Short report: identification of B-cell epitopes in the serine-rich Entamoeba histolytica protein

The serine-rich Entamoeba histolytica protein (SREHP) has been shown to be a protective antigen in animal models of amebic liver abscess when delivered by either parenteral or oral routes of immunization, and antibodies to SREHP can prevent amebic liver abscess in severe combined immunodeficient mice. To identify B cell epitopes of the SREHP molecule that could serve as the basis for a peptide-based vaccine, we synthesized overlapping peptides spanning the amino acid sequence of SREHP, and looked at the reactivity of serum samples from five individuals with amebic liver abscess to the overlapping peptides. We found that most of the epitopes recognized by serum samples from patients with amebic liver abscess map to the hydrophilic dodecapeptide or octapeptide repeats of SREHP, but there was no universal epitope recognized by all five serum samples. In addition, we show that synthetic peptides that include the epitopes of SREHP recognized in the mapping study are immunogenic in animals and can generate antibodies that recognize SREHP.

Adjustment and characterization of an original model of chronic ischemic heart failure in pig

We present and characterize an original experimental model to create a chronic ischemic heart failure in pig. Two ameroid constrictors were placed around the LAD and the circumflex artery. Two months after surgery, pigs presented a poor LV function associated with a severe mitral valve insufficiency. Echocardiography analysis showed substantial anomalies in radial and circumferential deformations, both on the anterior and lateral surface of the heart. These anomalies in function were coupled with anomalies of perfusion observed in echocardiography after injection of contrast medium. No demonstration of myocardial infarction was observed with histological analysis. Our findings suggest that we were able to create and to stabilize a chronic ischemic heart failure model in the pig. This model represents a useful tool for the development of new medical or surgical treatment in this field.

First Report of Tomato yellow leaf curl virus Infecting Tomato, Tomatillo, and Peppers in Guatemala

In Guatemala and other Central American countries, whitefly-transmitted geminiviruses (begomoviruses) cause economically important diseases of tomato (Solanum lycopersicum) and pepper (Capsicum annuum). Disease symptoms include stunted and distorted growth and leaf curling, crumpling, light green to yellow mosaic, purpling, and vein swelling. In Guatemala, at least eight bipartite begomovirus species infect tomato or peppers (1), but their role and relative importance is unclear. As part of an Integrated Pest Management strategy to manage these diseases, surveys for begomovirus symptoms in pepper and tomato have been conducted in the Salama Valley, Sanarate, and other locations since 2003, and begomoviruses were identified by squash blot hybridization, PCR and DNA sequencing. Beginning in 2006, a new type of symptom, stunted upright growth and upcurled leaves with yellowing of the margins and interveinal areas, was observed in tomato and tomatillo plants in the Salama Valley and Sanarate. These symptoms were similar to those induced by the exotic monopartite begomovirus Tomato yellow leaf curl virus (TYLCV). Evidence that TYLCV caused these symptoms came from positive results in high stringency squash blot hybridization tests with a TYLCV probe, and amplification of the expected size of ~0.3- and 2.8-kb fragments in PCR tests with TYLCV capsid protein (CP) gene and full-length component primer pairs, respectively (3). Sequence analyses of PCR-amplified CP fragments and portions of full-length fragments revealed 97 to 99% identity with isolates of TYLCV-Israel (TYLCV-IL). The complete nucleotide sequence of an isolate from the Salama Valley (GenBank Accession No. GU355941) was >99% identical to those of TYLCV-IL isolates from the Dominican Republic, Florida, and Cuba and ~97% identical to those of isolates from Mexico and California. Thus, this TYLCV-IL isolate (TYLCV-IL[GT:06]) was probably introduced from the Caribbean Region. To further characterize begomoviruses in the Salama Valley, leaf samples were collected from 44 and 118 tomato plants showing symptoms of begomovirus infection in March 2006 and 2007, respectively, and from 106 symptomatic pepper plants in March 2007. Begomovirus infection was confirmed in 42 of 44 and 93 of 118 of the tomato samples and 100 of 106 of the pepper samples based on PCR amplification of the expected size of ~0.6- and 1.1-kb DNA fragments with the begomovirus degenerate primers pairs AV494/AC1048 and PAL1v1978/PAR1c496, respectively (2,4). Sequence analyses of cloned PCR-amplified fragments revealed that 3 of the 44 and 16 of the 118 tomato samples collected in 2006 and 2007, respectively, and 9 of the 106 pepper samples were infected with TYLCV based on >97% identity with TYLCV-IL. In all samples, TYLCV was present in mixed infections with other begomoviruses. The introduction of TYLCV adds to the already high level of genetic complexity of bipartite begomovirus infection of tomatoes and peppers in Guatemala and will undoubtedly complicate disease management efforts. References: (1) M. K. Nakhla et al. Acta Hortic. 695:277, 2005. (2) M. R. Rojas et al. Plant Dis. 77:340, 1993. (3) R. Salati et al. Phytopathology 92:487, 2002. (4) S. D. Wyatt and J. Brown. Phytopathology 86:1288, 1996.

