Breaking Entry-and Species Barriers: LentiBOOST® Plus Polybrene Enhances Transduction Efficacy of Dendritic Cells and Monocytes by Adenovirus 5

Development of novel HPV therapeutic vaccine constructs based on engineered exosomes and tumor cell lysates

AIMS

Human papillomavirus (HPV) infections are highly prevalent globally. While preventive HPV vaccines exist, therapeutic vaccines are needed to treat existing HPV lesions and malignancies. This study evaluated the immunostimulatory and anti-tumor effects of three therapeutic vaccine candidates based on the recombinant protein, tumor cell lysate (TCL), and engineered exosome (Exo) harboring the heat shock protein 27 (Hsp27)-E7 fusion construct in mouse model.

MAIN METHODS

At first, the recombinant Hsp27-E7 protein was generated in E. coli expression system. Then, tumor cell lysates-based and engineered exosomes-based vaccine constructs harboring green fluorescent protein (GFP) and Hsp27-E7 were produced using lentiviral system. Finally, their immunological and antitumor effects were investigated in both prophylactic and therapeutic experiments.

KEY FINDINGS

Our data showed that the recombinant Hsp27-E7 protein, TCL-Hsp27-E7 and Exo-Hsp27-E7 regimens can induce the highest level of IFN-γ, TNF-α and Granzyme B, respectively. The percentage of tumor-free mice was identical for three vaccine strategies (survival rate: 75 %) in both prophylactic and therapeutic experiments. Generally, the TCL-Hsp27-E7, Exo-Hsp27-E7 and recombinant Hsp27-E7 protein regimens induced effective immune responses toward Th1 and CTL activity, and subsequently antitumor effects in mouse model.

SIGNIFICANCE

Regarding to higher Granzyme B secretion, lower tumor growth and more safety, the Exo-Hsp27-E7 regimen can be considered as the most promising HPV vaccination strategy.

Identification of a small molecule for enhancing lentiviral transduction of T cells

Genetic modification of cells using viral vectors has shown huge therapeutic benefit in multiple diseases. However, inefficient transduction contributes to the high cost of these therapies. Several transduction-enhancing small molecules have previously been identified; however, some may be toxic to the cells or patient, otherwise alter cellular characteristics, or further increase manufacturing complexity. In this study, we aimed to identify molecules capable of enhancing lentiviral transduction of T cells from available small-molecule libraries. We conducted a high-throughput flow-cytometry-based screen of 27,892 compounds, which subsequently was narrowed down to six transduction-enhancing small molecules for further testing with two therapeutic lentiviral vectors used to manufacture GSK's clinical T cell therapy products. We demonstrate enhanced transduction without a negative impact on other product attributes. Furthermore, we present results of transcriptomic analysis, suggesting alteration of ribosome biogenesis, resulting in reduced interferon response, as a potential mechanism of action for the transduction-enhancing activity of the lead compound. Finally, we demonstrate the ability of the lead transduction enhancer to produce a comparable T cell product using a 3-fold reduction in vector volume in our clinical manufacturing process, resulting in a predicted 15% reduction in the overall cost of goods.

Comparative analysis of the impact of 40 adenovirus types on dendritic cell activation and CD8+ T cell proliferation capacity for the identification of favorable immunization vector candidates

For the development of new adenovirus (AdV)-based vectors, it is important to understand differences in immunogenicity. In a side-by-side in vitro analysis, we evaluated the effect of 40 AdV types covering human AdV (HAdV) species A through G on the expression of 11 activation markers and the secretion of 12 cytokines by AdV-transduced dendritic cells, and the effect on CD8+ T cell proliferation capacity. We found that the expression of activation markers and cytokines differed widely between the different HAdV types, and many types were able to significantly impair the proliferation capacity of CD8+ T cells. Univariate and multivariate regression analyses suggested an important role of type I interferons in mediating this suppression of CD8+ T cells, which we confirmed experimentally in a proliferation assay using a type I interferon receptor blocking antibody. Using Bayesian statistics, we calculated a prediction model that suggests HAdV types HAdV-C1, -D8, -B7, -F41, -D33, -C2, -A31, -B3 and -D65 as the most favorable candidates for vaccine vector development.

