Marsupial and monotreme serum immunoglobulin binding by proteins A, G and L and anti-kangaroo antibody

Towards a pan marsupial sero-immunological tool in the demanding field of wildlife serology: Marsupial immunoglobulin-binding capability with protein A/G, protein L and anti-kangaroo antibody

Detection of infections in wildlife species is increasingly important to reduce the risk of spreading zoonotic and economically important parasites, understand disease epidemiology and promote the conservation of wildlife species. Serological tests are key in disease diagnosis and surveillance by detecting immunoglobulins against infectious agents. However, the need for species-specific reagents has limited the application of serological tests in wildlife species. This study evaluated the serum immunoglobulin-binding capability of polyclonal anti-kangaroo antibody and two non-species-specific reagents, including protein A/G and protein L, with the largest range of Australian marsupial species so far, including 32 species representing three major marsupial orders. Immunoglobulin-binding capability was assessed using immunoblotting, enzyme-linked immunosorbent assay and Western blot techniques. Variation in immunoglobulin-binding capability was observed between the three reagents and across the species tested, both across but also within taxonomic groups. Taxonomic distance was thus not always a good predictor of immunoglobulin-binding affinity, emphasizing the need to validate these reagents for each species separately. However, all three reagents bound with the serum immunoglobulins of most marsupial species tested. The findings of this study provide a valuable reference for species differences in affinity to protein A/G, protein L and anti-kangaroo antibody, assisting in the selection of appropriate reagents and the development of sero-immunological assays in Australian marsupials.

AFFINITY OF BRAZILIAN WILD MAMMAL IMMUNOGLOBULINS TO BACTERIAL PROTEINS A AND G

Staphylococcal A and streptococcal G proteins are widely used in immunoassays when specific immunological reagents are unavailable, such as for wild animals. The affinity of bacterial proteins A and G to the immunoglobulins of seven Brazilian mammals were tested, including black-tufted marmoset (Callithrix penicillata, n = 5), golden-bellied capuchin (Sapajus xanthosternos, n = 13), woolly mouse opossum (Micoureus demerarae, n = 6), long-nosed armadillo (Dasypus novemcinctus, n = 5), collared anteater (Tamandua tetradactyla, n = 5), ocelot (Leopardus pardalis, n = 6), and vampire bat (Desmodus rotundus, n = 5). Blood samples were collected from animals that were rescued in peri-urban rainforest fragments. Sera pools of each species were tested by ELISA to determine the intensity of each bacterial protein affinity to the immunoglobulins. When comparing the affinity to both proteins, immunoglobulins from D. rotundus, S. xanthosternos, and T. tetradactyla presented a higher affinity to protein G, whereas a higher affinity to protein A was found for immunoglobulins of C. penicillata and L. pardalis. The only species that presented a very low affinity to both bacterial proteins was M. demerarae. This study can be used as a reference for further studies on the development of sensitive and specific immunodiagnostic assays to be used for the monitoring of the health of these wild mammals.

Validation of an Indirect Immunofluorescence Assay and Commercial Q Fever Enzyme-Linked Immunosorbent Assay for Use in Macropods

Kangaroos are considered to be an important reservoir of Q fever in Australia, although there is limited knowledge on the true prevalence and distribution of coxiellosis in Australian macropod populations. Serological tests serve as useful surveillance tools, but formal test validation is needed to be able to estimate true seroprevalence rates, and few tests have been validated to screen wildlife species for Q fever. In this study, we modified and optimized a phase-specific indirect immunofluorescence assay (IFA) for the detection of IgG antibodies against Coxiella burnetii in macropod sera. The assay was validated against the commercially available ID Screen Q fever indirect multispecies enzyme-linked immunosorbent assay (ELISA) kit (IDVet, Grabels, France) to estimate the diagnostic sensitivity and specificity of each assay, using Bayesian latent class analysis. A direct comparison of the two tests was performed by testing 303 serum samples from 10 macropod populations from the east coast of Australia and New Zealand. The analysis indicated that the IFA had relatively high diagnostic sensitivity (97.6% [95% credible interval [CrI], 88.0 to 99.9]) and diagnostic specificity (98.5% [95% CrI, 94.4 to 99.9]). In comparison, the ELISA had relatively poor diagnostic sensitivity (42.1% [95% CrI, 33.7 to 50.8]) and similar diagnostic specificity (99.2% [95% CrI, 96.4 to 100]) using the cutoff values recommended by the manufacturer. The estimated true seroprevalence of C. burnetii exposure in the macropod populations included in this study ranged from 0% in New Zealand and Victoria, Australia, up to 94.2% in one population from New South Wales, Australia.

Descriptive Comparison of ELISAs for the Detection of Toxoplasma gondii Antibodies in Animals: A Systematic Review

Toxoplasma gondii is the zoonotic parasite responsible for toxoplasmosis in warm-blooded vertebrates. This systematic review compares and evaluates the available knowledge on enzyme-linked immunosorbent assays (ELISAs), their components, and performance in detecting T. gondii antibodies in animals. Four databases were searched for published scientific studies on T. gondii and ELISA, and 57 articles were included. Overall, indirect (95%) and in-house (67%) ELISAs were the most used types of test among the studies examined, but the 'ID Screen® Toxoplasmosis Indirect Multi-species' was common among commercially available tests. Varying diagnostic performance (sensitivity and specificity) and Kappa agreements were observed depending on the type of sample (serum, meat juice, milk), antigen (native, recombinant, chimeric) and antibody-binding reagents used. Combinations of recombinant and chimeric antigens resulted in better performance than native or single recombinant antigens. Protein A/G appeared to be useful in detecting IgG antibodies in a wide range of animal species due to its non-species-specific binding. One study reported cross-reactivity, with Hammondia hammondi and Eimeria spp. This is the first systematic review to descriptively compare ELISAs for the detection of T. gondii antibodies across different animal species.

