Protective Cell-mediated Immunity Research Articles

Aging modifies endometrial dendritic cell function and unconventional double negative T cells in the human genital mucosa

BackgroundImmune function in the genital mucosa balances reproduction with protection against pathogens. As women age, genital infections, and gynecological cancer risk increase, however, the mechanisms that regulate cell-mediated immune protection in the female genital tract and how they change with aging remain poorly understood. Unconventional double negative (DN) T cells (TCRαβ + CD4-CD8-) are thought to play important roles in reproduction in mice but have yet to be characterized in the human female genital tract. Using genital tissues from women (27–77 years old), here we investigated the impact of aging on the induction, distribution, and function of DN T cells throughout the female genital tract.ResultsWe discovered a novel site-specific regulation of dendritic cells (DCs) and unconventional DN T cells in the genital tract that changes with age. Human genital DCs, particularly CD1a + DCs, induced proliferation of DN T cells in a TFGβ dependent manner. Importantly, induction of DN T cell proliferation, as well as specific changes in cytokine production, was enhanced in DCs from older women, indicating subset-specific regulation of DC function with increasing age. In human genital tissues, DN T cells represented a discrete T cell subset with distinct phenotypical and transcriptional profiles compared to CD4 + and CD8 + T cells. Single-cell RNA and oligo-tag antibody sequencing studies revealed that DN T cells represented a heterogeneous population with unique homeostatic, regulatory, cytotoxic, and antiviral functions. DN T cells showed relative to CD4 + and CD8 + T cells, enhanced expression of inhibitory checkpoint molecules and genes related to immune regulatory as well as innate-like anti-viral pathways. Flow cytometry analysis demonstrated that DN T cells express tissue residency markers and intracellular content of cytotoxic molecules. Interestingly, we demonstrate age-dependent and site-dependent redistribution and functional changes of genital DN T cells, with increased cytotoxic potential of endometrial DN T cells, but decreased cytotoxicity in the ectocervix as women age, with implications for reproductive failure and enhanced susceptibility to infections respectively.ConclusionsOur deep characterization of DN T cell induction and function in the female genital tract provides novel mechanistic avenues to improve reproductive outcomes, protection against infections and gynecological cancers as women age.

Acute rotavirus infection is associated with the induction of circulating memory CD4+ T cell subsets

Strong CD4+ T cell-mediated immune protection following rotavirus infection has been observed in animal models, but its relevance in humans remains unclear. Here, we characterized acute and convalescent CD4+ T cell responses in children who were hospitalized with rotavirus-positive and rotavirus-negative diarrhoea in Blantyre, Malawi. Children presenting with laboratory-confirmed rotavirus infection had higher proportions of effector and central memory T helper 2 cells during acute infection i.e., at disease presentation compared to convalescence, 28 days post-infection defined by a follow-up 28 days after acute infection. However, circulating cytokine-producing (IFN-γ and/or TNF-α) rotavirus-specific VP6-specific CD4+ T cells were rarely detectable in children with rotavirus infection at both acute and convalescent stages. Moreover, following whole blood mitogenic stimulation, the responding CD4+ T cells were predominantly non-cytokine producers of IFN-γ and/or TNF-α. Our findings demonstrate limited induction of anti-viral IFN-γ and/or TNF-α-producing CD4+ T cells in rotavirus-vaccinated Malawian children following the development of laboratory-confirmed rotavirus infection.

Leishmania donovani Attenuates Dendritic Cell Trafficking to Lymph Nodes by Inhibiting C-Type Lectin Receptor 2 Expression via Transforming Growth Factor-β.

