An O-glycoside of sialic acid derivative that inhibits both hemagglutinin and sialidase activities of influenza viruses

The compound Neu5Ac3alphaF-DSPE (4), in which the C-3 position was modified with an axial fluorine atom, inhibited the catalytic hydrolysis of influenza virus sialidase and the binding activity of hemagglutinin. The inhibitory activities to sialidases were independent of virus isolates examined. With the positive results obtained for inhibition of hemagglutination and hemolysis induced by A/Aichi/2/68 virus, the inhibitory effect of Neu5Ac3alphaF-DSPE (4) against MDCK cells was examined, and it was found that 4 inhibits the viral infection with IC50 value of 5.6 microM based on the cytopathic effects. The experimental results indicate that compound 4 not only inhibits the attachment of virus to the cell surface receptor but also disturbs the release of the progeny viruses from infected cells by inhibiting both hemagglutinin and sialidase of the influenza viruses. The study suggested that the compound is a new class of bifunctional drug candidates for the future chemotherapy of influenza.     

Possible waterborne transmission and maintenance of influenza viruses in domestic ducks.

Two duck farms in Hong Kong were examined monthly for 1 year for the occurrence and persistence of influenza viruses within the duck communities. The predominant virus in one community was H3N2, a virus antigenically related to the pandemic Hong Kong strain. This virus was isolated monthly throughout the year from feces or pond water or both, indicating a cycle of waterborne transmission. Viruses of the same antigenic combination were isolated 1 and 2 years after the last sampling occasion, implying persistence in the community. Infection was asymptomatic. Maintenance of virus appeared to be dependent upon the continual introduction of ducklings susceptible to infection onto virus-contaminated water; the feces of ducks 70 to 80 days old were generally free of detectable virus despite the exposure of the ducks to virus in pond water. In the second community, in which ducklings were not introduced after the initial sampling, the prevailing viruses, H7N1 and H7N2, also present asymptomatically, ceased to be detected once the ducks were 70 to 80 days old. The normal practice of raising ducks of different ages on the same farm, wherein the water supplies are shared, as typified by the first community, appears to be instrumental in maintaining a large reservoir of influenza viruses in the duck population of southern China.     

Avirulent Avian Influenza Virus as a Vaccine Strain against a Potential Human Pandemic

In the influenza H5N1 virus incident in Hong Kong in 1997, viruses that are closely related to H5N1 viruses initially isolated in a severe outbreak of avian influenza in chickens were isolated from humans, signaling the possibility of an incipient pandemic. However, it was not possible to prepare a vaccine against the virus in the conventional embryonated egg system because of the lethality of the virus for chicken embryos and the high level of biosafety therefore required for vaccine production. Alternative approaches, including an avirulent H5N4 virus isolated from a migratory duck as a surrogate virus, H5N1 virus as a reassortant with avian virus H3N1 and an avirulent recombinant H5N1 virus generated by reverse genetics, have been explored. All vaccines were formalin inactivated. Intraperitoneal immunization of mice with each of vaccines elicited the production of hemagglutination-inhibiting and virus-neutralizing antibodies, while intranasal vaccination without adjuvant induced both mucosal and systemic antibody responses that protected the mice from lethal H5N1 virus challenge. Surveillance of birds and animals, particularly aquatic birds, for viruses to provide vaccine strains, especially surrogate viruses, for a future pandemic is stressed.     

Duck and human pandemic influenza A viruses retain sialidase activity under low pH conditions

The majority of influenza A viruses isolated from wild birds, but not humans, can replicate in the duck intestinal tract. Here we demonstrate that all duck isolates tested universally retain sialidase activities under low pH conditions independent of their neuraminidase (NA) subtypes. In contrast, the sialidase activities of most isolates from humans and pigs practically disappear below pH 4.5, with the exception of four human pandemic viruses isolated in 1957 and 1968. Sequence comparisons among duck, human, and swine N2 NA subtypes indicate that amino acids at positions 153, 253, 307, 329, 344, 347, 356, 368, 390, and 431 may be associated with the low pH stability of duck and human pandemic N2 NAs. This finding suggests that the low pH stability of duck influenza A virus NA may be a critical factor for replication in the intestinal tract through the digestive tract of ducks, and that the properties of NAs are important for understanding the epidemiology of the influenza virus.     

Identification of a 23S rRNA Gene Mutation in Clarithromycin-Resistant Helicobacter pylori

Background Transition mutations (A-G) at residue 2143, cognate to position 2058 in the Escherichia coli 23S rRNA gene, have been shown to confer resistance to macrolides in Helicobacter pylori. This study reports the finding that transversion mutations (A-C) can occur at 2143 as well.
Materials and Methods. Three clarithromycin-resistant H. pylori isolated from three different patients after treatment with clarithromycin were analyzed for point mutations by cycle sequencing of a 163-bp amplified region surrounding residue 2143 within the conserved loop of the 23S rRNA gene.
Results. Nucelotide sequence comparisons of a 163-bp amplified product revealed that A-C transversion mutations occurred at position 2143. H. pylori isolated from the patients prior to treatment were susceptible to clarithromycin and displayed no polymorphism at 2143.
Conclusion. This is the first report to show that A-C transversion mutations at position 2143 can confer resistance to clarithromycin in H. pylori and further support the role that mutations at position 2143 play in conferring macrolide resistance in H. pylori.     

Cocultivation of avian orthomyxoviruses and paramyxoviruses in embryonated eggs: implications for surveillance studies.

A relatively inexpensive flow microcalorimeter is described which is capable of detecting heat outputs as low as 3 μW (precision, ±2%). Its use is illustrated on river epilithon (0.8 to 6.8 μW cm⁻²), river sand (9.8 μW cm⁻³), and marine sand (15.3 μW cm⁻³); however, it could be used to detect the heat output from any biotic material over which a flow of water can be passed, provided that such an action would not be disruptive to chemical and biological equilibria.     

Isolation of a putative phospholipase C gene of Drosophila, norpA, and its role in phototransduction

Severe norpA mutations in Drosophila eliminate the photoreceptor potential and render the fly completely blind. Recent biochemical analyses have shown that norpA mutants lack phospholipase C (PLC) activity in the eye. A combination of chromosomal walking and transposon-mediated mutagenesis was used to clone the norpA gene. This gene encodes a 7.5 kb RNA that is expressed in the adult head. In situ hybridizations of norpA cDNA to adult tissue sections show that this gene is expressed abundantly in the retina. The putative norpA protein is composed of 1095 amino acid residues and has extensive sequence similarity to a PLC amino acid sequence from bovine brain. We suggest that the norpA gene encodes a PLC expressed in the eye of Drosophila and that PLC is an essential component of the Drosophila phototransduction pathway.