Development of Multispecies Recombinant Nucleoprotein-Based Indirect ELISA for High-Throughput Screening of Crimean-Congo Hemorrhagic Fever Virus-Specific Antibodies

Seroprevalence of Crimean-Congo haemorrhagic fever in Indian cattle and buffaloes

BACKGROUND & OBJECTIVES

Crimean-Congo hemorrhagic fever (CCHF) is an emerging tick-borne viral zoonotic disease of public health importance. Cattle and buffaloes although not showing any clinical symptoms, can be infected by the CCHF virus and act as sources of infection to human beings. The prevalence of CCHF in cattle and buffaloes is important from One health perspective for control of CCHF in humans.

METHODS

A cross-sectional study was undertaken to ascertain the prevalence of CCHFV in cattle and buffaloes of India.

MATERIALS AND METHODS

A total of 804 serum samples from four states of India (Gujarat and Rajasthan: human outbreaks reported; Punjab and Haryana: no outbreak reported) were screened by ELISA test detecting nucleoprotein antibodies of CCHFV.

RESULTS

The overall true prevalence was 8.63% (95% CI: 6.76% - 10.9%). The highest prevalence was recorded in Rajasthan (13.24%) followed by Gujarat (8.68%), Haryana (6.84%), and Punjab (6.51%). Prevalence of CCHF was higher in cattle (9.92%) than buffaloes (5.84%); in females (10.87%) than males (4.99%); in adults (10.18%) than young ones (5.66%). Interestingly, higher seropositivity was recorded in indigenous cattle (12.04%) than in exotic and cross-breed cattle (1.69%) which was statistically significant (p=0.001).

INTERPRETATION & CONCLUSION

These findings revealed CCHF virus is circulating unnoticed and the prevalence has increased over time which is of public health concern.

Mutational analysis of catalytic site domain of CCHFV L RNA segment

INTRODUCTION

Crimean-Congo haemorrhagic fever virus (CCHFV) has tripartite RNA genome and is endemic in various countries of Asia, Africa and Europe.

METHOD

The present study is focused on mutation profiling of CCHFV L segment and phylogenetic clustering of protein dataset into six CCHFV genotypes.

RESULTS

Phylogenetic tree rooted with NCBI reference sequence (YP_325663.1) indicated less divergence from genotype III and the sequences belonging to same genotypes have shown less divergence among each other. Mutation frequency at 729 mutated positions was calculated and 563, 49, 33, 46 and 38 amino acid positions were found to be mutated at mutation frequency intervals of 0-0.2, 0.21-0.4, 0.41-0.6, 0.61-0.8 and 0.81-1.0 respectively. Thirty-eight highly frequent mutations (0.81-1.0 interval) were found in all genotypes and mapping in L segment (encoded for RdRp) revealed four mutations (V2074I, I2134T/A, V2148A and Q2695H/R) in catalytic site domain and no mutation in OTU domain. Molecular dynamic simulation and in silico analysis showed that catalytic site domain displayed large deviation and fluctuation upon introduction of these point mutations.

CONCLUSION

Overall study provides strong evidence that OTU domain is highly conserved and less prone to mutation whereas point mutations recorded in catalytic domain have affected the stability of protein and were found to be persistent in the large population.

Multiplex Assay for Simultaneous Detection of Antibodies against Crimean-Congo Hemorrhagic Fever Virus Nucleocapsid Protein and Glycoproteins in Ruminants

Crimean-Congo hemorrhagic fever virus (CCHFV) is a widespread tick-borne zoonotic virus that causes Crimean-Congo hemorrhagic fever (CCHF). CCHF is asymptomatic in infected animals but can develop into severe illness in humans, with high case-fatality rates. Due to complex environmental and socio-economic factors, the distribution of CCHFV vectors is changing, leading to disease occurrence in previously unaffected countries. Neither an effective treatment nor a vaccine has been developed against CCHFV; thus, surveillance programs are essential to limit and control the spread of the virus. Furthermore, the WHO highlighted the need of assays that can cover a range of CCHFV antigenic targets, DIVA (differentiating infected from vaccinated animals) assays, or assays for future vaccine evaluation. Here, we developed a multiplex assay, based on a suspension microarray, able to detect specific antibodies in ruminants to three recombinantly produced CCHFV proteins: the nucleocapsid (N) protein and two glycoproteins, GN ectodomain (GNe), and GP38. This triplex assay was used to assess the antibody response in naturally infected animals. Out of the 29 positive field sera to the N protein, 40% showed antibodies against GNe or GP38, with 11 out of these 12 samples being positive to both glycoproteins. To determine the diagnostic specificity of the test, a total of 147 sera from Spanish farms free of CCHFV were included in the study. This multiplex assay could be useful to detect antibodies to different proteins of CCHFV as vaccine target candidates and to study the immune response to CCHFV in infected animals and for surveillance programs to prevent the further spread of the virus. IMPORTANCE Crimean-Congo hemorrhagic fever virus (CCHFV) causes Crimean-Congo hemorrhagic fever, which is one of the most important tick-borne viral diseases of humans and has recently been found in previously unaffected countries such as Spain. The disease is asymptomatic in infected animals but can develop into severe illness in humans. As neither an effective treatment nor a vaccine has been developed against CCHFV, surveillance programs are essential to limit and control the spread of the virus. In this study, a multiplex assay detecting antibodies against different CCHFV antigens in a single sample and independent of the ruminant species has been developed. This assay could be very useful in surveillance studies, to control the spread of CCHFV and prevent future outbreaks, and to better understand the immune response induced by CCHFV.

