Investigated Antibody Responses Research Articles

Dynamic Antibody Response: a Biomarker for COVID-19.

Novel coronavirus disease 2019 (COVID-19) is the cause of the third pneumonia-like outbreak of coronaviruses in humans during the 21st century. The status of the host immune system is a critical factor that affects the severity and outcomes of COVID-19. In particular, antibody responses are an indicator of the anti-viral defense; so, a delayed or inappropriate induction of these responses would correlate with a defect in the viral clearance. This is a rapid synthesis of literature investigating antibody responses in patients with the severe acute respiratory syndrome (SARS) and COVID-19. Lessons learned from severe acute respiratory syndrome (SARS), along with the direct evidence of antibody responses in COVID-19, pose the potentials of dynamic antibody responses for screening and prognostic purposes in COVID-19. Also, neutralizing antibodies extracted from recovered patients and monoclonal antibodies targeting cytokines offer therapeutic support for COVID-19. Altogether, the dynamics of antibody responses help to determine the effectiveness of treatments for COVID-19. Of note, it might be helpful for the evaluation of the efficacy of immunotherapy and vaccination - the dreams for the future of COVID-19. Further studies are necessary to investigate the possibility and efficacy of antibody extraction from animal subjects. Finally, numerous factors affect antibody response such as race, nutrition status, and virus mutations in viral infections, which need to be considered in the context of COVID-19.

Antibody Responses 8 Months after Asymptomatic or Mild SARS-CoV-2 Infection.

Waning humoral immunity in coronavirus disease patients has raised concern over usefulness of serologic testing. We investigated antibody responses of 58 persons 8 months after asymptomatic or mildly symptomatic infection with severe acute respiratory syndrome coronavirus 2. For 3 of 4 immunoassays used, seropositivity rates were high (69.0%–91.4%).

Isolation of potent SARS-CoV-2 neutralizing antibodies and protection from disease in a small animal model.

Countermeasures to prevent and treat coronavirus disease 2019 (COVID-19) are a global health priority. We enrolled a cohort of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-recovered participants, developed neutralization assays to investigate antibody responses, adapted our high-throughput antibody generation pipeline to rapidly screen more than 1800 antibodies, and established an animal model to test protection. We isolated potent neutralizing antibodies (nAbs) to two epitopes on the receptor binding domain (RBD) and to distinct non-RBD epitopes on the spike (S) protein. As indicated by maintained weight and low lung viral titers in treated animals, the passive transfer of a nAb provides protection against disease in high-dose SARS-CoV-2 challenge in Syrian hamsters. The study suggests a role for nAbs in prophylaxis, and potentially therapy, of COVID-19. The nAbs also define protective epitopes to guide vaccine design.

Antibodies to measles, mumps, and rubella virus in Thai children after two-dose vaccination at 9 months and 2.5 years: A longitudinal study

IntroductionThailand changed the schedule of childhood measles–mumps–rubella (MMR) vaccination in 2014, moving the second dose from the age of 6 years to 2.5 years. There are currently no data on antibody responses to the MMR vaccine since this recommendation. Material and methodsWe investigated antibody responses in a cohort of children who received two doses of MMR vaccine at the ages of 9 months and 2.5 years that was originally established to evaluate antibody levels to Bordetella pertussis antigens (ClinicalTrials.gov no. NCT02408926). Infants were born to mothers who previously received tetanus–diphtheria–acellular pertussis vaccine at 27–36 weeks of gestation. Anti-measles, -mumps, and -rubella virus IgG levels were measured at birth (cord blood) and the ages of 2 and 7 months (before the first MMR vaccination); 18 and 24 months (9 and 15 months, respectively, after the first dose); and 36 months (6 months after the second dose) using commercially available enzyme-linked immunosorbent assay kits. ResultsAt 7 months of age, 96.2%, 99.6%, and 98.8% of infants had no protection against measles, mumps, and rubella, respectively. Levels of antibody against all three antigens increased significantly after the first but not the second dose. At 6 months after two-dose vaccination, 97.4%, 84.8%, and 78.7% of children remained seroprotected against measles, mumps, and rubella, respectively. ConclusionsMaternally derived antibodies to measles, mumps, and rubella virus disappeared by the age of 7 months in Thai children. Two-dose MMR vaccination at 9 months and 2.5 years of age induced robust immune responses against these viruses.

