Dengue virus (DENV) infection in the presence of reactive, non-neutralizing immunoglobulin G (IgG) (RNNIg) is the greatest risk factor for dengue hemorrhagic fever (DHF) or dengue shock syndrome ...(DSS). Progression to DHF/DSS is attributed to antibody-dependent enhancement (ADE); however, because only a fraction of infections occurring in the presence of RNNIg advance to DHF/DSS, the presence of RNNIg alone cannot account for disease severity. We discovered that DHF/DSS patients respond to infection by producing IgGs with enhanced affinity for the activating Fc receptor FcγRIIIA due to afucosylated Fc glycans and IgG1 subclass. RNNIg enriched for afucosylated IgG1 triggered platelet reduction in vivo and was a significant risk factor for thrombocytopenia. Thus, therapeutics and vaccines restricting production of afucosylated, IgG1 RNNIg during infection may prevent ADE of DENV disease.
NKT cells play an important role in autoimmune diseases, tumor surveillance, and infectious diseases, providing in most cases protection against infection. NKT cells are reactive to CD1d presented ...glycolipid antigens. They can modulate immune responses by promoting the secretion of type 1, type 2, or immune regulatory cytokines. Pathogen-derived signals to dendritic cells mediated via Toll like Receptors (TLR) can be modulated by activated invariant Natural Killer T (iNKT) cells. The terminal β-(1-4)-galactose residues of glycans can modulate host responsiveness in a T helper type-1 direction via IFN-γ and TLRs. We have attempted to develop a defined immunotherapeutic, based on the cooperative action of a TLR ligand and iNKT cell using a mouse model of visceral leishmaniasis. We evaluated the anti-Leishmania immune responses and the protective efficacy of the β-(1-4)-galactose terminal NKT cell ligand glycosphingophospholipid (GSPL) antigen of L. donovani parasites. Our results suggest that TLR4 can function as an upstream sensor for GSPL and provoke intracellular inflammatory signaling necessary for parasite killing. Treatment with GSPL was able to induce a strong effective T cell response that contributed to effective control of acute parasite burden and led to undetectable parasite persistence in the infected animals. These studies for the first time demonstrate the interactions between a TLR ligand and iNKT cell activation in visceral leishmaniasis immunotherapeutic.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
•More than eighty percent adults immune to at least one dengue serotype.•More than half of them are immune to all four dengue serotypes.•Substantial interindividual variation observed in MBC, ...neutralizing/binding antibodies levels.•Presence of the neutralizing antibodies correlate with presence of binding antibodies, but not vice versa.•Levels of neutralizing and binding antibodies are not in perfect correlation.
The Indian population is facing highest dengue burden worldwide supporting an urgent need for vaccines. For vaccine introduction, evaluation and interpretation it is important to gain a critical understanding of immune memory induced by natural exposure. However, immune memory to dengue remains poorly characterized in this region.
We enumerated levels of dengue specific memory B cells (MBC), neutralizing (NT) and binding antibodies in healthy adults (n=70) from New Delhi.
NT-antibodies, binding antibodies and MBC were detectable in 86%, 86.56% and 81.63% of the subjects respectively. Among the neutralizing positive subjects, 58%, 27%, 5% and 10% neutralized all four, any three, any two and any one dengue serotypes respectively. The presence of the neutralizing antibodies was associated with the presence of the MBC and binding antibodies. However, a massive interindividual variation was observed in the levels of the neutralizing antibodies (range, <1:50–1:30,264), binding antibodies (range, 1:3,000–1:134,000,) as well as the MBC (range=0.006%–5.05%).
These results indicate that a vast majority of the adults are immune to multiple dengue serotypes and show massive interindividual variation in neutralizing/binding antibodies and MBCs – emphasizing the importance of monitoring multiple parameters of immune memory in order to properly plan, evaluate and interpret dengue vaccines.
Objectives
The aim of this study was to investigate and characterize the efficacy of asiaticoside in an experimental model of visceral leishmaniasis caused by antimony-susceptible (AG83) and ...-resistant (GE1F8R and K39) Leishmania donovani.
