The RM27-3E5 monoclonal antibody reacts with mouse CD27, a 45 kDa type I transmembrane protein and a member of the TNF superfamily. CD27 is expressed on peripheral T cells, memory B cells, NK cells, and a subset of thymocytes. CD27 is highly induced on T cells after TCR stimulation. CD70 is a ligand for CD27. Interaction with CD70 provides co-stimulation in T cells and induces signaling events essential for cell proliferation, long-term maintenance of antigen-specific T cells, antiviral responses, antitumor immunity, and alloreactivity. Agonistic antibodies that stimulate CD27 are currently being explored as experimental cancer treatments. The RM27-3E5 antibody is an agonistic antibody that stimulates CD27 upon binding. 

INVIVOMAB ANTI-MOUSE CD27

Ahrends, T., et al. (2017). “CD4(+) T Cell Help Confers a Cytotoxic T Cell Effector Program Including Coinhibitory Receptor Downregulation and Increased Tissue Invasiveness.” Immunity 47(5): 848-861 e845. PubMed

CD4(+) T cells optimize the cytotoxic T cell (CTL) response in magnitude and quality, by unknown molecular mechanisms. We here present the transcriptomic changes in CTLs resulting from CD4(+) T cell help after anti-cancer vaccination or virus infection. The gene expression signatures revealed that CD4(+) T cell help during priming optimized CTLs in expression of cytotoxic effector molecules and many other functions that ensured efficacy of CTLs throughout their life cycle. Key features included downregulation of PD-1 and other coinhibitory receptors that impede CTL activity, and increased motility and migration capacities. “Helped” CTLs acquired chemokine receptors that helped them reach their tumor target tissue and metalloprotease activity that enabled them to invade into tumor tissue. A very large part of the “help” program was instilled in CD8(+) T cells via CD27 costimulation. The help program thus enhances specific CTL effector functions in response to vaccination or a virus infection.

Ahrends, T., et al. (2016). “CD27 Agonism Plus PD-1 Blockade Recapitulates CD4+ T-cell Help in Therapeutic Anticancer Vaccination.” Cancer Res 76(10): 2921-2931. PubMed

While showing promise, vaccination strategies to treat cancer require further optimization. Likely barriers to efficacy involve cancer-associated immunosuppression and peripheral tolerance, which limit the generation of effective vaccine-specific cytotoxic T lymphocytes (CTL). Because CD4(+) T cells improve CTL responsiveness, next-generation vaccines include helper epitopes. Here, we demonstrate in mice how CD4(+) T-cell help optimizes the CTL response to a clinically relevant DNA vaccine engineered to combat human papillomavirus-expressing tumors. Inclusion of tumor-unrelated helper epitopes greatly increased CTL priming, effector, and memory T-cell programming. CD4(+) T-cell help optimized the CTL response in all these aspects via CD27/CD70 costimulation. Notably, administration of an agonistic CD27 antibody could largely replace helper epitopes in promoting primary and memory CTL responses, acting directly on CD8(+) T cells. CD27 agonism improved efficacy of the vaccine without helper epitopes, more so than combined PD-1 and CTLA-4 blockade. Combining CD27 agonism with CTLA-4 blockade improved vaccine-induced CTL priming and tumor infiltration, but only combination with PD-1 blockade was effective at eradicating tumors, thereby fully recapitulating the effect of CD4(+) T-cell help on vaccine efficacy. PD-1 blockade alone did not affect CTL priming or tumor infiltration, so these results implied that it cooperated with CD4(+) T-cell help by alleviating immune suppression against CTL in the tumor. Helper epitope inclusion or CD27 agonism did not stimulate regulatory T cells, and vaccine efficacy was also improved by CD27 agonism in the presence of CD4(+) T-cell help. Our findings provide a preclinical rationale to apply CD27 agonist antibodies, either alone or combined with PD-1 blockade, to improve the therapeutic efficacy of cancer vaccines and immunotherapy generally. Cancer Res; 76(10); 2921-31. (c)2016 AACR.

Ngiow, S. F., et al. (2016). “Agonistic CD40 mAb-Driven IL12 Reverses Resistance to Anti-PD1 in a T-cell-Rich Tumor.” Cancer Res 76(21): 6266-6277. PubMed

