Restriction digest patterns for gB types 1-4: Digestion with Rsa1 distinguishes types 1 and 2 from 3 and 4, whereas digestion with Hinf1 distinguishes 1 from 2 and 3 from 4. All lysates from four patients were amplified with primers gB1292 × gB1676. Aliquots of the first round of PCR were then amplified with primers gB1292 × gB1613. Products of the second round of amplification were digested with Rsa1 or Hinf1. Restriction digests were resolved on 10% polyacrylamide gels and stained with ethidium bromide. φχ176 HaeIII marker DNA was used to estimate molecular weight (lanes not shown). The DNA used for PCR template for gB types 1-3 were obtained from clinical isolates propagated on foreskin fibroblasts. The gB type 4 PCR product was directly amplified from cells harvested from a long-term marrow culture established from a patient with graft failure.