Liv Jorun Reitan

DNA Injection in Combination with Electroporation: a Novel Method for Vaccination of Farmed Ruminants

Injection of plasmid DNA encoding antigens into rodents followed by electroporation improved the immune response when compared with injection without electroporation (Widera et al. J Immunol 2000;164:4635–40; Zucchelli et al. J Virol 2000;74:11598–607; Kadowaki et al. Vaccine 2000;18:2779–88). The present study describes the extension of this technology to farm animals, by injecting plasmid DNA encoding mycobacterial antigens (MPB70, Ag85B and Hsp65) into the muscles of goats and cattle using two different types of electrodes, both allowing DNA delivery at the site of electroporation. The animals were vaccinated under local anaesthesia without any observed immediate or long‐term distress or discomfort, or any behavioural signs of muscle damage or pathological changes after the electroporation. DNA‐injected and electroporated goats showed increased humoral response after the primary vaccination when compared with nonelectroporated animals. Improved T‐cell responses following electroporation were observed in hsp65 DNA‐vaccinated cattle. DNA injection with or without electroporation did not compromise the specificity of the tuberculin skin test. In conclusion, a protocol applying in vivo electroporation free of side effects to farmed ruminants was established. In addition, we show that DNA vaccination in combination with electroporation can improve the primary immune responses to the encoded antigens.

Isolation of Mycobacterium avium Subspecies paratuberculosis Reactive CD4 T Cells from Intestinal Biopsies of Crohn's Disease Patients

Background Crohns disease (CD) is a chronic granulomatous inflammation of the intestine. The etiology is unknown, but an excessive immune response to bacteria in genetically susceptible individuals is probably involved. The response is characterized by a strong Th1/Th17 response, but the relative importance of the various bacteria is not known. Methodology/Principal Findings In an attempt to address this issue, we made T-cell lines from intestinal biopsies of patients with CD (n = 11), ulcerative colitis (UC) (n = 13) and controls (n = 10). The T-cell lines were tested for responses to various bacteria. A majority of the CD patients with active disease had a dominant response to Mycobacterium avium subspecies paratuberculosis (MAP). The T cells from CD patients also showed higher proliferation in response to MAP compared to UC patients (p<0.025). MAP reactive CD4 T-cell clones (n = 28) were isolated from four CD patients. The T-cell clones produced IL-17 and/or IFN-γ, while minimal amounts of IL-4 were detected. To further characterize the specificity, the responses to antigen preparations from different mycobacterial species were tested. One T-cell clone responded only to MAP and the very closely related M. avium subspecies avium (MAA) while another responded to MAP, MAA and Mycobacterium intracellulare. A more broadly reactive T-cell clone reacted to MAP1508 which belongs to the esx protein family. Conclusions/Significance The presence of MAP reactive T cells with a Th1 or Th1/Th17 phenotype may suggest a possible role of mycobacteria in the inflammation seen in CD. The isolation of intestinal T cells followed by characterization of their specificity is a valuable tool to study the relative importance of different bacteria in CD.

Elevated Antibody Responses in Patients with Crohn's Disease against a 14-kDa Secreted Protein Purified from Mycobacterium avium subsp. paratuberculosis

Patients with Crohns disease (CD) (n = 10) and ulcerative colitis (UC) (n = 10) were tested for immune responses against various antigens from Mycobacterium avium subsp. paratuberculosis; alkyl hydroperoxide reductase C (AhpC) and alkyl hydroperoxide reductase D (AhpD), which are constitutively expressed in this species as opposed to other mycobacteria, a 14‐kDa secreted antigen and PPD‐J. The CD patients had significantly elevated antibody levels against the 14 kDa protein (P < 0.05) that were negatively correlated with the duration of the disease (rs = − 0.85). They also seemed to have increased antibody levels against AhpC and AhpD, but the differences between the two groups were not significant. However, taken together, the antibody responses to three individual mycobacterial antigens in CD patients strengthen the possibility that the observed responses are caused by mycobacterial infection. No significant differences in the interferon (IFN)‐γ production, the interleukin (IL)‐10 production and the ability to proliferate upon stimulation with these antigens were observed. These results show that measuring antibody responses against purified specific antigens is a suitable and simple approach when assessing the connection between CD and mycobacteria in patients with clinical CD. Another important aspect in such studies is to have well defined patient groups tested at the onset of clinical symptoms.

Alkyl hydroperoxide reductases C and D are major antigens constitutively expressed by Mycobacterium avium subsp. paratuberculosis.

