In-process quality control in foot-and-mouth disease vaccine production by detection of viral non-structural proteins using chemiluminescence dot blot assay

Foot-and-mouth disease (FMD) is a contagious viral disease of cloven-footed animals. Immunization with inactivated virus vaccine is effective to control the disease. Six-monthly vaccination regimen in endemic regions has proven to be effective. To enable the differentiation of infected animals from those vaccinated, non-structural proteins (NSPs) are excluded during vaccine production. While the antibodies to structural proteins (SPs) could be observed both in vaccinated and infected animals, NSP antibodies are detectable only in natural infection. Quality control assays that detect NSPs in vaccine antigen preparations, are thus vital in the FMD vaccine manufacturing process. In this study, we designed a chemiluminescence dot blot assay to detect the 3A and 3B NSPs of FMDV. It is sensitive enough to detect up to 20 ng of the NSP, and exhibited specificity as it does not react with the viral SPs. This cost-effective assay holds promise in quality control assessment in FMD vaccine manufacturing.

Thermostable negative-marker foot-and-mouth disease virus serotype O induces protective immunity in guinea pigs

Foot-and-mouth disease (FMD) is a contagious viral disease of high economic importance, caused by FMD virus (FMDV), a positive-sense single-stranded RNA virus, affecting cloven-hoofed animals. Preventive vaccination using inactivated virus is in practice to control the disease in many endemic countries. While the vaccination induces antibodies mainly to structural proteins, the presence of antibodies to the non-structural proteins (NSP) is suggestive of infection, a criterion for differentiation of infected from vaccinated animals (DIVA). Also, there is a growing demand for enhancing the stability of the FMD vaccine virus capsid antigen as the strength of the immune response is proportional to the amount of intact 146S particles in the vaccine. Considering the need for a DIVA compliant stable vaccine, here we report generation and rescue of a thermostable and negative marker virus FMDV serotype O (IND/R2/1975) containing a partial deletion in non-structural protein 3A, generated by reverse genetics approach. Immunization of guinea pigs with the inactivated thermostable-negative marker virus antigen induced 91% protective immune response. Additionally, a companion competitive ELISA (cELISA) targeting the deleted 3A region was developed, which showed 92.3% sensitivity and 97% specificity, at cut-off value of 36% percent inhibition. The novel thermostable-negative marker FMDV serotype O vaccine strain and the companion cELISA could be useful in FMDV serotype O enzootic countries to benefit the FMD control program. KEY POINTS: • Thermostable foot-and-mouth disease virus serotype O with partial deletion in 3A. • Inactivated thermostable marker vaccine induced 91% protection in guinea pigs. • Companion cELISA based on deleted region in 3A could potentially facilitate DIVA.

Long-term protective immunity to goatpox in goats after a single immunization with a live attenuated goatpox vaccine

In this study, the duration of immunity following a single-dose vaccination using an attenuated live goatpox vaccine (GTPV/Uttarkashi/1978 strain) was evaluated in goatpox-seronegative goats for 52 months. Long-term immunity was evaluated by clinical protection upon virulent virus challenge and serum neutralization assay applied to serum samples. The rise in the level of GTPV-specific antibodies was found to reach a maximum at 21 days post-vaccination, and these antibodies were maintained for 1 to 2 years after immunization, with a steady decline. Upon virulent virus challenge at 12, 24, 42, and 52 months post-vaccination, protection in all the vaccinated animals was evident (100%), whereas, the control animals developed severe clinical disease. This is the first time that the long-term immunity of a live goatpox vaccine has been investigated up to 52 months after vaccination in goats by virulent virus challenge and demonstration of serum neutralization titres. This vaccine has immense potential for controlling and eradicating goatpox from an enzootic region.

The complete genome sequence of Indian sheeppox vaccine virus and comparative analysis with other capripoxviruses

Sheeppox virus (SPPV) is responsible for a significant economic loss to sheep husbandry in enzootic regions of Africa, the Middle East, and Asia including the Indian subcontinent. In this study, we present the complete genome sequence of SPPV vaccine strain SPPV-Srin38/00 from India determined by next-generation sequencing (NGS) using Illumina technology. The attenuated Srinagar vaccine strain of SPPV (SPPV-Srin38/00) was developed by serial passaging the virus initially in lamb testes (LT) cells followed by Vero cell line. The SPPV-Srin38/00 virus has a genome size of 150, 103 bp, which encodes for 147 functional putative genes and consists of a central coding region flanked by two identical 2353 bp inverted terminal repeats (ITRs). Comparative phylogenetic analysis based on complete genome sequences of Capripoxviruses formed three distinct groups each for SPPV, GTPV, and LSDV with clustering of SPPV-Srin38/00 strain with SPPV-A strain. Nine ORFs of SPPV-Srin38/00 namely SPPV-Srin_002/SPPV-Srin_155, SPPV-Srin_004/SPPV-Srin_153, SPPV-Srin_009, SPPV-Srin_013, SPPV-Srin_026, SPPV-Srin_132, and SPPV-Srin_136 were found to be fragmented as compared to LSDV, whereas only one ORF (such as SPPV-Srin_136) was found to be fragmented as compared to GTPV. SPPV genomes, including the SPPV-Srin38/00 strain, shared 99.78-99.98% intraspecies nucleotide identity, indicating that SPPV strains have extremely low genetic diversity. The strain shared 96.80-97.08% and 97.11-97.61% nt identity with GTPV and LSDV strains, respectively. Its ORFs 016, 021, 022, 130 and 138 are the least identical ORFs among three species of the genus Capripoxvirus with 72.5-93% aa identity to GTPV and LSDV strains and may be potentially used for differentiation of CaPV species. This study may contribute to a better understanding of the epidemiology and evolution of capripoxviruses as well as the development of specific detection methods, better expression vectors, and vaccines with improved safety and efficacy.