In vivo tracking of adenoviral-transduced iron oxide-labeled bone marrow-derived dendritic cells using magnetic particle imaging

BACKGROUND

Despite widespread study of dendritic cell (DC)-based cancer immunotherapies, the in vivo postinjection fate of DC remains largely unknown. Due in part to a lack of quantifiable imaging modalities, this is troubling as the amount of DC migration to secondary lymphoid organs correlates with therapeutic efficacy. Magnetic particle imaging (MPI) has emerged as a suitable modality to quantify in vivo migration of superparamagnetic iron oxide (SPIO)-labeled DC. Herein, we describe a popliteal lymph node (pLN)-focused MPI scan to quantify DC in vivo migration accurately and consistently.

METHODS

Adenovirus (Ad)-transduced SPIO+ (Ad SPIO+) and SPIO+ C57BL/6 bone marrow-derived DC were generated and assessed for viability and phenotype, then fluorescently labeled and injected into mouse hind footpads (n = 6). Two days later, in vivo DC migration was quantified using whole animal, pLN-focused, and ex vivo pLN MPI scans.

RESULTS

No significant differences in viability, phenotype and in vivo pLN migration were noted for Ad SPIO+ and SPIO+ DC. Day 2 pLN-focused MPI quantified DC migration in all instances while whole animal MPI only quantified pLN migration in 75% of cases. Ex vivo MPI and fluorescence microscopy confirmed that pLN MPI signal was due to originally injected Ad SPIO+ and SPIO+ DC.

CONCLUSION

We overcame a reported limitation of MPI by using a pLN-focused MPI scan to quantify pLN-migrated Ad SPIO+ and SPIO+ DC in 100% of cases and detected as few as 1000 DC (4.4 ng Fe) in vivo. MPI is a suitable preclinical imaging modality to assess DC-based cancer immunotherapeutic efficacy.

RELEVANCE STATEMENT

Tracking the in vivo fate of DC using noninvasive quantifiable magnetic particle imaging can potentially serve as a surrogate marker of therapeutic effectiveness.

KEY POINTS

• Adenoviral-transduced and iron oxide-labeled dendritic cells are in vivo migration competent. • Magnetic particle imaging is a suitable modality to quantify in vivo dendritic cell migration. • Magnetic particle imaging focused field of view overcomes dynamic range limitation.

The performance and perspectives of dendritic cell vaccines modified by immune checkpoint inhibitors or stimulants

Therapeutic dendritic cell (DC) vaccines stimulate the elimination of tumor cells by the immune system. However, while antigen-specific T cell responses induced by DC vaccines are commonly observed, the clinical response rate is relatively poor, necessitating vaccine optimization. There is evidence that the suppression of DC function by immune checkpoints hinders the anti-tumor immune responses mediated by DC vaccines, ultimately leading to the immune escape of the tumor cells. The use of immune checkpoint inhibitors (ICIs) and immune checkpoint activators (ICAs) has extended the immunotherapeutic range. It is known that both inhibitory and stimulatory checkpoint molecules are expressed by most DC subsets and can thus be used to manipulate the effectiveness of DC vaccines. Such manipulation has been investigated using strategies such as chemotherapy, agonistic or antagonistic antibodies, siRNA, shRNA, CRISPR-Cas9, soluble antibodies, lentiviruses, and adenoviruses to maximize the efficacy of DC vaccines. Thus, a deeper understanding of immune checkpoints may assist in the development of improved DC vaccines. Here, we review the actions of various ICIs or ICAs shown by preclinical studies, as well as their potential application in DC vaccines. New therapeutic interventional strategies for blocking and stimulating immune checkpoint molecules in DCs are also described in detail.