Modelling the initial phase of an epidemic using incidence and infection network data: 2009 H1N1 pandemic in Israel as a case study.

This paper presents new computational and modelling tools for studying the dynamics of an epidemic in its initial stages that use both available incidence time series and data describing the population's infection network structure. The work is motivated by data collected at the beginning of the H1N1 pandemic outbreak in Israel in the summer of 2009. We formulated a new discrete-time stochastic epidemic SIR (susceptible-infected-recovered) model that explicitly takes into account the disease's specific generation-time distribution and the intrinsic demographic stochasticity inherent to the infection process. Moreover, in contrast with many other modelling approaches, the model allows direct analytical derivation of estimates for the effective reproductive number (R(e)) and of their credible intervals, by maximum likelihood and Bayesian methods. The basic model can be extended to include age-class structure, and a maximum likelihood methodology allows us to estimate the model's next-generation matrix by combining two types of data: (i) the incidence series of each age group, and (ii) infection network data that provide partial information of 'who-infected-who'. Unlike other approaches for estimating the next-generation matrix, the method developed here does not require making a priori assumptions about the structure of the next-generation matrix. We show, using a simulation study, that even a relatively small amount of information about the infection network greatly improves the accuracy of estimation of the next-generation matrix. The method is applied in practice to estimate the next-generation matrix from the Israeli H1N1 pandemic data. The tools developed here should be of practical importance for future investigations of epidemics during their initial stages. However, they require the availability of data which represent a random sample of the real epidemic process. We discuss the conditions under which reporting rates may or may not influence our estimated quantities and the effects of bias.

Peptide mapping and characterisation of glycation patterns of the glima 38 antigen recognised by autoantibodies in Type I diabetic patients.

AIMS/HYPOTHESIS: Glima 38 is an N-glycated neuroendocrine membrane protein of M(r) 38,000, which is recognised by autoantibodies in approximately 20% of patients with Type I (insulin-dependent) diabetes mellitus. The aim of this study was to characterise the carbohydrate moiety and generate peptide maps of glima 38. METHODS: Sera of high immunoreactivity to glima 38 were used to isolate 35-S methionine-labelled protein from betaTC-3 cells and a neuronal cell line GT1.7. Tunicamycin was used to inhibit N-glycation of glima 38 and define the core protein. The carbohydrate moiety was characterised for tunicamycin sensitivity, lectin binding and susceptibility to different endoglycosidases. The protein moiety was subjected to digestion by proteases to define peptide maps. RESULTS: The autoreactive epitopes in glima 38 recognised by Type I diabetic sera are conformational and independent of the carbohydrate moiety. Inhibition of N-glycation of glima 38 in vivo, shows a protein core of M(r) 22,000 in both pancreatic beta-(betaTC3) and neuronal (GT1.7) cell lines. The carbohydrate moieties in the two cell types are distinct but contain a similar amount of terminal sialic acid residues and at least five oligosaccharide chains Glima 38 binds Triticum vulgare and Ricinus communis I lectins. Endoproteinase treatment of the M(r) 22,000 core protein results in peptides of M(r) 4500 and M(r) 20,000 with Lys-C, and peptides of M(r) 4000 and M(r) 11,000-12,000 with Glu-C/V8 and Asp-N proteases. CONCLUSION/INTERPRETATION: The biochemical properties of glima 38 define it as a new autoantigen in Type I diabetes and provide a basis for its purification.

Validity of screening for individuals at risk for type I diabetes by combined analysis of antibodies to recombinant proteins.

