Teresa Lagergård

A placebo-controlled trial of a pertussis-toxoid vaccine.

BACKGROUND Although many whole-cell vaccines have been effective in preventing pertussis, these vaccines are difficult to standardize and can produce side effects. In Sweden, pertussis became endemic during the 1970s despite vaccination. Because of its limited efficacy, the Swedish-made whole-cell vaccine was withdrawn in 1979. METHODS To evaluate the efficacy of an acellular vaccine consisting of pertussis toxin inactivated by hydrogen peroxide (pertussis toxoid), we conducted a randomized, double-blind, placebo-controlled trial in Sweden. Infants were vaccinated with either diphtheria and tetanus toxoids alone (DT toxoids, 1726 infants) or diphtheria, tetanus, and pertussis toxoids (DTP toxoids, 1724 infants) at 3, 5, and 12 months of age. RESULTS There were no serious reactions. With the pertussis vaccine there were slightly more local reactions than with the DT toxoids alone, but the rates of postvaccination fever were the same. The main period of surveillance, which began 30 days after the third vaccination, continued for a median of 17.5 months. There were 312 cases of pertussis (72 in the DTP-toxoids group and 240 in the DT-toxoids group) that met the clinical criterion (paroxysmal cough lasting > or = 21 days) and laboratory criteria for pertussis as defined by the World Health Organization. The efficacy of this acellular vaccine was 71 percent (95 percent confidence interval, 63 to 78 percent). The recipients of DTP toxoids who had pertussis had cough of shorter duration than the recipients of DT toxoids, and fewer had whooping and vomiting. The vaccine efficacy after two doses was 55 percent (95 percent confidence interval, 12 to 78 percent), on the basis of 14 cases in the DTP-toxoids group and 31 in the DT-toxoids group that met the definition of the World Health Organization. CONCLUSIONS A pharmacologically inert, acellular pertussis-toxoid vaccine that is easily standardized is safe and confers substantial protection against pertussis.

Etiology of community-acquired pneumonia in children based on antibody responses to bacterial and viral antigens.

The serologic responses to bacterial and viral antigens were determined in paired serum samples from 336 children, ages 1 month to 15 years, with roentgenographically verified community-acquired pneumonia. Significant increases in antibodies against one agent were found in 40% and against two or more agents in 8% of the children. There were significant increases in antibodies against respiratory syncytial virus in 20%, viruses of the influenza-par ainfluenza group in 6% and adenovirus in 3%. A serologic response to one or more of the pneumococcal antigens used (type-specific capsular polysaccharide, C-polysaccharide and pneumolysin) was demonstrated in 13% of the patients. Ten percent of the children had significant increases in antibodies against Mycoplasma pneumoniae. Only three patients had increases against Haemophilus influenzae type b and one each against Legionella pneumophila and Chlamydia. Respiratory syncytial virus was the predominant etiologic agent in young children whereas M. pneumoniae was more frequent in the older age group.

Correlation between Pertussis Toxin IgG Antibodies in Postvaccination Sera and Subsequent Protection against Pertussis

All acellular pertussis vaccines contain pertussis toxoid and induce protection against pertussis. This study investigated the relation between the postvaccination levels of pertussis toxin (PT) serum IgG and protection against pertussis. PT IgG was determined in sera obtained 21-77 days after the third vaccination from 813 children who received 3 doses of pertussis toxoid. The children were followed for 21-33 months after vaccination for the occurrence of pertussis. Of the children, 126 were exposed to pertussis in their households. The median PT IgG concentration was 79 U/mL in those who developed severe pertussis (>/=21 day of paroxysmal cough), 156 U/mL with mild pertussis (<21 days of paroxysmal cough), and 246 U/mL in those who did not develop pertussis (79 vs. 246, P<.0001). Corresponding values in the 687 children with no household exposure were 99, 124, and 155 U/mL, respectively (99 vs. 155, P<.0001). Thus, there is a highly significant correlation between the level of vaccine-induced serum PT IgG and protection against pertussis.

