Grass pollen immunotherapy induces an allergen-specific IgA2 antibody response associated with mucosal TGF-beta expression

Allergen immunotherapy (IT) has long-term efficacy in IgE-mediated allergic rhinitis and asthma. IT has been shown to modify lymphocyte responses to allergen, inducing IL-10 production and IgG Abs. In contrast, a putative role for IgA and local TGF-beta-producing cells remains to be determined. In 44 patients with seasonal rhinitis/asthma, serum IgA1, IgA2, and polymeric (J chain-containing) Abs to the major allergen Phl p 5 were determined by ELISA before and after a 2-year double-blind trial of grass pollen (Phleum pratense) injection IT. Nasal TGF-beta expression was assessed by in situ hybridization. Sera from five IT patients were fractionated for functional analysis of the effects of IgA and IgG Abs on IL-10 production by blood monocytes and allergen-IgE binding to B cells. Serum Phl p 5-specific IgA2 Abs increased after a 2-year treatment (approximately 8-fold increase, p = 0.002) in contrast to IgA1. Increases in polymeric Abs to Phl p 5 (approximately 2-fold increase, p = 0.02) and in nasal TGF-beta mRNA (p = 0.05) were also observed, and TGF-beta mRNA correlated with serum Phl p 5 IgA2 (r = 0.61, p = 0.009). Post-IT IgA fractions triggered IL-10 secretion by monocytes while not inhibiting allergen-IgE binding to B cells as observed with IgG fractions. This study shows for the first time that the IgA response to IT is selective for IgA2, correlates with increased local TGF-beta expression, and induces monocyte IL-10 expression, suggesting that IgA Abs could thereby contribute to the tolerance developed in IT-treated allergic patients.     

IFN-gamma produced by human papilloma virus-18 E6-specific CD4+ T cells predicts the clinical outcome after surgery in patients with high-grade cervical lesions

Cervical neoplastic lesions are associated with infection by high-risk human papilloma viruses (HPVs). HPV-16 and HPV-18 are the most common genotypes. It has been proposed that development of HPV-16-positive cervical lesions is associated with impaired CD4(+) T cell immunity against early Ags. The aim of the study was to evaluate whether this impairment also applies to HPV-18. We investigated the presence and the quality of anti-HPV-18 E6 CD4(+) T cell responses in the blood of 37 consecutive patients with high-grade cervical lesions, 25 normal donors, and 20 cord bloods. The immune infiltrate in the cervical lesions was also evaluated. The characteristics of the responses were correlated to the clinical outcome. We found that one or more HPV-18 E6 peptides, containing naturally processed epitopes, were able to induce a response in 40-50% of the patients, depending on the effector function tested. Importantly, these percentages rose to 80-100% when HPV-18-positive patients were considered. HPV-18 E6-specific CD4(+) T cells produced mixed Th1/Th2 responses and statistical analysis of the cytokines produced revealed that the amount of IFN-gamma released could predict infection persistence and/or disease relapse after surgery. Finally, we found that a higher number of infiltrating CD4(+) and T-bet(+) T cells in the lesions correlated with a favorable clinical outcome. Our results strongly suggest a relevant role for CD4(+) T cells in the control of the HPV-18 compared with HPV-16 infections in patients with high-grade cervical lesions and identify an immunologic parameter potentially useful for patients' stratification.     

Diminished potential for B-lymphoid differentiation after murine leukemia virus infection in vivo and in EML hematopoietic progenitor cells

Infection with a recombinant murine-feline gammaretrovirus, MoFe2, or with the parent virus, Moloney murine leukemia virus, caused significant reduction in B-lymphoid differentiation of bone marrow at 2 to 8 weeks postinfection. The suppression was selective, in that myeloid potential was significantly increased by infection. Analysis of cell surface markers and immunoglobulin H gene rearrangements in an in vitro model demonstrated normal B-lymphoid differentiation after infection but significantly reduced viability of differentiating cells. This reduction in viability may confer a selective advantage on undifferentiated lymphoid progenitors in the bone marrow of gammaretrovirus-infected animals and thereby contribute to the establishment of a premalignant state.     

Probing the flavivirus membrane fusion mechanism by using monoclonal antibodies

In this study, we investigated in a flavivirus model (tick-borne encephalitis virus) the mechanisms of fusion inhibition by monoclonal antibodies directed to the different domains of the fusion protein (E) and to different sites within each of the domains by using in vitro fusion assays. Our data indicate that, depending on the location of their binding sites, the monoclonal antibodies impaired early or late stages of the fusion process, by blocking the initial interaction with the target membrane or by interfering with the proper formation of the postfusion structure of E, respectively. These data provide new insights into the mechanisms of flavivirus fusion inhibition by antibodies and their possible contribution to virus neutralization.     