To initiate an antileishmanial adaptive immune response, dendritic cells (DCs) must carry Leishmania antigens from peripheral tissues to local draining lymph nodes. However, the migratory capacity of DCs is largely compromised during Leishmania donovani infection. The molecular mechanism underlying this defective DC migration is not yet fully understood. Here, we demonstrate that L. donovani infection impaired the lymph node homing ability of DCs by decreasing C-type lectin receptor 2 (CLEC-2) expression. L. donovani exerted this inhibitory effect by inducing transforming growth factor-β (TGF-β) secretion from DCs. Indeed, TGF-β produced in this manner inhibited nuclear factor-κB (NF-κB)-mediated CLEC-2 expression on DCs by activating c-Src. Notably, suppression of c-Src expression significantly improved the arrival of DCs in draining lymph nodes by preventing L. donovani-induced CLEC-2 downregulation on DCs. These findings reveal a unique mechanism by which L. donovani inhibits DC migration to lymph nodes and suggest a key role for TGF-β, c-Src, and CLEC-2 in regulating this process. IMPORTANCE Dendritic cells (DCs) play a key role in initiating T cell-mediated protective immunity against visceral leishmaniasis (VL), the second most lethal parasitic disease in the world. However, the T cell-inducing ability of DCs critically depends on the extent of DC migration to regional lymph nodes. Notably, the migration of DCs is reported to be impaired during VL. The cause of this impaired DC migration, however, remains ill-defined. Here, we provide the first evidence that L. donovani, the causative agent of VL, attenuates the lymph node homing capacity of DCs by decreasing C-type lectin receptor 2 (CLEC-2) expression on DCs. Additionally, we have demonstrated how L. donovani mediates this inhibitory effect. Overall, our work has revealed a unique mechanism underlying L. donovani-induced impairment of DC migration and suggests a potential strategy to improve antileishmanial T cell activity by increasing DC arrival in lymph nodes.

The role of Monocyte Chemoattractant Protein-Induced Protein-1 in the regulation of the immune responses to mycobacterial infection

Abstract Mycobacterium tuberculosis (Mtb) infection is mainly controlled by protective cell-mediated immunity. TNFα and other mediators, such as nitric oxide (NO), are crucial to the macrophage’s antimicrobial activity. The RNA-binding protein MCPIP1 is a zinc-finger protein with RNase activity that targets the 3’UTR region of cytokine’s mRNA for degradation like IL-6, IL-1β, and IL-12. Here, we aim to investigate the role of MCPIP1 during infection and its contribution to Mtb’s immune evasion. Our observations show that MCPIP1 increases after Mtb infection, correlating with disease progression. Similarly, global MCPIP1 KO (MCPIP1 −/−) mice showed lower lung bacterial burden than WT mice after 30 days. To address wheater the reduced number of bacteria was due to the macrophage’s absent MCPIP1 expression, we generated myeloid-specific MCPIP1 KO mice (M-MCPIP1 −/−). M-MCPIP1 −/−mice showed a similar reduction of bacterial growth as the MCPIP1 −/−mice compared with their WT littermates. Infection of bone marrow-derived macrophages confirmed that myeloid-MCPIP1 deficient cells had improved control of bacterial growth with increased IL-1β, IL-6, IL-12, iNOS, and TNFα. To evidence the mechanism by which M-MCPIP1 −/−macrophages contribute to Mtb growth control, we blocked TNFα and iNOS activity. Results showed that protection in M-MCPIP1 −/−is partly due to these molecule’s high expression, as the blockade of these mediators increased the bacterial burden. Our preliminary data suggest that the induction of MCPIP1 contributes to the bacteria’s immune evasion by targeting critical anti-TB molecules. Further experiments are needed to understand the mechanisms involved and consider MCPIP1 as a target for host-directed therapy for TB. R21AI151936 R21AI171734

Plasmodium-encoded murine IL-6 impairs liver stage infection and elicits long-lasting sterilizing immunity.

Plasmodium sporozoites (SPZ) inoculated by Anopheles mosquitoes into the skin of the mammalian host migrate to the liver before infecting hepatocytes. Previous work demonstrated that early production of IL-6 in the liver is detrimental for the parasite growth, contributing to the acquisition of a long-lasting immune protection after immunization with live attenuated parasites. Considering that IL-6 as a critical pro-inflammatory signal, we explored a novel approach whereby the parasite itself encodes for the murine IL-6 gene. We generated transgenic P. berghei parasites that express murine IL-6 during liver stage development. Though IL-6 transgenic SPZ developed into exo-erythrocytic forms in hepatocytes in vitro and in vivo, these parasites were not capable of inducing a blood stage infection in mice. Furthermore, immunization of mice with transgenic IL-6-expressing P. berghei SPZ elicited a long-lasting CD8+ T cell-mediated protective immunity against a subsequent infectious SPZ challenge. Collectively, this study demonstrates that parasite-encoded IL-6 attenuates parasite virulence with abortive liver stage of Plasmodium infection, forming the basis of a novel suicide vaccine strategy to elicit protective antimalarial immunity.

