Brucella melitensis: Divergence Among Indian Strains and Genetic Characterization of a Strain Isolated from Cattle.

Brucella melitensis primarily affects sheep, goats and is associated with brucellosis in humans, which is one of the world's most widespread neglected zoonotic disease. The current study attempted the determination of genetic diversity through comparative genome analysis of B. melitensis strains reported from India with other countries. The study also reports the isolation and identification of B. melitensis BMNDDB8664 from a cow with a history of abortion, whole-genome sequencing (WGS), determination of virulence factors, genotyping, and comparative genome analysis. Multilocus sequence typing, Multiple locus variable number of tandem repeats analysis (MLVA), and WGS based phylogeny revealed the predominance of ST-8 and genotypes (116 and II respectively) that clustered to the East Mediterranean lineage. Identification of hitherto unreported genotypes by MLVA also indicated the existence and circulation of West Mediterranean and American lineages in India. Though the AMOS-PCR results suggest the BMNDDB8664 isolate as Brucella abortus, the outcomes from multiplex PCR, ribosomal multilocus sequence typing, and WGS analysis confirmed it as B. melitensis. The analysis revealed the presence of adeF gene (aids conferring resistance to fluoro-quinolone and tetracyclines). The isolate lacked two important T4SS genes virB2 and virB7 genes (roles in infection and rifampicin resistance respectively) and also lacked the Brucella suis mprF gene that aids intracellular survival. Further, BMNDDB8664 lacked some of the genes associated with LPS synthesis (wbkB, wbkC) and transport (wzm, wzt) and hence, is most likely a rough strain. WGS-based phylogenetic analysis revealed close genetic relatedness of this BMNDDB8664 with a sheep isolate and two human isolates. The results prompt systematic, broad-based epidemiological studies on brucella infection at the species level. For effective control of human brucellosis, a concerted One Health approach with studies encircling the identification of aetiology at species, strain level to find their prevalence, spread, and inter-host transmission patterns need to be understood, for better design and implementation of effective control strategies in India and other endemic regions. Supplementary Information: The online version contains supplementary material available at 10.1007/s12088-023-01081-w.

E6 protein of human papillomavirus 16 (HPV16) expressed in Escherichia coli sans a stretch of hydrophobic amino acids, enables purification of GST-ΔE6 in the soluble form and retains the binding ability to p53.

Recombinant E6 expressed in Escherichia coli is known to form recalcitrant inclusion bodies even when fused to the soluble GST protein. This study describes the modification of the HPV genotype-16 oncogenic protein E6 in order to obtain it in the soluble form. The modified protein (ΔE6) was expressed in E. coli BL21 as an N-terminal fusion with GST (GST-ΔE6). ΔE6 was constructed by deleting the nucleotide sequences coding for IHDIIL (31-36 a.a), one of the highly hydrophobic peptide stretches, using splicing by overextension polymerase chain reaction (SOE-PCR). The removal of IHDIIL residues rendered the GST-ΔE6 soluble and amenable for purification involving a two step process a preliminary glutathione-GST affinity chromatography followed by gel-filtration chromatography. Evaluation of purified protein fractions by HPLC suggests that GST-ΔE6 exists as a monomer. Further, the ΔE6 in GST-ΔE6 seemed to retain the binding ability to p53 as determined by the glutathione-GST capture ELISA. Purified GST-ΔE6 we reckon, might find use as an essential reagent in immunological assays, in sero-epidemiological studies, and also in studies to delineate the structure and function of HPV16 E6.

Evaluation of commercial ELISA kits for diagnosis of brucellosis in cattle and buffaloes in different epidemiological scenarios.

Seven ELISA kits were evaluated for the fitness of purpose in diagnosing brucellosis among cattle and buffaloes in the endemic scenarios of India. The sera (675 numbers) for the study were sourced from brucellosis-free as well as infected herds. The diagnostic sensitivity (dsn) and specificity (dsp) of the kits were determined by three approaches: based on the results of the Rose Bengal test, history of the animals (sera from infected or naïve animals), and based on the results obtained from the 'majority of the tests'. The dsn and dsp ranged from 65.10% to 98.66%, and 98.04% to 100% respectively. The results and suitability of the kits for diagnostic application in various epidemiological situations were discussed.

Detection and genetic characterization indicates circulation of a possible new Theileria species (Theileria sp. Yokoyama) in India.

