DYNAMICS OF CELL-ASSOCIATED VIREMIA AND ANTIBODY-RESPONSE DURING THE EARLY PHASE OF LENTIVIRUS INFECTION IN SHEEP

Objective-To determine patterns of cell-associated viremia arid antibo dy responses during the early phase of ovine lentivirus (OvLV) infecti on in sheep. Animals-18 neonatal lambs. Procedures-12 lambs were inocu lated intratracheally with OvLV within 24 hours after birth; 6 lambs w ere inoculated with noninfected cell culture supernatant. Degree of ce ll-associated viremia was measured every other week for 16 weeks by us e of a limited dilution assay. Antibody responses to OvLV transmembran e (TM) and p25 proteins were determined weekly by use of a recombinant ELISA. Neutralizing antibody responses were measured before and 8 and 16 weeks after inoculation. Results-Degree of cell-associated viremia peaked between 2 and 6 weeks after inoculation and then decreased. Fo r inoculated lambs, mean anti-p25 titer peaked 5 weeks after inoculati on then slowly declined, whereas mean anti-TM and neutralizing antibod y titers increased steadily. Over time, mean degree of cell-associated viremia was negatively correlated with mean anti-TM titer. Maximum in dividual degree of cell-associated viremia was positively correlated w ith maximum individual anti-TM titer. Conclusions-Results suggest that after experimental inoculation, OvLV replicates actively for several weeks and that an increase in anti-TM titer coincides with a decrease in degree of cell-associated viremia. Although the role antibodies pla y in protecting against lentivirus infection remains uncertain, unders tanding the dynamics of the antibody response may have important impli cations for diagnosis of OvLV infection, and antibodies may prove to b e valuable markers for prediction of infection and disease.