Evaluation of the PEΔIII-LC3-KDEL3 Chimeric Protein of Entamoeba histolytica-Lectin as a Vaccine Candidate against Amebic Liver Abscess

Entamoeba histolytica is an intestinal parasite that causes dysentery and amebic liver abscess. E. histolytica has the capability to invade host tissue by union of virulence factor Gal/GalNAc lectin; this molecule induces an adherence-inhibitory antibody response as well as to protect against amebic liver abscess (ALA). The present work showed the effect of the immunization with PEΔIII-LC3-KDEL3 recombinant protein. In vitro, this candidate vaccine inhibited adherence of E. histolytica trophozoites to HepG2 cell monolayer, avoiding the cytolysis, and in a hamster model, we observed a vaccine-induced protection against the damage to tissue liver and the inhibition of uncontrolled inflammation. PEΔIII-LC3-KDEL3 reduced the expression of TNF-α, IL-1β, and NF-κB in all immunized groups at 4- and 7-day postinfection. The levels of IL-10, FOXP3, and IFN-γ were elevated at 7 days. The immunohistochemistry assay confirmed this result, revealing an elevated quantity of +IFN-γ cells in the liver tissue. ALA formation in hamsters immunized was minimal, and few trophozoites were identified. Hence, immunization with PEΔIII-LC3-KDEL3 herein prevented invasive amebiasis, avoided an acute proinflammatory response, and activated a protective response within a short time. Finally, this recombinant protein induced an increase of serum IgG.

Koala and Wombat Gammaherpesviruses Encode the First Known Viral NTPDase Homologs and Are Phylogenetically Divergent from All Known Gammaherpesviruses

There is a large taxonomic gap in our understanding of mammalian herpesvirus genetics and evolution corresponding to those herpesviruses that infect marsupials, which diverged from eutherian mammals approximately 150 million years ago (mya). We compare the genomes of two marsupial gammaherpesviruses, Phascolarctid gammaherpesvirus 1 (PhaHV1) and Vombatid gammaherpesvirus 1 (VoHV1), which infect koalas (Phascolarc tos cinereus) and wombats (Vombatus ursinus), respectively. The core viral genomes were approximately 117 kbp and 110 kbp in length, respectively, sharing 69% pairwise nucleotide sequence identity. Phylogenetic analyses showed that PhaHV1 and VoHV1 formed a separate branch, which may indicate a new gammaherpesvirus genus. The genomes contained 60 predicted open reading frames (ORFs) homologous to those in eutherian herpesviruses and 20 ORFs not yet found in any other herpesvirus. Seven of these ORFs were shared by the two viruses, indicating that they were probably acquired prespeciation, approximately 30 to 40 mya. One of these shared genes encodes a putative nucleoside triphosphate diphosphohydrolase (NTPDase). NTPDases are usually found in mammals and higher-order eukaryotes, with a very small number being found in bacteria. This is the first time that an NTPDase has been identified in any viral genome. Interrogation of public transcriptomic data sets from two koalas identified PhaHV1-specific transcripts in multiple host tissues, including transcripts for the novel NTPDase. PhaHV1 ATPase activity was also demonstrated in vitro, suggesting that the encoded NTPDase is functional during viral infection. In mammals, NTPDases are important in downregulation of the inflammatory and immune responses, but the role of the PhaHV1 NTPDase during viral infection remains to be determined.IMPORTANCE The genome sequences of the koala and wombat gammaherpesviruses show that the viruses form a distinct branch, indicative of a novel genus within the Gammaherpesvirinae Their genomes contain several new ORFs, including ORFs encoding a β-galactoside α-2,6-sialyltransferase that is phylogenetically closest to poxvirus and insect homologs and the first reported viral NTPDase. NTPDases are ubiquitously expressed in mammals and are also present in several parasitic, fungal, and bacterial pathogens. In mammals, these cell surface-localized NTPDases play essential roles in thromboregulation, inflammation, and immune suppression. In this study, we demonstrate that the virus-encoded NTPDase is enzymatically active and is transcribed during natural infection of the host. Understanding how these enzymes benefit viruses can help to inform how they may cause disease or evade host immune defenses.

An anti-amoebic vaccine: generation of the recombinant antigen LC3 from Entamoeba histolytica linked to mutated exotoxin A (PEΔIII) via the Pichia pastoris system

OBJECTIVE

To generate an immunogenic chimeric protein containing the Entamoeba histolytica LC3 fragment fused to the retrograde delivery domains of exotoxin A of Pseudomonas aeruginosa and KDEL3 for use as an effective vaccine.

RESULTS

A codon-optimized synthetic gene encoding the PEΔIII-LC3-KDEL3 fusion construct was designed for expression in Pichia pastoris. This transgene was subcloned into the plasmid pPIC9 for methanol-inducible expression. After transformation and selection of positive-transformed clones by PCR, the expression of the recombinant protein PEΔIII-LC3-KDEL3 was elicited. SDS-PAGE, protein glycosylation staining and western blot assays demonstrated a 67 kDa protein in the medium culture supernatant. The recombinant protein was detected with a polyclonal anti-6X His tag antibody and a polyclonal E. histolytica-specific antibody. A specific antibody response was induced in hamsters after immunization with this protein.

CONCLUSIONS

We report for the first time the design and expression of the recombinant E. histolytica LC3 protein fused to PEΔIII and KDEL3, with potential application as an immunogen.