Browsing by Author "Horsnell, William G C"
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- ItemOpen AccessDelayed goblet cell hyperplasia, acetylcholine receptor expression, and worm expulsion in SMC-specific IL-4Ralpha-deficient mice(Public Library of Science, 2007) Horsnell, William G C; Cutler, Antony J; Hoving, J Claire; Mearns, Helen; Myburgh, Elmarie; Arendse, Berenice; Finkelman, Fred D; Owens, Gary K; Erle, Dave; Brombacher, FrankInterleukin 4 receptor α (IL-4Rα) is essential for effective clearance of gastrointestinal nematode infections. Smooth muscle cells are considered to play a role in the type 2 immune response-driven expulsion of gastrointestinal nematodes. Previous studies have shown in vitro that signal transducer and activator of transcription 6 signaling in response to parasitic nematode infection significantly increases smooth muscle cell contractility. Inhibition of the IL-4Rα pathway inhibits this response. How this response manifests itself in vivo is unknown. In this study, smooth muscle cell IL-4Rα-deficient mice (SM-MHC Cre IL-4Rα −/lox ) were generated and characterized to uncover any role for IL-4/IL-13 in this non-immune cell type in response to Nippostrongylus brasiliensis infection. IL-4Rα was absent from α-actin-positive smooth muscle cells, while other cell types showed normal IL-4Rα expression, thus demonstrating efficient cell-type-specific deletion of the IL-4Rα gene. N. brasiliensis -infected SM-MHC Cre IL-4Rα −/lox mice showed delayed ability to resolve infection with significantly prolonged fecal egg recovery and delayed worm expulsion. The delayed expulsion was related to a delayed intestinal goblet cell hyperplasia, reduced T helper 2 cytokine production in the mesenteric lymph node, and reduced M3 muscarinic receptor expression during infection. Together, these results demonstrate that in vivo IL-4Rα-responsive smooth muscle cells are beneficial for N. brasiliensis expulsion by coordinating T helper 2 cytokine responses, goblet hyperplasia, and acetylcholine responsiveness, which drive smooth muscle cell contractions.
- ItemOpen AccessIL-4Rα-associated antigen processing by B cells promotes immunity in Nippostrongylus brasiliensis infection(Public Library of Science, 2013) Horsnell, William G C; Darby, Matthew G; Hoving, Jennifer C; Nieuwenhuizen, Natalie; McSorley, Henry J; Ndlovu, Hlumani; Bobat, Saeeda; Kimberg, Matti; Kirstein, Frank; Cutler, Anthony JIn this study, B cell function in protective TH2 immunity against N. brasiliensis infection was investigated. Protection against secondary infection depended on IL-4Rα and IL-13; but not IL-4. Protection did not associate with parasite specific antibody responses. Re-infection of B cell-specific IL-4Rα−/− mice resulted in increased worm burdens compared to control mice, despite their equivalent capacity to control primary infection. Impaired protection correlated with reduced lymphocyte IL-13 production and B cell MHC class II and CD86 surface expression. Adoptive transfer of in vivo N. brasiliensis primed IL-4Rα expressing B cells into naïve BALB/c mice, but not IL-4Rα or IL-13 deficient B cells, conferred protection against primary N. brasiliensis infection. This protection required MHC class II compatibility on B cells suggesting cognate interactions by B cells with CD4+ T cells were important to co-ordinate immunity. Furthermore, the rapid nature of these protective effects by B cells suggested non-BCR mediated mechanisms, such as via Toll Like Receptors, was involved, and this was supported by transfer experiments using antigen pulsed Myd88−/− B cells. These data suggest TLR dependent antigen processing by IL-4Rα-responsive B cells producing IL-13 contribute significantly to CD4+ T cell-mediated protective immunity against N. brasiliensis infection.
