A cationic lipid compound, a preparation method and a use thereof, and a delivery system for mRNA are provided. The cationic lipid compound has a structure represented by formula (I):

##STR00001##

In formula (I): X is O or N; n is 2-4; m is 2-4; a is 0 or 1; R.sub.1 is a chain structure comprising a tertiary amine; R.sub.2 is a linear fatty acyl group or a branched chain fatty acyl group; R.sub.3 is a branched chain fatty acyl group. The cationic lipid compound is used for preparing a delivery system for mRNA.

What is described is a method of synthesis of the compound of formula 1A,

##STR00001##

or a salt thereof, wherein R.sub.3 is a linear or branched alkene of 1, 2, 3, 4, 5 or 6 carbons; R.sub.4 and R.sub.5 are the same or different, each a hydrogen, or a linear or branched alkyl of 1, 2, 3, 4, 5 or 6 carbons; and L.sub.3 is a bond or an alkane of 1, 2, 3, 4, 5 or 6 carbons.

What is described is a method of synthesis of the compound of formula 1A,

##STR00001##

or a salt thereof, wherein R.sub.3 is a linear or branched alkene of 1, 2, 3, 4, 5 or 6 carbons; R.sub.4 and R.sub.5 are the same or different, each a hydrogen, or a linear or branched alkyl of 1, 2, 3, 4, 5 or 6 carbons; and L.sub.3 is a bond or an alkane of 1, 2, 3, 4, 5 or 6 carbons.

Described herein are compounds and compositions for use in treatment or prevention of an inflammatory bowel disease, gastrointestinal cancer, or a systemic bacterial infection in a subject in need thereof. They subject may be colonized by one or more pathogenic bacterial strains such as B. fragilis, E. faecalis, or C. perfringens. In certain aspects, the disclosure provides a method of diminishing the pathogenic effects of these bacterial stmins by administering a compound that binds to and/or inhibits one or more toxins produced thereby.

Described herein are compounds and compositions for use in treatment or prevention of an inflammatory bowel disease, gastrointestinal cancer, or a systemic bacterial infection in a subject in need thereof. They subject may be colonized by one or more pathogenic bacterial strains such as B. fragilis, E. faecalis, or C. perfringens. In certain aspects, the disclosure provides a method of diminishing the pathogenic effects of these bacterial stmins by administering a compound that binds to and/or inhibits one or more toxins produced thereby.

What is described is a compound of formula (1) ##STR00001##
wherein R.sub.1 and R.sub.2 are the same or different, each a linear or branched alkyl with 1-9 carbons, or an alkenyl or alkynyl with 2 to 11 carbon atoms; L.sub.1 and L.sub.2 are the same or different, each a linear alkyl having 5 to 18 carbon atoms, or form a heterocycle with N; X.sub.1 is a bond, or is COO whereby L.sub.2-COOR.sub.2 is formed; X.sub.2 is S or O; L.sub.3 is a bond or a lower alkyl, or form a heterocycle with N; R.sub.3 is a lower alkyl; and R.sub.4 and R.sub.5 are the same or different, each a lower alkyl;
or a pharmaceutically acceptable salt thereof.

What is described is a compound of formula (1) ##STR00001##
wherein R.sub.1 and R.sub.2 are the same or different, each a linear or branched alkyl with 1-9 carbons, or an alkenyl or alkynyl with 2 to 11 carbon atoms; L.sub.1 and L.sub.2 are the same or different, each a linear alkyl having 5 to 18 carbon atoms, or form a heterocycle with N; X.sub.1 is a bond, or is COO whereby L.sub.2-COOR.sub.2 is formed; X.sub.2 is S or O; L.sub.3 is a bond or a lower alkyl, or form a heterocycle with N; R.sub.3 is a lower alkyl; and R.sub.4 and R.sub.5 are the same or different, each a lower alkyl;
or a pharmaceutically acceptable salt thereof.

What is described is a compound of formula I ##STR00001##
consisting of a compound in which R.sub.1 is a branched chain alkyl consisting of 10 to 31 carbons; R.sub.2 is a linear alkyl, alkenyl, or alkynyl consisting of 2 to 20 carbons; L.sub.1 and L.sub.2 are the same or different, each a linear alkylene or alkenylene consisting of 2 to 20 carbons; X.sub.1 is S or O; R.sub.3 is a linear or branched alkylene consisting of 1 to 6 carbons; and R.sub.4 and R.sub.5 are the same or different, each a hydrogen or a linear or branched alkyl consisting of 1 to 6 carbons; or a pharmaceutically acceptable salt thereof.

What is described is a compound of formula I ##STR00001##
consisting of a compound in which R.sub.1 is a branched chain alkyl consisting of 10 to 31 carbons; R.sub.2 is a linear alkyl, alkenyl, or alkynyl consisting of 2 to 20 carbons; L.sub.1 and L.sub.2 are the same or different, each a linear alkylene or alkenylene consisting of 2 to 20 carbons; X.sub.1 is S or O; R.sub.3 is a linear or branched alkylene consisting of 1 to 6 carbons; and R.sub.4 and R.sub.5 are the same or different, each a hydrogen or a linear or branched alkyl consisting of 1 to 6 carbons; or a pharmaceutically acceptable salt thereof.

The present disclosure details various lipids, compositions, and/or methods of optimized systems and delivery vehicles for the delivery of nucleic acid sequences, polypeptides or peptides for use in vaccinating against infectious agents.