Can type-1 responses against intracellular pathogens be T helper 2 cytokine dependent?

Eugenia piauhiensis Vellaff. essential oil and γ-elemene its major constituent exhibit antileishmanial activity, promoting cell membrane damage and in vitro immunomodulation

Leishmaniasis is considered as one of the most Neglected Tropical Diseases (NTDs) in the world, caused by protozoan parasites of the genus Leishmania. Treatment of leishmaniasis by chemotherapy remains a challenge because of limited efficacy, toxic side effects, and drug resistance. The search for new therapeutic agents from natural sources has been a constant for the treatment of diseases such as leishmaniasis. The objective of this study was to evaluate the biological activity of Eugenia piauhiensis Vellaff. essential oil (EpEO) and its major constituent γ-elemene on promastigote and amastigote forms of Leishmania (Leishmania) amazonensis, its cytotoxicity, and possible mechanisms of action. EpEO was more active (IC₅₀ 6.43 ± 0.18 μg/mL) against promastigotes than γ-elemene [9.82 ± 0.15 μg/mL (48.05 ± 0.73 μM)] and the reference drug miltefosine [IC₅₀ 17.25 ± 0.26 μg/mL (42.32 ± 0.64 μM)]. EpEO and γ-elemene exhibited low cytotoxicity against J774.A1 macrophages, with CC₅₀ 225.8 ± 3.57 μg/mL and 213.21 ± 3.3 μg/mL (1043 ± 16.15 μM), respectively. Additionally, EpEO and γ-elemene present direct activity against the parasite, decreasing plasma membrane integrity. EpEO and γ-elemene also proved to be even more active against intracellular amastigotes of the parasite [IC₅₀ 4.59 ± 0.07 μg/mL and 8.06 ± 0.12 μg/mL (39.44 ± 0.59 μM)], respectively), presenting indirect effects through macrophage activity modulation. Anti-amastigote activity was associated with increased TNF-α, IL-12, NO, and ROS levels. In conclusion, our results suggest EpEO and γ-elemene as promising candidates for new drug development against leishmaniasis.

MicroRNA 155 Contributes to Host Immunity against Leishmania donovani but Is Not Essential for Resolution of Infection

CD4⁺ T helper 1 (Th1) cells producing interferon gamma (IFN-γ) are critical for the resolution of visceral leishmaniasis (VL). MicroRNA 155 (miR155) promotes CD4⁺ Th1 responses and IFN-γ production by targeting suppressor of cytokine signaling-1 (SOCS1) and Src homology-2 domain-containing inositol 5-phosphatase 1 (SHIP-1) and therefore could play a role in the resolution of VL. To determine the role of miR155 in VL, we monitored the course of Leishmania donovani infection in miR155 knockout (miR155KO) and wild-type (WT) C57BL/6 mice. miR155KO mice displayed significantly higher liver and spleen parasite loads than WT controls and showed impaired hepatic granuloma formation. However, parasite growth eventually declined in miR155KO mice, suggesting the induction of a compensatory miR155-independent antileishmanial pathway. Leishmania antigen-stimulated splenocytes from miR155KO mice produced significantly lower levels of Th1-associated IFN-γ than controls. Interestingly, at later time points, levels of Th2-associated interleukin-4 (IL-4) and IL-10 were also lower in miR155KO splenocyte supernatants than in WT mice. On the other hand, miR155KO mice displayed significantly higher levels of IFN-γ, iNOS, and TNF-α gene transcripts in their livers than WT mice, indicating that distinct organ-specific antiparasitic mechanisms were involved in control of L. donovani infection in miR155KO mice. Throughout the course of infection, organs of miR155KO mice showed significantly more PDL1-expressing Ly6C^hi inflammatory monocytes than WT mice. Conversely, blockade of Ly6C^hi inflammatory monocyte recruitment in miR155KO mice significantly reduced parasitic loads, indicating that these cells contributed to disease susceptibility. In conclusion, we found that miR155 contributes to the control of L. donovani but is not essential for infection resolution.