Development of anti-Crimean-Congo hemorrhagic fever virus Gc and NP-specific ELISA for detection of antibodies in domestic animal sera

Crimean-Congo hemorrhagic fever (CCHF) is a priority emerging disease. CCHF, caused by the CCHF virus (CCHFV), can lead to hemorrhagic fever in humans with severe cases often having fatal outcomes. CCHFV is maintained within a tick-vertebrate-tick cycle, which includes domestic animals. Domestic animals infected with CCHFV do not show clinical signs of the disease and the presence of antibodies in the serum can provide evidence of their exposure to the virus. Current serological tests are specific to either one CCHFV antigen or the whole virus antigen. Here, we present the development of two in-house ELISAs for the detection of serum IgG that is specific for two different CCHFV antigens: glycoprotein Gc (CCHFV Gc) and nucleoprotein (CCHFV NP). We demonstrate that these two assays were able to detect anti-CCHFV Gc-specific and anti-CCHFV NP-specific IgG in sheep from endemic CCHFV areas with high specificity, providing new insight into the heterogeneity of the immune response induced by natural infection with CCHFV in domestic animals.

Mapping of Antibody Epitopes on the Crimean-Congo Hemorrhagic Fever Virus Nucleoprotein

Crimean-Congo hemorrhagic fever virus (CCHFV), a nairovirus, is a tick-borne zoonotic virus that causes hemorrhagic fever in humans. The CCHFV nucleoprotein (NP) is the antigen most used for serological screening of CCHFV infection in animals and humans. To gain insights into antibody epitopes on the NP molecule, we produced recombinant chimeric NPs between CCHFV and Nairobi sheep disease virus (NSDV), which is another nairovirus, and tested rabbit and mouse antisera/immune ascites, anti-NP monoclonal antibodies, and CCHFV-infected animal/human sera for their reactivities to the NP antigens. We found that the amino acids at positions 161–320 might include dominant epitopes recognized by anti-CCHFV IgG antibodies, whereas cross-reactivity between anti-CCHFV and anti-NSDV antibodies was limited. Their binding capacities were further tested using a series of synthetic peptides whose sequences were derived from CCHFV NP. IgG antibodies in CCHFV-infected monkeys and patients were reactive to some of the synthetic peptide antigens (e.g., amino acid residues at positions 131–150 and 211–230). Only a few peptides were recognized by IgG antibodies in the anti-NSDV serum. These results provide useful information to improve NP-based antibody detection assays as well as antigen detection tests relying on anti-NP monoclonal antibodies.

Immune responses in multiple hosts to Nucleocapsid Protein (NP) of Crimean-Congo Hemorrhagic Fever Virus (CCHFV)

In 2019, the World Health Organization declared 3 billion to be at risk of developing Crimean Congo Hemorrhagic Fever (CCHF). The causative agent of this deadly infection is CCHFV. The data related to the biology and immunology of CCHFV are rather scarce. Due to its indispensable roles in the viral life cycle, NP becomes a logical target for detailed viral immunology studies. In this study, humoral immunity to NP was investigated in CCHF survivors, as well as in immunized mice and rabbits. Abundant antibody response against NP was demonstrated both during natural infection in humans and following experimental immunizations in mice and rabbits. Also, cellular immune responses to recombinant NP (rNP) was detected in multispecies. This study represents the most comprehensive investigation on NP as an inducer of both humoral and cellular immunity in multiple hosts and proves that rNP is an excellent candidate warranting further immunological studies specifically on vaccine investigations.

