of these K1 isolates are associated with a limited number of 0 lipopolysaccharide (LPS) types, the basis of this association of K1 and certain 0 antigens with neonatal E. coli meningitis is not clear. The present study examined in experimental E. coli bacteremia and meningitis in newborn and adult rats whether or not the K1 capsule and/or O-LPS antigen are critical determinants in the development of meningitis. Rats received subcutaneously at K1 E. coli strain (018+K1+) or mutants lacking either the K1 capsule (018+K1-) or 0 side-chain (018-K1+). 12-24 h later, blood and cerebrospinal fluid (CSF) specimens were obtained for quantitative cultures. The isolation of E. coli from CSF was observed in both newborn and adult rats infected with K1+ strains regardless of LPS phenotype (018+ or 18-) who also developed a high degree of bacteremia (e.g., greater than 10(4) CFU/ml of blood). In contrast, none of the newborn and adult rats infected with 018+K1- and developing bacteremia of greater than 10(4) were found to have positive CSF cultures. These findings indicate that the presence of the K1 capsule and a high degree of bacteremia are key determinants in the development of E. coli meningitis, suggesting that there may be specific binding sites present in the brain which have an affinity for the K1 capsule and thus may be responsible for the entry of K1-encapsulated E. coli into the meninges.

Effect of bacille Calmette-Guérin vaccination on tuberculin reactivity

The effect on tuberculin reactivity of bacille Calmette-Guérin vaccination (BCG-V) given 10 to 25 yr earlier was measured among schoolchildren and young adults in Montreal. Of a total eligible population of 8,264 persons, 5,952 were tuberculin tested (72%). The BCG-V status could be verified for 4,629 of 4,969 (93%) participants born in Quebec. Of these, 1,511 (33%) had received BCG-V, 66% of whom had been vaccinated once only in infancy, 23% of whom had been vaccinated once but after infancy, and 11% of whom had been vaccinated twice. Among those vaccinated in infancy, 7.9% had significant tuberculin reactions, compared with 18% among those vaccinated between 1 and 5 yr of age, and 25.4% among those vaccinated after the age of 5 (p less than 0.001). Among those receiving BCG-V in infancy, the prevalence of tuberculin reactions of 10 mm was similar to the nonvaccinated subjects, after accounting for differences in age and socioeconomic status. Among those vaccinated after infancy, tuberculin reactivity was not significantly affected by interval from BCG-V until tuberculin testing nor by repeat BCG-V. We conclude that after an interval of 10 to 25 yr the most important determinant of effect of BCG-V on tuberculin reactivity is age when vaccinated. A significant tuberculin reaction among those who have received BCG-V should be interpreted in light of the age when vaccinated and the expected prevalence of tuberculous infection in the population tested.

The human antibody V region repertoire to the type B capsular polysaccharide of Haemophilus influenzae

The V region repertoire of the human antibody response to the type b capsular polysaccharide of Haemophilus influenzae (Hib-PS) is being defined at the molecular level using antibodies purified from serum of immunized adults. The VH of this response is restricted to the VHIII subgroup while the VL can be divided into two categories. The most common VL, expressed in > 90% of adults and usually constituting the majority of a subjects anti-Hib-PS antibody response, is restricted to the product of a single V kappa II gene known as A2 that probably lacks somatic mutations. The product of the A2 gene is invariably joined to one of several J kappa products by an inserted arginine at the V kappa-J kappa junction. In contrast to the restricted nature of the dominant VL clonotype, the second category of VL constitutes a heterogeneous group of at least seven different VL gene products that often contain somatic mutations and generally exhibit crossreactivity with a related polysaccharide from E. coli. Elucidation of anti-Hib-PS V regions at the molecular level will permit examination of structure-function relationships among these clinically important antibodies and should make the V region repertoire to Hib-PS a useful model for studying human V gene responses.

Paediatric oncology in developing countries

Paediatric oncology in developing countries is a specialty in its own right that has so far been largely neglected by the western medical profession. It has specific features of genetic cancer predisposition and of external factors influencing phenotypic cancer manifestations. We point out here some of the specific features of cancer presentation in children of developing countries.