Distribution and structure-function relationship of myosin heavy chain isoforms in the adult mouse heart

The two cardiac myosin heavy chain isoforms, alpha and beta, exhibit distinct functional characteristics and therefore may be distributed regionally within the heart to match the functional demands of a specific region. In adult mouse hearts, which predominantly express alpha-myosin heavy chain, we observed high concentrations of beta-myosin in distinct areas such as at the tip of papillary muscles and at the base close to the valvular annulus. In light of these distinct distribution patterns of the myosin isoforms, we subsequently explored the isoform-specific structure-function relationships of the myosins. The alpha- and beta-isoforms are 93% identical in amino acid sequence, but it remains unclear which of the nonidentical residues determines isoform functionality. We hypothesized that residues situated within or close to the actin-binding interface of the myosin head influence actin binding and thereby modulate actin-activated ATPase activity. A chimeric myosin was created containing beta-sequence from amino acid 417 to 682 within the alpha-backbone. In mice, approximately 70% of the endogenous cardiac protein was replaced with the chimeric myosin. Myofibrils containing chimeric myosin exhibited ATPase activities that were depressed to the levels observed in hearts expressing approximately 70% beta-myosin. In vitro motility assays showed that the actin filament sliding velocity generated by chimeric myosin was similar to that of alpha-myosin, almost twice the velocities observed with beta-myosin. These data indicate that this large domain sequence switch conferred beta-like actin-activated ATPase activities to the chimeric myosin, suggesting that this region is responsible for the distinct hydrolytic properties of these myosin isoforms.     

Sequential growth of fetal sheep cardiac myocytes in response to simultaneous arterial and venous hypertension

While the fetal heart grows by myocyte enlargement and proliferation, myocytes lose their capacity for proliferation in the perinatal period after terminal differentiation. The relationship between myocyte enlargement, proliferation, and terminal differentiation has not been studied under conditions of combined arterial and venous hypertension, as occurs in some clinical conditions. We hypothesize that fetal arterial and venous hypertension initially leads to cardiomyocyte proliferation, followed by myocyte enlargement. Two groups of fetal sheep received intravascular plasma infusions for 4 or 8 days (from 130 days gestation) to increase vascular pressures. Fetal hearts were arrested in diastole and dissociated. Myocyte size, terminal differentiation (%binucleation), and cell cycle activity (Ki-67[+] cells as a % of mononucleated myocytes) were measured. We found that chronic plasma infusion greatly increased venous and arterial pressures. Heart (but not body) weights were approximately 30% greater in hypertensive fetuses than controls. The incidence of cell cycle activity doubled in hypertensive fetuses compared with controls. After 4 days of hypertension, myocytes were (approximately 11%) longer, but only after 8 days were they wider (approximately 12%). After 8 days, %binucleation was approximately 50% greater in hypertensive fetuses. We observed two phases of cardiomyocyte growth and maturation in response to fetal arterial and venous hypertension. In the early phase, the incidence of cell cycle activity increased and myocytes elongated. In the later phase, the incidence of cell cycle activity remained elevated, %binucleation increased, and cross sections were greater. This study highlights unique fetal adaptations of the myocardium and the importance of experimental duration when interpreting fetal cardiac growth data.     

Ascorbic acid oxidase is dynamically regulated by light and oxygen. A tool for oxygen management in plants?

Ascorbic acid oxidase (AAO) is a plant blue-copper protein catalyzing dioxygen reduction to water using ascorbic acid as the electron donor. In spite of extensive molecular characterization the physiological role of AAO is still uncertain. Abundant mRNA, protein and activity of AAO were observed in illuminated leaves of Cucurbita pepo. AAO activity was found to be proportional to light intensity. The light effect was rapidly reversed in dark and activity remained low throughout the dark period. Activity was elicited in dark by increased oxygen concentration. AAO activity increased in the facultative CAM Kalancho? blossfeldiana upon induction of the CAM cycle and decreased during germination of C. pepo and Zea mays under hypoxic conditions. These results strongly suggest that AAO activity could be part of a dynamic system for oxygen management in plants.     

Wnt signaling mediates regional specification in the vertebrate face

At early stages of development, the faces of vertebrate embryos look remarkably similar, yet within a very short timeframe they adopt species-specific facial characteristics. What are the mechanisms underlying this regional specification of the vertebrate face? Using transgenic Wnt reporter embryos we found a highly conserved pattern of Wnt responsiveness in the developing mouse face that later corresponded to derivatives of the frontonasal and maxillary prominences. We explored the consequences of disrupting Wnt signaling, first using a genetic approach. Mice carrying compound null mutations in the nuclear mediators Lef1 and Tcf4 exhibited radically altered facial features that culminated in a hyperteloric appearance and a foreshortened midface. We also used a biochemical approach to perturb Wnt signaling and found that in utero delivery of a Wnt antagonist, Dkk1, produced similar midfacial malformations. We tested the hypothesis that Wnt signaling is an evolutionarily conserved mechanism controlling facial morphogenesis by determining the pattern of Wnt responsiveness in avian faces, and then by evaluating the consequences of Wnt inhibition in the chick face. Collectively, these data elucidate a new role for Wnt signaling in regional specification of the vertebrate face, and suggest possible mechanisms whereby species-specific facial features are generated.