OBJECTIVE: To determine whether screening for the presence of multiple antibody markers for IDDM is effective at identifying individuals with high risk for disease development. RESEARCH DESIGN AND METHODS: Antibodies to GAD and the tyrosine phosphatase-like protein 1A-2 were determined in sequential serum samples from 44 first-degree relatives of IDDM patients, identified as possessing islet cell antibody (ICA) and/or insulin autoantibody (IAA), who were followed prospectively for IDDM development, ICA, IAA, and antibodies to GAD and 1A-2 were also determined in 93 cases of new-onset nonfamilial IDDM. RESULTS: The presence of two or more antibodies in addition to ICA or IAA conferred high risk (61%) for development of IDDM within 5 years of entry into the study and identified 89% of those who have developed IDDM on current follow-up. None of the relatives positive for ICA or IAA alone, in the absence of other antibody markers, have developed IDDM. Antibodies to islet antigens could both appear and disappear in follow-up samples obtained after entry into the study. The majority (60%) of young (< 16 years), sporadic cases of IDDM had multiple antibodies to islet antigens, but this proportion was lower in older patients (37%). CONCLUSIONS: A screening strategy based on the analysis of antibodies to multiple islet antigens can predict IDDM at high sensitivity and specificity in families, and such a strategy may also be applicable to identify young individuals in the general population with high disease risk. Since appearance of antibodies to different antigens occurs sequentially rather than simultaneously, accurate assessment of diabetes risk based on the presence of multiple antibodies will require follow-up over a number of years after the first evidence of islet autoimmunity.

Perinatal autoimmunity in offspring of diabetic parents. The German Multicenter BABY-DIAB study: detection of humoral immune responses to islet antigens in early childhood.

IDDM results from immune-mediated destruction of insulin-producing pancreatic beta-cells in individuals genetically susceptible for the disease. There is evidence that the 65-kDa isoform of GAD plays a critical role in the induction of autoimmune diabetes in NOD mice. In humans, it is still unclear when and to what beta-cell antigens autoreactive lymphocytes become activated during early disease. We conducted a prospective study from birth, BABY-DIAB, among children of mothers with IDDM or gestational diabetes or fathers with IDDM, and we investigated the temporal sequence of antibody responses to islet cells (ICA), insulin (IAA), GAD (GADA), and the protein tyrosine phosphatase IA-2/ICA512 (IA-2A). Of 1,019 children included at birth, we have currently followed 513 to the age of 9 months, 214 to the age of 2 years, and 37 to the age of 5 years. At birth, all antibody specificities were frequent in newborns of diabetic mothers but not fathers and are suggested to be transplacentally acquired because they are strongly correlated with antibody levels in their diabetic mothers. In early childhood, antibody levels were <99th percentile of control subjects in the majority of children. However, 37 children exhibited elevated antibody levels; these were most frequently detected at the age of 2 years. The antibody prevalence at age 2 years was 2.3% for ICA, 7% for IAA, 4.2% for GADA, and 2.8% for IA-2A (8.9% positive for at least one antibody). Children of diabetic fathers were positive for at least one antibody more frequently than were children of diabetic mothers (9 months of age: 8.5 vs. 3.6%; 2 years of age: 16.7 vs. 7.9%). There was no specific sequence in the appearance of positive autoantibodies, but 13 (35%) antibody-positive cases already had more than one ICA before the age of 2 years and 7 (19%) showed reactivity to three islet cell antigens before age 5 years. The presence of multiple antibodies confers high risk for the future development of diabetes; three of six children who exhibited positive antibody responses to all four antibodies tested and another child with two positive antibodies developed clinical diabetes at the ages of 13, 21, and 27 months and 5 years. We conclude that loss of tolerance to beta-cell autoantigens and appearance of autoimmune phenomena occur very early in life in individuals with genetic susceptibility for IDDM. Screening programs to identify candidates for disease-prevention therapies can therefore be focused on this young age-group, in whom the disease process may be less advanced and who may therefore be best suited to such therapies.

Identification and characterization of glima 38, a glycosylated islet cell membrane antigen, which together with GAD65 and IA2 marks the early phases of autoimmune response in type 1 diabetes.

Immunoprecipitating IgG autoantibodies to glutamic acid decarboxylase, GAD65, and/or a tyrosine phosphatase, IA2, are present in the majority of individuals experiencing pancreatic beta cell destruction and development of type 1 diabetes. Here we identify a third islet cell autoantigen, a novel 38-kD protein, which is specifically immunoprecipitated with sera from a subset of prediabetic individuals and newly diagnosed type 1 diabetic patients. The 38-kD autoantigen, named glima 38, is an amphiphilic membrane glycoprotein, specifically expressed in islet and neuronal cell lines, and thus shares the neuroendocrine expression patterns of GAD65 and IA2. Removal of N-linked carbohydrates results in a protein of 22,000 Mr. Glima 38 autoantibodies were detected in 16/86 (19%) of newly diagnosed patients, including three very young children, who had a rapid onset of disease, and in 6/44 (14%) of prediabetic individuals up to several years before clinical onset. The cumulative incidence of GAD65 and glima 38 antibodies in these two groups was 83 and 80%, respectively, and the cumulative incidence of GAD65, glima 38, and IA2 antibodies in the same groups was 91 and 84%, respectively. GAD65, IA2, and glima 38 represent three distinct targets of immunoprecipitating IgG autoantibodies associated with beta cell destruction and type 1 diabetes.

