Sickle cell research in Africa yields global benefits
September/October 2024 | Volume 23 Number 5
Photo courtesy of Badru Katumba / World Health OrganizationHealthcare workers monitor the blood pressure of a person with sickle cell disease.
More than 100 million people worldwide live with the sickle cell trait; this means a person has one normal and one abnormal copy of the hemoglobin gene. Two abnormal copies of the gene cause sickle cell disease (SCD). Between 2000 and 2021, the number of babies born with SCD surged by 13.5%, with increasing rates reported in nearly every nation studied. According to the
Global Burden of Disease Study 2021, the highest SCD disability burden was concentrated in western and central sub-Saharan Africa and India.
In SCD, genetic mutations cause red blood cells, which are typically round, to be shaped more like crescent moons. Round red blood cells move quickly through the blood vessels, but sickle-shaped cells can impair blood flow and result in clots and low oxygen levels, leading to chronic, acute pain syndromes, severe bacterial infections, and tissue death. Someone who is a carrier of the sickle cell trait does not suffer from SCD; however, they will likely pass that gene on to their children, who may potentially suffer from SCD as a result.
Currently, there are several treatment options available for SCD. Hydroxyurea is usually the first prescribed medication, while voxelotor, L-glutamine, and crizanlizumab-tmca treat different aspects of the disease. Those suffering from SCD may also receive ongoing blood transfusions as part of their treatment. In 2023, the U.S. Food and Drug Administration approved two new gene therapies to treat SCD that can either add a modified gene to the body or make changes to a gene that is already in the body.
These existing and new therapies reflect the scientific advances that have been made, yet they can be cost-prohibitive for many patients in high-income countries—and even more so for patients in low- and middle-income countries.
Tanzanian research
Dr. Siana Nkya, a senior lecturer at Muhimbili University of Health and Allied Sciences (MUHAS) in Tanzania, studies the genomic determinants of SCD in sub-Saharan African populations. Nkya, a former Fogarty Global Health Fellow, has spent the last 15 years of her career studying the effects of fetal hemoglobin decline among infants with sickle cell disease, a key factor modifying the severity of sickle cell disease.
She recently completed a
five-year project through an NIH Emerging Global Leader Award funded by Fogarty. This project involved establishing a birth cohort of more than 250 infants to study the natural decline of fetal hemoglobin in both sickle cell and non-sickle cell infants. The study tracked hemoglobin levels in these infants from birth till up to 3 years of age, providing critical insights into how fetal hemoglobin declines more slowly in infants with SCD compared to those without the condition. This delayed decline, or "delayed switch," is vital for understanding how to develop effective interventions, such as the timely administration of hydroxyurea.
Nkya’s work has not only contributed to a better understanding of SCD but has also laid the groundwork for future research and policy development in genetics across Africa. In fact, Nkya, who is president of the Tanzanian Human Genomics Organization (THGO), has been actively involved in advancing genetic research and policy in Tanzania. THGO, which will soon celebrate its fifth anniversary, has made significant progress in advocacy, training, research, diagnosis, and therapeutics. Notably, THGO has organized a national stakeholders' meeting that brought together key figures in genetics from across Tanzania to develop a human genetics agenda and shape government policy on genetics in the region for the next five years.
When asked about her hopes for the future, Nkya said, "I believe that there's a lot that will come out of genomic research in Africa, and I'm hoping that we will see more and more investment in this area."
Global impact of sickle cell trait
Recently, the National Human Genome Research Institute (NHGRI) published a study showing that genetic carriers of the sickle cell trait are prevalent across diverse human populations, including those of Mediterranean, Indian, and Middle Eastern ancestry, not just those of African origin, as was previously assumed. Other recent studies have also shown a marked increase in SCD birth rates in Latin America and the Caribbean. Fogarty-supported research in genomics and other disciplines conducted by Dr. Adel Driss in Ghana, Dr. Sophie Kiguli in Uganda, and Dr. Halima Bello-Manga in Nigeria also might contribute to the knowledge base that helps patients with SCD around the world.
Nkya said, "The more we support research in Africa, it's not just for Africa. It benefits the globe."
Updated October 16, 2024
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