RESUMEN
The binding of dengue type 2 (DEN-2) virus to mammalian (LLC-MK(2) and Vero) and mosquito (C6/36 and AP61) cell surfaces was investigated by a virus-binding assay using purified (3)H-labeled DEN-2 virus. The DEN-2 virus binding to all four cell types was specific and saturable, indicating the presence of a single class of receptors (ranging from 3.7 x 10(3) to 3.5 x 10(4) receptors/cell) with a high affinity for DEN-2 virus (K(d) ranging from 98 to 171 pM). Treatment of cell surfaces with certain glycosidases significantly reduced virus binding to mammalian cell lines, but not to the insect cell lines examined. Furthermore, heparin was found to compete with mammalian cell receptors for binding to DEN-2 virus and to inhibit viral infection of mammalian cells, but heparin had no effect on viral binding to or infection of insect cells. These results confirm previous reports suggesting that DEN-2 virus receptors on mammalian cell lines are different from those on insect cell lines.
Asunto(s)
Virus del Dengue/fisiología , Fusión de Membrana , Animales , Línea Celular , InsectosRESUMEN
Hepatitis E virus (HEV) is an important cause of enterically transmitted hepatitis in developing countries. Sporadic autochthonous cases of hepatitis E have been reported recently in the United States and other industrialized countries. The source of HEV infection in these cases is unknown; zoonotic transmission has been suggested. Antibodies to HEV have been detected in many animals in areas where HEV is endemic and in domestic swine and rats in the United States. There is evidence supporting HEV transmission between swine and humans. Nevertheless, HEV has not been detected in wild rodents. We tested murid rodents and house shrews trapped in Nepal's Kathmandu Valley, where hepatitis E is hyperendemic, for HEV infection. The most commonly trapped species was Rattus rattus brunneusculus. Serum samples from 675 animals were tested for immunoglobulin G against HEV by enzyme-linked immunosorbent assay; 78 (12%) were positive, indicating acute or past infection. Antibody prevalence was higher among R. rattus brunneusculus and Bandicota bengalensis than in Suncus murinus. Forty-four specimens from 78 antibody-positive animals had sufficient residual volume for detection of HEV RNA (viremia) by reverse transcription-PCR. PCR amplification detected four animals (9%; three were R. rattus brunneusculus and one was B. bengalensis) with viremia. Phylogenetic analysis of the four genome sequences (405 bp in the capsid gene) recovered showed that they were identical, most closely related to two human isolates from Nepal (95 and 96% nucleotide homology, respectively), and distinct from HEV sequences isolated elsewhere. These data prove that certain peridomestic rodents acquire HEV in the wild and suggest that cross-species transmission occurs, with rodents serving as a virus reservoir for humans.