MULTIFACTORIAL ETIOLOGY OF ANEMIA IN SIV-INFECTED RHESUS MACAQUES - DECREASED BFU-E FORMATION, SEROLOGIC EVIDENCE OF AUTOIMMUNE HEMOLYSIS, AND AN EXUBERANT ERYTHROPOIETIN RESPONSE

We attempted to define the etiology of anemia in SIV-infected rhesus m acaques. Bone marrow culture showed significantly decreased (75% reduc tion) burst forming unit-erythroid (BFU-E) growth in end-stage SIV' '' sick'' animals. Direct antiglobulin tests (DAT) were positive in nine of 35 SIV+ ''well'' and 14 of 14 SIV+ ''sick'' monkeys (0 of 25 contro l animals had positive DATs). In animals with a positive DAT, moderate to severe anemia was observed, as was increased LDH and spherocytosis . Erythropoietin was measured in four control, eight SIV' ''well'' and five SIV+ ''sick'' animals with mean levels of 4.0, 15.4, and 1176 mU /mL (r = .94) in the three groups. These data suggest that the cause o f anemia in the SIV-infected rhesus macaque is multifactorial, that th ere may be a defect in erythropoiesis, and that, serologically, an IgG mediated autoimmune hemolytic anemia is also present.