Interleukin-10 regulates the tissue factor activity of monocytes in an in vitro model of bacterial endocarditis

Monocytes are important effector cells in the pathogenesis of bacterial endocarditis since they provide the tissue factor that activates the coagulation system and maintains established vegetations. Monocytes secrete cytokines that can modulate monocyte tissue factor activity (TFA), thereby affecting the formation and maintenance of vegetations. In this study, we show that monocytes cultured for 4 h on a Streptococcus sanguis-infected fibrin matrix mimicking the in vivo vegetational surface express high levels of TFA. This was accompanied by secretion of the proinflammatory cytokines tumor necrosis factor alpha (TNF-alpha), interleukin-1 alpha (IL-1 alpha), and IL-1 beta. After a 24-h incubation period the anti-inflammatory cytokine IL-10 could also be detected. Our data show that, whereas TNF-alpha and IL-1 have a minor role in the induction of TFA by monocytes cultured on a fibrin matrix, TNF-alpha but not IL-1 plays an important role in the induction of IL-10 by these cells. In turn, our data show that IL-10 is an important factor in the downregulation of monocyte TFA. In summary, we conclude that IL-10 is an important factor in the control of monocyte TFA in endocardial vegetations.

Interleukin-10 stimulates Coxiella burnetii replication in human monocytes through tumor necrosis factor down-modulation: role in microbicidal defect of Q fever

Coxiella burnetii, an obligate intracellular bacterium, is the agent of Q fever. The chronic form of the disease is associated with the overproduction of interleukin-10 and deficient C. burnetii killing by monocytes. We hypothesized that the replication of C. burnetii inside monocytes requires a macrophage-deactivating cytokine such as interleukin-10. In the absence of interleukin-10, C. burnetii survived but did not replicate in monocytes. C. burnetii replication (measured 15 days) was induced in interleukin-10-treated monocytes. This effect of interleukin-10 is specific since transforming growth factor beta1 had no effect on bacterial replication. C. burnetii replication involves the down-modulation of tumor necrosis factor (TNF) release. First, interleukin-10 suppressed C. burnetii-stimulated production of TNF. Second, the addition of recombinant TNF to interleukin-10-treated monocytes inhibited bacterial replication. Third, the incubation of infected monocytes with neutralizing anti-TNF antibodies favored C. burnetii replication. On the other hand, deficient C. burnetii killing by monocytes from patients with chronic Q fever involves interleukin-10. Indeed, C. burnetii replication was observed in monocytes from patients with Q fever endocarditis, but not in those from patients with acute Q fever. Bacterial replication was inhibited by neutralizing anti-interleukin-10 antibodies. As monocytes from patients with endocarditis overproduced interleukin-10, the defective bacterial killing is likely related to endogenous interleukin-10. These results suggest that interleukin-10 enables monocytes to support C. burnetii replication and to favor the development of chronic Q fever.

Serological diagnosis of human brucellosis: analysis of seven cases with neurological and cardiological manifestations

Serum Tube Agglutination (STA) test was used as routine test to detect antibrucellar antibodies in diagnosis of brucella infection in sera (n = 75) and CSF (n = 14) from 78 patients with neurological (n = 60) and cardiological (n = 15) complaints in whom brucellosis was suspected, over a period of two and a half years from January, 1997 to July 1999. Seven (neurological-six and cardiac-one) serum samples (9.33%) were positive by STA, while none of the CSFs were positive. STA titres ranged from 1:10 to 1:1280. We report the findings of these seven cases with neurological and cardiac manifestations in whom STA were found positive. Treatment was accomplished in two cases (neurological-one and cardiac-one), while remaining five cases either were treated empirically with antitubercular treatment or lost for follow up. However these reported cases should alert clinicians to investigate for Brucella infection in cases of pyrexia of unknown origin and this condition in cases of chronic meningitis with unproven aetiology.

Immunologic evaluation in infective endocarditis

OBJECTIVE

To analyze the immune response in peripheral blood of patients with infective endocarditis.

METHODS

We studied 10 patients with infective endocarditis, age range from 20 to 50 years-old, males and females, and 20 healthy subjects in the same age range. The diagnosis of the disease was based on the clinical picture, echocardiogram, and hemoculture based upon samples drawn and tested before the treatment started. The were no history of atopy or malnutrition, no autoimmune disease, and they were not using any immunosuppressant or antibiotic medication.

RESULTS

The patients with endocarditis had significantly higher T and B lymphocyte, CD4+ and CD8+ cell counts, IgM and IgG serum levels, and C4 component of the complement than the control group; no significant difference concerning serum IgA and neutrophil oxidative metabolism; a significant decrease in C3, chemotaxis, and monocyte phagocytosis;cryoglobulins were detected in 66.6% of patients and they were formed by IgG, IgM, IgA, C3, and C4.

CONCLUSION

The patients with infective endocarditis were immunocompetent in most sectors of immune response and, at a certain moment, an autoimmune component may be present.

Identification of a novel antigen from Staphylococcus epidermidis

A genomic DNA library of Staphylococcus epidermidis NCTC 11047 was constructed, using the Lambda Zap Express cloning vector, and screened with serum collected from a patient with S. epidermidis endocarditis. Sequence analysis of a 30 kDa cloned protein, termed staphylococcal secretory antigen, SsaA, identified a novel protein not previously reported in S. epidermidis. SsaA showed strong homology with two other staphylococcal proteins: SceB from Staphylococcus carnosus and a staphyloxanthin biosynthesis protein from Staphylococcus aureus. Further investigation revealed SsaA to be a highly antigenic protein that was expressed in vivo and could be recovered from whole cells and from the culture supernatant. A combination of Western blot analysis and PCR screening identified SsaA or a homologue in 103/103 staphylococcal strains. SsaA-like genes were not detected in other Gram-positive bacteria of medical importance or a number of Gram-negative organisms. Elevated anti-SsaA IgG antibody levels were detected in sera of five patients with S. epidermidis endocarditis but not in patients with other S. epidermidis infections, endocarditis of other aetiologies or patients with no evidence of infection. The expression of SsaA during episodes of S. epidermidis endocarditis suggests a virulence role specific to the pathogenesis of this infectious disease.

