Automated angiodysplasia detection from wireless capsule endoscopy.

We present a novel system for the automatic detection of angiodysplasia lesions from capsule endoscopy images. The approach identifies potential regions of interest and classifies them using a combination of color-based, texture, statistical and morphological features. A boosted decision tree classification method is used in order to overcome the problem of unbalanced sampling between pathological and non-pathological regions. The lesion detection method has been designed and validated using a lesion database labelled by an expert. The approach achieves a sensitivity of 89.51% and a specificity of 96.8%, thus providing a high performance in the detection of angiodysplasia lesions.

Humoral immunity 10 years after booster immunization with an adolescent and adult formulation combined tetanus, diphtheria, and 5-component acellular pertussis vaccine.

Persistence of antibodies after a single dose of Tdap vaccine (tetanus, diphtheria, and 5-component acellular pertussis vaccine) was evaluated in a follow-up study of adolescents (N=324) and adults (N=644) who had received Tdap in earlier clinical trials. Outcome measures were seroprotection (tetanus and diphtheria) or seropositivity (pertussis) and geometric mean concentrations. Humoral immune responses to all antigens were robust 1 month after initial immunization, decreased at subsequent measurements, but continued to exceed pre-immunization levels 1, 3, 5, and 10 years later. Protective levels of diphtheria and tetanus antitoxin persisted in 99.3% of adolescents 10 years after a booster dose of Tdap. Seropositivity to 1 or more pertussis antigens also persisted in most adolescents for 10 years. Although tetanus antitoxin responses were similar in adults to those observed in adolescents, diphtheria antitoxin titers were lower, reflecting the fact that a smaller proportion of adults had received diphtheria toxoid in the previous 10 years compared to adolescents. These data will contribute to the selection of the optimal interval for repeat doses of Tdap.

Humoral immunity 5 years after booster immunization with an adolescent and adult formulation combined tetanus, diphtheria, and 5-component acellular pertussis vaccine.

Persistence of antibodies following a single dose of Tdap vaccine (tetanus, diphtheria, and five-component acellular pertussis vaccine for use in individuals past childhood) was evaluated in a follow-up of adolescents (N=324) and adults (N=644) who had received Tdap in earlier clinical trials. Outcome measures were seroprotection (tetanus and diphtheria) or seropositivity (pertussis) and geometric mean titers. Humoral immune responses to all antigens were robust 1 month after initial immunization; antibodies exceeded pre-immunization levels 1, 3, and 5 years later. These data will contribute to selecting the optimal interval for booster doses of Tdap.

Human papillomavirus E6E7-mediated adenovirus cell killing: selectivity of mutant adenovirus replication in organotypic cultures of human keratinocytes.

Replication-competent adenoviruses are being investigated as potential anticancer agents. Exclusive virus replication in cancer cells has been proposed as a safety trait to be considered in the design of oncolytic adenoviruses. From this perspective, we have investigated several adenovirus mutants for their potential to conditionally replicate and promote the killing of cells expressing human papillomavirus (HPV) E6 and E7 oncoproteins, which are present in a high percentage of anogenital cancers. For this purpose, we have employed an organotypic model of human stratified squamous epithelium derived from primary keratinocytes that have been engineered to express HPV-18 oncoproteins stably. We show that, whereas wild-type adenovirus promotes a widespread cytopathic effect in all infected cells, E1A- and E1A/E1B-deleted adenoviruses cause no deleterious effect regardless of the coexpression of HPV18 E6E7. An adenovirus deleted in the CR2 domain of E1A, necessary for binding to the pRB family of pocket proteins, shows no selectivity of replication as it efficiently kills all normal and E6E7-expressing keratinocytes. Finally, an adenovirus mutant deleted in the CR1 and CR2 domains of E1A exhibits preferential replication and cell killing in HPV E6E7-expressing cultures. We conclude that the organotypic keratinocyte culture represents a distinct model to evaluate adenovirus selectivity and that, based on this model, further modifications of the adenovirus genome are required to restrict adenovirus replication to tumor cells.

Tetrasomy is induced by human papillomavirus type 18 E7 gene expression in keratinocyte raft cultures.

