Oxidative burst mediated by toll like receptors (TLR) and CD14 on avian heterophils stimulated with bacterial toll agonists

Toll-like receptors (TLRs) recognize pathogen-associated molecular patterns (PAMPs) such as lipopolysaccharide (LPS) and lipoteichoic acid (LTA), which are found in the cell walls of gram-negative and gram-positive bacteria, respectively. This study was conducted to determine if TLRs are present on chicken heterophils and if these receptors mediate oxidative burst. Heterophils isolated from neonatal chicks were exposed to gram-negative Salmonella enteritidis (SE), gram-positive Staphylococcus aureus (SA), SE-LPS, and SA-LTA and the oxidative burst quantitated by luminol-dependent chemiluminescence. SE, SA, SE-LPS, and SA-LTA stimulated a significant increase in oxidative burst from heterophils. Furthermore, we measured the inhibitory effects of polyclonal antibodies on rat CD14, human TLR2 and TLR4 on the oxidative burst of heterophils when stimulated with LPS and LTA. The data suggest that TLR2 and TLR4 mediate LPS-stimulated oxidative burst while CD14 and TLR2 mediate LTA-stimulated oxidative burst in heterophils. This is the first report of PAMPs from gram-positive and gram-negative bacteria interacting with TLRs of avian heterophils.

Sterol carrier protein-2 functions in phosphatidylinositol transfer and signaling

Over 20 years ago, it was reported that liver cytosol contains at least two distinct proteins that transfer phosphatidylinositol in vitro, phosphatidylinositol transfer protein (PITP) and a pH 5.1 supernatant fraction containing sterol carrier protein-2 (SCP-2). In contrast to PITP, there has been minimal progress on the structural and functional significance of SCP-2 in phosphatidylinositol transport. As shown herein, highly purified, recombinant SCP-2 stimulated up to 13-fold the rapid (s) transfer of radiolabeled phosphatidylinositol (PI) from microsomal donor membranes to highly curved acceptor membranes. SCP-2 bound to microsomes in vitro and overexpression of SCP-2 in transfected L-cells resulted in the following: (i) redistribution of phosphatidylinositols from intracellular membranes (mitochondria and microsomes) to the plasma membrane; (ii) enhancement of insulin-mediated inositol-triphosphate production; and (iii) 5.5-fold down regulation of PITP. Like PITP, SCP-2 binds two ligands required for vesicle budding from the Golgi, PI, and fatty acyl CoA. Double immunolabeling confocal microscopy showed SCP-2 significantly colocalized with caveolin-1 in the cytoplasm (punctate) and plasma membrane of SCP-2 overexpressing hepatoma cells (72%), HT-29 cells (58%), and SCP-2 overexpressing L-cells (37%). Taken together, these data show for the first time that SCP-2 plays a hitherto unrecognized role in intracellular phosphatidylinositol transfer, distribution, and signaling.

Functional comparison of heterophils isolated from commercial broiler chickens

Heterophils from two pure lines (A and B) of commercial broiler chickens were isolated on days 1, 4, and 7 post-hatch to evaluate their ability to (1) phagocytose Salmonella enteritidis (SE) (2) degranulate when exposed to immune-IgG opsonized SE, and (3) produce an oxidative burst. On days 1 and 4, heterophils from line A were functionally more efficient compared to heterophils from line B (p<0.05). By 7 days post hatch, heterophil functions for both lines were comparable. To further study the inheritance of heterophil functional efficiency, F1 reciprocal crosses (line C=male Bxfemale A; line D=male Axfemale B) were evaluated for functional activity and compared with the immunologically efficient (A) and non-efficient (B) parent lines. Heterophils from line D had a more efficient heterophil function (p<0.05) when compared to heterophils from C. These results suggest that heterophil function and efficiency can be genetically transferred to progeny. Moreover they indicate that heterophil function is sex-associated and genetically controlled by the rooster since progeny of line A males maintained immunologically efficient characteristics whereas heterophils from the progeny of line B roosters remained immunologically inefficient. To our knowledge, this is the first report to describe a functional relationship between pure and F1 reciprocal crosses of broiler chickens with regard to heterophils and the innate immune response.

The envelope glycoprotein of simian immunodeficiency virus contains an enterotoxin domain

By the use of a mouse model, the enteropathic effects of the simian immunodeficiency virus (SIV) surface unit (SU) envelope glycoprotein were explored. Purified SU (0.01-0.45 nmol) was administered intraperitoneally to 6- to 8-day-old mouse pups and induced a dose-dependent diarrheal response. Surgical introduction of SU into adult mouse intestinal loops revealed fluid accumulation without histological alterations and SU-treated unstripped intestinal mucosa induced chloride (Cl(-)) secretory currents in Ussing chambers. Similarly to rotavirus NSP4, the first described viral enterotoxin, SU induced a transient increase in intracellular calcium levels and increased inositol 1,4,5-triphosphate (IP(3)) levels in HT-29 cells. These data indicate the calcium response is mediated by IP(3). The presence of diarrhea and fluid accumulation within intestinal loops in the absence of histological alterations and induction of Cl(-) secretory currents demonstrate that SIV contains an enterotoxic domain localized within SU and is the second viral enterotoxin described.