The Haemophilus ducreyi cytolethal distending toxin induces cell cycle arrest and apoptosis via the DNA damage checkpoint pathways

The cytolethal distending toxins (CDTs) induce cell cycle arrest by a mechanism still not well characterized. We demonstrate that the effect of the Haemophilus ducreyiCDT (HdCDT) is cell type-specific: B cell lines underwent apoptosis, epithelial cells and keratinocytes arrested exclusively in G2, whereas normal fibroblasts arrested both in G1 and G2. We studied normal keratinocytes and fibroblasts, which are relevant for understanding the pathogenicity ofH. ducreyi. The response to HdCDT resembles the checkpoint response activated by ionizing radiation. Both responses were characterized by an early induction of the p53 gene and the cyclin-dependent kinase inhibitor p21 in fibroblasts, and activation of the chk2 kinase in epithelial cells. In the Ataxia Telangiectasia-mutated gene (ATM)-deficient lymphoblastoid cell lines, intoxication was significantly delayed compared with ATM wild type cells, and was associated with a slower kinetic of p53 stabilization, suggesting that the early response to HdCDT is ATM-dependent. Activation of ATM-dependent pathways was further confirmed by the ability of caffeine to partially override the HdCDT-mediated cell cycle arrest. Our data shed new light on the mechanism of action of this novel family of bacterial toxins, limiting the target candidates to DNA or molecules directly involved in activation of checkpoint responses.

The cytolethal distending toxin from the chancroid bacterium Haemophilus ducreyi induces cell-cycle arrest in the G2 phase

The potent cytolethal distending toxin produced by Haemophilus ducreyi is a putative virulence factor in the pathogenesis of chancroid. We studied its action on eukaryotic cells, with the long-term goal of understanding the pathophysiology of the disease. Intoxication of cultured human epithelial-like cells, human keratinocytes, and hamster fibroblasts was irreversible, and appeared as a gradual distention of three- to fivefold the size of control cells. Organized actin assemblies appeared concomitantly with cell enlargement, promoted by a mechanism that probably does not involve small GTPases of the Rho protein family. Intoxicated cells did not proliferate. Similar to cells treated with other cytolethal distending toxins, these cells accumulated in the G2 phase of the cell cycle, demonstrating an increased level of the tyrosine phosphorylated (inactive) form of the cyclin-dependent kinase p34(cdc2). DNA synthesis was not affected until several hours after this increase, suggesting that the toxin acts directly on some kinase/phosphatase in the signaling network controlling the p34(cdc2) activity. We propose that this toxin has an important role both in the generation of chancroid ulcers and in their slow healing. The toxin may also be an interesting new tool for molecular studies of the eukaryotic cell- cycle machinery.

Clinical and immunologic responses to the capsular polysaccharide of Haemophilus influenzae type b alone or conjugated to tetanus toxoid in 18- to 23-month-old children.

The safety and immunogenicity of Haemophilus influenzae type b (Hib) capsular polysaccharide (CPS) alone, or covalently bound to tetanus toxoid in saline solution (Hib-TT) or adsorbed onto AI(OH)3 (Hib-TT ads), were evaluated after one injection into 18- to 23-month-old healthy children in Sweden. No side reactions were elicited by Hib CPS; side reactions elicited by the two conjugates were similar and comparable to those reported for diphtheria and tetanus toxoids adsorbed. Hib-TT was the most immunogenic of the three vaccines, eliciting about 10-fold higher antibody levels than Hib CPS; of 28 vaccinees, all had greater than 1.0 microgram Ab/mL serum after immunization with Hib-TT. Increases of Hib CPS antibodies within immunoglobulin classes induced by the three vaccines were, in decreasing order, IgG greater than IgM greater than IgA. Within IgG subclasses, rises in IgG1 Hib CPS antibodies were the most frequent, followed by IgG2; some vaccinees with high postimmunization levels also had rises in IgG3 and one in IgG4. Immunization-induced Hib CPS antibodies were bactericidal. Hib-TT also elicited higher levels of tetanus toxoid antibodies than Hib-TT ads; these tetanus toxoid antibodies neutralized tetanus toxin in vivo.

Cellular Internalization of Cytolethal Distending Toxin from Haemophilus ducreyi

ABSTRACT The chancroid bacterium Haemophilus ducreyi produces a toxin (HdCDT) which is a member of the recently discovered family of cytolethal distending toxins (CDTs). These protein toxins prevent the cyclin-dependent kinase cdc2 from being activated, thus blocking the transition of cells from the G2 phase into mitosis, with the consequent arrest of intoxicated cells in G2. It is not known whether these toxins act by signaling from the cell surface or intracellularly only. Here we report that HdCDT has to undergo at least internalization before being able to act. Cellular intoxication was inhibited (i) by removal of clathrin coats via K+depletion, (ii) by treatment with drugs that inhibit receptor clustering into coated pits, and (iii) in cells genetically manipulated to fail in clathrin-dependent endocytosis. Intoxication was also completely inhibited in cells treated with bafilomycin A1 or nocodazole and in cells incubated at 18°C, i.e., under conditions known to block the fusion of early endosomes with downstream compartments. Moreover, disruption of the Golgi complex by treatment with brefeldin A or ilimaquinone blocked intoxication. In conclusion, our data indicate that HdCDT enters cells via clathrin-coated pits and has to be transported via the Golgi complex in order to intoxicate cells. This is the first member of the family of CDTs for which cellular internalization and some details of the pathway have been demonstrated.