Bovine tropical theileriosis, a tick-borne disease, causes huge economic loss to the Indian dairy industry. Theileriosis in India is mainly caused by Theileria annulata, although the presence of T. orientalis has also been reported. The present study was undertaken to investigate the deaths of cross-bred Holstein Friesen (CBHF) cows on a farm in the state of Telangana, India. Deceased animals had recently calved and prior to death had developed high fever (107 °F) and anaemia. Infected cows were infested with ticks (Hyalomma species). Theileria piroplasms were noticed in the Giemsa stained blood smears. PCR assays further confirmed the presence of Theileria in the blood samples of the infected cows. Partial Tams1 gene sequences from the infected animals shared 99.87% to 100% identity scores with the sequences of Sri Lankan isolates recently proposed as a novel Theileria species (provisionally designated as Theileria sp. Yokoyama). To the best of our knowledge, this is the first report of the novel species of Theileria from India. Infected animals were effectively treated with buparvaquone and oxytetracycline. The introduction of new animals into the farm without risk assessment was found to be a major cause of the outbreak.

Prevalence of antibodies to Anaplasma in cattle and buffaloes of different organized herds in India.

Bovine anaplasmosis is one of the most important tick borne disease in ruminants causing huge economic loss to the dairy industry. A cross-sectional study was carried out to detect serum antibodies to Anaplasma infection in cattle and buffaloes housed in 14 organized herds located at various climatic zones spreading over 9 different states in India. A total of 911 serum samples, collected from 667 cattle and 244 buffaloes, were subjected to a competitive enzyme linked immune-sorbent assay detecting an epitope of major surface protein 5 (MSP5) of Anaplasma. The overall true prevalence was 48.72% (95% CI 45.13-52.32%). The prevalence rate was higher in cattle (51.58%) than buffaloes (40.89%) and the difference was statistically significant (p < 0.05). Indigenous cattle (59.30%) showed higher seropositivity than crossbreed (57.16%) and exotic cattle breeds (42.28%). Although statistically not significant, female (52.37%) showed higher seropositivity than male (46.43%). Similarly, significant difference in prevalence (p < 0.05) was observed for animals reared in different climatic zones with highest prevalence recorded in arid zone (90.49%) and lowest in semi-arid zone (29.83%). Very wide variation in prevalence (9.95-100%) was recorded between farms. The present study indicates endemicity of Anaplasma in India, similar to other tropical and sub-tropical countries of the world. Endemic instability was recorded in some of the studied farms suggesting possibility of outbreak of new clinical cases resulting in economic loss. Therefore, suitable policies and procedures for prevention and control of Anaplasma infection should be adopted in these farms.

Sero-diagnostic efficacy of various ELISA kits for diagnosis of infectious bovine rhinotracheitis (IBR) in cattle and buffaloes in India.

Bovine alphaherpesvirus-1 (BoHV-1), the causative agent of infectious bovine rhinotracheitis (IBR), is an economically important viral pathogen affecting cattle and buffaloes. Serological assays are mostly used for detection of the antibodies, but variation has been detected in the diagnostic performances of the individual assay. In the present study, four commercially available ELISA kits {two indirect ELISA (kits A and B) and two blocking ELISA (kits C and D)} were evaluated for the detection of antibodies against BoHV-1 in Indian cattle and buffaloes (fitness of purpose). The diagnostic sensitivity (dsn) and specificity (dsp) of these kits were determined by three ways; considering virus neutralization test (VNT) as gold standard test, using pre-test information of the samples, and majority of tests. Screening of 200 known negative sera (124 cattle, 76 buffaloes) sourced from IBR free farms revealed gB based ELISA kits are more specific than the indirect ELISA kits. Testing of 125 known positive sera (81 cattle, 44 buffaloes) suggests kit B be most sensitive followed by kit C, A and D. Interestingly, kit D was found to be most sensitive for detection of vaccination-induced BoHV-1 antibodies followed by kit B. Similar trend were also observed in the limit of dilution experiment performed using known infected and vaccinated sera. VNT was found to be the most specific test and its use as the gold standard test revealed all kits to have more than 99 % sensitivity. All the ELISA kits could detect BoHV-1 specific antibodies in the IBR vaccinated calves as early as 11 days post-vaccination. In Kappa statistics, an almost perfect agreement between the ELISA kits was recorded. The overall performance of the kits in serodiagnosis of IBR as determined by the area under curve in ROC analysis was good.