Alpha-galactosylceramide as adjuvant induces protective cell-mediated immunity against Leishmania mexicana infection in vaccinated BALB/c mice.

Adjuvants represent a promising strategy to improve vaccine effectiveness against infectious diseases such as leishmaniasis. Vaccination with the invariant natural killer T cell ligand α-galactosylceramide (αGalCer) has been used successfully as adjuvant, generating a Th1-biased immunomodulation. This glycolipid enhances experimental vaccination platforms against intracellular parasites including Plasmodium yoelii and Mycobacterium tuberculosis. In the present study, we assessed the protective immunity induced by a single-dose intraperitoneal injection of αGalCer (2μg) co-administrated with a lysate antigen of amastigotes (100μg) against Leishmania mexicana infection in BALB/c mice. The prophylactic vaccination led to 5.0-fold reduction of parasite load at the infection site, compared to non-vaccinated mice. A predominant pro-inflammatory response was observed in challenged vaccinated mice, represented by a 1.9 and 2.8-fold-increase of IL-1β and IFN-γ producing cells, respectively, in the lesions, and by 23.7-fold-increase of IFN-γ production in supernatants of restimulated splenocytes, all compared to control groups. The co-administration of αGalCer also stimulated the maturation of splenic dendritic cells and modulated a Th1-skewed immune response, with high amounts of IFN-γ production in serum. Furthermore, peritoneal cells of αGalCer-immunized mice exhibited an elevated expression of Ly6G and MHCII. These findings indicate that αGalCer improves protection against cutaneous leishmaniasis, supporting evidence for its potential use as adjuvant in Leishmania-vaccines.

IFN-γ production by brain-resident cells activates cerebral mRNA expression of a wide spectrum of molecules critical for both innate and T cell-mediated protective immunity to control reactivation of chronic infection with Toxoplasma gondii.

We previously demonstrated that brain-resident cells produce IFN-γ in response to reactivation of cerebral infection with Toxoplasma gondii. To obtain an overall landscape view of the effects of IFN-γ from brain-resident cells on the cerebral protective immunity, in the present study we employed NanoString nCounter assay and quantified mRNA levels for 734 genes in myeloid immunity in the brains of T and B cell-deficient, bone marrow chimeric mice with and without IFN-γ production by brain-resident cells in response to reactivation of cerebral T. gondii infection. Our study revealed that IFN-γ produced by brain-resident cells amplified mRNA expression for the molecules to activate the protective innate immunity including 1) chemokines for recruitment of microglia and macrophages (CCL8 and CXCL12) and 2) the molecules for activating those phagocytes (IL-18, TLRs, NOD1, and CD40) for killing tachyzoites. Importantly, IFN-γ produced by brain-resident cells also upregulated cerebral expression of molecules for facilitating the protective T cell immunity, which include the molecules for 1) recruiting effector T cells (CXCL9, CXCL10, and CXCL11), 2) antigen processing (PA28αβ, LMP2, and LMP7), transporting the processed peptides (TAP1 and TAP2), assembling the transported peptides to the MHC class I molecules (Tapasin), and the MHC class I (H2-K1 and H2-D1) and Ib molecules (H2-Q1, H-2Q2, and H2-M3) for presenting antigens to activate the recruited CD8+ T cells, 3) MHC class II molecules (H2-Aa, H2-Ab1, H2-Eb1, H2-Ea-ps, H2-DMa, H2-Ob, and CD74) to present antigens for CD4+ T cell activation, 4) co-stimulatory molecules (ICOSL) for T cell activation, and 5) cytokines (IL-12, IL-15, and IL-18) facilitating IFN-γ production by NK and T cells. Notably, the present study also revealed that IFN-γ production by brain-resident cells also upregulates cerebral expressions of mRNA for the downregulatory molecules (IL-10, STAT3, SOCS1, CD274 [PD-L1], IL-27, and CD36), which can prevent overly stimulated IFN-γ-mediated pro-inflammatory responses and tissue damages. Thus, the present study uncovered the previously unrecognized the capability of IFN-γ production by brain-resident cells to upregulate expressions of a wide spectrum of molecules for coordinating both innate and T cell-mediated protective immunity with a fine-tuning regulation system to effectively control cerebral infection with T. gondii.