We have demonstrated previously that oncogenic human papillomaviruses (HPVs) induce basal cell tetrasomy in low-grade squamous intraepithelial lesions of the cervix. To identify HPV genes and growth conditions involved in this process, we analyzed: (a) organotypic raft cultures of primary human keratinocytes transfected with whole HPV-18 genomes; and (b) organotypic raft cultures acutely infected with recombinant retroviruses expressing the HPV-18 E6, E7, or E6/E7 genes from the differentiation-dependent HPV-18 enhancer-promoter. Cultures were examined for HPV DNA by in situ hybridization and for karyotype by interphase cytogenetics. Tetrasomy occurred in the suprabasal strata of raft cultures expressing E7 and E6/E7 but not in those expressing E6 alone or in a control culture. These data indicate that suprabasal tetrasomy occurs in association with expression of the E7 gene alone. Basal cell tetrasomy was additionally observed in the raft culture transfected with whole HPV-18 genomes, consistent with observations in low-grade squamous intraepithelial lesions. The distribution of tetrasomic cells in these raft cultures may reflect the involvement of additional viral genes or possibly differences in the pattern of viral oncogene and host gene expression.

p21cip1 Degradation in differentiated keratinocytes is abrogated by costabilization with cyclin E induced by human papillomavirus E7.

The human papillomavirus (HPV) E7 protein promotes S-phase reentry in a fraction of postmitotic, differentiated keratinocytes. Here we report that these cells contain an inherent mechanism that opposes E7-induced DNA replication. In organotypic raft cultures of primary human keratinocytes, neither cyclin E nor p21cip1 is detectable in situ. However, E7-transduced differentiated cells not in S phase accumulate abundant cyclin E and p21cip1. We show that normally p21cip1 protein is rapidly degraded by proteasomes. In the presence of E7 or E6/E7, p21cip1, cyclin E, and cyclin E2 proteins were all up-regulated. The accumulation of p21cip1 protein is a posttranscriptional event, and ectopic cyclin E expression was sufficient to trigger it. In constract, cdk2 and p27kip1 were abundant in normal differentiated cells and were not significantly affected by E7. Cyclin E, cdk2, and p21cip1 or p27kip1 formed complexes, and relatively little kinase activity was found associated with cyclin E or cdk2. In patient papillomas and E7 raft cultures, all p27kip1-positive cells were negative for bromodeoxyuridine (BrdU) incorporation, but only some also contained cyclin E and p21cip1. In contrast, all cyclin E-positive cells also contained p27kip1. When the expression of p21cip1 was reduced by rottlerin, a PKC delta inhibitor, p27kip1- and BrdU-positive cells remained unchanged. These observations show that high levels of endogenous p27kip1 can prevent E7-induced S-phase reentry. This inhibition then leads to the stabilization of cyclin E and p21cip1. Since efficient initiation of viral DNA replication requires cyclin E and cdk2, its inhibition accounts for heterogeneous viral activities in productively infected lesions.

Transduction of the E6 and E7 genes of epidermodysplasia-verruciformis-associated human papillomaviruses alters human keratinocyte growth and differentiation in organotypic cultures.

Epidermodysplasia-verruciformis-associated human papilloma virus DNA has been detected in skin cancers, in premalignant and benign skin lesions, and in plucked hairs from immunocompetent and immunosuppressed patients. The role of epidermodysplasia-verruciformis-associated human papilloma virus in the pathogenesis of nonmelanoma skin cancer is still enigmatic. In organotypic cultures we investigated the effects of retroviral transduction of the E6 and E7 genes of epidermodysplasia-verruciformis-associated human papilloma virus types 5, 12, 15, 17, 20, and 38 on the growth and differentiation of human keratinocytes. Differentiation was disturbed to different degrees as revealed by histology and by the expression patterns of differentiation markers keratin 10 and small proline rich protein 2. Conversely, proliferating cell nuclear antigen was induced in some of the suprabasal, differentiated cells to varying extent. No unscheduled DNA synthesis was detected in these cells, however, as probed by 5'-bromo-2'-deoxyuridine incorporation. Most intriguingly, when the E6 and E7 genes of epidermodysplasia-verruciformis-associated human papilloma virus types 15 and 17 were transduced, a broadening layer of basal cells and an accelerated differentiation were observed. In addition, "papilla-like structures" comprising basal-like keratinocytes arose from the basal layer into the differentiated layers. These cells did not express the differentiation markers keratin 10 and small proline rich protein 2, but did actively replicate DNA. These observations warrant further research by using this system to elucidate the replication strategy of epidermodysplasia-verruciformis-associated human papilloma virus types in keratinocytes and to shed light on the role of these human papilloma virus types in the pathogenesis of skin cancer.

