A Malaysia 97 monovalent foot-and-mouth disease vaccine (>6PD50/dose) protects pigs against challenge with a variant FMDV A SEA-97 lineage virus, 4 and 7 days post vaccination.

Pigs play a significant role during outbreaks of foot-and-mouth disease (FMD) due to their ability to amplify the virus. It is therefore essential to determine what role vaccination could play to prevent clinical disease and lower virus excretion into the environment. In this study we investigated the efficacy of the double oil emulsion A Malaysia 97 vaccine (>6PD50/dose) against heterologous challenge with an isolate belonging to the A SEA-97 lineage at 4 and 7 days post vaccination (dpv). In addition, we determined whether physical separation of pigs in the same room could prevent virus transmission. Statistically there was no difference in the level of protection offered by 4 and 7 dpv. However, no clinical disease or viral RNA was detected in the blood of pigs challenged 4 dpv, although three of the pigs had antibodies to the non-structural proteins (NSPs), indicating viral replication. Viral RNA was also detected in nasal and saliva swabs, but on very few occasions. Two of the pigs vaccinated seven days prior to challenge had vesicles distal from the injection site, but on the inoculated foot, and two pigs had viral RNA detected in the blood. One pig sero-converted to the NSPs. In contrast, all unvaccinated and inoculated pigs had evidence of infection. No infection occurred in any of the susceptible pigs in the same room, but separated from the infected pigs, indicating that strict biosecurity measures were sufficient under these experimental conditions to prevent virus transmission. However, viral RNA was detected in the nasal swabs of one group of pigs, but apparently not at sufficient levels to cause clinical disease. Vaccination led to a significant decrease in viral RNA in vaccinated pigs compared to unvaccinated and infected pigs, even with this heterologous challenge, and could therefore be considered as a control option during outbreaks.

Efficacy of a high potency O1 Manisa monovalent vaccine against heterologous challenge with a FMDV O Mya98 lineage virus in pigs 4 and 7 days post vaccination.

Early protection with a high potency (>6PD50) foot-and-mouth disease (FMD) O1 Manisa (Middle-East South Asia lineage) vaccine against challenge with O/VIT/2010 (O Mya98 lineage) was tested in pigs. Only two pigs that were vaccinated seven days prior to challenge had any demonstrable antibodies as a result of vaccination at the time of challenge. However, 80% and 60% of pigs that were vaccinated seven and four days prior to coronary band challenge were protected. Vaccination significantly reduced the amount of virus excreted in nasal swabs, saliva and faeces compared to unvaccinated and infected controls. Virus and viral RNA could be detected in some pigs until termination of the experiment 14 days after challenge. Antibodies to the non-structural proteins (NSP) were detected in only one pig that was challenged four days post vaccination (dpv) and transiently in two pigs that were challenged sevendpv at only one time point. For each vaccine and control group, a group of unvaccinated pigs were kept in the same room but with no direct contact with the infected pigs to determine whether vaccination prevented transmission. Despite the presence of live virus and viral RNA in these indirect contact pigs, the groups in contact with the vaccinated and infected pigs did not develop clinical signs nor did they sero-convert. Contact pigs in the same room as unvaccinated challenged controls did show signs of disease and virus infection that resulted in sero-conversion to the NSP. A breach of the wall that separated the two groups at nine days post challenge might have contributed to this finding. This study showed that high potency vaccine can provide protection to pigs soon after vaccination and that aerosol transmission within rooms is a rare event.

Evaluation of cross-protection between O1 Manisa and O1 Campos in cattle vaccinated with foot-and-mouth disease virus vaccine incorporating different payloads of inactivated O1 Manisa antigen.

Serology is used to predict vaccine induced protection against challenge with a heterologous strain of the same serotype of foot-and-mouth disease virus (FMDV). To evaluate the accuracy of such predictions, we compared the protection afforded to cattle vaccinated with the O(1) Manisa strain of FMDV against challenge with either a homologous (O(1) Manisa) or a heterologous strain (O(1) Campos). Serology by virus neutralization test (VNT) using O(1) Manisa antiserum predicted an acceptable protection against such a challenge. Two experiments were carried out to compare the results for consistency. A total of 78 naïve cattle were vaccinated with different antigen payloads (60-0.94 µg) of O(1) Manisa. They were challenged by intradermolingual inoculation with live FMDV, either O(1) Manisa or O(1) Campos. Unvaccinated naïve control cattle (n=20) were also challenged with either the O(1) Manisa or O(1) Campos viruses and all developed generalized FMD. The protection results for the vaccinated cattle revealed that higher payloads of O(1) Manisa vaccine were needed to protect against heterologous challenge compared to that for homologous challenge. The 50% protective dose (PD(50)) values for the vaccine in experiments 1 and 2 were found to be 28.78 and 9.44 for the homologous challenge and 3.98 and 5.01 for heterologous challenge. Furthermore, protection against O(1) Campos required a higher level of vaccine-induced antibody against this virus compared to the level of O(1) Manisa neutralizing antibody associated with protection against homologous challenge. The 50% protective level of in vitro neutralizing antibody was found to be log(10)1.827 for O(1) Campos and log(10)0.954 for O(1) Manisa based on O(1) Manisa based virus neutralization test.