Enhanced SARS-CoV-2-Specific CD4+ T Cell Activation and Multifunctionality in Late Convalescent COVID-19 Individuals.

Background: Examination of CD4+ T cell responses during the natural course of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection offers useful information for the improvement of vaccination strategies against this virus and the protective effect of these T cells. Methods: We characterized the SARS-CoV-2-specific CD4+ T cell activation marker, multifunctional cytokine and cytotoxic marker expression in recovered coronavirus disease 2019 (COVID-19) individuals. Results: CD4+ T-cell responses in late convalescent (>6 months of diagnosis) individuals are characterized by elevated frequencies of activated as well as mono, dual- and multi-functional Th1 and Th17 CD4+ T cells in comparison to early convalescent (<1 month of diagnosis) individuals following stimulation with SARS-CoV-2-specific antigens. Similarly, the frequencies of cytotoxic marker expressing CD4+ T cells were also enhanced in late convalescent compared to early convalescent individuals. Conclusion: Our findings from a low-to middle-income country suggest protective adaptive immune responses following natural infection of SARS-CoV-2 are elevated even at six months following initial symptoms, indicating the CD4+ T cell mediated immune protection lasts for six months or more in natural infection.

Immunoadjunctive Therapy against Bacterial Infections Using Herbal Medicines Based on Th17 Cell-mediated Protective Immunity.

One of the major health concerns in the world is the global increase in intractable bacterial infectious diseases due to the emergence of multi- and extensively drug-resistant bacterial pathogens as well as increase in compromised hosts around the world. Particularly, in the case of mycobacteriosis, the high incidence of tuberculosis in developing countries, resurgence of tuberculosis in industrialized countries, and increase in the prevalence of Mycobacterium avium complex infections are important worldwide health concerns. However, the development of novel antimycobacterial drugs is currently making slow progress. Therefore, it is considered that devising improved administration protocols for clinical treatment against refractory mycobacteriosis using existing chemotherapeutics is more practical than awaiting the development of new antimycobacterial drugs. The regulation of host immune responses using immunoadjunctive agents may increase the efficacy of antimicrobial treatment against mycobacteriosis. The same situations also exist in cases of intractable infectious diseases due to common bacteria other than mycobacteria. The mild and long-term up-regulation of host immune reactions in hosts with intractable chronic bacterial infections, using herbal medicines and medicinal plants, may be beneficial for such immunoadjunctive therapy. This review describes the current status regarding basic and clinical studies on therapeutic regimens using herbal medicines, useful for the clinical treatment of patients with intractable bacterial infections. In particular, we focus on immunoadjunctive effects of herbal medicines on the establishment and manifestation of host antibacterial immunity related to the immunological roles of Th17 cell lineages.

Novel mumps virus epitopes reveal robust cytotoxic T cell responses after natural infection but not after vaccination

Mumps is nowadays re-emerging despite vaccination. The contribution of T cell immunity to protection against mumps has not been clearly defined. Previously, we described a set of 41 peptides that were eluted from human leukocyte antigen (HLA) class I molecules of mumps virus (MuV)-infected cells. Here, we confirmed immunogenicity of five novel HLA-B*07:02- and HLA-A*01:01-restricted MuV T cell epitopes from this set of peptides. High frequencies of T cells against these five MuV epitopes could be detected ex vivo in all tested mumps patients. Moreover, these epitope-specific T cells derived from mumps patients displayed strong cytotoxic activity. In contrast, only marginal T cell responses against these novel MuV epitopes could be detected in recently vaccinated persons, corroborating earlier findings. Identifying which MuV epitopes are dominantly targeted in the mumps-specific CD8+ T- response is an important step towards better understanding in the discrepancies between natural infection or vaccination-induced cell-mediated immune protection.

Multicomponent Gold-Linked Glycoconjugate Vaccine Elicits Antigen-Specific Humoral and Mixed TH1-TH17 Immunity, Correlated with Increased Protection against Burkholderia pseudomallei.