Assessing cardiovascular risk factors after coronary artery bypass surgery: value of an aggressive strategy including systematic follow-up

INTRODUCTION

Coronary revascularization surgery is a palliative treatment modality which should not preclude efforts to treat atherosclerosis.

AIM

To assess ongoing cardiovascular risk factors after coronary artery bypass surgery and develop a strategy to attenuate such factors.

METHODS

108 patients requiring a coronary artery bypass were included: 2 died soon after surgery and 6 were excluded for personal reasons. 100 patients were re-admitted into hospital 7 months after surgery for risk factor assessment. Eight months later, they were re-contacted by telephone (systematic follow-up) for a re-assessment.

RESULTS

The population consisted of 77 men with an average age of 64+/-11 years. Prior to the operation, the known risk factors were: smoking 34%; HBP 61%; cholesterol 47%; diabetes 30%; obesity 25%. During their hospital stay six months after the procedure: 91% of the patients had at least one lipid metabolism abnormality. New-onset diabetes was diagnosed in 5%. Blood pressure was uncontrolled in 18% and 10% were still smoking. Patients tended to be putting on weight and 55% engaged in little or no physical activity. Systematic follow-up: lipid metabolism had normalized in 70% of the patients. Blood glucose levels were significantly lower. Blood pressure was uncontrolled in 9% and 4% were still smoking. Their weight had stabilized and 65% were engaging in moderate-to-strenuous physical activity.

CONCLUSION

Inadequate attention is paid to risk factors after coronary artery bypass surgery. A short hospital stay including a cardiovascular evaluation and education about risk factors has a positive impact on the management of atherosclerosis in the medium term.

[Perioperative anticoagulation management for prosthetic heart valves]

OBJECTIVES

The practices and the guidelines over the perioperative management of the anticoagulation of patients with cardiac valves prothesis are the object of no consensual attitude. The thrombotic risk over the time is well known. It depends of the type or the location on the valve, of their associations and the age of the patient. In the perioperative period, the antithrombotic treatment must be interrupted according to the surgical haemorrhagic risk.

STUDY DESIGN

Short review.

RESULTS

Only patients, without associated risk factor, carriers of bioprosthesis from more than 3 months, can be maintained only under antiplatelets agents. In others situations, the caution imposes a bridge of anticoagulants from 48 to 72 hours with unfractionated heparin (subcutaneous at home, intravenous at the hospital). Low molecular weight heparin has no commercial authorization in this indication. The resumption of the anticoagulation by unfractionated heparin in postoperative period must be the most premature possible after the decrease of the surgical bleeding. The relay by vitamin K antagonists has to be made over 48 to 72 hours. Within the framework of the urgency, the surgical haemorrhagic risk is weak for an INR <1.5. According to the urgency of the surgery, a treatment by vitamin K (if the delay is over 12 hours) or by prothrombinic complex allows to correct this INR. The identification of thrombotic complications requires a particular attention. In the postoperative period, as soon as there is suspicion of thrombosis, clinical manifestations must be consolidated by the practice of a transoesophageal echography, which only confirm the diagnosis.

