117,371 research outputs found
On the product of M-measures in l-groups
No full textIn this paper we continue the investigation dealt with in
A. BOCCUTO - B. RIECAN, On extension theorems for M-measures in l-groups, Math. Slovaca (2008).
Starting from an extension-type existence theorem for M-measures with values in l-groups, we obtain existence results in
the countably compact case for M-measures and product of M-measures.
The motivation of this study in due to the fact that
in probability theory, in many applications it is advisable to deal with set functions, which are not necessarily additive, but satisfy other properties: for example, continuity
from below and from above for sequences of sets and "compatibility" with respect to the operations
of finite suprema and infima. These functions are called M-measures. For example, in decision making, this is the case of the theory of intuitionistic fuzzy events
(shortly IF-events), which are pairs A = (μA, nu A) of measurable functions μA, nu A : Omega -->[0, 1]
such that μA+nu A <= 1. Another application is the theory of joint random variables: in this context theM-measure extension theorem plays a crucial role in the construction of joint observables. Moreover, to consider latticegroup
or Riesz space-valued set functions allows to get applications in stochastic processes and in probabilities depending on the time and/or on the informations of the individual
Some new results about Brooks-Jewett and Dieudonné-type theorems in l-groups
No full textIn this paper we present some new versions of Brooks-Jewett and Dieudonne'-type theorems for l-group-valued measures.
Here the concepts of s-boundedness, sigma-additivity and regularity are formulated similarly as in the classical case, and not directly related to order sequences, regulators or similar objects. We use the tools of the Maeda-Ogasawara-Vulikh representation theorem and a technical lemma, which allows to prove some properties of l-group-valued measures using the corresponding ones of real-valued set functions
Some new results on ideal limit theorems in l-groups
No full textWe present some limit theorems for sequences of
measures, taking values in l-groups, in the setting
of ideal convergence. We use the tool of ideal exhaustiveness
in order to prove some results on uniform s-boundedness, uniform sigma-additivity, uniform absolute continuity and uniform regularity of a suitable subsequence of the given one, whose indexes belong to the dual filter associated to the ideal involved. We observe that, in general, ideal exhaustiveness is a condition, which cannot be dropped and we give an example about it. We deal with Frechet-Nikodym topologies and submeasures
Dieudonnè-type theorems for set functions with values in (l)-groups
No full textSome versions of Dieudonne' theorems are given for finitely additive set functions, not necessarily positive, taking values in Dedekind-complete (l)-groups. In our setting, regularity, strong boundedness and pointwise convergence of the measures involved are intended in the setting of (D)-convergence and with respect of a same regulator
Ideal limit theorems and their equivalence in l-group setting
No full textWe prove some equivalence results between
limit theorems for sequences of
l-group-valued measures, with respect to
order ideal convergence. A fundamental role is
played by the tool of uniform ideal
exhaustiveness of a measure sequence already
introduced for the real case or more generally
for the Banach space case in our recent papers,
to get some results on uniform
strong boundedness and uniform countable
additivity. We consider both the case in which
strong boundedness, countable additivity and the
related concepts are formulated with respect
to a common order sequence and the context in
which these notions are given in a classical like
setting, that is not necessarily with respect to a
same (O)-sequence. We show that, in general,
uniform ideal exhaustiveness cannot be omitted.
Finally we pose some open problems
Ideal convergence and divergence of nets in l-groups
No full textIn this paper we introduce the I- and I^*-convergence and divergence of nets in l-groups. We prove some theorems relating
different types of convergence/divergence for nets in l-group setting, in relation with ideals. We consider both order and (D)-convergence.
By using basic properties of order sequences,
some fundamental properties, Cauchy-type characterizations
and comparison results are derived.
