An isotype-specific spot-ELISA for the enumeration of antibody-secreting hybridomas and the determination of isotype switch variants

Affinity membrane identification of immunoglobulin subclass in hybridoma screening

Monoclonal hybridomas secrete immunoglobulins with a single antigen specificity and distinct class/subclass structure. Hybridoma management has commonly incorporated tests of antigen specificity into early screening procedures, but has not typically utilized assays of immunoglobulin structure. In this article, we describe a technique of class/subclass typing using polyvinylidene difluoride affinity membranes and a colorigenic enzymatic amplification system. The typing of monoclonal antibody structure was sufficiently sensitive to permit its routine use within several weeks of hybridoma fusion. The information obtained from early and routine class/subclass determinations included a semiquantitative assessment of monoclonal antibody concentration. In addition, the detection of a single immunoglobulin class/subclass in a microtiter well supernatant supported the possibility that the colony was monotypic. The application of class/subclass typing and Poisson statistics to hybridoma fusions provided a numerical estimate of the probability of colony monotypia.

Kinetics and cross-reactivity of the virus-specific antibody-forming cells in mice during primary and secondary infection with Japanese encephalitis virus and related flaviviruses

A modified antibody-forming cell assay was used to enumerate splenocytes secreting antibodies to Japanese encephalitis (JE) virus and four other flaviviruses in infected cells as the target antigens. The optimal viral antigen expression for the assay was standardized in the infected cells for each virus and the incubation time varied depending of the cell line and the virus. The kinetics of response of JE virus-infected mice readily showed IgG isotype switching. Antibody-forming splenocytes of mice primed or boosted with one flavivirus could distinguish, in variable proportions, the homologous virus antigen from heterologous ones depending on the serocomplex of the virus. Antibody-forming cells from flavivirus-infected mice were flavivirus specific as evidenced by the lack of recognition of Getah virus (alphavirus) antigen. After JE virus-infected mice were cross-primed with another flavivirus, the IgG-forming cell response resembled the secondary response to both viruses but had higher affinity to JE virus than to the cross-priming virus.

The use of chemiluminescence and the ELISA spot assay to identify and enumerate rare immunoglobulin switch variants

The use of chemiluminescence and the ELISA spot assay for identifying rare immunoglobulin switch variants is described. The technique utilizes nitrocellulose membranes and allows rapid screening of a large number of cells. The number of spots can be recorded either manually or automatically by using a commercially available colony counting program. This modification of the ELISA spot assay makes it less labor intensive and time consuming and can be adapted for the search for rare cells secreting small amounts of Ig or other macromolecules.

Cultivation of the hybridoma cell line MN12 in a homogeneous continuous culture system: effect of culture age

The stability of the hybridoma cell line MN12 in a long-term homogeneous continuous culture was studied using a panel of analytical methods. These include two flow cytometry methods, for the determination of relative cytoplasmic and membrane IgG content. In addition, the antibody production was determined by an ELISA, and the metabolic state of the cells was determined by means of glucose consumption and lactate production. These results indicate a possible selection of variants of MN12 hybridoma cells with an overall aerobic metabolism, but with a higher glucose consumption rate and a higher lactate production rate. These variants are mainly characterized by a different membrane IgG content and cytoplasmic antibody content. These changes may possibly be affected by the culture age.

Quantitation of IgE and carcinoembryonic antigen (CEA) by optical beam deflection (OBD) measurement of dot-immunobinding assay patterns visualized by an ELISA technique

Dot-immunobinding assays of IgE and CEA were performed by a conventional dot-ELISA technique with diaminobenzidine staining, and the quantitative results were compared by densitometry and a new, spectroscopic, optical beam deflection (OBD) method using the same membrane. It was possible with the OBD method to detect quantities of these substances at least ten times smaller than with densitometry. Better intra-assay reproducibility for IgE and CEA measurements was obtained by the OBD method. The measurable ranges of the OBD method was broader than that of densitometry, because dark bands caused OBD in proportion to their color densities. When the dot-immunobinding assay with OBD measurement for CEA was also compared with a microtube ELISA using biotin-avidin conjugates, the sensitivities and reproducibilities of the two methods were found to be similar, with a correlation coefficient of 0.991.

Epitope mapping and binding kinetics of monoclonal antibodies studied by real time biospecific interaction analysis using surface plasmon resonance

The interaction between human heart myoglobin and ten specific monoclonal antibodies was investigated with a new biosensor technology, real time biospecific interaction analysis (RT BIA), using surface plasmon resonance. Analysis of association and dissociation kinetics was monitored in real time, with unlabelled reactants. Antibody isotyping was rapid and simple. Epitope mapping with RT BIA confirmed, with substantial time saving, the sum of results obtained in conventional labelled systems. Monoclonal antibodies with four different epitope specificities and optimal binding function were selected for a myoglobin sandwich assay with enhanced sensitivity. BIAcore can be used directly as a diagnostic tool, or as an analytical tool in immunoassay development.

Rapid quality evaluation of hybridomas using ELISPOT and cell-ELISA techniques

We have used the ELISPOT assay in combination with ELISA procedures for rapid evaluation of properties of three different murine hybridoma cell lines, 104-I, -B and -G, secreting IgG1 kappa monoclonal antibodies against a 104-mer synthetic peptide from the C-terminal part of HIV-1 p24. By conventional ELISA we obtained data suggesting that the three monoclonal antibodies had different affinities. By cell-ELISA we found that the IgG1 kappa secretion rate varied between cells (4,000 to 14,000 antibody molecules/cell/min), and ELISPOT showed that only 4-5% of 104-I cells gave antigen-specific spots, indicating a cell population with diverse properties. We recommend that the ELISPOT and cell-ELISA techniques should be used routinely to supplement conventional ELISA procedures for rapid evaluation of hybridoma properties.

Instability of a hybridoma cell line in a homogeneous continuous perfusion culture system

In this study several analytical techniques were applied to obtain information about the stability of expression, the yield, and the integrity of a monoclonal antibody (Mab) produced by hybridoma cell line RIV6 in a homogeneous continuous perfusion culture system. The total antibody as well as the isotype-specific antibody contents decreased continuously during the course of cultivation, while the viable cell concentration remained constant. The origin of the discrepancy between the Mab contents observed by two enzyme-linked immuno sorbent assay (ELISA) systems during the steady state was due to fragmentation of the IgG molecule, either cytoplasmic or in the culture fluid, as determined by sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE) and western blotting. The IgG-secreting cells as well as the fraction of cells containing a high cytoplasmic IgG content decreased continuously during cultivation. The isoelectric focusing (IEF) pattern showed the appearance of two additional bands after five days of cultivation. This work indicates that cell line RIV6 is unstable in the culture system used, with respect to cell properties and product formation.