Zanamivir, a neuraminidase inhibitor, has shown promise as a drug to control influenza. During prolonged treatment with zanamivir, a mutant virus was isolated from an immunocompromised child infected with influenza B virus. A hemagglutinin mutation (198 Thr-->Ile) reduced the virus affinity for receptors found on susceptible human cells. A mutation in the neuraminidase active site (152 Arg-->Ly...

A kininogenin (EC 3.4.21.8) was purified from the venom of Vipera ammodytes ammodytes (European sand viper) by a combination of gel filtration and ion-exchange chromatography. The enzyme is approximately six times more active than bovine trypsin in its ability to release vasoactive peptides from a plasma precursor. The kininogenin is a glycoprotein containing 18-20% by weight of carbohydrate. I...

Amino acid substitutions within or near the active site of the viral neuraminidase (NA) may affect influenza virus fitness. In influenza A(H3N2) and B viruses circulating in Thailand between 2010 and 2015, we identified several NA substitutions that were previously reported to be associated with reduced inhibition by NA inhibitors (NAIs). To study the effect of these substitutions on the enzyma...

The increasing use of influenza virus neuraminidase (NA) inhibitors (NIs) necessitates the development of reliable methods for assessing the NI susceptibility of clinical isolates. We evaluated three NA inhibition assays against a panel of five clinical isolates each of influenza virus A/H1N1, A/H3N2, and B strains and four viruses with a defined resistance genotype (R292K, H274Y, R152K, and E1...

Purified gp71 of Friend murine leukemia virus (FLV) can interfere with virus infection, absorb neutralizing antibody, and in the presence of group-specific anti-gp71 antibody, hemagglutinate sheep erythrocytes. Interference by FLV gp71 with several murine leukemia viruses (MuLV) was tested in the XC and S + L- assay systems. Treatment of gp71 with trypsin or Pronase eliminated its interfering c...

The effect of strong electrolyte upon the activity of Vibrio cholerae neuraminidase (VC neuraminidase) toward the surface of intact cells and toward their isolated, purified sialolipid components, was studied in detail. A linear dependence of the logarithm of initial velocity on the square root of ionic strength was observed for purified GM8 over a concentration range of 0 to 0.05 M NaCl in 0.0...

Pterocarpans (1-3) and flavanones (4-10) were isolated from Sophora flavescens and screened for their ability to inhibit neuraminidase (an enzyme crucial in the proliferation of the influenza virus). The majority of inhibitors were shown to have IC(50) values of 20 microM or below. Interestingly, pterocarpan 1 emerged as the best inhibitor with an IC(50) of 1.4 microM. We were thus able to prov...

We examined 19 hepatoma tissues for alkaline phosphatase isoenzyme and found that six have both the Kasahara isoenzyme and an alkaline phosphatase with a unique electrophoretic mobility, in addition to the liver-type enzyme. From two of six carcinoma tissues, the abnormal enzyme was partly purified and subjected to a detailed analysis, which clarified that the abnormal enzyme resembled a fetal ...

Influenza is a major cause of severe respiratory infections leading to excessive hospitalizations and deaths globally; annual epidemics, pandemics, and sporadic/endemic avian virus infections occur as a result of rapid, continuous evolution of influenza viruses. Emergence of antiviral resistance is of great clinical and public health concern. Currently available antiviral treatments include fou...

Antibody directed against the neuraminidase of an influenza virus did not prevent attachment of the virus to red cells, but strongly inhibited elution of the virus from these cells. The virus used in these experiments had approximately 5o0 enzyme antigenic sites on the surface of each particle. In the presence of sufficient antibody to combine with all of these sites there was no measurable elu...