Leptosome-entrapped leptospiral antigens conferred significant higher levels of protection than those entrapped with PC-liposomes in a hamster model

We prepared novel liposomes from total polar lipids of non-pathogenic Leptospira biflexa serovar Potac (designated leptosomes) and evaluated their vaccine delivery/adjuvant potential with novel protective antigens (Lp0607, Lp1118 and Lp1454) of L. interrogans serovar Pomona in a hamster model. The immune response induced by three individual antigens and protective efficacy were evaluated and compared to those induced by same antigens entrapped with PC-liposomes and E. coli lipid liposomes (escheriosomes). Four-week-old hamsters were immunized subcutaneously twice at a 3-week interval, bled at various time points to evaluate antibody response and sacrificed to isolate splenocytes for lymphocyte proliferation and cytokine profiles in response to recall antigen. For the challenge test, 10x MLD(50) (modified lethal dose 50%) of virulent L. interrogans serovar Pomona were administered intraperitoneally. Our results demonstrate that leptosome are better adjuvant than PC-liposomes as revealed by enhanced long term antibody response, lymphocyte proliferation and significant enhancement of both Th1 (IFN-gamma) and Th2 (IL-4 and IL-10) cytokines. Additionally, leptosomes and escheriosomes induced significantly higher level of memory responses than PC-liposome did. Moreover, the novel leptosomal vaccine induced significantly higher levels of protection than those prepared with PC-liposomes as revealed by enhanced survival, reduced histopathological lesions in vital organs and reduced leptospiral load in kidneys. Taken together, the results of the present study clearly reveal that both leptosomes and escheriosomes have emerged as promising delivery vehicles/adjuvants that can be widely exploited with newly discovered antigens in future leptospira vaccines.

Fibronectin binds to and induces conformational change in a disordered region of leptospiral immunoglobulin-like protein B

Leptospira interrogans is a pathogenic spirochete that causes disease in both humans and animals. LigB (Leptospiral immunoglobulin-like protein B) contributes to the binding of Leptospira to extracellular matrix proteins such as fibronectin (Fn), fibrinogen, laminin, and collagen. A high affinity Fn-binding region of LigB has been recently localized to LigBCen2, which contains the partial eleventh and full twelfth immunoglobulin-like repeats (LigBCen2R) and 47 amino acids of the non-repeat region (LigBCen2NR) of LigB. In this study, LigBCen2NR was shown to bind to the N-terminal domain (NTD) of Fn (K(D) = 379 nm) by an enzyme-linked immunosorbent assay and isothermal titration calorimetry. Interestingly, this sequence was not observed to adopt secondary structure by far UV circular dichroism or by differential scanning calorimetry, in agreement with computer-based secondary structure predictions. A low partition coefficient (K(av)) measured with gel permeation chromatography, a high hydrodynamic radius (R(h)) measured with dynamic light scattering, and the insensitivity of the intrinsic viscosity to guanidine hydrochloride treatment all suggest that LigBCen2NR possesses an extended and disordered structure. Two-dimensional (15)N-(1)H HSQC NMR spectra of intact LigBCen2 in the absence and presence of NTD are consistent with these observations, suggesting the presence of both a beta-rich region and an unstructured region in LigBCen2 and that the latter of these selectively interacts with NTD. Upon binding to NTD, LigBCen2NR was observed by CD to adopt a beta-strand-rich structure, suggestive of the known beta-zipper mode of NTD binding.