[Correction of secondary immunodeficiency as a method of prevention of suppurative-septic complications after surgery with artificial blood circulation]

Eighty-five patients with acquired heart diseases with and without infective endocarditis (IE) were examined. In one group of patients traditional therapy was supplemented by the Russian drug immunofan, a synthetic hexapeptide with immunomodulating, antiinflammatory, and detoxifying effects. A course consisted of 10 intramuscular injections every other day (1 ml of 0.005% solution). The drug was prescribed after immunological studies on a laser flow cytometer (Becton Dickinson, USA). Correction was carried out before and after the operation. The postoperative period was uneventful in patients treated with immunofan; the incidence of clinical manifestations of IE was decreased. The concentrations of cytokines (IL-1, IL-6, TNF-alpha) in the blood were increased in patients with IE. In patients treated with immunofan, the concentrations of cytokines were decreased and immune parameters were normalized. Changes in the cytokine status can be used as a laboratory test for evaluating the efficiency of treatment in cardiosurgical patients with IE.

[Glucocorticosteroids in bacterial endocarditis: is it beneficial or harmful?]

AIM

Analysis of results of treatment of infectious endocarditis (IE) with glucocorticosteroids in combination with antibiotics.

MATERIAL AND METHODS

128 IE patients received antibiotics (control group). Glucocorticosteroids were added to antibiotics in 44 IE patients (study group).

RESULTS

Valvular replacement, congestive heart insufficiency, thromboembolic complications, suppression of cellular and humoral immunity occurred more frequently in patients of the study group.

CONCLUSION

It was found that glucocorticosteroids affect IE negatively, especially in the dose 30 mg/day and higher. Glucocorticosteroids are indicated in allergic reactions to the antibacterial drugs, severe renal damage (proteinuria < 1 g/l), myocardial defects; contraindicated in non-eradicated IE causative agent, in recurrent IE.

Kingella endocarditis and meningitis in a patient with SLE and associated antiphospholipid syndrome

We describe a patient with SLE and antiphospholipid syndrome who presented with severe headache and fever. Lumbar puncture analyses indicated meningitis. Kingella kingae was isolated from her blood cultures. A large mobile vegetation was seen on her mitral valve. The association between SLE, Libman-Sacks endocarditis and bacterial endocarditis is discussed.

[Impediment of cellular immune response under treatment with ticlopidine in a patient with Staphylococcus aureus endocarditis]

A 52-year-old male with coronary artery disease was admitted with acute aortic valve endocarditis and a temperature up to 39.5 degrees C caused by Staphylococcus aureus. The patient was treated with ticlopidine (Tiklyd) after percutaneous transluminal coronary angioplasties to reduce restenosis by inhibiting thrombocyte aggregation. Upon admission c-reactive protein (CRP) was 389 mg/l. Interleukin-6 (IL-6) and Interleukin-2-receptor (IL-2-rec) were distinctly increased. Monoclonal antimyocardial antibodies were found. Leukocyte count never exceeded 9.8 G/l; however, transesophageal echocardiography validated a soft vegetation of the aortic valve. Antibiotic therapy was initiated with imipenem, gentamicin and vancomycin; clarithromycin was added after five days. Temperature normalized after 24 days. The c-reactive protein decreased from 389 mg/l to 6 mg/l, and the elevated cytokine levels decreased accordingly. Agranulocytosis or pancytopenia by ticlopidine through a toxic mechanism have been described, which are normally reversible within three weeks; there has not yet been a description of a missing leukocyte response in endocarditis as in this case report. This is a special situation with lack of or impeded immunological response, which limits the use of ticlopidine, especially since a therapeutic alternative with clopidogrel is available.

Role of monocytes in experimental Staphylococcus aureus endocarditis

In the pathogenesis of bacterial endocarditis (BE), the clotting system plays a cardinal role in the formation and maintenance of the endocardial vegetations. The extrinsic pathway is involved in the activation of the coagulation pathway with tissue factor (TF) as the key protein. Staphylococcus aureus is a frequently isolated bacterium from patients with BE. We therefore investigated whether S. aureus can induce TF activity (TFA) on fibrin-adherent monocytes, used as an in vitro model of BE. We also assessed in vivo in rabbits with catheter induced vegetations, the effect of S. aureus infection on vegetational TFA. In vitro experiments showed that adherent S. aureus induced TFA on fibrin-adherent monocytes which was optimal at a bacterium/monocyte ratio of 1 to 1. Monocyte damage occurred when this ratio exceeded 4 to 1 (visually) or 6 to 1 (propidium iodide influx) Consequently, TFA decreased. In vivo S. aureus led to very high bacterial numbers in the vegetations and a significant increase of their weight. However, TFA of infected vegetations was the same as of sterile ones. This may be due to the high bacteria to monocyte ratio as well as bacterium-induced monocyte damage. Teicoplanin treatment of infected rabbits reduced bacterial numbers in the blood and in the vegetations. Two-day treatment resulted in an increase of vegetational TFA, but after four-day treatment vegetational TFA dropped, most probably due to a suboptimal bacterium/monocyte ratio. S. aureus endocarditis in etoposide (Vepesid)-treated rabbits, leading to a selective monocytopenia, caused a rapid death of the animals. In these rabbits no vegetations were found at all. We conclude that, like Streptococcus sanguis and Staphylococcus epidermidis, S. aureus is able to induce TFA in fibrin-adherent blood monocytes. In addition, monocytes have a protective effect during the course of S. aureus endocarditis.

The 75-kD tumour necrosis factor (TNF) receptor is specifically up-regulated in monocytes during Q fever endocarditis

Q fever is an infectious disease caused by Coxiella burnetii, an obligate intracellular microorganism that inhabits monocytes/macrophages. The dysregulated production of TNF-alpha in Q fever endocarditis has been associated with defective killing of C. burnetii by patient monocytes. As soluble receptors for TNF-alpha (TNF-R55 and TNF-R75) regulate TNF-alpha activity, we investigated their release by monocytes in Q fever. Spontaneous and C. burnetii-stimulated release of TNF-R75, but not of TNF-R55, was up-regulated in patients with ongoing endocarditis compared with controls. The increase in TNF-R75 release was related to the activity of Q fever endocarditis, since TNF-R75 release was similar in patients with cured endocarditis and controls. While spontaneous release of TNF-R75 by monocytes from patients with ongoing Q fever endocarditis occurred without changes in its membrane expression, C. burnetii increased the surface expression of TNF-R75. In addition, TNF-R75 transcripts were increased in resting and C. burnetii-stimulated monocytes from patients with ongoing endocarditis. On the other hand, TNF-R75 release was not related to TNF-alpha secretion. These results indicate that the modulation of TNF-R75 is a critical feature of the pathophysiology of Q fever endocarditis.

