Methods for determination of risk, previous history and/or presence of a betaretrovirus infection in a subject are described herein. Said methods may comprise incubating a biological sample from the subject, the biological sample comprising immune effector-producing cells, with one or more betaretrovirus-specific epitopes, the betaretrovirus-specific epitopes comprising at least 7 contiguous amino acids according to any one of SEQ ID Nos. 1-36, and measuring the production of immune effectors by the immune effector-producing cells, wherein production of the immune effectors by the immune effector-producing cells determines risk and/or presence of betaretrovirus infection in the subject. Isolated peptides and kits for carrying out the methods are also described.

Provided herein are delivery particle systems (XDP) useful for the delivery of payloads of any type. In some embodiments, a XDP particle system with tropism for target cells of interest is used to deliver CRISPR/Cas polypeptides (e.g., CasX proteins) and guide nucleic acids (gNA), for the modification of nucleic acids in target cells. Also provided are methods of making and using such XDP to modify the nucleic acids in such cells.

Methods for determination of risk, previous history and/or presence of a betaretrovirus infection in a subject are described herein. Said methods may comprise incubating a biological sample from the subject, the biological sample comprising immune effector-producing cells, with one or more betaretrovirus-specific epitopes, the betaretrovirus-specific epitopes comprising at least 7 contiguous amino acids according to any one of SEQ ID Nos. 1-36, and measuring the production of immune effectors by the immune effector-producing cells, wherein production of the immune effectors by the immune effector-producing cells determines risk and/or presence of betaretrovirus infection in the subject. Isolated peptides and kits for carrying out the methods are also described.

Disclosed are methods of treating a patient exposed to MTV. Also disclosed is a purified cDNA encoding an MTV transition protein peptide chain. Also disclosed is a vaccine containing an MTV transition protein. A further version of the invention is a vaccine comprising MTV polypeptides coupled to a carrier protein. MTV may be treated by providing an MTV vaccine with an MTV transition protein; and, administering said vaccine. In further instances, the MTV vaccine is administered with an antiretroviral medication.

Methods for determination of risk, previous history and/or presence of a betaretrovirus infection in a subject are described herein. Said methods may comprise incubating a biological sample from the subject, the biological sample comprising immune effector-producing cells, with one or more betaretrovirus-specific epitopes, the betaretrovirus-specific epitopes comprising at least 7 contiguous amino acids according to any one of SEQ ID Nos. 1-36, and measuring the production of immune effectors by the immune effector-producing cells, wherein production of the immune effectors by the immune effector-producing cells determines risk and/or presence of betaretrovirus infection in the subject. Isolated peptides and kits for carrying out the methods are also described.

A method using an endogenous retrovirus (ERV) as a biomarker for detecting a degree of aging of an object or a cell, tissue or organ or isolated cell thereof. A method using an ERV as a target for treating, preventing or delaying aging of the subject or a cell, tissue or organ or isolated cell thereof.

Provided herein are delivery particle systems (XDP) useful for the delivery of payloads of any type. In some embodiments, a XDP particle system with tropism for target cells of interest is used to deliver CRISPR/Cas polypeptides (e.g., CasX proteins) and guide nucleic acids (gNA), for the modification of nucleic acids in target cells. Also provided are methods of making and using such XDP to modify the nucleic acids in such cells.

Disclosed are methods of treating a patient exposed to MTV. Also disclosed is a purified cDNA encoding an MTV transition protein peptide chain. Also disclosed is a vaccine containing an MTV transition protein. A further version of the invention is a vaccine comprising MTV polypeptides coupled to a carrier protein. MTV may be treated by providing an MTV vaccine with an MTV transition protein; and, administering said vaccine. In further instances, the MTV vaccine is administered with an antiretroviral medication.

In one aspect, the invention provides a transgenic non-human animal model having germ cells and somatic cells containing an endogenous MMTV-SV40-Spy1A gene sequence introduced into said animal model or an ancestor of said animal model at an embryonic stage, wherein said gene sequence comprises a mouse mammary tumor virus gene (MMTV), a functionally disrupted SV40 gene (SV40) and a human Spy1A gene. In another aspect, the present invention provides a transgenic non-human animal model whose germ cells and somatic cells contain an endogenous Spy1A-pTRE-Tight gene sequence introduced into said animal model or an ancestor of said animal model at an embryonic stage. Preferably, the Spy1A-pTRE-Tight animal model expresses the Spy1A gene and develop cancer, preferably breast cancer, when administered with tetracycline, preferably doxycycline.

Methods of treating amyotrophic lateral sclerosis (ALS) or preventing the progression of ALS. Compounds useful in these therapeutic methods include anti-retroviral compounds and RNA interference (RNAi) constructs.