Protein biomarkers discriminate Leishmania major-infected and non-infected individuals in areas endemic for cutaneous leishmaniasis

Background

A successful host immune response to infection is dependent upon both innate and adaptive immune effector mechanisms. Cutaneous leishmaniasis results in an adaptive Th1 CD4⁺ T cell response that efficiently clears the parasite, but may also result in scaring. However the role of innate mechanisms during parasite clearance remains less well defined.

Methods

We examined a unique cohort of individuals, living in a Leishmania major endemic region, that were stratified among 3 distinct clinical groups in a cross-sectional study. Specifically, patients were classified either as healed (n = 17), asymptomatic (23), or naïve to infection (18) based upon the classical Leishmanin Skin Test (LST) and the presence or absence of scars. Utilizing a multiplexed immunoassay approach we characterized the induced cytokine and chemokine response to L. major.

Results

A subset of innate immune molecules was induced in all groups. By contrast, T cell-associated cytokines were largely induced in exposed groups as compared to L. major-infection naïve individuals. Two exceptions were IL-17A and IL-12p70, induced and not induced, respectively, in naïve individuals. In addition, GM-CSF was more strongly induced in healed patients as compared to the other two groups. Surprisingly an IL-13 response was the best cytokine for classifying previously infected donors.

Conclusions

Exploratory data analysis, utilizing principle component analysis (PCA), revealed distinct patient clusters of the healed and naïve groups based on the most differentially induced proteins. Asymptomatic previously infected individuals were more difficult to assign to a particular cluster based on these induced proteins. Analysis of these proteins may enable the identification of biomarkers associated with disease, leading to a better understanding of the protective mechanisms of immune response against leishmaniasis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-1458-6) contains supplementary material, which is available to authorized users.

IL-4 receptor-alpha-dependent control of Cryptococcus neoformans in the early phase of pulmonary infection

Cryptococcus neoformans is an opportunistic fungal pathogen that causes lung inflammation and meningoencephalitis in immunocompromised people. Previously we showed that mice succumb to intranasal infection by induction of pulmonary interleukin (IL)-4Rα-dependent type 2 immune responses, whereas IL-12-dependent type 1 responses confer resistance. In the experiments presented here, IL-4Rα⁻/⁻ mice unexpectedly show decreased fungal control early upon infection with C. neoformans, whereas wild-type mice are able to control fungal growth accompanied by enhanced macrophage and dendritic cell recruitment to the site of infection. Lower pulmonary recruitment of macrophages and dendritic cells in IL-4Rα⁻/⁻ mice is associated with reduced pulmonary expression of CCL2 and CCL20 chemokines. Moreover, IFN-γ and nitric oxide production are diminished in IL-4Rα⁻/⁻ mice compared to wild-type mice. To directly study the potential mechanism(s) responsible for reduced production of IFN-γ, conventional dendritic cells were stimulated with C. neoformans in the presence of IL-4 which results in increased IL-12 production and reduced IL-10 production. Together, a beneficial role of early IL-4Rα signaling is demonstrated in pulmonary cryptococcosis, which contrasts with the well-known IL-4Rα-mediated detrimental effects in the late phase.

Development of novel prime-boost strategies based on a tri-gene fusion recombinant L. tarentolae vaccine against experimental murine visceral leishmaniasis