IgA antineutrophil cytoplasmic antibodies in cutaneous vasculitis

BACKGROUND

Antineutrophil cytoplasmic antibodies (ANCA) of the IgA isotype have, for the most part, been detected in patients with Henoch-Schönlein purpura (HSP) or inflammatory bowel disease.

OBJECTIVES

We have evaluated the prevalence of IgA ANCA in a series of patients with different causes of cutaneous vasculitis.

METHODS

Forty consecutive patients with histologically proven leucocytoclastic vasculitis were included in the study: 18 had systemic vasculitis as well as cutaneous lesions, 10 of whom were diagnosed as having HSP, and 22 had only cutaneous vasculitis (with no identified cause in 10 cases). IgA ANCA were sought by indirect immunofluorescence using ethanol-fixed human neutrophil preparations as the substrate.

RESULTS

IgA ANCA were detected in six of 40 patients (15%) (one each with HSP, ulcerative colitis, Sjögren's syndrome, hypergammaglobulinaemia associated with Castelman's disease, erythema elevatum diutinum and bacterial endocarditis). Three of these patients also had IgG ANCA whose target antigen remained unidentified.

CONCLUSIONS

IgA ANCA are rarely observed in HSP (10%) and can be detected in a wide variety of other cutaneous vasculitides.

Coxiella burnetii survives in monocytes from patients with Q fever endocarditis: involvement of tumor necrosis factor

Endocarditis is the most frequent form of chronic Q fever, an infectious disease caused by Coxiella burnetii. As this obligate intracellular bacterium inhabits monocytes and macrophages, we wondered if pathogenesis of Q fever endocarditis is related to defective intracellular killing of C. burnetii by monocytes. Monocytes from healthy controls eliminated virulent C. burnetii within 3 days. In contrast, monocytes from patients with ongoing Q fever endocarditis were unable to eliminate bacteria even after 6 days. In patients who were cured of endocarditis, the monocyte infection was close to that of control monocytes. This killing deficiency was not the consequence of generalized functional impairment, since patient monocytes eliminated avirulent C. burnetii as did control cells. The addition of supernatants of C. burnetii-stimulated monocytes from patients with ongoing endocarditis to control monocytes enabled them to support C. burnetii survival, suggesting that some soluble factor is responsible for bacterial survival. This factor was related to tumor necrosis factor (TNF): expression of TNF mRNA and TNF release were increased in response to C. burnetii in patients with ongoing endocarditis compared to cured patients and healthy controls. In addition, neutralizing anti-TNF antibodies decreased C. burnetii internalization, an early step of bacterial killing, in monocytes from patients with ongoing endocarditis but did not affect delayed steps of intracellular killing. We suggest that Q fever-associated activation of monocytes allows the survival of C. burnetii by modulating early phases of microbial killing.

Effects of intranasal challenge with group A beta haemolytic streptococcus M type 49 in Swiss albino mice

Mice are susceptible to natural infections with streptococci and therefore can serve as suitable animal models to study experimental streptococcal infections. In an earlier study, we had shown the development of pharyngeal colonization, antibody response and histopathological changes in the heart following intranasal (IN) challenge with a rheumatogenic serotype of group A beta haemolytic streptococcus, the M type 18. To determine if nonpharyngitis associated serotypes can also elicit similar responses, 30 Swiss albino mice were challenged intranasally with 2 x 10(7) colony forming units of a skin associated serotype of group A beta haemolytic streptococcus, the M type 49. Pharyngeal colonization varied from 64% (n = 30) in the first week to 69% (n = 16) during the fourth week after IN challenge. Eleven (36.7%) of the 30 animals studied showed antibody response to DNase B (ADNB) with peak titers varying from 150 to 1200 units. Wide variations were seen in ADNB titers in individual mice. Histopathological evidence for cardiac lesions were seen in three animals. The changes were mild and varied from mild to chronic endocardial inflammation to calcification. The study shows that Swiss albino mice are also susceptible to IN challenge with skin associated strains of GABHS and therefore can serve as useful models to study the effects of experimental infection with diverse serotypes of GABHS.

Increased endothelial cell expression of alpha3beta1 integrin in cardiac valvulopathy in the primary (Hughes) and secondary antiphospholipid syndrome

The objective of this work was to determine markers of endothelial cell activation in valves from patients with antiphospholipid syndrome (APS) and heart valve involvement, in order to establish a role for endothelial cells in the pathogenesis of the valvular disease. Sixteen valves from ten patients with APS, obtained from autopsies or removed during valve replacement, were studied. Two groups of valves were used as controls. One group included seven normal valves from patients who died from non-cardiac diseases. The other group of valves were obtained from patients with bacterial endocarditis during autopsies or valve replacement operations. Immunoperoxidase and immunofluorescence stainings with antibodies to human immunoglobulins, endothelial cells, alpha3beta1 integrin, collagen IV, laminin and fibronectin were employed. Three histopathological patterns were apparent: normal valves, valves with verrucous endocarditis and valves with fibrocalcific changes. In all the valves with verrucous endocarditis the following findings were observed: (1) increased expression of the alpha3beta1 integrin on the endothelial cells, (2) increased amount of collagen IV, laminin and fibronectin, (3) proliferation of blood vessels and (4) linear subendothelial deposition of immunoglobulins and complement. The valves with fibrocalcific changes were deformed and showed a thick layer of collagen IV, laminin and fibronectin, yet in two valves the indothelial cells showed an expression of the alpha3beta1 integrin. The control valves did not express the integrin and had only a thin subendothelial band of collagen IV. In valves from patients with APS, 1 markers of endothelial cell activation are upregulated while the inflammatory exudate is scant. There is also a prominent deposition of immunoglobulins in the valves from patients with APS, suggesting a possible association between the deposition of the antibodies and the activation of the endothelial cells in APS.

[The formation of autoimmune complexes as an index of bioincompatibility in reconstructive heart operations]

The manifestation of bioincompatibility in the shape of complement-dependent changes: solubilisation and inhibition--of immune complexed formation was investigated in patients at the prosthetic cardiac operations with using artificial blood circulation, artificial cardiac valves and heterotopic vascular grafts. It was established, that the solubilisation of the precipitate, preformed by plasmic fibrinogen with antifibrinogenic immunoglobulin, and inhibition of hemagglutinating activity of normal autoantibodies in plasma appeared in several minutes after the contact of alien mains with own blood circulation system. These changes of formation of immune complexes in plasma, caused by complement activation, had a selective and reversible nature and were followed breaches of blood circulation. Estimation of early, functional indexes of bioincompatibility, displaying by changes of immune complex formation, may be helpful in prognostic relation in patients with immunocomplex diseases at prosthetic cardiac operations.

