In silico identification and high throughput screening of antigenic proteins as candidates for a Mannheimia haemolytica vaccine

This study examined the use of comparative genomic analysis for vaccine design against Mannheimia haemolytica, a respiratory pathogen of ruminants. A total of 2,341genes were identified in at least half of the 23 genomes. Of these, a total of 240 were identified to code for N-terminal signal peptides with diverse sub-cellular localizations (78 periplasmic, 52 outer membrane, 15 extracellular, 13 cytoplasmic membrane and 82 unknown) and were examined in an ELISA assay using a coupled-cell free transcription/translation system for protein expressionwith antisera from cattle challenged with serovars 1, 2 or 6 of M. haemolytica. In total, 186 proteins were immunoreactive to at least one sera type and of these, 105 were immunoreactive to all sera screened. The top ten antigens based on immunoreactivity were serine protease Ssa-1 (AC570_10970), an ABC dipeptid transporter substrate-binding protein (AC570_04010), a ribonucleotide reductase (AC570_10780), competence protein ComE (AC570_11510), a filamentous hemagglutinin (AC570_01600), a molybdenum ABC transporter solute-binding protein (AC570_10275), a conserved hypothetical protein (AC570_07570), a porin protein (AC569_05045), an outer membrane assembly protein YeaT (AC570_03060), and an ABC transporter maltose binding protein MalE (AC570_00140). The framework generated from this research can be further applied towards rapid vaccine design against other pathogens involved in complex respiratory infections in cattle.

Cellular and mucosal immune responses in the respiratory tract of Nigerian goats following intranasal administration of inactivated Recombinant Mannheimia hemolytica bacterine

This experiment was conducted to evaluate the cellular and mucosal responses in the respiratory tract of Nigerian goats vaccinated intranasally with recombinant Mannheimia hemolytica bacterine. Twenty one goats were divided into five groups, five goats each in three vaccinated groups while three goats each in two other groups serve as positive and negative control. Group A was vaccinated once; group B was vaccinated twice at one week interval, and group D at twice at two weeks interval. Group C1 were the unvaccinated and challenged, while group C2 were unvaccinated and unchallenged. The bronchoalveolar lavage differential counts and bronchial associated lymphoid tissue (BALT) responses were measured using Giemsa stained thin smear of the cell fraction of the lavage and histomorphometry. ANOVA were employed and significance was at p>0.05. The post-challenge macrophage to neutrophil (M:N) ratio values of group B goats was the highest and the ratio differed from other groups which had much lower M:N values. The exposure in group B resulted in significant increase in number and size of BALTs as well as the number of lymphocytes in BALT than those of the other groups. This study showed that intranasal vaccination of the recombinant Mannheimia hemolytica bacterine twice at a week interval was more efficient in inducing strong mucosal and defensive cellular responses in the respiratory tract.

Identification and expression of a gene encoding an epitope that induces hemagglutination inhibition antibody to Avibacterium paragallinarum serovar A

The aims of this study were the identification, cloning, and expression of a genetic region encoding an epitope that induces hemagglutination inhibition (HI) antibody against Avibacterium paragallinarum serovar A and an evaluation of the recombinant protein for immunogenicity in chickens. Although two monoclonal antibodies (MAbs) with HI activity, designated S24-951 and S7-1716-5C, were generated in this study, no reactive proteins with both MAbs were identified by Western blot analysis. A gene fragment of 5157 bp, designated hpa5. 1, was cloned from genomic DNA, and a recombinant protein expressed by hpa5.1, designated HPA5.1, reacted with both MAbs on dot-blot analysis. HPA5.1 showed no hemagglutinating activity, but significantly absorbed HI antibodies in the chicken immune serum. Analysis using a series of deletion mutants prepared from hpa5.1 indicated that a 4.8 kbp gene in hpa5.1 is essential for the expression epitope recognized by MAb S24-951. In addition, chickens immunized once with HPA5.1 showed a high protection rate with sufficient HI antibody titers against challenge exposure with a virulent strain of A. paragallinarum serovar A strain 221. These results show that hpa5. I1 is responsible for the expression of an epitope that induces HI antibody, and HPA5.1 might be a candidate for the development of a new vaccine against avian infectious coryza caused by A. paragallinarum serovar A.

Production of a d-glycero-d-manno-heptosyltransferase mutant of Mannheimia haemolytica displaying a veterinary pathogen specific conserved LPS structure; development and functionality of antibodies to this LPS structure

Previous structural studies of the lipopolysaccharides from the veterinary pathogens Mannheimia haemolytica (Mh), Actinobacillus pleuropneumoniae (Ap) and Pasteurella multocida (Pm) had identified a conserved inner core oligosaccharide structure that was present in all strains investigated. In order to examine the potential of this inner core structure as a vaccine, a mutagenesis strategy was adopted to interrupt a D-glycero-D-manno-heptosyltransferase gene (losB) of Mh. This gene encodes the enzyme responsible for the addition of a D-glycero-D-manno-heptose residue, the first residue beyond the conserved inner core, and its inactivation exposed the conserved inner core structure as a terminal unit on the mutant LPS molecule. Subsequent analyses confirmed the targeted structure of the mutant LPS had been obtained, and complementation with losB in trans confirmed that the losB gene encodes an alpha-1,6-D-glycero-D-manno-heptosyltransferase. Monoclonal antibodies raised in mice to this LPS structure were found to recognise LPS and whole-cells of the truncated mutant and wild-type Mh. The antibodies were bactericidal against a wild-type Mh strain and were able to passively protect mice in a model of Mh disease. This illustrates that it is possible to raise functional antibodies against the conserved inner core LPS structure.

