Modifying immune responses to adeno-associated virus vectors by capsid engineering

De novo immune responses are considered major challenges in gene therapy. With the aim to lower innate immune responses directly in cells targeted by adeno-associated virus (AAV) vectors, we equipped the vector capsid with a peptide known to interfere with Toll-like receptor signaling. Specifically, we genetically inserted in each of the 60 AAV2 capsid subunits the myeloid differentiation primary response 88 (MyD88)-derived peptide RDVLPGT, known to block MyD88 dimerization. Inserting the peptide neither interfered with capsid assembly nor with vector production yield. The novel capsid variant, AAV2.MB453, showed superior transduction efficiency compared to AAV2 in human monocyte-derived dendritic cells and in primary human hepatocyte cultures. In line with our hypothesis, AAV2.MB453 and AAV2 differed regarding innate immune response activation in primary human cells, particularly for type I interferons. Furthermore, mice treated with AAV2.MB453 showed significantly reduced CD8+ T cell responses against the transgene product for different administration routes and against the capsid following intramuscular administration. Moreover, humoral responses against the capsid were mitigated as indicated by delayed IgG2a antibody formation and an increased NAb50. To conclude, insertion of the MyD88-derived peptide into the AAV2 capsid improved early steps of host-vector interaction and reduced innate and adaptive immune responses.

Capsid-modified adeno-associated virus vectors as novel vaccine platform for cancer immunotherapy

Immunotherapy has significantly improved treatment outcomes in various cancer entities. To enhance immunogenicity and efficacy, and to further broaden its applicability, co-administration of anti-tumor vaccines is considered as a promising strategy. Here, we introduce adeno-associated virus (AAV) vectors, widely used for in vivo gene therapy, as a potent cancer vaccine platform. Our AAV vector-based vaccine combines antigen display on the capsid surface with a vector-mediated antigen overexpression targeting different components of the immune system in a unique chronological order by a single intramuscular application. Thereby, both profound and long-lasting antigen-specific T and B cell immune responses were induced. Moreover, mice receiving the vaccine were protected against tumor growth, demonstrating its efficacy in two tumor models, including the low immunogenic and aggressive B16/F10-Ova melanoma model. Remarkably, this approach was even effective in conditions of a late tumor challenge, i.e., 80 days post-vaccination, between 88% (B16/F10-Ova melanoma) and 100% (EG7 thymoma) of mice remained tumor free. Thus, decorating AAV vector particles with antigens by capsid engineering represents a potent vaccine concept for applications in cancer immunotherapy. Its modular and versatile "plug-and-play" framework enables the use of tumor antigens of choice and the easy implementation of additional modifications to enhance immunogenicity further.

Towards Clinical Implementation of Adeno-Associated Virus (AAV) Vectors for Cancer Gene Therapy: Current Status and Future Perspectives

Adeno-associated virus (AAV) vectors have gained tremendous attention as in vivo delivery systems in gene therapy for inherited monogenetic diseases. First market approvals, excellent safety data, availability of large-scale production protocols, and the possibility to tailor the vector towards optimized and cell-type specific gene transfer offers to move from (ultra) rare to common diseases. Cancer, a major health burden for which novel therapeutic options are urgently needed, represents such a target. We here provide an up-to-date overview of the strategies which are currently developed for the use of AAV vectors in cancer gene therapy and discuss the perspectives for the future translation of these pre-clinical approaches into the clinic.

Preclinical Evaluation of a Novel Lentiviral Vector Driving Lineage-Specific BCL11A Knockdown for Sickle Cell Gene Therapy

In this work we provide preclinical data to support initiation of a first-in-human trial for sickle cell disease (SCD) using an approach that relies on reversal of the developmental fetal-to-adult hemoglobin switch. Erythroid-specific knockdown of BCL11A via a lentiviral-encoded microRNA-adapted short hairpin RNA (shRNAmiR) leads to reactivation of the gamma-globin gene while simultaneously reducing expression of the pathogenic adult sickle β-globin. We generated a refined lentiviral vector (LVV) BCH-BB694 that was developed to overcome poor vector titers observed in the manufacturing scale-up of the original research-grade LVV. Healthy or sickle cell donor CD34+ cells transduced with Good Manufacturing Practices (GMP)-grade BCH-BB694 LVV achieved high vector copy numbers (VCNs) >5 and gene marking of >80%, resulting in a 3- to 5-fold induction of fetal hemoglobin (HbF) compared with mock-transduced cells without affecting growth, differentiation, and engraftment of gene-modified cells in vitro or in vivo. In vitro immortalization assays, which are designed to measure vector-mediated genotoxicity, showed no increased immortalization compared with mock-transduced cells. Together these data demonstrate that BCH-BB694 LVV is non-toxic and efficacious in preclinical studies, and can be generated at a clinically relevant scale in a GMP setting at high titer to support clinical testing for the treatment of SCD.

Growth differentiation factor 11 attenuates liver fibrosis via expansion of liver progenitor cells

OBJECTIVE

Liver fibrosis and cirrhosis resulting from chronic liver injury represent a major healthcare burden worldwide. Growth differentiation factor (GDF) 11 has been recently investigated for its role in rejuvenation of ageing organs, but its role in chronic liver diseases has remained unknown. Here, we investigated the expression and function of GDF11 in liver fibrosis, a common feature of most chronic liver diseases.