We prove that I^-convergence/divergence implies
I-convergence/divergence for every ideal, admissible for
the set of indexes with respect to which the net involved is directed, and we investigate a class of ideals for which the converse implication holds
Novel antiviral strategies against emerging viral diseases
No full textNovel antiviral strategies against emerging viral diseases
Doctoral Research School of Biochemistry and Molecular Biology-Cycle XXXII; Tutor: Luisa Bracci; Supervisor: Maurizio Zazzi; Candidate: Adele Boccuto
Background
Zika virus (ZIKV) Dengue virus (DENV) and West Nile virus (WNV) belong to the Flaviviridae family. The World Health Organization has ranked DENV as the most critical mosquito-borne viral disease and declared ZIKV an international public health emergency. Indeed, WNV is widely established in USA and some European areas and is associated to neuroinvasive disease. Despite intensive work, no specific antiviral therapy is available for ZIKV, DENV or WNV. In addition, increasing co-infections with different flaviviruses or serotypes cocirculating within the same area complicate the clinical outcome and treatment options. The high degree of conservation of some viral enzymes or host factor essential for Flaviviridae replication makes it reasonable to search for “broad-spectrum” antivirals.
Materials and Methods
The half-maximal cytotoxic concentration (CC50) of candidate inhibitors was calculated by Cell Titer-Glo cell viability assay. We determined the drug concentration inhibiting 50% of viral replication (IC50) of ZIKV, DENV and/or WNV by infection of Huh7 (hepatoma cell line) at a multiplicity of infection (MOI) of 0.005 (DENVZIKV) or 0.0025 (WNV) for 1 h and at the end of incubation treating Huh7 cells with serial dilutions of candidate compound at 37°C and 5% CO2. After 72 h (DENV-ZIKV) or 48h (WNV), the IC50 of compounds interfering with the virus life cycle up to protein production, but not at later steps, was directly measured by immune-detection assay (direct yield reduction assay, DYRA).
Otherwise, to determine the impairment of viral replicative capacity exerted at late steps of viral replication, e.g. viral assembly and budding, we performed an additional replicative cycle or by infection of pre-seeded Huh7 (Secondary yield reduction assay, SYRA) with supernatants obtained by first round of infection or by Plaque reduction assay (PRA) as previously described (Vicenti et al., 2018). Selectivity indexes (SI) were calculated as ratio between CC50 and IC50. For in vitro ZIKV resistance selection to sofosbuvir, ZIKV was propagated in the Huh-7 cell line with increasing
concentrations of sofosbuvir. Viral clones replicating at each drug increment step were collected and sequenced to detect emergent mutations in the polymerase (NS5) region and sofosbuvir IC50 was measured by DYRA.
Results and discussion
Evaluation of anti-DENV compounds targeting cellular DEAD-box 3 RNA helicase. Asp-Glu-Ala-Asp (DEAD)-box polypeptide 3 (DDX3) belongs to a family of ATP-dependent RNA helicases and is involved in many aspects of RNA metabolism as well as potentially participating to the antiviral innate immune signaling pathways. On the other hand, many studies highlight DDX3 as an essential host factor for the replication of clinically relevant viruses. As part of the activities planned in the UNAVIR and PANVIR project and in collaboration with First Health Pharmaceuticals, we evaluated the effect of DDX3 helicase inhibitors focusing on antiviral activity against DENV. Overall we tested 51 compounds, 31 showed anti-DENV activity and among these 11 molecules showed promising antiviral activity with median SI 66 (IQR 59-74). Overall, the preliminary data obtained so far support targeting DDX3 protein as a potentially effective strategy for inhibition of DENV replication and feasible broad-spectrum option to minimize the possibilities of generating resistance. The evaluation of the mechanism of action of a DDX3 inhibitor compound are currently under evaluation.
Evaluation of candidate antivirals agents targeting viral entry/fusion.
Virus entry by enveloped viruses is dependent not only on cellular receptors but also on cellular lipids playing multifaceted roles in viral infections as structural components and as necessary cofactors for viral replication. In this scenario, the possibility to identify broad-spectrum antiviral molecules acting on viral envelopes is of particular interest. We tested derivatives entry inhibitors of the previously identified MAS family (Cagno et al., 2018; Tintori et al., 2018) expected to affect virus-cell membrane fusion during DENV and ZIKV infection. We evaluated the
antiviral activity of MAS compounds adapting DYRA and incubating Huh7 cells with serial dilution of MAS molecules for 30 minutes before infection with ZIKV or DENV. Of the ten compounds investigated, five showed antiviral activity both against ZIKV (median SI 16 μM; IQR 12-26) and DENV (median SI 7; IQR 6-14), 3 showed antiviral activity against ZIKV in DYRA (median SI 8; IQR
6.5-17) and anti-DENV activity in SYRA (median SI 11; IQR 9-14), while 2 compounds were completely inactive . Interestingly, the three compound active only against ZIKV were found active also against DENV in SYRA (median SI 11; IQR 9-14). We further evaluated the antiviral activity of MAS9 showing IC50 values of 2.1±1.6 (SI 14) and 2.6±2.2 (SI 12) for DENV and ZIKV, respectively. The evaluation of the mechanism of action confirmed the antiviral activity of MAS9 in viral entry/fusion step of viral replication and through a higher selectivity for viral membranes. These preliminary results support the strategy to target selectively the viral membrane, possibly based on the efficiency of the repair activity of host cell, but not virus, membranes. This class of compounds warrants further investigations to prove and characterize the mechanism of action and the ability to inhibit different emerging enveloped viruses.
