Structure of Nine Arboviruses

During our investigation of the structure of arboviruses (Bergold, Graf & Munz, 1966; Bastardo, Bergold & Munz, 1968) 9 more viruses have been studied (Table 1). Serological tests kindly done by the Trinidad Regional Virus Laboratory (TRVL) and the Middle American Research Unit (Maru) in Panama helped to confirm the identity of the viruses. Viruses were grown in roller flasks in BHK 21 cells and titrated by plaquing in the same cells, using a serum-free maintenance medium (Bergold & Mazzali, 1968). The viruses were concentrated (400 ×) and purified by centrifugation (Bergold et al. 1966; Bastardo et al. 1968). Only two high-speed centrifugations were done with most viruses (Table 2) because the additional cycle caused considerable loss of infectivity. For electron-microscopy the virus samples were mixed (1 + 1) with sodium phosphotungstate (pH 7) and glycerol (1 + 2) was added (Horne, 1965).