Evaluation of a COVID-19 IgM and IgG rapid test; an efficient tool for assessment of past exposure to SARS-CoV-2

ABSTRACT COVID-19 is the most rapidly growing pandemic in modern time, and the need for serological testing is most urgent. Although the diagnostics of acute patients by RT-PCR is both efficient and specific, we are also crucially in need of serological tools for investigating antibody responses and assessing individual and potential herd immunity. We evaluated a commercially available test developed for rapid (within 15 minutes) detection of SARS-CoV-2-specific IgM and IgG by 29 PCR-confirmed COVID-19 cases and 124 negative controls. The results revealed a sensitivity of 69% and 93.1% for IgM and IgG, respectively, based solely on PCR-positivity due to the absence of a serological gold standard. The assay specificities were shown to be 100% for IgM and 99.2% for IgG. This indicates that the test is suitable for assessing previous virus exposure, although negative results may be unreliable during the first weeks after infection. More detailed studies on antibody responses during and post infection are urgently needed.

Antibody Responses to Immunization With HCV Envelope Glycoproteins as a Baseline for B-Cell–Based Vaccine Development

We investigated antibody responses to hepatitis C virus (HCV) antigens E1 and E2 and the relevance of animal models for vaccine development. We compared antibody responses to vaccination with recombinant E1E2 complex in healthy volunteers, non-human primates (NHPs), and mice. We analyzed 519 serum samples from participants in a phase 1 vaccine trial(ClinicalTrials.gov identifier NCT00500747) and compared them with serum or plasma samples from C57BL/6J mice (n= 28) and rhesus macaques (n= 4) immunized with the same HCV E1E2 antigen. Blood samples were collected at different time points and analyzed for antibody binding, neutralizing activity, and epitope specificity. Monoclonal antibodies from the immunized NHPs were isolated from single plasmablasts and memory B cells, and their immunogenetic properties were characterized. Antibody responses of the volunteers, NHPs, and mice to the non-neutralizing epitopes on the E1 N-terminus and E2 hypervariable region 1 did not differ significantly. Antibodies from volunteers and NHPs that neutralized heterologous strains of HCV primarily interacted with epitopes in the antigen region 3. However, the neutralizing antibodies were not produced in sufficient levels for broad neutralization of diverse HCV isolates. Broadly neutralizing antibodies similar to the human VH1-69 class antibody specific for antigen region 3 were produced in the immunized NHPs. In an analysis of vaccinated volunteers, NHPs, and mice, we found that recombinant E1E2 vaccine antigen induces high-antibody titers that are insufficient to neutralize diverse HCV isolates. Antibodies from volunteers and NHPs bind to the same neutralizing epitopes for virus neutralization. NHPs can therefore be used as a preclinical model to develop HCV vaccines. These findings also provide useful baseline values for development of vaccines designed to induce production of neutralizing antibodies.

A Third Dose of Measles-Mumps-Rubella Vaccine to Improve Immunity Against Mumps in Young Adults.