- ItemOpen AccessAn investigation of the effects of helminth worm infection on the capacity of HIV vaccines to boost vaccine-generated immune responses(2017) Humby, Samantha A; Chege, Gerald K; Williamson, Anna-Lise; Horsnell, William G CTo protect against sexual transmission, successful future HIV vaccines will likely be given to adolescents as a booster subsequent to primary immunization during infancy. In sub-Saharan Africa (SSA), a large proportion of children are chronically infected with a variety of helminths. These infections may suppress the ability of a host to elicit vaccine-induced Th1 responses that are considered important for a successful HIV vaccine. This study investigated the effect of chronic helminthic infection on the boosting capacity of a poxvirus-protein HIV vaccine regimen (SAAVI MVA-C and Env gp140 protein) in a mouse model. Groups of mice were prime-vaccinated with SAAVI MVA-C through an intramuscular injection, and Env gp140 protein formulated in Alum adjuvant which was administered via an intraperitoneal injection. These vaccinations were given concurrently, 2 weeks prior to infection with Schistosoma mansoni (Sm) through a percutaneous route. Control mice were either left uninfected (Naïve) or infected in the same manner (Sm) without vaccination. A booster vaccination was given 8 weeks post helminth infection. HIV-specific immune responses were analysed in the blood and spleens two weeks after booster vaccination. The magnitudes of cumulative IFN-γ ELISPOT responses to HIV Gag, RT and Env peptides were significantly (p<0.05) lower in the vaccinated and Sm-infected (Vaccine+Sm) mice (948 sfu/106) than vaccinated and uninfected (Vaccine) mice (1733 sfu/106), with IFN-γ responses to RT (CD8) being the most dominant for both mouse groups (Vaccine+Sm: 734 ± 221 sfu/106, Vaccine: 521 ± 116 sfu/106). No significant difference was observed in the magnitudes of cumulative IL-2 ELISPOT responses to the vaccine peptides between the Vaccine+Sm and Vaccine groups, however IL-2-producing T cell responses to Env (CD4) dominated in both mouse groups. Vaccine+Sm and Sm groups had similar IFN-γ- and IL-2-producing T cell responses to SEA. Splenocytes from Vaccine+Sm mice secreted less Th1 (IFN-γ, IL-2, TNF- α) and Th2 (IL-4, IL-6, IL-10) cytokines than those from uninfected vaccinated mice in response to HIV vaccine peptides. The total number of activated CD4+ T cells responding to vaccine peptides was greater for Vaccine+ Sm mice than Vaccine mice (p<0.05), however, no such statistical significance was observed in the differences seen between these vaccinated mouse groups for the number of activated CD8+ T cells. The frequencies of central memory activated CD4+ T cells were seen to be greater in Vaccine group (Gag; 34.28 ± 8.35%, Pol; 33.53 ± 6.34%, Env(CD4); 33.92 ± 3.87%, Env (CD8); 38.76 ± 10.52%) as opposed to the Vaccine+Sm group (Gag; 28.09 ± 3.95%, Pol; 26.45 ± 4.66%, Env (CD4); 28.79 ± 6.95%, Env (CD8); 28.65 ± 3.29%). Furthermore, Vaccine+Sm mice had higher titres of HIV-1 gp140- specific IgG1 antibodies (p<0.0001) (a Th2 antibody marker) but significantly less gp140- specific IgG2a (p<0.0001) and IgG2b (p<0.001) (Th1 antibody markers) antibodies. This trend was also observed with total non-Env-specific antibody titres. This study demonstrates that chronic helminthic infection is associated with an attenuated boosting capacity of a poxvirus-protein HIV vaccine in a mouse model, suppressing both T cell cytokine production and Th1-type antibody responses. Since HIV vaccine-induced Th1 responses are considered important for a successful HIV vaccine, these data suggest that chronic helminthiasis may impact negatively on future HIV vaccination outcomes in adolescents living in SSA where helminthic parasites are endemic.
