Screening for lead compounds and herbal extracts with potential anti-influenza viral activity.

Nonstructural protein 1 (NS1) of the highly pathogenic avian influenza virus (H5N1) contains a conserved RNA binding domain (RBD) that inhibits antiviral functions of host-innate immune response. Dimerization of NS1 forms a central groove and binds to double stranded (ds) RNA. This region might serve as a potential drug target. In this study, three dimensional structure model of NS1 RBD protein was constructed and virtual screening was performed to identify lead compounds that bound within and around the central groove. The virtual screening showed that 5 compounds bound within the central groove with binding energy ranging between -16.05 and -17.36 Kcal/mol. Two commercially available compounds, estradiol and veratridine, were selected for using in an in vitro screening assay. The results showed that neither of the compounds could inhibit the association between dsRNA and NS1 RBD protein. In addition, 34 herbal extracts were examined for their inhibitory effects. Five of them were able to inhibit association between NS1 RBD and dsRNA in electrophoresis mobility shift assay. Four herbs, Terminalia belirica, Salacia chinensis, Zingiber montanum and Peltophorum pterocarpum, could reduce > 50% of infectivity of H5N1 in a cell-based assay, and it is worth further studying their potential use as source of antiviral drugs.

Dengue virus neutralization and antibody-dependent enhancement activities of human monoclonal antibodies derived from dengue patients at acute phase of secondary infection.

Public health concern about dengue diseases, caused by mosquito-borne infections with four serotypes of dengue virus (DENV-1-DENV-4), is escalating in tropical and subtropical countries. Most of the severe dengue cases occur in patients experiencing a secondary infection with a serotype that is different from the first infection. This is believed to be due to antibody-dependent enhancement (ADE), by which one DENV serotype uses pre-existing anti-DENV antibodies elicited in the primary infection to facilitate entry of a different DENV serotype into the Fc receptor-positive macrophages. Recently, we prepared a number of hybridomas producing human monoclonal antibodies (HuMAbs) by using peripheral blood lymphocytes from Thai patients at acute phase of secondary infection with DENV-2. Here, we characterized 17 HuMAbs prepared from two patients with dengue fever (DF) and one patient with dengue hemorrhagic fever (DHF) that were selected as antibodies recognizing viral envelope protein and showing higher neutralization activity to all serotypes. In vivo evaluation using suckling mice revealed near perfect activity to prevent mouse lethality following intracerebral DENV-2 inoculation. In a THP-1 cell assay, these HuMAbs showed ADE activities against DENV-2 at similar levels between HuMAbs derived from DF and DHF patients. However, the F(ab')2 fragment of the HuMAb showed a similar virus neutralization activity as original, with no ADE activity. Thus, these HuMAbs could be one of the therapeutic candidates against DENV infection.

Comparative studies on the pathological findings and mortality in Schistosoma mansoni infected mice after treatment with artesunate and the current antischistosomal drugs.

The effect of artesunate (ART) on the pathology and mortality rate of in Schistosoma mansoni infected mice was comparatively studied with the current drugs of choice for the treatment of schistosomiasis mansoni: praziquantel (PZQ) and oxamniquine (OX). S. mansoni experimentally infected mice were treated at 9th week of infection with ART, PZQ or OX at an oral dosage of 300 mg kg(-1), 600 mg kg(-1) and 100 mg kg(-1), respectively. Untreated, infected mice and non-infected mice were added as controls. Samples of mice were sacrificed and examined for the pathological findings at 1 week, 1 month, and 3 months after treatment. At 1 week after treatment, both gross and microscopic lesions were observed. No significant differences were noted among the infected groups. Differences were observed at 1 month after treatment. The lesions decreased more rapidly in groups treated with PZQ and OX. At 3 months after treatment, there were significant differences in the pathological findings among groups. In the groups treated with PZQ and OX, the lesions were markedly reduced and rarely found, but they were clearly observed in the group treated with ART and in the untreated, infected group. High mortality was also recorded in the group treated with ART and in the untreated, infected group. Therefore, the treatment of S. mansoni infected mice at 9 weeks of infection with ART did not reduce the pathological findings or the mortality rate compared to treatment with the current recommended schistosomicides, PZQ and OX.