A novel fibronectin type III module binding motif identified on C-terminus of Leptospira immunoglobulin-like protein, LigB

Infection by pathogenic strains of Leptospira hinges on the pathogen's ability to adhere to host cells via extracellular matrix such as fibronectin (Fn). Previously, the immunoglobulin-like domains of Leptospira Lig proteins were recognized as adhesins binding to N-terminal domain (NTD) and gelatin binding domain (GBD) of Fn. In this study, we identified another Fn-binding motif on the C-terminus of the Leptospira adhesin LigB (LigBCtv), residues 1708-1712 containing sequence LIPAD with a beta-strand and nascent helical structure. This motif binds to 15th type III modules (15F(3)) (K(D)=10.70 microM), and association (k(on)=600 M(-1)s(-1)) and dissociation (k(off)=0.0129 s(-1)) rate constants represents a slow binding kinetics in this interaction. Moreover, pretreatment of MDCK cells with LigB(1706-1716) blocked the binding of Leptospira by 39%, demonstrating a significant role of LigB(1706-1716) in cellular adhesion. These data indicate that the LIPAD residues (LigB(1708-1712)) of the Leptospira interrogans LigB protein bind 15F(3) of Fn at a novel binding site, and this interaction contributes to adhesion to host cells.

Repeated domains of leptospira immunoglobulin-like proteins interact with elastin and tropoelastin

Leptospira spp., the causative agents of leptospirosis, adhere to components of the extracellular matrix, a pivotal role for colonization of host tissues during infection. Previously, we and others have shown that Leptospira immunoglobulin-like proteins (Lig) of Leptospira spp. bind to fibronectin, laminin, collagen, and fibrinogen. In this study, we report that Leptospira can be immobilized by human tropoelastin (HTE) or elastin from different tissues, including lung, skin, and blood vessels, and that Lig proteins can bind to HTE or elastin. Moreover, both elastin and HTE bind to the same LigB immunoglobulin-like domains, including LigBCon4, LigBCen7'-8, LigBCen9, and LigBCen12 as demonstrated by enzyme-linked immunosorbent assay (ELISA) and competition ELISAs. The LigB immunoglobulin-like domain binds to the 17th to 27th exons of HTE (17-27HTE) as determined by ELISA (LigBCon4, K(D) = 0.50 microm; LigBCen7'-8, K(D) = 0.82 microm; LigBCen9, K(D) = 1.54 microm; and LigBCen12, K(D) = 0.73 microm). The interaction of LigBCon4 and 17-27HTE was further confirmed by steady state fluorescence spectroscopy (K(D) = 0.49 microm) and ITC (K(D) = 0.54 microm). Furthermore, the binding was enthalpy-driven and affected by environmental pH, indicating it is a charge-charge interaction. The binding affinity of LigBCon4D341N to 17-27HTE was 4.6-fold less than that of wild type LigBCon4. In summary, we show that Lig proteins of Leptospira spp. interact with elastin and HTE, and we conclude this interaction may contribute to Leptospira adhesion to host tissues during infection.

ERK signaling in the pituitary is required for female but not male fertility

Males and females require different patterns of pituitary gonadotropin secretion for fertility. The mechanisms underlying these gender-specific profiles of pituitary hormone production are unknown; however, they are fundamental to understanding the sexually dimorphic control of reproductive function at the molecular level. Several studies suggest that ERK1 and -2 are essential modulators of hypothalamic GnRH-mediated regulation of pituitary gonadotropin production and fertility. To test this hypothesis, we generated mice with a pituitary-specific depletion of ERK1 and 2 and examined a range of physiological parameters including fertility. We find that ERK signaling is required in females for ovulation and fertility, whereas male reproductive function is unaffected by this signaling deficiency. The effects of ERK pathway ablation on LH biosynthesis underlie this gender-specific phenotype, and the molecular mechanism involves a requirement for ERK-dependent up-regulation of the transcription factor Egr1, which is necessary for LHbeta expression. Together, these findings represent a significant advance in elucidating the molecular basis of gender-specific regulation of the hypothalamic-pituitary-gonadal axis and sexually dimorphic control of fertility.

