Age-related efficacy of Shigella O-specific polysaccharide conjugates in 1-4-year-old Israeli children.

BACKGROUND: Despite its high worldwide morbidity and mortality, there is yet no licensed vaccine for shigellosis. We reported the safety and immunogenicity of Shigella O-specific polysaccharide-protein conjugates in adults and young children and efficacy of Shigella sonnei conjugate in young adults. METHODS: A double-blinded, randomized and vaccine-controlled Phase 3 evaluation of S. sonnei and Shigella flexneri 2a O-SP-rEPA conjugates, 25 microg, injected IM twice, 6 weeks apart, into healthy 1-4 years old, is reported. The children were followed for 2 years by telephone every other week and stool cultures were obtained for each episode of acute diarrhea (> or =3 loose stools/day or a bloody/mucous stool). Sera were taken randomly from 10% of the participants for IgG anti-LPS and anti-carrier levels. RESULTS: Of the 2799 enrollees, 1433 received S. sonnei and 1366 S. flexneri 2a conjugates; 2699 (96.4%) completed the 2-year follow-up. Local reactions occurred in approximately 5% and approximately 4% had temperatures > or =38.0 degrees C lasting 1-2 days. There were no serious adverse events attributable to the vaccines. Of the 3295 stool cultures obtained, 125 yielded S. sonnei and 21 S. flexneri 2a. Immunogenicity and efficacy were age-related. The overall efficacy of the S. sonnei conjugate was 27.5%; 71.1% (P=0.043) in the 3-4 years old. The numbers for S. flexneri 2a were too few for meaningful analysis. Cross-protection by S. flexneri 2a for non-vaccine S. flexneri types was found, but the numbers were too few for statistical significance. There was an age-related rise of vaccine-specific IgG anti-LPS in both groups, peaking at about 10 weeks and declining thereafter, but remaining > or =4-fold higher than in the controls 2 years after the second dose. CONCLUSIONS: Shigella conjugates are safe and immunogenic in 1-4 years old. The S. sonnei conjugate elicited 71.1% efficacy in the 3-4 years old and can be predicted to be efficacious in individuals older than 3 years of age. These results urge studies with our improved conjugates.

The effect of active immunization on varicella-related hospitalizations in Israel.

The purpose of this study is to report on the impact of introduction of the varicella vaccine "Varilix" on hospitalizations due to varicella, following licensure in Israel in June, 2000. Data on children hospitalized throughout Israel with the diagnosis of varicella were collected from 1998 until 2003. The national rate of varicella-related hospitalizations decreased during the period 2001-2002. However in 2003 an increase in hospitalization occurred. Based on an assumption that at least 22,000 vaccinations per year were administered, we estimate that there is a greater than 60% reduction in the risk for hospitalization in the immunized population (RR = 0.32; 0.10-1.00). In summary, no national trend in reduction of hospitalization has yet been observed, but a significant reduction in hospitalization is apparent for vaccinated children.

O-specific [corrected] polysaccharide conjugate vaccine-induced [corrected] antibodies prevent invasion of Shigella into Caco-2 cells and may be curative.

The O-specific polysaccharide (O-SP) domain of Shigella LPS is both an essential virulence factor and a protective antigen for this genus. A critical level of serum IgG anti-O-SP was shown to confer immunity to shigellosis, likely by complement-mediated bacteriolysis of the inoculum. Conjugate Shigella O-SP vaccines were shown to be safe and immunogenic in children, and, in a preliminary study, Shigella sonnei vaccine was protective in young adults. Characteristic of shigellosis is bacterial invasion of intestinal cells. Incubation of shigellae with postimmunization but not preimmunization sera of children vaccinated with S. sonnei or Shigella flexneri 2a O-SP conjugate vaccines inhibited in a type-specific and dose-dependent manner in vitro invasion of intestinal epithelial cells (Caco-2) and the infection-associated increases in IL-1beta and IL-8 mRNA and extracellular cytokine levels. Pretreatment of these sera or of Caco-2 cells with O-SP abrogated these effects also in a type-specific and dose-dependent manner. Confocal microscopy demonstrated antibody-specific inhibition of bacterial adhesion to HeLa cells. These protective effects were duplicated by IgG purified from these sera. These results suggest a dual role for IgG anti-O-SP. In addition to lysis of the inoculum in immune individuals, the newly synthesized IgG anti-O-SP in patients may terminate an established infection by inhibiting shigellae released from epithelial cells from invading new ones. A critical level of IgG anti-O-SP could, therefore, have a protective as well as a curative role in shigellosis.

