Effect of recombinant human cytokines on porcine neutrophil function.

The activity of four recombinant human cytokines on porcine neutrophils was evaluated. Porcine neutrophils were treated with varying doses of recombinant human tumour necrosis factor-alpha (rHu-TNF), interferon-gamma (rHu-IFN), interleukin-8 (rHu-lL-8), or granulocyte-macrophage colony-stimulating factor (rHu-GM-CSF). The function of treated neutrophils was compared with that of non-treated controls in the following assays: antibody-independent neutrophil cytotoxicity (AINC), antibody-dependent cell-mediated cytotoxicity (ADCC), iodination, Staphylococcus aureus ingestion, cytochrome C reduction, random migration, and chemotaxis. Treatment with rHu-TNF produced significant (P < 0.05) depression of neutrophil random migration (2.5, 25, and 250 ng ml-1 rHu-TNF) and iodination (250 ng ml-1) and a near significant (P = 0.08) depression in ADCC (250 ng ml-1). Treatment with 25,000 U ml-1 of rHu-IFN caused a significant increase in AINC. At lower doses of rHu-IFN, there was a trend (0.05 < P < or = 0.08) toward depression of AINC (250 U ml-1) and ADCC (25 U ml-1) and enhancement of iodination (250 U ml-1). Treatment with 50 ng ml-1 of rHu-IL-8 caused a near significant increase (P = 0.06) in AINC. There were no significant differences noted when porcine neutrophils were treated with rHu-GM-CSF (2.5-2500 U ml-1). No synergism was noted between rHu-TNF and rHu-IFN.

Alteration of neutrophil function in BCG-treated and non-treated swine after exposure to Salmonella typhimurium.

Salmonella typhimurium infection in swine causes an enterocolitis followed by a persistent carrier state, but little is known about the mechanisms that allow this organism to colonize and persist in host tissues. Neutrophils provide a first line of defense against invading pathogens such as Salmonella typhimurium. The purpose of this study was to evaluate porcine neutrophil function after in vivo exposure to Salmonella and to determine if the immunomodulator, bacillus Calmette Guerin (BCG), exerts any effect on neutrophil function or on the colonization and persistence of S. typhimurium in the pig. Compared to negative controls, neutrophils from pigs exposed to S. typhimurium exhibited significantly decreased iodination, cytochrome-C reduction, antibody-dependent cell-mediated cytotoxicity, random migration, and chemotaxis (P less than or equal to 0.05). Neutrophil bactericidal activity against S. typhimurium was significantly enhanced. Most of the significant differences were noted in the first two days after exposure to Salmonella. Often the functional alterations were biphasic, peaking again 7-10 days after exposure. BCG alone significantly depressed random migration and cytochrome-C reduction in unstimulated neutrophils. The clinical course, colonization pattern, and persistence of Salmonella were similar between pigs receiving BCG and untreated pigs. These data suggest that S. typhimurium infection causes a depression in oxidative metabolism and motility, yet an increase in overall bactericidal activity against S. typhimurium in circulating porcine neutrophils. It also appears that BCG treatment, as reported here, does not enhance resistance of pigs to S. typhimurium colonization or reduce the number of persistent organisms in the porcine ileum.

The effect of exposure to a delta cya/delta crp mutant of Salmonella typhimurium on the subsequent colonization of swine by the wild-type parent strain.

This study characterizes the clinical response and colonization pattern of caesarean-derived, colostrum-deprived swine exposed to a delta cya/delta crp mutant (chi 4233) of S. typhimurium and challenged with the wild-type parent strain. chi 4233 was mildly virulent in swine and induced transient fever and soft stools. Chi 4233 colonized the ileum, cecum, liver, spleen, tonsils, and mandibular and ileocolic lymph nodes of swine in a manner similar to the parental wild-type, but the numbers of S. typhimurium (chi 4233) in the ileum were 100- to 1000-fold less than those of pigs exposed to the parental wild-type. Pigs exposed to chi 4233 21 days before parental wild-type challenge demonstrated a milder clinical response to challenge than did pigs that did not receive chi 4233. The wild-type populations in the ilea of chi 4233-exposed pigs after challenge were 100- to 10,000-fold less than those in pigs not receiving chi 4233. The liver, spleen, and ileocolic lymph nodes were cleared of wild-type S. typhimurium more quickly after challenge in chi 4233-exposed pigs. The populations of chi 4233 in the ilea of exposed pigs after wild-type challenge were also less than would have been expected in unchallenged pigs. Thus, exposure of swine to a delta cya/delta crp mutant of S. typhimurium modulated the subsequent response to parental wild-type challenge and reduced carrier populations of wild-type S. typhimurium in infected swine.

Pseudorabies virus glycoprotein III derived from virions and infected cells binds to the third component of complement.

Glycoprotein III (gIII) of pseudorabies virus (PRV) was shown to bind to the third component of complement (C3). This was observed only with porcine C3 whereas human C3 showed negligible binding under the conditions tested. PRV virion proteins could be precipitated from supernatants and cell lysates of PRV-infected cells by means of swine-C3 coupled to sepharose. According to their molecular size and their reactivity with anti-gIII monoclonal antibodies, the precipitated PRV proteins represented the fully glycosylated and smaller forms of the gIII protein. Precipitation from PRV virions yielded predominantly the fully glycosylated form of gIII whereas infected cell lysates also contained lower molecular weight gIII proteins. The observed specificity of the virus protein for porcine C3 correlates well with the known host tropism of PRV. Our findings suggest that PRV gIII may exhibit more functions than solely providing attachment to heparin-like moieties on target cell surfaces. As the complement cascade is an important defense mechanism against a variety of pathogens, the interaction with the host C3, the pivotal component of the complement activation, might be a virulence factor of PRV.

Experimental establishment of persistent infection in swine with a zoonotic strain of Salmonella newport.

An experiment was conducted to determine whether a persistent Salmonella newport infection could be established in swine, to determine duration of shedding and distribution of the organism in internal organs, and to determine whether changes occurred in antimicrobial susceptibility or plasmid profile of the organism during the course of long-term infection. Naturally farrowed Salmonella-free pigs (n = 22) were orally exposed to a multiply antimicrobial-resistant zoonotic strain of S newport when they were 7 weeks old. Tonsillar and rectal swab specimens were examined bacteriologically for S newport during the first week after exposure, then weekly for 7 weeks. Fecal samples were likewise examined weekly or every 2 weeks for 28 weeks after exposure. Necropsies of 2 or 3 randomly selected pigs were conducted at 2, 4, 8, 12, 16, 20, 24, and 28 weeks after exposure. A total of 45 specimens/pig representing the following internal organs or tissues were examined bacteriologically for S newport: liver, spleen, kidney, gallbladder, heart, heart blood, lung, stomach, and tonsils; segments of the intestinal tract with corresponding lymph nodes; and lymph nodes from lymphocenters of the head and neck, thoracic cavity, thoracic limbs, abdominal viscera, and abdominal wall. Exposure to S newport induced a mild and transient clinical response. The organism was recovered from 97% of tonsillar swab specimens and 89% of rectal swab specimens collected during 7 weeks after exposure and from 98% of fecal samples collected during 28 weeks after exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Mapping and characterization of neutralizing epitopes of glycoproteins gIII and gp50 of the Indiana-Funkhauser strain of pseudorabies virus.

Neutralizing monoclonal antibodies directed against pseudorabies glycoproteins gIII or gp50 were produced. Using these antibodies in competitive binding ELISAs, three overlapping epitopes for gp50 and two nonoverlapping epitopes for gIII were mapped.