Heat-killed Streptococcus suis capsular type 2 strains stimulate tumor necrosis factor alpha and interleukin-6 production by murine macrophages

Streptococcus suis capsular type 2 is an important etiological agent of swine meningitis, and it is also a zoonotic agent. Since mononuclear phagocytes have been suggested to play a central role in the pathogenesis of meningitis, the objective of the present study was to evaluate the capacity of whole killed S. suis type 2 organisms to induce the release of the proinflammatory cytokines tumor necrosis factor alpha (TNF-alpha) and interleukin-6 (IL-6) by murine macrophages. Induction of cytokines was evaluated in the presence or absence of phorbol ester (phorbol 12-myristate 13-acetate [PMA]) costimulation. Results showed that S. suis type 2 stimulated the production of both cytokines in a concentration- and time-dependent fashion. Although large doses of bacteria were required for maximal cytokine release, titers were similar to those obtained with the lipopolysaccharide (LPS) positive control. An increase in cytokine release was observed with both S. suis and LPS with PMA costimulation. Experiments with cytochalasin-treated macrophages showed that the stimulation of cytokine production was phagocytosis independent. When macrophages were stimulated with an unencapsulated mutant, an increase in TNF production was observed, but the absence of the capsule had no effect on IL-6 production. In fact, whereas purified capsular polysaccharide of S. suis failed to induce cytokine release, purified S. suis cell wall induced both TNF and, to a lesser extent, IL-6. IL-6 secretion probably requires some distinct stimuli which differ from those of TNF. Finally, the S. suis putative virulence factors suilysin and extracellular protein EF showed no cytokine-stimulating activity. The ability of S. suis to trigger macrophages to produce proinflammatory cytokines may have an important role in the initiation and development of meningitis caused by this microorganism.

Home-based multicomponent rehabilitation program for older persons after hip fracture: a randomized trial

OBJECTIVE

To determine whether a home-based systematic multicomponent rehabilitation strategy leads to improved outcomes relative to usual care.

DESIGN

A randomized controlled trial with 12 months of follow-up.

SETTING

General community; 27 home care agencies.

PARTICIPANTS

Three hundred four nondemented persons at least 65 years of age who underwent surgical repair of a hip fracture at two hospitals in New Haven, CT, and returned home within 100 days.

INTERVENTION

Systematic multicomponent rehabilitation strategy addressing both modifiable physical impairments (physical therapy) and activities of daily living (ADL) disabilities (functional therapy) versus usual care.

MAIN OUTCOME MEASURES

A battery of self-report and performance-based measures of physical and social function.

RESULTS

There was no significant difference in the proportion of participants in the two groups who recovered to prefracture levels in self-care ADL at 6 months (71% vs 75%) or 12 months (74% in both groups) or in home management ADL at 6 months (35% vs 44%) or 12 months (44% vs 48%). There also was no difference between the two groups in social activity levels, two timed mobility tasks, balance, or lower extremity strength at either 6 or 12 months. Compared with participants who received usual care, those in the multicomponent rehabilitation program showed slightly greater upper extremity strength at 6 months (p = .04) and a marginally better gait performance (p = .08).

CONCLUSIONS

The systematic multicomponent rehabilitation program was no more effective in promoting recovery than usual home-based rehabilitation. Compared with previous cohorts, however, participants randomized to usual care in our study received more rehabilitative and home care services and experienced a higher rate of recovery. This finding is important given the current pressures to reduce home services. The challenge is to determine the composition and duration of rehabilitation and home services that will ensure optimal functional recovery most efficiently in older persons after hip fracture.

