Iron overload in multiply transfused patients who are HIV seropositive

Iron and infection: effects of host iron status and the iron-regulatory genes haptoglobin and NRAMP1 (SLC11A1) on host-pathogen interactions in tuberculosis and HIV

There are many lines of evidence illustrating that iron plays a pivotal role in modulating the battle for survival between mammalian hosts and their pathogens. Each displays considerable genetic investment in a wide range of mechanisms for acquiring and maintaining iron. These competitive mechanisms are highly complex, existing within an interacting matrix of absorption, transport, storage and detoxification systems, each of which are iron-responsive and thus able to adapt to the different phases of infection. Considerable genetic polymorphism in some of these systems, with signals of geographic selection in the hosts, and niche selection in the pathogens, indicates that they are critical for species survival. In this review we briefly summarize the role of iron in host immune function before reviewing the available evidence that iron modulates susceptibility and disease outcomes in HIV and TB (tuberculosis). We then examine the putative role of iron-related host genes by focussing on two candidate genes, haptoglobin and NRAMP1, for which there are common polymorphic variants in humans with strong evidence of functionally distinct biochemical phenotypes that would be predicted to influence the course of HIV and TB infections. Finally, we examine the limited evidence so far available that nutrient-gene interactions are likely to influence the way in which gene variants can protect against infection. We conclude that there is a wealth of evidence associating alterations in iron balance and in iron-regulatory systems with disease progression, but that many issues related to the direction of causality, mechanisms of action and sensitivity to pharmacological intervention remain to be elucidated. Since iron is probably the most widely prescribed compound throughout the world, used in both preventative and treatment regimens, a deeper understanding of the host-pathogen interactions relating to iron constitutes an important area for both basic and clinical research.

Evidences that zidovudine (AZT) could not be directly responsible for iron overload in AZT-treated patients: an in vitro study

Zidovudine (3'-azido-3'-deoxythymidine or azidothymidine, AZT) has been the first antiretroviral agent approved for clinical use, and it is still currently used in combination therapy of human immunodeficency virus (HIV) infection. On the basis of increasing clinical reports and in vitro studies, a strict correlation between AZT treatment of HIV positive patients and both the development of anemia and iron overload have been in evidence over the last few years. In this report, we have examined some features of zidovudine to better assess a likely implication of this drug in iron overload. For this purpose, we first determinated the iron chelating ability of both AZT and some of its phosphorylated derivatives in solution. The iron chelating ability of AZT toward the intracellular 'chelatable' iron pool was also evaluated. Finally, we investigated the effect of AZT on both iron and transferrin uptake. Our findings indicate that AZT per se cannot be directly responsible for the development of the iron overload found in human or animal models, for which other possible mechanisms are claimed to be involved.

Consensus statement: anemia in HIV infection--current trends, treatment options, and practice strategies. Anemia in HIV Working Group

BACKGROUND

Despite important advances in antiretroviral therapy, anemia remains a problem in many HIV-infected patients. Although the incidence of anemia in these patients has decreased, its prevalence appears to have stabilized or decreased only slightly. Anemia has a deleterious effect on both functional capacity and quality of life, and has been associated with shortened survival.

OBJECTIVE

The Anemia in HIV Working Group, an expert panel of physicians and researchers involved in the care of HIV-infected patients, met to determine the impact of anemia in this patient population; to develop practice strategies for the clinician treating HIV-infected patients with anemia; and to identify future research directions.

METHODS

The proposed practice strategies are based on results of the available clinical trials (as identified through a MEDLINE search), a review of the literature, and the clinical experience and expert opinion of the panel. The present report is based on meetings held in February and June of 1998; as further experience with various treatment options accumulates and the impact of highly active antiretroviral therapy becomes clearer, the panel will reconvene to develop evidence-based guidelines.

RESULTS

The working group considers HIV-associated anemia to be an important contributor to the morbidity and mortality of this infection. Recent reports indicate that recovery from anemia is associated with improved quality of life and survival.