Waning of vaccine-induced immunity is considered to play a central role in the reemergence of mumps among vaccinated young adults. The aim of the present study was to investigate antibody responses and safety of a third dose of measles-mumps-rubella vaccine (MMR-3) in 150 young adults. Antibody levels were related to a surrogate of protection based on preoutbreak serum antibody levels in 31 persons with and 715 without serological evidence of mumps. Mumps virus-specific immunoglobulin G (IgG) antibody responses and mumps virus-neutralizing antibody responses (based on the focus-reduction neutralizing test) against both the Jeryl Lynn mumps virus vaccine strain (hereafter, the "vaccine strain") and the MuVi/Utrecht.NLD/40.10 outbreak strain (hereafter, the "outbreak strain") were determined, and vaccine safety was evaluated. Four weeks following MMR-3 receipt, levels of IgG, anti-vaccine strain, and anti-outbreak strain antibodies increased by a factor of 1.65, 1.34, and 1.35, respectively. Although antibody levels decreased 1 year later, they were still above the baseline level by a factor of 1.37, 1.15, and 1.27, respectively. Based on the surrogate protective antibody cutoff, significantly more participants were protected against mumps virus infection up to 1 year after vaccination (ie, they had antibody levels above the presumed threshold for herd immunity). MMR-3 receipt increased antibody levels that may protect against mumps virus infection for longer than previously assumed and is expected to be a good and safe intervention for controlling a mumps outbreak. 2016-001104-36; NTR5911.

ZIKV-Specific NS1 Epitopes as Serological Markers of Acute Zika Virus Infection

Zika virus (ZIKV) infections have reemerged as a global health issue due to serious clinical complications. Development of specific serological assays to detect and differentiate ZIKV from other cocirculating flaviviruses for accurate diagnosis remains a challenge. We investigated antibody responses in 51 acute ZIKV-infected adult patients from Campinas, Brazil, including 7 pregnant women who later delivered during the study. Using enzyme-linked immunosorbent assays, levels of antibody response were measured and specific epitopes identified. Several antibody-binding hot spots were identified in ZIKV immunogenic antigens, including membrane, envelope (E) and nonstructural protein 1 (NS1). Interestingly, specific epitopes (2 from E and 2 from NS1) strongly recognized by ZIKV-infected patients' antibodies were identified and were not cross-recognized by dengue virus (DENV)-infected patients' antibodies. Corresponding DENV peptides were not strongly recognized by ZIKV-infected patients' antibodies. Notably, ZIKV-infected pregnant women had specific epitope recognition for ZIKV NS1 (amino acid residues 17-34), which could be a potential serological marker for early ZIKV detection. This study identified 6 linear ZIKV-specific epitopes for early detection of ZIKV infections. We observed differential epitope recognition between ZIKV-infected and DENV-infected patients. This information will be useful for developing diagnostic methods that differentiate between closely related flaviviruses.

Vaccination of horses with Lyme vaccines for dogs induces short-lasting antibody responses.

Borrelia burgdorferi can induce Lyme disease. Approved Lyme vaccines for horses are currently not available. In an effort to protect horses, veterinarians are using Lyme vaccines licensed for dogs. However, data to assess the response of horses to, or determine the efficacy of this off-label vaccine use are missing. Here, antibodies against outer surface protein A (OspA), OspC, and OspF were quantified in diagnostic serum submissions from horses with a history of vaccination with canine Lyme vaccines. The results suggested that many horses respond with low and often short-lasting antibody responses. Subsequently, four experimental vaccination trials were performed. First, we investigated antibody responses to three canine vaccines in B. burgdorferi-naïve horses. One killed bacterin vaccine induced antibodies against OspC. OspA antibodies were low for all three vaccines and lasted less than 16weeks. The second trial tested the impact of the vaccine dose using the OspA/OspC inducing bacterin vaccine in horses. A 2mL dose produced higher OspA and OspC antibody values than a 1mL dose. However, the antibody response again quickly declined, independent of dose. Third, the horses were vaccinated with 2 doses of a recombinant OspA vaccine. Previous vaccination and/or environmental exposure enhanced the magnitude and longevity of the OspA antibody response to about 20weeks. Last, the influence of intramuscular versus subcutaneous vaccine administration was investigated for the recombinant OspA vaccine. OspA antibody responses were not influenced by injection route. The current work highlights that commercial Lyme vaccines for dogs induce only transient antibody responses in horses which can also be of low magnitude. Protection from infection with B. burgdorferi should not be automatically assumed after vaccinating horses with Lyme vaccines for dogs.