Nitric oxide, prostaglandins, and impaired cerebral blood flow autoregulation in group B streptococcal neonatal meningitis.

Impaired autoregulation of cerebral blood flow (CBF) contributes to CNS damage during neonatal meningitis. We tested (i) the hypothesis that cerebrovascular autoregulation is impaired during early onset group B streptococcal (GBS) meningitis, (ii) whether this impairment is regulated by vasoactive mediators such as prostaglandins and (or) nitric oxide (NO), and (iii) whether this impairment is preventable by specific and (or) nonspecific inhibitors: dexamethasone, ibuprofen, and Nomega-nitro-L-arginine, a NO inhibitor. Sterile saline or 10(9) colony-forming units (cfu) of heat-killed GBS was injected into the cerebral ventricle of newborn piglets. CBF autoregulation was determined by altering cerebral perfusion pressure (CPP) with balloon-tipped catheters placed in the aorta. GBS produced a narrow range of CBF autoregulation due to an impairment at the upper limit of CPP. We report that in vivo in the early stages (first 2 h) of induced GBS inflammation (i) GBS impairs the upper limit of cerebrovascular autoregulation; (ii) ibuprofen, dexamethasone, and Nomega-nitro-L-arginine not only prevent this GBS-induced autoregulatory impairment but improve the range of cerebrovascular autoregulation; (iii) these autoregulatory changes do not involve circulating cerebral prostanoids; and (iv) the observed changes correlate with the induction of NO synthase gene expression. Thus, acute early onset GBS-induced impairment of the upper limit of CBF autoregulation can be correlated with increases of NO synthase production, suggesting that NO is a vasoactive mediator of CBF.

Deregulation of cyclooxygenase and nitric oxide synthase gene expression in the inflammatory cascade triggered by experimental group B streptococcal meningitis in the newborn brain and cerebral microvessels.

Group B Streptococcus (GBS) is the most common cause of neonatal sepsis and meningitis. Despite antibiotics, GBS in the newborn initiates a cascade of molecular and biological events leading to altered cerebral perfusion, blood-brain barrier disruption, cerebral edema, intracranial hypertension, neurological damage, and even death. Having previously shown that GBS infection impairs cerebral blood flow autoregulation and increases prostaglandin (PG) levels, we examined the regulation of some crucial inflammatory mediators (PGs, nitric oxide (NO), tumor necrosis factor-a) in the brain and cerebral microvessels (MVs) from newborn piglets. Cyclooxygenase (COX), the key enzyme in PG biosynthesis, exists in two isoforms, COX-1 and COX-2. Both may be directly induced by NO in a model of renal inflammation. Besides its neurotransmitter role, NO is a potent vasorelaxant whose production is catalyzed by at least three distinct nitric oxide synthases (NOS) (bNOS, ecNOS, iNOS). Western blot analyses showed that the newborn (4 day old) brain expressed lower levels of COX-1 (8-fold), COX-2 (20-fold), bNOS (12-fold), and ecNOS (5-fold) than in the 1 day old. MV showed approximately equal levels of COX-2, lower levels of COX-1 (4-fold), bNOS (5-fold), and higher levels of ecNOS (20-fold) in comparison to 4-day-old cerebral MV. A 4-day-old brain expressed lower levels of bNOS (5-fold), ecNOS (10-fold), and COX-1 (2-fold) than the 6-week-old pig. COX-2 protein was undetected in a 4-day-old pig brain, but present in great excess in MV. Purified MV showed lower ecNOS (14-fold), COX-1 (2-fold), and about equal levels of bNOS and COX-2 in comparison with MV from 6-week-old pigs. Reverse transcription polymerase chain reaction analyses confirmed these results. Treatment with noo-nitro-L-arginine (LNA), a NOS inhibitor, downregulated COX-1 expression in the newborn brain and both COX-1 and COX-2 cerebral MV expression. GBS infection (10(9) colony-forming units, 0.5 mL intracerebroventricular) of sedated newborn piglets induced the expression of tumor necrosis factor-alpha in the cerebrospinal fluid after 2 hours, upregulated bNOS expression in both brain and MVs, upregulated ecNOS in MVs, and downregulated COX-1, COX-2, and ecNOS in the brain. GBS did not trigger the expression of iNOS. Our data suggest that there is a net deficiency of NOS isoforms in the immature brain and microvasculature of the 4-day-old piglet and that the differences in expression lead to the immature control of NO and PG production, rendering newborns particularly susceptible to neurological damage because of the undeveloped nature of their response mechanisms. Moreover, the GBS-induced cascade deregulates the gene expression of interacting inflammatory mediators and may cause a net vasoconstrictor/vasodilator imbalance, leading to cerebral hypertension and edema in the early stages of infection. Pharmacological manipulations of the inflammatory cascade could lead to novel therapeutic approaches for the treatment of GBS meningitis.