Crimean Congo Hemorrhagic Fever Virus (CCHFV) is the most lethal human pathogen of medical importance after the dengue virus among arboviruses. The increasing geographic spread of Hyalomma ticks, which are responsible for viral transmission widespread, threatens billions of people. WHO currently declares the field of research on CCHFV as the second most urgently needed areas of investigations on emerging pathogens. About 10 to 40% of those infected with the virus lose their life due to the rapidly developing severe clinical manifestations. Pandemic potential and the lack of any approved treatment or vaccine make raise the studies on CCHFV as critical. The studies on CCHFV are challenging due to the necessities of BSL-4 facilities and the immunological characterization of individual structural proteins will lay the groundwork for the steps to be taken to treat and prevent this emerging disease. As is known from other RNA viruses, nucleoprotein (NP) has crucial roles in the viral life cycle, both in viral replication and transcription and in the formation of the virion structure. So far, detailed and comprehensive immunological characterizations on NP in multiple are not undertaken. Our study was set out to embark such detailed investigation. The strong humoral and cellular immune response to NP demonstrated by this study indicates that NP might be an excellent candidate for future scrutinies on vaccines and diagnostic reagents.

Development of double antibody sandwich ELISA as potential diagnostic tool for rapid detection of Crimean-Congo hemorrhagic fever virus

Crimean-Congo hemorrhagic fever (CCHF) virus, a highly pathogenic viral agent is responsible for severe fatal hemorrhagic infections in many parts of the world. The early diagnosis of CCHF infection is important for successful clinical management and epidemiological control. The nucleoprotein (NP) of CCHFV being highly conserved and immunogenic is used as early diagnostic marker. In this study, we report a rapid and sensitive double antibody based antigen capture ELISA to detect Crimean-Congo hemorrhagic fever virus (CCHFV). Highly specific polyclonal and monoclonal antibody against NP has been generated and used as capture and detector antibody respectively. The assay was able to detect viral nucleoprotein in different matrices including human serum, ticks and culture supernatant. The detection limit of the developed sandwich ELISA assay was 25 ng of purified antigen. Comparison with a real time RT-PCR revealed its detection limit to be 1000 genome equivalents of CCHFV. Further the assay was comparatively evaluated with a commercial kit employing gamma irradiated CCHFV, revealing a sensitivity and specificity of 100%. This newly developed sandwich ELISA (sELISA) with high sensitivity and specificity could be used as an efficient method for the detection of CCHF virus in humans, ticks and culture supernatant. The assay will be useful as alternate tool for diagnosis of acute infection and is amenable for screening of large scale samples in resource limited settings.

Development of a novel recombinant ELISA for the detection of Crimean-Congo hemorrhagic fever virus IgG antibodies

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne viral infection caused by Crimean-Congo hemorrhagic fever virus (CCHFV). Serological screening of CCHF is important and current ELISA use antigens prepared from virus which is expensive due to requirement of high bio-containment facilities. In this study, we aimed to develop a new recombinant ELISA. For this purpose, CCHFV genome were expressed as 13 proteins in E. coli and among them abundantly purified recombinant Nucleocapsid protein (rNP) and Mucin-like variable domain (rMLD) were used as antigen in ELISA (Rec-ELISA). Rec-ELISA using rNP, rMLD and a combination of both (rNP/rMLD) were probed with acute (n = 64; collected between days 1 and 7 after onset of symptoms), convalescent (n = 35; collected 8 days after onset of symptoms), consecutive sera (n = 25) of confirmed CCHF cases and control sera (n = 43). The sensitivity and specificity of Rec-ELISA using rNP/rMLD were 73% and 98% in acute cases and 97% and 98% in convalescent cases. The median interquartile absorbance value to discriminate the acute and convalescent phases of CCHF was significantly higher with ELISA using rNP/rMLD (P < 0.0001) compared to rNP (P > 0.05) and rMLD (P = 0.001). These results indicate that the Rec-ELISA using rNP/rMLD may be very useful to diagnose convalescent CCHF cases especially in field studies.

A Review on Emerging Infectious Diseases Prioritized Under the 2018 WHO Research and Development Blueprint: Lessons from the Indian Context

Objective: This review describes the current scenario of a priority group of emerging infectious diseases (EIDs) listed by World Health Organization (WHO), and their main determinants and drivers for the emergence/spread of the diseases. The gaps and strategies developed by India to meet the WHO guidelines on the effective control of epidemic-prone diseases and outbreaks are also presented in the review. Methods: Epidemiologic information of EIDs, namely Crimean-Congo hemorrhagic fever (CCHF), Ebola and Marburg viruses (EboV and MarV), Zika virus (ZIKAV), Rift Valley fever (RVF), Middle East respiratory syndrome, severe acute respiratory syndrome (SARS), Nipah and Hendra virus (NiV and HeV), and Lassa fever virus (LASV), was drawn from international and national electronic databases to assess the situation. A brief view on the novel coronavirus disease 2019 (COVID-19) in India is also included. Results: There are no reports for human infection of EboV, MarV, RVF, and LASV in India. CCHF, SARS, ZIKAV, and NiV have been involved in outbreaks in eight states of India, while COVID-19 is currently reported from majority of states. India has deeply strengthened its surveillance and response system of outbreaks and epidemic-prone diseases. Conclusions: Despite its enormous improvements made in the anticipation of such threats, still more efforts are needed in sensitization of populations as well as hospital management in the context to EIDs, as addressed in the review. Furthermore, there is still a need for more research and development activities to efficiently control EIDs.

