Described herein are compositions and methods for making and using recombinant bacteria that are capable of regulated attenuation and/or regulated expression of one or more antigens of interest.

The present invention provides compositions and methods of inducing an immune response in a subject in need thereof, comprising administering to the subject an immunologically-effective amount of a live Salmonella Typhi vector comprising a heterologous antigen from a pathogen, wherein the heterologous antigen comprises an outer membrane protein, an antigenic fragment thereof or a variant thereof, wherein the antigen is delivered to a mucosal tissue of the subject by an outer membrane vesicle.

The present invention provides compositions and methods for inducing an immune response in a subject in need thereof, comprising administering to the subject an immunologically-effective amount of a live Salmonella Typhi vector, wherein the Salmonella Typhi vector has been engineered to express one or more cancer antigens. In some aspects the vector has been engineered to express an outer membrane folding protein BamA or a fragment or variant thereof; and a lipid A deacylase PagL or a fragment or variant thereof, wherein the Salmonella Typhi vector is capable of delivering the antigen to a mucosal tissue or subcutaneously to dendritic cells via an outer membrane vesicle when administered to a subject.

Disclosed is a live self-destructing attenuated adjuvant Salmonella strain, or a derivative thereof, capable of safe in ovo inoculation into embryonated avian eggs without reduction in hatchability. In certain examples, the live self-destructing attenuated adjuvant Salmonella strain comprises an attenuated Salmonella typhimurium (S. typhimurium) bacterium, comprising one or more mutations resulting in in vivo self-destruction selected from the group consisting of Δalr, ΔdadB, ΔasdA, ΔP.sub.asdA::TT araC P.sub.araBADasd, ΔP.sub.dadB::TT araC P.sub.araBADdadB, ΔP.sub.asdA::TT rhaRSP.sub.rhaBADasd, ΔP.sub.dadB::TT rhaRSP.sub.rhaBADdadB and/or ΔP.sub.murA::TT rhaRSP.sub.rhaBADmurA. Also disclosed are method of using the attenuated adjuvant Salmonella strains to inoculate Avian species.

The present disclosure relates to novel immunogenic monovalent and multivalent polysaccharide-protein conjugate vaccine compositions comprising a polysaccharide selected from Salmonella serovar strains S. typhi; S. paratyphi A; S. typhimurium and S. enteritidis and alternative improved methods of polysaccharide fermentation, polysaccharide purification, polysaccharide-protein conjugation and stable formulation. The present disclosure further relates to methods for inducing an immune response in subjects against Salmonella typhi and non-typhi related diseases and/or for reducing or preventing Salmonella typhi and non-typhi related diseases in subjects using the compositions disclosed herein. The vaccine elicits bactericidal antibodies and is useful for prevention of gastroenteritis, enteric and typhoid fever.

A vaccine delivery method is presented that includes a composition including as one component a slurry matrix that is a liquid at room temperature and a gel at physiological pH, physiological salt concentrations and/or physiological temperatures and as a second component one or more antigens. Also included are methods of inducing an immune response in a subject and vaccinating a subject by administering such compositions.

Heptose-1-monophosphate-7-derivatives are modifiable immunomodulators that can be used to prepare clinically active conjugate compounds. Such conjugate compounds are useful in modulating an immune response in a subject.

The present disclosure relates to Salmonella Gallinarum mutant strains and uses thereof. A vaccine composition according to an aspect has no risk of reverting to pathogenicity, has no residual pathogenicity due to detoxification of an endotoxin, and does not cause lesions and bacterial re-isolation, thereby exhibiting significantly improved safety compared to the existing fowl typhoid vaccines. In addition, since the vaccine composition induces a high-level immune response even when administered to young chicks, it may be used regardless of age, and as the vaccine strain may be used as a live vaccine having an excellent protective capability by itself, the vaccine composition may be useful for preventing and alleviating fowl typhoid.

Disclosed is the attenuated Salmonella typhi vaccine Ty21a utilized as a vector for Shigella and/or enterotoxogenic E. coli genes stably integrated in the Ty21a chromosome. These genes include a heterologous Shigella sonnei O-antigen biosynthetic gene region that comprises the wzz gene and expresses Shigella sonnei form 1 O-antigen, as well as a heterologous acid resistance biosynthetic gene system comprising a YbaS gene, which enables increased stability of the Ty21a vector at pH 2.5 relative to Ty21a without the integrated acid resistance biosynthetic gene system.

The present invention relates to an attenuated strain of Salmonella comprising at least one copy of a DNA molecule comprising an expression cassette encoding PD-L1. In particular, the present invention relates to said attenuated strain of Salmonella for use in the treatment of cancer.