Characterization of immunoglobulin and cytokine responses in Burkholderia mallei infected equids.

Burkholderia mallei causes a highly fatal infectious disease in equines known as glanders. It is one of the OIE listed notifiable diseases, which entails strict control policy measures once B. mallei infection is confirmed in the susceptible hosts. Humans, especially equine handlers, veterinary professionals and laboratory workers are at greater risk to acquire the B. mallei infection directly through prolonged contact with glanderous equines, and indirectly through unprotected handling of B. mallei contaminated materials. Further, natural resistance of B. mallei to multiple antibiotics, aerosol transmission, lack of effective vaccine and treatment make this organism a potential agent of biological warfare. Results of experimental B. mallei infection in mouse and non-human primates and immunization with live attenuated B. mallei strains demonstrated that activation of early innate and adaptive immune responses play a critical role in controlling B. mallei infection. However, the immune response elicited by the primary hosts (equids) B. mallei infection is poorly understood. Therefore, we aimed to investigate immune responses in glanders affected horses (n = 23) and mules (n = 1). In this study, chronically infected equids showed strong humoral responses (IgM, IgG and IgA) specific to B. mallei type 6 secretory proteins such as Hcp1, TssA and TssB. The infected equids also elicited robust cellular responses characterized by significantly elevated levels of IFN-γ, TNF-α, IL-12, IL-17 and IL-6 in PBMCs. In addition, stimulation of equine PBMCs by Hcp1 resulted in the further elevation of these cytokines. Thus, the present study indicated that antibody response and T helper cell (Th) type 1-associated cytokines were the salient features of chronic B. mallei infection in horses. The immune responses also suggest further evaluation of these proteins as potential vaccine candidates.

Molecular Typing of Burkholderia mallei Isolates from Equids with Glanders, India.

We collected 10 Burkholderia mallei isolates from equids in 9 districts in India during glanders outbreaks in 2013-2016. Multilocus variable-number tandem-repeat analysis showed 7 outbreak area-related genotypes. The study highlights the utility of this analysis for epidemiologically tracing of specific B. mallei isolates during outbreaks.

16S rDNA and ITS Sequence Diversity of Burkholderia mallei Isolated from Glanders-Affected Horses and Mules in India (2013-2019).

Glanders is a highly contagious and fatal infection of equids caused by the bacteria known as Burkholderia mallei. It is one of the notifiable equine diseases and is still present in Asia, South America and Africa. In India, glanders re-emerged in 2006, and thereafter, increasing numbers of cases were reported in different regions of the country. Between 2013 and 2019, 39 B. mallei were isolated from glanders-affected horses (n = 30) and mules (n = 9) from seven states of India such as Uttar Pradesh, Haryana, Delhi, Himachal Pradesh, Gujarat, Maharashtra and Tamil Nadu. In this study, the phylogenetic relationships of these isolates were assessed by sequence analysis of 16S rDNA gene and ITS region. Purified PCR-amplified products of 16S rDNA gene and ITS region were sequenced, aligned and phylogenetic trees were constructed using MEGA 11 software. Additionally, B. mallei 16S rDNA (n = 36) and ITS (n = 18) sequences available in the GenBank were also included for analysis to determine the diversity of older B. mallei isolates with recent Indian isolates. Both the phylogeny showed that the majority of the recent isolates from India are closely related to each other, but are genetically diverse from older isolates that originated from India. Nucleotide substitutions were also observed in a single and double position in 12 recent and two old Indian isolates. The study also indicates that similar B. mallei strains were responsible for glanders outbreaks in different states (Uttar Pradesh- Himachal Pradesh and Uttar Pradesh- Haryana) and this is due to the migration of infected animals from one state to another state. This study implies that 16S rDNA and ITS region may be used for molecular characterization of B. mallei associated with glanders in resource-limited settings.

Improvement of recombinant-truncated Burkholderia motility protein A (BimA)-based indirect ELISA for equine glanders.