Cystic fibrosis. Infection and immunity to Pseudomonas

Chronic pulmonary infection with P. aeruginosa in CF may result from: 1. An initial failure of clearance mechanisms (increased adherence) leading to the development of a highly compartmentalized inflammatory reaction; 2. Inhibition of clearing mechanisms for bacteria present in the bronchial lumen; and 3. A largely ineffective, and possibly damaging, hyperactivity of inflammatory cells in the lumen and bronchial wall. The special relationship between the CF host and P. aeruginos, always long-term, and frequently subtle in its complexity, needs further understanding in order to develop new strategies for the treatment of chronic lung infections with this organism.

Food and drug reactions, wheezing, and eczema in preterm infants

Allergic reactions were investigated in 777 preterm infants who were randomly assigned to early diet and followed up to 18 months post term. Wheezing or asthma was common (incidence 23%); it was associated with neonatal ventilation, maternal smoking, and a family history of atopy and was unexpectedly reduced in babies born by caesarean section. Even in non-ventilated infants, the incidence of subsequent wheezing was 18%, rising to an estimated 44% (using logistic regression) when the foregoing risk factors (excluding ventilation) were present. Eczema occurred in 151 infants (19%) and was strongly associated with multiple pregnancy (30% incidence in twins or triplets). Reactions to cows' milk (incidence: 4.4% from detailed history; 0.8% confirmed by challenge), other foods (10%), and drugs (5%) were within the range reported in full term infants. Milk and food reactions were associated with multiple pregnancy (19%) and a family history of atopy. Reactions to drugs were least likely to occur in infants who had been ventilated and were on multiple medications in the neonatal period, suggesting that drug tolerance may have developed. We speculate that preterm infants may be a high risk group for asthma and eczema, which could imply an association between atopy and prematurity.

Quantification of nasopharyngeal bacteria for diagnosis of respiratory tract infection in children

Agreement between clinical signs of bacterial respiratory tract infections and quantities of respiratory tract pathogens in nasopharynx was studied in 77 children, aged 6-13 years. Specimens were obtained from 27 clinically bacterial and 51 clinically non-bacterial respiratory tract infections, and in 124 instances from healthy children. Viable counts of Streptococcus pneumoniae, Haemophilus influenzae, Branhamella catarrhalis, and beta-haemolytic streptococci were made from swab specimens suspended in saline before being plated on agar media. The frequency of these species in children with clinically bacterial, non-bacterial and no signs of respiratory tract infections were 85%, 47% and 26%, respectively. Bacterial counts greater than 10(4) colony-forming units (CFU)/ml of the pathogens occurred in 59% of clinically bacterial infections, as compared with 18% in clinically non-bacterial infections (p less than 0.001), the corresponding figures for counts greater than 10(3) CFU/ml being 85% and 41% (p less than 0.01), respectively. At neither level of bacterial count (i.e. greater than 10(4) or greater than 10(3], was there a significant difference between the healthy and those with a clinically non-bacterial infection. The quantification of bacteria in nasopharyngeal samples may thus be of clinical diagnostic value.

Prospective trial of timing of bacillus Calmette-Guérin vaccination in Canadian Cree infants

We studied 184 Cree Indian infants in randomized, prospective fashion to assess the effect of age on lymphocyte sensitization to purified protein derivative (PPD) before and after and without bacillus Calmette-Guérin (BCG) vaccination. Lymphocyte responses to PPD, Candida, and streptokinase were measured at birth and at intervals later. The mean response of paired values from 26 infants without BCG vaccination rose for the PPD stimulation index (SI) from 2.7 at birth to 3.9 before 2 yr of age. The SI for both Candida and streptokinase for this group of infants rose significantly in the first 2 yr (p less than 0.05). In 66 infants who received BCG in the first 7 days of life, the PPD-SI rose from 3.1 to 35.3 (p less than 0.001). In 17 infants who received the vaccine later but before 9 months, it rose from 3.1 at birth to 24.9, and in 14 who received it between 9 months and 2 yr, it rose from 2.2 to 52.9. The lymphocyte responses to PPD after BCG in these two groups were significantly different (p less than 0.05). There was no evidence in the older infants that a raised PPD-SI before BCG vaccination affected lymphocyte sensitization by the vaccine. We conclude that increasing the age at vaccination with BCG from birth to more than 9 months enhances immunologic sensitization to PPD significantly in this population.