Infectious bovine abortions: observations from an organized dairy herd.

Abortions in dairy animals can be caused by several infectious agents. Identification of the actual causal agent(s) is important for formulating suitable control strategies. A 3-year (2016-2018) longitudinal study was conducted in a dairy farm following an abortion storm in the mid- to late gestations. The investigation focused on the seven major infectious abortifacient in cattle, viz. bovine alphaherpesvirus-1 (BoHV-1), bovine viral diarrhoea virus (BVDV), Neospora caninum, Brucella abortus, Coxiella burnetii, Leptospira Hardjo, and Listeria monocytogenes. High seroprevalence was observed for BVDV (79.4%), Leptospira (70.5%), BoHV-1 (53.5%), and Brucella (45.0%) at the beginning of the investigation (August 2016). The incidence proportion increased for BVDV, Leptospira, and Brucella in the following years of the investigation. A strong association of Brucella seropositivity with history of abortion (OR = 3.27) was recorded. Incidence of BoHV-1 reduced during the period of study coincident with systematic IBR inactivated marker vaccination of the herd. Sixty-four abortion cases were investigated for the identification of causative agent(s) by microbial culture, serological (ELISA), and molecular detection (PCR/ real-time PCR). Antibodies to BVDV, Brucella, BoHV-1, Leptospira, Neospora, and Coxiella were detected in 63, 61, 56, 35, 5, and 6 aborting cattle, respectively. Real-time PCR/PCR of clinical specimens detected DNA of Brucella, BoHV-1, Coxiella, Leptospira, and Listeria in 34, 13, 12, 9, and 4 abortion cases, respectively. BVDV and Neospora were not detected in any specimen samples. Brucella abortus isolated from the farm was determined as ST1 by multi-locus sequence typing (MLST). DNA of multiple agents were detected in 21 of the 64 cases (43.75%). Overall, the data suggests, Brucella was the major causative agent, although multiple causative agents circulated in the farm.

Prevalence of brucellosis and infectious bovine rhinotracheitis in organized dairy farms in India.

This study was carried out to investigate the prevalence of bovine brucellosis and infectious bovine rhinotracheitis (IBR) in organized dairy farms with history of abortion in India. ELISA and Rose Bengal Plate Test (RBPT) were used to detect the seropositive animals and the test results indicated that 22.18% and 13.78% animals were declared as sero-positive by ELISA and RBPT, respectively. Milk Ring Test (MRT) was carried out only in one farm and 12.82% of the tested animals were turned positive. Culture examination analysis of milk samples, two animals revealed the presence of organisms indistinguishable from Brucella spp. The organism was confirmed as brucella by morphological characteristics and biochemical tests. An overall sero-prevalence of antibodies against IBR was found to be 60.84%. None of the genital and nasal swab samples was found to be positive for presence of bovine herpesvirus -1 (BHV-1) on repeated passage in Madin-Darby Bovine Kidney (MDBK) cell lines. Brucella and IBR considered as the causal agent for abortions in these farms. The present study indicates the urgent need and the necessity for control of these infectious diseases which cause heavy economic losses to the organized farms.

Development and laboratory validation of duplex real-time PCR for simultaneous detection of Brucella and bovine alphaherpesvirus from clinical specimens.

A duplex real­time PCR was developed and validated for the simultaneous detection of Brucella and bovine alphaherpesvirus­1 (BoHV­1) from bovine clinical specimens. The bcsp31 gene of Brucella and gB gene of BoHV­1 were used as targets in the assay. The limit of detection for BoHV­1 was 0.03 TCID50 of virus and 10 plasmid copies containing the target gene while for Brucella it was 4.1 × 101 CFUs. Intra­assay and inter­assay values showed high repeatability and reproducibility of the assay. The diagnostic sensitivity (dsn) and diagnostic specificity (dsp) of the duplex assay were determined by screening 443 clinical specimens and comparing the results with the respective individual assays. The dsn and dsp for detection of Brucella were found to be 95.24% and 95.65%, respectively whereas for BoHV­1, the dsn (100%) and dsp (99.47%) were slightly higher. The duplex assay had a very good degree of agreement with the respective individual real­time PCR test {kappa value 0.97 for Brucella and 0.95 for BoHV­1}. The results of the current study suggest that the duplex assay would be a cost­effective and time­saving alternative for the individual real­time PCR assay for the detection of Brucella and BoHV­1.

