Analysis of the Variability of Epstein-Barr Virus Genes in Infectious Mononucleosis: Investigation of the Potential Correlation with Biochemical Parameters of Hepatic Involvement

Abstract

Background: Primary Epstein-Barr virus (EBV) infection is usually asymptomatic, although at times it results in the benign lymphoproliferative disease, infectious mononucleosis (IM), during which almost half of patients develop hepatitis. The aims of the present study are to evaluate polymorphisms of EBV genes circulating in IM isolates from this geographic region and to investigate the correlation of viral sequence patterns with the available IM biochemical parameters.

Methods: The study included plasma samples from 128 IM patients. The genes EBNA2, LMP1, and EBNA1 were amplified using nested-PCR. EBNA2 genotyping was performed by visualization of PCR products using gel electrophoresis. Investigation of LMP1 and EBNA1 included sequence, phylogenetic, and statistical analyses.

Results: The presence of EBV DNA in plasma samples showed correlation with patients' necessity for hospitalization (p=0.034). The majority of EBV isolates was genotype 1. LMP1 variability showed 4 known variants, and two new deletions (27-bp and 147-bp). Of the 3 analyzed attributes of LMP1 isolates, the number of 33-bp repeats less than the reference 4.5 was the only one that absolutely correlated with the elevated levels of transaminases. EBNA1 variability was presented by prototype subtypes. A particular combination of EBNA2, LMP1, and EBNA1 polymorphisms, deleted LMP1/P-thr and non-deleted LMP1/P-ala, as well as genotype 1/ 4.5 33-bp LMP1 repeats or genotype 2/ 4.5 33-bp LMP1 repeats showed correlation with elevated AST (aspartate aminotransferase) and ALT (alanine transaminase).

Conclusions: This is the first study which identified the association between EBV variability and biochemical parameters in IM patients. These results showed a possibility for the identification of hepatic related diagnostic EBV markers.

Keywords: EBV; LMP1; gene polymorphism; infectious mononucleosis; transaminase.

Figure 1

Identification of EBV genotypes 1 and 2 in gel electrophoresis: genotype 1 positive samples 1–4 and 6–8; genotype 2 positive sample – 9; negative samples 5 and 10–14; L – 100-bp standard; PC – positive control of 596-bp fragment from the first PCR reaction; PC1 – positive control of 497-bp fragment for genotype 1; PC2 – positive control of 150-bp fragment for genotype 2; NC – negative control.

Figure 2

Phylogenetic tree of the C-terminus of LMP1. Thirty-three 506-bp fragments of LMP1 IM sequences and 13 sequences obtained from GenBank/EMBL7DDBJ database.

Figure 3

Distribution of the number of 33-bp LMP1 repeats (3-6) in IM patients with different AST and ALT levels.

Figure 4

Phylogenetic tree of the C-terminus of EBNA1. Thirty-one 329-bp fragments of EBNA1 IM sequences and 10 sequences obtained from GenBank/EMBL7DDBJ database.