ABSTRACTBurkholderia pseudomallei is the causative agent of melioidosis, a fatal disease with a high mortality rate. The intrinsic resistance to commonly used antibiotics combined with the complex bacterial life cycle has hampered the development of preventive and therapeutic interventions and vaccines. Furthermore, the need of humoral and cell-mediated immunity in protection against B. pseudomallei has complicated the development of effective vaccines. Antigen delivery vaccine platforms that promote humoral and cellular responses while maintaining a safe profile are a roadblock to developing subunit vaccines against intracellular pathogens. Gold nanoparticles (AuNPs) were used for the delivery of multicomponent antigens with the goal of inducing vaccine-mediated immunity, promoting protection against melioidosis disease. Different nanoglycoconjugates using predicted immunogenic protein candidates, Hcp1, FlgL, OpcP, OpcP1, OmpW, and hemagglutinin, were covalently coupled to AuNPs, together with the lipopolysaccharide (LPS) from Burkholderia thailandensis, which acted as an additional antigen. Animals immunized with individually coupled (AuNP-protein-LPS) formulations containing OpcP or OpcP1, together with CpG as an adjuvant, showed a significant increase in protection, whereas a nanovaccine combination (AuNP-Combo2-LPS) showed significant and complete protection against a lethal intranasal B. pseudomallei challenge. Animals immunized with AuNP-Combo2-LPS showed robust humoral antigen-specific (IgG and IgA) responses with higher IgG2c titer, indicating a TH1-skewed response and promotion of macrophage uptake. In addition, immunization with the nanovaccine combination resulted in a mixed antigen-specific TH1-TH17 cytokine profile after immunization. This study provides the basis for an elegant and refined multicomponent glycoconjugate vaccine formulation capable of eliciting both humoral and cell-mediated responses against lethal B. pseudomallei challenge.

Effector function prior to establishment of the phagosomal pathogen niche is required for protective CD4+ T cell-mediated immunity against Leishmania

Abstract Leishmania is an appealing model organism to study CD4+ T cell-mediated protective immunity against phagosomal pathogens which features localized primary and secondary infection sites with defined innate and adaptive responses. Upon secondary challenge of chronic L. major-infected C57Bl/6 mice, rapid CD4+T effector (TEFF) function via IFN-g-mediated activation of infected monocytes is associated with optimal immunity. However, the requirement for immediate effector function has yet to be demonstrated. Thus, we isolated time as a variable in the delivery of CD4+ TEFF effector function. We adoptively transferred (AT) chronic mouse-derived Ly6C+CD4+TEFFs into naïve recipients immediately (D0) or 4 days (D4) post-L. major challenge. In this time window Leishmania establishes an intracellular niche but does not proliferate. At day 21 post-challenge, D4 AT resulted in a total loss of the parasite control mediated by D0 transfer. To address whether parasite niche establishment modulated Th1 TEFF cell recruitment, we employed intravital imaging. Ag-sp T cells were present in the infected dermis at significantly lower numbers following D4 vs D0 transfer at 4 days post-T cell transfer, indicating a recruitment deficit. Rapid CD4+ Th1 effector function was required for circulating Th1 TEFF cells to capitalize on an early recruitment window associated with cxcl9 and cxcl10 expression and to prevent parasite niche establishment through altered cell recruitment, gene expression, and functional capacity of both innate and adaptive immune cells. Thus, acute TEFF cell availability is required to prevent host immunomodulation by Leishmania and is a key consideration for vaccination against phagosomal pathogens reliant on Th1 immunity.

Insights on the mechanisms of the protective immunity in the brain from the studies on infection with an intracellular microorganism, Toxoplasma gondii