Single-dose pharmacokinetics and genotoxicity of metronidazole in cats

Single-dose pharmacokinetics and genotoxicity of metronidazole in cats were evaluated. Cats received either 5mg/kg metronidazole intravenously, or 20mg/kg metronidazole benzoate (12.4mg/kg metronidazole base) orally in a single dose. Serial plasma samples were collected and assayed for metronidazole using high pressure liquid chromatography (HPLC). Genotoxicity was assessed in vitro in feline peripheral blood mononuclear cells (PBMC) and a feline T-cell lymphoma line incubated with metronidazole, and in vivo in PBMC collected before, during and 7 days after oral metronidazole, by use of the COMET assay. Systemic absorption of metronidazole was variable (mean=65+/-28%) with a peak of 8.84+/-5.4microg/ml at 3.6+/-2.9h. The terminal half-life was 5.34h from the intravenous dose and 5.16h from the oral dose. Systemic clearance was low (mean=91.57ml/h/kg [1.53ml/kg/min]), and the apparent volume of distribution (steady state) was 0.650+/-0.254l/kg. Genotoxicity was detected at all concentrations of metronidazole in feline PBMC and the T-cell lymphoma line in vitro. Genotoxicity was also observed in PBMC collected from cats after 7 days of oral metronidazole but resolved within 6 days of discontinuing metronidazole.

Immunogenicity and protective efficacy of recombinant Leptospira immunoglobulin-like protein B (rLigB) in a hamster challenge model

Leptospiral immunoglobulin-like protein (LigB) was truncated into conserved (LigBcon) and variable (varB1, varB2) fragments and expressed as GST/His-tag fusion proteins. Four-week-old hamsters were immunized with equal amounts of each fragment individually or combined in alum adjuvant at days 0 and 21 and subsequently challenged three weeks after the booster with 2.5 LD(50) live virulent Leptospira interrogans serovar Pomona. Our results demonstrate that immunization with LigB produced strong humoral immune responses as revealed by high titers against each fragment and significant enhancement in Th2 cytokines (IL-4, IL-10). A significant activation of CMI is revealed by enhanced proliferation of lymphocytes and up regulation of Th1 cytokines (IL-12p40, IFN-gamma) was also noted. Of the peptides studied, rLigBcon was able to impart maximum protection (71%), followed by rVarB1 (54%), whereas rVarB2 was not able to impart a significant level of protection (33%) against lethal infection as revealed by enhanced survival and reduced severity of histopathological lesions in vital organs (viz. kidney, liver, spleen) of the immunized animals. Moreover, concurrent administration of all three fragments significantly enhanced the protective efficacy of the vaccine (83%). Overall, our results clearly demonstrate that LigB has emerged as novel protective antigen that can be used in future subunit vaccines against leptospirosis.

Cerebrospinal fluid findings in cattle with central nervous system disorders: a retrospective study of 102 cases (1990-2008)

BACKGROUND

Cerebrospinal fluid (CSF) analysis is routinely used to aid in the diagnosis of central nervous system (CNS) disease in animals. There is little comprehensive information available on the diagnostic utility of CSF analysis in cattle.

OBJECTIVES

The purpose of this retrospective study was to review the characteristic CSF findings of specific CNS diseases in cattle.

METHODS

Medical records of cattle in which CSF analysis had been performed between 1990 and 2008 were reviewed. Cattle were included in the study if they had a confirmed diagnosis of CNS disease (based on clinical signs, laboratory testing, and/or histopathologic results). Cattle were categorized as having infectious or noninfectious causes of CNS disease and subgrouped based on specific disease diagnosis. CSF results were summarized and compared using nonparametric statistical tests.

RESULTS

Data from 102 cattle, mostly female Holsteins, were included in the study. Bacterial infections, particularly listeriosis and neonatal meningitis, were the most common cause of CNS disease. Neonatal meningitis was characterized by a marked, predominantly neutrophilic, pleocytosis. Mild mononuclear pleocytosis was typical of listeriosis, but was also seen with abscesses, viral infections, salt poisoning, and trauma. Variable CSF results were seen in cattle with otitis-related meningitis and thromboembolic meningoencephalitis. CSF results were usually normal with toxic, metabolic, degenerative, and neoplastic disorders.

