Analysis of cytomegalovirus resistance mutations and clinical features of CMV infection in immunocompromised children

Objective.

To determine frequency and spectrum of cytomegalovirus (CMV) resistance mutations to antiviral drugs in immunocompromised children. To study clinical course of resistant CMV infection in this patient population.

Materials and Methods.

This prospective study included 120 patients of the Dmitry Rogachev NMRC PHOI who mainly were recipients of allogeneic hematopoietic stem cell transplantation (HSCT) with confirmed CMV infection (median age – 8.9 years). The study inclusion criterion was the possible development of CMV drug resistance. With an increase in the CMV blood viral load (determined by real-time polymerase chain reaction), UL97 and UL54 genes mutations associated with CMV resistance to antiviral drugs (using Sanger sequencing) were studied.

Results.

Of 120 patients, 27 (22.5%) were found to have resistant CMV strains. The following mutations and their combinations were identified in CMV pUL97 protein kinase: A594V (n = 8), L595S (n = 6), H520Q (n = 2), A591V (n = 1), C592G (n = 1), C592S (n = 1), C607F (n = 1), C607Y (n = 1), C603W (n = 1), A594V/H520Q (n = 2), L595F/C592G (n = 1), L595S/M460V (n = 1); in the DNA polymerase pUL54: N408D (n = 1), V715H (n = 1), V781I/K513R (n = 1), L773V (n = 1). The most common mutations were A594V (37%) and L595S (27%). The median time from the start of antiviral therapy to the detection of a resistance mutation was 108 days (11-306 days). The following features were recorded in patients with CMV resistance mutations: higher values of peak viral load in the blood (p = 0.005), longer viral elimination (p = 0.001), and more frequent development of invasive fungal infections (p = 0.001). The overall survival rate in this group of patients was 60% versus 79% in patients without resistance mutations (p = 0.074).

Conclusions.

Frequency and spectrum of mutations responsible for CMV drug resistance in immunocompromised children have been determined. The most common mechanisms of CMV resistance to ganciclovir were A594V and L595S mutations of protein kinase pUL97. pUL54 mutations were detected less frequently and represented by the following: N408D, V781I, V715H and L773V. It is necessary to emphasize the importance of timely detection of resistant strains and adjustment of treatment strategy due to a more severe course of the disease when CMV resistance mutations are presented: longer viral persistence, increased incidence of fungal infections, decreased overall survival.