Latency-associated human cytomegalovirus glycoprotein N genotypes in monocytes from healthy blood donors.

BACKGROUND: The beta-herpesvirus human cytomegalovirus (HCMV) infects a variety of cell types and maintains a lifelong relationship with its host by way of a latent infection in circulating monocytes, myeloid precursor cells, and the hematopoietic progenitor population. Viral strain heterogeneity, shown by gene polymorphisms, has been implicated in the majority of HCMV biologic behaviors. HCMV UL73 encodes the polymorphic envelope glycoprotein N (gN), which shows seven genotypes (gN-1, gN-2, gN-3a, gN-3b, gN-4a, gN-4b, and gN-4c). STUDY DESIGN AND METHODS: Monocyte subfractions from 64 HCMV-seropositive healthy blood donors were collected to analyze gN genotypes distribution in the few cells harboring the latent viral genome. Different experimental approaches to extract viral genomes from the monocyte population and amplify UL73 (polymerase chain reaction touchdown and nested) for subsequent genotyping were tested and compared with diagnostic gold standard. gN genotype distribution in monocytes from immunocompetent healthy carriers was compared with previously reported data obtained from patient populations with acute HCMV infections. RESULTS: The efficiency of UL73 amplification from monocytes of healthy seropositive blood donors was approximately 39 percent, one of the highest reported to date. The leading gN genotype was gN-1 (87%), whereas the gN-4 variant was poorly represented (13%). The comparison of gN genotypic frequencies in the immunocompetent healthy population with immunocompromised patients is discussed. CONCLUSIONS: This work further supports the idea that strain-specific features could determine the cell tropism and influence the onset of latency.