[Infectious endocarditis: immune disorders, differentiated therapy]

AIM

Immunological assessment of variants of infectious endocarditis (IE) and design of differentiated approach to the disease therapy.

MATERIALS AND METHODS

Of 150 patients treated (90 males and 60 females, mean age 41.9 +/- 3.3 years) 28.7% and 71.3% had primary and secondary endocarditis, respectively. With chronization of the process, there was a trend to growing immune unbalance (IU).

RESULTS

The IU in IE patients manifested with leukocytosis changing for leukopenia, reduced absolute and relative number of lymphocytes, complement, T- and B-lymphocytes, growing content of CIC, IgM, rheumatoid factor and cryoproteins.

CONCLUSION

Besides antibacterial therapy, IE patients need immunocorrective and efferent therapy.

The presence of infection-related antiphospholipid antibodies in infective endocarditis determines a major risk factor for embolic events

OBJECTIVES

The impact of infection-associated antiphospholipid antibodies (APA) on endothelial cell activation, blood coagulation and fibrinolysis was evaluated in patients with infective endocarditis with and without major embolic events.

BACKGROUND

An embolic event is a common and severe complication of infective endocarditis. Despite the fact that APAs are known to be associated with infectious diseases, their pathogenic role in infective endocarditis has not been clearly defined.

METHODS

The relationship among the occurrence of major embolic events, echocardiographic vegetation size, endothelial cell activation, thrombin generation, fibrinolysis and APA was examined in 91 patients with definite infective endocarditis, including 26 patients with embolic events and 65 control subjects without embolic events.

RESULTS

Overall, 14.3% of patients exhibited elevated APA levels. Embolic events occurred more frequently in patients with elevated levels of APA than in patients without (61.5% vs. 23.1%; p = 0.008). Patients with elevated levels of APA showed higher levels of prothrombin-fragment F1 +2 (p = 0.005), plasminogen-activator inhibitor 1 (p = 0.0002), von Willebrand factor (p = 0.002) and lower levels of activated protein C (p = 0.001) than patients with normal levels of APA. Thrombin generation and endothelial cell activation were both positively correlated with levels of APA. The occurrence of elevated APA levels was frequently associated with structural valve abnormalities (p = 0.01) and vegetations >1.3 cm (p = 0.002).

CONCLUSIONS

Infection-associated elevated APA levels in patients with infective endocarditis are related to endothelial cell activation, thrombin generation and impairment of fibrinolysis. This may contribute to the increased risk for major embolic events in these patients.

[Systemic manifestations and development of GPIIbIIIa antibodies in the course of staphylococcal endocarditis. Report of a case]

Immunological complications of staphylococcal endocarditis are rare but represent a serious event in this condition. The authors report the case of acute tricuspid valve endocarditis in a 38 year old drug addict. The diagnosis was suggested by the presentation of bilateral bacterial lung abscesses with a murmur of tricuspid regurgitation, and confirmed by transthoracic and transoesophageal echocardiography. Bacteriological cultures isolated a methicillin-sensitive staphylococcal aureus. The outcome was complicated by a nephrotic syndrome associated with a glomerulonephritis by deposition of immune complexes and an autoimmune thrombocytopaenic purpura due to acquired anti-glycoprotein IIb IIIa antibodies. Antibiotic therapy led to cure without sequellae of the endocarditis, the nephrotic syndrome and the thrombocytopaenia. This case illustrates the risk of immunological complications during acute staphylococcal tricuspid valve endocarditis and also illustrates the possibility of a favourable outcome with antibiotic therapy alone. However, the potential severity of these complications indicates the need for early diagnosis and strict surveillance of this condition.

[The early diagnosis of postoperative infectious complications in heart surgery patients]

Great surgical aggression in operations on the heart and resulting immunodeficiency create prerequisites for the appearance and grave course of infectious complications. The authors have analyzed results of operative treatment of 100 patients with acquired valvular diseases. It has been established that low parameters of the resistance index of organism (RIO) before operation can be estimated as an unfavourable prognostic sign of the development of infectious complications. The RIO dynamics at the postoperative period in many aspects reflects the character of its course. RIO and the indices of the adaptation reaction show the degree of intoxication, make the clinical estimation objective, allow the assessment of efficiency of therapy and correction of medical prescriptions.

The immunocompromised host and risk for cardiovascular infection

The risk factors for cardiovascular (CV) infections are related to the immunocompetence of the host, preexisting cardiac conditions, and exposure to infectious organisms. Immunocompromised states are related to defective physical and chemical barriers and/or alterations of immune organs, cells, and substances. There are many conditions, diseases, drugs, and therapies that are associated with immunocompromised states. In-dwelling central venous catheters, prosthetic valves/devices, cardiac lesions, and conditions that create turbulent blood flow increase risk for CV infections. An understanding of the immune response, risk factors for immunocompromise, and risk factors for CV infections helps guide the CV nurse's plan of care related to assessment and interventions for prevention, identification, and treatment of CV infections. Diagnosis, monitoring, and management challenges of the immunocompromised patient with infective endocarditis and myocarditis are presented.

Influence of human immunodeficiency virus 1 infection and degree of immunosuppression in the clinical characteristics and outcome of infective endocarditis in intravenous drug users

BACKGROUND

Immunosuppression caused by human immunodeficiency virus 1 (HIV) infection appears to modify the clinical characteristics and to increase the severity of several bacterial infections. The impact of HIV infection and the degree of immunosuppression on the clinical characteristics and outcome of infective endocarditis (IE) in intravenous (IV) drug users has not been well characterized.

METHODS

Prospective cohort study among 292 consecutive IV drug users with IE diagnosed in 2 academic institutional hospitals in Barcelona, Spain, from January 1, 1984, to October 31, 1995. Serostatus of HIV infection was documented in 283 patients. We measured demographics, clinical and biological data, cause, echocardiographic findings, HIV serostatus and classification, CD4 cell count, complications, and mortality.

RESULTS

Among the 283 episodes of IE, 216 (76.3%) were in HIV-infected patients and 67 (23.7%) in non-HIV-infected patients. Rate of IE per 1000 admissions ranged from 0.17 to 0.82 per year, peaking in 1989. Characteristics of IE independently associated with HIV infection were right-side involvement (odds ratio [OR], 7.6; 95% confidence interval [CI], 3.5-16.7), a micro-organism different from viridans streptococci (OR, 2.5; 95% CI, 1.1-5.9), duration of drug abuse longer than 5 years (OR, 5.0; 95% CI, 2.4-10.3), and white blood cell count of no more than 10 X 10(9)/L (OR, 2.2; 95% CI, 1.1-4.2). There were no significant differences in mortality due to IE according to HIV serostatus. Among the 216 patients with HIV infection, the variables independently associated with worse outcome were CD4 cell count lower than 0.200 x 10(9)/L and left-sided or mixed IE.

