Antigenic relationships of flaviviruses with undetermined arthropod-borne status.

In contrast to most of the arthropod-borne flaviviruses, the flaviviruses with undetermined arthropod-borne status are probably disseminated only by direct contact with excreta (saliva, urine, feces, etc.); however, as yet undescribed arthropod transmission cycles may be found for some of them. Twenty-two of these flaviviruses, including prototype and recently isolated strains, were compared. Biologic properties were defined by infectivity titrations in suckling mice and Vero, LLC-MK2, and primary Pekin duck embryo cells, and antigenic relationships were defined by complement-fixation and plaque reduction neutralization tests. An antigenic classification scheme is proposed. Antigenic and biologic properties delimit two large clusters. The first, comprising a single antigenic complex, includes those which have yet to be isolated from arthropods, but are likely to be so (Israel turkey meningoencephalitis, Koutango, Negishi and Aroa viruses). The second, encompassing five antigenic complexes, is comprised of viruses which have been isolated exclusively from rodents or bats (Saboya, Carey Island, Dakar bat, Sokuluk, Bukalasa bat, Entebbe bat, Phnom Penh bat, Modoc, Sal Vieja, Jutiapa, San Perlita, Cowbone Ridge, Rio Bravo, Apoi, Tamana bat and Montana Myotis leucoencephalitis viruses) but includes three viruses (Saboya, Sokuluk and Entebbe bat viruses) which may be arthropod-borne, as indicated by replication in mosquito cells in vitro.

Evaluation of methods for chemically coupling foot-and-mouth disease virus to sheep red blood cells for immunological assays.

Six methods of chemically coupling proteins to red blood cells were evaluated for their effectiveness in coupling foot-and-mouth disease virus (FMDV) to sheep red blood cells. The coupling agents tested were potassium periodate, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (ECDI), chromium chloride, glutaraldehyde, bis-diazotized benzidine (BDB) and N-succinimidyl 3-(2-pyridyldithio) propionate (SPDP). Of these, only the coupling methods using BDB and SPDP resulted in virus-red cell complexes that reacted with FMDV antiserum in passive hemagglutination and passive immune hemolysis assays. The BDB and SPDP methods were studied further to determine optimal coupling conditions, the kinetics of coupling and the effects of chemical couplers on viral integrity. Only the FMDV-red cell complexes formed with SPDP were suitable targets for detecting FMDV antibody producing lymphocytes in a hemolytic plaque assay.