The Role of Macrophage Migration Inhibitory Factor (MIF) Genetic Polymorphisms in Predicting the Development of Macrocytic Anemia in HIV+ Patients.

Anemia is the most common hematologic morbidity in HIV+ patients and is associated with increased mortality. In previous studies, we have examined anemia-associated mortality in over 30,000 HIV+ men cared for within the VA system, and have confirmed the increased mortality previously shown to be associated with anemia. Most strikingly, however, we have demonstrated that macrocytosis in particular is an independent risk factor for early mortality even after correcting for alcohol abuse, liver disease, or therapy with AZT. We hypothesize that macrocytosis reflects a proinflammatory state associated with HIV and magnified by co-morbidities. We have therefore sought to link anemia with known markers of underlying inflammation. Genetic variants that affect the level of cytokine gene expression have been shown to influence the development of anemia associated with a variety of illnesses. One such polymorphism occurs in the macrophage migration inhibitory factor (MIF) gene, a cytokine secreted by macrophages and T-cells that induces release of TNF and IL-6 from macrophages. Our group has defined two polymorphisms in the promoter of the human MIF gene that affect the level of MIF expression. The first, a tetranucleotide CATT repeat, occurs 5-8 times within a Pit-1transcription factor binding site, and increased numbers of repeats are associated with higher levels of MIF expression. The second, a single-nucleotide polymorphism (SNP), has been identified at −173 bp (G/C), although its significance in predicting cytokine levels has been hard to separate from the associated CATT repeat polymorphism. High expression MIF polymorphisms have been shown to correlate with the development of anemia in the setting of malaria, to influence recovery from community acquired pneumonia, and to increase the severity of manifestations of rheumatoid arthritis. We therefore undertook to examine whether MIF polymorphisms might influence the development of anemia in the setting of HIV. We wished to test the hypothesis that the presence of high-expressing alleles of MIF predisposes to the development of anemia in the setting of HIV, particularly in association with other co-morbid conditions. In order to address this question, genomic DNA isolated/extracted from blood collected as part of the Veterans Aging Cohort Study (VACS) has been genotyped for the polymorphisms using a PCR based method. These data are being correlated with anemia, mean corpuscular volume, and CD4 count. We are using Cox proportional hazards models stratified by age, race, HIV severity, and co-morbid disease to examine associations between anemia type/severity and MIF gene polymorphisms. We are currently analyzing the prevalence of high-expressing MIF alleles in non-anemic and anemic patients with and without HIV, using multivariate analysis to identify correlations of genotype with markers of morbidity. It is hoped that these studies will provide insight into the etiology of anemia in HIV+ patients in general, and of macrocytic anemia in particular.