CONCLUSIONS

Although there is a difference in clinical presentation in IE in IV drug users, outcome was similar according to their HIV status. However, among HIV-infected patients, severe immunosuppression and mixed or left-side valvular involvement were strong risk factors for mortality.

Serological diagnosis of experimental Enterococcus faecalis endocarditis

A modified rat model of endocarditis with catheterization for 2 days was established in female Lewis rats using different inocula of Enterococcus faecalis (strain no. EF 19) in order to measure IgG antibodies in serum during the course of infection. Increasing the inocula intravenously resulted in an increase in the CFU/g vegetation and the CFU/g spleen, the ID50 being about 10 CFU/ml and the ID90 about 1x10(2) CFU/ml. The lowest bacterial inoculum infecting 100% of the rats was 3x10(3) CFU/ml, and for further investigations we used this inoculum size. Rats were sacrificed on day 2, 5, 7, 9, 11 and 28 after infection. The CFU/g vegetation and the CFU/g spleen increased until day 7 and then decreased. Serum samples were collected from 129 rats at different times after challenge. Three different ELISA systems were established to measure the IgG antibody responses: E. faecalis sonicate ELISA (a pool of four sonicates of strain no. EF 10, EF 11, EF 19 and EF 48), E. faecalis whole cell ELISA (strain no. EF 19) and E. faecalis purified cell wall ELISA (strain no. EF 19). An IgG antibody response was detected already on day 2, and except for a minor decrease on day 6/7 the antibody response continued to increase until day 14 (whole cell ELISA and sonicate ELISA) and day 21 (purified cell wall ELISA) when a plateau was reached. Significant increases in IgG antibody responses (p<0.05) were found between groups of rats from days 0-2, 2-8/9 and 8/9-14 in the E. faecalis whole cell and sonicate ELISAs and from days 0-2, 2-10/11 and 10/11-21 in the E. faecalis purified cell wall ELISA. In conclusion, we established a model of endocarditis in rats with catheterization for 2 days and were able to demonstrate an increase in IgG antibodies during the course of infection.

Molecular analysis of polyreactive monoclonal antibodies from rheumatic carditis: human anti-N-acetylglucosamine/anti-myosin antibody V region genes

Anti-myosin Abs are associated with inflammatory heart diseases such as rheumatic carditis and myocarditis. In this study, human cross-reactive anti-streptococcal/anti-myosin mAbs 1.C8, 1.H9, 5.G3, and 3.B6, produced from peripheral blood lymphocytes of patients with rheumatic carditis, and mAb 10.2.5, produced from a tonsil, were characterized, and the nucleotide sequences of their V(H) and V(H)L genes were analyzed. Human mAbs 1.C8, 1.H9, 10.2.5, and 3.B6 reacted with human cardiac myosin while mAb 5.G3 did not. The mAbs were strongly reactive with N-acetyl-beta-D-glucosamine, the dominant epitope of the group A streptococcal carbohydrate. mAb 1.H9 was moderately cytotoxic to rat heart cells in vitro in the presence of complement. The anti-myosin mAbs from rheumatic carditis were found to react with specific peptides from the light meromyosin region of the human cardiac myosin molecule. Anti-streptococcal/anti-myosin mAbs from normal individuals reacted with distinctly different light meromyosin peptides. The mAbs were encoded by V(H)3 gene segments V3-8, V3-23, and V3-30 and by the V(H)4 gene segment V4-59. The variable region genes encoding the anti-streptococcal/anti-myosin repertoire were heterogeneous and exhibited little evidence of Ag-driven somatic mutation.

Endocarditis as the first presentation of AIDS in infancy

A two month old Ugandan boy underwent surgery for an obstructive right ventricular vegetation associated with disseminated Staphylococcus aureus infection. Both the child and his mother subsequently tested positive for HIV infection. Very little is know about the incidence of endocarditis in paediatric patients with AIDS. To our knowledge this is the first case reported of disseminated S aureus infection associated with endocarditis and an obstructing vegetation in an HIV positive infant with a structurally normal heart. The initial signs and symptoms for endocarditis were atypical, a reflection of the overwhelming infection in an immunocompromised patient. Severe infections may have an atypical presentation in immunosuppressed patients. AIDS needs to be considered in these patients, especially if they come from populations with endemic HIV infection.

[Etiopathogenesis of infective endocarditis: predisposing heart diseases and causal microorganisms]

Infective endocarditis is caused by the infection of an amorphous mass of platelets and fibrin (the so-called nonbacterial thrombotic endocarditis) which involves a damaged endothelial surface of the heart. Several pathogenetic mechanisms (hemodynamic, immunological, microbiological, etc.) are needed for the development of endocarditis. We review some of these mechanisms, as well as possible changes in etiopathogenesis of this disease that have recently occurred.

Distribution of IgA subclass response to Coxiella burnetii in patients with acute and chronic Q fever

The progression of Coxiella burnetii infection to acute or chronic Q fever has been attributed to biological characteristics of the bacterium and to the host immune response. We measured whether serum levels of total and specific subclasses IgA1 and IgA2 could be correlated with the course of disease in acute and chronic Q fever infections, and with the occurrence of endocarditis. In patients with chronic infection, total IgA2 levels were significantly increased. Q-fever-specific IgA1 antibodies were detectable in both acute and chronic infections, but only patients with endocarditis had IgA2 antibodies to C. burnetii phase II antigens. These findings indicate that the measurement of IgA subclasses may be a useful aid in the serological diagnosis of Q fever. Our results reinforce the idea that immunologically mediated host factors are important in the pathogenesis of Q fever and in the disease outcome of this infection.

A guinea pig model for Q fever endocarditis

A new model of experimental endocarditis, using electrocoagulation of native aortic valves, was used for the study of Q fever endocarditis. In the 20 guinea pigs electrocoagulated and inoculated with Coxiella burnetii Nine Mile phase I strain, 10 presented with infective endocarditis. Of these, 7 died spontaneously. All guinea pigs with endocarditis presented with blood cultures positive for C. burnetii, and C. burnetii antigen was found in their cardiac valves. Positive blood cultures or valvular immunopositive cells were not identified in either nonelectrocoagulated or noninoculated controls. This experimental model demonstrates that Q fever in an animal with previously damaged valves results in endocarditis. It could provide a new tool for the investigation of pathophysiology and antibiotic therapy for Q fever endocarditis.

