A novel inactivated vaccine against Lawsonia intracellularis induces rapid induction of humoral immunity, reduction of bacterial shedding and provides robust gut barrier function.

Porcine proliferative ileitis is a major economic burden for the swine industry, affecting growing pigs and young adult pigs. In this study, the protective efficacy of an inactivated, injectable whole-cell bacteria vaccine against L. intracellularis - Porcilis® Ileitis was evaluated under field conditions. Eighty-five, three-week-old pigs on a commercial farrow-to-finish farm were vaccinated by the intramuscular route, either with a dose of injectable vaccine, or with saline. A subset of vaccinates and control pigs were necropsied at 21 days post-challenge. Incidence and severity of ileitis were evaluated by gross and microscopic observation of ileal tissues. Colonization of the gut after challenge was examined by L. intracellularis-specific immunohistochemistry, and qPCR of ileal scrapings. Integrity of the intestinal barrier was evaluated to quantify a range of intestinal markers including secreted mucin and intestinal alkaline phosphatase, and innate immune markers including Caspase-3 and Calprotectin. A second subset of pigs was monitored for fecal shedding of L. intracellularis, until resolution of shedding. Our investigation indicated that Porcilis Ileitis provided robust protection against ileitis, reduced bacterial shedding 15-fold (p < .05) and preserved normal gut barrier function in the face of an experimental challenge with virulent L. intracellularis.

Optimization of an antibiotic sensitivity assay for Mycoplasma hyosynoviae and susceptibility profiles of field isolates from 1997 to 2011.

Mycoplasma hyosynoviae is a common agent responsible for polyarthritis leading to decreased production in swine herds worldwide. Antimicrobial agents are used to combat infections; however breakpoints for M. hyosynoviae have not yet been established. A number of methods have previously been utilized to analyze minimum inhibitory concentrations (MICs) for antibiotics against M. hyosynoviae; however these techniques as currently described are not easily standardized between laboratories. A dry microbroth dilution method was conducted to compare the minimum inhibitory concentrations (MICs) for 18 antibiotics, representative of different classes, against 24 recent isolates (23 field isolates and the type strain) of M. hyosynoviae. The MICs were determined using standard, commercially available 96-well Sensititre(®) plates containing various freeze-dried antibiotics at a range of concentrations appropriate to their potency. Clindamycin (CLI), a lincosamide antibiotic, showed the highest activity and most consistent inhibition for all isolates with an MIC(50) of ≤ 0.12 µg/ml. Tiamulin (TIA), a pleuromutilin derivative, exhibited an MIC(50) of ≤ 0.25 µg/ml. The isolates had similar levels of susceptibility to the quinolones, enrofloxacin (ENRO) and danofloxacin (DANO), exhibiting an MIC(50) of 0.25 µg/ml and 0.5 µg/ml, respectively. For the macrolides, the MIC(50) for tylosin (TYLT) and tilmicosin (TIL) was ≤ 0.25 µg/ml and ≤ 2 µg/ml respectively, but was ≤ 16 µg/ml for tulathromycin (TUL). For the aminoglycosides, the MIC(50) for gentamicin (GEN) was ≤ 0.5 µg/ml, while spectinomycin (SPE) and neomycin (NEO) had an MIC(50) of ≤ 4 µg/ml. The tetracyclines, oxytetracycline (OXY) and chlortetracycline (CTET) both had an MIC(50) of ≤ 2 µg/ml. Florfenicol (FFN) exhibited a MIC(50) of ≤ 1 µg/ml. All isolates were resistant to penicillin (PEN), ampicillin (AMP), ceftiofur (TIO), trimethoprim/sulfamethoxazole (SXT), and sulphadimethoxine (SDM) at all concentrations. Within the isolates tested, there was a range of sensitivity detected, with some isolates being overall more resistant while others appeared more susceptible. Further research is required to demonstrate how this MIC data correlates to clinical efficacy of the various antibiotics in the field.

The antibody responses to swine influenza virus (SIV) recombinant matrix 1 (rM1), matrix 2 (M2), and hemagglutinin (HA) proteins in pigs with different SIV exposure.

The influenza invariant matrix 2 (M2) protein is a potential subunit vaccine candidate to induce protective immunity against broader strains of influenza A viruses (IAV). Antibodies to M2 protein have not been well characterized in IAV natural hosts. To characterize M2-specific antibodies in pigs, an ELISA to the extracellular region of the M2 (M2e) protein was developed. Sera from pigs experimentally infected with three different swine influenza virus (SIV) subtypes, immunized with an SIV inactivated vaccine, or positive for SIV maternally derived antibodies (MDA) in the absence of SIV infection were tested in assay. Confirmation of antibody titer status of pigs, was determined using a hemagglutination-inhibition (HI) test and the presence of antibodies to matrix 1 (M1) protein was measured by a recombinant M1 (rM1)-based ELISA. The antibody titers to the HA and M2e proteins but not to the rM1 were directly correlated to the dose of virus used to infect the pigs and the level of antibodies detected by the HI assay varied according to SIV subtype. Pigs experimentally infected with SIV produced low levels of M2e antibodies compared to antibodies detected by the HI and rM1 assays. Vaccination alone followed by infection did not increase the levels of M2e antibodies in contrast to HA and rM1 antibodies. Pigs with MDA had different levels of HA antibodies and were positive to M2e antibodies, but results were not correlated to HA antibodies levels and inconsistently present.