Polyspecific malaria antibodies present at the time of infection inhibit the development of immunity to malaria but antibodies specific for the malaria merozoite surface protein, MSP1, facilitate immunity

Serum taken from mice immune to malaria as a result of infection and drug cure, or from mice immunized with a recombinant form of the merozoite surface protein, MSP1, can provide passive protection of recipient mice against the lethal parasite, Plasmodium yoelii YM. However, recipients of MSP1-immune serum go on to develop long-term immunity, whereas recipients of serum from mice naturally immune to malaria rapidly lose their resistance to infection. We demonstrate that 'infection/cure' serum suppresses the development of both antibody and cell-mediated parasite-specific responses in recipients, whereas these develop in recipients of MSP1-specific antibodies. These data have profound implications for our understanding of the development of malaria immunity in babies who passively acquire antibodies from their mothers.

Single-chain antibodies produced by phage display against the C-terminal 19 kDa region of merozoite surface protein-1of Plasinodium yoelii reduce parasite growth following challenge

Antibodies have the potential to be therapeutic reagents for malaria. Here we describe the production of a novel phage antibody display library against the C-terminal 19 kDa region of the Plasmodium yoelii YM merozoite surface protein-1 (MSP1(19)). In vivo studies against homologous lethal malaria challenge show an anti-parasite effect in a dose dependent manner, and analysis by plasmon resonance indicates binding to the antigen is comparable to the binding of a protective monoclonal antibody. The data support the lack of a need for any antibody Fc-related function and hold great significance for the development of a therapeutic reagent for malaria. (C) 2002 Elsevier Science Ltd. All rights reserved.

Epitope-blocking enzyme-linked immunosorbent assays for the detection of serum antibodies to West Nile virus in multiple avian species

We report the development of epitope-blocking enzyme-linked immunosorbent assays (ELISAs) for the rapid detection of serum antibodies to West Nile virus (WNV) in taxonomically diverse North American avian species. A panel of flavivirus-specific monoclonal antibodies (MAbs) was tested in blocking assays with serum samples from WNV-infected chickens and crows. Selected MAbs were further tested against serum samples from birds that represented 16 species and 10 families. Serum samples were collected from birds infected with WW or Saint Louis encephalitis virus (SLEV) and from noninfected control birds. Serum samples from SLEV-infected birds were included in these experiments because WNV and SLEV are closely related antigenically, are maintained in similar transmission cycles, and have overlapping geographic distributions. The ELISA that utilized MAb 3.11126 potentially discriminated between WW and SLEV infections, as all serum samples from WNV-infected birds and none from SLEV-infected birds were positive in this assay. Assays with MAbs 2132 and 6B6C-1 readily detected serum antibodies in all birds infected with WNV and SLEV, respectively, and in most birds infected with the other virus. Two other MAbs partially discriminated between infections with these two viruses. Serum samples from most WNV-infected birds but no SLEV-infected birds were positive with MAb 3.676, while almost all serum samples from SLEV-infected birds but few from WNV-infected birds were positive with MAb 6B5A-5. The blocking assays reported here provide a rapid, reliable, and inexpensive diagnostic and surveillance technique to monitor WNV activity in multiple avian species.

Epitope-blocking enzyme-linked immunosorbent assays for detection of West Nile virus antibodies in domestic mammals

We evaluated the ability of epitope-blocking enzyme-linked immunosorbent assays (ELISAs) to detect West Nile virus (WNV) antibodies in domestic mammals. Sera were collected from experimentally infected horses, cats, and pigs at regular intervals and screened in ELISAs and plaque reduction neutralization tests. The diagnostic efficacies of these techniques were similar.

Prevalence of antibodies to the BK and JC papovaviruses in isolated populations

A total of 173 sera from isolated Brazilian Indian populations, 39 from the Diauarun area, and 68 from the Alto Xingú area, respectively in the North and the South of the Xingú National Park and 66 Kren-Akorore Indians, were examined for hemagglutination - inhibiting (HI) antibodies against BK and JC viruses. The global percentages of positive sera (> 1:40) were 5.2% for BK virus and 1.7% for JC virus. The distribution of positive sera according to the population groups showed one individual to be positive for BK virus in the Diauarun Indians and none of the sera contained HI antibody to JC virus; in the Alto Xingú Indians, 4 were positive for BK virus and 3 others were positive for JC virus; as regards Kren-Akorore Indians none of the sera contained antibody to JC virus, and only 4 were BK positive. Due to the limited number of observations it was neither possible to determine the time of occurrence of seroconversion nor correlate the positivity rates for both viruses in the different tribes with the respective "contact" with the white population.