CONCLUSIONS

CSF analysis is a useful adjunctive test for the diagnosis of CNS diseases in cattle. When interpreted together with signalment and clinical signs, CSF results can assist clinicians in the antemortem diagnosis of specific bovine CNS disorders.

Immune responses in mice to Mycobacterium avium subsp. paratuberculosis following vaccination with a novel 74F recombinant polyprotein

Johne's disease (JD) is a chronic infectious disease of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). Here, we report the cloning and expression of a 74kDa recombinant polyprotein (Map74F) and its protective efficacy against MAP infection in mice. Map74F was generated by the sequential linkage of the ORFs of the approximately 17.6-kDa C-terminal fragment of Map3527 to the full-length ORF of Map1519, followed at the C-terminus with approximately 14.6-kDa N-terminal portion of Map3527. Mice immunized with Map74F had a significant IgG1 response but not IgG2a. In immunized animals, the IgG1/IgG2a ratio increased until 4 weeks after MAP challenge. The ratio decreased from 8 weeks indicating a shift to a Th1 response. Antigen specific IFN-gamma response, CD3+ and CD4+ T cells increased significantly in immunized mice. Following challenge, MAP burden was significantly lower in liver, spleen and mesenteric lymph nodes of immunized animals compared to control animals indicating protection against MAP infection. This was further evident by the improved liver and spleen pathology of the immunized animals, which had fewer granulomas and lower numbers of acid-fast bacilli. Results of this study indicated that immunization of mice with Map74F protected mice against MAP infection.

Evaluation of protective immunity of Leptospira immunoglobulin like protein A (LigA) DNA vaccine against challenge in hamsters

We demonstrated earlier that immunization with recombinant Leptospira immunoglobulin like protein A (LigA) induced significant protection against virulent Leptospira interrogans serovar Pomona challenge in hamsters. However, the protective immune mechanism remains unclear. In the present study we demonstrated the protective efficacy of a LigA DNA vaccine and evaluated the immune mechanism underlying the protection against leptospirosis in hamsters. The LigA DNA vaccine was constructed in two truncated forms as the conserved portion (LigAcon) and a variable portion (LigAvar). Four-week-old hamsters were immunized three times at two-week intervals with vector alone or an equal amount of a recombinant construct containing either LigAcon or LigAvar. All animals were challenged intraperitoneally 2 weeks after the last immunization with a dose (LD50=10(8)) of virulent L. interrogans serovar Pomona. Prior to challenge, four animals were sacrificed, the spleen was removed aseptically, and splenocytes were assayed for lymphocyte proliferation and cytokine profiles in response to recall antigen. The protective efficacy was evaluated on the basis of survival and histopathological lesions in the kidney. The immuno-protective mechanism was assessed on the basis of Th1/Th2 profile of cytokines in immunized animals. Our results indicate that immunization with LigA DNA vaccine provides significant protection against leptospirosis. We suggest that immuno-protection is conferred by both humoral and cellular immunity as revealed by an increase in antibody titers during subsequent boosters, significant proliferation of lymphocytes and enhancement of both Th1 and Th2 cytokines. Taken together, the present study suggests that a LigA DNA vaccine is a promising candidate for prevention of leptospirosis.

Antibody and skin-test responses of sheep vaccinated against Johne's Disease

Current vaccines against Mycobacterium avium subsp. paratuberculosis (MAP, Johne's Disease) may cause animals to react positively when tested for Mycobacterium bovis (Bovis). Therefore, the effects of vaccination on MAP serum Ab and skin-test responses to MAP and Bovis PPD were compared in 25 ewes vaccinated against MAP with 24 control ewes in an infected flock 3 years post-vaccination. MAP-specific Ab levels were higher (P<0.001) in vaccinated ewes than in control ewes. All increases in skinfold-thickness from 0 to 48h were greater (P<0.0001) than zero while increases in skinfold-thickness from 48 to 72h were greater (P<0.05) than zero for Johnin but not for Bovis PPD. The Vaccine x PPD x Time interaction for skinfold-thickness was significant (P<0.001) with greater increases to Johnin than to Bovis, but with much greater increases in vaccinated ewes. These data suggest that administration of vaccines against MAP developed from whole organisms increase the likelihood that animals will be classified as "responders" to a Bovis screening test and negative by the follow-up comparative cervical tuberculin test, but they also show that vaccination initiates both humoral and cell-mediated MAP-specific responses.

