Mean Antibody Levels Research Articles

Periodontopathogen‐ and Host‐Derived Immune Response in Acute Coronary Syndrome

Owing to molecular mimicry, periodontal pathogen carriage may result in a systemic cross-reactive immune response with the host. The analyses were performed to investigate if serum antibody levels to human heat shock protein 60 (HSP60) are associated with the antibody levels and salivary carriage of two periodontal pathogens, Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis, as well as with the dental status in patients with acute coronary syndrome (ACS). ACS patients (n = 141) were monitored at baseline when entering to hospital, and after 1 week, 3 months and 1 year. Periodontal status was recorded by dental radiographs, and A. actinomycetemcomitans and P. gingivalis were detected by PCR from saliva at baseline. Serum IgG and IgA antibody levels were determined at all time points. All antibody levels remained quite stable during the follow-up. Serum IgG-class antibody levels to A. actinomycetemcomitans and HSP60 had a strong positive correlation with each other at all time points (r∼0.4, P < 0.05). Mean serum IgG antibody levels to HSP60 were significantly higher in the A. actinomycetemcomitans IgG- and IgA-seropositive than in the seronegative patients, but did not differ between the pathogen carriers compared to the non-carriers. HSP60 antibody levels did not differ significantly between the edentulous, non-periodontitis and periodontitis patients. Despite the observed cross-reactivity in the systemic IgG-class antibody response to HSP60 and A. actinomycetemcomitans, the pathogen carriage in saliva or the periodontal status did not affect the HSP60 antibody levels in ACS patients.

ELISA measurement of specific non-antigen-bound antibodies to Aβ1-42 monomer and soluble oligomers in sera from Alzheimer's disease, mild cognitively impaired, and noncognitively impaired subjects

BackgroundThe literature contains conflicting results regarding the status of serum anti-Aβ antibody concentrations in Alzheimer's disease (AD). Reduced levels of these antibodies have been suggested to contribute to the development of this disorder. The conflicting results may be due to polyvalent antibodies, antibody "masking" due to Aβ binding, methodological differences, and/or small sample sizes. The objectives of this pilot study were to compare serum anti-Aβ antibody concentrations between AD, mild cognitive impairment (MCI), and elderly noncognitively impaired (NCI) subjects while addressing these issues, and to perform power analyses to determine appropriate group sizes for future studies employing this approach.MethodsSerum antibodies to Aβ1-42 monomer and soluble oligomers in AD, MCI, and NCI subjects (10/group) were measured by ELISA, subtracting polyvalent antibody binding and dissociating antibody-antigen complexes. Differences in mean antibody levels were assessed for significance with repeated measures ANOVA using restricted maximum likelihood estimation, using Tukey-Kramer tests and confidence intervals for multiple comparisons. Spearman's rank correlation was used to determine associations between anti-monomer and anti-oligomer antibody concentrations. Estimated sample sizes required to detect effects of various sizes were calculated.ResultsThere were no significant differences between groups for mean anti-Aβ antibody levels, although these tended to be higher in AD than NCI specimens. Estimated group sizes of 328 and 150 for anti-Aβ monomer and oligomer antibodies, respectively, would have been required for 80% power for significance at 0.05 for a 25% increase in the AD mean relative to the NCI mean. Serum antibody concentrations to Aβ monomer and oligomers were strongly associated (correlations: 0.798 for undissociated sera, 0.564 for dissociated sera). Antibody-antigen dissociation significantly increased anti-Aβ monomer but not anti-Aβ oligomer antibody levels.ConclusionsThe findings in this pilot study are consistent with relatively similar concentrations of specific, non-antigen-bound antibodies to Aβ1-42 monomer and soluble oligomers in AD, MCI, and NCI sera. The differences between groups for these antibodies would have required approximate group sizes of 328 and 150, respectively, for a high probability for statistical significance. These findings do not support the hypothesis that reduced levels of anti-Aβ antibodies might contribute to AD's pathogenesis.

