Immunohistology of ectopic secondary lymph follicles in subcutaneous nodules from patients with hyperreactive onchocerciasis (sowda)

Ectopic secondary lymph follicles emerge in patients with autoimmune or infectious diseases, e.g. in the synovium in rheumatoid arthritis or the skin in Borrelia burgdorferi infection, but ectopic localisations in the skin are rarely described for helminth infections. We investigated the cellular composition of secondary lymph follicles in subcutaneous nodules from eight patients with hyperreactive onchocerciasis (synonymous “localised” form or sowda) using immunohistology. CD3- and CD45RO-positive T cells and CD20-positive B cells were present in the mantle zone. The germinal centre was characterised by many B cells and CD35-positive follicular dendritic cells, which formed a network of attached IgE- and CD23-positive cells with the low-affinity IgE (epsilon) receptor. Few of the B cells were labelled for IgG1, IgG2 and IgG4, whereas in other zones of the nodule IgG1 was expressed by plasma cells and IgG1-coated dead microfilariae. B cells and few macrophages expressed the MHC class II molecule HLA-DR. Mature CD68-positive tingible body macrophages with phagocytosed leukocytes and CD57-positive lymphocytes occurred in the germinal centre. Macrophages in the germinal centre only weakly expressed alpha1-antichymotrypsin in contrast to macrophages in other zones of the onchocercoma. Furthermore, the multifunctional cytokine TGF-beta was only weakly expressed by macrophages and lymphocytes in the secondary follicles. Only few tryptase-positive mast cells, calprotectin-positive young macrophages, eosinophils and neutrophils occurred in the secondary follicles, although these cells were abundant in the onchocercomas. In conclusion, the ectopic secondary lymph follicles in onchocercomas and lymph nodes from hyperreactive onchocerciasis patients are equally composed

More than seven decades of Acta Tropica: partnership to advance the 2030 Agenda for Sustainable Development

The inaugural issue of Acta Tropica has been published in 1944, at a time of utmost international isolation and uncertainty due to World War II. Now, more than seven decades later, Acta Tropica is a trusted outlet to communicate and disseminate scientific advances in the fields of parasitology and tropical medicine. As a scholarly, peer-reviewed journal, Acta Tropica contributes to the 2030 Agenda for Sustainable Development, particularly the Sustainable Development Goal (SDG) 3, that is "Ensure healthy lives and promote well-being for all of all ages". This article explores how Acta Tropica has evolved over time. Our analysis is based on a systematic review of keywords derived from all issues published in a specific year, arbitrarily selected at decadal snapshots (1950, 1960, 1970, 1980, 1990, 2000, 2010, and 2020). Results indicate a decrease in interdisciplinarity in favour of more specialised expertise in various fields of infectious diseases research and public health with a particular emphasis on low- and middle-income countries. Yet, by examining first and last authors' institutional affiliations and classifying countries by the Human Development Index (HDI), we find that most authors are affiliated with institutions in high- and very high-HDI countries. Over time, the mean number of authors on a paper has increased severalfold (from 1.35 in 1950 to 7.51 in 2020). Taken together, Acta Tropica has become increasingly globally anchored and contributes not only to SDG 3, but increasingly also to SDG 17, that is "Revitalize the global partnership for sustainable development"

Localization of Wolbachia-like gene transcripts and peptides in adult Onchocerca flexuosa worms indicates tissue specific expression

BACKGROUND: Most filarial species in the genus Onchocerca depend on Wolbachia endobacteria to successfully carry out their life cycle. O. flexuosa is a Wolbachia-free species, but its genome contains Wolbachia-like sequences presumably obtained from Wolbachia via horizontal gene transfer. Proteogenomic studies have shown that many of these Wolbachia-like sequences are expressed in adult worms. METHODS: Six Wolbachia-like sequences in O. flexuosa were chosen for further study based on their sequence conservation with Wolbachia genes, length of predicted open reading frames, and expression at the RNA and/or protein levels. In situ hybridization and immunohistochemical labeling were used to localize Wolbachia-like transcripts and peptides in adult worm tissues. RESULTS: RNA probes representing three of the six target sequences produced hybridization signals in worm tissues. These probes bound to transcripts in the intestine and lateral chords of both sexes, in the hypodermis, median chords and uteri in females, and in sperm precursor cells in males. Antibodies raised to three peptides corresponding to these transcripts bound to specific bands in a soluble extract of adult O. flexuosa by Western blot that were not labeled by control antibodies in pre-immune serum. Two of the three antibodies produced labeling patterns in adult worm sections that were similar to those of the RNA probes, while the third produced a different pattern. CONCLUSIONS: A subset of the Wolbachia-like sequences present in the genome of the Wolbachia-free filarial species O. flexuosa are transcribed in tissues where Wolbachia reside in infected filarial species. Some of the peptides and/or proteins derived from these transcripts appear to be concentrated in the same tissues while others may be exported to other regions of the worm. These results suggest that horizontally transferred Wolbachia genes and gene products may replicate important Wolbachia functions in uninfected filarial worms