[Vaccines for all occasions].

The strategy of immunizing a population at risk of infectious disease has been enormously successful medically and has also proven to be cost effective. Development of effective immunogens, that induce active immunization, is a long process that requires careful monitoring and assurance of short and long term safety, induction of protective immunity and proven efficacy in preventing the disease. A successful immunization program is also dependent on delivery of the vaccine to as many susceptible individuals as possible, so as to attain herd immunity. Passive immunization with antibodies, usually used prior to the development of active vaccines has also been remarkably effective. The special circumstances of the field and crowded conditions have demanded that the Medical Corps of the Israeli army cater for the needs of our soldiers. In this issue, the past achievements and current immunization policy are outlined for the first time. Their contribution to the health of our soldiers is commendable. Close monitoring of the epidemiology of infectious disease in the special circumstances of field conditions has prompted successful programs to markedly reduce infectious hepatitis A by passive immunization with gamma globulin in the past and, nowadays, with the killed active viral vaccine. In addition, prevention of influenza by killed viral vaccine and invasive bacterial disease by Neisseria meningitidis with multivalent polysaccharide vaccines are being used. This group has also improved hygienic conditions in the field to cope with shigellosis and salmonella infections. Research in the development of effective vaccines for protection of shigellosis has also been addressed by this group. New challenges posed by the emerging infectious diseases and the possible effects of bioterrorism are certain to keep this group on their toes.

Use of a computerized database to study the effectiveness of an attenuated varicella vaccine.

BACKGROUND: The varicella vaccine Varilrix (GlaxoSmithKline) was introduced in Israel in June 2000 as an optional vaccination for children. METHODS: We used the database of a single health maintenance organization that serves 25% of the population in Israel to assess the effectiveness of the vaccine retrospectively. Incidence and complications of varicella were derived from the database from January 1, 1998 until December 31, 2002. RESULTS: Since licensure >30000 individuals younger than 10 years in this health maintenance organization have been immunized with the vaccine. Annual incidence of disease per 1000 in the study population was 86.6 in 1998, 74.6 in 1999, 74.0 in 2000, 37.1 in 2001 and 44.6 in 2002. This declining trend in incidence of disease was statistically significant. Complications of varicella occurred in approximately 1% of patients throughout the 5-year study period, but there was a parallel decline in the number of patients with complications corresponding to the decline in disease incidence. Vaccine effectiveness for prevention of clinical disease in this population was 92% (95% confidence interval, 91.0 to 92.7). There were varying rates of utilization within communities of varied socioeconomic class, so that in the higher socioeconomic class there was an increased utilization and a corresponding decrease of attack rate; whereas in communities where there were lower utilization rates, corresponding increased numbers of varicella cases were seen. CONCLUSION: This database enables long term follow-up of the effectiveness of this vaccine in a large population.

Safety and immunogenicity of Shigella sonnei-CRM9 and Shigella flexneri type 2a-rEPAsucc conjugate vaccines in one- to four-year-old children.

BACKGROUND AND OBJECTIVE: Shigella conjugate vaccines have been shown to be safe, immunogenic and efficacious in adult volunteers. We have now investigated the safety and immunogenicity of investigational Shigella sonnei and Shigella flexneri 2a conjugate vaccines in 1- to 4-year-old children, the age group at greatest risk for shigellosis. METHODS: The O-specific polysaccharides of S. sonnei and S. flexneri 2a, the two most common shigellae from patients in Israel, were bound to medically useful carrier proteins to form conjugates. Eighty healthy 1- to 4-year-olds were randomized to receive two 0.5-ml im injections 6 weeks apart of either S. sonnei-CRM(9) or S. flexneri 2a-rEPA(succ). Blood was taken before, 6 weeks after the first injection, 4 weeks after the second injections and 2 years after immunization for assay of IgG anti-lipopolysaccharide, diphtheria toxin and Pseudomonas aeruginosa exotoxin A antibodies by enzyme-linked immunosorbent assay. RESULTS: During an 8-day surveillance period after each immunization, low fever (37.8-39.0 degrees C) lasting only 24 to 48 h occurred in 2 of 40 recipients after the first injection and 4 of 40 recipients after the second injection of S. flexneri 2a-rEPA(succ) and in 2 of 38 of S. sonnei-CRM(9) after the second injection; no fever was detected after the first injection. Liver function tests were normal in all vaccinees. S. sonnei-CRM(9) elicited a >4-fold rise in IgG anti-LPS in 92.1% and S. flexneri 2a-rEPA(succ) in 85% (P < 0.0001) after the second injection; both conjugates elicited type-specific booster responses. At 2 years the geometric mean concentrations of both IgG anti-lipopolysaccharides were significantly higher than preimmunization levels. A >4-fold rise of IgG anti-diphtheria (65.8%) and IgG anti-ETA (77.5%) was observed. CONCLUSION: These experimental Shigella conjugate vaccines were safe and immunogenic in 1- to 4-year-old children.