Comparative Effect ofLactobacillus caseiand a Commercial Mangosteen Dietary Supplement on Body Weight Gain and Antibody Response to Newcastle Disease Virus Vaccine in Fighting Roosters

The aim of the present study was to compare the effect of Lactobacillus casei and a commercial mixed combination of fruit juice that included Garcinia mangostana fruit extract on body weight gain from 7 to 90 days of age, on the antibody response 23 days after vaccination against Newcastle disease virus (NDV), and on the mortality in fighting roosters. Fifty-four 7-day-old birds were randomly distributed into three groups (treated with L. casei, G. mangostana, and saline solution [LC, GM, and SS groups, respectively]) of 18 animals each; all birds were orally treated daily. At 60 and 90 days, the LC group showed the highest body weight gain compared with the other two groups (P<.01). The mean levels of antibody to NDV were significantly higher in the GM group compared with the LC and SS groups (P<.05). Throughout the study the percentages of mortality were 5.55%, 0%, and 22.22% for the LC, GM, and SS groups, respectively. The results indicate that L. casei and the commercial mangosteen dietary supplement intake, compared with the control group, induce beneficial effects in fighting roosters--L. casei on weight gain and the commercial mixed combination of fruit juice with G. mangostana fruit extract on humoral immune response--and both showed none or very low mortality.

Follow-up of pregnant women exposed to chicken pox: an audit of relationship between level of antibody and development of chicken pox

The purpose of this study was to validate through natural exposure a cut-off level of varicella zoster IgG as protective against infection with varicella zoster virus (VZV). Laboratory testing to determine VZV immune status of pregnant women exposed to varicella is recommended. Quantitative assays are now available which are sensitive and specific. More than 200 consecutive requests for screening in pregnant patients with recent varicella contacts were followed-up by questionnaire. DiaSorin LIAISON and VZV time resolved fluorescence immuno assay (VZV TRFIA) were used to measure VZV antibody level. One hundred fifty out of 209 (72%) questionnaires were returned; 14 patients developed varicella, 129 did not and seven were not known. Patients who had been given VZIG and developed varicella on follow-up had a mean antibody level before VZIG of 28 mIU/ml and 62 mIU/ml, by LIAISON and TRFIA, respectively. The mean IgG level of those that did not develop varicella was 885 and 866 mIU/ml by LIAISON and TRFIA, respectively. Those with levels <100 mIU/ml were more likely to develop chicken pox than those with levels >100 mIU/ml (relative risk of 10.4 for LIAISON and 8.8 for TRFIA). On the basis of the relatively small numbers in this study, quantitative assays, using a 100mIU/ml cut-off, can differentiate between those who are susceptible and those who are protected against exposure, however follow-up studies should include sampling for VZV DNA and IgM.

High serum levels of rheumatoid factor and anti-phosphatidylserine antibody in patients with ischemic heart disease.

Immunopathological and inflammatory processes play important roles in the initiation and development of Ischemic Heart Disease (IHD). The aim of this study was to evaluate the serum levels of several autoantibodies including rheumatoid factor (RF), anti-nuclear antibodies (ANA), anti-small nuclear ribonucleoprotein (anti-Sm), anti-phosphatidylserine (anti-PS) and anti-cardiolipin (anti-CL) antibodies in patients with IHD. A total of 120 patients with IHD with acute myocardial infarction (AMI; n=60) or unstable angina (UA; n=60) and 60 sex- and age-matched healthy subjects were enrolled in this study. Serum samples of participants were tested for the ANA, anti-Sm, anti-PS and anti-CL antibodies by ELISA. Serum level of RF was measured by a turbidometric method. The mean serum levels of RF and anti-PS antibodies in AMI group and UA group were significantly higher than those observed in the control group (p<0.0001). The mean serum levels of RF and anti-PS antibodies in AMI patients were significantly higher than the UA group (p<0.01 and p<0.001, respectively). The mean serum levels of RF in men with AMI or UA diseases were significantly higher as compared to healthy control men (p<0.0001 and p<0.003, respectively). The differences of the serum levels of ANA, anti-Sm and anti-CL antibodies were not significant between AMI, UA and the control groups. There was no difference in the serum levels of RF, ANA, anti-Sm, anti-PS or anti-CL antibodies in patients with traditional risk factors, including hypertension, dyslipidemia, diabetes and smoking, and those without a certain risk factor. Higher serum levels of RF and anti-PS antibody in patients with IHD may be considered as independent risk factors for IHD.