B-cell epitopes recognized by IgE from patients sensitive to Amb a 5

BACKGROUND

The response to allergens characterized by IgE-mediated hypersensitivity is selective. The search for the inherited contribution to atopy has among other things, focused on the linkage of sensitivity to the presence of specific alleles in the DR and DQ locus. More than 90% of the responders to Amb a 5, an allergen from ambrosia artemisifolia, are DR-2 positive. This relationship is logically linked to the T-cell epitope presentation by the HLA complex.

OBJECTIVES

This study aims to investigate a possible relationship between T-cell epitopes, B-cell epitopes and the alleles of the DR and DQ loci in Amb a 5 sensitive DR-2+ and DR-2- individuals.

METHODS

Inhibition of solid state Elisa assays by IgE-enriched and IgG-depleted, heated sera. The inhibition was carried out in checkerboard pattern, bidirectionally; A inhibits B and B inhibits A.

RESULTS

The B-cell epitopes defined by the inhibition pattern were all found to be conformational. Three different epitope patterns (A, B, C) were recognized. The IgE and IgG complexes were found in only one responder. The DR and DQ locus alleles were all sequenced. Although all the individuals studied responding to Amb a 5 show presence of alleles such as 1501, associated with DR-2, our data indicates no correlation between the B-cell epitopes recognized and the DR and DQ locus alleles. A well known, general T-cell motif was recognized in the known sequence of Amb a 5.

CONCLUSIONS

Our investigation suggests that the choice of B-cell recognition is regulated independently of a putative link between T-cell epitope recognition and the D locus.

First Report of Golden Dwarf Mistletoe on Pinus maximinoi

Golden dwarf mistletoe (Arceuthobium aureum subsp. aureum Hawksw. & Wiens) is endemic to east-central Guatemala (Departments Alta Verapaz, Baja Verapaz, and Quiche) (1,2). Its principal hosts are Pinus pseudostrobus Lindl., P. montezumae Lamb., and P. oaxacana Mirov (1). In May 1999, A. aureum subsp. aureum was observed infecting Pinus maximinoi H. E. Moore at four locations: 1.0 km south (altitude 1,580 m) and 5.4 km north (altitude >1,630 m) of La Cumbre, Baja Verapaz on Route CA-14, 8 km west (altitude 1,670 m) of Chilasco, Baja Verapaz, and 5 km west (altitude 1,490 m) of San Cristobal Verapaz, Alta Verapaz on Route 7-W. Although previous reports (1,2) indicated that golden dwarf mistletoe does not induce witches'-brooms on its hosts, older (>50 years), severely affected P. maximinoi were observed to have formed large witches'-brooms as a result of dwarf mistletoe infection. Although it has been suggested that Pinus oocarpa Schiede is susceptible to golden dwarf mistletoe (1), several large trees of this species were observed growing within 5 m of infected P. maximinoi at three of the four locations, but none were infected. This is the first report of golden dwarf mistletoe on P. maximinoi. References: (1) F. G. Hawksworth and D. Wiens. 1996. Dwarf Mistletoes: Biology, Pathology, and Systematics. USDA Agric. Handb. 709. (2) D. Wiens and C. G. Shaw, J. Idaho Acad. Sci. 30:25, 1994.

Generation and characterization of monoclonal antibodies specific for the human IFN-gamma receptor