An antigen-specific, four-color, B-cell FluoroSpot assay utilizing tagged antigens for detection

The FluoroSpot assay, a variant of ELISpot utilizing fluorescent detection, has so far been used primarily for assessment of T cells, where simultaneous detection of several cytokines has allowed a more qualitative analysis of functionally distinct T cells. The potential to measure multiple analytes also presents several advantages when analyzing B cells. Our aim was to develop a B-cell FluoroSpot assay adaptable to studies of a variety of antigens. The assay utilizes anti-IgG antibodies immobilized in 96-well filter membrane plates. During cell culture, IgG antibodies secreted by antibody-secreting cells (ASCs) are captured in the vicinity of each of these cells and the specificity of single ASCs is defined using antigens for detection. The antigens were labeled with biotin or peptide tags enabling secondary detection with fluorophore-conjugated streptavidin or tag-specific antibodies. The assay, utilizing up to four different tag systems and fluorophores simultaneously, was evaluated using hybridomas and immunized splenocytes as ASCs. Assay variants were developed that could: i) identify multiple ASCs with different antigen specificities; ii) detect ASCs showing cross-reactivity with different but related antigens; and iii) define the antigen-specificity and, by including anti-IgG subclass detection reagents, simultaneously determine the IgG subclass of antibodies secreted by ASCs. As demonstrated here, the B-cell FluoroSpot assay using tag-based detection systems provides a versatile and powerful tool to investigate antibody responses by individual cells that can be readily adapted to studies of a variety of antigen-specific ASCs.

Improved performance and immunological responses as the result of dietary genistein supplementation of broiler chicks

The present study aimed to investigate the effect of supplemental genistein (an isoflavonoid) on performance, lymphoid organs’ development, and cellular and humoral immune responses in broiler chicks. A total of 675-day-old male broiler chicks (Ross 308) were randomly assigned to the five replicate pens (15 chicks each) of nine experimental diets. Dietary treatments included a negative (not-supplemented) control diet, two positive control groups (virginiamycin or zinc-bacitracin, 20 mg/kg), and diets containing 10, 20, 40, 80, 160 and 320 mg/kg of genistein. The cutaneous basophil hypersensivity (CBH) test was measured at day 10 of age after toe web injection with phytohemagglutinin-P. In addition, sera samples were collected after different antigen inoculations to investigate antibody responses. At day 28 of age, three randomly selected birds from each pen were euthanized to evaluate the relative weights of lymphoid organs. Results showed that dietary supplementation of both antibiotics increased (P<0.01) feed intake during 1 to 42 days of age. Furthermore, daily weight gain was influenced (P<0.01) by dietary treatments throughout the trial, so that the birds fed on antibiotics and 20 to 80 mg/kg genistein diets revealed the greater weight gains compared with other experimental groups. The best (P<0.05) feed conversion ratio assigned to the birds fed on diets containing antibiotics and moderate levels (40 to 80 mg/kg) of genistein. Although the relative weights of thymus (P<0.05) and bursa of Fabricius (P<0.01) were greater in birds fed on genistein-supplemented diets compared with antibiotics-supplemented birds, the spleen weight was not affected by experimental diets. Similarly, CBH response and antibody titers against Newcastle and infectious bronchitis disease viruses were markedly (P<0.05) greater in chicks fed on diets supplemented with 20 to 80 mg/kg of genistein. Interestingly, the higher dosages of genistein suppressed CBH and antibody responses to the levels seen by control and antibiotics chicks. Dietary inclusion of genistein increased (P<0.05) lymphocytes and subsequently reduced (P<0.01) heterophil to lymphocyte ratio. The present findings indicate that dietary genistein supplementation at the levels of 20 to 80 mg/kg not only improves growth performance, but also could beneficially affect immunological responses in broiler chicks.