Tetanus antibody in Nigerians living with HIV/AIDS: A preliminary report

The aim of this study is to investigate the need for anti-tetanus immunisation in Nigerians living with HIV/AIDS by quantifying antibody to tetanus organism in them. Both symptomatic and asymptomatic consenting Nigerians positive for HIV infection and aged 15 years and above were included in the study. Apparently healthy age- and sex-matched subjects were enrolled as controls. Immunisation history was recorded in all participants. The PCV, WBC, platelet and CD4+ cell counts were done on automated counter. Serum levels of antibody to tetanus were quantitated using standard ELISA method. There was no significant difference (t = 0.138, p = 0.89) in the mean serum levels of antibody to tetanus in patients with HIV/AIDS (0.5 ± 0.86 IU/mL) when compared with the controls (0.46 ± 0.52 IU/mL). About 85.7% (36/42) of patients with HIV/AIDS had protective tetanus antibody and only six (14.3%) had non-protective antibody levels. In patients with CD4+ T lymphocytes of 200 cells/µL, it was 0.53 ± 0.53 IU/mL. The difference was not statistically significant (t = 0.1, p = 0.918). The majority of our patients presented in advanced stage with 69% of them having CD4+ T lymphocytes < 200 cell/µL. This study found a significant number of Nigerians with HIV/AIDS having protective levels of antibody to tetanus in their sera. We therefore suggest continue efforts at improving on the National Programme on Immunisation, as immunisation in patients with HIV infection may not yield adequate responses and may be fraught with the risk of increase in viral replication.

Gastrointestinal sensitivity to soy and milk proteins in patients with IgA nephropathy

sensitivity to food antigens has been postulated as a contributing factor to the pathogenesis of IgA nephropathy (IgAN). in this study we used a recently developed mucosal patch technique to evaluate rectal mucosal sensitivity to soy and cow's milk (CM) proteins in IgAN patients (n = 28) compared to healthy subjects (n = 18). The rectal mucosal production of nitric oxide (NO) and release of myeloperoxidase (MPO) and eosinophil cationic protein (ECP) were measured. Serum samples were analyzed for IgA and IgG antibodies to alpha-lactalbumin, beta-lactoglobulin, casein and soy. 14 of 28 (14/28) patients experienced a rectal mucosal reaction, measured by increased NO and/or MPO levels, upon rectal challenge with soy and/or cow's milk proteins. The levels of IgG antibodies to alpha-lactalbumin, beta-lactoglobulin and casein were significantly higher in CM sensitive as compared with non-sensitive IgAN patients, whereas the mean serum levels of IgA antibodies were similar. No differences were seen in serum levels of IgA or IgG antibodies to soy. it is concluded that approximately half of our IgAN patients have a rectal mucosal sensitivity to soy or CM, and that an immune reactivity against antigens may be involved in the pathogenesis of IgAN in this subgroup of patients.

Stenotrophomonas maltophilia in Cystic Fibrosis

Stenotrophomonas maltophilia is one of the more common multidrug-resistant organisms isolated from the respiratory tract of patients with cystic fibrosis (CF), but the effect of chronic S. maltophilia infection on CF lung disease is unknown. To determine the impact of chronic S. maltophilia infection on lung disease in CF. We developed a serologic assay specific for S. maltophilia and in a cross-sectional study, measured serum antibodies to S. maltophilia in patients with CF to determine if a definition of chronic S. maltophilia isolation based on culture results corresponded to an immunologic response (serologic study). We then used this validated definition to examine the effect of chronic S. maltophilia on the severity of lung disease in a retrospective cohort study using the Toronto CF Database from 1997-2008 (cohort study). Serum antibody levels to S. maltophilia were measured in 179 patients with CF. Patients with chronic S. maltophilia had significantly higher mean antibody levels to S. maltophilia flagellin (P < 0.0001) and whole cell (P = 0.0004) compared with patients with intermittent or no S. maltophilia. The cohort study included 692 patients with an average follow-up of 8.3 years. In an adjusted log linear model, patients with chronic S. maltophilia infection had a significantly increased risk of pulmonary exacerbation requiring hospitalization and antibiotics compared with patients who had never had S. maltophilia (relative risk = 1.63; P = 0.0002). Chronic S. maltophilia infection in patients with CF is associated with a specific immune response to this organism and is an independent risk factor for pulmonary exacerbations.

