CHANGES IN THE SPECIFICITY OF ANTIBODIES IN MICE INFECTED WITH LACTATE DEHYDROGENASE-ELEVATING VIRUS

Infection with lactate dehydrogenase-elevating vints (LDV) modifies th e isotypic distribution of antibodies (Ab) directed to several antigen ic proteins with a preferential production of IgG2a. Because it was no t known whether the virus could also affect the Ab specificity, the au thors addressed this point using human growth hormone (hGH) as a model antigen. Anti-hGH monoclonal antibodies (MoAb) were used as probes to study the occurrence of Ab to three native hGH epitopes (3C11, F11 an d 10D6) in sera from LDV-infected CBA/Ht and BALB/c mice immunized wit h hGH. Competition ELISA was used to determine the extent of Ab direct ed to cryptic hGH epitopes, i.e. antigenic determinants hidden in the native hormone. Results indicated that in LDV-infected CBA/Ht mice the titres of anti-hGH Ab were lower than in controls, although a consist ent isotypic shift to IgG2a subclass was observed. Concurrently, the p resence of Ab to epitopes 3C11, F11 and/or 10D6 were markedly reduced in infected animals and most anti-hGH Ab were directed to hGH cryptic epitopes. By contrast, LDV infection increased the amount of anti-KLH Ab elicited by CBA/Ht mice and did not affect Ab specificity, whilst c ontrol and LDV-infected BALB/c mice showed similar concentrations of a nti-hGH Ab. Furthermore, the proportion of Ab to cryptic hGH epitopes did not change in infected animals even though an important shift to I gG2a was detected. Thus, data presented herein suggest that LDV Infect ion modifies Ab specificity depending on the mice genetic background a nd on the antigenic characteristics of the immunogen.