In vitro resistance to thrombin-induced platelet microbicidal protein is associated with enhanced progression and hematogenous dissemination in experimental Staphylococcus aureus infective endocarditis

We examined the influence of thrombin-induced platelet microbicidal protein 1 (tPMP-1) on the progression and hematogenous dissemination of experimental endocarditis caused by isogenic Staphylococcus aureus strains differing in tPMP susceptibility (tPMPs) or resistance (tPMPr) in vitro. Following simultaneous challenge of animals with both strains, significantly higher tPMPr bacterial densities were present in vegetations (P < 0.0001), kidneys (P < 0. 0001), and spleens (P < 0.0001) compared with those for the tPMPs strain. These data indicate that tPMP-1 limits the intravegetation proliferation and hematogenous dissemination of a tPMPs strain in experimental endocarditis, while the tPMPr phenotype confers a selective advantage associated with the enhanced progression of this infection.

Jarisch-Herxheimer reaction complicating the treatment of chronic Q fever endocarditis: elevated TNFalpha and IL-6 serum levels

Jarisch-Herxheimer reaction (J-HR) is an acute febrile reaction which may complicate the initiation of an effective treatment against infections due to intracellular micro-organisms. We report a case of J-HR complicating treatment of chronic Q fever endocarditis with demonstration of elevated serum cytokine concentrations.

Antibody response in six HACEK endocarditis cases under therapy

The antibody response to bacteria of the so-called HACEK group, i.e. Haemophilus spp., Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens and Kingella kingae, was measured in sera of six patients with endocarditis. The corresponding isolates from their blood cultures were identified by conventional methods, including reactions for nitrate reduction and catalase as well as acid production from sugars. Crude antigens were prepared by glycine extraction and sonification of the blood culture isolates, and used to determine titers by complement fixation. A patient with Haemophilus parainfluenzae bacteremia received a short course of antibiotic therapy, and relapsed with spondylitis and endocarditis 5 months later. Titers of sera against his own isolate rose from 1:40 to 1:320 and fell to 1:40 after therapy within one year. A patient with C. hominis endocarditis had a similarly prolonged course. The complement fixation titer against his own isolate was already 1:240 before antibiotics were administered. Another patient with C. hominis endocarditis presented a titer of 1:320 2 weeks after the diagnosis. These three patients revealed C-reactive protein values over 50 mg/l in the first serum sample. Decrease of both antibody titers and C-reactive protein values correlated with clinical improvement. Two patients with prosthetic valve replacement 5 months earlier developed C. hominis and K. kingae endocarditis, respectively. At admission, C-reactive protein values were 64 and 82, respectively, and therapy was instituted immediately. The first sera were received 3 and 6 weeks, respectively, after isolation of the corresponding blood culture isolates and revealed already low titers, i. e. 1:80 and 1:60, respectively. A woman with A. actinomycetemcomitans endocarditis received immediate therapy and did not develop titers against her own isolate. CRP was 100 at admission and remained over 50 5 weeks later. We conclude that the complement fixation assay with individual antigen preparations was easy to perform and allowed monitoring of the antibody response in 5 of 6 HACEK endocarditis cases under therapy, but the usefulness of this method to find culture-negative HACEK endocarditis needs to be established.

[Q fever with endocarditis: clinical presentation and serologic follow-up of 21 patients]

AIM OF THE STUDY

The purpose of this study was to analyse the clinical and serological follow-up in 21 patients with Q fever endocarditis in Switzerland from 1981 to 1993.

PATIENTS AND METHODS

Criteria for Q fever endocarditis were the following: Coxiella burnetii phase I IgG > 1 : 2560 and IgA > 1 : 20 by indirect immunofluorescence. Methods to confirm the diagnosis include immunohistochemical demonstration of C. burnetii by microscopy in valvular material (1 case) and inoculation of this material in experimental animals (10 cases). Information on clinical course of the disease, laboratory abnormalities and treatment were obtained by chart review and a questionnaire sent to physicians who requested the serological tests for Q fever.

RESULTS

The average age of the patients was 47 years (15 men and 6 women). 64% of patients had a history of environmental exposure to C. burnetii. The median time of symptomatology before diagnosis was 5 months (1-108). 19/21 patients had valvular lesions, and 2/21 vascular Dacron prosthesis. Most patients presented with fever (18/21), congestive cardiac failure (14/21), weight loss (12/21), anemia (6/19), or thrombocytopenia (6/19). All the patients required antibiotic treatment. Cardiac surgery was performed in 15/21 patients. For 10 patients the geometric mean serological follow-up included at least titers at time of diagnosis (IgG anti-phase I antibodies 1 : 27024, IgA anti-phase I antibodies 1 : 685), at the end of therapy (IgG anti-phase I antibodies 1 : 2941, IgA anti-phase I antibodies 1 : 153) and 6 months after the end of therapy (IgG anti-phase I antibodies 1 : 368, IgA anti-phase I antibodies 1 : 40). The fall in anti-phase I titers was significant. During the clinical and serological outcome (median of 60 months and 69 months respectively) there was no recurrence of endocarditis and antibody titers to C. burnetii phase I remained low. Two patients died during the observation period, one from lung cancer, while the cause of death in the other was unknown.

CONCLUSIONS

Serology is the key to Q fever diagnosis. The duration of treatment, and the values to be used to establish cure of endocarditis, are not clearly defined. During the clinical and serological outcome (median of 60 months and 69 months respectively) there was no recurrence of endocarditis and antibody titers to C. burnetii phase I remained low.

[The activation mechanisms in cytomegalovirus infection]

Antibodies to cytomegalovirus class IgG and IgM and level of tumor necrosis factor (TNF) in the serum were measured in 81 patients with severe surgical infections. In patients with acute lung abscess TNF level was twice higher and activation of cytomegalovirus infection (specific IgM) was three times more frequent than in patients with infectious endocarditis. The conclusion is made that severe surgical infections inducing progressive immunodeficiency create conditions for activation of latent viral infections, cytomegalovirus, in particular). Recommendations on prevention of hemotransmissible cytomegalovirus infection are presented.