Methods
The effect of asiaticoside was evaluated by microscopic counting of intracellular amastigotes in cultured macrophages stained with Giemsa. The antileishmanial effect of the compounds was assessed in infected BALB/c mice by estimation of splenic and liver parasite burdens in Leishman Donovan units. Cytokines were measured by real-time PCR and ELISA. Intracellular tumour necrosis factor-α (TNF-α) was measured by fluorescence-activated cell sorting. Nitric oxide was measured by the Griess reaction.
Results
Besides effectively inhibiting in vitro replication of the parasite within macrophages, asiaticoside treatment resulted in almost complete clearance of the liver and splenic parasite burden when administered at a dose of 5 mg/kg × 10 starting on day +30 of challenge with antimony-susceptible (AG83) and -resistant (GE1F8R and K39) L. donovani. Asiaticoside treatment was associated with a switch in the host from a Th2- to a Th1-type immune response accompanied by the induction of TNF-α-mediated nitric oxide production, all of which are important elements for macrophage function in antileishmanial defence mechanisms.
Conclusions
These results suggest that oral therapy with asiaticoside shows promising antileishmanial efficacy in animals infected by antimony-susceptible (AG83) and -resistant (GE1F8R and K39) L. donovani.
Pattern recognition receptors (PRR) sense certain molecular patterns uniquely expressed by pathogens. Retinoic-acid-inducible gene I (RIG-I) is a cytosolic PRR that senses viral nucleic acids and ...induces innate immune activation and secretion of type I interferons (IFNs). Here, using influenza vaccine antigens, we investigated the consequences of activating the RIG-I pathway for antigen-specific adaptive immune responses. We found that mice immunized with influenza vaccine antigens coadministered with 5'ppp-double-stranded RNA (dsRNA), a RIG-I ligand, developed robust levels of hemagglutination-inhibiting antibodies, enhanced germinal center reaction, and T follicular helper cell responses. In addition, RIG-I activation enhanced antibody affinity maturation and plasma cell responses in the draining lymph nodes, spleen, and bone marrow and conferred protective immunity against virus challenge. Importantly, activation of the RIG-I pathway was able to reduce the antigen requirement by 10- to 100-fold in inducing optimal influenza-specific cellular and humoral responses, including protective immunity. The effects induced by 5'ppp-dsRNA were significantly dependent on type I IFN and IPS-1 (an adapter protein downstream of the RIG-I pathway) signaling but were independent of the MyD88- and TLR3-mediated pathways. Our results show that activation of the RIG-I-like receptor pathway programs the innate immunity to achieve qualitatively and quantitatively enhanced protective cellular adaptive immune responses even at low antigen doses, and this indicates the potential utility of RIG-I ligands as molecular adjuvants for viral vaccines.
The recently discovered RNA helicase family of RIG-I-like receptors (RLRs) is a critical component of host defense mechanisms responsible for detecting viruses and triggering innate antiviral cytokines that help control viral replication and dissemination. In this study, we show that the RLR pathway can be effectively exploited to enhance adaptive immunity and protective immune memory against viral infection. Our results show that activation of the RIG-I pathway along with influenza vaccination programs the innate immunity to induce qualitatively and quantitatively superior protective adaptive immunity against pandemic influenza viruses. More importantly, RIG-I activation at the time of vaccination allows induction of robust adaptive responses even at low vaccine antigen doses. These results highlight the potential utility of exploiting the RIG-I pathway to enhance viral-vaccine-specific immunity and have broader implications for designing better vaccines in general.
