Provided herein are genetically modified cells and genetically modified non-human animals (e.g., rodents such as rats and mice) comprising: (i) a homozygous null mutation in Rag2 gene; (ii) a homozygous null mutation in IL2rg gene; (iii) a homozygous null mutation in the non-human animal FMS-like tyrosine kinase 3 (Flt3) gene, and (iv) a Flt3 ligand (Flt31) gene that comprises a non-human animal portion and a human portion operably linked to a Flt31 promoter, and optionally expressing one or more human or humanized polypeptides. Methods and compositions of making and using such genetically modified cells and non-human animals are also provided.

The current invention describes a laboratory animal model for dirofilarial nematodes wherein said laboratory animal is fed a dietary admixture of laboratory feed containing an immunosuppressing agent, for example, a glucocorticoid. The invention also describes the use of the laboratory animal model for screening endoparasiticides for the treatment and/or prevention of filarial nematode infections in animals.

Genetically modified rodents such as mice and rats, and methods and compositions for making and using the same, are provided. The rodents comprise a humanization of at least one endogenous rodent Tmprss gene, such as an endogenous rodent Tmprss2, Tmprss4, or Tmprss11d gene.

Genetically modified mice comprising a nucleic acid sequence encoding a human M-CSF protein are provided. Also provided are genetically modified mice comprising a nucleic acid sequence encoding a human M-CSF protein that have been engrafted with human cells such as human hematopoietic cells, and methods for making such engrafted mice. These mice find use in a number of applications, such as in modeling human immune disease and pathogen infection; in in vivo screens for agents that modulate hematopoietic cell development and/or activity, e.g. in a healthy or a diseased state; in in vivo screens for agents that are toxic to hematopoietic cells; in in vivo screens for agents that prevent against, mitigate, or reverse the toxic effects of toxic agents on hematopoietic cells; in in vivo screens of human hematopoietic cells from an individual to predict the responsiveness of an individual to a disease therapy, etc.

Perforin-2 (P2) is expressed by fibroblasts, microglia and macrophages and was found to be responsible for killing bacteria, for example, Mycobacteria smegmatis, M. avium, Salmonellae, MRSA (drug resistant Stapholococci), E. coli. Compounds identified by screening assays are selected based on the effects of these compounds on P2. Use of these compounds in the treatment of infectious diseases, in particular, bacteria and antibiotic-resistant bacteria is also provided.

In one aspect, the invention relates to a method of loading exosomes with oligonucleotide cargo, by incubating an oligonucleotide comprising one or more hydrophobic modifications with a population of exosomes for a period of time sufficient to allow loading of the exosomes with the oligonucleotide. Exosomes loaded with hydrophobic ally modified oligonucleotide cargo, and uses thereof, are also provided.

A mouse with a humanization of the mIL-3 gene and the mGM-CSF gene, a knockout of a mRAG gene, and a knockout of a mll2rg subunit gene; and optionally a humanization of the TPO gene is described. A RAG/ll2rg KO/hTPO knock-in mouse is described. A mouse engrafted with human hematopoietic stem cells (HSCs) that maintains a human immune cell (HIC) population derived from the HSCs and that is infectable by a human pathogen, e.g., S. typhi or M. tuberculosis is described. A mouse that models a human pathogen infection that is poorly modeled in mice is described, e.g., a mouse that models a human mycobacterial infection, wherein the mouse develops one or more granulomas comprising human immune cells. A mouse that comprises a human hematopoietic malignancy that originates from an early human hematopoietic cells is described, e.g., a myeloid leukemia or a myeloproliferative neoplasia.

Non-human animals, expressing humanized CD3 proteins are provided. Non-human animals, e.g., rodents, genetically modified to comprise in their genome humanized CD3 proteins are also provided. Additionally, provided are methods and compositions of making such non-human animals, as well as methods of using said non-human animals.

Various aspects described herein provide methods of generating alveolar or alveolar/airway organoids from a population of lung cells to differentiate into alveolar or alveolar/airway organoids. Also provided herein are methods and compositions for treating lung disease comprising transplantation of the alveolar or alveolar/airway organoids, or a cell isolated therefrom to a subject.

Non-human animal cells and non-human animals comprising a humanized ACE2 locus and a humanized TMPRSS locus, and methods of using such non-human animal cells and non-human animals are provided. Non-human animal cells or non-human animals comprising a humanized ACE2 locus and a humanized TMPRSS locus express a human ACE2 protein or a chimeric ACE2 protein, fragments of which are from human ACE2; and a human TMPRSS or chimeric TMPRSS protein, fragments of which are from human TMPRSS. Methods are also provided for using such non-human animals comprising a humanized ACE2 locus and a humanized TMPRSS locus to assess in vivo ACE2 activity, e.g., coronavirus infection and/or the treatment or prevention thereof.