Fall panicum (Panicum dichotomiflorum) hepatotoxicosis in horses and sheep

BACKGROUND

Fourteen horses at a boarding stable in Virginia were diagnosed with hepatic disease and locally grown hay was implicated as the cause.

HYPOTHESIS

Panicum dichotomiflorum, the predominant grass species in the hay, is hepatotoxic to horses.

ANIMALS

Naturally occurring cases were adult horses of various breeds. Two healthy adult horses and 2 healthy adult sheep were used in feeding trials.

METHODS

Blood and liver specimens collected from affected animals during the outbreak were analyzed. Some of the affected animals were treated supportively; the main intervention was hay withdrawal. Feeding trials were not blinded and no treatments were provided. Blood and liver specimens were collected and analyzed throughout the trials.

RESULTS

Five affected animals were euthanized, whereas the others recovered. One research horse was euthanized for postmortem examination, and the other research animals recovered after hay withdrawal. All affected animals had evidence of hepatic disease with abnormally high aspartate aminotransferase (AST), sorbitol dehydrogenase (SDH), gamma glutamyl transferase (GGT), and alkaline phosphatase (ALP) activity. Evaluation of liver biopsy specimens disclosed mild lymphocytic and histiocytic inflammation, mild vacuolar change (hydropic degeneration), prominently clumped chromatin, and necrosis of individual hepatocytes.

CONCLUSIONS AND CLINICAL IMPORTANCE

Severe hepatotoxicosis developed rapidly after Panicum hay exposure. Patchy hepatocyte necrosis was observed, implicating apoptosis as the mechanism of hepatotoxicosis. Absence of fibrosis in the research animals indicates that immediate withdrawal of Panicum hay should allow all but severely affected animals to recover from acute exposure.

Association of Helicobacter with cholangiohepatitis in cats

Infection with Helicobacter spp. is increasingly linked with hepatobiliary inflammation and neoplasia in people and in a variety of animals. We sought to determine if Helicobacter species infection is associated with cholangiohepatitis in cats. Deoxyribonucleic acid was extracted from tissue blocks from cats with cholangiohepatitis (32), noninflammatory liver disease (13), and cats with normal liver histology (4). Deoxyribonucleic acid was polymerase chain reaction-amplified with 2 sets of Helicobacter genus-specific primers, gel purified, and sequenced. Polymerase chain reaction-positive hepatic tissue was further examined with Steiner's stain, immunocytochemistry for Helicobacter species, and eubacterial fluorescent in situ hybridization. Gastric tissues of cats with known Helicobacter infection status served as controls for deoxyribonucleic acid extraction and sequence comparison. Helicobacter species were detected in 2/32 cats with cholangiohepatitis, and 1/17 controls. Sequences had 100% identity with Helicobacter species liver, Helicobacter pylori, and Helicobacter fenelliae/cinaedii in a cat with suppurative cholangitis, Helicobacter species liver, Helicobacter pylori, and Helicobacter nemistrineae in a cat with mild lymphocytic portal hepatitis, and Helicobacter bilis in a cat with portosystemic vascular anomaly. In contrast, sequences from gastric biopsies showed highest homology (99-100%) to "Helicobacter heilmannii," Helicobacter bizzozeronii, Helicobacter felis, and Helicobacter salomonis. Fluorescent in situ hybridization revealed a semicurved bacterium, with Helicobacter-like morphology, in an intrahepatic bile duct of the cat with suppurative cholangitis. This study has identified Helicobacter deoxyribonucleic acid in 2/32 cats with cholangiohepatitis and 1/13 cats with noninflammatory liver disease. Deoxyribonucleic acid sequences of hepatic Helicobacter species were distinct from those found in the stomach and are broadly consistent with those identified in cat intestine and bile, and hepatobiliary disease in people and rodents.

