Evaluation of a 3A-truncated foot-and-mouth disease virus in pigs for its potential as a marker vaccine

Abstract

Foot-and-mouth disease (FMD) is a highly contagious and economically devastating disease of cloven-hoofed animals in the world. The disease can be effectively controlled by vaccination of susceptible animals with the conventional inactivated vaccine. However, one major concern of the inactivated FMD virus (FMDV) vaccine is that it does not allow serological discrimination between infected and vaccinated animals, and therefore interferes with serologic surveillance and the epidemiology of disease. A marker vaccine has proven to be of great value in disease eradication and control programs. In this study, we constructed a marker FMDV containing a deletion of residues 93 to 143 in the nonstructural protein 3A using a recently developed FMDV infectious cDNA clone. The marker virus, r-HN/3A93–143, had similar growth kinetics as the wild type virus in culture cell and caused a symptomatic infection in pigs. Pigs immunized with chemically inactivated marker vaccine were fully protected from the wild type virus challenge, and the potency of this marker vaccine was 10 PD50 (50% pig protective dose) per dose, indicating it could be an efficacious vaccine against FMDV. In addition, we developed a blocking ELISA targeted to the deleted epitope that could clearly differentiate animals infected with the marker virus from those infected with the wild type virus. These results indicate that a marker FMDV vaccine can be potentially developed by deleting an immunodominant epitope in NSP 3A.

Development of a Blocking ELISA Using a Monoclonal Antibody to a Dominant Epitope in Non-Structural Protein 3A of Foot-and-Mouth Disease Virus, as a Matching Test for a Negative-Marker Vaccine

“…Mab 3A24 reacted with peptides A3, A4, and Q3 (Fig 1B), which share a common “AEKNPL” sequence, indicating that the “AEKNPL” sequence was the core motif involved in 3A24 Mab recognition. As the recombinant virus (r-HN/3A93–143) deleted 93–143 aa in 3A cannot be recognized by Mab 3A24 by indirect immunofluorescent assay [9], we can conclude that 3A24 Mab is specific targeting to epitope “AEKNPLE”.…”

“…The sera groups were described as follow: (Ⅰ) sera from unvaccinated healthy animals, including 84 from cattle, 88 from sheep, and 88 from swine, which were obtained from an FMD-free region; (Ⅱ) sera from healthy vaccinated animals, including 99 from cattle and 176 from swine that had been inoculated twice with an inactivated vaccine against type O FMD; (Ⅲ) sera from infected animals, including 100 samples from cattle infected with Asia 1/JS/CHA/05 or O/Tibet/CHA/99 FMDV collected between 10–28 DPI; 88 serum samples from sheep infected with Asia 1/JS/CHA/05 collected between 11–365 DPI; 88 sera collected from pigs infected with O/Tibet/CHA/99 collected between 3–11 DPI; (Ⅳ) sera from experimentally infected animals, including 40 sera collected from 4 cattle infected with A/WH/CHA/2009 FMDV at 0–229 DPI; 48 sera collected from 2 sheep infected with O/Tibet/CHA/99 FMDV at 0–417 DPI; 16 sera collected from one pig infected with O/ Tibet/CHA/99 FMDV at 0–194 DPI. (Ⅴ)1074 field sera collected from animal herds suspected of FMDV infection in China during 2009–2014, including 464, 413, and 197 sera collected from vaccinated cattle, sheep, and pigs, with all serologically positive animals being slaughtered after surveillance; (Ⅵ) A total of 12 serum samples were obtained from 3 cattle and 3 pigs before and after inoculation with the wild type O/HN/CHA/93 (Cathay topotype) at 28 DPI; 16 serum samples were obtained from 3 cattle and 5 pigs before and after inoculation with the 3A epitope-deleted marker virus (r-HN/3A 93-143 ) at 28 DPI [9]. All wild type virus-inoculated pigs show typical FMD signs, while all marker virus-infected pigs only showed low-level clinical signs.…”

“…The FMDV 3A protein is a partially conserved protein with 153 amino acids (aa), or 143 aa in the case of the Cathay topotype of type O FMDV. The C-terminal half of the NSP 3A protein could be partially deleted, and the recombinant viruses were attenuated to some extent [9–11]. A Cathay topotype of the type-O marker FMDV (r-HN/3A93–143) was recently generated in our lab by deleting residues 93 to 143 (a region harboring immunodominant B cell epitopes) in the NSP 3A protein.…”

“…A Cathay topotype of the type-O marker FMDV (r-HN/3A93–143) was recently generated in our lab by deleting residues 93 to 143 (a region harboring immunodominant B cell epitopes) in the NSP 3A protein. The marker virus can adapt to replicate in suspension culture in BHK21 cells, and the marker vaccine is effective in protecting pigs from challenge with the wild type (WT) virus [9]. …”

Marker vaccine potential of foot-and-mouth disease virus with large deletion in the non-structural proteins 3A and 3B

“…FMDV serotype specific negative marker vaccine and companion DIVA assay was developed and evaluated by the partial deletion of the VP1 G-H loop [31]. However, in an endemic country, with the circulation of multiple FMDV serotypes, it could be recommended that the negative marker vaccine should be designed by deletion or modification of epitopes present in the NSP [32]. Recently, attenuated antigenically marked FMDV vaccine featuring the deletion of leader protein have been produced by modification of specific B-cell epitopes in the NSP 3B and 3D [33].…”