Structural basis for carbohydrate binding properties of a plant chitinase-like agglutinin with conserved catalytic machinery.

A new chitinase-like agglutinin, RobpsCRA, related to family GH18 chitinases, has previously been identified in black locust (Robinia pseudoacacia) bark. The crystal structure of RobpsCRA at 1.85Å resolution reveals unusual molecular determinants responsible for the lack of its ancestral chitinase activity. Unlike other chitinase-like proteins, which lack chitinase catalytic residues, RobpsCRA has conserved its catalytic machinery. However, concerted rearrangements of loop regions coupled to non-conservative substitutions of aromatic residues central to the chitin-binding groove explain the lack of hydrolytic activity against chitin and the switch toward recognition of high-mannose type N-glycans. Identification of close homologs in flowering plants with conservation of sequence motifs associated to the structural adaptations seen in RobpsCRA defines an emerging class of agglutinins, as emphasized by a phylogenetic analysis, that are likely to share a similar carbohydrate binding specificity for high-mannose type N-glycans. This study illustrates the recent evolution and molecular adaptation of a versatile TIM-barrel scaffold within the ancestral GH18 family.

Identification of the hydroxyapatite-binding domain of salivary agglutinin.

The salivary agglutinin glycoprotein (SAG) is present in saliva but is also part of the salivary pellicle, playing a seemingly paradoxical role with regard to bacterial homeostasis. On the one hand, SAG aggregates bacteria in solution, thereby preventing bacterial colonization. On the other hand, when bound to the tooth surface, SAG facilitates bacterial colonization and microbial growth. The protein part of SAG is predominantly composed of conserved scavenger receptor cysteine-rich (SRCR) domains. Previously it was found that bacterial binding and aggregation is mediated via a single peptide loop, designated SRCRP2 (P2), within the SRCR domains of SAG. The current data suggest that the SRCR domains also harbour a hydroxyapatite (HA)-binding moiety, SRCRP3 (P3). The observation that P2 and P3 individually play unique roles in the function of SAGs contributes to our understanding of the dual role of SAGs in bacterial binding. Inspired by the bacterial-modulating capacity of SAGs, we created a P3-polyethylene glycol (PEG) conjugate. It was found that a P3 coating resulted in an increased antifouling activity of 20% compared with the uncoated surface in vitro. An additional PEG moiety resulted in an antifouling activity of up to 40% and 30% for Streptococcus mutans and Staphylococcus epidermidis, respectively.

Modifications influencing Widal test reactivity in a novel microplate assay.

Reliability of the Widal tube agglutination test has been the subject of many controversies over the years. This study was performed to assess the effect of certain modifications on the performance of Widal test in a novel microplate assay. Sera from 37 patients (21 males; 16 females) (mean age 28 +/- 7 years) were tested in the Immunology Unit at King Khalid University Hospital, Riyadh. Among them were 26 patients with suspected typhoid fever and 11 had bacteriologically confirmed diagnosis of Salmonella infection. The modifications included either the use of 0.5% bovine serum albumin (BSA), absorption of sera with sheep red blood cells (SRBC) or heat inactivation of sera. Compared with Widal tube agglutination test, microplate assay with SRBC absorption of the sera from patients with suspected typhoid fever was not only associated with enhancement of detection titers for both H (p < or = 0.001) and O (p < or = 0.005) Salmonella agglutinins but also the percentage of reactivity. The presence of BSA augmented detection titers for Salmonella H agglutinins (p < or = 0.02) only. Heat inactivation of sera however was found to be associated with reduction in the detectable titers for both H (p < or = 0.03) and O (p < or = 0.01) agglutinins. Increased titers of Salmonella agglutinins were also evident in 11 patients with confirmed diagnosis of Salmonella infection. The novel microplate agglutination assay using the SRBC absorption was associated with enhancement in Widal test reactivity and appears to be a useful alternative for the diagnosis of Salmonella infection.

Yersinia pestis autoagglutination factor is a component of the type six secretion system.