[Prediction of type I diabetes by antibody screening]. / Prädiktion des Typ-I-Diabetes durch Antikörper-Screening.

For the prediction of type I diabetes in first degree relatives of type I diabetics, a variety of laboratory methods are now available. Thus, screening for serum antibodies against the body's own insulin, islet cells and the enzyme glutamate decarboxylase, represents a simple and well-established routine examination used for early diagnosis. The combination of various parameters such as e.g. the age of the person at risk, antibody status (nature, number, combination or titer of the antibodies) and capacity for early insulin secretion following i.v. glucose loading, permits us to predict, with quite good accuracy, the risk years before there are any clinical manifestations. These successes of early diagnosis have led to new concepts of immunoprophylaxis for the prevention of type I diabetes. Thus, at the present time two highly promising studies involving the prophylactic administration of insulin or nicotinamide in persons at risk are underway in Germany, the results of which to date suggest that a new epoch of immunotherapeutic treatment of this disease may be in the offering.

No association of antibodies to glutamic acid decarboxylase and diabetic complications in patients with IDDM.

OBJECTIVE: To evaluate the association of antibodies to glutamic acid decarboxylase (GAD-ab) and diabetic complications (neuropathy, retinopathy, and nephropathy) in patients with insulin-dependent diabetes mellitus (IDDM). RESEARCH DESIGN AND METHODS: We examined the prevalence of GAD-ab (immunoprecipitation assay) and islet cell antibodies (ICAs) (indirect immunofluorescence) in a representative sample of IDDM patients (n = 146) with different disease duration (2-52 years, median 13.2 years). Of all patients characterized for the existence of diabetic complications, 56 of 146 had peripheral neuropathy, 24 of 142 had autonomic neuropathy, 67 of 141 had retinopathy, and 39 of 146 had nephropathy. RESULTS: GAD-ab (> 2 SD) were detected more frequently than ICA (> 5 Juvenile Diabetes Foundation units) in IDDM patients of different disease duration (GAD-ab+ 37% [54 of 146] vs. ICA+ 22% [32 of 146], P = 0.011; diabetes duration less than median: GAD-ab+ 47% vs. ICA+ 23%, P = 0.0046; diabetes duration greater than median: GAD-ab+ 27% vs. ICA+ 22%, P > 0.05). For GAD-ab and for ICA, respectively, no difference was observed in frequency of positivity or titers between patients with or without diabetic complications. CONCLUSIONS: Both GAD-ab and, to a lesser extent, ICA persist for a long time in several individuals. This persistence is not related to diabetic neuropathy or any other diabetic complication.

Alterations of lymphocyte subsets in children of diabetic mothers.