Trichostatin A up-regulates human papillomavirus type 11 upstream regulatory region-E6 promoter activity in undifferentiated primary human keratinocytes.

Human papillomavirus (HPV) gene expression in squamous epithelia is differentiation dependent in benign patient lesions and in organotypic raft cultures of primary human keratinocytes (PHKs). Using the lacZ reporter in raft cultures, we previously showed that this transcriptional regulation of the HPV type 11 (HPV-11) enhancer-promoter located in the upstream regulatory region (URR) appears to have resulted from coordination between the transcription transactivators AP1, Oct1, and Sp1 in differentiated upper strata and the repressor C/EBP in proliferating basal cells. We report here that trichostatin A, a specific inhibitor of histone deacetylase, dramatically stimulated reporter gene activity from the wild-type HPV-11 URR or the C/EBP mutation in PHKs grown in undifferentiated submerged cultures. In epithelial raft cultures, up-regulation occurred predominantly in basal and parabasal strata; this effect was promoter specific, as expression of the lacZ reporter gene driven by the murine leukemia virus long terminal repeat (LTR), the keratin 14 promoter, or the involucrin promoter was not altered, nor was expression of endogenous keratin 10 and profilaggrin affected. However, the responses were not cell type or species specific, as identical results were observed for both HPV-11 URR-lacZ and LTR-lacZ in murine retrovirus producer cell lines of fibroblast origin.

Characterization of B lymphocytes rescued from apoptosis by platelet-activating factor.

B lymphocyte development is characterized by deletion via apoptosis of immature cells that are insufficiently stimulated. We have previously demonstrated that crosslinking of the B cell receptor (BCR) using anti-IgM antibodies (alphaIgM) (2 microg/ml) in Ramos B lymphoblastoid cells causes deletion of 30-40% of cells by apoptosis in 24 h. Addition of the potent lipid mediator platelet-activating factor (10(-7) M) to alphaIgM stimulated Ramos cells significantly decreases the number of apoptotic cells as measured by annexin V labeling. We have characterized the phenotype of Ramos cells that have not become apoptotic following BCR stimulation. In these cells, there is a significant decrease in the surface expression of the VLA-4 adhesion molecule (31% of control expression) and surface IgM expression (sIgM) (53% of control expression). Significantly fewer cells co-incubated with platelet-activating factor (PAF) underwent apoptosis, and the remaining cells maintained control levels of VLA-4 (104% of control expression) and sIgM expression (104% of control). All of these protective effects were inhibited by the specific PAF receptor antagonist, WEB 2170. The action of PAF on alphaIgM induced apoptosis was not inhibited by either cycloheximide or cytochalasin B, suggesting that de novo protein synthesis and F-actin polymerization were not implicated in the rescue of Ramos cells by PAF. In contrast, the ability of PAF to maintain sIgM and VLA-4 expression at control levels was inhibited by cycloheximide (7. 5 microg/ml). Cytochalasin B (5 microg/ml) had no effect on sIgM expression but blocked the decrease in VLA-4 expression mediated by alphaIgM. These data indicate that PAF's effect on rescuing and maintaining alphaIgM stimulated Ramos B cells is mediated via at least two pathways. Abrogation of apoptosis does not require de novo protein synthesis, while maintenance of sIgM and VLA-4 expression requires protein synthesis.

Heme compounds as iron sources for nonpathogenic Rhizobium bacteria.