Autoagglutination (AA) is a protective phenotypic trait facilitating survival of bacteria in hostile environments and in the host during infection. Autoagglutination factors (AFs) that possess self-associating ability are currently characterized in many Gram-negative bacteria, but Yersinia pestis AFs are still a matter of debate. Previously, we have shown that AF of Hms(-) strain Y. pestis EV76 is a complex of the 17,485-kDa protein and a low-molecular-weight component with siderophore activity. Here, we identified the protein moiety of AF and examined its role in AA of Hms(+) and Hms(-)Y. pestis strains. Using MALDI-TOF MS of trypsin-hydrolyzed AF, we unambiguously identified the protein as YPO0502, which belongs to a family of Hcp-proteins forming pilus-like structures of the type six secretion system (T6SS). To address the role of YPO0502 in AA, we cloned ypo0502 in E. coli, overexpressed it in Y. pestis and constructed its knock-out mutant in Y. pestis. However, all these approaches failed: YPO0502 was not secreted in E. coli, formed inclusion bodies when overexpressed in Y. pestis, and could probably be compensated by other Hcp-like proteins in Y. pestis. In contrast, downregulation of ypo0502 expression by its antisense RNA supported the contribution of YPO0502 in AA of Hms(+) and Hms(-)Y. pestis strains. The results of the present study indicate that the Hcp-like component of T6SS encoded by ypo502 is involved in Y. pestis AA and suggest that at least one (ypo0499-0516) of the 6 T6SS clusters of Y. pestis is involved in bacterial interaction.

Variations in the responses of C57BL-10J and A-J mice to sheep red blood cells.

In response to repeated injections of sheep red blood cells, C57BL/10J mice produce predominantly 19S antibody in increasingly higher amounts, while A/J mice initially produce 19S antibody and then switch to produce increasing 7S antibody titers. In an F(1) generation all mice responded like the C57BL/10J mice. Backcross data implied genetic control involving at least three loci.

The role of the elution in antibody investigations.

BACKGROUND: The direct antiglobulin test (DAT) commonly detects immunoglobulin G (IgG) molecules or complement fragments on the red blood cell (RBC) surface. If IgG antibodies are present then elution procedures can be performed to identify the specificity of these antibodies. Our reference laboratory performs elutions on the RBCs of those patients who have received cellular blood products in the past 30 days and have either a newly identified positive DAT with anti-IgG or the agglutination strength is increased over a previous DAT and if ordered by a clinician regardless of transfusion history. This study questioned how frequently elutions contributed novel serologic information under our reference laboratory's current policy or whether elutions should be performed in more selective serologic conditions. STUDY DESIGN AND METHODS: Recipients whose RBCs underwent eluate testing were identified from the blood bank's database and information about the antecedent DAT and antibody detection test and eluate was recorded. RESULTS: In total 648 eluates were evaluated and 82 of 648 (12.7%) revealed a novel antibody not present in the serum (an informative eluate). In 2 of 82 informative eluates non-anti-A/B alloantibodies that were not present in the serum were detected: one example each of anti-D and anti-E. Both were associated with a microscopically positive antecedent DAT. The rate of an informative eluate was higher when the antibody detection test was negative. CONCLUSION: The strength of the DAT does not indicate the likelihood of an informative eluate. Performing an eluate when the antibody detection test is positive has limited value.

Hemagglutinating 7S subunits of 19S cold agglutinins.

Two highly purified IgM cold agglutinins have been mildly reduced yielding 7S subunits, with interchain covalent bonds intact. These subunits retained most of the cold-agglutinin activity as well as the specificity of the parent antibodies. However, as might be anticipated from theories of the importance of antibody size and number of subunits for complement binding, the IgM subunits were only very weakly lytic compared with the intact cold agglutinins. The findings are consistent with the presence of ten antibody-combining sites on the IgM molecule.

Capillary zone electrophoresis method development for the analysis of Hippeastrum hybrid agglutinin samples.

A capillary zone electrophoresis (CZE) method was developed aiming the analysis of Hippeastrum hybrid agglutinin (HHA) samples. HHA is presently being tested as a vaginal microbicide to prevent HIV transmission. It acts by direct binding to mannose residues that are abundantly present on the HIV gp120 envelope and so interrupts the virus entry process. The final CZE method employs 50mM sodium tetraborate (pH 9.9) as background electrolyte. In this condition, a cluster of about 30 isoform peaks is obtained, with very repeatable patterns. RSDs in the order of 0.2% for the migration time and detection sensitivity in the order of 70microgml(-1) were achieved.

