Increased proportion of antigen-specific antibody-producing hybridomas following an in vitro immunization with in vivo immunized mouse spleen cells

Effects of a novel anti-exospore monoclonal antibody on microsporidialNosema bombycisgermination and reproductionin vitro

A monoclonal antibody (mAb) 3C2, against an exospore protein of the microsporidiumNosema bombycis(N. bombycis) was prepared, and its effects on microsporidial germination and reproductionin vitrowere studied. MAb 3C2 was effective in inhibiting the germination and subsequent infection ofBombyx moricells compared to the control mAb. The antigen was isolated by 2-dimensional gel electrophoresis. Immunoblotting revealed it to be an 84 kDa protein corresponding to pI (7·2) on the 2-D gel. The present results suggest that the antibodies can be used for diagnostic purposes and for developing new therapeutic strategies in controlling microsporidian diseases.

Role of immunoglobulin A monoclonal antibodies against P23 in controlling murine Cryptosporidium parvum infection

Cryptosporidium parvum is an important diarrhea-causing protozoan parasite of immunocompetent and immunocompromised hosts. Immunoglobulin A (IgA) has been implicated in resistance to mucosal infections with bacteria, viruses, and parasites, but little is known about the role of IgA in the control of C. parvum infection. We assessed the role of IgA during C. parvum infection in neonatal mice. IgA-secreting hybridomas were developed by using Peyer's patch lymphocytes from BALB/c mice which had been orally inoculated with viable C. parvum oocysts. Six monoclonal antibodies (MAbs) were selected for further study based on indirect immunofluorescence assay reactivity with sporozoite and merozoite pellicles and the antigen (Ag) deposited on glass substrate by gliding sporozoites. Each MAb was secreted in dimeric form and recognized a 23-kDa sporozoite Ag in Western immunoblots. The Ag recognized comigrated in sodium dodecyl sulfate-polyacrylamide gel electrophoresis with P23, a previously defined neutralization-sensitive zoite pellicle Ag. MAbs were evaluated for prophylactic or therapeutic efficacy against C. parvum, singly and in combinations, in neonatal BALB/c mice. A combination of two MAbs given prophylactically prior to and 12 h following oocyst challenge reduced the number of intestinal parasites scored histologically by 21.1% compared to the numbers in mice given an isotype-matched control MAb (P < 0.01). Individual MAbs given therapeutically in nine doses over a 96-h period following oocyst challenge increased efficacy against C. parvum infection. Four MAbs given therapeutically each reduced intestinal infection 34.4 to 42.2% compared to isotype-matched control MAb-treated mice (P < 0.05). One MAb reduced infection 63.3 and 72. 7% in replicate experiments compared to isotype-matched control MAb-treated mice (P < 0.0001). We conclude that IgA MAbs directed to neutralization-sensitive P23 epitopes may have utility in passive immunization against murine C. parvum infection.

Simple diagnosis of Encephalitozoon sp. microsporidial infections by using a panspecific antiexospore monoclonal antibody

Microsporidia (phylum Microsproa) have recently become recognized as common opportunistic protozoans in the United States and worldwide, particularly affecting immunodeficient patients. Microsporidian organisms within the genus Encephalitozoon are the cause of nephrologic, ophthalmic, pneumologic, gastroenteric, and systemic infections. However, diagnosis of the small spores by light microscopy is difficult, even with newly developed and improved staining techniques. We have developed an anti-Encephalitozoon species monoclonal antibody-based immunoassay for easy diagnosis. A hybridoma was produced and selected following one main criterion: recognition by immunofluorescence of all known Encephalitozoon spores affecting humans. The selected monoclonal antibody-secreting hybridomas were characterized by enzyme-linked immunosorbent assay, immunofluorescence, Western blot, and immunoelectron microscopy using Encephalitozoon species from fresh and fixed samples from patients and from in vitro cultures. In the immunofluorescence assay, one monoclonal antibody, termed 3B6, strongly recognized Encephalitozoon cuniculi, E. hellem, and E. intestinalis. Monoclonal antibody 3B6 bound to other microsporidia (Nosema and Vairimorpha spp.) without cross-reacting with any other parasite, including Enterocytozoon bieneusi, fungus, or bacterium tested. In immunoelectron microscopy assays, monoclonal antibody 3B6 bound to the exospore of Encephalitozoon species, while in Western blot assays, it recognized three to seven antigens with molecular masses ranging from 34 to 117 kDa. We have developed a sensitive and specific monoclonal antibody-based immunoassay to diagnose common microsporidian infections, particularly with Encephalitozoon species. This is a new tool for identifying spores in bodily fluids and biopsy samples and is an efficient diagnostic test. Additionally, monoclonal antibody 3B6 can serve to assess the prevalence of microsporidial infections in immunodeficient and immunocompetent patients.

New approaches for the development and application of monoclonal antibodies for the diagnosis and therapy of human cancer

Monoclonal antibodies (MAbs) represent potentially important reagents for both the diagnosis and therapy of human cancer. Innovative approaches are resulting in the improved production of MAbs and an enhanced ability to use these molecules therapeutically. Application of genetic engineering to MAb development is also resulting in the production of MAbs displaying enhanced target specificity. Of particular value for cancer therapy will be catalytic, bispecific, anti-idiotypic and human MAbs. By using agents that can augment the expression of tumor-associated antigens on cancer cells, a further increase in the utility of MAbs in cancer therapy will be forthcoming.

Absence of monoclonal antibody detectable Kaposi sarcoma-specific antigens on lesion-derived cultured cells

To define the histogenesis and cell origin of Kaposi sarcoma (KS), we cultured KS cells without retrovirally conditioned media from three HIV seropositive AIDS patients and then attempted to raise mouse hybrid monoclonal antibodies (Mabs) specific to these AIDS-KS cells. After both in vivo and in vitro immunization trials, all putative Mabs reacted positively to KS cells but also non-specifically with other human (CH5 and OM) and non-human (RSE-1) control endothelial cell lines. To overcome this crossreactivity, we further "absorbed" previously cloned hybrids and pre-hybrid splenocytes by incubating them with the control endothelial cell lines to eliminate splenocytes and/or hybridomas reactive to normal endothelium. Whereas absorption successfully eliminated immunoreactivity to control endothelium, it also excluded reactivity to KS cells. These findings (lack of specific antigenicity and immunoresponsiveness of KS similar to non-KS control endothelium) suggest that AIDS-KS cells are neither antigenically transformed nor neoplastic, but instead represent dedifferentiated or transdifferentiated endothelium which retains immunogenicity of its original endothelial cell prototype.