DIFFERENTIATION OF VARICELLA VACCINE FROM WILDSTRAINS

Abstract

Varicella vaccine (VV) recipients have occasionally developed significant illness following immunization. It is necessary to ascertain whether these illnesses are produced by VV or by natural infection. Virus was isolated from one vaccine recipient 26 and 28 days post immunization. These isolates, (Lo26 and Lo28) were tested together with early and late passage vaccine, (Oka) strain; 3 wild isolates; and a laboratory, (Ellen) strain. VZ infected cells were lysed and then treated to remove normal cell components. The virus was then treated with SDS to release viral DNA which was purified and digested with a variety of restriction enzymes (RE). The digests were electrophoresed in agarose gels containing ethidium bromide. Two types of patterns were observed. One, found with several enzymes, revealed minor changes reflecting previously described variable regions. The second, seen only with Pst 1, clearly differentiated vaccine and Lo26 and Lo28 from the others. Differences observed appear to result from the deletion of a Pst 1 RE site in the long segment of vaccine VZ DNA. This change was already present in early passage of the Oka strain while the Ellen strain retained this site despite over 150 tissue culture passages. Pst 1 characterization of VZ DNA obtained from isolates will be useful in determining whether rashes in vaccinees or their contacts are due to vaccine or result from unrecognized wild VZ infection. It will also help to characterize isolates from vaccinees who develop zoster.