Etiology of community-acquired pneumonia in patients requiring hospitalization

The etiology of community-acquired pneumonia was studied in 127 patients with roentgenologically verified pneumonia who needed hospitalization. Etiology was determined on the basis of a positive blood culture and/or a significant antibody titer increase.Streptococcus pneumoniae was the probable etiological agent in 69 patients, nontypeableHaemophilus influenzae in five patients,Streptococcus pyogenes in two patients, andLegionella pneumophila andStaphylococcus aureus in one patient each. Evidence ofMycoplasma pneumoniae infection was found in 18 patients and ofChlamydia psittaci infection in three patients. Influenza virus type A was the cause of infection in 15 patients. One patient had infection with influenza virus type B, one patient with parainfluenza virus type 1, and three patients with respiratory syncytial virus. In 20 patients there was evidence of infection with more than one microorganism. No etiological agent was found in 27 patients. SinceStreptococcus pneumoniae was the predominant etiological agent penicillin should be drug of first choice in patients with pneumonia who need treatment in hospital. In young adults, however, the high frequency ofMycoplasma pneumoniae infection would justify the use of erythromycin or doxycycline as drug of first choice.

Mass vaccination of children with pertussis toxoid: decreased incidence in both vaccinated and nonvaccinated persons

During 1979-1995, there was no vaccination against pertussis in Sweden. With the aim of studying the epidemiology and transmission of pertussis, mass vaccination with pertussis toxoid of children born during the 1990s was instituted in the Göteborg area (population, 778,597) in 1995. Infants were offered 3 doses of pertussis toxoid combined with diphtheria and tetanus toxoids. Children aged > or =1 year were offered 3 doses of pertussis toxoid alone. From June 1995 through February 1999, 167,810 doses of pertussis toxoid were given to 61,219 children born during the 1990s (56% received 3 doses). The number of Bordetella pertussis isolates per year declined from 1214 (1993-1995) to 64 (January 1997 through June 1999; P<.0001), and hospitalizations due to pertussis declined from 62 to 5 (P<.0001). Significant decreases in B. pertussis isolates and hospitalizations occurred in all age groups, including adults and nonvaccinated infants. Thus, mass vaccination of children with pertussis toxoid decreases spread of B. pertussis in the population.

Etiology of community-acquired pneumonia in out-patients

Most studies undertaken to establish the etiology of pneumonia have been performed on hospitalized patients. In these patients Streptococcus pneumoniae has been shown to be the dominating microorganism (1--4). The etiology of pneumonia in out-patients might, however, be different in which case guide-lines for treatment based on studies of hospitalized patients might not be relevant for out-patients. For this reason we studied 54 out-patients comprising 21 men 15-69 years old (median age 27 years) and 33 women 19-62 years old (median age 31 years) who had symptoms and X-rays showing inflammatory changes compatible with pneumonia. Patients attended the out-patient clinic at the Department of Infectious Diseases in G6teborg. The study was performed over a three year period; there was no seasonal distribution of the cases. The patients had been ill for 1-14 days (median 6 days) before admission to the study. One patient had asthma, one hay-fever, one rheumatism and one coeliac disease. The other 50 patients had no known associated disease. Ten patients had received antibiotic treatment (seven phenoxymethylpenicillin, one ampicfllin and two doxycyeline) before nasopharyngeal culture was taken. At the first visit to the out-patient c l in ic nasopharyngeal secretion for culture and a serum sample for antibody determinations were obtained. Unfortunately it was not possible to collect sputum for practical reasons. A second serum sample was obtained 3 to 4 weeks later. Aerobic culture of nasopharyngeal secretion was performed on blood and hematin agar. Titers of antibodies to the following infectious agents were determined: Streptococcus pneumoniae, Haemophilus influenzae, Streptococcus pyogenes, Legionella pneumophila, Mycoplasma pneumoniae, Chlamydia psittaci, influenza virus types A and B, parainfluenza virus types 2 and 3, respiratory syncytial virus, adenoviruses, and enteroviruses. The antibody determinations were performed using enzyme-linked immunosorbent assays, neutralization tests, corn-