Trypsin-dependent hemagglutination of erythrocytes of a variety of mammalian and avian species by Alkhumra hemorrhagic fever virus.

Alkhumra hemorrhagic fever virus (AHFV) is an emerging flavivirus that was discovered in 1994-1995 in Saudi Arabia. Clinical manifestations of AHFV infection include hemorrhagic fever, hepatitis, and encephalitis, with a reported mortality rate as high as 25 %. Biological characteristics of this virus have not been well defined. Agglutination of erythrocytes (hemagglutination) is a laboratory tool for studying the attachment of viruses to cellular receptors. The envelope protein contains sites for attachment to host receptors to initiate the process of infection and is thus an essential component of the virion. In the present study, we examined the ability of AHFV to agglutinate erythrocytes of 13 mammalian and avian species (human group O+, camel, cow, sheep, goat, rabbit, guinea pig, mouse, rat, chicken, duck, goose and turkey) with and without trypsin-treatment. Without trypsin treatment, AHFV failed to agglutinate erythrocytes of all examined species. Following trypsin treatment, AHFV agglutinated erythrocytes of five species, namely, goose, human group O+, rat, guinea pig, and mouse, in descending order of sensitivity. This trypsin-dependent hemagglutination test has potential for use in serological and functional studies of AHFV.