A rapid and quantitative method for the evaluation of V gene usage, specificities and the clonal size of B cell repertoires

The quantitative simultaneous description of both variable region gene usage and antigen specificity of immunoglobulin repertoires is a major goal in immunology. Current quantitative assays are labor intensive and depend on extensive gene expression cloning prior to screening for antigen specificity. Here we describe an alternative method based on high efficiency single B cell cultures coupled with RT-PCR that can be used for rapid characterization of immunoglobulin gene segment usage, clonal size and antigen specificity. This simplified approach should facilitate the study of antibody repertoires expressed by defined B cell subpopulations, the analysis of immune responses to self and nonself-antigens, the development and screening of synthetic antibodies and the accelerated study and screening of neutralizing antibodies to pathogenic threats.

Genetic control of the B cell response to LPS: opposing effects in peritoneal versus splenic B cell populations

Lipopolysaccharide (LPS) from gram-negative bacteria activates B cells, enabling them to proliferate and differentiate into plasma cells. This response is critically dependent on the expression of TLR4; but other genes, such as RP105 and MHC class II, have also been shown to contribute to B cell LPS response. Here, we have evaluated the role of genetic control of the B cell response to LPS at the single cell level. We compared the response to LPS of peritoneal cavity (PEC) and splenic B cells on the BALB/c genetic background (LPS-low responder) to those on the C57BL/6J background (LPS-high responder) and their F1 progeny (CB6F1). Both PEC and splenic B cells from B6 exhibited 100% clonal growth in the presence of LPS; whereas, BALB/c PEC and splenic B cells achieved only 50% and 23% clonal growth, respectively. Adding CpG to the LPS stimulus pushed PEC B cell clonal growth in the low responder strain BALB/c up to 90%, showing that the nonresponse to LPS is a specific effect. Surprisingly, PEC B cells on the F1 background behaved as high responders, while splenic B cells behaved as low responders to LPS. The data presented here reveals a previous unsuspected behavior in the genetic control of the B cell response to LPS with an opposing impact in splenic versus peritoneal cavity B cells. These results suggest the existence of an, as yet, unidentified genetic factor exclusively expressed by coelomic B cells that contributes to the control of the LPS signaling pathway in the B lymphocyte.

Identification of highly specific and cross-reactive antigens of Leishmania species by antibodies from Leishmania (Leishmania) chagasi naturally infected dogs

The Leishmania species present a genetic homology that ranges from 69 to 90%. Because of this homology, heterologous antigens have been used in the immunodiagnosis and vaccine development against Leishmania infections. In the current work, we describe the identification of species-specific and cross-reactive antigens among several New World Leishmania species, using symptomatic and asymptomatic naturally Leishmania chagasi-infected dog sera. Soluble antigens from five strains of New World Leishmania were separated by electrophoresis in SDS-PAGE and immunoblotted. Different proteins were uniquely recognized in the L. chagasi panel by either symptomatic or asymptomatic dog sera suggesting their use as markers for the progression of disease and diagnosis of the initial (sub-clinical) phase of the infection. Cross-reactive antigens were identified using heterologous antigenic panels (L. amazonensis strains PH8 and BH6, L. guyanensis and L. braziliensis). L. guyanensis panel showed the highest cross-reactivity against L. chagasi specific antibodies, suggesting that proteins from this extract might be suitable for the diagnosis of visceral canine leishmaniasis. Interestingly, the 51 and 97 kDa proteins of Leishmania were widely recognized (77.8% to 100%) among all antigenic panels tested, supporting their potential use for immunodiagnosis. Finally, we identified several leishmanial antigens that might be useful for routine diagnosis and seroepidemiological studies of the visceral canine leishmaniasis.

Flow cytometric assay in peripheral blood of dogs--reference values for leukocytes from Brazilian beagles

Use of domestic reference values in the flow cytometry analysis is known to improve its accuracy by integrating local variations as gender, race and age. Up to date application of flow cytometry in veterinary medicine has been limited to describe the percentual values just for peripheral lymphocytes subsets of blood. We now report establishment of reference values for a wide range of proportional and absolute numbers of peripheral blood leukocytes, including T cells subsets, B cells, monocytes and eosinophils, applicable to the healthy population of Beagles in Brazil and other regions with similar demographic characteristics. Normal reference values were also established to estimate the gender-related differences. This information will provide clinical aid in the evaluation of immunologic status as well as standard values for experimental animals of dogs from Brazil and other similar regions.