DESIGN

We analysed the expression of GDF11 in patients with liver fibrosis, in a mouse model of liver fibrosis and in hepatic stellate cells (HSCs) as well as in other liver cell types. The functional relevance of GDF11 in toxin-induced and cholestasis-induced mouse models of liver fibrosis was examined by in vivo modulation of Gdf11 expression using adeno-associated virus (AAV) vectors. The effect of GDF11 on leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5)+ liver progenitor cells was studied in mouse and human liver organoid culture. Furthermore, in vivo depletion of LGR5+ cells was induced by injecting AAV vectors expressing diptheria toxin A under the transcriptional control of Lgr5 promoter.

RESULTS

We showed that the expression of GDF11 is upregulated in patients with liver fibrosis and in experimentally induced murine liver fibrosis models. Furthermore, we found that therapeutic application of GDF11 mounts a protective response against fibrosis by increasing the number of LGR5+ progenitor cells in the liver.

CONCLUSION

Collectively, our findings uncover a protective role of GDF11 during liver fibrosis and suggest a potential application of GDF11 for the treatment of chronic liver disease.

DROSHA Knockout Leads to Enhancement of Viral Titers for Vectors Encoding miRNA-Adapted shRNAs

RNAi-based gene therapy using miRNA-adapted short hairpin RNAs (shRNA^miR) is a powerful approach to modulate gene expression. However, we have observed low viral titers with shRNA^miR-containing recombinant vectors and hypothesized that this could be due to cleavage of viral genomic RNA by the endogenous microprocessor complex during virus assembly. To test this hypothesis, we targeted DROSHA, the core component of the microprocessor complex, and successfully generated monoallelic and biallelic DROSHA knockout (KO) HEK293T cells for vector production. DROSHA KO was verified by polymerase chain reaction (PCR) and western blot analysis. We produced lentiviral vectors containing Venus with or without shRNA hairpins and generated virus supernatants using DROSHA KO packaging cells. We observed an increase in the fluorescence intensity of hairpin-containing Venus transcripts in DROSHA KO producer cells consistent with reduced microprocessor cleavage of encoded mRNA transcripts, and recovery in the viral titer of hairpin-containing vectors compared with non-hairpin-containing constructs. We confirmed the absence of significant shRNA^miR processing by northern blot analysis and showed that this correlated with an increase in the amount of full-length vector genomic RNA. These findings may have important implications in future production of viral shRNA^miR-containing vectors for RNAi-based therapy.

Role of miR-203 in estrogen receptor-mediated signaling in the rat uterus and endometrial carcinoma

The role of microRNAs (miRNA) in estrogen receptor (ER) signaling in the uterus and in endometrial cancer is not well understood. We therefore analyzed miRNA expression in uterine samples from a standard 3-day uterotrophic assay using young female adult rats to identify E2-regulated miRNAs. Microarray analysis identified 47 E2 down-regulated miRNAs including miR-30a, and 25 E2up-regulated miRNAs including miR-672, miR-203, and miR-146b. The strongly E2-upregulated miR-203 was selected for further analysis. miR-203 was deleted in the rat endometrial adenocarcinoma cell line, RUCA-I, using CRISPR/CAS9. Five clones devoid of miR-203 expression were generated. Proliferation was reduced and G2-arrest was observed in all miR-203 deficient RUCA-I clones. Transfection with a miR-203-3p mimic partially rescues this effect. Comparison of mRNA expression in three miR-203 knockout clones to wild type RUCA-I cells reveals 566 miR-203-upregulated and 592 miR-203-downregulated genes. 43 of the genes that are upregulated by miR-203 knockout in vitro are downregulated in the uterus by E2. Of these Acer2, Zbtb20, Ptn, Rcbtb2, Mum1l1, Hmgn3, and Nfat5 possess one or more seed sequence matches in their 3'-UTR that are predicted to be targets of miR-203. These data demonstrate the importance of E2 regulated miRNAs in general, and miR-203 in particular, for E2 regulated gene expression and physiological processes including proliferation and cell migration, in the uterus as well as in the etiology of endometrial carcinomas.

Nutrition support of the pediatric patient with AIDS

Maintaining optimal nutrition in the pediatric patient with Acquired Immune Deficiency Syndrome (AIDS) is challenging, but it may be one of the most effective therapies. Patients experience numerous complications that compromise nutritional status. Infection, fever, diarrhea, feeding problems, and decreased intake all contribute to malnutrition, which in turn predisposes the patient even more to infection and malabsorption. Nutrition assessment should be done routinely so that new problems may be identified and treated. High-calorie, high-protein feedings, vitamin supplementation, and, when necessary, gavage feedings or parenteral nutrition are recommended to improve nutritional status and prevent further deficits. Maintaining optimal nutrition in the pediatric patient with Acquired Immune Deficiency Syndrome (AIDS) poses a significant challenge to the health care team. Patients may experience numerous complications that compromise nutritional status. The patient is at high risk for opportunistic infections, especially of the lungs, central nervous system, gastrointestinal (GI) tract, and skin. Such infections are common causes of morbidity and mortality. Impaired nutritional status may further impair the patient's immunocompetence. A study by Kotler and Gaety demonstrated severe progressive malnutrition in adult AIDS patients, with the lowest measures of lean body mass occurring in those patients close to death at the time of the study. While no studies of children with AIDS have been done to date, we have subjectively observed feeding problems, weight loss, and malnutrition in most of the patients we have seen.