Glanders is a contagious and highly fatal disease of equines with zoonotic potential. It is caused by a Gram-negative, nonmotile bacterium Burkholderia mallei. Complement fixation test (CFT) is one of the most commonly used tests for diagnosis of glanders; however, it has some limitations. A recombinant-truncated Burkholderia intracellular motility A (BimA) protein-based indirect enzyme-linked immunosorbent assay (iELISA) was previously reported by us for glanders diagnosis, which has been re-optimized in this study using a panel of glanders positive (n = 75) and glanders negative (n = 227) serum samples. The improved iELISA exhibited 96% sensitivity and 90.75% specificity. The assay had 98.56% negative predictive value. In the improved iELISA, background for negative samples was reduced and a rational assay cut-off based on ROC curves was introduced. Intra laboratory repeatability of the iELISA was tested by 3 different operators with 100% correlation. The BimA-coated ELISA plates could be used without significant decrease in diagnostic efficacy even after their storage at room temperature or 37°C for 90 days. Overall, the improved iELISA is a sensitive, specific, reproducible, and easy-to-use assay that has potential in serodiagnosis of glanders, more suitably to demonstrate freedom from B. mallei infection in a population.

Use of heavy water (D2O) in developing thermostable recombinant p26 protein based enzyme-linked immunosorbent assay for serodiagnosis of equine infectious anemia virus infection.

Thermostabilizing effect of heavy water (D2O) or deuterium oxide has been demonstrated previously on several enzymes and vaccines like oral poliovirus vaccine and influenza virus vaccine. In view of the above observations, effect of heavy water on in situ thermostabilization of recombinant p26 protein on enzyme-linked immunosorbent assay (ELISA) for serodiagnosis of equine infectious anemia virus (EIAV) infection was investigated in the present study. The carbonate-bicarbonate coating buffer was prepared in 60% and 80% D2O for coating the p26 protein in 96-well ELISA plate and thermal stability was examined at 4 °C, 37 °C, 42 °C, and 45 °C over a storage time from 2 weeks to 10 months. A set of positive serum (n = 12) consisting of strong, medium, and weak titer strength (4 samples in each category) and negative serum (n = 30) were assessed in ELISA during the study period. At each time point, ELISA results were compared with fresh plate to assess thermal protective effect of D2O. Gradual increase in the stabilizing effect of 80% D2O at elevated temperature (37 °C < 42 °C < 45 °C) was observed. The 80% D2O provides the thermal protection to rp26 protein in ELISA plate up to 2 months of incubation at 45 °C. The findings of the present study have the future implication of adopting cost effective strategies for generating more heat tolerable ELISA reagents with extended shelf life.

Optimization and validation of indirect ELISA using truncated TssB protein for the serodiagnosis of glanders amongst equines.

OBJECTIVE: To express truncated TssB protein of Burkholderia mallei and to evaluate its diagnostic efficacy for serological detection of glanders among equines. MATERIALS AND METHODS: In an attempt to develop recombinant protein based enzyme-linked immunosorbent assay (ELISA), N-terminal 200 amino acid sequences of B. mallei TssB protein-a type 6 secretory effector protein--were expressed in prokaryotic expression system. Diagnostic potential of recombinant TssB protein was evaluated in indirect ELISA using a panel of glanders positive (n = 49), negative (n = 30), and field serum samples (n = 1811). Cross-reactivity of the assay was assessed with equine disease control serum and human melioidosis positive serum. RESULTS: In comparison to CFT, diagnostic sensitivity and specificity of ELISA were 99.7% and 100%, respectively. CONCLUSIONS: The indirect ELISA method using the truncated TssB offered safer and more rapid and efficient means of serodiagnosis of glanders in equines. These data highlight the use of TssB as potential diagnostic antigen for serological diagnosis of glanders.

Knowledge, awareness and perception about equine glanders among veterinarians and medical professionals in India.

