Time Course of MERS-CoV Infection and Immunity in Dromedary Camels

Abstract

Knowledge about immunity to Middle East respiratory syndrome coronavirus (MERS-CoV) in dromedary camels is essential for infection control and vaccination. A longitudinal study of 11 dam-calf pairs showed that calves lose maternal MERS-CoV antibodies 5-6 months postparturition and are left susceptible to infection, indicating a short window of opportunity for vaccination.

Keywords: MERS-CoV; Middle East respiratory syndrome coronavirus; calves; camel; dams; dromedary; immunity; infection; maternal antibodies; risk assessment; viruses.

Figure

MERS-CoV–specific IgG antibody levels in dromedary camel dam–calf pairs, United Arab Emirates, 2014–2015. A) MERS-CoV spike protein S1-domain–based ELISA ratios of individual samples (dots) plus mean (horizontal line) and SD (error bars) over the course of 1 year for dams (black dots) and calves (gray dots). Ratios were calculated by dividing the ELISA optical density at 450 nm of each sample by that of a calibrator to minimize interassay variation. Dashed lines indicate cutoff values for positive (ratio 1.1) and borderline (ratio 0.8) samples. MERS-CoV infection indicates time points where MERS-CoV RNA was detected in camels. B) Neutralizing titers of individual samples from camel calves at selected time points determined by microneutralization test (dots). For comparison, ELISA ratios for the selected time points are shown in parallel as a boxplot diagram; box represents 50% of the complete dataset from the first to the third quartile, and whiskers are drawn according to the Tukey method. MERS-CoV, Middle East respiratory syndrome coronavirus; NT, neutralization test.