HUMORAL IMMUNE-RESPONSE AGAINST HUMAN CYTOMEGALOVIRUS (HCMV)-SPECIFICPROTEINS AFTER HCMV INFECTION IN LUNG TRANSPLANTATION AS DETECTED WITH RECOMBINANT AND NATURALLY-OCCURRING PROTEINS

The humoral immune response to four intracellularly located cytomegalo virus (CMV) proteins was studied in 15 lung transplant recipients expe riencing active CMV infections. Five patients had primary infections, and 10 had secondary infections. Antibodies of the immunoglobulin M (I gM) and IgG classes were measured in an enzyme-linked immunosorbent as say (ELISA) system in which procaryotically expressed recombinant prot eins were used as a substrate and also in a monoclonal antibody-based capture ELISA which uses naturally occurring proteins as a substrate. The proteins investigated were the lower matrix protein pp65 (ppUL83), the major DNA-binding protein p52 (ppUL44), and the two immediate ear ly proteins IE1 and IE2 (different splicing products of UL123). Higher levels of antibodies were found to pp65 and especially to p52 than to the immediate early antigens. Antibody levels detected in the recombi nant protein-based ELISAs were generally lower than antibody responses detected with the matching antigen capture ELISA. Moreover, some pati ents appeared to have antibodies mainly to epitopes present on natural ly occurring proteins. The antibody responses detected in both assays were related to the viral load during infection as assessed by the CMV antigenemia test, which is a quantitative marker for CMV load. It was found that although epitopes on naturally occurring proteins induce h igher antibody responses and responses in more patients, antibodies di rected to epitopes present on the recombinant proteins were inversely related to the viral load during a CMV infection. Therefore, antibodie s to epitopes on the recombinant proteins might be more clinically rel evant in this group of lung transplant recipients.