Many animal-pathogenic bacteria can use heme compounds as iron sources. Like these microorganisms, rhizobium strains interact with host organisms where heme compounds are available. Results presented in this paper indicate that the use of hemoglobin as an iron source is not restricted to animal-pathogenic microorganisms. We also demonstrate that heme, hemoglobin, and leghemoglobin can act as iron sources under iron-depleted conditions for Rhizobium meliloti 242. Analysis of iron acquisition mutant strains indicates that siderophore-, heme-, hemoglobin-, and leghemoglobin-mediated iron transport systems expressed by R. meliloti 242 share at least one component.

Platelet-activating factor abrogates apoptosis induced by cross-linking of the surface IgM receptor in a human B lymphoblastoid cell line.

B lymphocyte development is characterized by deletion, via apoptosis, of immature cells that are stimulated via the B cell receptor in the absence of a second signal. We have investigated whether platelet-activating factor (PAF), a potent B lymphocyte activator, can provide a complementary signal with B cell receptor ligation to abrogate apoptosis. Cross-linking of the surface IgM on Ramos B lymphoblastoid cells using anti-IgM Abs (2 microg/ml) caused programmed cell death in 34 +/- 5.4% of the cells. Coincubation of PAF (10(-7)M) with alphaIgM led to a significant decrease in apoptotic cells as measured by DNA laddering and TUNEL assay (13.8 +/- 3%). The effect of PAF was dose dependent (10(-7)-10(-9) M) and was inhibited by the specific PAF receptor antagonist, WEB 2170. PAF protected cells from the effect of alphaIgM for up to 1 h after it was added. alphaIgM-induced programmed cell death in Ramos cells was blocked by catalase and, therefore, is caused in part by the production of toxic hydroxyl radicals from hydrogen peroxide. We investigated the action of PAF on markers of intracellular oxidation. H2O2 in low doses induced apoptosis, via production of OH. radicals. PAF inhibited H2O2-induced apoptosis in Ramos cells; it also attenuated H2O2- and alphaIgM-mediated increases in hydroxyl radical (OH.) as measured by the oxidation of 2',7'-dichlorofluorescein diacetate to 2',7'-dichlorofluorescein and blocked the depletion of reduced glutathione induced by alphaIgM. PAF maintained IgM secretion, which was greatly inhibited by incubation with alphaIgM alone. These data indicate that PAF potentially provides an important cosignal to surface IgM-stimulated Ramos cells by inhibiting apoptosis. This is in part due to the activity of PAF in the oxidant/ antioxidant pathway.

Biochemical mediators of meningeal inflammatory response to group B streptococcus in the newborn piglet model.

The meningeal inflammatory response to a heat-killed mutant unencapsulated strain of type III group B Streptococcus (GBS) was studied in a newborn piglet model. GBS (10(9) colony-forming unit equivalents) or saline (control) was inoculated intraventricularly. Serial cerebrospinal fluid measurements were done at baseline and over the course of the next 24 h for cytochemical changes and production of tumor necrosis factor (TNF) and prostaglandins. In separate experiments, we defined the time course of early changes during the first 6 h and dose response relationship over a range of inocula 10(6) to 10(9) colony-forming unit equivalents. The intraventricular inoculation of the heat-killed unencapsulated GBS induced marked leukocytosis and increased protein by 6 h. These changes were preceded by a several hundredfold increase in TNF (maximum at 2 h) and prostaglandins (maximum at 2-4 h). The early and sharp rise in TNF suggests its pivotal role in initiating the inflammatory cascade. The magnitude of the inflammatory response increased with increasing bacterial dose over the range studied. To study the effect of encapsulation of GBS in the induction of meningeal inflammation, we compared the response to the unencapsulated mutant strain with that to the encapsulated parent strain. The encapsulated strain produced much smaller inflammatory changes, and only with high doses of bacteria. The GBS cell wall appeared to be the primary bacterial product triggering inflammation. Intraventricular injection of the heat-killed unencapsulated GBS with exposed cell wall can serve as a valid model for studying neonatal meningitis.

Effect of group B streptococcal meningitis on retinal and choroidal blood flow in newborn pigs.