[The first assessment of hepatitis E virus seroprevalence in northern Portugal]

Hepatitis E is an enterically transmitted acute viral hepatitis, etiologically associated with a recently characterized virus, the hepatitis E virus (HEV). Outbreaks mainly occur in developing countries and as sporadic cases in endemic regions. The authors present the first serological assessment in northern Portugal to assess the presence of anti HEV IgG, using the Elisa test, the EIA and HEV Abbott, in samples from 50 blood donors and 103 chronic liver disease patients. In 2 blood donors (4%) and in 7 (6.8%) liver patients, the HEV antibody was detected with optic densities/cut off always below 2.5. Only one patient had a sojourn in an endemic region; the presence of anti-HEV was not significantly associated with other hepatotropic viruses. With this test the authors conclude that 4% of our blood donors are seropositive for anti-HEV antibody and that this percentage is not significantly higher in chronic liver disease patients (6.8%). They also think that a new generation of immunological assays, designed for serological diagnosis of HEV infection, will provide a further understanding of hepatitis E epidemiology.

Diamine oxidase in the diagnosis of ruptured fetal membranes

Diamine oxidase activity is present in amniotic fluid but absent from vaginal secretions, providing a method for diagnosing rupture of membranes. Vaginal secretions were absorbed onto sterile paper strips, eluted, and assayed for diamine oxidase activity. Interfering substances included maternal serum, iodine antiseptics, and large amounts of meconium. Two of 109 prenatal clinic (negative control) specimens displayed measurable diamine oxidase activity; one of 144 postamniotomy (positive control) specimens had no diamine oxidase activity. Of 75 test specimens obtained by speculum examination and 488 test specimens obtained without the aid of a speculum, 18 and 62, respectively, displayed a diamine oxidase test result different from results of conventional tests (nitrazine paper, ferning, fetal cell stains). These discrepancies are discussed in view of the utility of the diamine oxidase test as an adjunct to conventional methods for diagnosing rupture of membranes. The diamine oxidase test appears to be objective, sensitive, quantitative, and capable of detecting amniotic fluid leaks more than 25 hours after rupture of membranes. It can be performed in 1 hour and requires a scintillation counter.

Maternal serum diamine oxidase in fetal death and low-birth-weight infants

Serum diamine oxidase was measured at different gestational ages in 681 pregnancies resulting in live births and 102 pregnancies resulting in fetal deaths. Statistical analysis revealed that gestational age-adjusted diamine oxidase levels in the fetal-death group were significantly lower (P less than 0.001) than those in the live-birth group. Moreover, the relative risk associated with a low diamine oxidase level, compared with a normal level, increased from 3.7 at 8 weeks to 16.6 at 12 weeks. Pregnancies resulting in low-birth-weight infants exhibited normal serum diamine oxidase levels. The association between low diamine oxidase and subsequent fetal death is discussed in view of the hypothesis that polyamines and polyamine-degrading enzymes interact to protect the fetoplacental unit from immune rejection.

Spermidine oxidase in human pregnancy serum. Probable identity with diamine oxidase

Diamine oxidase was previously measured in human pregnancy serum with putrescine or histamine as substrate. We have now documented the presence of spermidine oxidase activity in pregnancy serum by means of a specific radioactive assay with [14C]spermidine as substrate and Dowex 50 cation-exchange chromatography to separate products from substrate. The apparent Km of a partially purified preparation of this enzyme for spermidine was 10.9 microM and the Ki for aminoguanidine was 0.8 microM. The pH optimum (pH 9.0) and temperature optimum (55 degrees C) were identical with those for diamine oxidase. Spermidine oxidase activity and diamine oxidase activity eluted in a concerted fashion when pregnancy serum was subjected to cadaverine-Sepharose chromatography, gel filtration and ion-exchange chromatography. Spermidine oxidase became detectable in serum during pregnancy in the human approx. 8 weeks after the last menstrual period and increased with gestational age in concert with the increase in diamine oxidase activity, reaching a plateau at 20 weeks of gestation. Foetal-cord serum displayed virtually no activity of either enzyme. A 400-fold-purified preparation of diamine oxidase retained the same diamine oxidase/spermidine oxidase ratio as exhibited by crude pregnancy serum. These data suggest that in pregnancy serum, unlike foetal bovine serum, spermidine oxidase and diamine oxidase activity may be a single enzyme protein.

Separation of putrescine oxidase and spermidine oxidase in foetal bovine serum with the aid of a specific radioactive assay of spermidine oxidase

1. A sensitive and specific assay for spermidine oxidase is described. The method involves the separation of [14C]spermidine (substrate) from [14C]putrescine (product) and other 14C-labelled products on a Dowex 50 cation-exchange column: 92% of the putrescine applied to the column was eluted by 2.3 M-HCl, but this treatment left 96% of the spermidine bound to the column. Unchanged spermidine could be removed from the column by elution with 6 M-HCl. 2. By means of this assay, foetal and adult bovine serum were each shown to contain spermidine oxidase activity, putrescine being a major product of the oxidation of spermidine by the serum enzymes. 3. In foetal bovine serum, spermidine oxidase activity is separable from putrescine oxidase activity by chromatography on a cadaverine-Sephadex column, by gel filtration and by ion-exchange column chromatography. Putrescine oxidase was purified 1900-fold and spermidine oxidase 130-fold by these procedures. The former oxidized putrescine but not spermidine, and spermidine oxidase exhibited no activity with putrescine as substrate.