Human virus detection with graphene-based materials

Our recent experience of the COVID-19 pandemic has highlighted the importance of easy-to-use, quick, cheap, sensitive and selective detection of virus pathogens for the efficient monitoring and treatment of virus diseases. Early detection of viruses provides essential information about possible efficient and targeted treatments, prolongs the therapeutic window and hence reduces morbidity. Graphene is a lightweight, chemically stable and conductive material that can be successfully utilized for the detection of various virus strains. The sensitivity and selectivity of graphene can be enhanced by its functionalization or combination with other materials. Introducing suitable functional groups and/or counterparts in the hybrid structure enables tuning of the optical and electrical properties, which is particularly attractive for rapid and easy-to-use virus detection. In this review, we cover all the different types of graphene-based sensors available for virus detection, including, e.g., photoluminescence and colorimetric sensors, and surface plasmon resonance biosensors. Various strategies of electrochemical detection of viruses based on, e.g., DNA hybridization or antigen-antibody interactions, are also discussed. We summarize the current state-of-the-art applications of graphene-based systems for sensing a variety of viruses, e.g., SARS-CoV-2, influenza, dengue fever, hepatitis C virus, HIV, rotavirus and Zika virus. General principles, mechanisms of action, advantages and drawbacks are presented to provide useful information for the further development and construction of advanced virus biosensors. We highlight that the unique and tunable physicochemical properties of graphene-based nanomaterials make them ideal candidates for engineering and miniaturization of biosensors.

Characterization and applications of a Crimean-Congo hemorrhagic fever virus nucleoprotein-specific Affimer: Inhibitory effects in viral replication and development of colorimetric diagnostic tests

Crimean-Congo hemorrhagic fever orthonairovirus (CCHFV) is one of the most widespread medically important arboviruses, causing human infections that result in mortality rates of up to 60%. We describe the selection of a high-affinity small protein (Affimer-NP) that binds specifically to the nucleoprotein (NP) of CCHFV. We demonstrate the interference of Affimer-NP in the RNA-binding function of CCHFV NP using fluorescence anisotropy, and its inhibitory effects on CCHFV gene expression in mammalian cells using a mini-genome system. Solution of the crystallographic structure of the complex formed by these two molecules at 2.84 Å resolution revealed the structural basis for this interference, with the Affimer-NP binding site positioned at the critical NP oligomerization interface. Finally, we validate the in vitro application of Affimer-NP for the development of enzyme-linked immunosorbent and lateral flow assays, presenting the first published point-of-care format test able to detect recombinant CCHFV NP in spiked human and animal sera.

Identification of functional epitopes of structural proteins and in-silico designing of dual acting multiepitope anti-tick vaccine against emerging Crimean-Congo hemorrhagic fever virus

Recurrent outbreaks of Crimean-Congo hemorrhagic fever (CCHF) virus infection in different parts of world are a major global health concern. The CCHF viral infection is associated with severe hemorrhagic fevers and mortality up to 40%. More than 30 countries in Asia, Europe and Africa are affected with CCHF infection. Prevention of infection through vaccine becomes more important when no effective antiviral and associated therapies are available. Further ticks play a crucial role in maintenance and transmission of CCHFV. Therefore, the control of transmission by ticks is warranted for ultimate prevention of outbreak. The study employed a series of immunoinformatics approaches to design novel multiepitope vaccine targeting highly immunodominant epitopes of major structural proteins (Nucleoprotein and Glycoprotein complex) of CCHFV. Vaccine was designed by incorporating linear and conformational B cell, helper and cytotoxic T cell epitopes from these crucial immunogenic proteins adjoined with appropriate linkers and adjuvant. This vaccine construct was also complemented with a highly immunogenic and conserved protective tick salivary antigen named subolesin to impart dual activity as a unique transmission blocking vaccine. The B-cell peptides were also experimentally validated. The designed vaccine was further in silico validated for its physiochemical properties, allergenicity and immunogenicity etc. The proposed candidate vaccine construct has the potential to function both as a vaccine against CCHF virus as well as a universal anti-tick vaccine.