ABSTRACT Antigens characteristic for Mycobacterium aviumsubspecies paratuberculosis were identified by crossed immunoelectrophoresis (CIE) and by absorbing out cross-reactive antigens by using a polyclonal and polyvalent Mycobacterium avium subspecies avium antiserum. Two antigens were present in M. avium subsp. paratuberculosis and not detected in Mycobacterium avium subsp.avium. They were identified as antigens 17 and 20 in a CIE reference system for M. avium subsp.paratuberculosis antigens. Purified antigen 20 was identified as alkyl hydroperoxide reductase C (AhpC) while the N-terminal part of purified antigen 17 showed 80% homology with alkyl hydroperoxide reductase D (AhpD) of Mycobacterium tuberculosis. AhpC had a nonreduced mobility in sodium dodecyl sulfate-polyacrylamide gel electrophoresis corresponding to a molecular mass of 45 kDa and is probably a homodimer linked with disulfide bridges in its native form. AhpD had a mobility corresponding to 19 kDa. Monospecific rabbit antiserum against AhpC and AhpD reacted with 9 strains of M. avium subsp. paratuberculosis but not with 20 other mycobacterial strains except for aMycobacterium gordonae strain, against which a weak cross-reactive band was produced. Goats experimentally infected withM. avium subsp. paratuberculosis had strong gamma interferon (IFN-γ) responses toward both AhpC and AhpD, and they also had antibodies against AhpC. The ability of AhpC and AhpD to induce IFN-γ production shows that these proteins potentially could be used in future vaccines or in diagnostic assays. These results further show that AhpC and AhpD are immunologically important proteins which are constitutively and highly expressed in M. aviumsubsp. paratuberculosis without the bacteria being submitted to oxidative stress and that the specificities of antigens can be a matter of different levels of protein expression in various species as well as distinct structural differences.

Immune response and protective immunity after vaccination of Atlantic salmon (Salmo salar L.) against furunculosis

The development of protective immunity in Atlantic salmon ( Salmo salar L.) following intraperitoneal immunisation with an adjuvanted furunculosis vaccine was studied. The level of protection 6 weeks after vaccination was evaluated using cohabitation challenge. Serum antibody levels were measured weekly using an enzyme-linked immunosorbent assay (ELISA) against whole cells of Aeromonas salmonicida subspecies salmonicida , and against lipopoly-saccharide (LPS) and A-layer isolated from A. salmonicida . Six weeks after vaccination head kidney leucocytes were isolated and stimulated with the two mitogens, LPS from Echerichia coli and phytohaemagglutinin (PHA), and also with whole cells of A. salmonicida . Vaccinated fish were found to produce antibodies against all antigens tested, though some individual variation was seen. A significant increase in antibody level to whole cells of A. salmonicida was observed 3–8 weeks after vaccination. The antibody response to A-layer was not significant until 7 weeks after vaccination. Leucocytes from vaccinated fish were found to respond significantly stronger to whole A. salmonicida than did unvaccinated controls, while the responses to mitogens did not differ significantly. Vaccinated fish also showed a higher survival than unvaccinated, the relative percent survival (RPS) 21 days after challenge being 44%.

AhpC, AhpD, and a Secreted 14-Kilodalton Antigen from Mycobacterium avium subsp. paratuberculosis Distinguish between Paratuberculosis and Bovine Tuberculosis in an Enzyme-Linked Immunosorbent Assay

ABSTRACT Sera from cattle naturally infected with Mycobacterium avium subsp. paratuberculosis(n = 56) and naturally (n = 4) and experimentally (n = 8) infected withMycobacterium bovis were tested for the presence of antibodies against paratuberculosis antigens. An enzyme-linked immunosorbent assay (ELISA) was established based on absorption ofM. avium subsp. paratuberculosis antigens on a hyperimmune antiserum against M. avium subsp.avium proteins in order to remove cross-reacting antigens. This absorbed-antigen ELISA recognized 66% of animals with paratuberculosis (37 of 56), while none of the animals with naturally occurring bovine tuberculosis (TB) had detectable antibodies. However, the animals with experimental bovine TB also responded in this ELISA. Similar results were found in a commercial ELISA, showing that neither of these tests was able to distinguish between paratuberculosis and bovine TB. The sera were further tested for antibody activities against purified AhpC and AhpD, which are proteins constitutively expressed byM. avium subsp. paratuberculosis, and against a secreted 14-kDa protein present in culture filtrates from theM. avium complex. Elevated antibody levels to AhpC, AhpD, and the 14-kDa antigen were found in 27% (13 of 48), 15% (7 of 48), and 27% (13 of 48), respectively, of the cattle with paratuberculosis. Together these ELISAs were positive with 35% (17 of 48) of the animals. None of the animals with bovine TB had detectable antibodies against any of the purified proteins despite their high levels of cross-reacting antibodies. These results show that purified specific antigens are needed to differentiate between paratuberculosis and bovine TB in ELISA.

In vitro stimulation of salmonid leucocytes with mitogens and with Aeromonas salmonicida.