First report on the antibody verification of HLA-DR, HLA-DQ and HLA-DP epitopes recorded in the HLA Epitope Registry

The International Registry of Antibody-Defined HLA Epitopes (http://www.epregistry.com.br) has been recently established as a tool to understand humoral responses to HLA mismatches. These epitopes can be structurally defined as eplets by three-dimensional molecular modeling and amino acid sequence differences between HLA antigens. A major goal is to identify HLA eplets that have been verified experimentally with informative antibodies. This report addresses class II epitopes encoded by genes in the HLA-D region. Our analysis included reviews of many publications about epitope specificity of class II reactive human and murine monoclonal antibodies and informative alloantibodies from HLA sensitized patients as well as our own antibody testing results. As of July 1, 2014, 24 HLA-DRB1/3/4/5, 15 DQB, 3 DQA and 8 DPB antibody-verified epitopes have been identified and recorded. The Registry is still a work-in-progress and will become a useful resource for HLA professionals interested in histocompatibility testing at the epitope level and investigating antibody responses to HLA mismatches in transplant patients.

Enhanced protection against Clonorchis sinensis induced by co-infection with Trichinella spiralis in rats.

Although co-infection with multiple parasites is a frequent occurrence, changes in the humoral immune response against a pre-existing parasite induced as a result of a subsequent parasitic infection remain undetermined. Here, we utilized enzyme-linked immunosorbent assay (ELISA) to investigate antibody responses, cytokine production and enhanced resistance in Clonorchis sinensis-infected rats (Sprague-Dawley) upon Trichinella spiralis infection. Higher levels of C. sinensis-specific IgG and IgA were elicited upon T. spiralis infection, and these levels remained higher than in rats infected with C. sinensis alone. Upon subsequent infection with T. spiralis, IgG antibodies against C. sinensis appeared to be rapidly boosted at day 3, and IgA antibodies were boosted at day 7. Challenge infection of C. sinensis-infected rats with T. spiralis induced substantial mucosal IgG and IgA responses in the liver and intestine and increases in antibody-secreting plasma cells in the spleen and bone marrow. Subsequent infection also appeared to confer effective control of liver C. sinensis loads, resulting in enhanced resistance. Memory B cells generated in response to C. sinensis infection were rapidly amplified into antibody-secreting cells upon T. spiralis infection. These results indicate that enhanced C. sinensis clearance induced by co-infection is associated with systemic and mucosal IgG and IgA responses.

First report on the antibody verification of MICA epitopes recorded in the HLA epitope registry.

The International Registry of HLA Epitopes (http://epregistry.com.br) has been recently established as a tool to understand antibody responses to HLA mismatches. These epitopes are defined structurally by three-dimensional molecular modelling and amino acid sequence differences between HLA antigens. A major goal was to identify HLA epitopes that have been verified experimentally with informative antibodies. This report addresses the identification of MICA epitopes. Our analysis included published information about MICA antibody reactivity in sera from sensitized patients as well as data from our own laboratories. This report describes twenty-one MICA epitopes verified with antibodies which have primarily been tested in Luminex assays with single alleles. The epitopes correspond to distinct eplets that are often defined by single residues. The Registry is still a work-in-progress and will become a useful resource for HLA professionals interested in histocompatibility testing at the epitope level and investigating antibody responses to HLA mismatches in transplant patients.

First report on the antibody verification of HLA-ABC epitopes recorded in the website-based HLA Epitope Registry.

The International Registry of Antibody-Defined HLA Epitopes ( http://www.epregistry.com.br) has been recently established as a tool to understand humoral responses to human leukocyte antigen (HLA) mismatches. These epitopes are defined structurally by three-dimensional molecular modeling and amino acid sequence differences between HLA antigens. So-called eplets represent essential components of HLA epitopes and they are defined by polymorphic residues. A major goal is to identify HLA epitopes that have been verified experimentally with informative antibodies. Our analysis has also included data in many publications. As of 1 November 2013, 95 HLA-ABC antibody-verified epitopes have been recorded, 62 correspond to eplets and 33 are defined by eplets paired with other residue configurations. The Registry is still a work-in-progress and will become a useful resource for HLA professionals interested in histocompatibility testing at the epitope level and investigating antibody responses to HLA mismatches in transplant patients.

