Previously unreported Arg594Lys in EBNA-1 and Leu212 in EBNA-2 among patients with EBV-associated infectious mononucleosis in Croatia

Abstract

The molecular diversity of Epstein-Barr virus (EBV) is defined by mutations in specific EBV genes and has been insufficiently studied in infectious mononucleosis (IM). The aim of this study was to determine all variations of the EBV latency genes EBNA-1, EBNA-2 and LMP-1 in pediatric patients with EBV-associated IM in Croatia, including previously defined SNPs and indels as well as previously undocumented polymorphisms. The vast majority of EBV isolates (71/72) were determined as EBV type 1 while EBNA-1 genes were classified exclusively as previously defined EBNA-1 prototypes, with 22/72 sequences categorized as P-Ala and 50/72 sequences as P-Thr. The most common LMP-1 variants included wild type (B95-8, 20/72), China1 (19/72) and recombinants (10/72). This study also described a previously undocumented polymorphism in the Arg594Lys substitution that is present in all EBNA-1 sequences examined. In addition, we found a Leu212 insertion in the EBNA-2 sequences of 50/72 isolates compared to the wild type. These polymorphisms were described for the first time in this geographic region and were not mentioned in previous studies on EBV diversity in IM. We also concluded mutual variant association between the variants using a chi-square test, in which the LMP-1 North Carolina variant was significantly more likely to appear with the EBNA-1 P-Ala prototype, while the B95-8 LMP-1 variant was significantly more likely to appear with the EBNA-1 P-Thr prototype (p < 0.05). Furthermore, leucine addition in EBNA-2 sequences is more likely to appear with LMP-1 wild type and EBNA-1 P-Thr prototype while EBV type 1 identical to the reference sequence is more likely to appear with North Carolina LMP-1 variant and EBNA-1 P-Ala prototype (p < 0.05).