Strong expression of TGF-beta in human host tissues around subcutaneous Dirofilaria repens

Dirofilaria repens and other Dirofilaria species are widely distributed parasitic nematodes of carnivores, which occasionally are transmitted to men, causing subcutaneous nodules. In humans, it usually occurs only as single male or female filariae without production of microfilariae. The non-productive living or dead Dirofilaria worms in subcutaneous biopsies from 15 human patients permitted us to study the role of the pleiotropic and immunoregulatory cytokine transforming growth factor beta (TGF-beta) independent from the influence of microfilariae. Antiserum against latent TGF-beta 1 was used for an immunohistological examination. In the infiltrates around female and male filariae, there occurred strongly TGF-beta-positive macrophages, mast cells, endothelial cells, fibrocytes, and giant cells adjacent to dead worms. In one nodule, secondary lymph follicles were observed with clearly TGF-beta-positive B cells in the mantle zone and weakly positive macrophages and B cells in the germinal centre. A network of CD35-positive follicular dendritic cells was observed in the germinal centre. All Dirofilaria contained Wolbachia endobacteria, which probably had attracted the numerous TGF-beta-negative neutrophils near to the worm. Wolbachia were phagocytosed by neutrophils adjacent to dead filariae. Macrophages and lymphocytes expressed the MHC class II molecule HLA-DR in small accumulations of immune cells in the outer zone of the infiltrate and the mantle zone and germinal centre of secondary lymph follicles. It is concluded that single non-productive Dirofilaria worms elicit a strong expression of TGF-beta. This result is in accordance with observations on Onchocerca volvulus from patients with the hyporeactive (generalised) form

Efficacy of 5-week doxycycline treatment on adult Onchocerca volvulus.

The effects of 5-week doxycycline treatment on the depletion of Wolbachia endobacteria from Onchocerca volvulus, on the interruption of embryogenesis and on microfilariae production, and with regard to macrofilaricidal activity were studied. In 2003, in an endemic area in Ghana, 22 onchocerciasis patients received 100 mg/day doxycycline for 5 weeks. Two years after the start of the study, 20 treated and ten untreated patients were nodulectomized and skin microfilariae were counted. The onchocercomas were examined by immunohistology for the presence of Wolbachia, embryogenesis, and vitality of adult filariae. The latter two parameters were further assessed by alternating logistic regression analysis, taking into account the dependency of worms and nodules in patients. Doxycycline resulted in depletion of Wolbachia and in complete interruption of embryogenesis in all worms that were assumed to have been present during treatment. In the treated patients, only 51% of the female worms were alive, compared to 84% in the untreated patients, indicating a moderate but distinct macrofilaricidal activity of doxycycline at this dose. It is concluded that, in areas with ongoing transmission, doxycycline cannot replace regular ivermectin mass treatment because new infections would require repeated rounds of doxycycline. However, doxycycline can be used for the treatment of individuals outside transmission areas, in foci where ivermectin resistance may occur, and in countries where onchocerciasis and loiasis are co-endemic

Criteria for the differentiation between young and old Onchocerca volvulus filariae

