ABSTRACT
Emergence of genetically and antigenically divergent lineages/genotypes and poor intergenotypic antigenic coverage is a major concern in serotype A foot-and-mouth-disease virus (FMDV) in India. In 2009, to cover antigenic diversity emerged in serotype A virus field isolates, IND40/2000 was selected as the new vaccine strain for incorporation in the trivalent FMD vaccine formulation used in India. Although current vaccine strain (IND40/2000) covers most isolates antigenically, a few VP3(59)-deletion group isolates showed low r-value in routine vaccine matching exercise. The VP3(59)-deletion group within genotype 18 emerged first in late part of 2002 and in 2007 causing outbreaks along with non-deletion isolates of the same genotype. In case of emergence or re-emergence of more antigenically divergent isolates in future, a need for a new vaccine candidate to cover maximum isolates of both deletion and non-deletion group may arise. Four alternate candidate vaccine strains (IND281/2003, IND195/2007, IND360/2007 and IND123/2008) were selected based on set criteria and antigenic relationships with field isolates sampled between 2002 and 2009 were analyzed using a micro-neutralization test. Phylogenetic analysis based on capsid region of serotype A isolates revealed existence of two broad distinct clusters (VP3(59)-deletion and non-deletion group) within genotype 18. The VP3(59)-deletion group has diversified genetically with time giving rise to three different sub-lineages (clade18a, 18b and 18c). The present study indicates that the virus candidates IND281/2003 (VP3(59)-deletion group) and IND195/2007 (non-deletion group) can be used as an adjunct or alternative strain to currently used vaccine strain IND40/2000 in case of emergence of more antigenically divergent isolates in future.
Subject(s)
Antigenic Variation/genetics , Antigens, Viral/genetics , Cattle Diseases/epidemiology , Cattle Diseases/virology , Foot-and-Mouth Disease Virus/genetics , Foot-and-Mouth Disease/epidemiology , Foot-and-Mouth Disease/prevention & control , Animals , Capsid Proteins/genetics , Cattle , Foot-and-Mouth Disease Virus/classification , Foot-and-Mouth Disease Virus/isolation & purification , India/epidemiology , Neutralization Tests , Phylogeny , Sequence Deletion , Viral VaccinesABSTRACT
Foot-and-mouth disease virus (FMDV) samples transported to the laboratory from far and inaccessible areas for serodiagnosis pose a major problem in a tropical country like India, where there is maximum temperature fluctuation. Inadequate storage methods lead to spoilage of FMDV samples collected from clinically positive animals in the field. Such samples are declared as non-typeable by the typing laboratories with the consequent loss of valuable epidemiological data. The present study evaluated the usefulness of FTA Classic Cards for the collection, shipment, storage and identification of the FMDV genome by RT-PCR and real-time RT-PCR. The stability of the viral RNA, the absence of infectivity and ease of processing the sample for molecular methods make the FTA cards a useful option for transport of FMDV genome for identification and serotyping. The method can be used routinely for FMDV research as it is economical and the cards can be transported easily in envelopes by regular document transport methods. Live virus cannot be isolated from samples collected in FTA cards, which is a limitation. This property can be viewed as an advantage as it limits the risk of transmission of live virus.
Subject(s)
Foot-and-Mouth Disease Virus/isolation & purification , Foot-and-Mouth Disease/diagnosis , Reverse Transcriptase Polymerase Chain Reaction/methods , Sampling Studies , Animals , Clinical Laboratory Techniques/standards , Foot-and-Mouth Disease Virus/genetics , RNA, Viral/genetics , RNA, Viral/isolation & purification , Sample Size , SerotypingABSTRACT
Laboratory detection of specific foot-and-mouth disease virus (FMDV) is routinely carried out by ELISA and RT-PCR. Identification and serotyping of FMDV by ELISA requires polyclonal antibodies raised in rabbits and guinea pigs. The polyclonal antibodies have certain disadvantages such as batch to batch variation, inconsistent yields of antibodies and limited quantity of serum obtained from individual animals. This paper describes a method wherein monoclonal antibodies and chicken IgY were used in an antigen capture-ELISA for serotyping of thirty tongue epithelial samples and sixty tissue culture fluids. The results were compared with the routine antigen detection ELISA. The present study indicated that monoclonal antibodies and chicken IgY can substitute conventional polyclonal antibodies for routine serotyping of FMDV.