The initial steps of dengue viral entry have been divided into adsorption and penetration using acid glycine treatment to inactivate extracellular virus after attachment to baby hamster kidney (BHK) cells but prior to penetration. First, we showed that virus infection was accomplished within 2 h after adsorption. Second, the assay was used to examine the properties of dengue envelope E protein-specific monoclonal antibodies (MAbs), lectins, and heparin. We found that three MAbs, 17-2, 46-9, and 51-3, may neutralize dengue 2 virus (DEN-2) through inhibition of not only viral attachment but also of penetration. However, one MAb, 56-3.1, interfered specifically with attachment. Therefore, the functional domains of E protein involved in attachment and penetration may be different. Moreover, studies with lectins indicated that carbohydrates, especially alpha-mannose residues, present on the virion glycoproteins may contribute to binding and penetration of the virus into BHK and mosquito C6/36 cells. Finally, virus infectivity was inhibited by heparin through its blocking effects at both virus attachment and penetration. This suggests that cell surface heparan sulfate functions in both viral attachment and penetration of DEN-2 virus. In conclusion, our results further elucidated some aspects of the dengue virus entry process.

The present investigation examined whether an association exists between betel quid chewing and signs of periodontal disease and determined the prevalence of Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis by polymerase chain reaction. The periodontal status of 34 betel quid chewers and 32 non‐betel quid chewers were compared. A significantly higher prevalence of bleeding on probing was found in betel quid chewers than non‐chewers among the subjects with higher plaque level, greater gingival inflammation, deeper probing depth or greater attachment loss. Also, the results suggested that betel quid chewers may harbor higher levels of infection with A. actinomycetemcomitans and P. gingivalis than non‐betel quid chewers. The association persists after adjusting for severity of the clinical parameters. In conclusion, betel quid chewing was associated with a higher prevalence of bleeding on probing where higher clinical levels of disease existed, and with a likelihood of subgingival infection with A. actinomycetemcomitans and P. gingivalis.

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The open reading frame potentially encoding a 78 amino acid, 9101 Da hydrophobic protein (HP) and, mapping at the 3' end of the porcine transmissible gastroenteritis coronavirus (TGEV) genome, was shown to be expressed during virus replication. The cloned HP gene was placed in a plasmid under control of the T7 RNA polymerase promoter and in vitro translation of transcripts generated in vitro yielded a 9.1-kDa protein that was immunoprecipitable with porcine hyperimmune anti-TGEV serum. Antiserum raised in rabbits against a 31 amino acid synthetic polypeptide that represented the central hydrophilic region of HP specifically immunoprecipitated HP from TGEV-infected cells. HP was further shown to become associated with microsomal membranes during synthesis in vitro and was found to be closely associated with the endoplasmic reticulum and cell surface membranes in infected cells. The intracellular location of HP suggests that it may play a role in the membrane association of replication complexes or in virion assembly.

Aqueous extracts of ripe areca nut without husk (ripe ANE) and fresh and tender areca nut with husk (tender ANE) were examined for their effects on the defensive functions of human neutrophils. Exposure of peripheral blood neutrophils to ripe ANE and tender ANE inhibited their bactericidal activity against oral pathogens, including Actinobacillus actinomycetemcomitans and Streptococcus mutans, in a dose-dependent manner. At the concentrations tested, ripe and tender ANEs did not significantly affect the viability of neutrophils as verified by their ability to exclude trypan blue dye. However, both ANEs inhibited the production of bactericidal superoxide anion by neutrophils as measured by cytochrome c reduction. Moreover, the ripe ANE inhibited neutrophils more effectively than did tender ANE. Arecoline, a major alkaloid of areca nut, only exhibited an inhibitory effect on the functions of neutrophils when high concentrations were used. Therefore, arecoline could not be used to explain the inhibitory effects observed for ANEs. In conclusion, our results demonstrated that ripe and tender ANEs reduced the antibacterial activity and the superoxide anion production of neutrophils. This effect may contribute to a less efficient elimination of bacteria from the periodontal environment. Inhibition of the antimicrobial functions of neutrophils may alter the microbial ecology of the oral cavity, and this may be one possible mechanism by which areca nut compromises the oral health of users of areca nut products.