Genomic relatedness among Actinobacillus pleuropneumoniae field strains of sterotypes 1 and 5 isolated from healthy and diseased pigs

Forty-four Actinobacillus pleuropneumoniae isolates recovered from both healthy and diseased pigs were characterized by random amplified polymorphic DNA analysis (RAPD), pulsed field gel electrophoresis (PFGE) and apx toxin gene typing. Nine RAPD types and 14 PFGE patterns were identified. No common RAPD or PFGE patterns were found between strains of serotype 1 and those of serotype 5. The RAPD analysis indicated that the 15 serotype 1 strains isolated from diseased pigs were assigned to 4 RAPD types, with 66% of strains characterized by the same RAPD type. By contrast, the 5 strains of serotype 1 isolated from healthy carriers were dispersed in 4 RAPD types. These data suggest that the diversity of strains isolated from healthy pigs could be higher than that of strains recovered from diseased pigs. In addition, all serotype 5 strains exhibited a unique RAPD type. Unlike RAPD, PFGE analysis allowed discrimination among isolates of serotype 1 and among those of serotype 5. All but 3 isolates showed the same apx genotype as their respective serotype reference strain. These data indicate that RAPD analysis is a valuable rapid tool for routine subtyping of strains of serotype 1. For strains of serotype 5, a combination of several typing methods, such as PFGE and apx gene typing, is needed to provide useful information on the molecular epidemiology of swine pleuropneumonia.

The missing millions: organized labor, business, and the defeat of Clinton's Health Security Act

During the battle over comprehensive health care reform in the early 1990s, organized labor was not only unable to put together a winning coalition but also found itself divided and on the defensive as it struggled to prevent any further erosion of the private-sector safety net of the U.S. welfare state. Labor's relative ineffectiveness has deep institutional and political roots and was not merely a consequence of its dwindling membership base. Several key institutions of the private welfare state, notably the Taft-Hartley health and welfare funds and the Employment Retirement Income Security Act (ERISA) preemption, brought the interests of organized labor more closely in line with those of large employers and commercial insurers and aggravated divisions within organized labor and between unions and public interest groups. In addition, several political factors conspired to reinforce labor's tendency to stick to a policy path on health care issues that was predicated on an employer-mandate solution and that had been charted primarily by business and leading Democrats. As a result, organized labor did not emerge from the 1993-1994 struggle with its political base fortified nor with a viable long-term political strategy to achieve universal health care and to shift the political debate over health policy in a more desirable direction.

Identification of Actinobacillus pleuropneumoniae strains of serotypes 7 and 4 using monoclonal antibodies: demonstration of common LPS O-chain epitopes with Actinobacillus lignieresii

Monoclonal antibodies (Mabs) against Actinobacillus pleuropneumoniae serotype 7 were produced and characterized. Three Mabs directed against surface polysaccharides were selected. One of the Mabs was directed against a capsular polysaccharide epitope (CPS) of A. pleuropneumoniae serotype 7 whereas two other Mabs reacted with different epitopes of the LPS O-chain. One of the latter reacted with the reference strain of serotype 7 and the other one with serotypes 7 and 4. These three Mabs were used to test, by Dot-ELISA, 508 field strains of A. pleuropneumoniae. None of the strains belonging to other serotypes different from serotypes 4 and 7 were positive with the Mabs. Used in combination, the CPS and one of the LPS O-chain directed Mabs were shown to be suitable for serotyping since they detected 100% of serotype 7 strains. In this study, we confirm for the first time that A. pleuropneumoniae serotype 4 is present in North America. Finally, both O-chain specific Mabs also reacted with the O-chain of Actinobacillus lignieresii. The cross-reactivity between the two species was confirmed using sera from pigs experimentally infected with A. pleuropneumoniae serotype 7 and A. lignieresii, using immunoblotting and ELISA. This is the first report of a specific cross-reactivity between the LPS of these bacterial species.

