Infections with extracellular trypanosomes require control by efficient innate immune mechanisms and can result in the destruction of the mammalian humoral immune system

Salivarian trypanosomes are extracellular parasites that affect humans, livestock, and game animals around the world. Through co-evolution with the mammalian immune system, trypanosomes have developed defense mechanisms that allow them to thrive in blood, lymphoid vessels, and tissue environments such as the brain, the fat tissue, and testes. Trypanosomes have developed ways to circumvent antibody-mediated killing and block the activation of the lytic arm of the complement pathway. Hence, this makes the innate immune control of the infection a crucial part of the host-parasite interaction, determining infection susceptibility, and parasitemia control. Indeed, trypanosomes use a combination of several independent mechanisms to avoid clearance by the humoral immune system. First, perpetuated antigenic variation of the surface coat allows to escape antibody-mediated elimination. Secondly, when antibodies bind to the coat, they are efficiently transported toward the endocytosis pathway, where they are removed from the coat proteins. Finally, trypanosomes engage in the active destruction of the mammalian humoral immune response. This provides them with a rescue solution in case antigenic variation does not confer total immunological invisibility. Both antigenic variation and B cell destruction pose significant hurdles for the development of anti-trypanosome vaccine strategies. However, developing total immune escape capacity and unlimited growth capabilities within a mammalian host is not beneficial for any parasite, as it will result in the accelerated death of the host itself. Hence, trypanosomes have acquired a system of quorum sensing that results in density-dependent population growth arrest in order to prevent overpopulating the host. The same system could possibly sense the infection-associated host tissue damage resulting from inflammatory innate immune responses, in which case the quorum sensing serves to prevent excessive immunopathology and as such also promotes host survival. In order to put these concepts together, this review summarizes current knowledge on the interaction between trypanosomes and the mammalian innate immune system, the mechanisms involved in population growth regulation, antigenic variation and the immuno-destructive effect of trypanosomes on the humoral immune system. Vaccine trials and a discussion on the role of innate immune modulation in these trials are discussed at the end

Features of Highly Pathogenic Avian Influenza (HPAI) H5N1 in Domestic Poultry

H5 and H7 subtypes are associated with the highly pathogenic form of AI (HPAI), which are extremely virulent, causing up to 100% mortality in domestic poultry. This virulence and ability to cause systemic infection have been attributed to the multibasic cleavage motif in their hemagglutinin molecule, which are recognized by subtilisin-like endoproteases that are virtually present in every tissue, making them capable of replicating in multiple tissue; hence, lesions are multisystemic (i.e., nervous, circulatory, respiratory, integumentary, musculoskeletal, hemopoietic, gastrointestinal, reproductive systems). The myriads of lesion that accompanied outbreaks of HPAI in domestic poultry as seen in Nigeria from 2006 to 2016 are as a result of the above findings. A critical look at the Nigerian HPAI situation not only revealed the general clinic-pathologic features in domestic poultry and factors that support the persistence of the virus in the environment but also gave insight to the flow of the virus in the country. A situation whereby poultry are kept in free-range, multispecies, multiage holdings with low biosecurity supports the spread of HPAI. Also, the live bird markets (LBMs) that have been fed by this unorganized poultry structure have consistently been the nidus for HPAI detection, be it in 2008 after the virus was thought to have been eradicated or in 2015, when the virus resurfaced in Lagos. It is proposed that all factors enhancing the propensity of the virus to remain in poultry should be giving the attention required. Therefore, it is important that the strict biosecurity measures that ensure prevention of HPAI incursion into poultry premises after 2008 are revamped while improving on the organization of the poultry and product supply chain in the country

Mapping restricted introgression across the genomes of admixed indigenous African cattle breeds

Background: The genomes of indigenous African cattle are composed of components with Middle Eastern (taurine) and South Asian (indicine) origins, providing a valuable model to study hybridization and to identify genetic barriers to gene flow. In this study, we analysed indigenous African cattle breeds as models of hybrid zones, considering taurine and indicine samples as ancestors. In a genomic cline analysis of whole-genome sequence data, we considered over 8 million variants from 144 animals, which allows for fine-mapping of potential genomic incompatibilities at high resolution across the genome. Results: We identified several thousand variants that had significantly steep clines (‘SCV’) across the whole genome, indicating restricted introgression. Some of the SCV were clustered into extended regions, with the longest on chromosome 7, spanning 725 kb and including 27 genes. We found that variants with a high phenotypic impact (e.g. indels, intra-genic and missense variants) likely represent greater genetic barriers to gene flow. Furthermore, our findings provide evidence that a large proportion of breed differentiation in African cattle could be linked to genomic incompatibilities and reproductive isolation. Functional evaluation of genes with SCV suggest that mitonuclear incompatibilities and genes associated with fitness (e.g. resistance to paratuberculosis) could account for restricted gene flow in indigenous African cattle. Conclusions: To our knowledge, this is the first time genomic cline analysis has been applied to identify restricted introgression in the genomes of indigenous African cattle and the results provide extended insights into mechanisms (e.g. genomic incompatibilities) contributing to hybrid differentiation. These results have important implications for our understanding of genetic incompatibilities and reproductive isolation and provide important insights into the impact of cross-breeding cattle with the aim of producing offspring that are both hardy and productive