Glanders is a highly infectious and notifiable disease of equines that occurs due to Burkholderia mallei. In India, glanders re-emerged in 2006 and thereafter regular outbreaks have been reported in various states (n = 14). Frequent and prolonged contact with equids with glanders may transmit B. mallei infection to humans. This study was designed to learn more about the Knowledge, Awareness and Perception (KAP) of veterinarians, para veterinarians, and physicians about equine glanders, which will help in enhancing the nation-wide glanders eradication programme. A total of 165 respondent's from 11 Indian states and one union territory were surveyed. Most of the respondents (n = 160) were from equine glanders affected or endemic states. Knowledge gap analysis revealed that 40.3 and 22% of the participants were not aware of government regulations and the transmission of glanders, respectively. These are major concerns given the wide spread occurrence of disease in the country. Awareness test on glanders revealed that 65(39.4%) participants would collect biological samples for laboratory confirmation, 67(40.6%) would inform the concerned authorities and 106 (64.2%) replied that they would eliminate the glanders infected equines. Analysis of perception towards equine glanders showed that majority of the participants (n = 113, 68.4%) observed that equine keepers were reluctant to disclose the clinical symptoms of B. mallei infection. Furthermore, non-co-operation and unwillingness by superiors (33.9%), financial (31%), administrative (28.4%), and technical limitations (27.8%) were major constraints under the perception analysis. This study reveals that veterinarians need to be educated on governmental policies and guidelines on equine glanders with regular training and awareness programs. Intersectoral co-ordination to investigate human glanders is also needed.

Complete genome sequence analysis of Japanese encephalitis virus isolated from a horse in India.

The complete genome of the Japanese encephalitis virus (JEV) strain JEV/eq/India/H225/2009(H225), isolated from an infected horse in India, was sequenced and compared to previously published JEV genomes. H225 genome was 10,977-nucleotides long, comprising a single ORF of 10,299-nucleotides, a 5'-UTR of 95 nucleotides and a 3'-UTR of 582 nucleotides. The H225 genome showed high levels of sequence identity with 47 fully sequenced JEV genomes, ranging from 99.3 % to 75.5 % for nucleotides and 99.2 % to 91.5 % for amino acid sequences. Phylogenetic analysis of the full-length sequence indicated that the H225 strain belongs to genotype III and is closely related to the Indian JEV strain Vellore P20778. A comparison of amino acids associated with neurovirulence in the E proteins and non-structural proteins of known virulent and attenuated JEV strains suggested H225 to be a highly virulent strain. This is the first report of whole-genome sequencing of a genotype III JEV genome isolated from equines.

Immunotherapeutic potential of CpG oligodeoxynucleotides in veterinary species.

Innate immunity plays a critical role in host defense against infectious diseases by discriminating between self and infectious non-self. The recognition of infectious non-self involves germ-line encoded pattern recognition receptors (PRRs) that recognize pathogen-associated molecular patterns (PAMPs). The PAMPs are the components of pathogenic microbes which include not only the cell wall constituents but also the unmethylated 2'-deoxy-ribo-cytosine-phosphate-guanosine (CpG) motifs. These CpG motifs present within bacterial and viral DNA are recognized by toll-like receptor 9 (TLR9), and signaling by this receptor triggers a proinflammatory cytokine response which, in turn, influences both innate and adaptive immune responses. The activation of TLR9 with synthetic CpG oligodeoxynucleotides (ODNs) induces powerful Th1-like immune responses. It has been shown to provide protection against infectious diseases, allergy and cancer in laboratory animal models and some domestic animal species. With better understanding of the basic biology and immune mechanisms, it would be possible to exploit the potential of CpG motifs for animal welfare. The research developments in the area of CpG and TLR9 and the potential applications in animal health have been reviewed in this article.

Multisectoral prioritization of zoonotic diseases in Haryana (India) using one health approach.