Dengue is a global epidemic causing over 100 million cases annually. The clinical symptoms range from mild fever to severe hemorrhage and shock, including some fatalities. The current paradigm is ...that these severe dengue cases occur mostly during secondary infections due to antibody-dependent enhancement after infection with a different dengue virus serotype. India has the highest dengue burden worldwide, but little is known about disease severity and its association with primary and secondary dengue infections. To address this issue, we examined 619 children with febrile dengue-confirmed infection from three hospitals in different regions of India. We classified primary and secondary infections based on IgM:IgG ratios using a dengue-specific enzyme-linked immunosorbent assay according to the World Health Organization guidelines. We found that primary dengue infections accounted for more than half of total clinical cases (344 of 619), severe dengue cases (112 of 202) and fatalities (5 of 7). Consistent with the classification based on binding antibody data, dengue neutralizing antibody titers were also significantly lower in primary infections compared to secondary infections (P ≤ 0.0001). Our findings question the currently widely held belief that severe dengue is associated predominantly with secondary infections and emphasizes the importance of developing vaccines or treatments to protect dengue-naive populations.
Several co-pathogens that pose threats to the fetus during gestation, including human cytomegalovirus (HCMV), may also contribute to mother-to-child transmission (MTCT) of human immunodeficiency ...virus type 1 (HIV-1). Within endemic settings, associations between maternal HCMV viral load and increased incidence of MTCT of HIV-1 are documented; however, the mechanisms that promote transmission are poorly characterized. Here we demonstrate that HCMV coinfection enhances susceptibility and viral replication of HIV-1 in placental macrophages (Hofbauer cells) in vitro. Consistent with enhanced viral susceptibility, HCMV exposure upregulates CCR5 and CD80 expression on Hofbauer cells. HCMV also significantly induces type I interferon (IFN), proinflammatory cytokines, and antiviral gene expression. Interestingly, we found that HCMV diminishes type I IFN-mediated phosphorylation of STAT2. Collectively, our data suggest that HCMV-induced activation, local inflammation, and antagonism of type I IFN responses in placental Hofbauer cells promote in utero transmission of HIV-1.
Compared with cutaneous leishmaniasis, vaccination against visceral leishmaniasis has received limited attention. Most available drugs are toxic, and relapse after cure remains a chronic problem. ...Growing limitations in available chemotherapeutic strategies due to emerging resistant strains and lack of an effective vaccine strategy against visceral leishmaniasis deepens the crisis. Complete soluble antigen (CSA), from a β1-4 galactosyltransferase expressing attenuated Leishmania donovani parasite, induced protection against subsequent challenge and during active infections. CSA immunization was effective against both pentavalent antimony sensitive and resistant strains of L. donovani. Majority (~85%) of the immunized animals showed sterile protection. Resolution of the disease required the presence of T cells, and the recovered animals remained immune to re-challenge. Control of the parasites was dependent on type 1 CD4⁺ helper cells, which evolved in the presence of IL-12 and activated macrophages through the production of IFN-γ. Immunity was adoptively transferable and was dependent on both CD4⁺ and CD8⁺ cells. CSA immunization led to enhanced IFN-γ production, while suppressing the IL-10 production. However, CSA immunization did not abrogate IL-4 production. Our results accentuate the need to establish a favorable cellular immunity while intervening with the development of Th2 cells during leishmania infection.
In vitro and in vivo anti-leishmanial efficacy of copper salisylaldoxime (CuSAL), a transition metal complex, was evaluated and the underlying mechanism was studied. In vitro studies revealed that ...30 μM of CuSAL causes 96% reduction in parasite burden in infected macrophages. CuSAL is least toxic in host cells. A dose of 5 mg/kg bodyweight per mice on alternate days (5 doses) gives ∼97% protection in both liver and spleen. Moreover, CuSAL potentially inhibits the catalytic activity of LdTOPILS and causes apoptosis of Leishmania parasites through induction of intracellular ROS generation and activation of caspase-like proteases. Interestingly, CuSAL does not inhibit the catalytic activity of human topoisomerase I. The present study illuminated that CuSAL, has potent anti-leishmanial activity, which selectively targets LdTOPILS; and is a safe for human. Therefore, this compound might be highly promising candidate to develop the rational approaches for chemotherapy of human leishmaniasis.
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•Copper salisylaldoxime (CuSAL) shows potent anti-leishmanial activity.•CuSAL selectively inhibits the catalytic activity of L. donovani Topoisomerase I (LdTOPILS) leading to apoptosis.•CuSAL does not inhibit the host topoisomerase I (human Topoisomerase I).
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