Tools for Detection of Schistosomiasis in Resource Limited Settings

Schistosomiasis is a debilitating disease affecting over 200 million people, with the highest burden of morbidity and mortality in African countries. Despite its huge impact on the health and socio-economic burden of the society, it remains a neglected tropical disease, with limited attention from governments and stakeholders in healthcare. One of the critical areas that is hugely under-developed is the development of accurate diagnostics for both intestinal and urogenital schistosomiasis. Diagnosis of schistosomiasis is important for the detection and treatment of disease in endemic and non-endemic settings. A conclusive detection method is also an indispensable part of treatment, both in the clinic and during mass drug administration (MDA), for the monitoring efficacy of treatment. Here, we review the available diagnostic methods and discuss the challenges encountered in diagnosis in resource limited settings. We also present the available diagnostics and cost implications for deployment in resource limited settings. Lastly, we emphasize the need for more funding directed towards the development of affordable diagnostic tools that is affordable for endemic countries as we work towards the elimination of the disease

Generation of a nanobody targeting the paraflagellar rod protein of trypanosomes.

Trypanosomes are protozoan parasites that cause diseases in humans and livestock for which no vaccines are available. Disease eradication requires sensitive diagnostic tools and efficient treatment strategies. Immunodiagnostics based on antigen detection are preferable to antibody detection because the latter cannot differentiate between active infection and cure. Classical monoclonal antibodies are inaccessible to cryptic epitopes (based on their size-150 kDa), costly to produce and require cold chain maintenance, a condition that is difficult to achieve in trypanosomiasis endemic regions, which are mostly rural. Nanobodies are recombinant, heat-stable, small-sized (15 kDa), antigen-specific, single-domain, variable fragments derived from heavy chain-only antibodies in camelids. Because of numerous advantages over classical antibodies, we investigated the use of nanobodies for the targeting of trypanosome-specific antigens and diagnostic potential. An alpaca was immunized using lysates of Trypanosoma evansi. Using phage display and bio-panning techniques, a cross-reactive nanobody (Nb392) targeting all trypanosome species and isolates tested was selected. Imunoblotting, immunofluorescence microscopy, immunoprecipitation and mass spectrometry assays were combined to identify the target recognized. Nb392 targets paraflagellar rod protein (PFR1) of T. evansi, T. brucei, T. congolense and T. vivax. Two different RNAi mutants with defective PFR assembly (PFR2RNAi and KIF9BRNAi) were used to confirm its specificity. In conclusion, using a complex protein mixture for alpaca immunization, we generated a highly specific nanobody (Nb392) that targets a conserved trypanosome protein, i.e., PFR1 in the flagella of trypanosomes. Nb392 is an excellent marker for the PFR and can be useful in the diagnosis of trypanosomiasis. In addition, as demonstrated, Nb392 can be a useful research or PFR protein isolation tool

Solid-phase ELISA result.

<p>Coating 5 µg/well of soluble protein of parasite lysates (<i>T. evansi</i> strains, <i>T. congolense and T. vivax</i>) and subsequent recognition by Nb392 and non-relevant nanobody (NbBCII10) as negative control. In each of three separate experiments, lysates were plated in triplicates and detected with Nb392 (shaded boxes) or NbBCII10 (unshaded boxes). Data presented are mean values of three wells (±SD). The mean values of negative control wells are compared to the mean values of corresponding test wells coated with lysates of <i>T. evansi</i> strains, <i>T. vivax</i> and <i>T. congolense</i>, *<i>P</i><0.05, **<i>P</i><0.01, ***<i>P</i><0.001. Results shown are representative of three independent experiments.</p

Western blot analysis on wild type and mutant parasites probed with Nb392 and anti-ALBA as loading control.

<p>From left to right upper panel: WT <i>T. brucei</i> procyclics, <i>PFR2^RNAi</i> uninduced, <i>PFR2^RNAi</i> 2-day induction, <i>KIF9B^RNAi</i> uninduced, <i>KIF9B^RNAi</i> 4-day induction <i>T. evansi</i> blood form, <i>T. brucei</i> WT blood form, <i>T. brucei</i> procyclics WT calibration with 2×10⁶, 1×10⁶, 5×10⁵, 2.5×10⁵ and 1.25×10⁵ parasites. Lower panel: Anti-ALBA antibody used as loading control. Values on the left are given in kilodaltons.</p

List of peptide masses from mass spectra of upper and lower bands and their respective sequence matches with the positions in the genome of <i>T. brucei</i>.

<p>List of peptide masses from mass spectra of upper and lower bands and their respective sequence matches with the positions in the genome of <i>T. brucei</i>.</p