Multiparametric analyses of human PBMCs loaded ex vivo with a candidate idiotype vaccine for HCV-related lymphoproliferative disorders

Immunological effects of adjuvants in subsets of antigen presenting cells of cancer patients undergoing chemotherapy

Background

We have previously shown that HCC patients and healthy subjects are equally responsive to a RNAdjuvant^®, a novel TLR-7/8/RIG-I agonist based on noncoding RNA developed by CureVac, by an ex vivo evaluation. However, the immunological effect of adjuvants on immune cells from cancer patients undergoing chemotherapy remains to be demonstrated. Different adjuvants currently used in cancer vaccine clinical trials were evaluated in the present study on immune cells from cancer patients before and after chemotherapy in an ex vivo setting.

Methods

PBMCs were obtained from 4 healthy volunteers and 23 patients affected by either colon (OMA) or lung cancer (OT). The effect of CpG, Poly I:C, Imiquimod and RNA-based adjuvant (RNAdjuvant^®) was assessed using a multiparametric approach to analyze network dynamics of early immune responses. Evaluation of CD80, CD86 and HLA-DR expression as well as the downstream effect on CD4⁺ T cell phenotyping was performed by flow cytometry; cytokine and chemokine production was evaluated by Bio-Plex ProTM.

Results

Treatment with RNAdjuvant^® induced the strongest response in cancer patients in terms of activation of innate and adoptive immunity. Indeed, CD80, CD86 and HLA-DR expression was found upregulated in circulating dendritic cells, which promoted a CD4⁺ T cell differentiation towards an effector phenotype. RNAdjuvant^® was the only one to induce most of the cytokines/chemokines tested with a pronounced Th1 cytokine pattern. According to the different parameters evaluated in the study, no clear cut difference in immune response to adjuvants was observed between healthy subjects and cancer patients. Moreover, in the latter group, the chemotherapy treatment did not consistently correlate to a significant altered response in the different parameters.

Conclusions

The present study is the first analysis of immunological effects induced by adjuvants in cancer patients who undergo chemotherapy, who are enrolled in the currently ongoing cancer vaccine clinical trials. The results show that the RNAdjuvant^® is a potent and Th1 driving adjuvant, compared to those tested in the present study. Most importantly, it is demonstrated that chemotherapy does not significantly impair the immune system, implying that cancer patients are likely to respond to a cancer vaccine even after a chemotherapy treatment.

Immunological effects of a novel RNA-based adjuvant in liver cancer patients

Evaluation of biological effects of adjuvants on immune cells has been assessed in a limited number of studies. Moreover, no data are available on samples derived from cancer patients who may have a severe immune impairment. The effects of a novel RNA-based adjuvant (RNAdjuvant® developed by CureVac) were assessed in an ex vivo setting on PBMCs obtained from 8 healthy volunteers and 17 HCC patients, using a multiparametric approach to analyze network dynamics of early immune responses. Evaluation of CD80, CD86 and HLA-DR expression, cytokine production as well as gene expression was performed. Moreover, the downstream effect on CD4+ T cell phenotyping was evaluated. Treatment with RNAdjuvant® showed comparable effects on PBMCs of both HCC and healthy subjects. In particular, CD80, CD86 and HLA-DR expression was found up-regulated in circulating dendritic cells, which promoted a CD4+ T cell differentiation toward an effector phenotype. A mixed Th1/Th2 cytokine pattern was induced, although a more predominant production of TNFα and IFNγ was observed in HCC patients versus healthy controls. The cytokine profile was further confirmed by gene transcriptional analysis, which showed up-regulation of several genes involved in innate and adaptive immune-related pathways. The present study is the first demonstration that HCC patients and healthy subjects are equally responsive to an adjuvant. This may suggest that the same vaccine formulation including the RNAdjuvant® might have similar potency in healthy subjects and cancer patients.

Systems vaccinology for cancer vaccine development

Results of therapeutic vaccines for established chronic infections or cancers are still unsatisfactory. The only therapeutic cancer vaccine approved for clinical use is the sipuleucel-T, for the treatment of metastatic prostate cancer, which induces a limited 4-month improvement in the overall survival of vaccinated patients compared to controls. This represents a remarkable advancement in the cancer immunotherapy field, although the clinical outcome of cancer vaccines needs to be substantially improved. To this aim, a multipronged strategy is required, including the evaluation of mechanisms underlying the effective elicitation of immune responses by cancer vaccines. The recent development of new technologies and computational tools allows the comprehensive and quantitative analysis of the interactions between all of the components of innate and adaptive immunity over time. Here we review the potentiality of systems biology in providing novel insights in the mechanisms of action of vaccines to improve their design and effectiveness.

Prediction of individual immune responsiveness to a candidate vaccine by a systems vaccinology approach

Background

We have previously shown that a candidate idiotype vaccine, based on the IGKV3-20 light chain protein, is able to induce activation of circulating antigen presenting cells (APCs) in both HCV-positive and HCV-negative subjects, with production of Th2-type cytokines. In addition, such a candidate idiotype vaccine induces an early gene expression pattern, characterized by the strong induction of an innate immune response, and a late pattern, characterized by a prevalent B cell response. Nonetheless, some HCV-positive individuals showed a complete lack of maturation of circulating APCs with low levels of cytokine production, strongly suggesting the possible identification of selective impairments in immune response in individual subjects.

Method

Peripheral blood mononuclear cells (PBMCs) were stimulated ex vivo with IGKV3-20 for 24 h and 6 days. Analysis of the global gene expression profile as well as the cytokine pattern was performed for individual subjects.

Results

The gene expression profile showed a strong agreement with the cytokine pattern. Indeed, the expression pattern of immune-related genes is highly predictive of the individual immunological phenotype.

Conclusion

The overall results represent a proof of concept, indicating the efficacy of such an ex vivo screening platform for predicting individual’s responsiveness to an antigen as well as guiding optimization of vaccine design. Larger cohort study will be needed to validate results observed in the study.