Ribavirin as a curative and prophylactic agent against foot and mouth disease virus infection in C57BL/6 suckling and adult mice model

Despite the availability of control measures for foot-and-mouth disease (FMD), the application of antiviral agents is imperative due to certain limitations in the prevention and control of FMD. This study pertains to systematic in vivo investigation of ribavirin as a prophylactic/curative agent, both in suckling and adult C57BL/6 mice against foot-and-mouth disease virus (FMDV) infection. In the adult mice, antiviral efficacy was assessed based on standard clinical score, body weight, and viral load. Only 13.33 to 33.33% of adult mice exhibited disease-specific symptoms following treatment and infection and vice versa, respectively, indicating the antiviral efficacy of the ribavirin. Further, the distribution of virus in different vital organs following ribavirin treatment and virus infection, and vice versa using SYBR green-based real-time PCR is reported. In the blood sample, the viral RNA was detected as early as two days post-infection and there was a significant reduction in virus titer (1000 to 10,000-folds) in the treatment groups compared to the infection control group. Animals receiving ribavirin had significantly lower organ virus titers at 2, 4, 6, 9, and 14 days post-challenge (dpc) than placebo-treated. In suckling mice, the treatment groups were 100% protected/cured compared to the control group. Thus, our data demonstrate that ribavirin may provide a feasible therapeutic approach to prevent as well as to treat FMDV infection.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13337-021-00746-8.

Infection and protection responses of deletion mutants of non-structural proteins of foot-and-mouth disease virus serotype Asia1 in guinea pigs

The development of a negative marker vaccine against the foot-and-mouth disease virus (FMDV) will enhance the capabilities to differentiate vaccinated from infected animals and move forward in the progressive control pathway for the control of FMD. Here, we report the development of mutant FMDV of Asia1 with partial deletion of non-structural proteins 3A and 3B and characterization of their infectivity and protection response in the guinea pig model. The deleted FMDV Asia1/IND/63/1972 mutants, pAsia^Δ3A and pAsia^Δ3A3B1 were constructed from the full-length infectious clone pAsia^WT, the viable virus was rescued, and the genetic stability of the mutants was confirmed by 20 monolayer passages in BHK21 cells. The mutant Asia1 viruses showed comparable growth pattern and infectivity with that of Asia^WT in the cell culture. However, the Asia^Δ3A3B1 virus showed smaller plaque and lower virus titer with reduced infectivity in the suckling mice. In guinea pigs, the Asia^Δ3A3B1 virus failed to induce the disease, whereas the Asia^Δ3A virus induced typical secondary lesions of FMD. Vaccination with inactivated Asia1 mutant viruses induced neutralizing antibody response that was significantly lower than that of the parent virus on day 28 post-vaccination (dpv) in guinea pigs (P < 0.05). Furthermore, challenging the vaccinated guinea pigs with the homologous vaccine strain of FMDV Asia1 conferred complete protection. It is concluded that the mutant Asia^Δ3A3B1 virus has the potential to replace the wild-type virus for use as a negative marker vaccine after assessing the vaccine worth attributes in suspension cell and protective efficacy study in cattle.Key points• Deletion mutant viruses of FMDV Asia1, developed by PCR-mediated mutagenesis of NSP 3A and 3B1, were genetically stable.• The growth kinetics and antigenic relatedness of the mutant viruses were comparable with that of the wild-type virus.• Vaccination of guinea pigs with the deletion mutant viruses conferred complete protection upon challenge with the homologous virus.

In vitro antiviral efficacy of pleconaril and ribavirin on foot-and-mouth disease virus replication

Antiviral therapy is a promising strategy to control acute viral infections. FMDV causes an acute infection and the vaccination provides a protective immunity 7 days post immunization. If the infection is uncontained, then it affects the entire herd. In such circumstances, if antiviral drug is administered the infection can be checked in a herd. Ribavirin is known to cure persistently infected BHK21 cells with FMD virus. However, there have been no systematic studies on antiviral activity of ribavirin against FMDV at different time points with the application of ELISA, PCR or real-time PCR. Pleconaril is known to inhibit enteroviruses and rhinoviruses but has not been explored on FMDV. Hence, the present study evaluates the in vitro antiviral efficacy of pleconaril and ribavirin on FMDV replication. The maximum non-toxic concentrations (MNTC) of pleconaril and ribavirin for BHK21 cells respectively were 7.81 μg/50 μL and 15.62 μg/50 μL. Thus, drug concentrations below MNTC were tested for their antiviral activity against serial tenfold diluted FMDV O, A and Asia 1 serotypes. Pleconaril did not inhibit FMDV serotype O replication at 7.5 μg/50 μL based on CPE inhibition assay and this was further confirmed using sandwich ELISA, PCR/real-time PCR. On the other hand, ribavirin at 15.62 μg/50 μL inhibited the in vitro replication of FMDV O, A and Asia 1 and the inhibition was confirmed by serotype specific sandwich ELISA, PCR and real-time PCR assays. The inhibition was directly proportional to the concentration of ribavirin. Therefore, ribavirin could be explored for its in vivo efficacy as a potential therapeutic in the prevention of early spread of FMDV infection in a herd.

Sequence analysis of haemagglutinin gene of camelpox viruses shows deletion leading to frameshift: Circulation of diverse clusters among camelpox viruses

Orthopoxviruses (OPVs) have broad host range infecting a variety of species along with gene-specific determinants. Several genes including haemagglutinin (HA) are used for differentiation of OPVs. Among poxviruses, OPVs are sole members encoding HA protein as part of extracellular enveloped virion membrane. Camelpox virus (CMLV) causes an important contagious disease affecting mainly young camels, endemic to Indian subcontinent, Africa and the Middle East. This study describes the sequence features and phylogenetic analysis of HA gene (homologue of VACV A56R) of Indian CMLV isolates. Comparative analysis of CMLV HA gene revealed conserved nature within CMLVs but considerable variability was observed between various species of OPVs. Most Indian CMLV isolates showed 99.5%-100% and 96.3%-100% identity, at nucleotide (nt) and amino acid (aa) levels respectively, among themselves and with CMLV-M96 strain. Importantly, Indian CMLV strains along with CMLV-M96 showed deletion of seven nucleotides resulting in frameshift mutation at C-terminus of HA protein. Phylogenetic analysis displayed distinct clustering among CMLVs which might point to the circulation of diverse CMLV strains in nature. Despite different host specificity of OPVs, comparative sequence analysis of HA protein showed highly conserved N-terminal Ig V-set functional domain with tandem repeats. Understanding of molecular diversity of CMLVs and structural domains of HA protein will help in the elucidation of molecular mechanisms for immune evasion and design of novel antivirals for OPVs.