Lyme Disease: antibodies against Borrelia burgdorferi in farm workers in Argentina

Lyme Disease is a tick-borne (specially by Ixodes ticks) immune-mediated inflammatory disorder caused by a newly recognize spirochete, Borrelia burgdorferi. Indirect fluorescent antibody (IF) staining methods and enzyme-linked immunosorbent assay are frequently relied upon to confirm Lyme borreliosis infections. Although serologic testing for antibodies has limitations, it is still the only practical means of confirming B. burgdorferi infections. Because we have no previous report of Lyme disease in human inhabitants in Argentina, a study was designed as a seroepidemiologic investigation of the immune response to B. burgdorferi in farm workers of Argentina with arthritis symptoms. Three out of 28 sera were positive (#1,5 and 9). Serum # 1 was positive for Immunoglobulin G at dilution 1:320, serum # 5 and # 9 both to dilution 1:160; while for Immunoglobulin M all (#1, 5 and 9) were positive at low dilution (1:40) using IF. The results showed that antibodies against B. burgdorferi are present in an Argentinian population. Thus caution should be exercised in the clinical interpretation of arthritis until the presence of B. burgdorferi be confirmed by culture in specific media.

Human cryptosporidiosis: detection of specific antibodies in the serum by an indirect immunofluorescence

Cryptosporidium sp., a coccidian parasite usually found in the faeces of cattle, has been recently implicated as an agent of human intestinal disease, mainly in immunocompromised patients. In the study realized, by an indirect immunofluorescence technique, specific immunoglobulins (IgG and IgM) have been demonstrated in human serum against Cryptosporidium oocysts. Purified oocysts were used as antigens in the indirect immunofluorecence assay. After analyzing this test in sera from selected groups of patients, the frequency of both specific IgG and IgM of immunocompetent children who were excreting oocysts in their faeces was 62% and in children with negative excretion of oocysts was 20% and 40%, respectively. In adults infected with the human immunodeficiency virus (HIV) and who were excreting Cryptosporidium in their stools, the frequency was 57% for IgG but only 2% for IgM. Twenty three percent of immunocompromised adults with not determined excretion of oocysts in their stools had anti-Cryptosporidium IgG in their sera. Children infected with human immunodeficiency virus had no IgM and only 14% had IgG detectable in their sera. The indirect immunoflorescence assay, when used with other parasitological techniques appears to be useful for retrospective population studies and for diagnosis of acute infection. The humoral immune response of HIV positive patients to this protozoan agent needs clarification.

Chromatographic behaviour of monoclonal antibodies against wild-type amidase from Pseudomonasaeruginosa on immobilized metal chelates

The aim of this work was to devise a one-step purification procedure for monoclonal antibodies (MAbs) of IgG class by immobilized metal affinity chromatography (IMAC). Therefore, several stationary phases were prepared containing immobilized metal chelates in order to study the chromatographic behaviour of MAbs against wild-type amidase from Pseudomonas aeruginosa. Such MAbs adsorbed to Cu(II), Ni(II), Zn(II) and Co(II)-IDA agarose columns. The increase in ligand concentration and the use of longer spacer arms and higher pH values resulted in higher adsorption of MAbs into immobilized metal chelates. The dynamic binding capacity and the maximum binding capacity were 1.33 +/- 0.015 and 3.214 +/- 0.021 mg IgG/mL of sedimented commercial matrix, respectively. A K(D) of 4.53 x 10(-7) M was obtained from batch isotherm measurements. The combination of tailor-made stationary phases of IMAC and the correct selection of adsorption conditions permitted a one-step purification procedure to be devised for MAbs of IgG class. Culture supernatants containing MAbs were purified by IMAC on commercial-Zn(II) and EPI-30-IDA-Zn(II) Sepharose 6B columns and by affinity chromatography on Protein A-Sepharose CL-4B. This MAb preparation revealed on SDS-PAGE two protein bands with M(r) of 50 and 22 kDa corresponding to the heavy and light chains, respectively. Copyright (C) 2011 John Wiley & Sons, Ltd.

