Provided are compositions comprising vectors for the co-expression of a modified GlcNAc-1-Phosphotransferase gene and a lysosomal enzyme. The gene encoding the lysosomal enzyme is operably linked to a first promoter and the gene encoding the GlcNAc-1-Phosphotransferase is operably linked to a second promoter. Also provided herein are methods of treating a lysosomal storage disorder comprising administering to a subject the compositions of the disclosure.

The invention relates to an expression vector operable in vertebrate liver cells, having an expression cassette with a bidirectional promoter, driving operably linked protein expression by a first side and a second side, a first expression unit, under the control of the first side of the promoter, said first expression unit comprising a positive selectable marker gene, a second expression unit, under the control of the second side of the promoter, comprising an ORFeus reporter element wherein said ORFeus reporter element comprises a gene encoding L1-ORF land a retrotransposition reporter gene encoding a retrotransposition reporter protein, wherein preferably the retrotransposition reporter protein from said retrotransposition reporter gene is provided only when the ORFeus reporter element is subject to retrotransposition. The invention also relates to transgenic animals which are useful to detect somatic retrotransposition.

The invention provides bidirectional expression vectors comprising Chinese hamster ovary elongation factor 1- (CHEF1) transcriptional regulatory DNA elements, a gene of interest (GOI), a minimal cytomegalovirus (minCMV) and a selectable marker (SM) and/or a human adenovirus tripartite leader (AdTPL) sequence. The invention also provides method for increasing heterologous protein expression in a host cell comprising culturing the host cell the bidirectional expression vector(s).

The present invention relates to modular systems for vaccination against infectious agents that involves the delivery of, e.g., exosome-loaded, antigen-encoding mRNAs to and into cells and tissues of the immunized subject. The present invention also relates to compositions and methods for the design, preparation, manufacture, formulation, and/or use of vaccines, e.g., nucleic acid vaccines, loaded into extracellular vesicles, e.g., exosomes loaded with synthetic mRNAs encoding multiple surface and cytoplasmic antigens of interest, e.g., antigenic polypeptides derived from an infectious virus, e.g., SARS-CoV-2, designed to elicit strong humoral and cellular immune responses due to the simultaneous expression of antigens in their native state and as exosome-associated antigens.

Aspects of the disclosure relate to bicistronic AAV nucleic acid constructs comprising a transgene encoding hexosaminidase A (HEXA) and hexosaminidase (HEXB) proteins. In some embodiments, the disclosure provides methods for treating or preventing lysosomal storage disorders, such as Tay-Sachs disease and Sandhoff disease, using bicistronic nucleic acid constructs described by the disclosure.