CONCLUSIONS

As HIV-infected persons live longer, maintaining quality of life becomes an increasingly important goal of treatment. When planning treatment strategies, clinicians should consider the quality-of-life decrement caused by anemia. Transfusions should be used when rapid recovery is required, and underlying conditions causing anemia should be treated, if possible. Recombinant human erythropoietin (rHuEPO) therapy is appropriate in certain HIV-infected persons and should be considered to maintain hemoglobin concentrations. The target hemoglobin level is 12 g/dL for men and 11 g/dL for women. Weekly rHuEPO dosing is suggested, initiated at 40,000 U, as has been established in patients with cancer.

3'-Azido-3'-deoxythymidine reduces the rate of transferrin receptor endocytosis in K562 cells

K562 cells, exposed for at least 24 h to 5 microM 3'-azido-3'-deoxythymidine (AZT), gave rise to an overall increase in the number of cell surface transferrin binding receptors (18-20%). This effect was ascertained either with binding experiments by using 125I-transferrin and with immunoprecipitation by using a specific monoclonal antibody against the transferrin receptor. At higher AZT concentrations (20 and 40 microM), a further increase was found, that is, up to 23% by binding experiments and up to 110% by immunoprecipitation. However, Scatchard analysis of the binding data indicated that although the number of cell surface transferrin receptors increased, the affinity of transferrin for its receptor did not change (Ka=4.0x108 M). Surprisingly, immunoprecipitation of total receptor molecules showed that the synthesis of receptor was not enhanced by the drug treatment. The effect of AZT on transferrin internalization and receptor recycling was also investigated. In this case, data indicated that the increase in the number of receptors at the cell surface was probably due to a slowing down of endocytosis rate rather than to an increased recycling rate of the receptor to cell surface. In fact, the time during which half the saturated amount of transferrin had been endocytosed (t1/2) was 2.15 min for control cells and 3.41, 3.04, and 3.74 min for 5, 20, and 40 microM AZT-treated cells, respectively. Conversely, recycling experiments did not show any significant differences between control and treated cells. A likely mechanism through which AZT could interfere with the transferrin receptor trafficking, together with the relevance of our findings, is extensively discussed.

Bone marrow macrophage iron grade and survival of HIV-seropositive patients

OBJECTIVE

Increased iron stores predispose to certain microbial infections. This association might be especially important in patients whose immune system is impaired by HIV. This study examined the relationship between iron stores and the survival times of patients with HIV infection.

DESIGN

Retrospective analysis of iron stores, as determined directly in bone marrow aspirates, and of hospital records.

SETTING

The George Washington University Hospital, an urban academic tertiary care institution.

PATIENTS

Three hundred and forty-eight HIV-seropositive adults who had diagnostic bone marrow aspirates between January 1985 and June 1996.

MEASUREMENTS

Bone marrow macrophage iron stores were graded on a scale of 0 to 5. For analysis of the influence of iron stores on survival, we compared patients with grades 4-5 iron stores (markedly or massively increased; n = 188) to those with grades 0-2 iron stores (normal or decreased; n = 130).

RESULTS

Infections caused by Candida spp., Pneumocystis carinii, and Mycobacterium spp. were more common in patients with high macrophage iron grades than in patients with low or normal iron grades (P < or = 0.006). The adjusted estimated rate of death (hazards ratio) was higher in patients with high iron stores compared with patients with low or normal iron stores, both from the time of the bone marrow study (ratio of 2.1; 95% confidence interval 1.3-3.5; P = 0.003) and the determination of HIV-seropositivity (ratio of 2.8; 95% confidence interval 1.4-4.9; P = 0.001).

CONCLUSION

High iron stores, as determined by bone marrow macrophage iron grade, may be associated with shorter survival times in patients with HIV infection.

Diagnosis and treatment of hepatic disease in patients with HIV

Liver involvement with opportunistic infections and neoplasms is a well-recognized component of AIDS, affecting most patients. The cause of hepatic disease in these patients may be divided into hepatitis, granulomatous disease, mass lesions, vascular lesions, hepatotoxic drugs, and nonspecific findings. With a rational approach, most patients with AIDS and liver disease can be diagnosed and treated in a cost-effective manner with low morbidity.