Anti-idiotypic antibody (ab2) vaccines: coupling of Ab2 BR3E4 to KLH increases humoral and/or cellular immune responses in animals and colorectal cancer patients.

The colorectal carcinoma (CRC)-associated CO17-1A/GA733 antigen (Ag) has been the target of a phase II/III randomized trial of passive immunotherapy with monoclonal antibody CO17-1A (Ab1), and phase I active immunotherapy trials with polyclonal anti-idiotypic antibodies (Ab2) mimicking the CO17-1A or GA733 epitope of the Ag. However, monoclonal rat Ab2 BR3E4 directed against Ab1 CO17-1A was superior to polyclonal Ab2 in inducing antigen-specific humoral and cellular immune responses in mice and rabbits. Various forms of Ab2 BR3E4, i.e., BR3E4-F(ab')2 precipitated with aluminum-hydroxide (alum), BR3E4-F(ab')2 coupled to KLH and precipitated or non-precipitated with alum, and BR3E4-IgG in alum or incomplete Freund's adjuvant were compared for their capacity to induce in rabbits anti-anti-idiotypic antibodies (Ab3) that specifically bind to the CO17-1A Ag. BR3E4-F(ab')2 coupled to KLH and precipitated with alum was shown to induce the highest Ab3 titers, followed by Ab2 BR3E4-IgG in alum. Therefore Ab2 BR3E4 as intact IgG (IgG group) or as F(ab')2 coupled to KLH (KLH group), was administered in a phase I trial to 45 patients with CRC, stage Dukes'D (UICC stage IV), with the goal to modulate patients' immune responses to their tumors. Fifteen of 23 patients in the IgG group developed Ab3 binding specifically to Ab2, and in four of these patients the Ab3 also specifically bound to Ag-positive CRC cells. Lymphoproliferative responses to Ab2 and/or GA733-2E Ag stimulation were observed in three of these patients. Eighteen of the 22 KLH group patients tested developed Ab3 and the Ab3 bound specifically to CRC cells in eight patients. Five of the 15 KLH group patients tested developed lymphoproliferative responses to Ab2 and/or GA733-2E Ag. Thus, there was a trend for the KLH group demonstrating higher immune response rates than the IgG group. Clinical responses were rare in these patients with liver metastases.

Cancer vaccines: single-epitope anti-idiotype vaccine versus multiple-epitope antigen vaccine.

In this study, we compared the immunogenicity and tumor-protective activity of anti-idiotypic antibodies mimicking a single tumor-associated epitope and tumor-associated antigen expressing multiple potentially immunogenic epitopes. We focused our study on the colorectal-carcinoma(CRC)-associated antigen GA733 (also known as CO17-1A/KS1-4/KSA/EpCAM). Monoclonal anti-idiotypic antibody (Ab2) BR3E4 was produced against murine anti-CRC mAb CO17-1A (Ab1) in rats. Full-length native GA733 protein was isolated from human tumor cells, and the extracellular domain protein (GA733-2E) was isolated from supernatants of recombinant baculovirus-infected insect cells by immunoaffinity chromatography. The immunomodulatory activity of the Ab2 was compared with that of the antigen, both in rabbits and in mice. Mice, like humans but not rabbits, express a GA733 antigen homologue on some of their normal tissues. Thus, these in vivo models allow the comparison of the immunogenicity of Ab2 and antigen in the presence (mice) and absence (rabbits) of normal tissue expression and immunological tolerance of the GA733 antigen homologue. In rabbits, aluminum-hydroxide(alum)-precipitated native GA733 antigen was superior to alum-precipitated Ab2 in inducing specific humoral immunity. In mice, alum-precipitated recombinant GA733-2E antigen, but not alum-precipitated Ab2, induced specific humoral immunity. However, when the Ab2 was administered to mice in Freund's complete adjuvant, specific humoral immune responses were elicited. Ab2 in complete Freund's adjuvant and GA733-2E in alum were compared for their capacity to induce antigen-specific cellular immunity in mice. Whereas lymphoproliferative responses were obtained with the recombinant antigen only, delayed-type hypersensitivity responses were obtained with both recombinant antigen and Ab2, although these responses were lower than after antigen immunization. The recombinant antigen in alum did not protect mice against challenge with antigen-positive syngeneic murine CRC cells. Similar studies with Ab2 BR3E4 mimicking the CO17-1A epitope were not possible because the tumor cells do not express this epitope after transfection with the human GA733-2 cDNA. However, similar studies with Ab2 mimicking the epitope defined by mAb GA733, which is expressed by the transfected tumor cells, indicated a lack of tumor-protective activity of this Ab2. In contrast, the full-length antigen expressed by recombinant adenovirus inhibited the growth of established tumors in mice. In conclusion, soluble antigen is a more potent modulator of humoral and cellular immune responses than Ab2, both administered in adjuvant. However, for induction of protective immunity, the immunogenicity of the antigen must be further enhanced, e.g., by expression of the antigen in a viral vector.