Shedding of bovine alphaherpesvirus-1 in bovine extended frozen semen in Indian semen stations: A longitudinal analysis.

Infectious bovine rhinotracheitis (IBR) caused by bovine alphaherpesvirus 1 (BoHV-1) is an economically important disease of cattle and buffaloes. Following acute infection, the virus usually attains latency in the sensory neurons. Stress-induced reactivation of latency can cause the infected animals to intermittently shed the virus in body secretions including semen. A longitudinal analysis was carried out to study BoHV-1 shedding in the semen of IBR seropositive cattle and buffaloes. The study involved data generated from the screening of 119,850 extended frozen semen (EFS) batches, collected from 1,229 IBR seropositive bulls, over a period of four years (April 2015 to March 2019). A TaqMan based real-time PCR assay was employed to detect the gB gene BoHV-1 DNA in the EFS batch samples. Each sample was tested in duplicate and amplification in any of the replicates at or below the threshold cycle (Ct ≤ 40) was considered positive. The overall positivity of BoHV-1 in EFS batches was 1.18%. About 41% of the bulls (509 of 1,229) were found to have excreted the virus in semen at least once during the study period. The frequency of viral shedding in buffaloes (0.96%) was significantly lower than that of cattle (1.3%) (p < 0.001). No significant difference was noted in the rate of shedding between the first and the second ejaculates collected on the same day (p = 0.607). The rate of shedding also did not vary among various breeds of cattle (p = 0.454) or with the age of the bulls (p = 0.054). No significant variation in the shedding rate was observed in cattle across different seasons (p = 0.101); while in buffaloes, the rate was higher in autumn (1.2%) than in winter (0.7%) (p = 0.037). The difference in positivity among semen stations was statistically significant (p < 0.001). Analysis of data revealed that ≥100 EFS batch samples/bull were screened from 361 of the 1,229 bulls included in the study. None of the EFS batches screened from 39 of these 361 bulls were found positive during the four years, suggesting they were non-shedders. Further research is warranted to delineate the underlying features of the seropositive non-shedders; following which an adequate risk assessment may be made for the maintenance of infected but non-shedding bulls in semen production.

Development and characterization of monoclonal antibodies against FMD virus type Asia-1 and determination of antigenic variations in the field strains.

Twelve mouse monoclonal antibodies (MAbs) were developed against an Indian vaccine strain of foot and mouth disease virus (FMDV) type Asia-1 WBN 117/85. The MAbs were tested for their ability to bind to whole virus particle, trypsin-treated 146S (TT-146S) virus particle, sub-viral (12S and disrupted virus) antigens by ELISA and to neutralize virus infectivity in cell culture. Extensive characterization of MAbs revealed the existence of three different groups based on the binding of non-overlapping epitopes. Eight type Asia-1 specific MAbs (RF7, RF8, RD10, RE11, RC11, RC10/O, RB11 and RC10/M), which formed group 1 (G1), were found to bind a neutralizing, trypsin-sensitive (TS) and conformational epitope. Two MAbs (WB8 and WC3) in group 2 (G2) were found to bind a non-neutralizing, trypsin-resistant, conformational and 12S-specific epitope, which was intertypically conserved in all the four serotypes of FMDV (O, A, C and Asia-1) prevalent in India. Two MAbs (KG10 and KF10), which formed group 3 (G3), were found to be against a non-neutralizing, TS and conformational epitope, common to types Asia-1 and A. Members of G1 were IgG2a isotype, while those of G2 and G3 were IgG1 and IgG2b isotypes, respectively. Antigenic analysis of 31 FMDV type Asia-1 field isolates and two vaccine strains, using a panel of type Asia-1-specific MAbs, revealed antigenic similarity of the virus isolates tested and non-existence of neutralization escape mutants. The developed MAbs have practical utility, especially in the manufacture of FMD vaccine, diagnosis and FMDV characterization.

Evaluation of a specialized filter-paper matrix for transportation of extended bovine semen to screen for bovine herpesvirus-1 by real-time PCR.