Red flour beetle (Tribolium castaneum): From population genetics to functional genomics

Tribolium castaneum is a small and low maintenance beetle that has emerged as a most suitable insect model for studying developmental biology and functional genetic analysis. Diverse population genetic studies have been conducted using Tribolium as the principal model to establish basic facts and principles of inbreeding experiments and response to the selection and other quantitative genetics fundamentals. The advanced molecular genetic studies presently focused on the use of Tribolium as a typical invertebrate model for higher diploid eukaryotes. After a whole genome sequencing of Tribolium, many areas of functional genomics were unraveled, which enabled the use of it in many technical approaches of genomics. The present text reviews the use of Tribolium in techniques such as RNAi, transgenic studies, immune priming, immunohistochemistry, in situ hybridization, gene sequencing for characterization of microRNAs, and gene editing using engineered endonuclease. In contrast to Drosophila, the T. castaneum holds a robust systemic RNAi response, which makes it an excellent model for comparative functional genetic studies.

Copy number variation in livestock: A mini review

Copy number variation (CNV) is a phenomenon in which sections of the genome, ranging from one kilo base pair (Kb) to several million base pairs (Mb), are repeated and the number of repeats vary between the individuals in a population. It is an important source of genetic variation in an individual which is now being utilized rather than single nucleotide polymorphisms (SNPs), as it covers the more genomic region. CNVs alter the gene expression and change the phenotype of an individual due to deletion and duplication of genes in the copy number variation regions (CNVRs). Earlier, researchers extensively utilized SNPs as the main source of genetic variation. But now, the focus is on identification of CNVs associated with complex traits. With the recent advances and reduction in the cost of sequencing, arrays are developed for genotyping which cover the maximum number of SNPs at a time that can be used for detection of CNVRs and underlying quantitative trait loci (QTL) for the complex traits to accelerate genetic improvement. CNV studies are also being carried out to understand the evolutionary mechanism in the domestication of livestock and their adaptation to the different environmental conditions. The main aim of the study is to review the available data on CNV and its role in genetic variation among the livestock.

Comparative efficacy of chemical stabilizers on the thermostabilization of a novel live attenuated buffalopox vaccine

In the present investigation, the thermostability of a live attenuated buffalopox vaccine prepared with an indigenous baffalopox virus isolate (BPXV Vij/96) and freeze-dried under conventional lyophilizing conditions is described. Three different stabilizer combinations like LS (lactalbumin hydralysate + sucrose), LHT (lactalbumin hydralysate + Trehalose dihydrate) and TAA (Trehalose dihydrate + l- Alanine + l-Histidine) were used to prepare the vaccine. The study indicated that the LS stabilizer was found to be the stabilizer of choice followed by LHT and TAA for buffalopox vaccine at all temperatures studied. The presence of stabilizers has beneficial influence in preserving the keeping quality of the vaccine. Further, among the diluents used to reconstitute the freeze-dried buffalopox vaccine, double distilled water, 0.85% normal saline solution and phosphate buffer saline were the choice of diluents in that order. However, 1M MgSO₄ did not perform well at higher temperatures. Investigation suggests for using LS as a stabilizer for freeze-drying and any of the three diluents except 1MgSO₄ for reconstitution of buffalopox vaccine.

RT-LAMP assay: an alternative approach for profiling of bovine heat shock protein 70 gene in PBMC cultured model

The purpose of this study is to develop a novel Reverse Transcriptase Loop-mediated isothermal amplification (RT-LAMP) based assay for in vitro profiling of heat shock protein 70 (Hsp70) in bovine peripheral blood mononuclear cell (PBMC) culture model utilizing the absorbance level of magnesium pyrophosphate-a by-product of LAMP reaction. A set of bovine Hsp70 specific RT-LAMP primers were designed to detect the differential absorbance level of magnesium pyrophosphate by-product which signifies the degree of Hsp70 amplification from cDNA of thermally induced cultured cells at different recovery periods. The study revealed significant (P < 0.05) correlation between absorbance level and the fold change of Hsp70 transcripts at different kinetic intervals of heat stress recovery in bovine PBMC cell culture models. RT-LAMP based absorbance assay can be used as an indicator to measure the degree of bovine Hsp70 transcripts produced during thermal stress and can be used as an alternative to the traditional Real time PCR assay. Developed RT-LAMP assay can be used as a cost-effective method for profiling of bovine HSP70 gene.

Comparative expression profile of NOD1/2 and certain acute inflammatory cytokines in thermal-stressed cell culture model of native and crossbred cattle

Thermotolerance depends mainly on the health and immune status of the animals. The variation in the immune status of the animals may alter the level of tolerance of animals exposed to heat or cold stress. The present study was conducted to investigate the expression profile of two important nucleotide binding and oligomerization domain receptors (NLRs) (NOD1 and NOD2) and their central signalling molecule RIP2 gene during in vitro thermal-stressed bovine peripheral blood mononuclear cells (PBMCs) of native (Sahiwal) and crossbred (Sahiwal X HF) cattle. We also examined the differential expression profile of certain acute inflammatory cytokines in in vitro thermal-stressed PBMC culture among native and its crossbred counterparts. Results revealed that the expression profile of NOD1/2 positively correlates with the thermal stress, signalling molecule and cytokines. Present findings also highlighted that the expression patterns during thermal stress were comparatively superior among indigenous compared to crossbred cattle which may add references regarding the better immune adaptability of Zebu cattle.

Co-administration of recombinant major envelope proteins (rA27L and rH3L) of buffalopox virus provides enhanced immunogenicity and protective efficacy in animal models

Buffalopox virus (BPXV) and other vaccinia-like viruses (VLVs) are causing an emerging/re-emerging zoonosis affecting buffaloes, cattle and humans in India and other countries. A27L and H3L are immuno-dominant major envelope proteins of intracellular mature virion (IMV) of orthopoxviruses (OPVs) and are highly conserved with an ability to elicit neutralizing antibodies. In the present study, two recombinant proteins namely; rA27L (₂₁S to E₁₁₀; ∼30 kDa) and rH3L(₁M to I₂₈₀; ∼50 kDa) of BPXV-Vij/96 produced from Escherichia coli were used in vaccine formulation. A combined recombinant subunit vaccine comprising rA27L and rH3L antigens (10 μg of each) was used for active immunization of adult mice (20μg/dose/mice) with or without adjuvant (FCA/FIA) by intramuscular route. Immune responses revealed a gradual increase in antigen specific serum IgG as well as neutralizing antibody titers measured by using indirect-ELISA and serum neutralization test (SNT) respectively, which were higher as compared to that elicited by individual antigens. Suckling mice passively administered with combined anti-A27L and anti-H3L sera showed a complete (100%) pre-exposure protection upon challenge with virulent BPXV. Conclusively, this study highlights the potential utility of rA27L and rH3L proteins as safer candidate prophylactic antigens in combined recombinant subunit vaccine for buffalopox as well as passive protective efficacy of combined sera in employing better pre-exposure protection against virulent BPXV.