Incidence of acute otitis media up to the age of 1 1/2 years in urban infants

The object of this prospective cohort investigation of 1,642 infants was to study the incidence of acute otitis media (AOM) in urban children during the first 18 months of life. The monthly incidence of AOM was greatest at the age of 10 months, and the largest proportion of children with AOM was also found in this 10-month age group. Before the age of 18 months, 56.7% of the infants had had at least one episode of AOM, while 26.9% had had one or two episodes and 29.8% three or more. The corresponding figures before the age of 12 months were: 45.3%; 26.8%; 18.5%, and before the age of 9 months: 30.5%; 22.1%; 8.4%. The AOM incidence, particularly as regards recurrent AOM, was rather higher in boys than in girls.

The in vitro B-cell response to pneumococcal polysaccharides in adults and neonates

In order to gain insight into the relatively late appearance in ontogeny of responsiveness to T-cell independent (TI) antigens, the in vitro human B-cell response to type 4 pneumococcal polysaccharides (PS4, a human TI-2 antigen) was studied. B cells obtained from adults differentiate into anti-PS4 antibody forming cells upon culturing with PS4, but neonatal B cells obtained from cord blood fail to respond. The culture system used does, however, allow the differentiation of B cells reactive with TD antigens, for example ovalbumin. In order to evaluate the concept that in man the anti-PS4 response is derived from a particular B-cell subset we separated adult B cells on the basis of expression of the determinant recognized by the monoclonal antibody FMC7. The anti-PS4 response is found mainly, but not exclusively, in the FMC7+ subset. The selective unresponsiveness of neonatal B cells to TI-2 antigens is not, however, due to the absence of FMC7+ B cells because, unlike adult blood B cells of which about 50% are FMC7+, 100% of neonatal B cells are FMC7+.

Differential immunoglobulin G subclass antibody titers to respiratory syncytial virus F and G glycoproteins in adults

Two respiratory syncytial virus glycoproteins, F and G, which differ substantially in the amount of glycosylation were used as antigens in an enzyme-linked immunosorbent assay to determine immunoglobulin G (IgG) subclass titers in 30 experimentally infected healthy adults. The titers of antibodies to the F glycoprotein achieved in postinfection sera were highest in the IgG1 subclass, whereas those to the G glycoprotein were highest and comparable in the IgG1 and IgG2 subclasses. The high IgG2 response to the G glycoprotein suggests that it is seen by the immune system as a polysaccharide antigen, a hypothesis consistent with its large carbohydrate content.

Hypergammaglobulinemia in cystic fibrosis. Role of Pseudomonas endobronchial infection

Hypergammaglobulinemia, chronic endobronchial infection with Pseudomonas aeruginosa (PA), and the resulting systemic humoral immune response to PA are each associated with worsened clinical status and prognosis in patients with cystic fibrosis (CF). Major serum immunoglobulin isotype levels (IgG, IgA, IgM, and IgG1-4 subclasses) were measured in 31 CF patients and ten control subjects. Immunoglobulin levels were related to airway infection with PA and the resulting IgG antibody response against PA lipopolysaccharide (LPS). Hyperimmunoglobulinemia G was present with elevated IgG1 and IgG2 in 48 percent, IgG3 in 52 percent, and IgG4 in 42 percent of CF patients. The PA infection was associated with striking increases in IgG2. IgG2 levels correlated well with IgG2 antibodies to PA LPS (r = +0.70, p less than 0.001). However, even CF patients who were not infected with PA had an increased prevalence of high IgG3 (p less than 0.05) and IgG4 (p less than 0.01). The PA infection thus appears to be a major, but not the only factor causing hypergammaglobulinemia in CF.

Decreased production of specific antibodies to cow's milk proteins in premature infants during the first six months of life

Concentrations of IgG and IgM antibodies to casein, beta-lactoglobulin, lactalbumin and bovine serum albumin (BSA) in sera of premature infants of less than 36 weeks gestation, at 5 weeks of age, were less than in age-matched term infants. At 6 months of age IgG antibodies to BSA in preterms were still significantly lower than in term infants.