Protection against direct in-contact challenge following foot-and-mouth disease vaccination in sheep and goats: the effect on virus excretion and carrier status.

The ability of foot-and-mouth disease (FMD) vaccine to protect sheep and goats from a homologous direct in-contact challenge and the effect on virus excretion from the nasal secretions and oropharynx was examined. An experimental oil adjuvant O(1) Manisa FMD vaccine protected sheep and goats from clinical disease from 7 days post vaccination following 24 hours of direct in-contact exposure to four infected donor sheep or goats. Goats required lower antibody titres for protection when compared with sheep. Protection from clinical disease did not prevent localized viral replication in goats and at least two goats had viral RNA detected on day 28 post challenge. Quantitative reverse transcriptase polymerase chain reaction showed that the level of virus replication shortly after direct in-contact challenge in oropharynx and nasal secretions of vaccinated animals was reduced by 100 and 1000 times respectively when compared with unvaccinated controls. The findings also show that after direct in-contact challenge, use of FMD vaccine will prevent or reduce local virus replication, thereby significantly reduce the amount of virus released into the environment in the all-important early post-exposure period. There is low risk of vaccinated animals transmitting disease as live virus could not be readily isolated.

Effect of FMD vaccine antigen payload on protection, sub-clinical infection and persistence following needle challenge in sheep.

The relationship of Foot-and-Mouth Disease (FMD) virus antigen payload and single and double vaccinations in conferring protection against virus challenge in sheep was studied. Sheep vaccinated with half the cattle dose (1 ml) containing 15 and 3.75 µg of FMDV antigen with or without booster resisted virulent challenge on 21 days post vaccination or 7 days post booster. FMDV RNA could be detected in nasal secretions in 26% of vaccinated sheep (10(3.12) to 10(3.82) viral RNA copies) on day 35 post challenge. No live virus could be isolated after 5 days post challenge indicating that the risk of transmission of disease was probably very low. The finding showed that vaccines containing antigen payload of 1.88 µg may prevent or reduce the local virus replication at the oropharynx and shedding of virus from nasal secretions and thereby reduce the amount of virus released into the environment subsequent to exposure to live virus. Sheep with no vaccination or with poor sero conversion to vaccination can be infected without overt clinical signs and became carriers.

Chimeric tymovirus-like particles displaying foot-and-mouth disease virus non-structural protein epitopes and its use for detection of FMDV-NSP antibodies.

Expression of Physalis mottle tymovirus (PhMV) coat protein (CP) in Escherichia coli (E. coli) was earlier shown to self-assemble into empty capsids that are nearly identical to the capsids formed in vivo. Aminoacid substitutions were made at the N-terminus of wild-type PhMV CP with single or tandem repeats of infection related B-cell epitopes of foot-and-mouth disease virus (FMDV) non-structural proteins (NSPs) 3B1, 3B2, 3AB, 3D and 3ABD of lengths 48, 66, 49, 51 and 55, respectively to produce chimeras pR-Ph-3B1, pR-Ph-3B2, pR-Ph- 3AB, pR-Ph-3D and pR-Ph-3ABD. Expression of these constructs in E. coli resulted in chimeric proteins which self-assembled into chimeric tymovirus-like particles (TVLPs), Ph-3B1, Ph-3B2, Ph-3AB, Ph-3D and Ph-3ABD as determined by ultracentrifugation and electron microscopy. Ph-3B1, Ph-3B2, Ph-3AB and Ph-3ABD reacted with polyclonal anti-3AB antibodies in ELISA and electroblot immunoassay, while wild-type PhMV TVLP and Ph-3D antigens did not react. An indirect ELISA (I-ELISA) was developed using Ph-3AB to detect FMDV-NSP antibodies in sera of animals that showed clinical signs of FMD. Field serum samples from cattle, buffalos, sheep, goats and pigs were examined by using these chimeric TVLPs for the differentiation of FMDV infected animals from vaccinated animals (DIVA). The assay was demonstrated to be highly specific (100%) and reproducible with sensitivity levels (94%) comparable to the Ceditest kit (P>0.05).

Molecular characterization of foot-and-mouth disease virus type C of Indian origin.

Comparison of nucleotide sequences of the partial 1D region of foot-and-mouth disease type C viruses of Indian origin with those of European, South American, and Southeast Asian viruses revealed that the Indian viruses form a distinct genotype. The vaccine strain C IND/51/79 belongs to this genotype and may be a prototype strain of this genotype.