Zoonotic diseases have huge livestock and public health burden worldwide, including India. Prioritizing zoonotic diseases is one of the important tasks under 'One Health' as it facilitates effective policy making, proper allocation of resources and promotion of multisectoral collaboration. Although some efforts have been made to prioritizing zoonotic diseases at national level in India, it is important to identify priority diseases in regional settings due to wide variation in climate and demography of different states. Therefore, the present study aims to prioritize zoonotic diseases for the state of Haryana (India). One Health Zoonotic Disease Prioritization (OHZDP) tool was used in this study to prioritize zoonotic diseases. Based on literature review of the past 23 years (2000-2022) on prevalence, morbidity, and mortality of zoonotic diseases, twenty-three high-scoring zoonotic diseases in Haryana and neighboring states of India were initially shortlisted for prioritization. A three-day participatory workshop was conducted involving 17 experts representing the Health, Animal Husbandry and Wildlife departments of Haryana. The Analytical Hierarchy Process (AHP) was used to rank the criteria, which were used to score the selected diseases using the decision tree analysis. The participants selected the following 7 criteria along with their relative weights to score the diseases: (1) Severity of disease in humans, (2) Severity of disease in animals, (3) Presence of disease in the region, (4) Transmission and outbreak potential, (5) Socio-economic impact, (6) Availability of interventions, and (7) Existing inter-sectoral collaboration for surveillance and reporting. The top scoring eight diseases selected as priority zoonotic diseases for Haryana were rabies, Japanese encephalitis, bovine tuberculosis, leptospirosis, avian influenza (H5N1), brucellosis, glanders and Influenza A (H1N1). Sensitivity analysis did not reveal any significant variation in prioritization results by varying criteria weights. This is the first systemic attempt to prioritize zoonotic diseases in the state and this will help in formulating effective monitoring, prevention, and control strategies for zoonotic diseases in the regional settings.

Diagnosis of rabies using reverse-transcription polymerase chain reaction on post-mortem skin tissue specimens of the nasolabial plate in a rabies suspected cow: a case study.

In India, rabies in cattle is under-reported. Religious sentiments hamper its diagnosis, discouraging post-mortem examination, particularly opening the cranium. Specimens of peripheral tissue innervated by the cranial nerves could potentially be used as alternative diagnostic specimens to the brain. Herein, we present a case study of a novel approach for diagnosing rabies in a cow suspected of having rabies, using skin tissue specimens of the nasolabial plate obtained post-mortem. Brain and nasolabial tissue specimens tested positive for rabies using conventional reverse-transcription polymerase chain reaction. This approach has been previously shown to have a high diagnostic sensitivity in animals. We encourage further studies with more nasolabial plate skin specimens for both post- and antemortem diagnosis of rabies in cattle.

Sequence-based detection and typing procedures for Burkholderia mallei: Assessment and prospects.

Although glanders has been eradicated in most of the developed world, the disease still persists in various countries such as Brazil, India, Pakistan, Bangladesh, Nepal, Iran, Bahrain, UAE and Turkey. It is one of the notifiable diseases listed by the World Organization for Animal Health. Occurrence of glanders imposes restriction on equestrian events and restricts equine movement, thus causing economic losses to equine industry. The genetic diversity and global distribution of the causing agent, Burkholderia (B.) mallei, have not been assessed in detail and are complicated by the high clonality of this organism. Among the identification and typing methods, PCR-based methods for distinguishing B. mallei from its close relative B. pseudomallei as well as genotyping using tandem repeat regions (MLVA) are established. The advent and continuous advancement of the sequencing techniques and the reconstruction of closed genomes enable the development of genome guided epidemiological tools. For achieving a higher genomic resolution, genotyping methods based on whole genome sequencing data can be employed, like genome-wide single nucleotide polymorphisms. One of the limitations in obtaining complete genomic sequences for further molecular characterization of B. mallei is its high GC content. In this review, we aim to provide an overview of the widely used detection and typing methods for B. mallei and illustrate gaps that still require development. The genomic features of Burkholderia, their high homology and clonality will be first described from a comparative genomics perspective. Then, the commonly used molecular detection (PCR systems) and typing systems (e.g., multilocus sequence typing, variable number of tandem repeat analysis) will be presented and put in perspective with recently developed genomic methods. Also, the increasing availability of B. mallei genomic sequences and evolution of the sequencing methods offers exciting prospects for further refinement of B. mallei typing, that could overcome the difficulties presently encountered with this particular bacterium.

Validation of a Commercial Glanders ELISA as an Alternative to the CFT in International Trade of Equidae.