Serum immunoglobulin G antibody subclass responses to respiratory syncytial virus F and G glycoproteins after primary infection

Because the immunoglobulin G (IgG) response to carbohydrate antigens is typically from the IgG2 subclass and the IgG response to protein antigens is typically from the IgG1 and sometimes the IgG3 subclass, two respiratory syncytial virus glycoproteins, F and G, which differ substantially in the amount of glycosylation, were used as antigens in an enzyme-linked immunosorbent assay to determine IgG subclass responses in 20 infants and young children with naturally acquired respiratory syncytial virus infection. Both glycoproteins elicited primarily IgG1 and IgG3 responses, indicating that the protein moieties of the glycoproteins may be immunodominant in this age group.

Recurrent acute otitis media--prophylactic penicillin treatment: a prospective study. Part I

Recurrent acute otitis media (RAOM) is a distressing clinical manifestation of middle ear pathology, mainly expressed in the first two years of life. In this controlled study, prophylactic treatment by phenoxymethyl penicillin reduced significantly the frequency of RAOM in 60 children, as compared to 48 children who received a short ampicillin course only on the occasion of an acute otitis media episode. The importance of breastfeeding, age at initial episode, the type of treatment given and the pertinent literature is discussed. A working hypothesis of this prophylactic treatment is suggested.

Antibodies to O-antigen of lipopolysaccharide are protective against neonatal infection with Escherichia coli K1

Monoclonal IgM specific for the O18 antigen conferred passive protection to 1-week-old rats against bacteremia and killing after oral challenge with O18:K1 Escherichia coli. Specific protection of the pups was also achieved by immunizing the pregnant rats with purified O18 lipopolysaccharide. We suppose that most human newborns that are colonized by potentially invasive K1 E. coli are protected by the transplacental transfer of anti-lipopolysaccharide immunoglobulin G, and we suggest that treatment with such antibodies might in the future be considered a therapeutic option. Rat serum from 1-week-old animals had only about one-third of the complement hemolytic activity of adult rat serum. This low level of hemolytic activity correlated with a relatively poor bactericidal activity in antibody-dependent and antibody-independent bactericidal in vitro assays. Monoclonal anti-O18 immunoglobulin M, although protective in vivo and bactericidal when added to adult rat serum, only poorly inhibited the multiplication of O18:K1 cells in serum from 1-week-old rats. This suggests that other elements of host defense besides complement participate in antibody-mediated in vivo protection.

Altered T cell subsets and function in polytransfused beta-thalassemia patients: correlation with sex and age at first transfusion

Monoclonal antibodies (OKT series) have been used to investigate possible modifications of T lymphocytes and T lymphocyte subsets in 65 multiply transfused beta-thalassemia patients. No significant difference was observed in percentage and absolute number of OKT3-, OKT4-, and OKT8-positive cells when compared to controls. A subgroup of patients (10 patients, 15.3%), however, could be selected who showed a reversal of OKT4/OKT8 ratio. These patients did not differ from the others as to age, number of transfusions, frequency of splenectomy, ferritin levels, hepatitis B markers, chronic liver disease incidence, and numbers of B lymphocytes and natural killer cells. The features distinguishing this group from the remaining patients were: decreased mitogen responsiveness; early age when first transfused; high incidence of males (90%). Immunological investigation was done in 2 occasions, 1 year apart, but no significant modification was observed in these patients. These findings suggest that in beta-thalassemia patients transfusion therapy started very early in life may be responsible for persistent immunological modifications. The susceptibility to such modifications might be greater in males.

A prospective study demonstrating an association between plasma IgG2 concentrations and susceptibility to otitis media in children

Plasma IgG subclass levels of 20 children, 12 and 32 months of age, who were susceptible to acute purulent otitis media, were compared with those of 20 age-matched control children. The IgG2 levels were significantly lower in the otitis-prone group, with a mean of 0.58 +/- 0.30 g/l at 12 months of age (controls 0.85 +/- 0.39) and 0.82 +/- 0.30 at 32 months of age (controls 1.38 +/- 0.49). Otitis-prone children with IgG2 levels less than or equal to 0.58 g/l (at 12 months of age) were found to suffer from Haemophilus influenzae infections 2.6 times as often as those with IgG2 levels greater than 0.58 g/l. On the other hand pneumococci were found 1.9 times as often in the group with IgG2 level greater than 0.58 g/l, as in the group with IgG2 level less than or equal to 0.58 g/l. Otitis proneness seems partly to be due to an immunological incompetence of IgG2, which also influences the bacterial spectrum of the infections.