Preventing intense false positive and negative reactions attributed to the principle of ELISA to re-investigate antibody studies in autoimmune diseases

To study the possible involvement of potential environmental pathogens in the pathogenesis of autoimmune diseases, it is essential to investigate antibody responses to a variety of environmental agents and autologous components. However, none of the conventional ELISA buffers can prevent the false positive and negative reactions attributed to its principal, which utilizes the high binding affinity of proteins to plastic surfaces. The aims of this study are to reveal all types of non-specific reactions associated with conventional buffer systems, and to re-investigate antibody responses to potential environmental pathogenic and autologous antigens in patients with autoimmune diseases using a newly developed buffer system “ChonBlock™” by ELISA.Compared to conventional buffers, the new buffer was highly effective in reducing the most intense false positive reaction caused by hydrophobic binding of immunoglobulin in sample specimens to plastic surfaces, “background (BG) noise reaction”, and other non-specific reactions without interfering with antigen–antibody reactions. Applying this buffer, we found that IgG antibody responses to Escherichia coli O111:B4, E. coli lipopolysaccharide (LPS) and peptidoglycan polysaccharide (PG-PS) were significantly lower or tended to be lower in patients with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), whereas IgA antibody responses to these antigens were equal or tended to be higher compared to normal controls. As a consequence, the IgA/IgG antibody ratios against these agents were significantly higher in patients with RA and SLE, except for Crohn's disease, which showed significantly higher IgG responses to these antigens.To assay antibodies in human sera, it is indispensable to eliminate false positive and negative reactions by using an appropriate buffer system, and to include antigen non-coated blank wells to determine BG noise reactions of invidual samples. Finally, based on our preliminary analysis in this study, we propose that low IgG antibody responses to potential pathogenic environmental factors may be the fundamental disorder in autoimmune diseases.

Human Antibody Responses to Avian Influenza A(H7N9) Virus, 2013

Understanding host antibody response is crucial for predicting disease severity and for vaccine development. We investigated antibody responses against influenza A(H7N9) virus in 48 serum samples from 21 patients, including paired samples from 15 patients. IgG against subtype H7 and neutralizing antibodies (NAbs) were not detected in acute-phase samples, but ELISA geometric mean titers increased in convalescent-phase samples; NAb titers were 20–80 (geometric mean titer 40). Avidity to IgG against subtype H7 was significantly lower than that against H1 and H3. IgG against H3 was boosted after infection with influenza A(H7N9) virus, and its level in acute-phase samples correlated with that against H7 in convalescent-phase samples. A correlation was also found between hemagglutinin inhibition and NAb titers and between hemagglutinin inhibition and IgG titers against H7. Because of the relatively weak protective antibody response to influenza A(H7N9), multiple vaccinations might be needed to achieve protective immunity.

Antibodies by Non-Febrile, Smear-Negative Individuals from a Malaria Epidemic-Prone Setting in Ethiopia are Strongly Reactive to Plasmodium falciparum Blood-Stage Vaccine Candidate Antigens