Industrial hygiene assessment of reticuloendotheliosis viruses exposure in the poultry industry

Reticuloendotheliosis viruses (REV) are a group of retroviruses like avian leukosis/sarcoma viruses (ALSV) that naturally infect and cause cancers in chickens. We recently found that ALSV antibody levels were associated with job tasks in the poultry industry. The objectives of this study are to examine whether a similar association can be found with REV antibody levels and to examine the correlation between REV and ALSV antibody levels. Relative risk was estimated comparing REV antibody levels of 45 poultry workers with those of 44 controls. The expected mean antibody level was predicted for the association with employment by a generalized linear model. Correlation coefficient was measured between ALSV and REV antibody levels. REV antibody levels were significantly higher in poultry workers than in control subjects and were associated with gender and employment conditions, especially employment duration. The relative risk was significantly higher for some job categories. A significant correlation was observed between REV and ALSV antibody levels, which was strong among poultry workers, but weak among the control subjects. Antibody levels can be validly used to identify certain job tasks associated with high risk of exposure to REV in the workplace, and the practical implication is recommendations for protection at these job tasks. Importantly, in situations where there is exposure to multiple pathogens in the workplace, the analysis of antibody levels of one pathogen may sufficiently represent exposure to the other correlated pathogens. This suggested exposure assessment may hold true for pathogens with a similar route of transmission.

Phase 1 safety and immunogenicity trial of the Plasmodium falciparum blood-stage malaria vaccine AMA1-C1/ISA 720 in Australian adults

A Phase 1 trial was conducted in malaria-naïve adults to evaluate the recombinant protein vaccine apical membrane antigen 1-Combination 1 (AMA1-C1) formulated in Montanide® ISA 720 (SEPPIC, France), a water-in-oil adjuvant. Vaccinations were halted early due to a formulation issue unrelated to stability or potency. Twenty-four subjects (12 in each group) were enrolled and received 5 or 20μg protein at 0 and 3 months and four subjects were enrolled and received one vaccination of 80μg protein. After first vaccination, nearly all subjects experienced mild to moderate local reactions and six experienced delayed local reactions occurring at Day 9 or later. After the second vaccination, three subjects experienced transient grade 3 (severe) local reactions; the remainder experienced grade 1 or 2 local reactions. All related systemic reactogenicity was grade 1 or 2, except one instance of grade 3 malaise. Anti-AMA1-C1 antibody responses were dose dependent and seen following each vaccination, with mean antibody levels 2–3 fold higher in the 20μg group compared to the 5μg group at most time points. In vitro growth-inhibitory activity was a function of the anti-AMA1 antibody titer. AMA1-C1 formulated in ISA 720 is immunogenic in malaria-naïve Australian adults. It is reasonably tolerated, though some transient, severe, and late local reactions are seen.

Boosting antibody responses toPlasmodium falciparummerozoite antigens in children with highly seasonal exposure to infection

Longitudinal cohort studies are important to describe the dynamics of naturally acquired antibody response profiles to defined Plasmodium falciparum malaria antigens relative to clinical malaria episodes. In children under 7 years of age in The Gambia, serum IgG responses were measured to P. falciparum merozoite antigens AMA1, EBA175, MSP119, MSP2 and crude schizont extract, over a 10-month period. Persistence of antibody responses was measured in 152 children during the dry season when there was virtually no malaria transmission, and 103 children were monitored for new episodes of clinical malaria during the subsequent wet season when transmission occurred. Children who experienced clinical malaria had lower antibody levels at the start of the study than those who remained free from malaria. Associations between dry season antibody persistence and subsequent wet season antibody levels suggested robust immunological memory responses. Mean antibody levels to all antigens were elevated by the end of the wet season in children who experienced clinical malaria; each of these children had a boosted antibody response to at least one antigen. In all children, antibody avidities were lower against MSP2 than other antigens, a difference that did not change throughout the study period or in relation to clinical malaria episodes.