- ItemOpen AccessAn investigation of the impact of parasitic worm infection on the immunogenicity of candidate HIV vaccines(2017) Dzhivhuho, Godfrey Azwindini; Chege, Gerald K; Williamson, Anna-Lise; Horsnell, William G CDevelopment of effective and affordable HIV vaccines is one of the best and cost-effective strategies for controlling the HIV epidemic and a top priority in endemic areas. Successful future candidate HIV vaccines are expected to elicit effective antibody and T cell-mediated responses. This is envisaged to be attained through induction of potent T cell-mediated immune responses to control viral replication in the tissues and disease progression as well as a durable antibody immune response which comprises of broadly neutralizing antibodies to block virus entry at the mucosal sites. Both types of immune responses are influenced by a T helper cell type 1 (Th1) immune response. In developing worlds such as Sub-Saharan Africa co-infections of HIV and schistosomiasis are common. Helminth infections such as schistosomiasis induce strong Th2 biased immune responses that have been reported to alter HBV, BCG, Tetanus toxoid and some candidate HIV vaccine-specific immune responses. Because Th1 and Th2 are almost mutually exclusive, it is suggested that, in the presence of chronic helminthic infections, Th1 responses elicited by HIV vaccine may be attenuated, hence, reduce vaccine efficiency. On the other hand, vaccination with an effective HIV vaccine might shift the immune bias towards a Th1 response, resulting in worsening of the helminth-associated pathology, thus, making the vaccine unsafe to the recipients. This study aimed at investigating if chronic helminth infection (Schistosoma mansoni: Sm) has a negative impact on the immunogenicity of HIV vaccine candidates (SAAV DNA-C2, SAAVI MVA-C, and Env gp140 protein) previously shown to induce cellular, mixed and antibody immune responses in mice. The objectives of this study were to (i) infect mice with live Schistosoma mansoni infection in order to induce a predominantly Th2 immune response in a mouse model; (ii) evaluate if helminth-induced Th2 immune biasing negatively affects responses to candidate HIV vaccines; (iii) evaluate the ability of ant ihelminthic chemotherapy in restoring normal responses to HIV vaccines in helminth infected mice; (iv) evaluated if HIV vaccine that predominantly induces strong cellular immune responses result in worsening of the helminth-associated pathology and (v) evaluate if helminth eggs in the absence of live helminth infection drives a Th2-dominant response that can affect HIV vaccine responses. The BALB/c mouse model has been used extensively at the University of Cape Town for studying the Smassociated immunology as well as for initial evaluation of candidate HIV vaccines. Female BALB/c mice were either chronically infected with Sm cercariae or inoculated with Sm eggs (SmE) before being subsequently vaccinated twice, 4 weeks apart with three vaccination regimes that elicit cellular (SAAVI DNA-C2 prime + MVA-C boost denoted: DNA+MVA), antibody (gp140 Env protein) and mixed cellular and antibody (SAAVI MVA-C prime + gp140 Env protein boost denoted: MVA+gp140) responses. Some groups of mice infected with live Sm were treated twice with praziquantel (PZQ) prior to vaccination. Spleens, blood and livers were harvested for analysis of vaccine-specific T cell, antibody responses and histological studies using ELISpot, ELISA, CBA, ICS staining, H&E/CAB staining and hydroxyproline assay. Our findings demonstrated that in a mouse model, chronic Sm-infection induces a predominantly Th2 immune biased response marked with elevated parasite-specific IL-4; IL-6 and IL-10 as well as elevated total IgG1 and IgM, while resulting in decreased Th1 markers. Furthermore, chronic infection significantly inhibited cellular responses to the MVA+gp140 vaccine regimen shown by IFN-γ and IL-2 ELISpot; CBA and ICS staining. Similarly, in DNA+MVA vaccinated mice, a significant reduction in vaccine-specific responses was observed in Sm-infected groups compared to uninfected vaccinated groups shown by IFN-γ and IL-2 ELISpot; CBA and ICS against HIV immunogens. antihelminthic treatment with PZQ resulted in the partial restoration of Th1-Th2 balance in the Sm-infected hosts, with the levels of vaccine-induced IFN-γ; TNF-α and IL-2 being partially restored despite the presence of elevated Th2 cytokines after treatment with PZQ. A significant overall decrease in Env gp140 specific IgG, IgG1, IgG2a and IgG2b antibody responses was observed in the Sm-infected mice vaccinated with gp140 or MVA+gp140 vaccine regimen compared to uninfected vaccinated controls. Surprisingly, antihelminthic treatment did not restore vaccineinduced antibody responses. Our histology data showed that DNA+MVA vaccinated mice develop increased liver pathology during chronic schistosomiasis compared to unvaccinated Sm-infected groups shown by larger livers; spleen and enlarged granuloma formation. However, no significant difference in collagen content (a marker of fibrosis) measured by hydroxyproline assay in both vaccinated and unvaccinated infected groups was observed. Our findings further demonstrated that in a mouse model, inoculation with SmE also induces a predominantly Th2 immune biased response marked with elevated parasite-specific IL-4; IL-6 and IL-10 while resulting in decreased Th1 markers. No significant impact on cellular responses evaluated by ELISpot and CBA were observed. However, gp140 specific IgG, IgG1 IgG2a and IgG2b antibody responses were significantly reduced in groups challenged with SmE. Overall, these findings show that chronic helminthiasis in the mouse model induces a strong Th2 biasing which is associated with attenuation of both T cell and antibody response to HIV vaccines. Elimination of helminths by chemotherapy may partially restore T cell responses, but not necessarily antibody responses. These findings further suggest that vaccinating helminth infected individuals with HIV vaccines that induce strong cellular responses may increase the pathology induced by the parasites, rendering the vaccine unsafe in helminth endemic areas. Furthermore, this study suggested that in the absence of an active chronic Sm-infection, SmE left trapped in the tissues following antihelminthic treatment, may continue to induce strong Th2 responses which are capable of downregulating vaccine-specific responses, especially the antibody-mediated responses. This study strongly recommends that development of HIV vaccines should also focus on designing vaccines that can overcome helminth-induced immunity.