Synergistic effect of high-mobility group box-1 and lipopolysaccharide on cytokine induction in bovine peripheral blood mononuclear cells

High-mobility group box 1 (HMGB1) is one of the potent endogenous adjuvants released by necrotic and activated innate immune cells. HMGB1 modulates innate and adaptive immune responses in humans and mice by mediating immune cells crosstalk. However, the immuno-modulatory effects of HMGB1 in the bovine immune system are not clearly known. In this study, the effect of bovine HMGB1 alone or in combination with LPS on the expression kinetics of cytokines upon in vitro stimulation of bovine peripheral blood mononuclear cells (PBMCs) was investigated by quantitative PCR assay. The biological activity of bovine HMGB1 expressed in this prokaryotic expression system was confirmed by its ability to induce nitric oxide secretion in RAW 264.7 cells. The present results indicate that HMGB1 induces a more delayed TNF-α response than does LPS in stimulated PBMCs. However, IFN-γ, IFN-β and IL-12 mRNA transcription peaked at 6 hr post stimulation after both treatments. Further, HMGB1 and LPS heterocomplex up-regulated TNF-α, IFN-γ and IL-12 mRNA expression significantly than did individual TLR4 agonists. The heterocomplex also enhanced the expression of TLR4 on bovine PBMCs. In conclusion, the data indicate that HMGB1 and LPS act synergistically and enhance proinflammatory cytokines, thereby eliciting Th1 responses in bovine PBMCs. These results suggest that HMGB1 can act as an adjuvant in modulating the bovine immune system and thus lays a foundation for using HMGB1 as an adjuvant in various bovine vaccine preparations.

Differential effect of thermal stress on HSP70 expression, nitric oxide production and cell proliferation among native and crossbred dairy cattle

In a tropical country like India, thermal stress is one of the major factors which significantly affects the productivity of dairy cattle. The present study was aimed to identify the effect of heat and cold stress on cell viability, mitogen stimulation indices, nitric oxide production and HSP70 expression in Sahiwal and Holstein crossbred (Frieswal) population in India. The results indicated that the Sahiwal breed can better withstand the effect of heat and cold stress significantly (P<0.05) when compared to the crossbred cattle due to the higher survivability of the Peripheral Blood Mononuclear Cells (PBMCs) and Phytohemagglutinin (PHA-P) mitogen based stimulation indices. The study also revealed the significant differences (P<0.05) in the level of nitric oxide (µM) production amongst the pre and post thermal stressed samples of Sahiwal and Frieswal crossbred samples. Further, the expression of HSP70 was significantly (P<0.05) higher in Sahiwal compared to Frieswal immediately after heat/cold shock to 6h of recovery as indirect ELISA analysis showed gradual rise in the Hsp70 protein concentration (ng/ml) immediately after heat and cold stress (0h) and reached the peak at 6h of recovery. Western blot and immune fluorescent assay results were also corroborated with the findings of indirect ELISA. In Sahiwal cattle the mRNA expression of HSP70 and its protein concentration were higher (P<0.05) during peak summer (44°C) and winter (10°C) as compared to Frieswal cattle. This investigation supports the earlier information on the higher adaptability of indigenous cattle breeds to hot and humid conditions compared to the crossbreds of temperate cattle breeds.

Expression of bovine interleukin 15 and evaluation of its biological activity in vitro

BACKGROUND/AIM

Recent studies have shown that interleukin-15 (IL-15)is a critical factor for the development and proliferation of CD8(+) memory T cells. The aim of present study is to study the role bovine IL-15 (bIL-15)in activation pathway of bovine CD8(+) T cells if any, which will be useful in designing the adjuvant to increase the duration of immunity of the vaccine preparations.

MATERIALS AND METHODS

Coding region of bIL-15 (489) was amplified from cDNA of lipopolysaccharide-induced bovine peripheral blood mononuclear cells (PBMCs) using gene specific primers and cloned into pcDNA3.1(+). Mature length of bIL-15 was amplified using gene specific primers and cloned into pET32a for expression studies. Expressed fusion protein was purified using Ni-Nitrilotriacetic acid agarose affinity chromatography and analyzed by SDS-Polyacryamide gel electrophoresis (PAGE) and western blotting. Biological activity of purified protein was analyzed by quantitative Polymerase Chain Reaction (qPCR) for an increase in levels of Bcl2, STAT3 and STAT5a using cDNA synthesized from RNA of PBMCs induced with different concentrations of purified bIL-15. Role of IL-15 in inducing memory CD8(+) T cells was analyzed by qPCR for increase in the level of Carnitine Palmitoyl Transferase 1a (CPT1a) using cDNA synthesized from RNA of PBMCs induced with different concentrations of purified bIL-15.

RESULTS

Bovine IL-15 was amplified and analyzed by agarose gel electrophoresis, which showed a specific product of ~490bp, mature sequence was amplified using full-length as a template to get a product of ~350bp. The protein was expressed, purified and analyzed by SDS-PAGE and Western blotting, which showed a specific product of 32kDa. Biological activity of purified bIL-15 fusion protein showed an increase in levels of Bcl2, STAT3 and STAT5a with 5 fold, 9 fold, and 10 fold increases as analyzed by qPCR, respectively. Role of IL-15 in inducing memory T cells showed an increase in expression level of CPT1a at 2.5 fold increase as compared to control cells.

CONCLUSION

Bovine IL-15 has been successfully cloned and expressed in our work, and the biological activity shows that the purified fusion protein is biologically active. As there is an increase in levels of CPT1a an enzyme critical for survival of memory T cells, IL-15 can be used for increase in the memory response, which can be used as an adjuvant with viral vaccines for increasing the immunity.

