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. 2020 Jun 17;17(1):77.
doi: 10.1186/s12985-020-01347-5.

Challenge infection model for MERS-CoV based on naturally infected camels

Naif Khalaf Alharbi  1   2 , Osman H Ibrahim  3 , Ali Alhafufi  3 , Samy Kasem  3   4 , Ali Aldowerij  3 , Raed Albrahim  3 , Ali Abu-Obaidah  3 , Ali Alkarar  3 , Faisal Altaib Bayoumi  3 , Ali Mohammed Almansour  3 , Musaad Aldubaib  5 , Hail M Al-Abdely  6   7 , Hanan H Balkhy  8   9   10 , Ibrahim Qasim  3
Affiliations

Challenge infection model for MERS-CoV based on naturally infected camels

Naif Khalaf Alharbi et al. Virol J. .

Abstract

Background: Middle East Respiratory Syndrome coronavirus (MERS-CoV) is an emerging virus that infects humans and camels with no approved antiviral therapy or vaccine. Some vaccines are in development for camels as a one-health intervention where vaccinating camels is proposed to reduce human viral exposure. This intervention will require an understanding of the prior exposure of camels to the virus and appropriate vaccine efficacy studies in camels.

Methods: We conducted a cross sectional seroprevalence study in young dromedary camels to determine the rate of MERS-CoV seropositivity in young camels. Next, we utilised naturally infected camels as a natural challenge model that can be used by co-housing these camels with healthy naive camels in a ratio of 1 to 2. This model is aimed to support studies on natural virus transmission as well as evaluating drug and vaccine efficacy.

Results: We found that 90% of the screened camels have pre-existing antibodies for MERS-CoV. In addition, the challenge model resulted in MERS-CoV transmission within 48 h with infections that continued for 14 days post challenge.

Conclusions: Our finding suggests that the majority of young dromedary camels in Saudi Arabia are seropositive and that naturally infected camels can serve as a challenge model to assess transmission, therapeutics, and vaccine efficacy.

Keywords: Challenge model; Dromedary camels; MERS-CoV; Saudi Arabia; Seroprevalence; Vaccine efficacy.

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Conflict of interest statement

We do not have any conflict of interest.

Figures

Fig. 1
Fig. 1
Screening of young camels for MERS-CoV antibodies. a: A representative map of KSA showing the number of camels per province, written underneath province names. Density of colour represents the camel number per 100 km2 in each province. b and c: 362 dromedary calves below the age of 2 years were screened for anti-S1 antibodies using EUROIMMUN ELISA kits. ELISA Ratio of > 1.1 is positive, < 0.8 is negative, between 0.8 and 1.1 is equivocal. Dotted line represents the assay positive cutoff of 1.1. Seven different herds and farms were screened in Qassim (Q) province and twelve in Jouf (J) province
Fig. 2
Fig. 2
MERS-CoV natural infection in dromedaries as a challenge model Five calves (closed circle symbols) were mixed with three naturally infected camels (black symbols). Nasal swabs were assessed for the presence of MERS-CoV UpE (a) and ORF1a (v) amplicons by RT-qPCR for 14 (and at 42) d.p.c. Pre-challenge Ct values for the naïve calves were also included (0 d.p.c.). Ct values are shown for individual camels. Dotted line represents the cutoff Ct value of 37. A value of 40 were given to all undetectable (negative) samples
See this image and copyright information in PMC

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