Glanders, caused by Burkholderia (B.) mallei is a notifiable zoonotic disease in equidae. For international trade and movement of equids, certificates of negative serological test results for antibodies against B. mallei are required. To date, the complement fixation test (CFT) is the mandatory test to issue these health certificates. The CFT is difficult to standardize and, due to its poor specificity, often leads to false-positive reactions resulting in trade restrictions with considerable financial consequences. In the present study, the new ID Screen Glanders Double Antigen Multispecies ELISA (GLANDA- ELISA) (IDvet, Grabels, France) was evaluated using 400 negative and 370 glanders positive field samples of equidae. The GLANDA-ELISA was significantly more specific (99.8%) than the CFT (97.0%). Considering the comparable sensitivities of CFT (96.5%) and ELISA (98.1%), this new GLANDA-ELISA test appears a suitable confirmatory test and a realistic alternative for serological testing of horses for trade or movement.

Serological Survey of Humans Exposed to Burkholderia mallei-Infected Equids: A Public Health Approach.

Glanders is a fatal bacterial infection of equids caused by Burkholderia mallei. The infection can be transmitted to humans through prolonged direct contact with glanderous equids. Recently, reemergence of equine glanders has been reported in many countries. To investigate zoonotic transmission of B mallei infection, sera were collected from 538 humans including equine handlers and veterinary professionals exposed to glanderous equids. Samples were tested by ELISA (enzyme-linked immunosorbent assay) and complement fixation test and found negative for B mallei-specific antibodies. Even though there was no incidence of human glanders during this survey period, occupational exposure will continue to remain a serious concern and a key risk factor. Therefore, we emphasize the need for intersectoral collaboration and coordination among veterinary, human, and public health authorities for continuous surveillance and monitoring of human glanders under one health concept.

Serological surveillance and clinical investigation of glanders among indigenous equines in India from 2015 to 2018.

Equine glanders is an infectious and notifiable bacterial disease caused by Burkholderia mallei. The disease has been reported in South American, African and Asian countries including India. Here, we present the outcome of glanders serosurveillance carried out between January 2015 and December 2018 to know the status of equine glanders among different states in India. A total of 102,071 equid sera from 299 districts of twenty-one states and one union territory were tested for glanders. Samples were screened with Hcp1 indirect ELISA followed by confirmatory diagnosis by CFT. During this four-year surveillance, a total of 932 glanders-positive cases were detected from 120 districts of 12 states. The study also revealed increasing trend of glanders from 2016 onwards with maximum occurrence in northern India. Overall seroprevalence ranged between 0.62% (95% CI, 0.52-0.72) and 1.145% (95% CI, 1.03-1.25). Seasonal shifting from winter to summer (March to June) coincided with highest number glanders incidence with corresponding seroprevalences of 1.2% (95% CI, 1.09-1.30). The present surveillance unveils territorial ingression of glanders to six states like Jammu & Kashmir, Gujarat, Rajasthan, Madhya Pradesh, Delhi and Tamil Nadu. In addition, re-emerging cases have been reported in Maharashtra, Haryana and Punjab after a gap of 10 years. Lack of awareness, little veterinary care and unrestricted movement of equids across state borders might have led to the introduction and establishment of the infection to these states. We believe that information from this study will provide a baseline data on glanders for devising surveillance and control strategies in India. Being a zoonotic disease, the persistence of glanders poses a potential threat to occupationally exposed humans especially equine handlers and veterinarians. Therefore, targeted surveillance of human population from each glanders outbreak is also recommended.

Sequence and functional variability of Toll-like receptor 9 gene in equines.

Significant structural differences in the extracellular domain of toll-like receptor 9 (TLR9) account for species-specific recognition of its ligand CpG-ODN sequences. TLR9 is extensively studied in human, mice and some domestic animals. The recognition ability appears to be utilized differently by various species and breeds, but so far no comprehensive study exists about the equine TLR9 gene. We characterized TLR9 sequences of Marwari and Zanskari breeds of horses and Poitu donkey. We sequenced and identified the protein coding regions of equine TLR9 and compared with other animals and human beings. Furthermore, we also analyzed the amino acid substitutions and their likely implications on functions. The analysis revealed 14% evolutionary divergence between equine and human TLR9, while it was 1% between the Equus caballus and Equus asinus and less than 1% within Equus caballus. In phylogenetic analysis of predicted amino acids, the indigenous equines grouped with thoroughbred Equus caballus, while human, cattle, dog, sheep, mice, and buffalo formed separate clades. Furthermore, we also analyzed the amino acid substitutions and their likely implications on functions by sorting intolerant from tolerant (SIFT) analysis and predicted two substitutions of amino acids (D80N and S822P) in Marwari horses in leucine rich repeat 1 (LRR1) without any functional effects. The substitutions (V214A and Y579C) in LRR 3 and LRR11 in Zanskari horses were predicted to have functional consequences. Out of overall 8 substitutions, three substitutions (I420V, S970R and R1001C) were found in Equus asinus in LRR7, LRR 13, and toll interleukin receptor (TIR) domains, while the substitution G649S is observed in Poitu donkey only. We report for the first time that despite the conserved residues, the striking effect of substitutions, found within the TLR9 genes of different equine breeds/species may have possible implications.