Prevalence of Salmonella antibodies among goats slaughtered for chevon in Bareilly (Northern India).

We screened serum samples of 1024 goats slaughtered for chevon in Bareilly in Northern India for Salmonella antibodies with indirect ELISA, MAT-H (microagglutination test using flagellar antigens e, n, x and 1, 5) and MAT-O (microagglutination test using somatic antigens 4, 12 and 3, 10, 15). Salmonella antibodies were detected in 48, 8 and 40%, goats using Salmonella-cytotoxi-I ELISA, MAT 'H' and MAT 'O', respectively. After adjusting for test accuracy, the seroprevalence were highest for Salmonella-cytotoxi-I ELISA (46%) followed by agglutinins against 'O' 3, 10, 15 (15%) and negligible for other agglutinins. With all 5 tests, prevalence of Salmonella antibodies was significantly higher in females than in males. No significant difference was evident in prevalence of Salmonella antibodies to different antigens in different age groups of male goats except for e, n, x agglutinins that were significantly more prevalent in young adult (<6-18 months) males than in adult (>18 months of age) or young (< or =6 months of age) goats. On the other hand, in females, prevalence of Salmonella-cytotoxin-I antibodies and e, n, x agglutinins differed significantly among three age groups, being the most prevalent in adult goats. As expected, the results of different tests had little or no correlation because the different tests targeted antibodies to different antigens.

Cold Agglutinin Disease in a Patient of Pulmonary Tuberculosis.

We report a case of secondary cold agglutinin disease (CAD) due to pulmonary tuberculosis in a 68-year male patient who presented with acrocyanosis involving both upper limbs and greater portion of lower limbs. Direct Coombs' test was positive with mild anemia and the cold agglutinin titer was high. Sputum showed numerous acid fast bacilli per high power field. The patient was given standard anti-tuberculous treatment (ATT) and his symptoms gradually improved. After nine months of ATT, his haemoglobin improved, acrocyanosis resolved completely and cold agglutinin titer decreased in level.

Hodgkin's cell lectin: an ectosialyltransferase and lymphocyte agglutinant related to the hepatic asialoglycoprotein receptor.

The galactophilic lectin expressed on the surface of cultured Hodgkin's cells, recently described by this laboratory, has binding characteristics similar to those of the hepatic asialoglycoprotein receptor (HBP), and has been recognized as a Mr 55,000 (p55) membrane glycoprotein by a polyclonal antiserum to rat HBP. This study confirms the close structural relationship between the two lectins showing immunological cross-reactivity of monoclonal and polyclonal antibodies recognizing distinct epitopes on rat or human HBP. In support of the suggested dual nature of p55 as lectin and ectosialyltransferase, enzyme activity is inhibited by the monoclonal anti-HBP antibody, anti-HA 116. Cultured Hodgkin's cells, as purified HBP, agglutinate T-lymphocytes expressing hyposialylated membrane glycosyl determinants. This cell-cell interaction mediated by p55 results in the incorporation of sialic acid into lymphocyte surface asialo-glycans. The function of the Hodgkin's lectin as lymphocyte agglutinant in vitro suggests its role as an immunomodulator contributing to the immunodeficiencies associated with Hodgkin's disease.

Studies on lectins. XXXVI. Properties of some lectins prepared by affinity chromatography on O-glycosyl polyacrylamide gels.

A number of lectins has been purified by affinity chromatography on O-glycosyl polyacrylamide gels. The lectins isolated (and the particular sugar ligands used in the affinity carriers) are as follows: Anguilla anguilla, serum (alpha-L-fucosyl-), Vicia cracca, seeds; Phaseolus lunatus, seeds; Glycine soja, seeds; Dolichos biflorus, seeds; Maclura pomifera, seeds; Sarothamnus scoparius, seeds; Helix pomatia, ablumin glands; Clitocybe nebularis, fruiting bodies (all N-acetyl-alpha-D-galactosaminyl-); Ricinus communis, seeds (beta-lactosyl-); Ononis spinosa, root; Fomes fomentarius, fruiting bodies; Marasmius oreades, fruiting bodies (all alpha-D-galactosyl-), Canavalia ensiformis, seeds, (i.e., concanavalin A) (alpha-D-glucosyl-). Physicochemical properties of Glycine soja, Dolichos biflorus, Phaseolus lunatus, Helix Pomatia and Ricinus communis lectins corresponded well to properties of the preparations studied earlier by other workers. For the other purified lectins the essential physiochemical data (sedimentation coefficient, molecular weight, subunit composition, electrophoretic patterns, amino acid composition, carbohydrate content, isoelectric point) were established and their precipitating, hemagglutinating and mitogenic activities determined.