Recombinant Mannheimia haemolytica serotype 1 outer membrane protein PlpE enhances commercial M. haemolytica vaccine-induced resistance against serotype 6 challenge

Mannheimia haemolytica outer membrane protein PlpE, a major immunogenic outer membrane lipoprotein has identical sequences in serotypes 1 (S1) and S6. Recombinant outer membrane lipoprotein PlpE (rPLpE) from M. haemolytica S1 was added to commercial M. haemolytica S1 vaccines to determine if it would enhance vaccine-induced immunity against heterotypic M. haemolytica S6 challenge. Serum antibody responses to M. haemolytica whole cells, leukotoxin and rPlpE were measured. Experiment 1 consisted of four vaccine groups: controls, 100 microg rPlpE, M. haemolytica Bacterin-Toxoid (One Shot) and M. haemolytica Bacterin-Toxoid + 100 microg rPlpE. Vaccines were given on day 0. On day 21, calves were challenged transthoracically with M. haemolytica S6. Lung lesion scores and percentage lesion reduction were 6.3 +/- 2.0 for controls, 3.6 +/- 2.4 for rPlpE vaccinates (42.9% reduction), 3.4 +/- 1.5 for One Shot-vaccinates (46.0% reduction), and 2.4 +/- 1.4 for One Shot/rPlpE vaccinates (61.9% reduction). Experiment 2 consisted of four vaccine groups: controls, 100 microg rPlpE, M. haemolytica toxoid (Presponse), and M. haemolytica toxoid+100 microg rPlpE. On day 28, calves were challenged transthoracically with M. haemolytica S6. Lung lesion scores and percentage lesion reduction were 8.1 +/- 2.2 for controls, 4.4 +/- 4.7 for the rPlpE vaccinates (45.7% reduction), 4.8 +/- 2.2 for Presponse-vaccinates (40.7% reduction), and 2.0 +/- 1.2 for Presponse/rPlpE vaccinates (75.3% reduction). These results indicate that addition of rPlpE from M. haemolytica S1 can enhance commercial M. haemolytica vaccine-induced resistance against experimental challenge with M. haemolytica S6.

Effects of dietary energy and starch concentrations for newly received feedlot calves: I. Growth performance and health

Crossbred calves (n = 572; initial BW = 186 +/- 27 kg) purchased from northern Texas, Arkansas, and southeast Oklahoma auction markets were delivered to the Willard Sparks Beef Research Center, Stillwater, OK, and used to study the effects of dietary energy and starch concentrations on performance and health of newly received feedlot calves during a 42-d receiving period. On arrival, calves were assigned randomly to one of two dietary energy levels (0.85 or 1.07 Mcal NEg/kg DM) and one of two dietary starch levels (34 or 48% of ME from starch) in a 2 x 2 factorial arrangement of treatments. Cattle were weighed and serum samples were collected on d 0, 7, 14, 28, and 42. Individual animal records of morbidity were kept for all cases of respiratory and other disease. Nasal swabs were collected from each morbid animal and cultured for upper-respiratory pathogens. There were no energy x starch level interactions for performance or health response variables. Daily gain (1.14 kg/d) and gain efficiency (ADG:DMI = 0.179) were not affected by increasing dietary energy or starch concentrations. Calves fed low-energy diets consumed (P < 0.05) more DM. No difference (P = 0.54) was detected in morbidity for calves fed high-energy (62.4% calves treated) compared with low-energy (65.8% calves treated) diets; however, calves fed the high-starch diets had numerically (P = 0.11) greater morbidity than calves fed low-starch diets (68.8 vs. 59.4% calves treated, respectively). There were no energy or starch effects on Mannheimia haemolytica or Pasteurella multocida antibody titers; however, day effects (P < 0.02) occurred. On d 7, 14, and 28, calves had antibody titers for P. multocida that were greater (P < 0.05) than titers on d 0. In addition, calves had greater antibody titers to M. haemolytica on d 7 and 14 than on d 0. Nasal swabs revealed that calves fed the high-energy diets tended (P = 0.06) to have a lower percentage of morbid calves with P. multocida during the first antimicrobial treatment and a lower percentage of Haemophilus somnus isolates during the first (P = 0.01) and second (P = 0.06) antimicrobial treatments than calves fed the low-energy diets. Although animal performance was not influenced, the present data suggest that feeding the high-energy diet decreased the percentage of P. multocida and H. somnus pathogens in calves that received one or more antimicrobial treatments.