The immune system operates the protection against infections by selecting efficient pathways depending on the pathogen. Toxoplasma gondii, an obligate intracellular protozoan parasite, has two lifecycle stages, tachyzoite and cyst, in intermediate hosts including humans. Tachyzoite is the acute stage form that quickly proliferates within host cells. Cyst is the chronic stage form that can slowly grow into more than 100 mm in diameter by containing hundreds to thousands of bradyzoites. Our studies on the IFN-g-mediated protective immunity against cerebral tachyzoite growth revealed that IFN-g production by brain-resident cells is not only required for upregulation of the innate protective immunity to limit cerebral tachyzoite proliferation during the early stage of the tachyzoite growth but also crucial for recruiting immune T cells from the periphery and activation of the recruited T cells to ultimately prevent the tachyzoite growth. Since IFN-g is crucial for the protective immunity against various intracellular microorganisms in the brain, it is possible that IFN-gproduced by brain-resident cells plays a key first line defense role by orchestrating both the innate and T cell-mediated protective immunity to control not only T. gondii but also the other intracellular pathogens. Our studies on the protective immunity against T. gondii cysts uncovered the capability of cytotoxic T cells to penetrate into the target in a perforin-dependent manner for its elimination. After penetrating into the target, the cytotoxic T cells secrete granzyme B, which associates with an accumulation of phagocytes to eliminate the parasite. Since the presence of tumor-infiltrating CD8+ T cells in solid cancers is an indicator of positive prognosis of cancer patients, the perforin-mediated penetration of CD8+ T cells and an accumulation of phagocytes could function as a powerful protective mechanism against not only T. gondiicysts but also targets of large mass in general such as solid cancers.

Cellular Immune Responses are Preserved and May Contribute to&amp;nbsp;Chadox1 ChAdOx1 nCoV-19&amp;nbsp;Vaccine Effectiveness Against Infection Due to SARS-CoV-2 B·1·617·2 Delta Variant Despite Reduced Virus Neutralisation

Background: The emergence of SARS-CoV-2 variants of concern (VoC) has threatened the effectiveness of vaccination due to decreased neutralisation ability of the vaccine generated antibodies. Our objective was to assess ChAdOx1 nCoV-19 vaccine effectiveness during the massive surge from 1st April to 31stMay 2021 predominantly due to the more infectious B·1·617·2 (Delta) in India. Methods: We conducted a test-negative case-control study to assess the effectiveness of ChAdOx1 nCoV-19 vaccine. Cases were RT-PCR positive for SARS-CoV-2 infection. In addition, we tested live virus neutralisation and cellular immune responses against VoC among healthy recipients of ChAdOx1 nCoV-19 vaccine. The outcomes were effectiveness of ChAdOx1 nCoV-19 against infection and severe coronavirus disease-19, virus neutralisation effectivity and T-cell responses against the VoC among healthy vaccine recipients. Findings: Of the 2766 cases of confirmed SARS-CoV-2 infection, 3·1% were fully vaccinated compared with 7·1% of the 2377 controls giving an adjusted OR of 0·37 (95%CI 0·28, 0·48); this translated to 63·1% (95%CI 51·5, 72·1) vaccine effectiveness against SARS-CoV-2 B·1·617·2 variant, seen in 90% of the infected population as confirmed by whole-genome virus sequencing. Full vaccination prevented moderate-severe COVID-19 in 81·5% (95%CI: 9·9, 99·0). The effectiveness of single-dose vaccine was 46·2% (95%CI: 31·6, 57·7) against infection but 79·2% (95%CI: 46·1, 94·0) in preventing moderate-severe Covid-19. Among healthy vaccinated persons, plasma live virus neutralisation was 2·5-6·8 fold lower against B·1·1·7, B·1·351, B·1·617·1 and B·1·617·2 being lowest against B·1·617·2. However, T-cell responses were preserved against the recombinant mutant receptor binding domain antigens suggesting cell-mediated immune protection. Interpretation: Despite significantly reduced virus neutralisation, the effectiveness of ChAdOx1 nCoV-19 vaccine was 63% against B·1·617·2 infection and 81·5% in preventing severe disease. Spike specific T cells responses against virus variants were maintained and might contribute to immune protection following vaccination. Funding Information: Department of Biotechnology, Government of India; Council for Scientific and Industrial Research, India; Fondation Botnar. Declaration of Interests: None to declare. Ethics Approval Statement: The studies were approved by the Institute Ethics Committees of the partnering institutions.

A pathway to cure chronic infection with Toxoplasma gondii through immunological intervention.