Relatedness of Streptococcus suis serotype 2 isolates from different geographic origins as evaluated by molecular fingerprinting and phenotyping

The genetic diversity of 88 Streptococcus suis serotype 2 isolates which were recovered from various countries was examined by randomly amplified polymorphic DNA (RAPD) analysis with three primers. This bacterial collection included 80 isolates of porcine origin and 8 of human origin. This investigation allowed the identification of 23 RAPD types containing 1 to 30 isolates originating from one to six countries. Common RAPD patterns were found between human and pig isolates. The isolates were also tested for the production of virulent factors such as hemolysin, muramidase-released protein (MRP), and extracellular factor (EF). All isolates exhibiting the virulent phenotype hemolysin+ MRP+ EF+ clearly clustered on the basis of fingerprinting by RAPD analysis. In a similar way, most of isolates with the hemolysin- MRP- EF- phenotype were assigned to one RAPD cluster. Therefore, RAPD clusters are more related to the phenotype defined with hemolysin, MRP, and EF than to the geographic origin of the isolates. These data indicate that RAPD analysis used in conjunction with phenotypic methods provides a reliable method for the assessment of the clonal relationship between S. suis isolates responsible for infections in pigs or humans, especially for those exhibiting the classic "virulent" phenotype hemolysin+ MRP+ EF+.

Streptococcus suis and group B Streptococcus differ in their interactions with murine macrophages

Streptococcus suis type 2 and group B Streptococcus type III (GBS) are important encapsulated bacterial species causing meningitis. In the present study we compared quantitatively the uptake and intracellular survival of S. suis type 2 and GBS type III with murine macrophages in non-opsonic conditions. The role of the capsule of both pathogens was also studied using previously obtained unencapsulated isogenic mutants. Encapsulated S. suis wild-type strain was practically not phagocytosed, while the unencapsulated mutant was easily ingested by macrophages. On the other hand, the well encapsulated GBS strain and its unencapsulated mutant were both phagocytosed in large numbers. Even if S. suis unencapsulated mutant showed a higher uptake rate than the parental strain, this value was always markedly lower than the numbers of ingested GBS strains. In addition, the intracellular survival of encapsulated and unencapsulated GBS strains was significantly higher than that of S. suis strains. These results suggest that interactions between GBS type III and S. suis type 2 with murine macrophages as well as the role of the capsule as an antiphagocytic factor are different for the two bacterial pathogens.

Phylogenetic diversity of Streptococcus suis strains of various serotypes as revealed by 16S rRNA gene sequence comparison

The 16S rRNA gene sequences of reference strains of Streptococcus suis serotypes 1-34 and 1/2 were determined. A comparative sequence analysis showed that the degree of sequence similarity between S. suis reference strains ranged from 93.94 to 100%. A dendrogram was constructed from the similarity matrix. Thirty-two strains representing 32 serotypes fell into a major group divided into three clusters. The other strains, S. suis serotypes 32, 33 and 34, were more distant. Biochemical characterization of the six more distant strains, including S. suis serotypes 20, 22, 26, 32, 33 and 34, revealed a profile similar to that of other S. suis serotypes. Comparison of the 16S rRNA gene sequences of S. suis reference strains with sequences of other members of the genus Streptococcus indicated that, with the exception of S. suis serotypes 32, 33 and 34, reference strains did not cluster with any other species in the genus. In conclusion, 16S rRNA gene sequence analysis defined a major group of S. suis reference strains which were very closely related and a higher divergence for S. suis serotypes 32, 33 and 34. However, to date, there is no strong evidence to reclassify strains of these serotypes in another species.

Chromosome sizes and phylogenetic relationships between serotypes of Actinobacillus pleuropneumoniae

The genome size of Actinobacillus pleuropneumoniae was determined by pulsed field gel electrophoresis of AscI and ApaI digested chromosomal DNA. The genome size of the type strain 4074T (serotype 1) was determined to be 2404 +/- 40 kb. The chromosome sizes for the reference strains of the other serotypes range between 2.3 and 2.4 Mb. The restriction pattern profiles of AscI, ApaI and NheI digested chromosomes showed a high degree of polymorphism among the different serotype reference strains and allowed their discrimination. The analysis of the macrorestriction pattern polymorphism revealed phylogenetic relationships between the different serotype reference strains which reflect to some extent groups of serotypes known to cross-react serologically. In addition, different pulsed fields gel electrophoresis patterns also revealed heterogeneity in the chromosomal structure among different field strains of serotypes 1, 5a, and 5b, while strains of serotype 9 originating from most distant geographical places showed homogeneous ApaI patterns in pulsed field gel electrophoresis.