Serologic studies in suspected visceral candidiasis.

Twenty-six healthy controls and 45 patients with clinically suspected candidiasis were studied utilizing precipitin determination by double immunodiffusion, agglutinin titers, and presence of clumping factor by microscopy. The data are used to evaluate the specificity, reproducibility, and ease of performance of the procedures. Our results indicate that there is considerable overlap in agglutinin titers in patients with or without visceral candidiasis and that determination of clumping factor by microscopy only is inadequate for diagnosis. Precipitin tests were positive in 80% of patients with visceral candidiasis (exceptions were highly immunosuppressed hosts). This test is easily performed, reproducible, and can be applied in any general hospital laboratory. Neither agglutinin nor precipitin determination appears to be applicable to determining duration of therapy.

Correlation of abnormal immunoglobulin with clinical features of myeloma.

Physical and chemical characteristics of the abnormal immunoglobulin as well as the immunoglobulin type are important determinants of the clinical features and prognosis in myeloma. A review of 270 cases of myeloma studied by the Acute Leukemia Group B showed that survival was adversely affected by azotemia. The presence of Bence Jones proteinuria adversely influenced survival even in patients who were not initially azotemic. The presence of lambda-type Bence Jones proteinuria resulted in greatly shortened survival in contrast to kappa-type Bence Jones proteinuria in the absence, or presence, of a serum IgG M-protein. The adverse effect of lambda-type Bence Jones protein could not be demonstrated in patients with IgA myeloma. Patients with IgA myeloma were found to have a noticeably shorter survival than those with IgG myeloma.

Cold agglutinin titers in psychiatric patients.

Cold agglutinin titers were obtained from the serum of 41 psychiatric patients. The 21 chronic schizophrenic patients tended to have positive cold agglutinin titers; the authors suggest that this immunological finding may be associated with long-term neuroleptic treatment.

Cold agglutinin autoantibodies in psychiatric patients: their relation to diagnosis and pharmacological treatment.

BACKGROUND AND METHOD: The purpose of this study was to compare titers of cold agglutinins in schizophrenic patients with those in patients with major affective disorders and in normal healthy subjects. One hundred sixty-six psychiatric patients and 37 healthy comparison subjects were included in the study. Ninety of the patients suffered from schizophrenia, 54 from bipolar disorder, and 22 from major depression. Venous blood samples were obtained from all subjects between 8:00 and 10:00 a.m. and were immediately tested for cold agglutinin titers. RESULTS: A high frequency (42.2%) of positive cold agglutinin titers was detected in the schizophrenic patients, compared with the bipolar (11.1%) and unipolar (9.0%) patients and the comparison group (8.1%). The investigators did not find any pharmacological effect on these results. CONCLUSIONS: The findings suggest that, at least in this group, positive cold agglutinin titers are associated with schizophrenia. However, this observation cannot provide direct evidence for the involvement of viral or autoimmune factors in schizophrenia.

Hemolytic anemia associated with multiple autoantibodies and low serum complement.