Visceral leishmaniasis (VL) is a vector-borne disease affecting humans and domestic animals that constitutes a serious public health problem in many countries. Although many antigens have been examined so far as protein- or DNA-based vaccines, none of them conferred complete long-term protection. The use of the lizard non-pathogenic to humans Leishmania (L.) tarentolae species as a live vaccine vector to deliver specific Leishmania antigens is a recent approach that needs to be explored further. In this study, we evaluated the effectiveness of live vaccination in protecting BALB/c mice against L. infantum infection using prime-boost regimens, namely Live/Live and DNA/Live. As a live vaccine, we used recombinant L. tarentolae expressing the L. donovani A2 antigen along with cysteine proteinases (CPA and CPB without its unusual C-terminal extension (CPB^-CTE)) as a tri-fusion gene. For DNA priming, the tri-fusion gene was encoded in pcDNA formulated with cationic solid lipid nanoparticles (cSLN) acting as an adjuvant. At different time points post-challenge, parasite burden and histopathological changes as well as humoral and cellular immune responses were assessed. Our results showed that immunization with both prime-boost A2-CPA-CPB^-CTE-recombinant L. tarentolae protects BALB/c mice against L. infantum challenge. This protective immunity is associated with a Th1-type immune response due to high levels of IFN-γ production prior and after challenge and with lower levels of IL-10 production after challenge, leading to a significantly higher IFN-γ/IL-10 ratio compared to the control groups. Moreover, this immunization elicited high IgG1 and IgG2a humoral immune responses. Protection in mice was also correlated with a high nitric oxide production and low parasite burden. Altogether, these results indicate the promise of the A2-CPA-CPB^-CTE-recombinant L. tarentolae as a safe live vaccine candidate against VL.

Visceral leishmaniasis (VL) is the most severe form of leishmaniasis and has emerged as an opportunistic infection in HIV-1 infected patients in many parts of the world. Drug-resistant forms have developed so emergence and increased the need for advanced preventive strategies. Using live avirulent organisms as a vaccine has been proven to be more effective than other regimens. The lizard protozoan parasite Leishmania tarentolae is considered as nonpathogenic to humans. In our previous work, a recombinant L. tarentolae strain expressing the amastigote-specific L. donovani A2 antigen as a vaccine candidate elicited protection against L. infantum challenge in mice. Furthermore, combinations of CPA/CPB cysteine proteinases were more protective against visceral and cutaneous Leishmania infections than the individual forms. Herein, we used DNA/Live and Live/Live prime-boost vaccination strategies against visceral leishmaniasis in BALB/c mice consisting of the A2-CPA-CPB^-CTE tri-fusion genes formulated with cationic solid lipid nanoparticles and a recombinant L. tarentolae expressing the tri-fusion. Assessments of cytokine production, humoral responses, parasite burden and histopathological studies support that the recombinant L. tarentolae A2-CPA-CPB^-CTE candidate vaccine elicits a protective response against visceral leishmaniasis in mice and represents an important step forward in the development of new vaccine combinations against Leishmania infections.

Peroxisome Proliferator-Activated Receptor-γ-Mediated Polarization of Macrophages in Leishmania Infection

Infection is the outcome of a contest between a pathogen and its host. In the disease leishmaniasis, the causative protozoan parasites are harbored inside the macrophages. Leishmania species adapt strategies to make the infection chronic, keeping a balance between their own and the host's defense so as to establish an environment that is favorable for survival and propagation. Activation of peroxisome proliferator-activated receptor (PPAR) is one of the tactics used. This ligand-activated nuclear factor curbs inflammation to protect the host from excessive injuries by setting a limit to its destructive force. In this paper, we report the interaction of host PPARs and the pathogen for visceral leishmaniasis, Leishmania donovani, in vivo and in vitro. PPAR expression is induced by parasitic infection. Leishmanial activation of PPARγ promotes survival, whereas blockade of PPARγ facilitates removal of the parasite. Thus, Leishmania parasites harness PPARγ to increase infectivity.

Interleukin-13 reduces hyperalgesia and the level of interleukin-1β in BALB/c mice infected with Leishmania major with an up-regulation of interleukin-6

The anti-inflammatory cytokines interleukin-10 (IL-10) and interleukin-13 (IL-13) were shown to reduce hyperalgesia in some models such as rats exposed to UV rays. In addition, IL-10 was also shown to reduce hyperalgesia in high dose of Leishmania major-induced inflammation in BALB/c mice accompanied by a significant decrease in the levels of interleukin-1β (IL-1β) in the paws of infected mice, while no effect on the levels of IL-6 was observed. In this study, we injected BALB/c mice with a high dose of L. major and treated them with IL-13 (15 ng/animal) for twelve days (excluding the weekends) and hyperalgesia was assessed using thermal pain tests. Furthermore, the levels of IL-1β and IL-6 were also assessed at different post-infection days. Our results show that IL-6 and more importantly IL-1β don't play a direct role in the L. major-induced hyperalgesia and that IL-13 induces this hyperalgesia through the down-regulation of IL-1β and another proinflammatory cytokine (most probably TNF-α). Furthermore, our data show that IL-13 leads to the upregulation of the level IL-6 which initially seems to have no direct role in the induced hyperalgesia. Therefore, we suggest that the L. major-induced hyperalgesia is mainly mediated by the cytokine cascade leading to the production of sympathetic amines.