HLA-A, -B, -DR and -DQ antigens in black patients with infective endocarditis

In order to determine if genetically determined immune response factors could play a role in the pathogenesis of infective endocarditis in black patients, we performed HLA-A and HLA-B typing in 38 patients with this disease and HLA-DR and HLA-DQ typing in 33 and 27 of these individuals, respectively. HLA typing was also carried out in a control group of normal black adults. The HLA typing was done by means of a standard microlymphocytotoxicity test. No difference in HLA-A, HLA-B, HLA-DR and HLA-DQ antigen frequencies between patients and controls were noted. This study did not provide any evidence that genetic factors could contribute to a disposition to infective endocarditis.

Aggregation and binding substances enhance pathogenicity in rabbit models of Enterococcus faecalis endocarditis

We investigated the importance of enterococcal aggregation substance (AS) and enterococcal binding substance (EBS) in rabbit models of Enterococcus faecalis cardiac infections. First, American Dutch belted rabbits were injected intraventricularly with 10(8) CFU and observed for 2 days. No clinical signs of illness developed in animals given AS- EBS- organisms, and all survived. All rabbits given AS- EBS+ organisms developed signs of illness, including significant pericardial inflammation, but only one of six died. All animals given AS+ EBS- organisms developed signs of illness, including pericardial inflammation, and survived. All rabbits given AS+ EBS+ organisms developed signs of illness and died. None of the rabbits receiving AS+ EBS+ organisms showed gross pericardial inflammation. The lethality and lack of inflammation are consistent with the presence of a superantigen. Rabbit and human lymphocytes were highly stimulated in vitro by cell extracts, but not cell-free culture fluids, of AS+ EBS+ organisms. In contrast, cell extracts from AS- EBS- organisms weakly stimulated lymphocyte proliferation. Culture fluids from human lymphocytes stimulated with AS+/EBS+ enterococci contained high levels of gamma interferon and tumor necrosis factor alpha (TNF-alpha) and TNF-beta, which is consistent with functional stimulation of T-lymphocyte proliferation and macrophage activation. Subsequent experiments examined the abilities of the same strains to cause endocarditis in a catheterization model. New Zealand White rabbits underwent transaortic catheterization for 2 h, at which time catheters were removed and animals were injected with 2 x 10(9) CFU of test organisms. None of the animals given AS- EBS- organisms developed vegetations or showed autopsy evidence of tissue damage. Rabbits given AS- EBS+ or AS+ EBS- organisms developed small vegetations and had splenomegaly at autopsy. All rabbits given AS+ EBS+ organisms developed large vegetations and had splenomegaly and lung congestion at autopsy. Similar experiments that left catheters in place for 3 days revealed that all rabbits given AS- EBS- or AS+ EBS+ organisms developed vegetations, but animals given AS+ EBS+ organisms had larger vegetations and autopsy evidence of lung congestion. These experiments provide direct evidence that these two cell wall components play an important role in the pathogenesis of endocarditis as well as in conjugative plasmid transfer.

Hyperproduction of alpha-toxin by Staphylococcus aureus results in paradoxically reduced virulence in experimental endocarditis: a host defense role for platelet microbicidal proteins

Staphylococcal alpha-toxin targets several cell types which are important components of cardiac vegetations in endocarditis, including platelets, erythrocytes, and endothelial cells. We evaluated the in vivo role of Staphylococcus aureus alpha-toxin in experimental endocarditis by using isogenic strains differing in the capacity to produce functional alpha-toxin, including 8325-4 (wild-type strain), DU-1090 (a mutant strain with allelic replacement of the alpha-toxin gene [hla]), DU1090(pH35L) (a mutant strain producing a target cell-binding but nonlytic toxin), DU1090(pDU1212) (a variant of DU1090 carrying the cloned hla gene on a multicopy plasmid), and DU1090(pCL84::hla) (a variant of DU1090 with a single copy of the hla gene cloned into the chromosomal lipase locus). In vitro, wild-type alpha-toxin (from parental strain 8325-4) extensively lysed both erythrocytes and platelets. In contrast, mutant alpha-toxin [from strain DU1090(pH35L)] lysed neither cell type. Following exposure to the wild-type alpha-toxin, platelet lysates were found to contain microbicidal activity against Bacillus subtilis (but not against Micrococcus luteus), as well as against the parental and alpha-toxin variant S. aureus strains noted above. Furthermore, lysate microbicidal activity was heat stable, neutralized by polyanionic filters or compounds, and recoverable from anionic filter membranes by hypertonic saline elution. These characteristics are consistent with those of cationic platelet microbicidal proteins (PMPs). Reverse-phase high-pressure liquid chromatography and polyacrylamide gel electrophoresis confirmed the presence of three distinct PMPs (1, 2, and 3) in platelet lysates. In experimental endocarditis, the two variant staphylococcal strains producing either minimal alpha-toxin or nonlytic alpha-toxin in vitro [strains DU1090 and DU1090(pH35L), respectively] exhibited significantly lower virulence in vivo than the parental strain (decreased intravegetation staphylococcal densities). Paradoxically, the two variant staphylococcal strains producing alpha-toxin at supraparental levels in vitro [strains DU1090(p1212) and DU1090(pCL84::hla)] also exhibited significantly decreased induction rates and intravegetation staphylococcal densities in experimental endocarditis versus the parental strain. The reduced in vivo virulence of the latter variant staphylococcal strains could not be explained by differences in bacteremic clearance or initial adherence to sterile vegetations (compared to the parental strain). These findings suggest that the reduced virulence exhibited by the variant staphylococcal strains in this model was related to pathogenetic events subsequent to bacterial adherence to the damaged endocardium. Excess intravegetation secretion of alpha-toxin, leading to increased PMP release (secondary to either increased platelet secretion or lysis), may well explain the reduced virulence observed in experimental endocarditis.

Enterococcus faecalis antigens in human infections

Genomic libraries of two Enterococcus faecalis strains, OG1RF and TX52 (an isolate from an endocarditis patient), were constructed in cosmid vectors pBeloBAC11 and pLAFRx, and screened with a serum from a rabbit immunized with surface proteins of an E. faecalis endocarditis isolate and sera from four patients with enterococcal endocarditis. Seventy-five cosmid clones reacted with at least two of the sera. Thirty-eight of the 75 immunopositive clones were considered to contain distinct inserts based on their DNA restriction patterns and were chosen for further subcloning into a pBluescript vector. Each sublibrary was screened with one of the five sera, and the DNA sequence of the immunopositive subclones was determined. Analysis of these sequences revealed similarities to a range of proteins, including bacterial virulence factors, transporters, two-component regulators, metabolic enzymes, and membrane or cell surface proteins. Fourteen subclones did not show significant similarity to any sequence in the databases and may contain novel genes. Thirteen of the immunopositive cosmid clones did not yield immunopositive subclones, and one such cosmid clone produced a nonprotein antigen in Escherichia coli.