Human and porcine early kidney precursors as a new source for transplantation.

Kidney transplantation has been one of the major medical advances of the past 30 years. However, tissue availability remains a major obstacle. This can potentially be overcome by the use of undifferentiated or partially developed kidney precursor cells derived from early embryos and fetal tissue. Here, transplantation in mice reveals the earliest gestational time point at which kidney precursor cells, of both human and pig origin, differentiate into functional nephrons and not into other, non-renal professional cell types. Moreover, successful organogenesis is achieved when using the early kidney precursors, but not later-gestation kidneys. The formed, miniature kidneys are functional as evidenced by the dilute urine they produce. In addition, decreased immunogenicity of the transplants of early human and pig kidney precursors compared with adult kidney transplants is demonstrated in vivo. Our data pinpoint a window of human and pig kidney organogenesis that may be optimal for transplantation in humans.

Treatment of chronic granulomatous disease with myeloablative conditioning and an unmodified hemopoietic allograft: a survey of the European experience, 1985-2000.

Treatment of chronic granulomatous disease (CGD) with myeloablative bone marrow transplantation is considered risky. This study investigated complications and survival according to different risk factors present at transplantation. The outcomes of 27 transplantations for CGD, from 1985 to 2000, reported to the European Bone Marrow Transplant Registry for primary immunodeficiencies were assessed. Most transplant recipients were children (n = 25), received a myeloablative busulphan-based regimen (n = 23), and had unmodified marrow allografts (n = 23) from human leukocyte antigen (HLA)-identical sibling donors (n = 25). After myeloablative conditioning, all patients fully engrafted with donor cells; after myelosuppressive regimens, 2 of 4 patients fully engrafted. Severe (grade 3 or 4) graft-versus-host disease (GVHD) disease developed in 4 patients: 3 of 9 with pre-existing overt infection, 1 of 2 with acute inflammatory disease. Exacerbation of infection during aplasia was observed in 3 patients; inflammatory flare at the infection site during neutrophil engraftment in 2: all 5 patients belonged to the subgroup of 9 with pre-existing infection. Overall survival was 23 of 27, with 22 of 23 cured of CGD (median follow-up, 2 years). Survival was especially good in patients without infection at the moment of transplantation (18 of 18). Pre-existing infections and inflammatory lesions have cleared in all survivors (except in one with autologous reconstitution). Myeloablative conditioning followed by transplantation of unmodified hemopoietic stem cells, if performed at the first signs of a severe course of the disease, is a valid therapeutic option for children with CGD having an HLA-identical donor.

Engraftment and differentiation of human metanephroi into functional mature nephrons after transplantation into mice is accompanied by a profile of gene expression similar to normal human kidney development.

Metanephroi, the embryonic precursors of the adult kidney, can be induced in vivo to grow and develop. Despite their potential clinical utility for transplantation, the ability of human metanephroi to differentiate after transplantation into functional mature nephrons is mostly unknown. To address this, 70-d human metanephroi were transplanted into NOD/SCID mice; global gene expression patterns that underlie development of human metanephric transplants were analyzed and compared with normal human kidney development. In addition, functionality of the grafts was assessed by dimercaptosuccinic acid radioisotope scans at different times after transplantation. The results of hybridization to cDNA arrays when RNA was derived from normal human kidneys at 8, 12, 16, and 20 wk gestation demonstrated that a subset of 240 genes changed substantially with time. The induced genes can be classified as cell cycle regulators, transcription and growth factors, and signaling, transport, adhesion, and extracellular matrix molecules. Strikingly, clustering analysis of global gene expression at 2, 6, and 10 wk after metanephric transplantation revealed an expression profile that characterizes normal human kidney development. Moreover, maturation of the transplants was accompanied by an increased uptake of dimercaptosuccinic acid. Nevertheless, expression levels of specific genes were mostly found to be suppressed in the transplants compared with the normal kidneys. These data provide insights into human kidney development and support the possibility of the transplantability of human metanephroi. Understanding of the molecular regulation of the transplanted developing metanephroi might lead to the development of strategies aimed at increasing the levels of specific genes, nephron endowment, and graft function.