Bacterial Ghosts of Escherichia coli Drive Efficient Maturation of Bovine Monocyte-Derived Dendritic Cells

Bacterial ghosts (BGs) are empty cell envelopes derived from Gram-negative bacteria. They not only represent a potential platform for development of novel vaccines but also provide a tool for efficient adjuvant and antigen delivery system. In the present study, we investigated the interaction between BGs of Escherichia coli (E. coli) and bovine monocyte-derived dendritic cells (MoDCs). MoDCs are highly potent antigen-presenting cells and have the potential to act as a powerful tool for manipulating the immune system. We generated bovine MoDCs in vitro from blood monocytes using E. coli expressed bovine GM-CSF and IL-4 cytokines. These MoDCs displayed typical morphology and functions similar to DCs. We further investigated the E. coli BGs to induce maturation of bovine MoDCs in comparison to E. coli lipopolysaccharide (LPS). We observed the maturation marker molecules such as MHC-II, CD80 and CD86 were induced early and at higher levels in BG stimulated MoDCs as compared to the LPS stimulated MoDCs. BG mediated stimulation induced significantly higher levels of cytokine expression in bovine MoDCs than LPS. Both pro-inflammatory (IL-12 and TNF-α) and anti-inflammatory (IL-10) cytokines were induced in MoDCs after BGs stimulation. We further analysed the effects of BGs on the bovine MoDCs in an allogenic mixed lymphocyte reaction (MLR). We found the BG-treated bovine MoDCs had significantly (p<0.05) higher capacity to stimulate allogenic T cell proliferation in MLR as compared to the LPS. Taken together, these findings demonstrate the E. coli BGs induce a strong activation and maturation of bovine MoDCs.

Development and comparative evaluation of loop mediated isothermal amplification (LAMP) assay for simple visual detection of orf virus in sheep and goats

A loop-mediated isothermal amplification (LAMP) assay targeting DNA Pol gene was optimized and evaluated for the rapid detection of orf virus in clinical samples. The LAMP assay was found to be specific and sensitive. The detection rate of LAMP (89.3%) was better than PCR (67.9%) and comparable to real-time PCR (91.1%) in clinical samples by gel electrophoresis and visual detection methods. This LAMP assay is simple and does not rely upon any special equipment and could be employed in clinical diagnosis and epidemiological survey of orf infection.

Evaluation of thermo-stability of bluetongue virus recombinant VP7 antigen in indirect ELISA

This study shows the thermo-stability of lyophilized and purified recombinant VP7 bluetongue virus (BTV) protein in the presence of two sugar stabilizers (trehalose and mannitol) at different temperature. Truncated VP7 protein purified by nickel affinity column was lyophilized in the presence of trehalose and mannitol at 60 mM final concentration and then exposed to different temperature like 4, 25, 37 and 45 °C for various periods like 5 months, 7 weeks, 7 days and 48 h, respectively. After thermal treatment, the reactivity of the protein was evaluated in indirect ELISA. At 4 and 25 °C, the protein was stable up to 5 months and 7 weeks, respectively, irrespective of stabilizers used. At 37 °C, it was stable up to 3 days with both the stabilizers, after which it lost its stability and reactivity. At 45 °C, the protein was stable up to 30 and 24 h with trehalose and mannitol stabilizers, respectively. Both stabilizers found suitable for stability of the protein. However, trehalose appeared to have better stabilizing effect, particularly at higher temperatures than the mannitol. Trehalose could be used as stabilizer for freeze-drying the recombinant VP7 protein if an indirect ELISA kit based on the purified rVP7 protein is supplied to different laboratories of the country for detection of BTV antibody in sheep.

Detection of subclinical peste des petits ruminants virus infection in experimental cattle

The present study was undertaken to investigate the possible involvement of cattle in the epidemiology of peste des petits ruminants (PPR) as subclinical carriers. Cattle were exposed experimentally to PPR virus (PPRV) infection or placed in contact with PPR infected goats. Clinical samples including heparinized/EDTA blood, plasma, peripheral blood monocyte cells (PBMCs) and clotted blood (for serum) were collected periodically from 21 days post infection (dpi) to 397 dpi (21, 45, 50, 57, 65, 95, 111, 119, 148, 190, 203 and 397 dpi) and tested for PPRV antigen, nucleic acid and antibody. Exposed cattle seroconverted and maintained PPRV specific haemagglutinin antibodies and detectable PPRV antigen/nucleic acid in blood, plasma and PBMCs from 21 to 397 dpi. PPRV was recovered from blood and PBMC collected from experimental animals at 21 dpi, initially in B95a cells and then adapted to Vero cells. The study indicated that PPRV can infect cattle subclinically and PPRV antigen/nucleic acid persist in cattle for at least 397 days.

Protective immune response of live attenuated thermo-adapted peste des petits ruminants vaccine in goats

Virulent isolate of peste des petits ruminants virus (PPRV) of Indian origin (PPRV Jhansi 2003) initially adapted in Vero cells was further propagated in thermo-adapted (Ta) Vero cells grown at 40 °C for attaining thermo-adaption and attenuation of virus for development of Ta vaccine against PPR in goats and sheep. The virus was attenuated up to 50 passages in Ta Vero cells, at which, the virus was found sterile, innocuous in mice and guinea pigs and safe in seronegative goats and sheep. The developed vaccine was tested for its immunogenicity in goats and sheep by subcutaneous inoculation of 100 TCID50 (0.1 field dose), 10(3) TCID50 (one field dose) and 10(5) TCID50 (100 field doses) of the attenuated virus along with controls as per OIE described protocols for PPR vaccine testing and were assessed for PPRV-specific antibodies 7-28 days post vaccination (dpv) by PPR competitive ELISA and serum neutralization tests. The PPRV antibodies were detected in all immunized goats and sheep and goats were protective when challenged with virulent PPRV at 28th dpv along with controls for potency testing of the vaccine. The attenuated vaccine did not induce any adverse reaction at high dose (10(5) TCID50) in goats and sheep and provided complete protection even at low dose (10(2) TCID50) in goats when challenged with virulent virus. There was no shedding and horizontal transmission of the attenuated virus to in-contact controls. The results indicate that the developed PPR Ta attenuated virus is innocuous, safe, immunogenic and potent or efficacious vaccine candidate alternative to the existing vaccines for the protection of goats and sheep against PPR in the tropical countries like India.