Voltammetric immunosensor for the diagnosis of celiac disease based on the quantification of anti-gliadin antibodies

Antibodies against gliadin are used to detect celiac disease (CD) in patients. An electrochemical immunosensor for the voltammetric detection of human anti-gliadin antibodies (AGA) IgA and AGA IgG in real serum samples is proposed. The transducer surface consists of screen-printed carbon electrodes modified with a carbon nanotube/gold nanoparticle hybrid system, which provides a very useful surface for the amplification of the immunological interactions. The immunosensing strategy is based on the immobilization of gliadin, the antigen for the autoantibodies of interest, onto the nanostructured surface. The antigen–antibody interaction is recorded using alkaline phosphatase labeled anti-human antibodies and a mixture of 3-indoxyl phosphate with silver ions (3-IP/Ag+) was used as the substrate. The analytical signal is based on the anodic redissolution of the enzymatically generated silver by cyclic voltammetry. The electrochemical behavior of this immunosensor was carefully evaluated assessing aspects as sensitivity, non-specific binding and matrix effects, and repeatability and reproducibility. The results were supported with a commercial ELISA test.

Hepatitis A antibodies in two socioeconomically distinct populations of São Paulo, Brazil

To evaluate the prevalence of antibody against hepatitis A in two socioeconomically distinct populations of a developing country, 540 serum specimens from children and adults living in São Paulo, Brazil, were tested for IgG anti HAV by a commercial radioimunoassay (Havab, Abbott Laboratories). The prevalence of anti-HAV in low socioeconomic level subjects was 75.0% in children 2-11 years old and 100.0% in adults, whereas in middle socioeconomic level significantly lower prevalences were observed (40.3% in chidren 2-11 years old and 91.9% in adults). Voluntary blood donors of middle socioeconomic level showed a prevalence of 90.4%. These data suggest that hepatitis A infection remains a highly endemic disease in São Paulo, Brazil.

Prevalence of anti-p: Falciparum sporozoite antibodies in adults in the amapa region of Brazil

17 of 20 adult sera from the Amapa region of Brazil were active in the inhibition of P. falciparum sporozoite invasion (ISI) assay which has been correlated with protective antibodies. In contrast 11 sera were positive in IFA tests and 6 were positive in CSP tests. These results suggest that the ISI assay will be useful for evaluating naturally acquired protective anti-sporozoite antibodies in endemic areas, particularly during vaccine efficacy studies using sporozoite-based vaccines.

The presence of antibodies for hepatitis a virus in amazonia Didelphis marsupialis (Vertebrata, Marsupialia)

Anti-HAV was detected by enzyme - immunoassay in sera collected from 6 (18,75%) of 32 Didelphis marsupialis trapped in the Amazon region. No anti-HAV were found in the sera from 136 other wild animals, including small rodents, reptiles and other marsupials.

Lectins for the detection of IgM antibodies to T. gondii in the diagnosis of acute toxoplasmosis by immunofluorescence test

Lectins were labeled with fluorescein and tried as conjugates in the immunofluorescence (IP) test for the detection of IgM antibodies to T. gondii, in the diagnosis of acute toxoplasmosis. This approach was an attempt to find alternative reagents for anti-human IgM fluorescent conjugates (AHIgMFC), which contain quite frequently anaibcdies to toxoplasma, as contaminants, due to natural T. gondii infections among animals used for imunization. Lentil (Lens culinaris) lectin fluorescence conjugates (LcFC) provided most satisfactory results. The evaluation of LcFC carried out in a total of 179 sera from patients with acute and chronic toxoplasmosis, with non-related infections or healthy subjects, gave high values of relative efficiency, co-positivity and co-negativity indices, respectively 0.989, 0.969 and 1.000, in reference to the conventional AHIgMFC. Moreover, three batches of LcFC successively prepared gave reproducible test results. The advantage of LcFC as an alternative reagent for the serodiagnosis of acute toxoplasmosis is supported by practical aspects of its preparation.