Synthetic bovine NK-lysin-derived peptide (bNK2A) does not require intra-chain disulfide bonds for bactericidal activity

Future of Immune Modulation in Animal Agriculture

Immune modulation in animal agriculture has been of research interest for several decades, yet only a few immunomodulators have received regulatory approval in the United States and around the world. In this review, we summarize market and regulatory environments impacting commercial development of immunomodulators for use in livestock and poultry. In the United States, very few immunomodulators have received regulatory approval for use in livestock by either the US Department of Agriculture Center for Veterinary Biologics or the Food and Drug Administration (FDA). To date, only one immunomodulator has received FDA approval, and an extensive body of peer-reviewed literature is available regarding the basis for its use and health benefits. We present a more thorough review of the history and impact of this immune restorative. Finally, we discuss the interaction of immunomodulators on health, metabolism, and other factors impacting the future of immune modulation in livestock.

Characterization of NK-lysin A, a potent antimicrobial peptide from the zebrafish Danio rerio

Antimicrobial peptides (AMPs) are important players of the innate immune system with a major role in the defense against invading pathogens. AMPs belonging to the family of saposin-like proteins (SAPLIPs) include the porcine NK-lysin and the human granulysin. In the zebrafish Danio rerio, transcript analyses of NK-lysin encoding genes have been reported, but biochemical characterizations at the protein level are missing so far. Here, we present the recombinant expression, purification, and characterization of one of these homologs, namely of NK-lysin A (DaNKlA). To remove the affinity tag from DaNKlA, we made use of a self-splicing intein. Recombinant DaNKlA depolarized liposomes over a broad pH range and showed a preference for negatively charged lipids. DaNKlA inhibited the growth of and killed different Gram-positive and Gram-negative bacteria, including the fish pathogenic bacterium Vibrio anguillarum, by membrane permeabilization but displayed substantially lower activity against yeast cells. Structural modelling and bioinformatic comparison of DaNKlA with characterized SAPLIPs suggest membrane destabilization accompanied by strong electrostatic interactions as the mode of action.

Progress and persistence of diseases of high consequence to livestock in the United States

The USDA/ARS-National Disease Center (NADC) will celebrate its 65th anniversary of existence in November 2026. NADC continues as one of the world's premier animal health research centers conducting basic and applied research on endemic diseases with economic impact on U.S. livestock and wildlife. This research center also supports a program studying important food safety pathogens such as Salmonella, E. coli and Campylobacter. NADC has contributed significantly to the elimination of a few diseases, notably hog cholera and milk fever, and made progress in reducing the impact of many other animal diseases through vaccines, therapies and managerial recommendations. Despite nearly 65 years of targeted research on these diseases and much progress, some of these continue to persist. The reasons for such persistence varies for each disease condition and they are often multifactorial involving host susceptibility, virulence and even environmental conditions. Individually and in aggregate, these disease conditions have a massive economic impact and can be devasting to animal producers, owners and individuals that become infected through zoonotic disease agents such as tuberculosis, leptospirosis and avian influenza. They also diminish the health, well-being and welfare of affected animals, which directly affects the food supply. The NADC is using all available technologies including genomic, biochemical, reverse genetics, and vaccine trials in the target host to combat these significant diseases. We review the progress and reasons for persistence of selected diseases and food safety pathogens as well as the progress and potential outcomes should research and programmatic plans to eliminate these disease conditions cease.

New insight into the biological activity of Salmo salar NK-lysin antimicrobial peptides

NK-lysin is a potent antimicrobial peptide (AMP) with antimicrobial activity against bacteria, fungi, viruses, and parasites. NK-lysin is a type of granulysin, a member of the saposin-like proteins family first isolated from a pig's small intestine. In previous work, for the first time, we identified four variants of nk-lysin from Atlantic salmon (Salmo salar) using EST sequences. In the present study, we reported and characterized two additional transcripts of NK-lysin from S. salar. Besides, we evaluated the tissue distribution of three NK-lysins from S. salar and assessed the antimicrobial, hemolytic, and immunomodulatory activities and signaling pathways of three NK-lysin-derived peptides. The synthetic peptides displayed antimicrobial activity against Piscirickettsia salmonis (LF-89) and Flavobacterium psychrophilum. These peptides induced the expression of immune genes related to innate and adaptive immune responses in vitro and in vivo. The immunomodulatory activity of the peptides involves the mitogen-activated protein kinases-mediated signaling pathway, including p38, extracellular signal-regulated kinase 1/2, and/or c-Jun N-terminal kinases. Besides, the peptides modulated the immune response induced by pathogen-associated molecular patterns (PAMPs). Our findings show that NK-lysin could be a highly effective immunostimulant or vaccine adjuvant for use in fish aquaculture.