Dromedary camels as a natural source of neutralizing nanobodies against SARS-CoV-2
Lotfi Chouchane, … , Murugan Subramanian, Jingxuan Shan
Lotfi Chouchane, … , Murugan Subramanian, Jingxuan Shan
Published February 2, 2021
Citation Information: JCI Insight. 2021;6(5):e145785. https://doi.org/10.1172/jci.insight.145785.
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Research Article COVID-19

Dromedary camels as a natural source of neutralizing nanobodies against SARS-CoV-2

Abstract

The development of prophylactic and therapeutic agents for coronavirus disease 2019 (COVID-19) is a current global health priority. Here, we investigated the presence of cross-neutralizing antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in dromedary camels that were Middle East respiratory syndrome coronavirus (MERS-CoV) seropositive but MERS-CoV free. The tested 229 dromedaries had anti–MERS-CoV camel antibodies with variable cross-reactivity patterns against SARS-CoV-2 proteins, including the S trimer and M, N, and E proteins. Using SARS-CoV-2 competitive immunofluorescence immunoassays and pseudovirus neutralization assays, we found medium-to-high titers of cross-neutralizing antibodies against SARS-CoV-2 in these animals. Through linear B cell epitope mapping using phage immunoprecipitation sequencing and a SARS-CoV-2 peptide/proteome microarray, we identified a large repertoire of Betacoronavirus cross-reactive antibody specificities in these dromedaries and demonstrated that the SARS-CoV-2–specific VHH antibody repertoire is qualitatively diverse. This analysis revealed not only several SARS-CoV-2 epitopes that are highly immunogenic in humans, including a neutralizing epitope, but also epitopes exclusively targeted by camel antibodies. The identified SARS-CoV-2 cross-neutralizing camel antibodies are not proposed as a potential treatment for COVID-19. Rather, their presence in nonimmunized camels supports the development of SARS-CoV-2 hyperimmune camels, which could be a prominent source of therapeutic agents for the prevention and treatment of COVID-19.

Authors

Lotfi Chouchane, Jean-Charles Grivel, Elmoubasher Abu Baker Abd Farag, Igor Pavlovski, Selma Maacha, Abbirami Sathappan, Hamad Eid Al-Romaihi, Sirin W.J. Abuaqel, Manar Mahmoud Ahmad Ata, Aouatef Ismail Chouchane, Sami Remadi, Najeeb Halabi, Arash Rafii, Mohammed H. Al-Thani, Nico Marr, Murugan Subramanian, Jingxuan Shan

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Figure 3

Analysis of virus-neutralizing potential of SARS-CoV-2 cross-reactive camel sera.

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Analysis of virus-neutralizing potential of SARS-CoV-2 cross-reactive ca...
(A) SARS-CoV-2 RBD competition immunofluorescence assay using human neutralizing antibody (NAb) against SARS-CoV-2. The curve started with [NAb] concentration at 5 μg/ml and proceeded in a 12-step, 2-fold dilution series. The [NAb] concentration versus inhibition curve was fit by a 4-parameter logistic model. (B) The correlation between RBD binding inhibitory effects and seroreactivity with MERS-CoV S protein in camel sera. MERS-CoV S seroreactive–positive sera from 98 living camels were included. (C) Inhibition of ACE2 binding to SARS-CoV-2 RBD by 11 camel sera. The sera were serially diluted to 1:2, 1:6, 1:18, 1:54, 1:162, and 1:486. Each datum point represents the median of up to 500 individual beads. The log2(dilution) versus inhibition curves were fit by a 4-parameter logistic model. (D) Competition for RBD binding between RBD-specific human IgG1 monoclonal antibody AS35 and camel serum. Camel antibody binding on RBD was revealed by AF594-labeled goat anti-camel antibodies, and human NAb binding was revealed with AF488-labeled goat anti-human anti-IgG1 antibodies. (E) The correlation between inhibition of ACE2 binding and VHH antibody binding activity on RBD in 11 camel sera. (F) Single-dose (1:50 dilution) pseudovirus neutralizing assay. Twenty camel sera were randomly selected from the ones showing RBD binding inhibitory effects. The virus entry into HEK293 cells was monitored by relative luminescence (RLU). ACE2-Fc, ACE2-conjugated with Fc domain of human IgG; CS, control serum from a healthy individual. Error bars represent the standard deviation of biological triplicates. (G) Inhibition curves for 3 sera ranked top in single-dose assay. The sera were diluted 2 times and then subjected to 8-step, 2-fold series dilutions. Typical 4-parameter inhibition curves were observed between log-transformed dilution and inhibition rate (percentage) and were used to determine EC50. Error bars represent the standard deviation of biological triplicates.