Purified preparations of the human IFN-gamma R derived from placental membranes were used to produce receptor-specific murine mAb. Supernatants from growth-positive wells were screened for their ability to block binding of 125I-IFN-gamma to human placental membranes. Ten inhibitory cultures were identified. Two of these (GIR-208 and GIR-301) abrogated all binding of radioligand to either intact placental membranes or soluble, purified IFN-gamma R. Three others (GIR-72, 76 and 94) showed moderate blocking activity (65, 59, and 49%, respectively) whereas the remaining five (GIR-57, 67, 83, 109, and 153) blocked binding to a low but significant extent (20 to 40%). Specificity experiments demonstrated that the antibodies reacted with the receptor and not the ligand (IFN-gamma). None of the antibodies reacted with IFN-gamma by ELISA. Moreover, GIR-208 and GIR-301, but not isotype-matched controls, identified the receptor by Western blot analysis. GIR-208 and GIR-301 also completely abrogated binding of 125I-IFN-gamma to either mononuclear phagocytes (U937) or human fibroblasts (WISH). Competition experiments revealed that GIR-208 and GIR-301 recognized similar epitopes on the IFN-gamma R and that these (or this) epitopes were identical to or linked to the ligand binding site of the receptor. In addition, both antibodies inhibited development of IFN-gamma-dependent anti-viral activity in WISH cells in a dose-dependent fashion. These data thus indicate that the IFN-gamma R expressed on human placental cells, mononuclear phagocytes, and fibroblasts are similar.

Regulation of immunity and inflammation by mediators from macrophages

Mononuclear phagocytes secrete a number of materials into the extracellular environment. The materials secreted by phagocytes can be grouped into three categories: a) enzymes affecting extracellular proteins (collagenase, elastase, lysosomal proteases, plasminogen activators), b) materials involved in defense processes (complement proteins, interferons, lysozyme), and c) factors regulating activities of surrounding cells. The latter include lymphostimulatory molecules, a colony-stimulating factor, and inhibitors of cell growth. The conditions for secretion of the materials depend on the activity of the phagocytes. The lymphostimulatory molecules secreted by macrophages exert various effects: 1) an increase in DNA synthesis of lymphocytes, 2) a maturation of early thymocytes to mature T cells, and 3) the differentiation of some B cells to antibody-secreting cells. The mitogenic principle has been partially isolated as a protein of 15,000 to 20,000 daltons. The secretion of lymphostimulatory molecules is increased following uptake of various materials by macrophages or by addition of activated T cells to macrophage cultures.

Reduced receptor binding by a human interferon-gamma fragment lacking 11 carboxyl-terminal amino acids

Treatment of recombinant human interferon-gamma (IFN-gamma) with either 1) the arginine-specific proteases clostripain or submaxillaris protease or 2) the broadly specific enzyme pronase produced a stable fragment with m.w. of 15,500. Structural analysis showed that the cleavage occurred between residues 129 and 130 and thus produced a fragment lacking only 11 carboxyl-terminal amino acids. The fragmented and untreated molecules showed identical amino-terminal amino acid sequences and were equally reactive with either polyclonal or monoclonal anti-IFN-gamma. IFN-gamma lacking carboxyl-terminal amino acids displayed a 1000- to 2000-fold reduction in its capacity to bind to cellular IFN-gamma receptors at 4 degrees C. Functionally the fragment showed a 50-fold reduction in its ability to induce antiviral activity in fibroblasts and a 10-fold reduction in its ability to induce Fc receptors on the human histiocytic lymphoma cell line U937. These results thus suggest that the carboxyl terminus of human IFN-gamma contributes significantly to the formation of the receptor-binding site of the molecule.

Sarcoidosis with incomplete bilateral bundle branch block pattern disappearing following steroid therapy: an electrophysiological study

A man with a 30-year history of pulmonary sarcoidosis, confirmed by lymph node biopsy and a positive Kveim reaction, developed an incomplete bilateral bundle branch block pattern. Cardiac catherization and angiography revealed normal pressures, hemodynamic parameters and left ventricular contractile pattern; the coronary arteries were patent. His bundle electrograms demonstrated a normal H-V interval that was not altered by atrial pacing. After four weeks of steroid therapy the electrocardiographic abnormality disappeared. However, when restudied at this time, incomplete bilateral bundle branch block pattern could be elicited on atrial pacing and with the extrastimulus technique. Other electrophysiological observations suggested the presence of an AV nodal bypass tract and demonstrated changing intraventricular conduction patterns. The implications of these findings are discussed.