Classification of Trachoma Virus Strains by Protection of Mice from Toxic Death

Abstract

Summary Twenty-nine trachoma virus strains isolated on Taiwan and nine trachoma strains and two inclusion conjunctivitis strains obtained from other areas of the world have been tested in mice for cross-protection against intravenous toxicity. Crude yolk sac suspensions of these TRIC viruses were used both for protection and challenge. Protection was produced by intravenous injection of one-third and then two-thirds a minimum lethal toxic dose 14 and 7 days prior to challenge. All 29 of the Taiwan trachoma strains fell into one of two cross-protecting groups designated as the TW-1 and TW-3 groups. Three trachoma strains from New Delhi protected against each other and members of the TW-3 group. Two trachoma strains from Apache Indians in Arizona cross-protected with the TW-1 group. A Saudi Arabia and a Gambia trachoma strain protected against each other but not against the other strains tested. Two trachoma and two inclusion conjunctivitis strains failed to cross-protect with any strain. Therefore, seven different cross-protecting types were demonstrated. It is concluded that the total number of different groups of TRIC virus strains in the mouse toxicity prevention test are not yet known, but that in a given geographic area (as exemplified by Taiwan with two groups) the number of different groups is limited.