- ItemOpen AccessNippostrongylus-induced intestinal hypercontractility requires IL-4 receptor alpha-responsiveness by T cells in mice(Public Library of Science, 2012) Schmidt, Saskia; Hoving, J Claire; Horsnell, William G C; Mearns, Helen; Cutler, Antony J; Brombacher, Tiroyaone M; Brombacher, FrankGut-dwelling helminthes induce potent IL-4 and IL-13 dominated type 2 T helper cell (T H 2) immune responses, with IL-13 production being essential for Nippostrongylus brasiliensis expulsion. This T H 2 response results in intestinal inflammation associated with local infiltration by T cells and macrophages. The resulting increased IL-4/IL-13 intestinal milieu drives goblet cell hyperplasia, alternative macrophage activation and smooth muscle cell hypercontraction. In this study we investigated how IL-4-promoted T cells contributed to the parasite induced effects in the intestine. This was achieved using pan T cell-specific IL-4 receptor alpha-deficient mice (iLck cre IL-4Rα −/lox ) and IL-4Rα-responsive control mice. Global IL-4Rα −/− mice showed, as expected, impaired type 2 immunity to N. brasiliensis . Infected T cell-specific IL-4Rα-deficient mice showed comparable worm expulsion, goblet cell hyperplasia and IgE responses to control mice. However, impaired IL-4-promoted T H 2 cells in T cell-specific IL-4Rα deficient mice led to strikingly reduced IL-4 production by mesenteric lymph node CD4 + T cells and reduced intestinal IL-4 and IL-13 levels, compared to control mice. This reduced IL-4/IL-13 response was associated with an impaired IL-4/IL-13-mediated smooth muscle cell hypercontractility, similar to that seen in global IL-4Rα −/− mice. These results demonstrate that IL-4-promoted T cell responses are not required for the resolution of a primary N. brasiliensis infection. However, they do contribute significantly to an important physiological manifestation of helminth infection; namely intestinal smooth muscle cell-driven hypercontractility.
- ItemOpen AccessSurfactant Protein-D is essential for immunity to Helminth Infection(Public Library of Science, 2016) Thawer, Sumaiyya; Auret, Jennifer; Schnoeller, Corinna; Chetty, Alisha; Smith, Katherine; Darby, Matthew; Roberts, Luke; Mackay, Rosie-Marie; Whitwell, Harry J; Timms, John F; Madsen, Jens; Selkirk, Murray E; Brombacher, Frank; Clark, Howard William; Horsnell, William G CAuthor Summary Infections by parasitic worms are very common, and controlling them is a major medical and veterinary challenge. Very few drugs exist to treat them, and the parasites can develop resistance to these. In order to find new ways to control worm infections, understanding how our immune system responds to them is essential. Many important parasitic worm infections move through the host lung. In this study we show that a major secreted protein in the lung, Surfactant Protein D (SP-D), is essential for immunity to a parasitic worm infection. We found that this protein binds to worm larvae in the lung to help the immune system kill them. Infecting mice that do not express SP-D with worms demonstrates SP-D is important in this immune response. These mice are unable to launch an effective anti-worm immune response and have many more worms in their intestine compared to mice that do express SP-D. We also show that if we increase SP-D levels in the lung the mouse has better immunity to worms. Together this shows for the first time that SP-D is very important for immunity to worm infections.