Interaction of multiple risk factors in the pathogenesis of experimental reflux nephropathy in the pig

The importance of several pathogenetic factors in the development of reflux nephropathy was evaluated in 25 piglets with complete unilateral vesicoureteral reflux and urinary tract infection. Three independent risk factors were studied: roentgenographic intrarenal reflux, P-fimbriation of the bacterial strain, absence of previous immunization. E. coli with P-fimbriae produce mannose-resistant agglutination of pig red blood cells and are more adherent to pig uroepithelial cells than E. coli without P-fimbriae. Vesicoureteral reflux was surgically induced at 2 weeks, urinary tract infection introduced at 6 weeks and the animals killed at 12 weeks of age. Independently, the 3 risk factors had a borderline or insignificant effect on renal scarring. Animals with none or only 1 risk factor, however, had significantly less scarring, fewer glomerular lesions and lower serum creatinines than those with 2 or 3 factors present. Several independent pathogenetic factors seem to have a synergistic effect on the development of reflux nephropathy.

Antigen-induced plaque-forming cell responses in cultures of peripheral blood mononuclear cells of human neonates and infants

Human cord blood mononuclear cells (CBMC) were stimulated in vitro with a number of T cell-dependent antigens. Antigen-induced B cell activation was measured applying a plaque-forming cell assay for the detection of antigen-specific IgM-secreting B cells. With the exception of diphtheria toxoid, the antigens ovalbumin, sheep red blood cells, Helix pomatia hemocyanin, burro red blood cells, and tetanus toxoid elicited an IgM-plaque-forming cell response in cultures of CBMC to levels obtained for peripheral blood mononuclear cells (PBMC) from adult controls. However, for each antigen used, the antigen dose optimal for the induction of a response was consistently found to be a hundred to a thousand times lower than the concentration of the corresponding antigen optimal for adult PBMC. Longitudinal studies on PBMC obtained from infants between 2 and 30 months of age revealed that a shift of the antigen dose toward concentrations needed to induce plaque-forming cells in cultures of adult PBMC occurs at approximately age 8 months. Our data indicate that various antigens can be used for the in vitro analysis of antigen-specific B cell activation and regulatory T cell functions in studies concerning the ontogeny of the humoral immune response in humans.

Do children with recurrent Haemophilus influenzae otitis media become infected with a new organism or reacquire the original strain?

Using the techniques of outer membrane protein gel analysis and biotyping, we characterized nontypable Haemophilus influenzae isolates from middle ear aspirates of 30 children with recurrent nontypable H, influenzae (NTHI) otitis media. Nine of the 13 children with early recurrence of NTHI otitis (less than 30-day intervals) had respective first and second isolates that were identical. In contrast, 14 of 18 children with late recurrences of NTHI otitis (greater than 30-day intervals) had respective first and second isolates that were different, whereas four children had late recurrences with organisms that appeared to be identical with their respective initial infecting strains. These results suggest that early recurrent NTHI otitis usually is a result of relapse with the initial infecting NTHI strain. In contrast, late recurrent disease is usually the result of infection with a new organism. However, the observation that four children had late recurrences with the original strains suggests that strain-specific protective immunity may not uniformly develop after recovery from NTHI otitis.

Salmonella meningitis in infancy

Despite adequate treatment, mortality and morbidity were high among the 13 cases of Salmonella meningitis in this series. Chloramphenicol, being a bacteriostatic agent against Salmonella species, is not a suitable antibiotic for the treatment of Salmonella meningitis. Treatment for 4-6 weeks is recommended with use of an antibiotic capable of achieving an adequate bactericidal concentration in the cerebrospinal fluid such as moxalactam. Intraventricular antibiotic treatment should be considered if there is a delay in the eradication of the Salmonella organisms from the cerebrospinal fluid after starting treatment.