Production of virulence-related proteins by Canadian strains of Streptococcus suis capsular type 2

The production of muramidase-released protein (MRP), extracellular protein factor (EF) and hemolysin (suilysin) by 101 Canadian field strains of Streptococcus suis capsular type 2 is described. Most strains (72%) isolated from diseased pigs were MRP-EF- and only 1 strain was MRP+EF+. This strain was also the only 1 to produce the hemolysin. Thirteen strains (15%) were MRP+ EF- and only 3 strains were MRP* EF-. All the strains isolated from clinically healthy pigs as well as a bovine and 2 human isolates had a MRP-EF- phenotype. In addition, 7 strains (8%) had a MRPS phenotype, which had so far been described for S. suis capsular type 1. In conclusion, most Canadian field isolates of S. suis capsular type 2 tested in this study do not produce the virulence-related proteins described so far for this bacterial pathogen.

Development of an immunomagnetic method for selective isolation of Actinobacillus pleuropneumoniae serotype 1 from tonsils

An immunomagnetic separation technique (IMS) for the selective isolation of Actinobacillus pleuropneumoniae serotype 1 was developed. Superparamagnetic polystyrene beads (immunomagnetic beads [IMBs]) were coated with purified rabbit immunoglobulin G specific for A. pleuropneumoniae serotype 1. The antibody concentration, the number of IMBs, the incubation time, and the temperature of incubation influenced the recovery of the target bacteria. The sensitivity of the IMS technique was 1,000-fold higher than that of direct culture. When tonsils from animals from infected herds were tested, significantly more positive tonsils were detected by the IMS technique (68%) than by the standard procedures (22%). The method represents an innovative and highly sensitive approach for the isolation of A. pleuropneumoniae from carrier animals.

Systematic home-based physical and functional therapy for older persons after hip fracture

OBJECTIVE

To describe the development, implementation, and results of a home-based rehabilitation protocol for older persons after hip fracture.

DESIGN

Demonstration study.

SETTING

Community.

PARTICIPANTS

One hundred forty-eight community-living, nondemented participants at least 65 years of age who underwent repair of a fractured hip at two local hospitals.

INTERVENTION

A linked assessment-intervention, home-based rehabilitation strategy. The physical therapy (PT) component of the intervention was designed to identify and ameliorate impairments in balance, strength, transfers, gait, and stair climbing; the functional therapy (FT) component was designed to identify and improve unsafe and/or inefficient performance of specific activities of daily living (ADL).

MAIN OUTCOME MEASURES

The percentage of participants able to complete each component and the extent of progress noted in strength, balance, transfers, gait, and daily functioning.

RESULTS

A total of 104 of the 148 participants (70%) completed the 6-month PT and FT program; 4 completed only PT and 6 refused both PT and FT. The remaining 32 participants (22%) received partial PT and FT that was terminated by death, hospitalization, or institutionalization. Seventy-seven percent of participants reported performing at least half of the recommended daily exercise sessions. Ninety-four percent and 96% of participants progressed in upper and lower extremity conditioning respectively; 33% progressed to the highest level in the graduated resisted exercise program. All participants progressed in the competency-based graded balance program, with 55% progressing to the fifth (most difficult) level. Similarly, the majority progressed in transfer maneuvers, stair climbing, and outdoor gait. One repetition maximum (RM) elbow extension increased from a mean of 5.8 (SD 4.6) pounds at baseline to 7.2 (SD 3.8) pounds at 6mo (t 2.22; p < .02). One RM knee extension increased from 5.8 (SD 5.8) pounds to 10.8 (SD 5.4) pounds (t = 8.06; p < .0001). The number of gait deviations decreased from 2.1 (SD 1.3) to 0.6 (SD 0.9) (p < .0001), while the mean modified Berg Balance Scale Score increased from 13.0 (SD 4.8) to 20.5 (SD 6.8) (t = 16.6; p < .0001). Finally, the Total ADL Score increased from a mean of 48.2 (SD 15.0) to 77.7 (SD 18.8) (t = 17.03; p = .0001).

