Resistance to salmonid fish viral infections: Induction and improvement of cellular antiviral states

The present study aimed to analyse comparatively the protection induced by polycytidylic acid (poly I:C), a potent interferon inductor, and several salmonid fish viruses against homologous or heterologous viruses in vitro (in BF-2 cells) and in vivo in the brown trout Salmo trutta L., 1758), in single or dual infections. The expression of MxmRNA protein was used as an interferon marker. The results showed strong interference activity against rhabdoviruses in the supernatants of macrophages stimulated with poly I:C and with heterologous rhabdoviruses. The antiviral effectiveness of the cytokine-like activities differed amongst the several viruses tested. Moreover, high reduction of cumulative mortality was shown in poly I:C stimulated (3 days before infection) and IPNV-IHNV coinfected trout. A correlation between stimulation, antiviral activity and mRNA-Mx protein expression was also observed. The results indicate that interferon-mediated activity plays a significant role in the loss of IHNV virulence when it is coinfected with IPNV.El propósito de este trabajo fue analizar comparativamente la protección inducida por el ácido polycitidílico (poly I:C), un potente inductor de interferón, y algunos virus de salmónidos frente a infecciones producidas por virus homólogos o heterólogos, tanto in vitro (en células BF-2) como in vivo (en trucha común Salmo trutta L., 1758). Los resultados demostraron que los sobrenadantes de macrófagos de trucha común, estimulados con poly I:C y rhabdovirus, inducen una actividad antivírica e interferente considerable, especialmente frente a rhabdovirus heterólogos. La efectividad antivírica de esta actividad citokina-like fue distinta según los virus ensayados. También se constató una reducción alta de la mortalidad acumulada en truchas estimuladas con poly I:C (tres días antes de la infección) y coinfectadas con una mezcla de IPNV-IHNV en la misma proporción. Se observó una correlación entre estimulación, actividad antivírica y expresión de Mx mRNA. Los resultados indican que el interferón desempeña un papel importante en la pérdida de infectividad del IHNV en las coinfecciones con IPNV.Instituto Español de Oceanografí

Search for CP Violation in the Decay Z -> b (b bar) g

About three million hadronic decays of the Z collected by ALEPH in the years 1991-1994 are used to search for anomalous CP violation beyond the Standard Model in the decay Z -> b \bar{b} g. The study is performed by analyzing angular correlations between the two quarks and the gluon in three-jet events and by measuring the differential two-jet rate. No signal of CP violation is found. For the combinations of anomalous CP violating couplings, ${\hat{h}}_b = {\hat{h}}_{Ab}g_{Vb}-{\hat{h}}_{Vb}g_{Ab}$ and $h^{\ast}_b = \sqrt{\hat{h}_{Vb}^{2}+\hat{h}_{Ab}^{2}}$, limits of \hat{h}_b < 0.59$and$h^{\ast}_{b} < 3.02$ are given at 95\% CL.Comment: 8 pages, 1 postscript figure, uses here.sty, epsfig.st

The impact of co-infections on fish: a review

International audienceAbstractCo-infections are very common in nature and occur when hosts are infected by two or more different pathogens either by simultaneous or secondary infections so that two or more infectious agents are active together in the same host. Co-infections have a fundamental effect and can alter the course and the severity of different fish diseases. However, co-infection effect has still received limited scrutiny in aquatic animals like fish and available data on this subject is still scarce. The susceptibility of fish to different pathogens could be changed during mixed infections causing the appearance of sudden fish outbreaks. In this review, we focus on the synergistic and antagonistic interactions occurring during co-infections by homologous or heterologous pathogens. We present a concise summary about the present knowledge regarding co-infections in fish. More research is needed to better understand the immune response of fish during mixed infections as these could have an important impact on the development of new strategies for disease control programs and vaccination in fish

Production of excited beauty states in Z decays

A data sample of about 3.0 million hadronic Z decays collected by the ALEPH experiment at LEP in the years 1991 through 1994, is used to make an inclusive selection of B~hadron events. In this event sample 4227 \pm 140 \pm 252 B^* mesons in the decay B^* \to B \gamma and 1944 \pm 108 \pm 161 B^{**} mesons decaying into a B~meson and a charged pion are reconstructed. For the well established B^* meson the following quantities areobtained: \Delta M = M_{B^*} - M_{B} = (45.30\pm 0.35\pm 0.87)~\mathrm{MeV}/c^2 and N_{B^*}/(N_B+N_{B^*}) = (77.1 \pm 2.6 \pm 7.0)\%. The angular distribution of the photons in the B^* rest frame is used to measure the relative contribution of longitudinal B^* polarization states to be \sigma_L/(\sigma_L + \sigma_T)= (33 \pm 6 \pm 5)\%. \\ Resonance structure in the M(B\pi)-M(B) mass difference is observed at (424 \pm 4 \pm 10)~\mathrm{MeV}/c^2. Its shape and position is in agreement with the expectation for B^{**}_{u,d} states decaying into B_{u,d}^{(*)} \pi^\pm. The signal is therefore interpreted as arising from them. The relative production rate is determined to be \frac{BR(Z \to b \to B_{u,d}^{**})}{BR(Z \to b \to B_{u,d})} = [27.9 \pm 1.6(stat) \pm 5.9(syst) \phantom{a}^{+3.9}_{-5.6}(model)]\%. where the third error reflects the uncertainty due to different production and decay models for the broad B_{u,d}^{**} states

Tau hadronic branching ratios

From 64492 selected \tau-pair events, produced at the Z^0 resonance, the measurement of the tau decays into hadrons from a global analysis using 1991, 1992 and 1993 ALEPH data is presented. Special emphasis is given to the reconstruction of photons and \pi^0's, and the removal of fake photons. A detailed study of the systematics entering the \pi^0 reconstruction is also given. A complete and consistent set of tau hadronic branching ratios is presented for 18 exclusive modes. Most measurements are more precise than the present world average. The new level of precision reached allows a stringent test of \tau-\mu universality in hadronic decays, g_\tau/g_\mu \ = \ 1.0013 \ \pm \ 0.0095, and the first measurement of the vector and axial-vector contributions to the non-strange hadronic \tau decay width: R_{\tau ,V} \ = \ 1.788 \ \pm \ 0.025 and R_{\tau ,A} \ = \ 1.694 \ \pm \ 0.027. The ratio (R_{\tau ,V} - R_{\tau ,A}) / (R_{\tau ,V} + R_{\tau ,A}), equal to (2.7 \pm 1.3) \ \%, is a measure of the importance of QCD non-perturbative contributions to the hadronic \tau decay widt