The durability and efficacy of anti-human PD1 monoclonal antibodies (PD1 mAb) vary across different malignancies. Although an absence of tumor-infiltrating cytotoxic T lymphocytes has been identified as a cause for resistance to PD1 mAb, the presence of intratumor exhausted PD1(hi) T cells also contributes to insensitivity to this immune checkpoint therapy. In this study, we used mouse tumor models of PD1 mAb resistance that harbored PD1(hi) T cells and flow cytometry analysis of tumor-infiltrating leukocytes immediately post-therapy as a screening platform to identify agents that could resensitize T cells to PD1 blockade. We showed that an agonistic anti-CD40 mAb converted PD1(hi) T cells into PD1(lo) T cells, reversing phenotypic T-cell exhaustion and allowing the anti-PD1 refractory tumors to respond to anti-PD1 therapy. PD1 downmodulation by anti-CD40 mAb relied upon IL12 but not IL23, CD80/CD86/CD28, or CD70/CD27. Consistent with a role for regulatory T cells (Treg) in promoting T-cell exhaustion, we also showed that intratumor Treg presented with a less activated and attenuated suppressive phenotype, marked by reductions in CTLA4 and PD1. Similar to anti-CD40 mAb, anti-CTLA4 mAb also lowered intratumor T-cell PD1 expression. Our study provides a proof-of-principle framework to systematically identify immune conditioning agents able to convert PD1(hi) T cells to PD1(lo) T cells, with clinical implications in the management of anti-PD1 refractory patients. Cancer Res; 76(21); 6266-77. (c)2016 AACR.

Roberts, D. J., et al. (2010). “Control of established melanoma by CD27 stimulation is associated with enhanced effector function and persistence, and reduced PD-1 expression of tumor infiltrating CD8(+) T cells.” J Immunother 33(8): 769-779. PubMed

The immune response to the tumor can be enhanced by targeting costimulatory molecules on T cells. As the CD70-CD27 costimulatory axis plays an important role in the activation, survival, and differentiation of lymphocytes, we have examined the efficacy of agonistic anti-CD27 antibodies as monotherapies for established melanoma in a murine model. We show that this approach leads to a substantial reduction in the outgrowth of both experimental lung metastases and subcutaneous tumors. Anti-CD27 treatment supports the maintenance of tumor-specific CD8(+) T cells within the tumor, reduces the frequency of FoxP3-expressing CD4(+) T cells within tumors, and potentiates the ability of NK1.1(+) and CD8(+) tumor infiltrating cells to secrete IFNgamma upon coculture with tumor cells. The enhanced effector function correlated with lower levels of PD-1 expression on CD8(+) T cells from anti-CD27-treated mice. Despite the modulating effect of anti-CD27 on multiple cell types, only CD8(+) T cells were absolutely required for tumor control. The CD4(+) T cells were dispensable, whereas NK1.1(+) cells were needed during early stages of tumor growth but not for the effectiveness of anti-CD27. Thus, CD27-mediated costimulation provides a potent boost to multiple aspects of the endogenous responses to tumor, and may be exploited to enhance tumor immunity.

Sakanishi, T. and H. Yagita (2010). “Anti-tumor effects of depleting and non-depleting anti-CD27 monoclonal antibodies in immune-competent mice.” Biochem Biophys Res Commun 393(4): 829-835. PubMed

CD27 plays an important role in T-cell co-stimulation and is also expressed on lymphomas. In the present study, we generated novel depleting and non-depleting monoclonal antibodies (mAbs) against mouse CD27 and characterized their co-stimulatory activity in vitro and anti-tumor effects in immune-competent mice bearing syngeneic T-cell lymphoma (EG7) expressing or lacking CD27. A profound anti-tumor effect was observed with a non-depleting mAb (RM27-3E5), but not with a depleting mAb (RM27-3C1), against either EG7/CD27(+) or EG7/CD27(-) tumors, which was associated with the induction of EG7-specific cytotoxic T lymphocytes (CTLs). Consistently, the anti-tumor effect of RM27-3E5 was abolished in T cell-deficient nude mice. These results indicate that a non-depleting agonistic mAb against CD27 is promising for cancer therapy by co-stimulating tumor-specific CTL induction.

Sumi, T., et al. (2008). “CD27 and CD70 do not play a critical role in the development of experimental allergic conjunctivitis in mice.” Immunol Lett 119(1-2): 91-96. PubMed

CD27, which belongs to the TNF receptor family, is a costimulatory molecule that participates in T-cell activation. Unlike costimulatory molecules such as OX40 and 4-1BB, little is known about the role CD27 plays a role in the development of experimental diseases. We asked whether CD27 and its ligand CD70 participate in the development of experimental allergic conjunctivitis (EC) in BALB/c mice, which is generated by immunization with ragweed (RW) in alum and challenged 10 days later with RW in eye drops. The roles of CD27 and CD70 were tested by intraperitoneally injecting the mice with anti-CD27, anti-CD70 or a control Ab during the induction or effector phase. Twenty-four hours after challenge, the conjunctivas, blood and spleens were harvested for histological analysis, measuring Ig levels and cytokine analysis, respectively. Regardless of when the mice were treated, anti-CD27 or anti-CD70 Ab treatment did not significantly affect the severity of EC as evaluated by conjunctival eosinophil numbers. However, anti-CD27 or anti-CD70 Ab treatment during the induction phase did significantly modulate systemic humoral and cellular immune responses. In vitro treatment of RW-primed splenocytes with anti-CD27 or anti-CD70 Ab did not affect the EC-inducing capability of the splenocytes. Taken together, CD27 and CD70 do not play a critical role in the development of EC.