Drugs exist that show long-lasting inhibition of embryogenesis and microfilaria production or macrofilaricidal activity against Onchocerca volvulus. Therefore, the patients have to be followed-up for several years. Clinical drug trials have to be performed in areas with ongoing transmission to assess the efficacy on younger worms. In addition, future vaccine trials may also require demonstrating efficacy against establishment of new worms. For the evaluation of the efficacy, it is necessary to differentiate between older worms, which were exposed to the drug, and younger worms newly acquired after drug treatment or vaccination. Here, we describe criteria for the differentiation between young and old filariae based on histological studies of worms with a known age from travellers, or from children, or patients living in areas with interrupted transmission in Burkina Faso, Ghana or Uganda. Older worms were larger and presented degenerated tissues. Gomori's iron stain showed that the worms accumulated more iron with increasing age, first in the gut and later in other organs. Using an antibody against O. volvulus lysosomal aspartic protease, the gut of young worms was stained only weakly; whereas, it was stronger labelled in older worms, accompanied by additional staining of hypodermis and epithelia. Using morphological and immunohistological criteria, it was possible to differentiate young (1–3 years old) from older females and to identify young males

Endosymbiont DNA in Endobacteria-Free Filarial Nematodes Indicates Ancient Horizontal Genetic Transfer

Background: Wolbachia are among the most abundant symbiotic microbes on earth; they are present in about 66% of all insect species, some spiders, mites and crustaceans, and most filarial nematode species. Infected filarial nematodes, including many pathogens of medical and veterinary importance, depend on Wolbachia for proper development and survival. The mechanisms behind this interdependence are not understood. Interestingly, a minority of filarial species examined to date are naturally Wolbachia-free. Methodology/PrincipalFindings:We used 454 pyrosequencing to survey the genomes of two distantly related Wolbachia- free filarial species, Acanthocheilonema viteae and Onchocerca flexuosa. This screen identified 49 Wolbachia-like DNA sequences in A. viteae and 114 in O. flexuosa. qRT-PCR reactions detected expression of 30 Wolbachia-like sequences in A. viteae and 56 in O. flexuosa. Approximately half of these appear to be transcribed from pseudogenes. In situ hybridization showed that two of these pseudogene transcripts were specifically expressed in developing embryos and testes of both species. Conclusions/Significance: These results strongly suggest that the last common ancestor of extant filarial nematodes was infected with Wolbachia and that this former endosymbiont contributed to their genome evolution. Horizontally transferred Wolbachia DNA may explain the ability of some filarial species to live and reproduce without the endosymbiont while other species cannot

Wolbachia endobacteria depletion by doxycycline as antifilarial therapy has macrofilaricidal activity in onchocerciasis: a randomized placebo-controlled study

In a randomized, placebo-controlled trial in Ghana, 67 onchocerciasis patients received 200-mg/day doxycycline for 4–6 weeks, followed by ivermectin (IVM) after 6 months. After 6–27 months, efficacy was evaluated by onchocercoma histology, PCR and microfilariae determination. Administration of doxycycline resulted in endobacteria depletion and female worm sterilization. The 6-week treatment was macrofilaricidal, with >60% of the female worms found dead, despite the presence of new, Wolbachia-containing worms acquired after the administration of doxycycline. Doxycycline may be developed as second-line drug for onchocerciasis, to be administered in areas without transmission, in foci with IVM resistance and in areas with Loa co-infections

IL10 Haplotype Associated with Tuberculin Skin Test Response but Not with Pulmonary TB

Evidence from genetic association and twin studies indicates that susceptibility to tuberculosis (TB) is under genetic control. One gene implicated in susceptibility to TB is that encoding interleukin-10 (IL10). In a group of 2010 Ghanaian patients with pulmonary TB and 2346 healthy controls exposed to Mycobacterium tuberculosis, among them 129 individuals lacking a tuberculin skin test (PPD) response, we genotyped four IL10 promoter variants at positions −2849 , −1082 , −819 , and −592 and reconstructed the haplotypes. The IL10 low-producer haplotype −2849A/−1082A/−819C/−592C, compared to the high-producer haplotype −2849G/−1082G/−819C/−592C, occurred less frequent among PPD-negative controls than among cases (OR 2.15, CI 1.3–3.6) and PPD-positive controls (OR 2.09, CI 1.2–3.5). Lower IL-10 plasma levels in homozygous −2849A/−1082A/−819C/−592C carriers, compared to homozygous −2849G/−1082G/−819C/−592C carriers, were confirmed by a IL-10 ELISA (p = 0.016). Although we did not observe differences between the TB patients and all controls, our results provide evidence that a group of individuals exposed to M. tuberculosis transmission is genetically distinct from healthy PPD positives and TB cases. In these PPD-negative individuals, higher IL-10 production appears to reflect IL-10-dependent suppression of adaptive immune responses and sustained long-term specific anergy