Prospective evaluation of the balloon-to-annulus ratio for valvuloplasty in the treatment of pulmonic stenosis in the dog

BACKGROUND

In dogs, treatment of pulmonic valve stenosis (PS) with pulmonary balloon valvuloplasty (PBV) is a viable method to decrease the pressure gradient across the valve. However, to the authors' knowledge, the variables that influence the selection of the correct balloon size for the procedure have not been explored. Moreover, the lesions caused by the procedure have not been detailed.

HYPOTHESIS

Variables that influence the measurement of the annulus could affect selection of the balloon size. We sought to determine the effects of treatment when the balloon-to-annulus ratio (BAR) was or > 1.3, but within the recommended range of 1.2-1.5, regardless of whether dilation was performed with single or double balloon technique.

ANIMALS

Twenty-five Beagles with PS were studied.

METHODS

Inter- and intra-observer variability, echocardiography versus angiocardiography, and systolic versus diastolic timing were evaluated for the BAR. Assessment of right ventricular (RV) pressure, Doppler gradient, stenotic valve area, and RV wall thickness were compared before and 1, 90, and 180 days after treatment. Postmortem examination of the heart was done.

RESULTS

Significant correlations existed in measurement of the annulus; however, variation existed that would change balloon size. Improvement in the degree of PS was significant regardless of the BAR or single or double ballooning. In the most severely affected dogs, continued improvement was noted on day 90. Postmortem examination revealed tears in the commissures and the valve leaflets.

CONCLUSIONS

Multiple factors influenced determination of the BAR and a range of 1.2-1.5 was effective without detrimental consequences. Dogs with severe PS had continued decrease in RV pressure 3 months after treatment.

Adherent and invasive Escherichia coli is associated with granulomatous colitis in boxer dogs

The mucosa-associated microflora is increasingly considered to play a pivotal role in the pathogenesis of inflammatory bowel disease. This study explored the possibility that an abnormal mucosal flora is involved in the etiopathogenesis of granulomatous colitis of Boxer dogs (GCB). Colonic biopsy samples from affected dogs (n = 13) and controls (n = 38) were examined by fluorescent in situ hybridization (FISH) with a eubacterial 16S rRNA probe. Culture, 16S ribosomal DNA sequencing, and histochemistry were used to guide subsequent FISH. GCB-associated Escherichia coli isolates were evaluated for their ability to invade and persist in cultured epithelial cells and macrophages as well as for serotype, phylogenetic group, genome size, overall genotype, and presence of virulence genes. Intramucosal gram-negative coccobacilli were present in 100% of GCB samples but not controls. Invasive bacteria hybridized with FISH probes to E. coli. Three of four GCB-associated E. coli isolates adhered to, invaded, and replicated within cultured epithelial cells. Invasion triggered a "splash"-type response, was decreased by cytochalasin D, genistein, colchicine, and wortmannin, and paralleled the behavior of the Crohn's disease-associated strain E. coli LF 82. GCB E. coli and LF 82 were diverse in serotype and overall genotype but similar in phylogeny (B2 and D), in virulence gene profiles (fyuA, irp1, irp2, chuA, fepC, ibeA, kpsMII, iss), in having a larger genome size than commensal E. coli, and in the presence of novel multilocus sequence types. We conclude that GCB is associated with selective intramucosal colonization by E. coli. E. coli strains associated with GCB and Crohn's disease have an adherent and invasive phenotype and novel multilocus sequence types and resemble E. coli associated with extraintestinal disease in phylogeny and virulence gene profile.