Association of Epstein Barr Virus Infection (EBV) with Breast Cancer in Rural Indian Women

IntroductionBreast cancer is the most common malignancy affecting females worldwide but conventional risk factors are able to explain only a small proportion of these cases. A possible viral etiology for breast cancer has been proposed and Epstein-Barr Virus (EBV) is a widely researched candidate virus. The aim of the present study, first one of its kind from India, was to determine if there is a greater association of EBV infection with breast cancer patients as compared to patients with benign breast diseases.MethodsWe looked for expression of Epstein-Barr Virus Nuclear Antigen-1 (EBNA-1) in breast cancer tissue specimens by employing immunohistochemistry (IHC). We also measured levels of anti-EBNA-1 Immunoglobulin (IgG) antibodies in stored sera of these patients using commercial Enzyme linked Immunosorbent Assay (ELISA) kit. Patients with benign breast diseases were used as a comparison group for both immunohistochemical and serological analysis.Results58 cases of malignant breast disease and 63 of benign breast disease (controls) were included in the study. Using manufacturer determined cut-off of 3 IU/ml, 50/55 tested (90.9%) cases and 27/33 tested (81.8%) controls were seropositive for anti-EBNA-1 IgG. Mean antibody levels were significantly higher for cases (54.22 IU/ml) as compared to controls (18.68 IU/ml). IHC for EBNA-1 was positive in 28/51 cases (54.9%). No IHC positivity was noted in the tested 30 controls. Our results show that EBNA-1 expression is seen in a significant proportion of breast cancer tissue specimens from rural India and as compared to patients with benign breast diseases these patients also have a higher immunological response against EBNA-1.

Healthcare Worker Occupation and Immune Response toPneumocystis jirovecii

The reservoir and mode of transmission of Pneumocystis jirovecii remain uncertain. We conducted a cross-sectional study of 126 San Francisco General Hospital staff in clinical (n = 103) and nonclinical (n = 23) occupations to assess whether occupational exposure was associated with immune responses to P. jirovecii. We examined antibody levels by ELISA for 3 overlapping fragments that span the P. jirovecii major surface glycoprotein (Msg): MsgA, MsgB, and MsgC1. Clinical occupation participants had higher geometric mean antibody levels to MsgC1 than did nonclinical occupation participants (21.1 vs. 8.2, p = 0.004); clinical occupation was an independent predictor of higher MsgC1 antibody levels (parameter estimate = 0.89, 95% confidence interval 0.29-1.48, p = 0.003). In contrast, occupation was not significantly associated with antibody responses to either MsgA or MsgB. Healthcare workers may have occupational exposure to P. jirovecii. Humans may be a reservoir for P. jirovecii and may transmit it from person to person.

Serological response to tick-borne encephalitis (TBE) vaccination in the elderly – results from an observational study

Background: In the elderly, the incidence of tick-borne encephalitis (TBE) is higher than in younger individuals. At the same time, the responsiveness of the elderly to vaccination may be decreased. Product information for TBE vaccines therefore recommends determining antibody response after two of the three doses required for primary immunization in persons over 60. Objective: To determine the proportion of persons aged 60 years or older with insufficient antibody response after administration of two doses of TBE vaccine. Methods: A retrospective analysis of TBE-specific antibody levels as determined by Immunozym® ELISA in serum samples of 185 vaccinees > 60 years of age after the first two of the three vaccinations required for primary immunisation. Patients received either FSME-IMMUN Adult or Encepur® Adults at one vaccination centre in the Czech Republic. In a subset of 80 vaccinees, two additional ELISAs and a neutralization test (NT) were performed. Results: Overall, 33 of the 185 individuals (18%) included in the Immunozym analysis had antibody concentrations below putative protective levels after two doses. Geometric mean concentrations and seropositivity rates were higher in individuals vaccinated with FSME-IMMUN than in those vaccinated with Encepur®. While the differences in mean antibody levels and/or seropositivity rates in ELISAs for the Neudörfl strain (used in FSME-IMMUN) were significant, no significant differences were obtained for Enzygnost, which uses the Karlsruhe strain (used in Encepur). Conclusions: After two doses of TBE vaccine, one in five persons aged 60 years or older may be without protective antibodies, confirming the importance of testing the antibody response after the second vaccination and administering an additional dose in the event of insufficient response.

