Isolation and Characterization of Dromedary Camel Coronavirus UAE-HKU23 from Dromedaries of the Middle East: Minimal Serological Cross-Reactivity between MERS Coronavirus and Dromedary Camel Coronavirus UAE-HKU23

Abstract

Recently, we reported the discovery of a dromedary camel coronavirus UAE-HKU23 (DcCoV UAE-HKU23) from dromedaries in the Middle East. In this study, DcCoV UAE-HKU23 was successfully isolated in two of the 14 dromedary fecal samples using HRT-18G cells, with cytopathic effects observed five days after inoculation. Northern blot analysis revealed at least seven distinct RNA species, corresponding to predicted subgenomic mRNAs and confirming the core sequence of transcription regulatory sequence motifs as 5′-UCUAAAC-3′ as we predicted previously. Antibodies against DcCoV UAE-HKU23 were detected in 58 (98.3%) and 59 (100%) of the 59 dromedary sera by immunofluorescence and neutralization antibody tests, respectively. There was significant correlation between the antibody titers determined by immunofluorescence and neutralization assays (Pearson coefficient = 0.525, p < 0.0001). Immunization of mice using recombinant N proteins of DcCoV UAE-HKU23 and Middle East respiratory syndrome coronavirus (MERS-CoV), respectively, and heat-inactivated DcCoV UAE-HKU23 showed minimal cross-antigenicity between DcCoV UAE-HKU23 and MERS-CoV by Western blot and neutralization antibody assays. Codon usage and genetic distance analysis of RdRp, S and N genes showed that the 14 strains of DcCoV UAE-HKU23 formed a distinct cluster, separated from those of other closely related members of Betacoronavirus 1, including alpaca CoV, confirming that DcCoV UAE-HKU23 is a novel member of Betacoronavirus 1.

Diversity of Dromedary Camel Coronavirus HKU23 in African Camels Revealed Multiple Recombination Events among Closely Related Betacoronaviruses of the Subgenus Embecovirus

“…Microneutralization assays. Heat-inactivated (56°C for 30 min) camel sera were first diluted 1:10 and then subjected to serial 2-fold dilutions and mixed with equal volumes of virus at a dose of 200 50% tissue culture infective doses (TCID 50 ) of DcCoV-HKU23 isolate 368F (49). After 1 h of incubation at 37°C, 35 l of the virus-serum mixture was added in quadruplicate to HRT-18G cell monolayers in 96-well microtiter plates.…”

Hosts and Sources of Endemic Human Coronaviruses

“…The bovine CoV (BCoV) is the best-studied representative, whereas essentially the same virus is present in other ungulates whose common names are often identified in virus designations (e.g., Giraffe-CoV; Hasoksuz et al, 2007). The recently described camel CoV HKU23 is a BCoV variant previously known to exist in camels (Corman et al, 2016;Reusken et al, 2013;Sabir et al, 2016;Woo et al, 2016;Wunschmann et al, 2002). All of these viruses belong to BetaCoV1, whose hosts comprise primates, lagomorphs, artiodactyls, and perissodactyls, as well as carnivores (Alekseev et al, 2008;Drexler et al, 2014;Erles et al, 2003;Guy et al, 2000;Hasoksuz et al, 2007;Lau et al, 2012;Lim et al, 2013;Majhdi et al, 1997;Tsunemitsu et al, 1995;Woo et al, 2014) (Fig.…”

Middle East respiratory syndrome (MERS) coronavirus and dromedaries

“…Genera (Woo et al, 2014d). Recently, we successfully isolated DcCoV UAE-HKU23 using the human rectal tumour HRT-18G cell line and confirmed that it is different from the betaCoV in alpacas using bioinformatics approaches (Woo et al, 2016b). Although both MERS-CoV and DcCoV UAE-HKU23 are beta CoVs, there is minimal cross antigenicity between them, as shown by various serological tests (Woo et al, 2014d).…”