article · Proceedings of the National Academy of Sciences
Middle East respiratory syndrome coronavirus in dromedary camels across Africa exhibits distinct regional diversity compared to strains from the Arabian Peninsula. Genetic and phenotypic characterisation of camel viruses from Morocco, Burkina Faso, Nigeria, and Ethiopia demonstrates that African strains form a separate clade, termed clade C, while remaining antigenically similar to Arabian strains. Within this group, strains from West and North Africa form subclade C1, distinguished by characteristic deletions in the accessory gene ORF4b. Viral isolates from Burkina Faso and Nigeria demonstrate reduced replication competence in human respiratory cell cultures, human ex vivo lung tissues, and human DPP4-transduced mice when compared to Saudi Arabian isolates. Although removing ORF4b enhances interferon responses in cultured cells, this deletion alone does not explain the reduced replication capacity, suggesting other genetic factors limit zoonotic risk.
MERS-CoV causes severe zoonotic disease, yet documented human infections remain concentrated in the Arabian Peninsula despite widespread viral presence in African camels. Demonstrating that African camel strains replicate less effectively in human respiratory tissues provides a biological explanation for regional differences in infection rates, helping health authorities better gauge spillover risks and focus surveillance at the animal-human interface.
This early-stage virological research does not present an immediate commercial product, but the findings are relevant to diagnostic manufacturers and vaccine developers. Identifying regional clade differences and antigenic similarities enables developers to evaluate whether existing diagnostic tests and vaccine candidates effectively recognise African lineages. Any real-world application in targeted surveillance tools or updated biological reagents remains at an early discovery phase.
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Middle East respiratory syndrome coronavirus (MERS-CoV) causes a zoonotic respiratory disease of global public health concern, and dromedary camels are the only proven source of zoonotic infection. Although MERS-CoV infection is ubiquitous in dromedaries across Africa as well as in the Arabian Peninsula, zoonotic disease appears confined to the Arabian Peninsula. MERS-CoVs from Africa have hitherto been poorly studied. We genetically and phenotypically characterized MERS-CoV from dromedaries sampled in Morocco, Burkina Faso, Nigeria, and Ethiopia. Viruses from Africa (clade C) are phylogenetically distinct from contemporary viruses from the Arabian Peninsula (clades A and B) but remain antigenically similar in microneutralization tests. Viruses from West (Nigeria, Burkina Faso) and North (Morocco) Africa form a subclade, C1, that shares clade-defining genetic signatures including deletions in the accessory gene <i>ORF4b</i> Compared with human and camel MERS-CoV from Saudi Arabia, virus isolates from Burkina Faso (BF785) and Nigeria (Nig1657) had lower virus replication competence in Calu-3 cells and in ex vivo cultures of human bronchus and lung. BF785 replicated to lower titer in lungs of human DPP4-transduced mice. A reverse genetics-derived recombinant MERS-CoV (EMC) lacking <i>ORF4b</i> elicited higher type I and III IFN responses than the isogenic EMC virus in Calu-3 cells. However, <i>ORF4b</i> deletions may not be the major determinant of the reduced replication competence of BF785 and Nig1657. Genetic and phenotypic differences in West African viruses may be relevant to zoonotic potential. There is an urgent need for studies of MERS-CoV at the animal-human interface.
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DOI: 10.1073/pnas.1718769115
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