Pretransplant IgG antibodies to polyoma BK virus in pediatric renal transplants

We retrospectively measured IgG antibody levels to BKV in pretransplant sera and compared levels in children who developed BK viremia to a control group who remained free of infection after transplantation. Sera from 45 renal transplant patients were available for analysis (BK viremia = 23, controls = 22). Serum BKV PCR levels ranged from 3400 to 6.5 million DNA copies/mL (mean +/- s.d.: 978K +/- 1.77 million) and were highest in patients with BK nephritis (p = 0.007). Overall, 35% of children with BK viremia were BKV-seronegative vs. 9% of children in control group (p = 0.04), but mean antibody levels were similar between viremic and control patients (p = 0.15). However, children who developed viremia later than six months post-transplantation had significantly lower antibody levels compared with controls (p = 0.004) and patients with early viremia (p = 0.007), and may represent de novo infection or reinfection, rather than recurrence of latent infection. Pretransplant antibody status was significantly associated with subsequent development of BK viremia. Although our findings identified possible factors for developing BK viremia, there was sufficient overlap of both seropositive status and antibody levels among viremic patients and the control group to question the clinical utility of pretransplant IgG antibodies.

Long‐Term Serologic Responses to thePneumocystis jiroveciiMajor Surface Glycoprotein in HIV‐Positive Individuals With and WithoutP. jiroveciiInfection

The immune responses to Pneumocystis jirovecii major surface glycoprotein (Msg) in individuals with human immunodeficiency virus (HIV) infection are poorly understood. We examined the sequential serologic responses to recombinant Msg carboxyl terminus fragments (MsgC1, MsgC3, MsgC8, and MsgC9) by enzyme-linked immunosorbent assay in a cohort of individuals with HIV infection for the 5.5 years before death and autopsy. Analyses included mean antibody levels by status at death (Pneumocystis pneumonia, P. jirovecii colonization, or neither), factors associated with high antibody levels, and antibody responses before and after active Pneumocystis pneumonia. Patients who died from Pneumocystis pneumonia had higher levels of antibody to MsgC8 than did patients who died from other causes. Previous episode of Pneumocystis pneumonia, geographic location, and age were independent predictors of high levels of anitbodies to most or all Msgs. Failure to take Pneumocystis pneumonia prophylaxis was associated with high levels of antibody to MsgC1. Patients who developed and recovered from active Pneumocystis pneumonia during the study exhibited an increase in serum antibody levels that persisted for months after the infection, whereas patients who developed another acquired immunodeficiency syndrome-defining illness did not. Serum antibodies to Msgs are important markers of P. jirovecii infection in patients with HIV infection and are influenced by host and environmental factors in complex ways.

Antibody response to Pseudomonas aeruginosa in children with cystic fibrosis

Cystic fibrosis (CF) is the most frequent life threatening autosomal recessive disease in white subjects. The primary cause of morbidity and mortality in children with CF is chronic pulmonary infection, mainly caused by Pseudomonas aeruginosa. The purpose of this study was to assess the value of the measurement of antibodies to P. aeruginosa in diagnosing lung infection by the bacteria in CF patients. We assessed P. aeruginosa antibody titers in CF patients from Rio de Janeiro, Brazil, using cell lysate antigens as well as recombinant PcrV, a Type III Secretion System protein. Sputum (more than 70% of the specimens) or oropharyngeal swabs were obtained whenever patients were regularly followed for their pulmonary disease. Blood samples were obtained with an average interval of 6 months for a period of 2 years. The ELISA cut-offs were assigned as the positive 95% confidence interval of the mean antibody levels from non-fibrocystic controls. Our data showed that most CF patients (81%) of whom were not chronically infected by P. aeruginosa (Groups I and II), had their first serology positive for rPcrV. Cell-lysate ELISA was able to detect P. aeruginosa antibodies before positive culture in the first serum sample of 44% of the patients from Groups I and II. When serum reactivity to rPcrV and cell lysate were combined, 94% of CF patients from Groups I and II (n = 16) had the first serology positive for P. aeruginosa over a mean time of 20 months before the first isolation of P. aeruginosa. In conclusion, longitudinal P. aeruginosa serology should become part of respiratory care follow-up, in conjunction with other lung parameter functions.

On the relationship between mean antibody level, seroprotection and clinical protection from influenza

For many vaccines the amount of antibodies induced has a positive correlation with the likelihood of clinical protection from disease. Mean antibody level is therefore frequently used as a serological surrogate endpoint for vaccine efficacy. In addition, a dichotomous surrogate endpoint is often defined: seroprotection. We explore the relationship between mean antibody level, seroprotection and clinical protection from influenza, using a simple statistical model. The model reveals that the relationship depends not only on the mean but also on the dispersion of the antibody levels, the threshold for clinical protection and the clinical protection curve. The consequences for the interpretation of mean antibody levels and seroprotection rates in terms of clinical protection from influenza are discussed.