The extended frozen semen (EFS) batches produced from infectious bovine rhinotracheitis (IBR) sero-positive cattle and buffalo bulls housed in various semen stations in India are transported to the testing laboratory in liquid nitrogen (LN2) for screening bovine herpesvirus-1 (BoHV-1). This procedure is laborious and poses LN2 related hazards. An alternative logistics for transportation of samples was investigated. Use of Flinders Technology Associates (FTA®) elute card was evaluated for transportation of extended bovine semen to screen BoHV-1 DNA by real-time PCR targeting gB gene and the method was compared with the OIE approved Chelex resin based method. A protocol for extraction of BoHV-1 DNA from FTA® card spotted with extended semen was optimized. The viral DNA was found to be stable on FTA® card for at least 28 days when the cards are stored at 4°-37 °C. The analytical sensitivity for the assay was determined using variable dilutions of BoHV-1 spiked semen and positive plasmid harbouring gB gene (97bp) spotted onto FTA® card and it was found to be 100.8 TCID50/ml or 100 copies respectively in real-time PCR. The test could detect as low as 100.008 TCID50/ml or 1 copy of positive plasmid when more number of replicates (n = 6) of the same sample were tested. This sensitivity was found to be comparable to Chelex method and both the methods demonstrated a very strong correlation (r = 0.9774; 95% CI: 0.9620-0.9860) in terms of Ct value (p < 0.0001). The diagnostic sensitivity and specificity of the FTA method in comparison to the Chelex method was 83.08% (95% CI: 71.73%-91.24%) and 93.23% (95% CI: 89.38%-96.01%) respectively when 316 samples were screened by both the methods. The degree of agreement between these two tests was good (Kappa value: 0.738; 95% CI: 0.646-0.829). The method was found to be robust and highly repeatable in inter-assay and intra-assay precision testing. The result suggests that the FTA® card holds promise as an alternative system for transportation of EFS for downstream screening of BoHV-1 DNA.

Direct typing of Canine parvovirus (CPV) from infected dog faeces by rapid mini sequencing technique.

Canine parvovirus (CPV) is a non-enveloped single stranded DNA virus with an icosahedral capsid. Mini-sequencing based CPV typing was developed earlier to detect and differentiate all the CPV types and FPV in a single reaction. This technique was further evaluated in the present study by performing the mini-sequencing directly from fecal samples which avoided tedious virus isolation steps by cell culture system. Fecal swab samples were collected from 84 dogs with enteritis symptoms, suggestive of parvoviral infection from different locations across India. Seventy six of these samples were positive by PCR; the subsequent mini-sequencing reaction typed 74 of them as type 2a virus, and 2 samples as type 2b. Additionally, 25 of the positive samples were typed by cycle sequencing of PCR products. Direct CPV typing from fecal samples using mini-sequencing showed 100% correlation with CPV typing by cycle sequencing. Moreover, CPV typing was achieved by mini-sequencing even with faintly positive PCR amplicons which was not possible by cycle sequencing. Therefore, the mini-sequencing technique is recommended for regular epidemiological follow up of CPV types, since the technique is rapid, highly sensitive and high capacity method for CPV typing.

Typing of canine parvovirus isolates using mini-sequencing based single nucleotide polymorphism analysis.

The antigenic types of canine parvovirus (CPV) are defined based on differences in the amino acids of the major capsid protein VP2. Type specificity is conferred by a limited number of amino acid changes and in particular by few nucleotide substitutions. PCR based methods are not particularly suitable for typing circulating variants which differ in a few specific nucleotide substitutions. Assays for determining SNPs can detect efficiently nucleotide substitutions and can thus be adapted to identify CPV types. In the present study, CPV typing was performed by single nucleotide extension using the mini-sequencing technique. A mini-sequencing signature was established for all the four CPV types (CPV2, 2a, 2b and 2c) and feline panleukopenia virus. The CPV typing using the mini-sequencing reaction was performed for 13 CPV field isolates and the two vaccine strains available in our repository. All the isolates had been typed earlier by full-length sequencing of the VP2 gene. The typing results obtained from mini-sequencing matched completely with that of sequencing. Typing could be achieved with less than 100 copies of standard plasmid DNA constructs or ≤10¹ FAID50 of virus by mini-sequencing technique. The technique was also efficient for detecting multiple types in mixed infections.

Development of foot-and-mouth disease virus (FMDV) serotype O virus-like-particles (VLPs) vaccine and evaluation of its potency.