CONCLUSIONS

This systematic assessment and intervention protocol, targeting impairments and ADL, was feasible, safe, and effective. Protocols such as the one presented should enhance the ability to implement rehabilitation programs for the increasing number of multiply impaired older persons receiving home-based therapy and to document the process and outcomes of this care.

Detection of antibodies against Actinobacillus pleuropneumoniae serotype 5 using an inhibition enzyme immunoassay

An inhibition enzyme immunoassay (EIA) for detection of antibodies against A. pleuropneumoniae serotype 5 (App-5) in pig sera, based on the inhibition of the binding of an App-5 specific monoclonal antibody was established. The monoclonal antibody (MAb 210-F11) was found to be directed against an epitope on the O-chain of App-5 LPS. In the inhibition EIA, highly purified App-5 LPS was used to coat microtitre plates. Serial dilutions of pig sera were added to the plates prior to the addition of the MAb 210-F11. The degree of binding of App-5 antibodies from pig sera was determined as the percentage inhibition of the MAb 210-F11. Pig serum from specific pathogen free (SPF) herds, from experimentally infected animals, and from acutely and chronically infected herds were tested. A serum dilution of 1/30 was found to be optimal, when using 50% inhibition as the discriminating inhibition percentage. No cross-reactivity was observed with serum from pigs infected with other App serotypes or bacteria isolated from the respiratory tract, such as A. suis and H. parasuis. The inhibition EIA will be used for surveillance of App-5 antibodies in SPF and conventional herds.

Serodiagnosis of swine pleuropneumonia due to Actinobacillus pleuropneumoniae serotypes 7 and 4 using long-chain lipopolysaccharides

A saline boiled extract (SBE), capsular polysaccharides (CPS) and long-chain lipopolysaccharides (LC-LPS) of Actinobacillus pleuropneumoniae serotype 7 have been evaluated in ELISA for the serodiagnosis of swine pleuropneumonia caused by this serotype. Mean optical densities (ODs) obtained with the 3 antigens using sera from negative herds as well as from animals experimentally and naturally exposed to A. pleuropneumoniae serotypes 7 or 4 were not statistically different. The positive ELISA reaction with anti-serotype 4 sera was unexpected with the CPS, which are supposed to be serotype-specific; LPS traces present in the CPS appeared to be responsible for this reaction. In addition, sera from animals exposed to A. pleuropneumoniae serotypes 5 or 10 presented cross-reactions with the SBE and the CPS, but not with the LC-LPS. Cross-reactions were mainly due to rough LPS, as shown by immunoblotting. The LC-LPS is easily obtainable and can be used for the detection of antibodies in animals infected with A. pleuropneumoniae serotypes 7 and 4.

Detection of antibodies against Streptococcus suis capsular type 2 using a purified capsular polysaccharide antigen-based indirect ELISA