Human CD141+ (BDCA-3)+ dendritic cells (DCs) represent a unique myeloid DC subset that cross-presents necrotic cell antigens

The characterization of human dendritic cell (DC) subsets is essential for the design of new vaccines. We report the first detailed functional analysis of the human CD141⁺ DC subset. CD141⁺ DCs are found in human lymph nodes, bone marrow, tonsil, and blood, and the latter proved to be the best source of highly purified cells for functional analysis. They are characterized by high expression of toll-like receptor 3, production of IL-12p70 and IFN-β, and superior capacity to induce T helper 1 cell responses, when compared with the more commonly studied CD1c⁺ DC subset. Polyinosine-polycytidylic acid (poly I:C)–activated CD141⁺ DCs have a superior capacity to cross-present soluble protein antigen (Ag) to CD8⁺ cytotoxic T lymphocytes than poly I:C–activated CD1c⁺ DCs. Importantly, CD141⁺ DCs, but not CD1c⁺ DCs, were endowed with the capacity to cross-present viral Ag after their uptake of necrotic virus-infected cells. These findings establish the CD141⁺ DC subset as an important functionally distinct human DC subtype with characteristics similar to those of the mouse CD8α⁺ DC subset. The data demonstrate a role for CD141⁺ DCs in the induction of cytotoxic T lymphocyte responses and suggest that they may be the most relevant targets for vaccination against cancers, viruses, and other pathogens.

In vitro cytokine responses of peripheral blood mononuclear cells from healthy dogs to distemper virus, Malassezia and Toxocara

Naïve CD4+ T cells may differentiate into a number of subsets including T helper 1 (Th1) Th2, Th3, Th17 and T regulatory (Treg) cells depending on the type of antigen they encounter. These CD4+ families have been defined based on the array of cytokines they produce and the effects they have on adaptive immune responses. CD4+ subsets are cross regulatory and at times cooperative. The study of these adaptive immune modulators has revealed the important role that cytokines play in mounting effective as well as detrimental immune responses to pathogens. Examining the cytokine responses of lymphocytes in culture can provide important understanding of how immune responses to pathogens are orchestrated. For this purpose the in vitro cytokine production of peripheral blood mononuclear cells (PBMC) from healthy dogs was examined in response to stimulation with antigens from a common canine virus (canine distemper virus, CDV), a commensal skin yeast of dogs (Malassezia pachydermatis) and a common canine helminth (Toxocara canis (T. canis)). Cell culture supernatants were removed from antigen stimulated and unstimulated control PBMC after 4, 24, 48 and 72 h and the concentration of Th1 type cytokines (IL-2, IFN-gamma, TNF-alpha) and Th2 type cytokines (IL-4, IL-5, IL-10) was determined using sandwich ELISA assays. CDV induced low levels of cytokine production initially with a predominance of IL-10 at 24h and a balanced response at 48 h of incubation. Malassezia antigen stimulated an early type 2 cytokine response with dramatic production of IL-4 at 24h of incubation compared to the other stimulants examined. By 48 h of incubation, however, the cytokine mix in response to Malassezia had also moved toward a Th1 type response. T. canis induced early production of Th2 type cytokines with IL-5 predominating; however, with longer incubation (48-72 h) there was a switch to a balanced Th1/Th2 response. In conclusion, the cytokines produced in vitro by canine PBMC in response to prototypical Th1 and Th2 type pathogens were not clearly polarized and shifted over time. While the in vitro study of PBMC cytokine responses cannot be directly extrapolated to in vivo responses to the same antigens, the results do highlight the dynamic and fluctuating nature of cytokine production.