Abstract
Abstract 1600
It is well known that Fc gamma receptors expressed on monocytes and macrophages enhance the presentation of antibody-bound antigens. Human Fc gamma receptors are coded by genes located on chromosome 1q23. Fc gamma RIIA (CD32) is a transmembrane protein expressed on neutrophils. Efficacy of phagocytosis by polymorphonuclear neutrophils is known to vary between allotypes of Fc gamma RIIa. Polymorphisms of Fc gamma RIIA have been linked to susceptibility to infections by encapsulated bacteria (N. meningitides, H. influenzae) and severe sepsis by several authors. Moreover, susceptibility to perinatal HIV-1 infection has been attributed to polymorphisms of Fc gamma RIIA, and this is the only association of FC gamma RIIA with viral diseases in the literature. FcγRIIA gene has two condominantly expressed alleles the 131-Arg (R131) and the 131-His (H131) allele. R131 binds IgG2 much less avidly than H131.
To propose Fc gamma RIIA polymorphisms as a genetic risk factor for acquisition and latency of EBV infection in patients with lymphoproliferative diseases.
Forty Greek patients with EBV-unrelated low grade B-cell leukemic lymphomas (chronic lymphocytic leukemia: 23, marginal zone lymphoma: 11, mantle cell lymphoma: 3, hairy cell leukemia: 2, follicular lymphoma: 1), were included in the study. Patients' sera were tested with ELISA for the presence of EBV-VCA IgG antibodies. DNA from peripheral blood was studied by quantitative real time - PCR for the EBV-R gene, while RNA from peripheral blood was studied by RT-PCR for the EBV-LMP1 oncoprotein. Genomic DNA from peripheral blood was tested for Fc gamma RIIA 131Histidin(H)/arginine(R) SNP, by PCR, followed by restriction fragment length polymprphim (RFLP) using the appropriate enzyme (BstUI, Fermentas, Vilnius, Lithuania). We used Pearson Chi-square for the statistical analysis of the results.
All but 2 patients were positive for EBV-VCA IgG antibodies. Nineteen patients (47.5%) were EBV-positive. LMP1 was expressed in 13/19 (68.4%) EBV-positive patients. The vast majority (16/19, 84.2%) of EBV positive patients carried the R131 allele (13 were heterozygous and 3 homozygous), while only 3 were homozygous for the H131 allele. Among 21 EBV-negative patients, only 6 (28.5%) carried the R131 allele (4 heterozygous and 2 homozygous) (2-sided p=0001). R131 allele was present in 11/13 (84.6%) LMP1-positive patients in comparison to 6/21 (28.0%) EBV-negative patients (2-sided p=0.002).
The high prevalence of FC gamma RIIA polymorphisms among EBV-positive patients indicates a possible pathogenetic role of the FC gamma RIIA in acquisition and chronicity of EBV infection. LMP1 is the major oncoprotein of EBV. The correlation of this polymorphism to LMP1 expression is an indication that it may play a major role in the expression of latency phase proteins, a fact that may further be implicated in the pathogenesis of lymphoproliferative diseases in these patients. We continue the study in our centre, increasing the number of patients enrolled.
No relevant conflicts of interest to declare.
Author notes
Asterisk with author names denotes non-ASH members.