Role of phagocytosis in activation of the coagulation system in Streptococcus sanguis endocarditis

The formation of vegetations consisting of fibrin, cellular elements, humoral factors, and bacteria is the central event in the pathogenesis of bacterial endocarditis. Fibrin formation occurs on the vegetation, the coagulation system being activated locally via the expression of tissue factor (TF) on fibrin-adherent monocytes. This study was performed to assess the importance of phagocytosis of fibrin-adherent Streptococcus sanguis in the stimulation of TF expression on fibrin-adherent monocytes, as well as a role for "frustrated" phagocytosis. With the latter process, these cells are unable to remove bacteria from the fibrin surface but nonetheless might be activated to generate TF. We found that serum was not required for the stimulation of TF expression by fibrin-adherent monocytes in the presence of S. sanguis in an in vitro model for bacterial endocarditis. The bacterial adhesin dextran did not influence the TF activity (TFA) of fibrin-adherent monocytes: TFA was the same after stimulation with a dextran-positive streptococcus as with its dextran-negative mutant. Furthermore, dextran did not influence the TFA of endocardial vegetations, which was the same for vegetations isolated from rabbits infected either with dextran-positive S. sanguis or its dextran-negative mutant. These results do not support the hypothesis that in bacterial endocarditis (frustrated) phagocytosis significantly contributes to TF expression on vegetation-adherent monocytes. Fibronectin, however, although not influencing the fibrin binding of the streptococci, did enhance the TFA of monocytes in a concentration-dependent manner. We conclude that although streptococci do enhance expression of TFA on monocytes, phagocytosis and bacterial adhesins do not play a major role in this process. Stimulation of monocyte TFA may be more dependent on interactions between monocytes and the vegetational surface via fibronectin receptors, such as VLA 4 and VLA 5 (very late antigens 4 and 5).

Native-valve endocarditis caused by Staphylococcus lugdunensis

Coagulase-negative staphylococci cause about 5% of native-valve endocarditis. Staphylococcus lugdunensis, a recently-described species of coagulase-negative staphylococci, has been reported to cause destructive native-valve endocarditis with a high mortality. We report four consecutive cases of definite Staphylococcus lugdunensis native-valve endocarditis by the Duke criteria over a 4-year period. All patients required urgent aortic valve replacement 1-5 days after admission, and recovered. An intriguing, aspect in the presentation of these patients was a history of vasectomy and inguinal skin breaks in the immediate period preceding the occurrence of endocarditis.

Production of interleukin-10 and transforming growth factor beta by peripheral blood mononuclear cells in Q fever endocarditis

The pathophysiology of Q fever endocarditis is characterized by the suppression of antigen-specific cell-mediated immune responses. We investigated the production of interleukin-10 (IL-10) and transforming growth factor beta (TGF-beta), known to interfere with the development of protective cell immunity. IL-10 was markedly released by unstimulated peripheral blood mononuclear cells (PBMC) from patients with Q fever endocarditis. This release resulted from the upregulation of IL-10 gene transcription. Similarly, the release of TGF-beta1 and TGF-beta2 was significantly higher in patient PBMC than in control cells, but the expression of their respective mRNA was not enhanced in patient cells. In contrast, lipopolysaccharide-stimulated transcription and release of IL-10 and TGF-beta were similar in patients and controls. The release of IL-10 by PBMC but not that of TGF-beta was correlated with the clinical status of the patients. First, IL-10 production was correlated with specific antibody levels. Second, IL-10 release remained elevated in patients prone to relapse. Taken together, our results suggest that the release of IL-10 and TGF-beta is upregulated in Q fever endocarditis. IL-10 might be considered as a marker of disease relapses and might be instrumental in monitoring the efficiency of the treatment.

Upregulation of tumor necrosis factor alpha and interleukin-1 beta in Q fever endocarditis

The occurrence of Q fever endocarditis likely involves some alterations in the responses of monocytes, the in vivo targets of Coxiella burnetii. To test this hypothesis, the production of the inflammatory cytokines tumor necrosis factor alpha, interleukin-1 beta, and interleukin-6 was assessed in monocytes from patients with Q fever endocarditis. Spontaneous transcription and secretion of tumor necrosis factor and interleukin-1 were significantly higher in patient monocytes than in healthy controls. The interleukin-6 transcripts were also upregulated in patient cells. Moreover, in patients with recent endocarditis exhibiting high titers of immunoglobulin G directed to C. burnetii in phase I, monocytes released significantly higher levels of tumor necrosis factor and interleukin-1 than in patients with stabilized endocarditis. Immunoglobulin G titers and the overproduction of tumor necrosis factor and interleukin-1 were significantly correlated. Hence, the overproduction of inflammatory cytokines might be a marker of disease activity.

Defining antibody targets in Streptococcus oralis infection

Immunoblotting of sera from 12 neutropenic patients with Streptococcus oralis septicemia and 18 patients with endocarditis due to viridans group streptococci revealed immunodominant S. oralis antigens at 85 and 180 kDa. The former cross-reacted with a mouse monoclonal antibody to hsp90. The latter was identified by sequencing positive clones obtained by screening a genomic expression library of S. oralis with pooled sera from patients who had been infected with S. oralis. Antibody eluted from one of these clones reacted with the 180-kDa antigen of S. oralis. Southern blotting confirmed the origin of the clone from S. oralis. The derived amino acid sequence showed 76.2% homology with the PAc protein precursor of Streptococcus mutans and 73.8% homology with the SpaA protein precursor of Streptococcus sobrinus. Epitope mapping of the derived amino acid sequence with sera from patients with viridans group streptococcal endocarditis delineated nine epitopes. Peptides 1 (TMYPNRQPGSGWDSS) and 2 (WYSLNGKIRAVDVPK), representing two of these epitopes, and peptide 3 (YEVEKPLEPAPVAPS), representing the repeat proline region, were synthesized. These three peptides were used to screen a phage antibody display library derived from a patient who had recovered from S. oralis infection. Two of the human recombinant antibodies produced (SORAL 3 and SORAL 4 against peptide 3) and a human recombinant antibody (B3.7) against the conserved epitope (LKVIRK) of hsp90 gave statistically significant protection, compared with control groups, in a mouse model of lethal S. oralis infection.