Recombinant horse interleukin-4 and interleukin-10 induced a mixed inflammatory cytokine response in horse peripheral blood mononuclear cells.

BACKGROUND AND AIM: Interleukin (IL)-4 and IL-10 activate plethora of immune cells and induce the humoral immune response. However, recombinant version of horse IL-4 and IL-10 has not been investigated to understand their immunomodulating activities. This study aimed to produce recombinant horse mature IL-4 and IL-10 in Escherichia coli. Immune-modulating activities of recombinant horse IL-4 and IL-10 were investigated in peripheral blood mononuclear cells (PBMCs). MATERIALS AND METHODS: Equine PBMCs were stimulated with recombinant IL-4 and IL-10. A proliferation of PBMCs was measured by XTT assay and cytokines induction was measured by enzyme-linked immunosorbent assay and real-time polymerase chain reaction. RESULTS: Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis displayed a molecular weight of 15 kDa for IL-4 and 19 kDa for IL-10. Recombinant IL-4 and IL-10 significantly induced cell proliferation at 250 ng/ml. The results demonstrated that IL-4 enhanced expression of interferon-gamma (IFN-γ), IL-6, tumor necrosis factor-alpha (TNF-α), and IL-10, while recombinant horse IL-10 induced expression of IL-6, IFN-γ, and TNF-α. CONCLUSION: The present study demonstrated that biologically active horse IL-4 and IL-10 could be produced in E. coli.

Evaluation of the comparative accuracy of the complement fixation test, Western blot and five enzyme-linked immunosorbent assays for serodiagnosis of glanders.

Glanders is a zoonotic contagious disease of equids caused by Burkholderia (B.) mallei. Serodiagnosis of the disease is challenging because of false-positive and false-negative test results. The accuracy of the complement fixation test (CFT) which is prescribed for international trade by the World Organisation for Animal Health (OIE), five ELISAs and a Western blot (WB) were compared for serodiagnosis of glanders using sera from 3,000 glanders-free and 254 glanderous equids. Four ELISA tests are based on recombinant antigens (TssA, TssB, BimA and Hcp1), the IDVet ELISA is based on a semi-purified fraction of B. mallei and WB makes use of a purified LPS-containing B. mallei-antigen. Sensitivity and specificity of tests were estimated using cut-off values recommended by the test developers. The WB and all ELISAs, except BimA, were significantly more specific than the CFT. ELISAs based on TssA, TssB, and BimA antigens had significantly lower sensitivity compared to CFT while the sensitivities of the Hcp1-ELISA, the IDVet-ELISA and the WB did not differ significantly from that of the CFT. Given their comparable sensitivities and specificities, the CFT (98.0%, 96.4%), the WB (96.8%, 99.4%), the Hcp1-ELISA (95.3%, 99.6%) and the IDVet-ELISA (92.5%, 99.5%) should be further developed to meet OIE requirements.

Draft Genome Sequences of Two Clinical Isolates of Burkholderia mallei Obtained from Nasal Swabs of Glanderous Equines in India.

Burkholderia mallei is a Gram-negative coccobacillus which causes glanders-a fatal disease of equines that may occasionally be transmitted to humans. Several cases of outbreaks have been reported from India since 2006. This paper presents draft genome sequences of two B. mallei strains isolated from equines affected by glanders in India.