Immunoprotection of recombinant leptospiral immunoglobulin-like protein A against Leptospira interrogans serovar Pomona infection

We previously reported the cloning and characterization of leptospiral immunoglobulin-like proteins LigA and LigB of Leptospira interrogans. LigA and LigB are conserved at the amino-terminal region but are variable at the carboxyl-terminal region. Here, we evaluate the potential of recombinant LigA (rLigA) as a vaccine candidate against infection by L. interrogans serovar Pomona in a hamster model. rLigA was truncated into conserved (rLigAcon) and variable (rLigAvar) regions and expressed in Escherichia coli as a fusion protein with glutathione-S-transferase (rLigA). Golden Syrian hamsters were immunized at 3 and 6 weeks of age with rLigA (rLigAcon and rLigAvar) with aluminum hydroxide as an adjuvant. Hamsters given recombinant glutathione-S-transferase (rGST)-adjuvant and phosphate-buffered saline-adjuvant served as nonvaccinated controls. Three weeks after the last vaccination, all animals were challenged intraperitoneally with 10(8) L. interrogans serovar Pomona bacteria (NVSL 1427-35-093002). All hamsters immunized with recombinant LigA survived after challenge and had no significant histopathological changes. In contrast, nonimmunized and rGST-immunized hamsters were subjected to lethal doses, and the hamsters that survived showed severe tubulointerstitial nephritis. All vaccinated animals showed a rise in antibody titers against rLigA. Results from this study indicate that rLigA is a potential vaccine candidate against L. interrogans serovar Pomona infection.

Novel attenuated Salmonella enterica serovar Choleraesuis strains as live vaccine candidates generated by signature-tagged mutagenesis

Salmonella enterica serovar Choleraesuis is a host-adapted pathogen that causes swine paratyphoid. Signature-tagged mutagenesis (STM) was used to understand the pathogenicity of S. enterica serovar Choleraesuis in its natural host and also to develop novel attenuated live vaccine candidates against this disease. A library of 960 signature-tagged mutants of S. enterica serovar Choleraesuis was constructed and screened for attenuation in pigs. Thirty-three mutants were identified by the STM screening, and these mutants were further screened for attenuation by in vivo and in vitro competitive growth. Of these, 20 mutants targeting the outer membrane, type III secretion, transporter, lipopolysaccharide biosynthesis, and other unknown proteins were confirmed for attenuation. Five highly attenuated mutants (SC2D2 [ssaV], SC4A9 [gifsy-1], SC6F9 [dgoT], SC12B12 [ssaJ], and SC10B1[spiA]) were selected and evaluated for safety and protective efficacy in pigs by comparison with a commercially available vaccine strain. STM-attenuated live vaccine strains SC4A9 (gifsy-1) and SC2D2 (ssaV) were superior to commercially available live vaccine because they provided both safety and a protective immune response against challenge in pigs.

In vitro cellular immune responses to recombinant antigens of Mycobacterium avium subsp. paratuberculosis

Five recombinant antigens (Ags; 85A, 85B, 85C, superoxide dismutase [SOD], and 35-kDa protein) were purified from Mycobacterium avium subsp. paratuberculosis and evaluated for their ability to stimulate peripheral blood mononuclear cells (PMBCs) from fecal-culture-positive cows (low and medium shedders) and culture-negative healthy cows. Recombinant Ags 85A, 85B, and 85C induced significant lymphocyte proliferation as well as the production of gamma interferon (IFN-gamma), interleukin-2 (IL-2), IL-12, and tumor necrosis factor alpha (TNF-alpha), but not IL-4, from low and medium shedders. The 85 antigen complex did not stimulate PMBC proliferation from culture-negative healthy cows. The 35-kDa protein also induced significant lymphocyte proliferation as well as the production of IFN-gamma and IL-4 from low and medium shedders. CD4(+) T cells and CD25(+) (IL-2R) T cells were stimulated the most by 85A and 85B, while the 35-kDa protein primarily stimulated CD21(+) B cells involved in humoral immune responses. Interestingly, SOD was less immunostimulatory than other antigens but strongly induced gammadelta(+) T cells, which are thought to be important in the early stages of infection, such as pathogen entry. These data provide important insight into how improved vaccines against mycobacterial infections might be constructed.