Functional characterization of compound heterozygosity Hb S/Hb Deer Lodge in Brazil

Abstract

Introduction  The Hb Deer Lodge (β2 His>Arg; HBB:c.8A>G) is a structural hemoglobin variant described in some populations around the world, characterized by increased oxygen affinity, but does not confer clinical symptoms to its carriers. The coinheritance of the Hb Deer Lodge with the most common hemoglobin variant, Hb S, has been reported only once; however, functional data were not described. Here we show a case of the Hb S and Hb Deer Lodge carrier in heterozygosity.

Methods  The Hb S and Hb Deer Lodge association was identified by High-Performance Liquid Chromatography (HPLC), reverse phase HPLC and the β globin gene sequencing. The functional characterization of this interaction was obtained using the O₂ dissociation curve, determination of the cooperativity between the globin chains and the Bohr effect in the presence and absence of organic phosphates.

Results  When the Hb S and Hb Deer Lodge were associated, there was a decrease in cooperativity, no significant changes in oxygen affinity and no significant Bohr effect changes.

Conclusion  Despite these genetic variations, the carrier showed no hematological alterations and no clinical symptoms, possibly due to the high oxygen affinity of the Hb Deer Lodge, which interferes with the Hb S polymerization.

Keywords
Sickle cell disease; Hemoglobin variant; Hemoglobin Deer Lodge