TaqMan based real-time duplex PCR for simultaneous detection and quantitation of capripox and orf virus genomes in clinical samples

A rapid and sensitive TaqMan based real-time duplex PCR (drt-PCR) assay for simultaneous detection, differentiation and quantitation of Capripoxvirus (CaPV) and Orf virus (ORFV) DNA, was optimized targeting the highly conserved DNA polymerase genes of these virus genomes. Two pairs of oligonucleotide primers and two hybridization probes labeled with Cy5/BHQ1 and Hex/BHQ1 for CaPV and ORFV, respectively, were used in the drt-PCR assay. The assay was found to be specific only to targeted viruses and did not react with buffalopox virus (BPXV), camelpox virus (CMLV) (Orthopoxviruses) and cDNA of Peste des petits ruminants virus and bluetongue virus, the other common viruses of sheep and goats. The detection limit of the assay was 20 copies for each of the standard plasmid and 35fg of viral genomic DNA for CaPV and ORFV, respectively, in a single and mixed virus population. Both intra-(0.49-4.6% and 0.7-3.7%) and inter-(0.6-2.35% and 0.27-2.1%) assay variations of drt-PCR for CaPV and ORFV DNA were within the acceptable limits, implying high reproducibility and repeatability of the assay. Further, the diagnostic specificity and the sensitivity of the assay was assessed using known virus isolates of sheeppox virus (SPPV), goatpox virus (GTPV) and ORFV and the clinical specimens from sheep and goats. The developed drt-PCR assay was able to detect, differentiate, quantify simultaneously and also to identity mixed infections of CaPV and ORFV in sheep and goats.

Prevalence of Peste-des-petits-ruminant virus antibodies in cattle, buffaloes, sheep and goats in India

The present study describes the prevalence of Peste-des-petits-ruminant virus (PPRV) antibodies in cattle, buffaloes, sheep and goats carried out during the period 2011 using the serum samples randomly collected from different villages of five states of India. A total of 1,498 serum samples [n = 605 (cattle); n = 432 (buffaloes); n = 173 (sheep); n = 288 (goats)] were collected from 52 districts in five states (Andhra Pradesh, Gujarat, Jammu and Kashmir, Maharashtra and Rajasthan) of India and were screened for PPRV-specific antibodies by using PPR monoclonal antibody-based competitive ELISA kit. Analysis of 1,498 samples indicates that an overall seroprevalence of 21.83 % with 11.07 % in cattle, 16.20 % in buffaloes, 45.66 % in sheep and 38.54 % in goats. This report presents the results of PPRV-specific antibodies in situations where the subclinical, inapparent or nonlethal or recovery of infection was suspected in cattle, buffaloes, sheep and goats. The presence of PPRV antibodies demonstrate that bovines are exposed to PPRV infection and it implies the importance of cattle and buffaloes as subclinical hosts for the virus besides widespread presence of the disease in sheep and goats. Further, the study showed that the prevalence of PPRV antibodies in apparently healthy livestock under natural situation, 21.83 % of the animals were protected from PPRV re-infection. This inturn help in the implementation of disease control strategies such as vaccination in that particular geographical area.

Multiplex PCR for simultaneous detection and differentiation of sheeppox, goatpox and orf viruses from clinical samples of sheep and goats

A multiplex polymerase chain reaction (mPCR) was developed and evaluated for detection of pox viral infections simultaneously using clinical samples from sheep and goats. Specific primers for three pox viruses of sheep and goats including sheeppox virus (SPPV), goatpox virus (GTPV) and orf virus (ORFV) were designed targeting conserved sequences of the DNA binding phosphoprotein (I3L) coding gene of Capripoxvirus (CaPV) and the DNA polymerase (E9L) gene of parapoxvirus for identification of these viruses. The mPCR assay was found to be sensitive for detecting as low as 350 pg of viral genomic DNA or 10(2) copies of standard plasmid of individual targets; and 10(3) copies of plasmid in a mixture of two or three viruses. The assay was specific for detecting one or more of the viruses in various combinations from clinical specimens. Two hundred and thirty five (n=235) clinical samples from sheep and goats received from different geographical regions of the country for diagnosis of pox infection were evaluated by developed uniplex and mPCR assays. The assay had improved diagnostic sensitivity and specificity over to in-use laboratory diagnostic methods and can be useful for clinical differential diagnosis of these infections in sheep and goats.

Comparative immunogenicity of two peste des petitis ruminants (PPR) vaccines in South Indian sheep and goats under field conditions

Peste des petitis ruminants (PPR) is an economically important endemic viral disease of sheep and goats in India, where several different homologous PPR vaccine candidates have been developed. We evaluated the serological response to two vaccine strains, Arasur/87 and Sungri/96, in South Indian cross-bred and native sheep and goats reared under organized and unorganized settings. Animals seronegative (percent inhibition or PI <40) by competitive enzyme-linked immunosorbent assay (c-ELISA) were immunized with either of the vaccine strains or placebo. Sera collected on 21, 60 and 90 days post-vaccination were subjected to c-ELISA and serum neutralization test (SNT). Seropositivity (PI >40), seroconversion (fourfold increase in SNT titres) and seroprotection (SNT titre of ≥8 deemed to be protective) ranged from 66.7 to 84.0 %, 56.0 to 69.2 %, and 60.0 to 76.0 %, respectively. However, no significant difference was observed between responses to the two vaccine strains. These results support the premise that the two vaccine strains are equally efficacious.

Co-administration of flagellin augments immune responses to inactivated foot-and-mouth disease virus (FMDV) antigen

Foot-and-mouth disease virus (FMDV) is one of the most contagious animal virus known that affects livestock health and production. This study aimed to investigate the effect of flagellin, a toll-like receptor 5 agonist, on the immune responses to inactivated FMDV antigen in guinea pig model. Our results showed that the co-administration of flagellin with FMDV antigen through intradermal route induces earlier and higher anti-FMDV neutralizing antibody responses as compared to FMDV antigen alone. Both IgG1 and IgG2 antibody-isotype responses were enhanced, but the IgG1/IgG2 ratios were relatively low, indicative of TH1 type of immune activation. On live viral challenge, flagellin+FMDV immunized guinea pigs showed 70% (7 out of 10) protection rate as compared to 40% (4 out of 10) in FMDV alone immunized guinea pigs. The results demonstrate that the co-administration of flagellin augments immune responses (preferably TH1 type) and protective efficacy against FMDV in guinea pigs.

Animal poxvirus vaccines: a comprehensive review

The family Poxviridae includes several viruses of medical and veterinary importance. Global concerted efforts combined with an intensive mass-vaccination campaign with highly efficaceious live vaccine of vaccinia virus have led to eradication of smallpox. However, orthopoxviruses affecting domestic animals continue to cause outbreaks in several endemic countries. Different kinds of vaccines starting from conventional inactivated/attenuated to recombinant protein-based vaccines have been used for control of poxvirus infections. Live virus homologous vaccines are currently in use for diseases including capripox, parapox, camelpox and fowlpox, and these vaccines are highly effective in eliciting (with the exception of parapoxviruses) long-lasting immunity. Attenuated strains of poxviruses have been exploited as vectored vaccines to deliver heterologous immunogens, many of them being licensed for use in animals. Worthy of note are vaccinia virus, fowlpox virus, capripoxvirus, parapoxvirus and canary pox, which have been successfully used for developing new-generation vaccines targeting many important pathogens. Remarkable features of these vaccines are thermostability and their ability to engender both cellular and humoral immune responses to the target pathogens. This article updates the important vaccines available for poxviruses of livestock and identifies some of the research gaps in the present context of poxvirus research.