Leucocytes from peripheral blood (PBL), spleen and head kidney of Atlantic salmon ( Salmo salar ) and rainbow trout ( Oncorhynchus mykiss ) responded well when stimulated with lipopolysaccharide from Escherichia coli and phytohaemagglutinin (PHA). Thymocytes responded to PHA only. PBL from Atlantic salmon vaccinated against furunculosis showed significantly higher responses as compared to non-vaccinated fish when stimulated with an antigen preparation of whole cells of Aeromonas salmonicida . In leucocyte cultures from rainbow trout vaccinated against furunculosis, specific antibodies to A. salmonicida were produced in vitro . None or very low antibody levels were detected in cultures from non-immunised fish during the first 7 days in culture. After 9 days, a primary antibody response to A. salmonicida could, however, be detected in these cultures. Good correlation ( r =0·88) between antibody production by blood leucocytes and splenocytes was seen.

Diagnosing Clostridium perfringens-associated necrotic enteritis in broiler flocks by an immunoglobulin G anti-alpha-toxin enzyme-linked immunosorbent assay

The tools available for monitoring necrotic enteritis caused by Clostridium perfringens in broiler chickens have been limited, particularly for identifying subclinical disease. In this study, a modified enzyme-linked immunosorbent assay was used to quantify levels of specific immunoglobulin G to C. perfringens alpha-toxin in serum from broilers. We found significantly higher antibody levels in broilers with a history of subclinical necrotic enteritis compared with a zinc-bacitracin-treated group with a low level of gut lesions. Furthermore, in 4.5-week-old commercial broiler flocks, there was an association between the occurrence of C. perfringens-associated hepatitis at slaughter and the immune response to alpha-toxin. Practical solutions for defining cut-off levels for positive serum samples at individual and flock levels are proposed, and were found to be useful on a set of samples available from flocks with different histories regarding the occurrence of C. perfringens-associated disease. This serological approach seems promising as a diagnostic tool in research and disease monitoring regarding C. perfringens-associated disease.

Development of an antibody ELISA for potency testing of furunculosis (Aeromonas salmonicida subsp salmonicida) vaccines in Atlantic salmon (Salmo salar L)

The study was conducted in Atlantic salmon to establish the initial and basic scientific documentation for an alternative batch potency test for salmon furuculosis vaccines. We assessed the antibody response development for Aeromonas salmonicida vaccines at different immunisation temperatures (3, 12 and 18 °C), by an enzyme-linked-immunosorbent assay (ELISA) 3, 6, 9 and 12 weeks post vaccination, and the correlation between antibody response and protection in cohabitation challenge experiments performed 6 and 12 weeks post vaccination. Fish immunised with a vaccine containing full antigen dose had a significant increase in antibody response after 252 day degrees and the measured values correlated well with protection after 500 day degrees. Fish vaccinated with a reduced antigen dose showed a significant lower antibody response than fish vaccinated with the full dose vaccine at all samplings, and showed a similar low relative percent survival (RPS) in the challenges. The results from this study indicate that an antibody ELISA can discriminate between vaccines of different antigen content and the method may replace challenge tests in batch potency testing of furunculosis vaccines in Atlantic salmon. An immunisation temperature of 12 °C and sampling after 6-9 weeks, seemed to be the most appropriate time for using antibody responses to confirm batch potency.

SEROLOGIC SURVEY FOR ANTIBODIES AGAINST MYCOBACTERIUM AVIUM SUBSP. PARATUBERCULOSIS IN FREE-RANGING CERVIDS FROM NORWAY

Affinity between protein-G and immunoglobulins from red deer (Cervus elaphus), moose (Alces alces), roe deer (Capreolus capreolus), and reindeer (Rangifer tarandus tarandus) was tested in a competition binding assay. Sera from red deer, reindeer, and moose inhibited the assay less than sera from cattle (less affinity), whereas sera from roe deer showed a slightly higher affinity to protein-G than did sera from cattle. The conclusion was made that protein-G could be used instead of anti-species antibodies for these cervid species, where the aim of the screening was to look for exposure or lack of exposure to mycobacteria in the tested populations. Serologic screening of 1,373 free-ranging cervids for antibodies against Mycobacterium avium subsp. paratuberculosis was conducted. All sera were tested by a protein-G–based antigen-absorbed enzymelinked immunosorbent assay (ELISA). Seropositive moose (10/537; 1.9%), red deer (14/371; 3.8%), roe deer (6/49; 12.2%), and semidomesticated reindeer (11/325; 3.4%) were found, whereas wild reindeer (n=91) were seronegative. In addition, the red deer sera were tested with a commercial ELISA, by which two animals tested positive and nine were suspicious of having M. avium subsp. paratuberculosis antibodies. Tissue samples and feces from 10 moose originating from a population with a clustering of seropositive animals were investigated by histology and bacteriology with negative results. Paratuberculosis has never been diagnosed in free-ranging or farmed cervid species in Norway. Thus, further studies are indicated to prove that the present findings reflect an infection with M. avium subsp. paratuberculosis.