Coinfection of the immunocompromised but not the immunocompetent host by multiple human cytomegalovirus strains.

Coinfection by multiple human cytomegalovirus (HCMV) strains was investigated in immunocompetent individuals and AIDS patients. Thirty HCMV maternal and fetal or newborn isolate pairs from 9 cases of congenital HCMV infection as well as 36 HCMV isolates and 2 PCR-HCMV-positive CSF samples from 13 AIDS patients were tested by restriction fragment length polymorphism analysis of multiple genome regions. Results from the group of congenital infections showed that: i) all the 9 women with primary HCMV infection presumably harboured a single HCMV strain; ii) all strains were genetically unrelated; iii) isolates from infected fetuses or newborns consisted of a single strain apparently indistinguishable from the maternal strain; iv) no strain variations were observed in isolates from different body sites or in sequential isolates from newborns up to 8 months after birth. Results from the AIDS patient group demonstrated that; i) all patients were infected by unrelated strains; ii) 6/13 (46.1%) patients were coinfected by 2 or more HCMV strains; iii) in a single patient two different HCMV strains were detected in blood and urine, respectively, whereas a mixture of the two was found in the pharynx; iv) 4 patients showed the sequential appearance of a mixed virus population or different strains suggesting sequential reinfections.