Analgesic, Antibacterial and Antiviral Activities of 2-(5-Alkyl-1,3,4-oxadiazol-2-yl)-3H-benzo[f]chromen-3-ones

A novel series of 2-(5-alkyl-1,3,4-oxadiazol-2-yl)-3H-benzo[f]chromen-3-ones (4a-e) have been evaluated for analgesic, antibacterial and antiviral activities. Analgesic activity was carried out using acetic acid-induced writhing method in Swiss albino male mice. The antibacterial activity was performed against Gram-positive and Gram-negative clinical strains by agar well diffusion method. The in vitro antiviral activity was carried out against camelpox and buffalopox viruses. The analgesic activity exhibited by the compounds 4a, 4c and 4d were found to be more significant compared to the standard. The bacterial activity was determined by the inhibition of growth of the organism by the drugs at different concentrations. All the compounds showed significant activity when compared with the drug ciprofloxacin. The in vitro antiviral activity of the compound 4b tested against camelpox and buffalopox viruses revealed no activity when tested at concentrations of 250 μg. The compound 4b did not alter the titres of both the viruses and the titres remain, respectively, 10^6.5 TCID₅₀ and 10^6.74 TCID₅₀ per ml for camelpox vaccine virus and buffalopox vaccine virus. However, the compounds 4a-e showed significant analgesic and antibacterial activities.

Expression, purification, and functional characterisation of flagellin, a TLR5-ligand

Flagellin, a Toll-like receptor 5 (TLR5)-ligand, is known for its activities like adjuvant, induction of pro-inflammatory cytokines and innate immunity. In this context, fliC gene of Salmonella Typhimurium was cloned into pET32a expression plasmid using in-house designed gene specific primers. The frame and orientation of the inserted fliC gene was confirmed upon colony PCR, restriction enzyme analysis and sequencing. Sequence analysis of fliC revealed proper orientation of the gene and had 1,485 nucleotides. Following transformation of pET-fliC plasmid into Escherichia coli BL21 (DE3) cells, the gene was expressed after inducing with IPTG (Isopropylβ-D-1-thiogalactopyranoside). The polyHis-tag-fliC was ~70kDa as confirmed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The identity/authenticity of the recombinant-fliC was confirmed by its specific reactivity with commercial anti-fliC MAb of S. Typhimurium. Further, the antigenic and functional properties of recombinant-fliC were determined espousing its ability to induce antigen specific antibodies in G pigs and increased m-RNA expression of certain pro-inflammatory mediators like TNF-α and GM-CSF in vitro.

Prevalence of peste des petits ruminants among sheep and goats in India

This study measured the clinical prevalence of peste des petits ruminants (PPR) among sheep and goats in India between 2003 and 2009 by analyzing clinical samples from suspected cases of PPR that were submitted to the Rinderpest and Allied Disease Laboratory, Division of Virology, IVRI, Mukteswar for PPR diagnosis. PPR outbreaks were confirmed by detecting PPR virus (PPRV)-specific antigen in the clinical samples. Clinical samples (blood, nasal swabs, spleen, lymph node, kidney, liver, intestine, and pooled tissue materials) were taken from a total of 592 sheep and 912 goats in different states of India and screened for the presence of PPRV antigen using a monoclonal antibody-based sandwich ELISA kit. A total of 20, 38, and 11 laboratory-confirmed PPR outbreaks occurred among sheep, goat, and combined sheep and goat populations, respectively. Our findings provide evidence of widespread PPR endemicity in India. The underlying reasons could be variations in husbandry practices in different geographical regions, agro-climatic conditions, and livestock migration. Furthermore, decrease in the number of PPR outbreaks over time might be due to the effectiveness of current live PPR vaccines and timely vaccination of target species. Vaccination against PPR has been practiced in India since 2002 to control this disease.

Sero-epidemiological study of peste des petits ruminants in sheep and goats in India between 2003 and 2009

This study describes the serosurveillance of peste des petits ruminants (PPR) in sheep and goats that was carried out between 2003 and 2009 using serum samples from animals suspected of PPR that were submitted to the Rinderpest and Allied Disease Laboratory (Division of Virology of the Indian Veterinary Research Institute [IVRI]). A total of 2,197 serum samples from sheep and 2,687 from goats were screened for PPR virus (PPRV) antibody using a monoclonal antibody-based competitive enzyme-linked immunosorbent assay developed at IVRI. Screening of the 4,884 serum samples showed that the prevalence of PPRV antibody in sheep and goats was 41.01% (95% confidence interval [CI]: 31.86 to 50.16) and 46.11% (95% CI: 37.18 to 55.04), respectively, with an overall prevalence of 43.56% (95% CI: 36.78 to 50.34) during the period. This indicates increased and widespread infection with the virus in India compared with earlier reports, which is attributed to the variations in sheep and goat husbandry practices in different regions, the agro-climatic conditions, the topography of different states, the socio-economic status of individual farmers and the migration of livestock in India.

Differentiation of sheeppox and goatpox viruses by polymerase Chain reaction-restriction fragment length polymorphism

In the present study, the partial gene sequences of P32 protein, an immunogenic envelope protein of Capripoxviruses (CaPV), were analyzed to assess the genetic relationship among sheeppox and goatpox virus isolates, and restriction enzyme specific PCR-RFLP was developed to differentiate CaPV strains. A total of six goatpox virus (GTPV) and nine sheeppox virus (SPPV) isolates of Indian origin were included in the sequence analysis of the attachment gene. The sequence analysis revealed a high degree of sequence identity among all the Indian SPPV and GTPV isolates at both nucleotide and amino acid levels. Phylogenetic analysis showed three distinct clusters of SPPV, GTPV and Lumpy skin disease virus (LSDV) isolates. Further, multiple sequence alignment revealed a unique change at G120A in all GTPV isolates resulting in the formation of Dra I restriction site in lieu of EcoR I, which is present in SPPV isolates studied. This change was unique and exploited to develop restriction enzyme specific PCR-RFLP for detection and differentiation of SPPV and GTPV strains. The optimized PCR-RFLP was validated using a total of fourteen (n=14) cell culture isolates and twenty two (n=22) known clinical samples of CaPV. The Restriction Enzyme specific PCR-RFLP to differentiate both species will allow a rapid differential diagnosis during CaPV outbreaks particularly in mixed flocks of sheep and goats and could be an adjunct/supportive tool for complete gene or virus genome sequencing methods.

