Dromedaries (Camelus dromedarius) are of low susceptibility to inoculation with foot-and-mouth disease virus serotype O

Immunogenicity of imported foot-and-mouth vaccines in different species in Mongolia

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FMD vaccines were independently assessed using published international guidelines.

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Highest titres were seen with oil-adjuvanted vaccines with a 2 dose primary course.

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Lower titres were seen with aqueous vaccines requiring a boost after 3 months.

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It is unknown how the lower titres observed in camels correlate with protection.

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The results have important implications for vaccine policy in Mongolia.

Foot-and-mouth disease (FMD) is a high impact viral disease of livestock for which vaccines are extensively used in control. Mongolia has regular incursions of FMD virus that are typically limited to the eastern region although large epidemics are occasionally reported in the normally disease-free western areas. Vaccines are imported and form an important component of the control strategy. In 2015, post-vaccination monitoring guidelines were published by the FAO-OIE recommending approaches for assessing the appropriateness of imported vaccines including small-scale immunogenicity studies. This study used these recommended approaches to guide the use of vaccine adjuvant type and the need for a one or two dose primary course in the national control programme considering cattle, sheep and Bactrian camels and also whether these vaccines were appropriate for the FMD virus lineages considered high risk to Mongolia (A/ASIA/Sea-97; O/SEA/Mya-98; O/ME-SA/PanAsia; O/ME-SA/Ind-2001). The results of these immunogenicity studies indicated that in cattle and sheep, oil-adjuvanted vaccines led to higher and more persistent neutralisation titres that were satisfactory against the target lineages if a two-dose primary course was utilised. In contrast, aqueous-adjuvanted vaccines were associated with lower titres that likely required a booster after 3 months. Levels of antibodies in Bactrian camels were significantly lower although it is unknown how these may correlate with protection under experimental or field exposure conditions. The results of this study have implications for vaccine policy in Mongolia and suggest further studies on the role of Bactrian camels in the epidemiology of FMD are necessary to indicate if further research on FMD vaccines are needed in this species.

Characterization of single-domain antibodies against Foot and Mouth Disease Virus (FMDV) serotype O from a camelid and imaging of FMDV in baby hamster kidney-21 cells with single-domain antibody-quantum dots probes

Background

Foot-and-mouth disease (FMD) is a highly contagious disease that affects cloven-hoofed animals and causes significant economic losses to husbandry worldwide. The variable domain of heavy-chain antibodies (VHHs or single domain antibodies, sdAbs) are single-domain antigen-binding fragments derived from camelid heavy-chain antibodies.

Results

In this work, two sdAbs against FMD virus (FMDV) serotype O were selected from a camelid phage display immune library and expressed in Escherichia coli. The serotype specificity and affinity of the sdAbs were identified through enzyme-linked immunosorbent assay and surface plasmon resonance assay. Moreover, the sdAbs were conjugated with quantum dots to constitute probes for imaging FMD virions. Results demonstrated that the two sdAbs were specific for serotype O and shared no cross-reactivity with serotypes A and Asia 1. The equilibrium dissociation constant (KD) values of the two sdAbs ranged from 6.23 nM to 8.24 nM, which indicated high affinity to FMDV antigens. Co-localization with the sdAb-AF488 and sdAb-QD probes indicated the same location of FMDV virions in baby hamster kidney-21 (BHK-21) cells.

Conclusions

sdAb-QD probes are powerful tools to detect and image FMDV in BHK-21 cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-015-0437-2) contains supplementary material, which is available to authorized users.

Middle East respiratory syndrome coronavirus antibody reactors among camels in Dubai, United Arab Emirates, in 2005

We tested, using a low starting dilution, sequential serum samples from dromedary camels, sheep and horses collected in Dubai from February/April to October of 2005 and from dromedary camels for export/import testing between Canada and USA in 2000–2001. Using a standard Middle East respiratory syndrome coronavirus (MERS‐CoV) neutralization test, serial sera from three sheep and three horses were all negative while sera from 9 of 11 dromedary camels from Dubai were positive for antibodies supported by similar results in a MERS‐CoV recombinant partial spike protein antibody ELISA. The two negative Dubai camels were both dromedary calves and remained negative over the 5 months studied. The six dromedary samples from USA and Canada were negative in both tests. These results support the recent findings that infection with MERS‐CoV or a closely related virus is not a new occurrence in camels in the Middle East. Therefore, interactions of MERS‐CoV at the human–animal interface may have been ongoing for several, perhaps many, years and by inference, a widespread pandemic may be less likely unless significant evolution of the virus allow accelerated infection and spread potential in the human population.

Molecular cloning and phylogenetic analysis of integrins alphavbeta1 and alphavbeta6 of one-humped camel (Camelus dromedarius)

Bactrian camels can relatively easily be infected with FMDV, but dromedary camels remain resistant even to high doses of the virus. To understand the different susceptibility between the two camel species from the standpoint of viral receptors, this work reports the sequences of the dromedary camel integrin cDNAs encoding alphavbeta1 and alphavbeta6 and compare them to those of other species, especially to Bactrian camels. The complete coding sequences for the dromedary camel alphav, beta1 and beta6 subunits were found to be 3147, 2397, and 2364 nucleotides in length, encoding 1048, 798, and 787 amino acids, respectively. The dromedary camel integrin alphav, beta1, and beta6 subunit shares common structural and functional elements with their counterparts from the other species. Phylogenetic trees showed that the dromedary camel alphav, beta1, and beta6 were clustered into the Artiodactyla group, together with those of Bactrian camel, pig, sheep, and cattle that are susceptible to FMDV infection. Compared with the Bactrian camel integrins, 4, 10, and 8 amino acid changes were found in the dromedary camel alphav, beta1, and beta6 subunits, respectively. This study will be of importance in understanding the differences of integrins as FMDV receptors among dromedary camel and other species.

Bactrian camel (Camelus bactrianus) integrins alphavbeta3 and alphavbeta6 as FMDV receptors: molecular cloning, sequence analysis and comparison with other species

Integrins are heterodimeric adhesion receptors that participate in a variety of cell-cell and cell-extracellular matrix protein interactions. Many integrins recognize RGD sequences displayed on extracellular matrix proteins and the exposed loops of viral capsid proteins. Four members of the alphav integrin family of cellular receptors, alphavbeta3, alphavbeta6, alphavbeta1 and alphavbeta8, have been identified as receptors for foot-and-mouth disease virus (FMDV) in vitro, and integrins are believed to be the receptors used to target epithelial cells in the infected animals. To analyse the roles of the alphav integrins from a susceptible species as viral receptors, we have cloned Bactrian camel alphav, beta3 and beta6 integrin cDNAs and compared them to those of other species. The coding sequences for Bactrian camel integrin alphav, beta3 and beta6 were found to be 3165, 2289 and 2367 nucleotides in length, encoding 1054, 762 and 788 amino acids, respectively. The Bactrian camel alphav, beta3 and beta6 subunits share many structural features with homologues of other species, including the ligand binding domain and cysteine-rich region. Phylogenetic trees and similarity analyses showed the close relationships of integrin genes from Bactrian camels, pigs and cattle, which are each susceptible to FMDV infection, that were distinct from the orders Rodentia, Primates, Perissodactyla, Carnivora, Galliformes and Xenopus. We postulate that host tropism of FMDV may in part be related to the divergence in integrin subunits among different species.