Toxoplasma gondii, an obligate intracellular protozoan parasite, can establish a chronic infection in the brain by forming tissue cysts. This chronic infection is widespread in humans worldwide including developed countries, with up to one third of the population being estimated to be infected with this parasite. Diagnosis of this chronic infection is usually conducted by serological detection of IgG antibodies against this parasite. Since infected individuals remain positive for these antibodies for years, it has generally been considered that this infection is a lifelong infection. It is also often considered that this chronic infection is "latent" or "quiescent". However, recent discovery of the capability of perforin-dependent, CD8+ T cell-mediated immune responses to eliminate T. gondii cysts in collaboration with phagocytes illustrated dynamic interplays between T. gondii cysts and host immune system during this chronic infection. Importantly, the cytotoxic T cell-mediated protective immunity is able to remove mature cysts of the parasite. It is now clear that chronic T. gondii infection is not "latent" or "quiescent". Elucidating the mechanisms of the dynamic host-pathogen interactions between the anti-cyst protective immunity and T. gondii cysts and identifying the pathway to appropriately activate anti-cyst CD8+ cytotoxic T cells would be able to open a door for eradicating T. gondii cysts and curing chronic infection with this parasite.

Cytokine saga in visceral leishmaniasis

In humans, infection with Leishmania manifests into a spectrum of diseases. The manifestation of the diseases depend on the resultant evasion of the parasite to immune responses namely by macrophages, which is an exclusive host of Leishmania. The B cells valiantly mount antibody responses, however, to no avail as the Leishmania parasites occupy the intracellular niches of the macrophages and subvert the immune response. Extensive studies have been documented on the role of cell-mediated immunity (CMI) in protection and counter survival strategies of the parasites leading to downregulation of CMI. The present review attempts to discuss the cytokines in progression or resolution of visceral form of leishmaniasis or kala-azar, predominantly affecting the Indian subcontinent. The components/cytokine(s) responsible for the regulation of the critical balance of T helper cells and their subsets have been discussed in the perspective.Therefore, any strategy involving the treatment of visceral leishmania (VL) needs to consider the balance and regulation of T cell function.

In situ neutrophil efferocytosis shapes T cell immunity to influenza infection.

Early recruitment of neutrophils from the blood to sites of tissue infection is a hallmark of innate immune responses. However, little is known about the mechanisms by which apoptotic neutrophils are cleared in infected tissues during resolution and the immunological consequences of in situ efferocytosis. Using intravital multiphoton microscopy, we show previously unrecognized motility patterns of interactions between neutrophils and tissue-resident phagocytes within the influenza-infected mouse airway. Newly infiltrated inflammatory monocytes become a chief pool of phagocytes and play a key role in the clearance of highly motile apoptotic neutrophils during the resolution phase. Apoptotic neutrophils further release epidermal growth factor and promote the differentiation of monocytes into tissue-resident antigen-presenting cells for activation of antiviral T cell effector functions. Collectively, these results suggest that the presence of in situ neutrophil resolution at the infected tissue is critical for optimal CD8+ T cell-mediated immune protection.

Secreted heat shock protein gp96-Ig vaccine induces malaria specific intrahepatic CD8 T cell responses

Abstract A highly-efficacious and durable malaria vaccine is an essential tool for global malaria eradication. One promising strategy to develop such a vaccine is to induce robust CD8+ T cell-mediated protective immunity against malaria liver stage parasites. We developed and tested a novel malaria vaccine platform based on the secreted form of the heat shock protein gp96 immunoglobulin, (gp96-Ig) to induce malaria antigen-specific liver resident memory CD8+ T cells. Gp96-Ig has ideal properties as an antigen carrier and vaccine adjuvant to activate antigen presenting cells (APCs) and effectively chaperone antigens for cross presentation via MHC I to CD8+ T lymphocytes. Our study shows that vaccination of mice and non-human primate (NHP) animal models with HEK-293 cells transfected with gp96-Ig and two well-known Plasmodium falciparum (Pf) vaccine candidate antigens, circumsporozoite protein (CSP) and apical membrane antigen 1 (AMA1), induce liver infiltrating, antigen-specific, cytotoxic memory CD8+ T cell responses. The majority of the CSP and AMA specific intrahepatic CD8+ T cells expressed CD69 and CXCR3, hallmarks of tissue resident memory T cells (TRM). Also, we found an increased frequency of intrahepatic CD8+ T cells secreting IL-2, which is relevant for maintenance of effective memory responses. Our findings are strongly supportive of a novel gp96-Ig-based malaria vaccine as a unique systemic and liver-homing, liver-stage antigen-specific CD8+ cytotoxic T lymphocyte (CTL) vaccine strategy.