To investigate the impact of diabetic mothers on the maturation of the immune system in their offspring, immunophenotypic markers of major lymphocyte subpopulations were evaluated by two-colour flow cytometric analysis in 160 healthy children of diabetic mothers (100 with insulin-dependent diabetes mellitus (IDDM): 48 with gestational diabetes), including 22 neonates, 45 infants aged 8-12 months, 46 children aged 1-2 years, 29 children aged 3-6 years and 18 children aged 7-17 years. Results were compared with 21 neonates of healthy mothers from our hospital and with 110 paediatric subjects of a reference population. In neonates of diabetic mothers, percentages of total lymphocytes (p = 0.044), T and B lymphocytes (p = 0.004, respectively) were significantly decreased compared to our neonates of healthy mothers. By subdividing the group of neonates in offspring of mothers with IDDM (n = 15) or gestational diabetes (n = 7), differences compared to normal neonates were mainly observed in neonates of mothers with IDDM (T lymphocytes: p = 0.006; B lymphocytes: p = 0.008). In cord blood, 45.5% of neonates had antibodies to islet cells, insulin or glutamic acid decarboxylase, most likely transmitted through the placenta of the diabetic mother. No association was found between alterations of lymphocyte subsets and antibody-positivity in cord blood, nor was there any correlation of lymphocyte counts and mean HbA1 during pregnancy, maternal age at delivery, diabetes duration, or neonatal birth weight, respectively. Comparisons among age groups from newborn infants through adolescents revealed higher percentages of total lymphocytes and lower percentages of activated T cells in children of diabetic mothers compared to children of the reference population between the age of 1 to 6 years (67-73% of the cases above and 62-77% below the interquartiles of the reference range, respectively). No significant differences in lymphocyte subpopulations between children of mothers with IDDM diabetes and gestational diabetes have been detected. In addition, there were no abnormalities of lymphocyte subsets in children who are at high risk for the development of IDDM. In summary, we suggest that the observed changes in children of diabetic mothers may reflect a cellular immune reaction to the particular maternal environment, characterized by both an abnormal metabolic state and persisting autoimmunity in the affected mother.

Associations of anti-GAD antibodies with islet cell antibodies and insulin autoantibodies in first-degree relatives of type I diabetic patients.

Sera from 114 first-degree relatives of insulin-dependent diabetes mellitus (type I diabetes) patients and 81 healthy individuals living in Germany were analyzed for antibodies to rat brain glutamic acid decarboxylase (GAD-ab) using an immunoprecipitation assay. The determination of GAD-ab in the 81 islet cell antibody (ICA) and insulin autoantibody (IAA) negative healthy individuals established a normal range (mean +/- 2 SD); 2 healthy individuals (2.5%) possessed GAD-ab levels above this range, but became negative on follow-up. None of 86 ICA-/IAA- first-degree relatives had GAD-ab; whereas, 42.9% of 28 ICA+ and/or IAA+ relatives were positive for GAD-ab. Presence of GAD-ab was negatively correlated with IAA (P = 0.02) and positively with ICA (P = 0.0006). Follow-up samples were obtained from 25 of 28 ICA+ and/or IAA+ relatives with a mean (+/- SD) follow-up period of 20.6 +/- 12.1 months. In these 25 relatives, GAD-ab were positive in 70% ICA+/IAA-, 0% ICA-/IAA+, and 57.1% ICA+/IAA+ relatives in the first sample and in 57.1% ICA+/IAA-, 0% ICA-/IAA+, and 70% ICA+/IAA+ relatives in the last sample. GAD-ab, once detected, persisted in 9 of 11 GAD-ab+ relatives. Of the relatives, 2 converted to GAD-positivity, concomitant with the appearance of ICA, and 2 others lost GAD-ab during follow-up. Of the 28 ICA+ and/or IAA+ relatives, 6 progressed to overt type I diabetes on follow-up, and GAD-ab were detectable in 4 of these relatives.(ABSTRACT TRUNCATED AT 250 WORDS)

L-pilin variants of Neisseria gonorrhoeae MS11.

Phase- and antigenic variation of pilin expression in Neisseria gonorrhoeae is based on the genetic exchange between silent pilin genes (pilS) and the pilin expression locus (pilE). Similarly, the non-piliated L-variants of strain MS11, which show an increased resistance to certain antibiotics, are the result of recombination with the pilE locus. However, this recombination is atypical in that pilE(L) carries a tandem arrangement of a complete pilin gene and additional partial pilin genes under the control of the same pilE promoter. Since the two pilin gene copies are tandemly arranged and are often in the same translational frame, oversized pilin molecules are produced, which do not assemble into pili. The tandem gene copies introduced in a pilE(L) locus originate from silent loci where they are already joint. Upon reversion to the P+ phenotype the L-variants lose one pilin gene copy from the pilE(L) in a process reminiscent of the deletion events that otherwise lead to the formation of the non-revertible and non-piliated Pn mutants of MS11 gonococci. Thus deletion of pilin genes from pilE can be regarded as a third mechanism of pilin variation in gonococci.