James W. Rohrer

EXPRESSION AND IMMUNOGENICITY OF ONCOFETAL ANTIGEN-IMMATURE LAMININ RECEPTOR IN HUMAN RENAL CELL CARCINOMA

PURPOSE The 32 to 44 kDa. oncofetal antigen-immature laminin receptor (OFA-iLR) is a multifunctional protein expressed by various tumors, including breast, lung, ovary and prostate carcinoma as well as lymphoma. OFA-iLR has been implicated in tumor invasiveness, metastasis and growth. Interferon-gamma producing effector T cells and interleukin (IL)-10 producing suppressor T cells specific for OFA-iLR have been described. MATERIALS AND METHODS The 43515 IgG2a anti-OFA-iLR monoclonal antibody was used to detect OFA-iLR expression in human renal cell carcinoma tissue by flow cytometry and immunoblotting. Spontaneous or therapy induced immune responses against OFA-iLR were determined in patients with metastatic renal cell carcinoma. Proliferative and cytokine (interferon-gamma and IL-10) responses of peripheral blood mononuclear cells from patients with renal cell carcinoma against recombinant OFA-iLR were assessed. RESULTS Using flow cytometry OFA-iLR was detected in all 13 tumors tested. Immunoblotting revealed differences in OFA-iLR expression in renal cell carcinoma and normal kidney tissue. OFA-iLR specific proliferative and cytokine responses of mononuclear cells were detected in all 6 patients tested. Importantly evidence was also obtained that treating metastatic renal cell carcinoma with tumor lysate pulsed dendritic cells would enhance OFA-iLR specific immunity. CONCLUSIONS This study demonstrates that OFA-iLR is an immunogenic tumor associated antigen in human renal cell carcinoma. OFA-iLR specific effector T cells producing interferon-gamma may have a role in the control of tumor growth, whereas suppressor T cells producing IL-10 may promote tumor tolerance and, thus, tumor progression.

Tumors express both unique TSTA and crossprotective 44 kDa oncofetal antigen.

Abstract Tumors of inbred rodents and humans generally express a shared tumor-associated transplantation antigen (TATA)-like oncofetal antigen (OFA) and tumor-specific transplantation antigen (TSTA), which stimulate cytotoxic T lymphocyte (CTL) tumor rejection responses. Immunoregulatory CD8 + OFA-specific suppressor T cells are also stimulated, which promote tumor development via interleukin 10 secretion, inhibiting CTL function. Here, Joseph Coggin and colleagues argue that future investigations must distinguish responses to OFA and TSTA.

Identification of Oncofetal Antigen/Immature Laminin Receptor Protein Epitopes That Activate BALB/c Mouse OFA/iLRP-Specific Effector and Regulatory T Cell Clones

During tumor development in mice and humans, oncofetal Ag/immature laminin receptor (OFA/iLRP)-specific Th1, CTL, and IL-10-secreting T (Ts) cells are induced. The presence of too many Ts or too few effector T cells appears to predict a poor prognosis. We established clones of OFA/iLRP-specific splenic Th1, CTL, and Ts cells from the OFA/iLRP+ MCA1315 fibrosarcoma-bearing BALB/c mice or from BALB/c mice vaccinated with 1 or 10 μg of rOFA/iLRP. The MCA1315 tumor cell-reactive T cell clones were characterized as to surface Ag phenotype, cytokine secretion profile, and specificity for OFA/iLRP presented by syngeneic splenic APC. OFA/iLRP-specific Th1 and Ts clones were established from all mice. OFA/iLRP-specific CTL could be established from all mice except for mice immunized with 10 μg of rOFA/iLRP. Analysis of the proliferation profile of the OFA/iLRP-specific clones to overlapping OFA/iLRP 12-mer peptides that spanned the OFA/iLRP protein sequence defined the epitopes to which the T cell clones responded. There was a similar spatial distribution of the epitopes to which the two types of CD8 T cell clones responded. The nonapeptide epitopes of the Ts clones were located between aa 36 and 147 of OFA/iLRP, while the epitopes of the CTL clones were located between aa 52 and 163. Even though the CTL and Ts epitopes shared part of the protein, all of the CD8 CTL epitopes were distinct and separable from those of CD8 Ts cells.

Lyb3: A B Cell Surface Antigen Associated with Triggering Secretory Differentiation1

The results discussed in this review show that the TNP-specific IgA lambda 2-secreting BALB/c plasmacytoma MOPC-315 is partially composed of small lymphocytoid, presecretory cells which express the Lyb3 determinant. It is shown that MOPC-315 cell secretory differentiation, but not clonal proliferation, can be modulated by anti-Lyb3. Anti-Lyb3 serum has been shown to: 1) augment secretory differentiation enhancement by suboptimal numbers of secretory differentiation-enhancing, IgA315-specific helper T cells; 2) replace this secretory differentiation-enhancing T cell population as long as clone growth helper T cells are present; and 3) block suppression of secretory differentiation mediated by carrier-immune Ts cells. These results demonstrate that whether anti-Lyb3 serum enhances immune responses by replacing or augmenting a helper signal or by counteracting suppressor signals, the effects are focused on secretory differentiation events and have no effect on clonal proliferation.

Production, safety and antitumor efficacy of recombinant Oncofetal Antigen/immature laminin receptor protein.

We describe here for the first time an efficient high yield production method for clinical grade recombinant human Oncofetal Antigen/immature laminin receptor protein (OFA/iLRP). We also demonstrate significant antitumor activity for this protein when administered in liposomal delivery form in a murine model of syngeneic fibrosarcoma. OFA/iLRP is a therapeutically very promising universal tumor antigen that is expressed in all mammalian solid tumors tested so far. We have cloned the human OFA/iLRP cDNA in a bacterial expression plasmid which incorporates a 6x HIS-tag. Large scale cultures of the plasmid transformed Escherichia coli were performed and the crude HIS-tagged OFA/iLRP was isolated as inclusion bodies and solubilized in guanidine chloride. The protein was then purified by successive passage through three column chromatography steps of immobilized metal affinity, anion exchange, and gel filtration. The resulting protein was 94% pure and practically devoid of endotoxin and host cell protein. The purified OFA/iLRP was tested in mice for safety and efficacy in tumor rejection with satisfactory results. This protein will be used for loading onto autologous dendritic cells in an FDA approved phase I/II human cancer vaccine trial in OFA/iLRP-positive breast cancer patients.

True Immunogenicity of Oncofetal Antigen/Immature Laminin Receptor Protein

Su et al . [(1)][1] described the detection of RNA present in renal cell carcinoma (RCC) that achieved expression of oncofetal antigen (OFA) in RCC patient’s monocytes and gave rise to OFA-expressing dendritic cells ex vivo . When these OFA-expressing dendritic cells were infused back into

Distinct Populations of SRBC-Immune Suppressor Cells Control B Cell Clone Growth and Secretory Differentiation

ABSTRACT. Growth and secretory differentiation of the anti-TNP IgA (M315)-secreting mouse myeloma MOPC-315 are suppressed by SRBC-immune T cells in the presence of TNP-SRBC. At least two populations of SRBC-immune T S cells mediate this suppression. One population specifically recognizes both M315 and SRBC determinants and selectively suppresses 315 cell secretory differentiation in the presence of SRBC; haptenation is irrelevant. The other population is carrier-specific, lacks receptors for M315 idiotopes, and suppresses both 315 clone growth and secretory differentiation in the presence of TNP-SRBC (i.e., a hapten-carrier bridge is required).