Evaluation of candidate anti-flaviviral agents targeting the NS3-NS5 interaction.
A family of 2,6-diaminopurine derivatives targeting a conserved allosteric pocket on DENV/ZIKV NS5 polymerase, which is required to bind NS3 and generate the functional replication complex, has been recently discovered (Vincettiet al., 2019, 2015). Herein, we analysed a new series of derivatives molecules structurally modified to increase the affinity for the allosteric pocket on NS5 and reduce their cellular toxicity. Of the 21 derivatives compounds investigated against ZIKV and DENV, 5 were cytotoxic, 16 showed anti-ZIKV activity (median SI 9 [IQR 7-26.5]) and 13 showed anti-DENV activity (median SI 11 [IQR 6-13]) in SYRA. The best SI was obtained for compound MR333 with SI of 182 and 77 for ZIKV and DENV, respectively. Moreover, MR333 was found to be active also against WNV with comparable antiviral activity in PRA and SI of 55. This class of compounds appears to be attractive and warrants further evaluation of the mechanism of action and the genetic barrier to the emergence of resistance mutations. Biochemical assays investigating MR333 are underway to confirm and characterize the expected inhibition of multiple viruses based on binding to the highly conserved pocket on the thumb of Flavivirus polymerases.
Characterization of in vitro ZIKV resistance to sofosbuvir.
Given the high degree of NS5 homology observed
among members of the Flaviviridae family (Boldescu et al., 2017; Lim et al., 2013), sofosbuvir has been recently evaluated as an anti-Flavivirus lead candidate. Indeed, the anti-ZIKV activity of sofosbuvir has been showed in vitro with cell-based assay and in animal models. However, sofosbuvir drug genetic barrier has been not yet evaluated with ZIKV. The virus breakthrough time grew with increasing sofosbuvir concentration of 5, 10, 20 and 40 μM (5, 15, 22 and 40±9 days, respectively) with exception of 80 μM (20±2 days). No sequence variations were found up to
20 μM sofosbuvir, while the mutations V360L and V607I were selected in presence of 40 μM sofosbuvir and 80 μM. The mutations C269Y and H289T were individually selected in two experiments with 80 μM sofosbuvir. Globally, majority of mutations observed in Sanger sequencing were confirmed by NGS with addition of N407T, T833I, K834C and W835R mutations which were not associated to sofosbuvir drugpressure. By DYRA we demonstrated the reduced susceptibility to sofosbuvir of viruses carrying the C269Y, V360L and V607I mutations. Moreover, the analysis of NS5 gene showed that the V607I is located near the well-known mutation S282T in SGxxxT consensus sequence of HCV NS5B, within the motif B, and is implicated in drug resistance of HCV toward nucleotide inhibitors (Gane et al., 2016). Interestingly, the V360L mutation is located in a well-known stretch of amino acids termed β-nuclear localization sequence (positions 320-368), whereas, the C269Y is located in the poorly conserved 10-residue linker domain (aminoacidic positions 263 to 272) which is essential for the adequate NS5 conformation. Therefore, the mutations detected are probably related to emergence of ZIKV resistance to sofosbuvir in vitro and, certainly, require further biochemical investigations.
