Humoral Immune Responses to Epstein-Barr virus encoded Tumor Associated Proteins and their Putative Extracellular Domains in Nasopharyngeal Carcinoma Patients and Regional Controls

Dewi Kartikawati Paramita (1) , Christien Fatmawati (1) , Hedy Juwana (2) , Frank G. van Schaijk (2) , Jajah Fachiroh (1) , Sophia Mubarika Haryana (1) , Jaap M. Middeldorp (3)

1 Faculty of Medicine
2 Pathology
3 Department of Pathology

Epstein-Barr virus latency proteins EBNA1, LMP1, LMP2 and BARF1 are expressed in tumor cells of nasopharyngeal carcinoma (NPC). IgG and IgA antibody responses to these non-self tumor antigens were analysed in NPC patients (n=125) and regional controls (n=100) by three approaches, focusing on the putative LMP1, LMP2 extracellular domains. Despite abundant IgG and IgA antibody responses to lytic antigens and EBNA1, patients had low titer (1:25 - 1:100) IgG to LMP1 (81.2%), LMP2 (95.6%) and BARF1 (84.8%), while immunoblot showed such reactivity in 24.2%, 12.5% and 12.5% at 1:50 dilution, respectively. Few IgA responses were detected, except for EBNA1. Controls only showed IgG to EBNA1. ELISA using peptides from different domains of LMP1, LMP2 and BARF1 also yielded mostly negative results. When existing, low level IgG to intracellular C-terminus of LMP1 (62.9%) prevailed. Rabbit immunisation with peptides representing extracellular (loop) domains yielded loop-specific antibodies serving as positive control. Importantly, these rabbit antibodies stained specifically extracellular domains of LMP1 and LMP2 on viable cells and mediated complement-driven cytolysis. Rabbit anti-LMP1 loop-1 and -3 killed 50.4% and 59.4% of X50/7 and 35.0% and 35.9% of RAJI cells, respectively, and 22% of both lines were lysed by anti-LMP2 loop-2 or -5 antibodies. This study demonstrates that (extracellular domains of) EBV-encoded tumor antigens are marginally immunogenic for humoral immune responses. However, peptide specific immunization may generate such antibodies, which can mediate cell killing via complement activation. This opens options for peptide-based tumor vaccination in patients carrying EBV latency-II type tumors such as nasopharyngeal carcinoma.

Mots clés: Medicine

Dewi Kartikawati Paramita, Christien Fatmawati, Hedy Juwana, Frank G. van Schaijk, Jajah Fachiroh, et al.. Humoral Immune Responses to Epstein-Barr virus encoded Tumor Associated Proteins and their Putative Extracellular Domains in Nasopharyngeal Carcinoma Patients and Regional Controls. Journal of Medical Virology, 2011, 83 (4), pp.665. ⟨10.1002/jmv.21960⟩. ⟨hal-00614671⟩