Expression of an antigen homologous to the human CO17-1A/GA733 colon cancer antigen in animal tissues.

The CO17-1A/GA733 antigen is associated with human carcinomas and some normal epithelial tissues. This antigen has shown promise as a target in approaches to passive and active immunotherapy of colorectal cancer. The relevance of animal models for studies of immunotherapy targeting this antigen in patients is dependent on the expression of the antigen on normal animal tissues. Immunohistoperoxidase staining with polyclonal rabbit antibodies to the human antigen revealed the human homologue on normal small intestine, colon and liver of mice, rats and non-human primates, whereas mouse monoclonal antibodies to the CO17-1A or GA733 epitopes on the human antigen did not detect the antigen. Polyclonal rabbit antibodies, elicited by the murine antigen homologue derived from recombinant baculovirus-infected insect cells, immunoprecipitated the antigen from mouse small intestine, colon, stomach, kidney and lung. The isolated recombinant murine protein bound polyclonal, but not monoclonal, antibodies to the human CO17-1A/GA733 antigen, and recombinant human antigen bound polyclonal antibodies elicited by the murine antigen homologue. Thus, the antigen homologue expressed by animal tissues is similar, but not identical, to the human antigen. These results have important implications for experimental active and passive immunotherapy targeting the CO17-1A/GA733 antigen.

Monoclonal anti-idiotypic antibody functionally mimics the human gastrointestinal carcinoma epitope GA733.

Anti-idiotypic antibodies (Ab2) that bind to the antigen-combining region of anti-tumor antibodies (Ab1) may functionally, and even structurally, mimic tumor antigen. We have previously demonstrated that polyclonal goat Ab2 directed against anti-human gastrointestinal carcinoma Ab1 GA733 induces anti-anti-idiotypic antibodies (Ab3) in animals that are Ab1-like in their binding specificity and idiotope expression. To obtain more defined Ab2 vaccines with potentially increased specificity and efficacy, a monoclonal Ab2 (FG1) was produced against Ab1 GA733 in rats. The monoclonal Ab2 FG1, similar to the polyclonal Ab2 described previously, induced Ab3 in rabbits that were Ab1-like in their idiotope expression and binding specificity to tumor cells and antigen. Antigen-specific Ab3 induced by Ab2 FG1 were easily detected in unprocessed rabbit sera, whereas the demonstration of such Ab3 after polyclonal Ab2 immunization required purification of the Ab3 from the rabbit sera. In addition, Ab2 FG1 induced antigen-specific humoral and cellular immunity in mice. Murine Ab3 bound specifically to antigen-positive tumor cells. Ab2-immunized mice showed antigen-specific delayed-type hypersensitivity (DTH) reaction, and cultured splenocytes from the immune mice demonstrated specific proliferation and cytokine (interferon-gamma and interleukin-4) secretion upon stimulation with GA733 antigen. However, immune mice were not protected against a challenge with syngeneic GA733 antigen-expressing colon carcinoma cells.

[Multiple meningiomas of thoracic spinal cord: report of two cases].

Multiple spinal meningiomas are relatively rare and account for from only 2 to 3.5% of all spinal meningiomas. Two cases of multiple meningiomas of the thoracic spinal cord were reported. Case 1. A 73-year-old woman was admitted with a 5 month history of progressive motor weakness and sensory disturbance in the legs bilaterally. Neurological findings on admission revealed paraparesis, hypesthesia and hypalgesia under the Th10 level, hyperreflexia of both legs, and urinary incontinence. Myelography and MRI revealed two intradural extramedullary lesions at the Th7 and Th10 level. Both tumors were removed completely. Histopathological examination showed psammomatous meningiomas. Case 2. A 52-year-old man was admitted with a 2 month history of progressive motor weakness and numbness of both legs. Neurological findings on admission revealed paraparesis, hypesthesia and hypalgesia under the Th10 level, hyperreflexia of both legs, and genitourinary incontinence. Lumbar myelography showed complete block at the Th9 level. MRI showed stenosis of the spinal canal at the Th8/9 level, and a deviation of the spinal cord. MRI with Gd-DTPA showed that the spinal cord was compressed by intradural extramedullary tumors. However, myelography and MRI could not detect the multiplicity of tumors. CT myelography demonstrated three separate tumors from the Th7 to the Th9. Three tumors were totally removed. Histopathologically, they were meningotheliomatous meningiomas. These cases were considered as being multiple meningiomas of the spine. Both patients showed no manifestations of von Recklinghausen's disease. The cause of the multiplicity in these cases was uncertain. Multiple spinal tumor is very difficult to diagnose because of unusual clinical symptoms.(ABSTRACT TRUNCATED AT 250 WORDS)