Co‐infection of two β‐herpesviruses (CMV and HHV‐7) as an increased risk factor for ‘CMV disease’ in patients undergoing renal transplantation

The ubiquity of human cytomegalovirus (CMV) and human herpesvirus‐7 (HHV‐7), as well as activation of these viruses during immunosuppression, allows the suggestion that both viruses could participate in the development of ‘CMV disease’ in patients after renal transplantation (RT). The aim of our research was to study the prevalence of latent CMV and HHV‐7 infections in patients before RT, to determine interaction between these viruses in dual infection and possible association of their reactivation with the progression of ‘CMV disease’ after RT. Peripheral blood samples were collected from 49 patients before and up to 10–12 wk after RT. The methods used for diagnostics of viral infections were: serology, nested polymerase chain reaction (nPCR) analysis of peripheral blood leukocytes (PBL) and plasma, and virus isolation in cell cultures (morphological changes, nPCR analysis of cellular and cell‐free samples, indirect immunofluorescence analysis). Before RT, CMV and HHV‐7 DNAs were detected in PBL but not in the plasma samples, which indicates the presence of latent viral infection in patients. Latent dual (CMV+HHV‐7) infection was prevalent (51.0%) in 49 patients, while CMV and HHV‐7 infections alone were detected in 26.5 and 12.2% of patients, respectively. 
Risk of viral disease after RT, for recipients with latent dual infection before RT, was 12‐ and 2.2‐fold higher in comparison with CMV and HHV‐7 infections alone, respectively. 
Frequency of dual infection in 18 recipients with ‘viral syndrome’ or ‘CMV disease’ after RT was reliably higher (13/18, 81.3%) than CMV (1/18, 6.2%) (p<0.025) and HHV‐7 (2/18, 12.5%) (p<0.025) infections alone. HHV‐7 reactivation preceded CMV reactivation in 77.0% of the cases of dual infection in the recipients with viral disease and reactivation of both viruses preceded the development of viral disease. 
Severe ‘CMV disease’ developed in 2 out of 2 recipients with CMV primary infection and ‘viral syndrome’ in 1 recipient with CMV reinfection. The reactivation of CMV was detected in all recipients prior to onset of the disease. 
Correlation was shown between reactivation of latent HHV‐7 infection and development of febrile syndrome in 2 out of 2 recipients with HHV‐7 infection alone. 
Taking into account that dual infection is an increased risk factor for ‘viral syndrome’ and ‘CMV disease’ development, screening diagnostic should include testing for both viral infections in transplant donors as well as in recipients before and after RT.