An unmanned, towable aerovehicle is described and includes a container or frame to hold or support cargo, at least one and, in some examples, a plurality of autogyro assemblies connected to the container and to provide flight characteristics, and a controller to control operation the autogyro assembly for unmanned flight. Silica-stabilized alumina powder, prepared by spray drying of bayerite powder, precipitating silica in a bayerite slurry with an acid, or impregnation or co-extrusion of bayerite with sodium silicate solution was found to be a superior catalyst support precursor. The characteristic antigens which can be obtained from it and which can be employed for detecting antibodies against retroviruses which are associated with immunodeficiency diseases are also disclosed, as are the DNA and amino acid sequences of the virus.