PURPOSE: To assess the effect of group B streptococcal (GBS) meningitis on retinal blood flow (RetBF) and choroidal blood flow (ChBF) autoregulation in sedated newborn piglets (1 to 5 days of age). METHODS: Fourteen study animals injected with 0.5 ml heat-killed GBS (10(9)) were compared to 10 control animals injected with 0.5 ml saline. The site of injection for both groups was the cerebral lateral ventricles. RetBF and ChBF were measured by radioactive microspheres (141Ce, 51Cr, 113Sn, 85Sr, 95Nb, 46Sc) over a mean arterial blood pressure (MABP) range of 20 to 150 mm Hg. Hypertension and hypotension were induced 2 hours apart in random sequence on each animal by inflating balloon-tipped catheters placed at the descending aorta and the aortic root, respectively. RetBF and ChBF were measured 15 minutes before and after injection of GBS or saline (baseline) and during hypotension or hypertension. RESULTS: Fifth-order polynomial regression analyses of RetBF and ChBF (ml/100 g per minute) versus MABP showed that in control animals, blood flows were constant at MABP of 60 to 110 mm Hg for RetBF and was pressure passive above and below these ranges. However, no autoregulation was observed for ChBF throughout the MABP range. In contrast, RetBF of GBS-treated animals increased with increasing blood pressure throughout range of MABP studied, and absence of autoregulation was maintained in the choroid. Vascular resistance (mm Hg/ml per minute/100 g) increased as MABP was raised to maintain constant flow and was correlated linearly with MABP at 60 to 110 mm Hg (r = 0.6682, P = 0.0003) in RetBF of control animals but not in GBS-treated animals (r = -0.291, P = NS). Vascular resistance did not change with MABP for ChBF of control animals (r = -0.264, P = NS) but decreased as MABP was raised in GBS-treated animals (r = -0.548, P < 0.0001). GBS did not alter oxygen delivery, which varied directly with MABP in control animals (RetBF: r = 0.74, P < 0.001; ChBF: r = 0.68, P < 0.001) and in GBS-treated animals (RetBF: r = 0.55, P < 0.001; ChBF: r = 0.68, P < 0.001). CONCLUSION: Group B streptococcal meningitis significantly impairs eye blood flow autoregulation and may contribute to increased risk of retinal damage in infants with meningitis.

Neutrophil Fc receptor participation in phagocytosis of type III group B streptococci.

Human peripheral blood neutrophils bear receptors for immunoglobulin G, FcRII, and FcRIII that differ structurally and functionally. We investigated the role of FcRII and FcRIII in the phagocytosis of group B streptococci (GBS) by measuring neutrophil uptake of radiolabeled type III GBS. The mean uptake of GBS opsonized with human serum containing complement and specific antibody was 76%, but when this serum was heated, the mean uptake was only 22%. A monoclonal antibody to FcRIII, Leu-11b, inhibited in a dose-dependent manner uptake of GBS opsonized with heated or intact serum to maxima of 40 and 30%, respectively. Conversely, a monoclonal antibody to FcRII, IV.3, inhibited by 77% the uptake of GBS opsonized with heated serum but had no effect when GBS was opsonized with intact serum. Leu-11b and IV.3 had an additive inhibitory effect with heated but not with intact serum. Neither monoclonal antibody inhibited the uptake of GBS opsonized with hypogammaglobulinemic serum. Therefore, FcRII is the primary mediator of the phagocytosis of GBS opsonized by antibody alone, whereas FcRIII plays a lesser role. Surprisingly, FcRII is not necessary for phagocytosis when complement is also present. FcRIII participates, to a limited extent, in phagocytosis of GBS opsonized with antibody whether or not complement is present. These findings suggest that the function of FcRII in triggering phagocytosis may be particularly important in host defense against type III GBS in the setting of complement deficiency of young infants.

Prevention of group B streptococcal infection.