In the present study a purified capsular polysaccharide antigen-based indirect ELISA (CPS-ELISA) to detect antibodies against Streptococcus suis capsular type 2 was developed and compared with a whole cell antigen-based ELISA (WCA-ELISA). The WCA-ELISA presented a very low specificity when rabbit antisera to other capsular types were tested. Most of these cross-reactions were due to common proteins. The standardized CPS-ELISA gave satisfactory results using a concentration of 0.1 micrograms/well; most cross-reactions decreased significantly, with some exceptions, such as those shared by capsular types 1/2, 12 and 17. These cross-reactions were mainly due to common epitopes present in the capsule, as shown by immunoblotting. In a second experiment, the CPS-ELISA was used to detect antibodies in experimentally infected piglets. Despite the fact that capsular type 2 S. suis could be reisolated from all infected animals during and/or after the trial, antibody titers against a second infection. Sera from piglets experimentally infected were completely protected against a second infection. Sera from piglets experimentally infected with S. suis capsular types 1/2 or 12 presented cross-reactions at low dilutions, confirming data previously obtained with rabbit sera. Finally, sera of animals from herds with clinical signs associated with S. suis capsular type 2 did not present titers significantly different from those of disease free herds. From our results we concluded that the CPS-ELISA developed in this study can not be used as a diagnostic tool to identify infected animals.

Identification of two core types in lipopolysaccharides of Actinobacillus pleuropneumoniae representing serotypes 1 to 12

Lipopolysaccharides (LPS) of Actinobacillus pleuropneumoniae were separated by Tricine-SDS-polyacrylamide gel electrophoresis, which has been shown to improve resolution of low-molecular-mass fast migrating bands. Strains representing the 12 serotypes of A. pleuropneumoniae can be divided in two groups according to the gel mobility of the core - lipid A region of their LPS. The first electromorphic core type (core type I), found in serotypes 1, 6, 9, and 11, had a migration slower than Salmonella typhimurium Ra LPS. The second electromorphic core type (core type II), found in the remaining serotypes (i.e., 2, 3, 4, 5, 7, 8, 10, and 12) had a migration similar to S. typhimurium Ra LPS. Furthermore, we observed that these two core types were antigenically different. Western blot analyses indicated that core - lipid A region of LPS from electromorphic core type I strains reacted when probed with serum from a pig experimentally infected with a core type I strain but not when probed with serum from a pig experimentally infected with a core type II strain. Conversely, core - lipid A region of LPS from electromorphic core type II strains reacted only when probed with serum from a pig experimentally infected with a core type II strain. Our results, based on both electrophoretic mobility and antigenicity, suggest the presence of two LPS core types in A. pleuropneumoniae.

Role of capsular sialic acid in virulence and resistance to phagocytosis of Streptococcus suis capsular type 2

Streptococcus suis capsular type 2 has a capsule rich in sialic acid (NANA). Sialic acid, known to be an antiphagocytic factor for many bacterial species, inhibits the activation of the alternative complement pathway. The role of capsular NANA in virulence, resistance to phagocytosis and intracellular survival of S. suis capsular type 2 was evaluated. In general, a low concentration of NANA was observed for all the S. suis strains tested. In addition, no difference could be found in NANA concentrations between strains of different virulence degrees. Sialic acid concentration increased in the virulent strain 89-1591 and the avirulent strain 90-1330 after in vivo growth with an increased capsular material thickness compared to growth in vitro. No significant difference could be found in the phagocytosis rate by porcine blood monocytes of either strain and strain 89-1591 treated with sialidase or the sialic acid-binding lectin from Sambucus nigra (SNA I). Intracellular survival of strain 89-1591 decreased after treatments with sialidase or lectin, becoming comparable to that of strain 90-1330. Finally, no difference could be seen in virulence using a murine model, even if strain 89-1591 was treated with the enzyme or the lectin. Thus, NANA does not seem to be a critical virulence factor for S. suis capsular type 2.

In vitro phagocytosis and survival of Streptococcus suis capsular type 2 inside murine macrophages