Bacterial meningitis and encephalitis in ruminants

The clinical aspects of bacterial meningitis in neonates are described in this article. Specific types of meningitis affecting adult cattle are also described. Other conditions occurring less frequently,such as frontal sinusitis and brain abscess, are discussed.

Immunogenicity of recombinant Mannheimia haemolytica serotype 1 outer membrane protein PlpE and augmentation of a commercial vaccine

Mannheimia haemolytica is the major cause of severe bacterial pneumonia associated with shipping fever in cattle. The gene for M. haemolytica outer membrane protein (OMP) PlpE was cloned into the expression vector pRSETA. The cloned gene was then expressed in BL21(DE3)pLysS and the recombinant PlpE (rPlpE) was purified and used in immunological and vaccination studies. Vaccination of cattle with commercial M. haemolytica vaccines stimulated no significant (P>0.05) antibody responses to rPlpE. Recombinant PlpE in a commercial proprietary adjuvant was highly immunogenic when injected subcutaneously into cattle. Vaccination of cattle with 100 microg of rPlpE markedly enhanced resistance against experimental challenge with virulent M. haemolytica. Addition of 100 microg of rPlpE to a commercial M. haemolytica vaccine, Presponse, significantly enhanced (P<0.05) protection afforded by the vaccine against experimental challenge. Addition of rPlpE to commercial M. haemolytica vaccines could greatly enhance vaccine efficacy.

Effect of intranasal exposure to leukotoxin-deficient Mannheimia haemolytica at the time of arrival at the feedyard on subsequent isolation of M haemolytica from nasal secretions of calves

OBJECTIVE

To determine the effect of intranasal exposure to live leukotoxin (LktA)-deficient Mannheimia haemolytica (MH) at the time of feedyard arrival on nasopharyngeal colonization by wild-type MH in calves.

ANIMALS

200 calves.

PROCEDURE

Calves from Arkansas (AR calves; n = 100; mean body weight, 205 kg) were purchased from an order buyer barn. Calves from New Mexico (NM calves; n = 100; mean body weight, 188 kg) were obtained from a single ranch. Calves were transported to a feedyard, where half of each group was exposed intranasally with LktA-deficient MH at the time of arrival. Calves were observed daily for respiratory tract disease (RTD), and nasal swab specimens were collected periodically to determine nasopharyngeal colonization status with MH. Serum samples were assayed for antibodies to MH.

RESULTS

15 AR calves had nasopharyngeal colonization by wild-type MH at the order buyer barn, whereas none of the NM calves had nasopharyngeal colonization. Intranasal exposure to LktA-deficient MH elicited an increase in serum antibody titers against MH in NM calves, but titers were less in NM calves treated for RTD. Exposure of NM calves to LktA-deficient MH offered protection from nasopharyngeal colonization by wild-type MH.

CONCLUSIONS AND CLINICAL RELEVANCE

Exposure of calves to LktA-deficient MH elicited an increase in serum antibody titers against MH and decreased colonization of the nasopharynx by wild-type MH. Earlier exposure would likely allow an immune response to develop before transportation and offer protection from nasopharyngeal colonization and pneumonia caused by wild-type MH.

Effects of tilmicosin phosphate, administered prior to transport or at time of arrival, and feeding of chlortetracycline, after arrival in a feedlot, on Mannheimia haemolytica in nasal secretions of transported steers

OBJECTIVE

To determine effects of time of administration of tilmicosin and feeding of chlortetracycline on colonization of the nasopharynx of transported cattle by Mannheimia haemolytica (MH).

ANIMALS

454 steers (body weight, 200 kg).

PROCEDURE

3 studies included 4 truckloads of steers assembled and processed in the southeastern United States. For each truckload of steers, a third received tilmicosin before transportation (PRIOR), then all were transported to a feedlot in New Mexico (23 hours). At arrival (day 0), another third received tilmicosin (ARR). The remaining third did not receive tilmicosin (control steers [CTR]). Steers in studies 1 and 2 were housed in a feedlot, and steers in study 3 were housed on wheat pasture. One half of the steers from each group in studies 2 and 3 were fed chlortetracycline on days 5 to 9. Steer with signs of respiratory tract disease were treated. Nasal swab specimens were examined for MH to determine colonization.

RESULTS

PRIOR and ARR steers had a lower incidence of respiratory tract disease and MH colonization than CTR steers, but PRIOR and ARR steers did not differ. Feeding chlortetracycline did not have an effect.

CONCLUSIONS AND CLINICAL RELEVANCE

Tilmicosin can inhibit MH from colonizing the nasopharynx of cattle. Because tilmicosin inhibits the growth of MH in the respiratory tract, medication with tilmicosin prior to transport should reduce the incidence of acute respiratory tract disease during the first week at the feedlot when calves are most susceptible to infectious organisms.