Capsid coding region diversity of re-emerging lineage C foot-and-mouth disease virus serotype Asia1 from India.

Foot-and-mouth disease virus (FMDV) serotype Asia1 was first reported in India in 1951, where three major genetic lineages (B, C and D) of this serotype have been described until now. In this study, the capsid protein coding region of serotype Asia1 viruses (n = 99) from India were analyzed, giving importance to the viruses circulating since 2007. All of the isolates (n = 50) recovered during 2007-2013 were found to group within the re-emerging cluster of lineage C (designated as sublineage C(R)). The evolutionary rate of sublineage C(R) was estimated to be slightly higher than that of the serotype as a whole, and the time of the most recent common ancestor for this cluster was estimated to be approximately 2001. In comparison to the older isolates of lineage C (1993-2001), the re-emerging viruses showed variation at eight amino acid positions, including substitutions at the antigenically critical residues VP279 and VP2131. However, no direct correlation was found between sequence variations and antigenic relationships. The number of codons under positive selection and the nature of the selection pressure varied widely among the structural proteins, implying a heterogeneous pattern of evolution in serotype Asia1. While episodic diversifying selection appears to play a major role in shaping the evolution of VP1 and VP3, selection pressure acting on codons of VP2 is largely pervasive. Further, episodic positive selection appears to be responsible for the early diversification of lineage C. Recombination events identified in the structural protein coding region indicates its probable role in adaptive evolution of serotype Asia1 viruses.

Megaprimer-mediated capsid swapping for the construction of custom-engineered chimeric foot-and-mouth disease virus.

Foot-and-mouth disease (FMD) is a highly contagious, economically important disease of transboundary importance. Regular vaccination with chemically inactivated FMD vaccine is the major means of controlling the disease in endemic countries like India. However, the selection of appropriate candidate vaccine strain and its adaptation in cell culture to yield high titer of virus is a cumbersome process. An attractive approach to circumvent this tedious process is to replace the capsid coding sequence of an infectious full-genome length cDNA clone of a good vaccine strain with those of appropriate field strain, to produce custom-made chimeric FMD virus (FMDV). Nevertheless, the construction of chimeric virus can be difficult if the necessary endonuclease restriction sites are unavailable or unsuitable for swapping of the capsid sequence. Here we described an efficient method based on megaprimer-mediated capsid swapping for the construction of chimeric FMDV cDNA clones. Using FMDV vaccine strain A IND 40/2000 infectious clone (pA(40/2000)) as a donor plasmid, we exchanged the capsid sequence of pA(40/2000) with that of the viruses belonging to serotypes O (n = 5), A (n = 2), and Asia 1 (n = 2), and subsequently generated infectious FMDV from their respective chimeric cDNA clones. The chimeric viruses exhibited comparable infection kinetics, plaque phenotypes, antigenic profiles, and virion stability to the parental viruses. The results from this study suggest that megaprimer-based reverse genetics technology is useful for engineering chimeric vaccine strains for use in the control and prevention of FMD in endemic countries.

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

Foot-and-mouth disease (FMD) is a highly contagious, economically important disease of transboundary importance. Regular vaccination with chemically inactivated FMD vaccine is the major means of controlling the disease in endemic countries like India. However, the traditional inactivated vaccines may sometimes contain traces of FMD viral (FMDV) non-structural protein (NSP), therefore, interfering with the NSP-based serological discrimination between infected and vaccinated animals. The availability of marker vaccine for differentiating FMD infected from vaccinated animals (DIVA) would be crucial for the control and subsequent eradication of FMD in India. In this study, we constructed a negative marker FMDV serotype O virus (vaccine strain O IND R2/1975), containing dual deletions of amino acid residues 93-143 and 10-37 in the non-structural proteins 3A and 3B, respectively through reverse genetics approach. The negative marker virus exhibited similar growth kinetics and plaque morphology in cell culture as compared to the wild type virus. In addition, we also developed and evaluated an indirect ELISA (I-ELISA) targeted to the deleted 3AB NSP region (truncated 3AB) which could be used as a companion differential diagnostic assay. The diagnostic sensitivity and specificity of the truncated 3AB I-ELISA were found to be 95.5% and 96%, respectively. The results from this study suggest that the availability negative marker virus and companion diagnostic assay could open a promising new avenue for the application of DIVA compatible marker vaccine for the control of FMD in India.

Foot and Mouth Disease (FMD) incidence in cattle and buffaloes and its associated farm-level economic costs in endemic India.

The study investigated the important epidemiological parameters and farm-level economic costs of FMD incidence in cattle and buffaloes during 2013-14 to 2015-16 in various states of India. Multistage random sampling procedure was adopted for the primary survey and data was collected through face-to-face personal interview from 18,609 cattle and buffalo rearing farm households from 123 districts across twelve states and one Union Territory. Besides epidemiological parameters, different farm-level direct and indirect loss associated with FMD was assessed at disaggregated level (states) by employing deterministic mathematical models. Highest number of affected villages and disease incidence was observed in non- FMD control programme (FMD-CP) implemented Madhya Pradesh and Assam states, respectively whereas negligible incidence was in FMD-CP implemented Punjab state. The disease incidence was high during 2013-14 and declined during 2014-15 and 2015-16, respectively implied severe incidence scenario (2013-14) succeeded by moderate (2014-15) and mild (2015-16) scenarios. The crossbred and high productive animals were severely affected than local breeds whereas on sexwise and agewise comparison revealed higher incidence in females and adult animals. During severe incidence scenario, milk loss/animal ranged from USD 6.87-47.44, 18.42-125.88, 16.33-91.43, and 27.17-123.62; mortality loss/animal ranged from USD 32.61-804.27, 30.76-577.7, 65.36-502.2, and 188.04-413.7; distress sale loss/animal ranged from USD 3.22-188.63, 64.34-519.3, 214.47-341.8, and 209.11-450.3; and opportunity cost of labour/animal from USD 5.49-54.29, 5.49-67.78; 7.95-31.37 and 9.83-72.38 in indigenous cattle, crossbred cattle, local and improved buffalo, respectively. The estimated draught power loss/animal varied from USD 39.46-142.94 with least being in Madhya Pradesh and highest in Assam states whereas the median treatment cost/animal was USD 9.18 and USD 27.07 in indigenous cattle and upgraded buffaloes, respectively. The total farm-level economic loss projected due to FMD in cattle and buffaloes in India was USD 3159 million (INR 221,110 million), USD 270 million (INR 18,910 million) and USD 152 million (INR 10,610 million), respectively during the severe, moderate and mild incidence scenarios at 2015-16 constant prices. The loss varied across the states, and in severe incidence scenario, the country might lose USD 3.2 billion/year and hence, the bi-annual vaccination schedule need to be strictly implemented in all the states. Besides timely vaccination coverage, managing unabated animal movement, educating and motivating the farmers to vaccinate their animals might reduce the incidence and consequential losses to various stakeholders in endemic states like India.