Peste des petits ruminants virus detected in tissues from an Asiatic lion (Panthera leo persica) belongs to Asian lineage IV

In this study, peste des petits ruminants virus (PPRV) was detected in frozen pooled tissue samples from a dead Asiatic lion (Panthera leo persica). The samples were negative for canine distemper virus and positive for PPRV nucleic acids when tested with one-step RT-PCR using the appropriate virus-specific primers. Subsequent amplification, cloning, and sequencing of the partial nucleocapsid, matrix, and fusion genes confirmed the presence of PPRV nucleic acid. Comparative sequence and phylogenetic analyses of the structural genes of the isolated virus confirmed that the virus belonged to Asian lineage IV and was closely related to PPRV circulating in India.

Quantitative polymerase chain reaction: another tool to evaluate viable virus content in live attenuated orf vaccine

A probe-based real-time polymerase chain reaction (PCR) assay based on the highly conserved DNA polymerase gene of orf virus (ORFV) for the quality control of attenuated orf vaccine is reported. Primary lamb testis (PLT) cells were infected with orf vaccine virus and harvested at a critical time point to obtain maximum viable virus content as determined by real-time PCR. DNA extracted from these harvests was subjected to real-time PCR. A critical time point for the harvesting of PLT cells infected with various log(10) dilutions of vaccine virus was found to be 42 h (highest slope of 3.335), which was obtained by comparing the slopes of standard curves of different time intervals. The assay was employed to evaluate viable virus content in different batches of orf vaccine. The titres estimated by real-time PCR and conventional TCID(50) were comparable with a correlation of 0.8169. Thus, the real-time PCR assay could provide an alternative method or supplementary tool to estimate live ORFV particles in attenuated orf vaccine.

Cytokines expression profile and kinetics of Peste des petits ruminants virus antigen and antibody in infected and vaccinated goats

The present study deals with the co-ordination of cytokine (IL-4 and IFN-γ) expression and kinetics of peste des petits ruminants (PPR) virus antigen and antibody in PPRV infected and vaccinated goats. The infected animals exhibited mixed cytokine (both T(H)1 and T(H)2) responses in the initial phase of the disease. The infected and dead goats had increased IFN-γ response before their death; while IL-4 remained at the base level. The cytokine expression in recovered animals was almost similar to that of vaccinated ones, where a unique biphasic response of IL-4 expression was observed with an up-regulation of IFN-γ on 7(th) days post vaccination (dpv). Analysis of PPR virus antigen and antibody kinetics in different components of blood from infected and vaccinated animals revealed that the PPR virus antigen load was highest in plasma followed by serum and blood of the infected animals, whereas vaccinated animals showed only marginal positivity on 9(th) dpv. The antibody titer was high in serum followed by plasma and blood in both vaccinated and infected animals. Therefore, it is inferred that the presence of antigen and antibody were significant with the expression of cytokine, and that a decreased response of IL-4 was noticed during intermediate phase of the disease i.e., 7 to 12(th) days post infection (dpi). This indicates the ability to mount a functional T(H)2 response after 14(th) dpi could be a critical determinant in deciding the survival of the PPR infected animal.

Study on passive immunity: Time of vaccination in kids born to goats vaccinated against Peste des petits ruminants

In this study, the decay of maternal peste des petits ruminants virus (PPRV) antibodies in kids born to goats vaccinated with Asian lineage IV PPR vaccine and the efficacy of passive immunity against PPRV was assessed to determine the appropriate period for vaccination in kids. Serum samples collected from kids born to vaccinated, unvaccinated and infected goats at different time intervals were tested by PPR competitive ELISA and serum neutralization test (SNT). Maternal antibodies in kids were detectable up to 6 months with a decline trend from the third month onwards and receded below the protective level by the fourth month. The kid with an SN titre of 1:8 at the time of immunization showed significant PPRV specific antibody response (percentage inhibition of 76; SN titers >1:16), when tested on 21 day post-vaccination and was completely protected from infection upon virulent PPRV challenge. Similarly, the kid with 1:8 SN titers was completely protected from PPR infection on active challenge. Therefore, PPR vaccination is recommended in kids, aged 4 months and born to immunized or exposed goats. This could be a suitable period to avoid window of susceptibility in kids to PPRV and the effort to eliminate PPR infection from susceptible populations.

Emergence and reemergence of vaccinia-like viruses: global scenario and perspectives

Among the members of the genus Orthopoxvirus (OPXV), vaccinia virus (VACV), the type species of the genus is a double-stranded DNA virus, belongs to the subfamily Chordopoxvirinae of the family Poxviridae. The causative agents of smallpox, VACV and Variola virus are mutually immunogenic and the type species of Orthopoxvirus, cause only mild complications in humans. Therefore, the VACV was used as a smallpox vaccine world over under mass immunization program promoted by World Health Organization, which lead to the variola eradication globally in 1979. Since then, no vaccination of human population has been carried out; however, vaccination has been continued for at-risk laboratory workers, military personnel and others working with recombinant VACV or other non-variola orthopoxviruses (OPXVs). There has now been a surge in the development of safer smallpox vaccines and understanding of the biology of VACV necessitating re-use of this vaccine in most vulnerable population, because of rise in bioterrorist threats globally. Also, globally there has been the emergence and re-emergence of vaccinia-like viruses (VLVs) in Brazil, buffalopox viruses in Egypt, Indonesia, India and its neighbouring countries like Nepal, Pakistan. Bioterrorism as well as emergence and re-emergence of the VLVs constitute a concern as 50 % of the population globally (40 % in USA) <30 years are unvaccinated and most vulnerable for smallpox reemergence. Thus, the search for new generation safer smallpox vaccine entails review of biology of VLVs in the smallpox-free world. In this review, we present occurrence of VLVs in the world with exhaustive discussion particularly on the emergence and re-emergence of these viruses in India and Brazil where VLVs are sufficiently studied.