References
Boldescu, V., Behnam, M.A.M., Vasilakis, N., Klein, C.D., 2017. Broad-spectrum agents for flaviviral infections: Dengue, Zika and beyond. Nat. Rev. Drug Discov. https://doi.org/10.1038/nrd.2017.33Cagno, V., Tintori, C., Civra, A., Cavalli, R., Tiberi, M., Botta, L., Brai, A., Poli, G., Tapparel, C., Lembo, D.,
Botta, M., 2018. Novel broad spectrum virucidal molecules against enveloped viruses. PLoS One 13, 1– 18. https://doi.org/10.1371/journal.pone.0208333
Gane, E.J., Shiffman, M.L., Etzkorn, K., Morelli, G., Stedman, C., Davis, M.N., Hinestrosa, F., Dvory-Sobol, H., Huang, K.C., Osinusi, A., McNally, J., Brainard, D., McHutchison, J., Thompson, A., Sulkowski, M., 2016. Sofosbuvir/Velpatasvir in Combination with Ribavirin for 24 Weeks is Effective Retreatment for Patients who failed Prior NS5A Containing DAA Regimens: Results of the GS-US-342-1553 Study. J.Hepatol. 64, S147–S148. https://doi.org/10.1016/s0168-8278(16)00037-4
Lim, S.P., Koh, J.H.K., Seh, C.C., Liew, C.W., Davidson, A.D., Chua, L.S., Chandrasekaran, R., Cornvik, T.C., Shi,P.Y., Lescar, J., 2013. A crystal structure of the dengue virus non-structural protein 5 (NS5) polymerase delineates interdomain amino acid residues that enhance its thermostability and de novo initiation activities. J. Biol. Chem. 288, 31105–31114. https://doi.org/10.1074/jbc.M113.508606
Tintori, C., Iovenitti, G., Ceresola, E.R., Ferrarese, R., Zamperini, C., Brai, A., Poli, G., Dreassi, E., Cagno, V., Lembo, D., Canducci, F., Botta, M., 2018. Rhodanine derivatives as potent anti-HIV and anti-HSV microbicides. PLoS One 13, 1–19. https://doi.org/10.1371/journal.pone.0198478
Vicenti, I., Boccuto, A., Giannini, A., Dragoni, F., Saladini, F., Zazzi, M., 2018. Comparative analysis of different cell systems for Zika virus (ZIKV) propagation and evaluation of anti-ZIKV compounds in vitro. Virus Res. 244, 64–70. https://doi.org/10.1016/j.virusres.2017.11.003
Vincetti, P., Caporuscio, F., Kaptein, S., Gioiello, A., Mancino, V., Suzuki, Y., Yamamoto, N., Crespan, E., Lossani, A., Maga, G., Rastelli, G., Castagnolo, D., Neyts, J., Leyssen, P., Costantino, G., Radi, M., 2015. Discovery of Multitarget Antivirals Acting on Both the Dengue Virus NS5-NS3 Interaction and the Host Src/Fyn Kinases. J. Med. Chem. 58, 4964–4975. https://doi.org/10.1021/acs.jmedchem.5b00108
Vincetti, P., Kaptein, S.J.F., Costantino, G., Neyts, J., Radi, M., 2019. Scaffold Morphing Approach to Expand the Toolbox of Broad-Spectrum Antivirals Blocking Dengue/Zika Replication. ACS Med. Chem. Lett. 10, 558–563. https://doi.org/10.1021/acsmedchemlett.8b0058
Ideal exhaustiveness and limit theorems for l-group-valued measures
No full textIn this paper we present some results about existence and sigma-additivity of suitable limit measures, taking values in l-groups, in the setting of ideal convergence. We use the tool of ideal exhaustiveness, extending some earlier results, which were given in the real setting
Modes of ideal continuity of l-group-valued measures
No full textIn this paper we deal with
(ideal) continuity of lattice
group-valued finitely additive measures, and prove
some basic properties and comparison results. We
investigate the relations between
different modes of ideal continuity, and give
some characterization.
Finally we pose some open problems
Limit theorems in l-groups with respect to D-convergence
No full textSome Schur, Vitali-Hahn-Saks and Nikodym convergence theorems for l-group-valued measures are given in the context of (D)-convergence. We consider both the sigma-additive and the finitely additive case. The pointwise convergence of the measures involved is assumed to be with respect to a common regulator, while the concepts of sigma-additivity and strong boundedness are formulated similarly as the corresponding classical ones (and not with respect to a same regulator)
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