Immunoepidemiological Profiling of Onchocerciasis Patients Reveals Associations with Microfilaria Loads and Ivermectin Intake on Both Individual and Community Levels

Abstract

Mass drug administration (MDA) programmes against Onchocerca volvulus use ivermectin (IVM) which targets microfilariae (MF), the worm's offspring. Most infected individuals are hyporesponsive and present regulated immune responses despite high parasite burden. Recently, with MDA programmes, the existence of amicrofilaridermic (a-MF) individuals has become apparent but little is known about their immune responses. Within this immunoepidemiological study, we compared parasitology, pathology and immune profiles in infection-free volunteers and infected individuals that were MF+ or a-MF. The latter stemmed from villages in either Central or Ashanti regions of Ghana which, at the time of the study, had received up to eight or only one round of MDA respectively. Interestingly, a-MF patients had fewer nodules and decreased IL-10 responses to all tested stimuli. On the other hand, this patient group displayed contrary IL-5 profiles following in vitro stimulation or in plasma and the dampened response in the latter correlated to reduced eosinophils and associated factors but elevated neutrophils. Furthermore, multivariable regression analysis with covariates MF, IVM or the region (Central vs. Ashanti) revealed that immune responses were associated with different covariates: whereas O. volvulus-specific IL-5 responses were primarily associated with MF, IL-10 secretion had a negative correlation with times of individual IVM therapy (IIT). All plasma parameters (eosinophil cationic protein, IL-5, eosinophils and neutrophils) were highly associated with MF. With regards to IL-17 secretion, although no differences were observed between the groups to filarial-specific or bystander stimuli, these responses were highly associated with the region. These data indicate that immune responses are affected by both, IIT and the rounds of IVM MDA within the community. Consequently, it appears that a lowered infection pressure due to IVM MDA may affect the immune profile of community members even if they have not regularly participated in the programmes.

A lack of confirmation with alternative assays questions the validity of IL-17A expression in human neutrophils using immunohistochemistry

“…The combination of stimuli from the filarial nematode and its bacterial endosymbiont Wolbachia could promote a cytokine milieu favourable for the induction of an IL-17-mediated immune response [22], but little is currently known about the actual presence and role of such a response in filariasis [23][24][25]. We identified IL-17A expressing neutrophils in Wolbachia-positive Onchocerca volvulus nodules from infected Cameroonian patients [26] using immunohistochemistry (IHC) staining with a commercially available antibody (R&D Systems, goat polyclonal anti-IL-17A, Nodules from patients infected with O. volvulus were surgically removed, fixed in 80% ethanol and paraffin-embedded as part of the evaluation of a phase II trial of doxycycline [26].…”

Patency of Litomosoides sigmodontis infection depends on Toll‐like receptor 4 whereas Toll‐like receptor 2 signalling influences filarial‐specific CD4+ T‐cell responses

“…The specific ligands, however, remain unclear although potential candidates include the Wolbachia surface protein, which induces TLR activity in vitro and can elicit TNF release in PBMC from healthy individuals in a dose‐dependent manner . Moreover, PBMC from O. volvulus ‐infected individuals produce pro‐inflammatory cytokines when cultured with Wolbachia surface protein, and recently, a recombinant peptidoglycan‐associated lipoprotein (wPAL) elicited higher TNF responses in microfilaridermic individuals compared with amicrofilaridermic cohorts: following regression analysis this was shown to be dependent on the presence of Mf . In vitro experiments have shown that macrophages respond to Brugia malayi antigen or Wolbachia in a TLR2/TLR6‐dependent manner and ES62, a phosphorylcholine‐containing glycoprotein derived from the non‐ Wolbachia containing filarial nematode Acanthocheilonema viteae also signals via TLR4, indicating that the filariae contain TLR‐specific components themselves .…”

“…26 Moreover, PBMC from O. volvulus-infected individuals produce pro-inflammatory cytokines when cultured with Wolbachia surface protein, 26 and recently, a recombinant peptidoglycan-associated lipoprotein (wPAL) elicited higher TNF responses in microfilaridermic individuals compared with amicrofilaridermic cohorts: following regression analysis this was shown to be dependent on the presence of Mf. 49 In vitro experiments have shown that macrophages respond to Brugia malayi antigen or Wolbachia in a TLR2/TLR6-dependent manner 25 and ES62, a phosphorylcholine-containing glycoprotein derived from the non-Wolbachia containing filarial nematode Acanthocheilonema viteae also signals via TLR4, indicating that the filariae contain TLR-specific components themselves. 50 In vivo a study that focused on determining the role of TLR4 and the development of protective immunity noted that C3H/HeJ mice failed to develop immune-mediated larval killing, and spleen cells from those mice produced significantly higher levels of IL-5 upon antigen re-stimulation.…”

“…Groups of WT, TLR2 À/À and TLR4 À/À BALB/c mice were infected with Litomosoides sigmodontis. On days35,49 and 72 post infection (p.i. ), spleen (a) and medLN (b) cells from individual mice were analysed by flow cytometry for the number of Foxp3 + CD25 hi Treg cells within the CD4 + T-cell compartment.…”

Inflammatory and regulatory CCL and CXCL chemokine and cytokine cellular responses in patients with patentMansonella perstansfilariasis

“…In ivermectin-treated onchocerciasis patients the expression of immunity will change; with parasite clearance, depressed cellular responsiveness of both types 1 and 2 will reactivate to O. volvulus and to bystander antigens, while parasite-specific antibody responses will lessen gradually [13][14][15][16][17][18]. Cell culture supernatants were collected after 48 h and chemokine and cytokine secretion was quantified by specific enzyme-linked immunosorbent assay (ELISA) (R&D Systems).…”