Programming effective respiratory immunity to influenza with combination microparticle adjuvants

Abstract T cell-mediated immunity (CMI) can provide long-lived protection following parenteral immunization, but eliciting durable and protective CMI in the mucosa remains a significant challenge. Here, using polylactic-co-glycolic acid (PLGA)-based cationic pathogen-like particles (PLPs) for delivery of TLR agonists, we have investigated novel ways of presenting vaccine components to the immune system to simulate the potent innate immune stimulating effects of pathogens. We generated micro particle sized PLPs loaded with TLR4 (glucopyranosyl lipid adjuvant, GLA) and/or TLR9 (CpG) agonists, and formulated them with and without a mucosal delivery enhancing carbomer-based nano-emulsion adjuvant (ADJ). These adjuvants delivered intranasally to mice safely elicited robust and durable influenza nucleoprotein (NP)-specific CD8+/CD4+ effector and tissue-resident memory responses in lungs and airways. PLPs delivering TLR4 versus TLR9 agonists drove phenotypically and functionally distinct populations of effector and memory T cells. Following influenza virus challenge, functional and phenotypic attributes of effector T cells unique to the individual PLP formulation were associated with disparate levels of viral control in the respiratory tract. These studies demonstrate: (1) how adjuvant formulations affect effector/memory T cell differentiation in the lungs; (2) feasibility of using PLGA-based PLPs in vaccine formulations to elicit protective T cell immunity in the respiratory tract.

Selective Upregulation of Transcripts for Six Molecules Related to T Cell Costimulation and Phagocyte Recruitment and Activation among 734 Immunity-Related Genes in the Brain during Perforin-Dependent, CD8+ T Cell-Mediated Elimination of Toxoplasma gondii Cysts.

We recently found that an invasion of CD8+ cytotoxic T cells into tissue cysts of Toxoplasma gondii initiates an elimination of the cysts in association with an accumulation of microglia and macrophages. In the present study, we compared mRNA levels for 734 immune-related genes in the brains of infected SCID mice that received perforin-sufficient or -deficient CD8+ immune T cells at 3 weeks after infection. At 7 days after the T cell transfer, mRNA levels for only six genes were identified to be greater in the recipients of the perforin-sufficient T cells than in the recipients of the perforin-deficient T cells. These six molecules included two T cell costimulatory molecules, inducible T cell costimulator receptor (ICOS) and its ligand (ICOSL); two chemokine receptors, C-X-C motif chemokine receptor 3 (CXCR3) and CXCR6; and two molecules related to an activation of microglia and macrophages, interleukin 18 receptor 1 (IL-18R1) and chitinase-like 3 (Chil3). Consistently, a marked reduction of cyst numbers and upregulation of ICOS, CXCR3, CXCR6, IL-18R1, and Chil3 mRNA levels were also detected when the perforin-sufficient CD8+ immune T cells were transferred to infected SCID mice at 6 weeks after infection, indicating that the CD8+ T cell-mediated protective immunity is capable of eliminating mature T. gondii cysts. These results together suggest that ICOS-ICOSL interactions are crucial for activating CD8+ cytotoxic immune T cells to initiate the destruction of T. gondii cysts and that CXCR3, CXCR6, and IL-18R are involved in recruitment and activation of microglia and macrophages to the T cell-attacked cysts for their elimination.IMPORTANCE T. gondii establishes a chronic infection by forming tissue cysts, which can grow into sizes greater than 50 μm in diameter as a consequence of containing hundreds to thousands of organisms surrounded by the cyst wall within infected cells. Our recent studies using murine models uncovered that CD8+ cytotoxic T cells penetrate into the cysts in a perforin-dependent manner and induce their elimination, which is accompanied with an accumulation of phagocytic cells to the T cell-attacked target. This is the first evidence of the ability of the T cells to invade into a large target for its elimination. However, the mechanisms involved in anticyst immunity remain unclear. Immune profiling analyses of 734 immune-related genes in the present study provided a valuable foundation to initiate elucidating detailed molecular mechanisms of the novel effector function of the immune system operated by perforin-mediated invasion of CD8+ T cells into large targets for their elimination.