Production of human monoclonal IgG antibodies reacting with cytomegalovirus (CMV)

Evaluation of the fusion partner cell line SPYMEG for obtaining human monoclonal antibodies against influenza B virus

Influenza B virus has been known to infect humans and other animals, including seals. Vaccination efficacy varies across seasons. Human monoclonal antibodies (mAbs) can be useful for developing novel vaccines, guided by epitope analysis, and can be used therapeutically. Hybridoma technology has been used to make mAbs. Here we evaluated SPYMEG as a fusion partner cell line for human mAb generation specific to influenza B hemagglutinin (HA). SPYMEG is a human/murine myeloma partner cell line that has previously been used to generate human mAbs that recognize the HA of influenza A and B viruses. Peripheral blood mononuclear cells were obtained from 16 volunteers, previously vaccinated with the 2014–2015 trivalent seasonal influenza vaccine, and were fused with SPYMEG to yield hybridomas. The resulting hybridomas were screened for antigen-specific antibody secretion and cloned by limiting dilution. We obtained 32 stable clones secreting anti-influenza B HA human IgG, although most of these clones were obtained from one volunteer (SeaV-29) who had a robust immune response. We conclude that SPYMEG is a good fusion partner cell line, although cloning by limiting dilution may lead to significant loss of hybridomas.

Exploring the native human antibody repertoire to create antiviral therapeutics

Native human antibodies are defined as those that arise naturally as the result of the functioning of an intact human immune system. The utility of native antibodies for the treatment of human viral diseases has been established through experience with hyperimmune human globulins. Native antibodies, as a class, differ in some respects from those obtained by recombinant library methods (phage or transgenic mouse) and possess distinct properties that may make them ideal therapeutics for human viral diseases. Methods for cloning native human antibodies have been beset by technical problems, yet many antibodies specific for viral antigens have been cloned. In the present review, we discuss native human antibodies and ongoing improvements in cloning methods that should facilitate the creation of novel, potent antiviral therapeutics obtained from the native human antibody repertoire.

Production and analysis of IgG monoclonal anti-DNA antibodies from systemic lupus erythematosus (SLE) patients

This study compares recently devised methods for producing IgG anti-DNA MoAbs from patients with SLE and analyses the antibodies generated from one patient at different phases of disease. Lymphocytes from SLE patients were transformed with Epstein-Barr virus(EBV) and/or fused with a heteromyeloma cell line, CB-F7. Direct fusion with CB-F7 resulted in the highest proportion of IgG-secreting lines, whereas EBV transformation resulted in a high percentage of IgM-secreting lines. Using direct fusion, five IgM anti-DNA antibody-secreting hybridomas were generated using lymphocytes from a patient with relatively inactive SLE. Six months later when the disease was active, only IgG anti-DNA antibodies were produced. The antigen-binding patterns of the MoAbs were analysed. Only one of the IgM anti-DNA antibodies reacted with dsDNA by ELISA and none by Crithidia immunofluorescence, whereas two of the IgG antibodies reacted with dsDNA by ELISA and Crithidia but did not bind to ssDNA. Only the two IgG high affinity anti-dsDNA antibodies bound to histones, and this was enhanced by added DNA, whereas three IgM antibodies bound to cardiolipin. This study supports the notion that MoAbs derived from a patient with SLE represent those found in the serum of SLE patients at different stages of disease activity. The binding to histones by the two IgG anti-dsDNA antibodies supports the recently expressed view that antibodies binding DNA/histone may be important in the pathogenesis of SLE.

Development of human monoclonal antibodies against human cytomegalovirus

Human monoclonal antibodies (HMAbs) against human cytomegalovirus (HCMV) have been developed by fusion of human spleen cells and human lymphoblastoid cell lines (NP101 and NP197). The cell line NP101 had great advantages in its high fusion frequency and the stability of the resultant hybridomas. The specificity of HMAbs was confirmed by enzyme-linked immunosorbent assay (ELISA) and immunofluorescence staining. Two of the six HMAbs obtained, which were IgG3 subclass, neutralized viral infectivity in the absence of complement. The neutralizing activity of one of these two HMAbs was enhanced in the presence of human complement, whereas the other was not. Another IgG1 subclass HMAb neutralized viral infection only in the presence of complement. The remaining three HMAbs showed no neutralizing activity. Those HMAbs may provide an important approach to studying human immune responses to HCMV. HMAbs having neutralizing activity may prove to be useful for passive immunotherapy of HCMV diseases.

Influence of somatic cell hybridization and human serum on the generation and stability of human hybridomas

We describe an approach that allows the generation of stable hybridomas secreting antigen specific human IgG antibodies with an efficiency comparable to that of the generation of IgM and IgA secreting hybridomas. This was achieved by evaluating means to increase the frequency of human hybridoma formation and the stability of the generated hybridoma cells when subjected to conditions for large scale growth. To this end, we generated new fusion lines with an increased human DNA content and modified the culture system. However, the application of these new fusion lines primarily resulted in unstable giant cells. As a consequence, we evaluated whether the viability of newly formed hybrids between existing fusion lines and lymphoblastoid cell lines might be improved. In an attempt to provide as many components necessary for the growth of antibody secreting hybridomas as possible, we propagated fused cells in medium supplemented with human serum. Our results show that with this approach the frequency of initially growing hybrids was significantly increased. Furthermore, only in culture medium supplemented with human serum was it possible to obtain stable IgG secreting clones.