Long-term persistence of anti-HPV-16 and -18 antibodies induced by vaccination with the AS04-adjuvanted cervical cancer vaccine: Modeling of sustained antibody responses

Objectives Strong and sustained HPV-16 and -18 antibody responses have been observed in previously unexposed women aged 15–25 years vaccinated with the AS04-adjuvanted HPV-16/18 L1 virus-like particle vaccine. While awaiting the extended results of ongoing trials, our objective was to predict the long-term persistence of anti-HPV-16/18 antibodies in vaccinees by applying three statistical models using immunogenicity data from vaccinated women with serum samples collected up to 6.4 years after first vaccination. Two different data lock-points (up to 5.5 years and up to 6.4 years) were used to assess the robustness of the models. Methods Three statistical models were applied to estimate the long-term persistence of anti-HPV-16/18 antibodies in 393 women vaccinated with the AS04-adjuvanted HPV-16/18 vaccine. Individual antibody levels for each study participant at each timepoint up to 6.4 years were input to previously published power-law and modified power-law models. The power-law model estimates antibody decay over time. The modified power-law model takes into account both antibody persistence over time and immune memory. A third model, the piece-wise model, fits the data based on three different non-overlapping intervals (between Months 7 and 12, Months 12 and 21, and over 21 months), corresponding to the observed decay of vaccine-induced antibodies. Results HPV-16 and -18 antibodies peaked at Month 7 and gradually plateaued at Months 18–24 and remained stable through 6.4 years. Mean antibody levels at the last timepoint were several fold higher than those associated with natural infection. All three models predict that HPV-16 and -18 mean antibody levels will remain well above those associated with natural infection for at least 20 years, when using data from 5.5 as well as 6.4 years' follow-up. Predictions are similar for the modified power-law model and improve with longer follow-up for both the power-law and the piece-wise models. Conclusions Vaccination with the AS04-adjuvanted HPV-16/18 vaccine is predicted to provide long-term persistence for both HPV-16 and -18 antibodies, independent of the statistical model applied. Model predictions are based on conservative mathematical assumptions. Since the input of longer term data of up to 6.4 years showed an improved profile compared with that for data up to 5.5 years, the predictions of antibody persistence based on population means are conservative when predicting that antibody levels will remain well above levels induced by natural infection for 20 years.

Seroprevalence of IgG Antibodies to Pertussis Toxin in the First Grade Medical Students in Hamedan, Iran

Background: Pertussis is a highly communicable disease of the respiratory tract caused by Bordetella pertussis. Neither natural disease nor vaccination provide complete or life long immunity against reinfection or disease. Protection against typical disease is immeasurable after 12 years. Coughing adolescents and adults currently are the major reservoir for B. pertussis and are the usual source for “index cases” in infants and children. Without natural reinfection with B. pertussis or repeated booster vaccination, adolescent and adults are susceptible to clinical disease if exposed. The aim of this study was to assess the B. pertussis antibody levels in the medical students of Hamedan University of Medical Sciences. Methods: One hundred sixty-three first grade medical students with no history of chronic respiratory infection and immunodeficiency were selected. Serum samples were collected from them and analyzed for anti-pertussis toxin (PT) IgG antibodies by enzyme-linked immunosorbent assay (ELISA). Antibody titers were calculated using reference line methodology. Anti-PT titers more than 24 g/ml were considered to be positive. Results: The mean age of cases was 19.48 year. Out of 163 cases, 47.6 percent had positive antibody titer and the mean of antibody titer was 71.72 g/ml. 42% of females and 54% of males had positive antibody titers. Thirty-three percent of age group 21yr had positive antibody level. The mean of antibody level in male was 84.07, in female was 58.9 u/ml. Antibody levels were not statistically significantly different between males and females. The mean antibody level in age group 21 yr was 49.269 g/ml. There were no statistically significant differences between age groups in the proportion of antibody levels. Conclusion: The high rates of seropositivity in our study population indicate previous infection, which are a threat to infants who have not completed primary immunisation. In this respect, booster vaccination for adolescents and adults is recommended.