Background: Plasmodium falciparum malaria remains a major public health concern globally though there is some decline due to scale-up of control efforts. Evaluation of the anti-malarial immune profile, in populations residing in epidemic-prone areas in the dry season or at the time when vector control largely reduced man-mosquito contact, would help predict malaria burden when future epidemics occur. Methods: A cross-sectional study was designed to investigate antibody responses to four P. falciparum blood stage vaccine candidate antigens in non-febrile individuals from Shewa Robit in north-central Ethiopia where malaria transmission was expected at a minimal level as a result of the sampling season and effective vector control. Blood samples were analyzed microscopically for Plasmodium detection. The enzyme-linked immunosorbent assay (ELISA) was used to measure immunoglobulin (IgG) antibodies to apical membrane antigen 1 (AMA1), glutamaterich protein (GLURP) R2 region and merozoite surface protein 2 (MSP2) allelic variants. Results: Study participants were smear-negative for Plasmodium infection. While 51 (22%) of the participants reported that they had never been exposed to clinical malaria in life, 177 (78%) reported at least one clinical malaria episode with laboratory confirmed P. falciparum infection. The antigens tested were well-recognized by the test sera although significant differences were observed in antibody prevalence and level between the different antigens and there was inter-individual variability. IgG response to the antigens showed age-related pattern but without evidence of relation with status and frequency of reported past exposure to clinical malaria. Conclusion: The data suggests that individuals in an epidemic-prone malaria setting have reactive and stable antibodies that readily recognize P. falciparum blood-stage vaccine candidate antigens in the absence of slidepositivity. Analysis of age-related pattern in antibody level showed positive association with age but unrelated with increasing frequency of reported episode suggesting the role of intrinsic age-related factors in malaria immune maturation.

16th IHIW: A Website for Antibody‐Defined HLA Epitope Registry

The concept that HLA antibodies are specific for epitopes rather than HLA antigens is important not only for the determination of mismatch acceptability for sensitized patients but also for a better understanding of the antibody response to an HLA mismatch. Numerous publications describe epitope-specific antibodies, but there is no standardized information about the repertoire of clinically relevant HLA epitopes. Under auspices of the 16th IHIW, we have developed a website-based registry of antibody-verified HLA epitopes. Epitope notations are based on HLA molecular modelling of amino acid residues in polymorphic sequence positions. Informative epitope-specific antibodies had been induced by a transplant, transfusion or pregnancy and were monoclonal antibodies or eluates of sera absorbed with single HLA alleles. Antibody reactivity was determined in binding assays with single-allele panels. Antibody producer/immunizer HLA types enhanced the characterization of specific epitopes. The Registry also includes epitopes described in original research publications. Based on the extent of antibody reactivity information, we assigned epitope status as confirmed (well documented) or provisional (more data are needed). At present, the Registry has 69 HLA-ABC, 53 DRB1/3/4/5, 17 DQ, 8 DP and 22 MICA antibody-verified epitopes and will be updated on a quarterly basis. Laboratories worldwide continue to submit data about previously unreported antibody-specific epitopes. For each epitope, the website shows its amino acid composition and HLA alleles that share the epitope. Links show antibody reactivity patterns, sensitization information and references. Other links show molecular modelling of corresponding structural epitopes and polymorphic residue information for epitope-carrying alleles. The website will also have a link to epitope frequency information in different populations. Search functions will list mismatched epitopes on mismatched alleles for selected HLA types. The HLA Epitope Registry will become a valuable resource for researchers interested in HLA compatibility at the epitope level and investigating antibody responses to HLA mismatches.

Systemic Antibody Responses to the Immunodominant p23 Antigen and p23 Polymorphisms in Children with Cryptosporidiosis in Bangladesh

Cryptosporidium is a major cause of diarrhea in children in developing countries. However, there is no vaccine available and little is known about immune responses to protective antigens. We investigated antibody responses to p23, a putative vaccine candidate, in children in Bangladesh with cryptosporidiosis and diarrhea (cases) and uninfected children with diarrhea (controls), and p23 gene polymorphisms in infecting species. Serum IgM, IgG, and IgA responses to p23 were significantly greater in cases than controls after three weeks of follow-up. Cases with acute diarrhea had significantly greater serum IgA and IgM responses than those with persistent diarrhea, which suggested an association with protection from prolonged disease. The p23 sequences were relatively conserved among infecting species and subtype families. Although most children were infected with Cryptosporidium hominis, there was a cross-reactive antibody response to C. parvum antigen. These results support further development of p23 as a vaccine candidate.