Group B streptococci continue to be major perinatal pathogens, both for mothers and their infants, and are associated with significant morbidity, mortality, and its attendant cost to society. Approaches to prevention are directed toward either eliminating exposure to the organism or enhancing host resistance, that is, chemoprophylaxis and immunoprophylaxis. Intrapartum chemoprophylaxis has been shown to effectively interrupt vertical transmission of group B streptococci from the genitally colonized mother to the infant and to decrease the incidence of both maternal and early-onset neonatal group B streptococcal disease. To avoid unnecessarily exposing large numbers of colonized women to antibiotics, only those with defined risk factors should be selected for intrapartum chemoprophylaxis. This regimen is ampicillin given intravenously, 2 g initially at onset of labor or rupture of membranes, followed by 1 g every 4 hours until delivery. Risk factors include premature onset of labor or rupture of membranes before 37 weeks' gestation, rupture of membranes of more than 12 hours, intrapartum fever, group B streptococcal bacteriuria, or having previously delivered an infant with group B streptococcal disease. Detection of anogenital colonization is accomplished either by culture late in the second or early in the third trimester or by intrapartum group B streptococcal antigen testing of vaginal swabs from those previously culture-negative or not cultured. Although this approach combines the advantages of several proposed strategies, it will still miss those cases of group B streptococcal disease developing in the absence of discernible risk factors. Intrapartum prophylaxis does not prevent late-onset group B streptococcal disease. Prenatal and postnatal chemoprophylaxis have not been shown to be effective. Symptomatic infants born to mothers given chemoprophylaxis should be evaluated for neonatal sepsis and treated accordingly. This approach is also suggested for asymptomatic premature infants, those whose mothers have not received adequate prophylaxis or have previously delivered infants with group B streptococcal disease, and for twin siblings of infants developing group B streptococcal disease. Successful implementation of this approach may be limited by the availability and sensitivity of the rapid antigen test used. Immunoprophylaxis, and active immunization in particular, is the most promising method of preventing perinatal group B streptococcal disease in mothers and their infants, including late-onset disease. Immunization of pregnant women with type III polysaccharide vaccine has resulted in adequate provision of functional antibody to the infants born to responders.(ABSTRACT TRUNCATED AT 400 WORDS)

Potential use of intravenous immune globulin for group B streptococcal infection.

Several lines of evidence suggest that passive immunization as adjunctive therapy for or prevention of group B streptococcal (GBS) sepsis in neonates will require the use of preparations of human intravenous immune globulin (IVIG) that are hyperimmune for protective antibodies to GBS. Results from both in vitro and in vivo experiments utilizing commercially available IVIG preparations suggest that the doses necessary for achieving levels of pathogen-specific antibody capable of promoting efficient opsonization and phagocytosis of GBS may be prohibitive. Several laboratories have reported that standard IVIG preparations contain only modest levels of antibodies to the four capsular polysaccharides of GBS (the protective moieties), are variable in their effect on in vitro opsonophagocytosis by dose and method of preparation, and are significantly less protective in animal models than is IVIG prepared from adults immunized with GBS polysaccharide vaccines. Further, when we gave a single infusion of standard IVIG at a dose of either 500 or 750 mg/kg to 10 premature neonates during the first week of life, opsonophagocytosis of type III GBS by their sera and adult neutrophils was observed only when high levels of specific antibody were achieved, levels only transiently achieved in nonimmune infants. Commercial preparation of human immune globulin hyperimmune for GBS will be required for optimal adjunctive therapy in patients with sepsis due to GBS and for the possible prevention of late-onset infant disease.

Role of intravenous immunoglobulin in prevention of late-onset infection in low-birth-weight neonates. The Neonatal IVIG Study Group.

As a result of inadequate placental transport of maternal IgG, preterm neonates of less than 32 weeks' gestation, especially those with birth weights less than 1,500 g, are profoundly hypogammaglobulinemic at birth, a condition that worsens during the first several weeks of life. This hypogammaglobulinemia is believed to contribute to their high frequency of late-onset sepsis, with its accompanying morbidity and mortality. Animal studies suggest that human immunoglobulin prepared for intravenous use (IVIG) improves host defense against pathogens that cause neonatal infections, but studies of IVIG in human neonates have been inconclusive because of the small numbers of infants included, lack of suitable controls, use of clinical rather than strict microbiologic definition of sepsis, and performance only in a single hospital outside the United States. A double-blind, randomized, placebo-controlled multicenter trial in the United States is in progress to determine the efficacy of IVIG in the prevention of late-onset infections in infants with birth weights between 500 and 1,750 g. Infants are infused with 500 mg of IVIG/kg or albumin-saline placebo at 3-7 days of age, 7 days later, and every 14 days for five doses. Efficacy parameters include mortality, number of proved infectious episodes (bacterial, fungal, or viral), and infection-related morbidity. Definitive guidelines for the possible use of prophylactic IVIG in low-birth-weight neonates should result from this evaluation of 500 to 700 infants in the United States.