In this study, data on phagocytosis of Streptococcus suis and its survival inside macrophages are presented. Mouse peritoneal macrophages were incubated in the presence of one of five different strains of S. suis capsular type 2: a virulent wild-type strain (1591), a non-capsulated non-virulent mutant strain (M2), a poorly capsulated non-virulent mutant strain (M42), a non-virulent capsulated strain (1330), and the wild-type reference (virulent) strain S735. Opsonized or non-opsonized bacteria were incubated with macrophages in vitro and samples were obtained after 1 and 3 h incubation. Phagocytosis as well as live and dead intracellular organisms were determined by acridine orange and crystal violet staining. After 1 h incubation, non-opsonized virulent and non-virulent capsulated bacteria were poorly phagocytosed (by less than 7% of the macrophages), whereas the non-capsulated non-virulent mutant strain was highly phagocytosed (by more than 68% of the macrophages). The M42 mutant strain was more phagocytosed than the capsulated strains but less than the non-capsulated M2 mutant strain (35%). In contrast, a higher percentage of live bacteria was observed inside macrophages for the capsulated strains (1591 and S735) than for the non- or poorly capsulated mutant strains (M2 and M42). Opsonization of bacteria with rabbit serum or heat-inactivated rabbit serum significantly increased phagocytosis. For every opsonized strain, after 3 h incubation, the percentage of live bacteria within macrophages was considerably lower than the corresponding non-opsonized strains. In conclusion, the capsule of S. suis type 2 appears to act as an important anti-phagocytic factor. However, virulent capsulated non-opsonized strains can be phagocytosed by mouse peritoneal macrophages within which they appear to survive for at least 3 h. Serum factors other than complement increase not only phagocytosis but also intracellular killing of S. suis of both capsulated and non-capsulated strains.

Serotyping of Actinobacillus pleuropneumoniae serotype 5 strains using a monoclonal-based polystyrene agglutination test

A polystyrene agglutination test has been developed for serotyping Actinobacillus pleuropneumoniae serotype 5a and 5b strains. Protein A-coated polystyrene microparticles were sensitized with a murine monoclonal antibody recognizing an epitope on serotype 5 LPS-O chain as shown by SDS-PAGE and Western blotting. A total of 205 A. pleuropneumoniae, strains including all 12 serotype reference strains and 13 strains representing 8 common bacterial species associated with swine or related to A. pleuropneumoniae, were tested by mixing 25 microL of polystyrene reagent with the same volume of a dense suspension of bacterial cells grown for 18 h. All A. pleuropneumoniae strains had been previously serotyped using standard procedures. The polystyrene agglutination test was rapid (less than 3 min) and easy to perform. Overall a very good correlation (97.3%) with the standard techniques was found. The sensitized polystyrene particles were stable for at least 6 mo.

Production and characterization of monoclonal antibodies against Actinobacillus pleuropneumoniae serotype 1

Three monoclonal antibodies (mAbs) against Actinobacillus pleuropneumoniae serotype 1, designated 4.2 A11 B5, 5.1 G8 F10 and 1.5 C5 F4 (IgG3, IgG2b and IgM respectively), were produced and characterized. mAbs 4.2 A11 B5 and 5.1 G8 F10 were directed against different epitopes located in the O chain of the LPS. Both clones also recognized reference strains of A. pleuropneumoniae serotypes 9 and 11. The mAb 1.5 C5 F4 reacted with the reference strain of A. pleuropneumoniae serotype 1, with the encapsulated strain 4045 (but not with its non-capsulated mutant) and with A. pleuropneumoniae serotype 1 purified capsular polysaccharides (CPS). The epitope was sensitive to periodate oxidation, heat-labile, and located in the capsular material of A. pleuropneumoniae serotype 1, as demonstrated by immunoblotting. Treatment of the CPS with 5% ammonium hydroxide eliminated the reaction, which may indicate that the epitope recognized by 1.5 C5 F4 mAb is a O-acetyl containing determinant. When different A. pleuropneumoniae field strains were tested, the percentage of strains recognized by the mAbs varied with the mAb and the test used. Cross-reactions associated with the LPS of some A. pleuropneumoniae serotype 5 field strains could be observed with the 4.2 A11 B5 mAb. Of the three mAbs characterized, 1.5 C5 F4 seemed to be the most suitable for A. pleuropneumoniae serotype 1 detection since it reacted with 99% of serotype 1 field strains and it did not recognize any of the strains belonging to other serotypes.