A 37 year old woman with extravascular hemolytic anemia had a positive Monospot test associated with positive antiglobulin and anticomplement Coombs' tests, cold agglutinins and warm autoantibodies. IgG-kappa (k) antibodies, which reacted with all panel red cells at 37 degrees C, were eluted from her circulating red cells. However, neither immunoglobulins nor C3 was detected after her serum was adsorbed with heterologous red cell stroma at 37 degrees C and eluted at the same temperature in glycine buffer. In contrast, IgM-kappa and IgM-lambda (lambda), IgG-3-kappa, IgG4-lambda, IgA-lambda and C3 were eluted at 37 degrees C from heterologous red cell stroma after adsorption with her serum at 0 degrees C. Thus, antibodies of several types, which were present in the patient's serum, reacted optimally with red cell antigens at low temperature. Cold-reactive IgG3-kappa antibodies, which also capable of interacting with red cells at 37 degrees C, probably accounted for the IgG-kappa antibodies eluted from the patient's circulating red cells. The patient's serum C4 titers were decreased, with low normal to moderately depressed C3 and low normal C5, indicating that the anti-red cell IgM and/or IgG3-kappa antibodies probably fixed complement. A localized cold stress test resulted in a transient increase in plasma hemoglobin and a decrease in serum C3 titer. These findings, and the beneficial clinical response obtained with small doses of prednisone, suggest that both the cold-reactive antibodies and the IgG-kappa on circulating red cells were pathophysiologically significant. This is the first report of a patient with multiple red cell autoantibodies in whom serum complement component titers were determined in conjunction with characterization of the anti-red cell immunoglobulins. Subclinical infectious mononucleosis may have preceded the prolonged hemolytic episode. Clinical evidence of systemic lupus erythematosus has not appeared.

Waterborne typhoid fever in Dade County, Florida. Clinical and therapeutic evaluation of 105 bacteremic patients.

An extensive outbreak of waterborne typhoid fever occurred in 1973 at a migrant labor camp in Dade County, Florida. Blood cultures from 105 of the 188 patients with proved or presumptive cases of typhoid fever grew Salmonella typhi. The clinical and laboratory findings in these patients were reviewed. Fever, usually with temperatures above 38.8 degrees C and of the sustained type, was a primary manifestation of disease, although a majority of the patients also complained of headache and gastroenteric symptoms. Hepatic or splenic enlargement was present in 52 per cent and 42 per cent, respectively, whereas rose spots were detected in only 13 per cent. The total leukocyte count was normal in 74 per cent, but serum levels of liver and muscle enzymes were frequently elevated. Gastrointestinal, pulmonary and neurologic complications were infrequent; circulatory failure was not observed. Defervescence in response to antibiotic therapy was variable; however, the median response among 68 patients who received chloramphenicol was two days less than that in 34 patients treated with ampicillin. There was one possible treatment failure with ampicillin. The relapse rate of 10 per cent in chloramphenicol-treated patients was not significantly greater than the 3 per cent rate among those treated with ampicillin. Serologic studies for typhoid fever were of limited diagnostic value since the titer of agglutinins was 1:160 or higher in 49 per cent of the serums obtained before treatment, and a fourfold rise in titer occurred in only 24 per cent of 57 patients studied. The serologic response to chloramphenicol treatment did not differ from that to ampicillin.

Effect of acyclovir on various murine in vivo and in vitro immunologic assay systems.

In two in vitro tests, lymphocyte-mediated cytotoxicity and neutrophil chemotaxis, acyclovir showed no inhibitory effects at concentrations as high as 600 microM. The compound inhibited rosette formation with nonimmune mouse lymphocytes in vitro by approximately 50 percent at 15.8 microM. The significance of this inhibition is unclear. In four in vivo tests in mice which measured humoral and cell-mediated immunity (complement-dependent cellular cytotoxicity, complement-independent cellular cytotoxicity, delayed hypersensitivity and graft versus host reaction) acyclovir showed no inhibitory effects at single doses up to 200 mg/kg given on day 2 after antigenic stimulation. Four daily doses of acyclovir at 50 mg/kg per day had no effect on the numbers of hemolytic IgM antibody-forming cells in the spleen when assayed on day 4. At the higher dosage of 100 mg/kg per day for four days, there was a slight reduction in the numbers of these cells. There was no significant decrease in hemagglutinin or hemolysin antibody titers after four daily doses of acyclovir up to 200 mg/kg.

Antirat erythrocyte agglutinins.

Antirat hemagglutinins may be found in the sera of both normal and sick persons. High titers of these antibodies are influenced by the major blood groups, the antigen B tending to suppress these antibodies, and by age where juveniles have higher titers than adults. Elevated titers may be stimulated by immunization, injection of pooled gamma-globulin, infection, and transplantation.