Foot-and-mouth disease (FMD) is an economically significant viral disease that rampage dairy and other livestock industries in many countries. The disease is being controlled by the use of an inactivated vaccine. However, a recombinant marker vaccine, which avoids the use of live virus, may be an option for the unambiguous differentiation of infected animals from vaccinated animals. A recombinant baculovirus clone containing P1-2A-3C coding sequences of foot-and-mouth disease virus (FMDV) serotype O(1) Manisa was generated. The FMDV structural proteins along with the 3C protease were expressed in Sf9 cells and the generation of virus like particles (VLP) was studied. The recombinant protein was formulated as vaccine using an oil adjuvant, ISA 206 and potency of the vaccine was tested in cattle. The vaccine had a potency value (PD(50)) of 5.01 and most of the vaccinated animals exhibited neutralizing antibody titers after two immunizations.

Use of real-time polymerase chain reaction to detect bovine herpesvirus 1 in frozen cattle and buffalo semen in India.

Bovine herpesvirus 1 (BoHV-1) infection in cattle and buffalo makes these animals life-long carriers of the virus which is intermittently excreted in semen. In the present study, a real-time polymerase chain reaction (PCR) was validated to screen frozen semen from cattle and buffalo for BoHV-1 by amplification of the gB gene of the virus. Analysing the intra- and inter-test variability, the assay was found to be highly reproducible. High sensitivity (100%) and specificity (90.04%) of this real-time PCR assay was recorded in comparison to virus isolation. Extended frozen semen samples from 574 cattle and buffalo bulls that were seropositive to infectious bovine rhinotracheitis (IBR) tested by real-time PCR indicated that 1.97% semen batches from cattle and 3.36% batches of buffalo semen were positive for BoHV-1. The real-time PCR protocol will be useful for screening large numbers of semen samples from IBR-seropositive cattle and buffalo bulls as the test is less time consuming and several batches of semen can be tested with ease compared to virus isolation in cell culture.

Partial sequence analysis of VP1 of Indian isolates of foot-and-mouth disease virus type Asia-1.

Nucleotide sequence of 3' end of VP1 (1D region) was determined using RT-PCR amplified DNA of 31 foot and mouth disease virus (FMDV) type Asia-1 field isolates originating from 11 different geographically distinct states of India during the period 1987-2000. These field strains exhibited an average of 7.5% divergence among them and were found to be divergent from the Indian vaccine strains Asia-1 WBN 117/85, IND 8/79, and IND 63/72, by an average 5.9, 14.8, and 7.4% divergence, respectively. Phylogenetic analysis of these 31 field isolates including 3 of the vaccine strains of India and sequences of 22 Indian field isolates obtained from the GenBank revealed that all the Indian FMDV type Asia-1 isolates belonged to a single genotype comprising of two distinct lineages (Lineages A and B). All the field isolates under study belonged to the Lineage-B comprising 8 different clusters, which also includes the vaccine strains WBN-117/85 and IND 8/79. Surprisingly, another vaccine strain IND 63/72 formed Lineage-A. Phylogenetic analysis of sequences of another 23 exotic type Asia-1 isolates from 15 different countries obtained from the GenBank along with the 56 Indian isolates revealed the existence of three distinct genotypes. The prototype strain Asia-1 PAK 1/54 belongs to a separate genotype. Two strains from India along with one strain each from China and Russia belongs to another genotype. The third genotype is formed by the remaining isolates including all the 31 isolates from the present study and exotic viruses from 14 other different countries. Comparison of deduced amino acid (aa) sequence indicated that majority of the mutations were found within two distinct regions corresponding to amino acid positions 130-160 and 193-211. The motif at aa positions 138-141 in vaccine strains WBN 117/85, IND 8/79 and in all the field isolates was ETTS/P; however, the same motif in IND 63/72 was TQPT. The motif 153-156 in majority of Indian isolates including vaccine strains WBN 117/85 and IND 8/79 was LSGQ/R whereas the same motif seen in IND 63/72 was VSNR. The study revealed that the FMDV type Asia-1 isolates circulating in the country are not highly heterogeneous, but showed considerable genetic variations. Certain mutations were also observed in the residues, which have been proved to be contributing to the formation of neutralizing epitopes. In neutralization studies employing polyclonal antisera, type Asia-1 WBN 117/85 revealed broader serological spectrum than other vaccine strains of India used in this study.