Monophosphoryl Lipid A Based Cationic Liposome Facilitates Vaccine Induced Expansion of Polyfunctional T Cell Immune Responses against Visceral Leishmaniasis

A new chimeric protein composed by T-cell epitopes from peroxidoxin and pyridoxal kinase proteins is protective against visceral leishmaniasis

Visceral leishmaniasis (VL) is a neglected tropical disease caused by intracellular protozoan parasites, and which present high incidence in populations in the world. The diagnosis is difficult to be performed, and treatment is toxic and/or presents high cost. In this context, prophylactic vaccination could help as an effective control measure against the disease. In this study, a new chimeric protein (LAV) was constructed with immunogenic T-cell epitopes from two immunogenic Leishmania proteins, and it was evaluated to protects BALB/c mice against Leishmania infantum infection. For this, animals were vaccinated with rLAV associated with micelles (Mic) or monophosphoryl lipid A (MPLA) as adjuvants; while the others received saline, rLAV, Mic or MPLA as controls. Results showed that the rLAV/Mic and rLAV/MPLA combinations induced higher cell proliferation indexes in stimulated cell cultures after infection, as well as the development of a polarized Th1-type cellular and humoral response before and after infection, which was based on the production of IFN-γ, IL-12, TNF-α, nitrite, and IgG2a isotype antibodies. In addition, both CD4+ and CD8+ T-cell subtypes were important for the IFN- secretion in both groups, as compared to the others. Control groups mice produced significantly higher levels of IL-4, IL-10 and anti-parasite IgG1 antibodies, suggesting the occurrence of a Th2-type immune profile in these unprotected animals. The parasite load was found to be significantly lower in mice vaccinated with rLAV/MPLA or rLAV/Mic, as compared to the others, by using a limiting dilution assay and qPCR. In conclusion, data suggest that rLAV plus adjuvant could be considered as a vaccine candidate in future studies to protect against VL.

Nanovaccines: Merits, and diverse roles in boosting antitumor immune responses

An attractive type of cancer immunotherapy is cancer therapeutic vaccines that induce antitumor immunity effectively. Although supportive results in the recent vaccine studies, there are still numerous drawbacks, such as poor stability, weak immunogenicity and strong toxicity, to be tackled for promoting the potency and durability of antitumor efficacy. NPs (Nanoparticles)-based vaccines offer unique opportunities to breakthrough the current bottleneck. As a rule, nanovaccines are new the generations of vaccines that use NPs as carriers and/or adjuvants. Several advantages of nanovaccines are constantly explored, including optimal nanometer size, high stability, plenty of antigen loading, enhanced immunogenicity, tunable antigen presentation, more retention in lymph nodes and promote patient compliance by a lower frequency of dosing. Here, we summarized the merits and highlight the diverse role nanovaccines play in improving antitumor responses.

The Pathogenicity and Virulence of Leishmania - interplay of virulence factors with host defenses

Leishmaniasis is a group of disease caused by the intracellular protozoan parasite of the genus Leishmania. Infection by different species of Leishmania results in various host immune responses, which usually lead to parasite clearance and may also contribute to pathogenesis and, hence, increasing the complexity of the disease. Interestingly, the parasite tends to reside within the unfriendly environment of the macrophages and has evolved various survival strategies to evade or modulate host immune defense. This can be attributed to the array of virulence factors of the vicious parasite, which target important host functioning and machineries. This review encompasses a holistic overview of leishmanial virulence factors, their role in assisting parasite-mediated evasion of host defense weaponries, and modulating epigenetic landscapes of host immune regulatory genes. Furthermore, the review also discusses the diagnostic potential of various leishmanial virulence factors and the advent of immunomodulators as futuristic antileishmanial drug therapy.

Controlled rate slow freezing with lyoprotective agent to retain the integrity of lipid nanovesicles during lyophilization

We designed a novel lyophilization method using controlled rate slow freezing (CSF) with lyoprotective agent (LPA) to achieve intact lipid nanovesicles after lyophilization. During the freezing step, LPA prevented water supercooling, and the freezing rate was controlled by CSF. Regulating the freezing rate by various liquid media was a crucial determinant of membrane disruption, and isopropanol (freezing rate of 0.933 °C/min) was the optimal medium for the CSF system. Lyophilized lipid nanovesicle using both CSF and LPA retained 92.9% of the core material and had uniform size distributions (Z-average diameter = 133.4 nm, polydispersity index = 0.144), similar to intact vesicles (120.7 nm and 0.159, respectively), after rehydration. Only lyophilized lipid nanovesicle using both CSF and LPA showed no changes in membrane fluidity and polarity. This lyophilization method can be applied to improve storage stability of lipid nanocarriers encapsulating drugs while retaining their original activity.

HO-3867 Induces ROS-Dependent Stress Response and Apoptotic Cell Death in Leishmania donovani

Lack of vaccine and increasing chemotherapeutic toxicities currently necessitate the development of effective and safe drugs against various forms of leishmaniases. We characterized the cellular stress induced by a novel curcumin analogue, HO-3867, encapsulated within the phosphatidylcholine-stearylamine (PC-SA) liposome for the first time against Leishmania. The liposomal formulation of HO-3867 (i.e., PC-SA/HO-3867) initiated oxidative stress-induced apoptosis in L. donovani, revealed by altered cell morphology, phosphatidylserine externalization, mitochondrial depolarization, intracellular lipid accumulation, and cell cycle arrest in promastigotes. Liposomal HO-3867 was observed to be a strong apoptosis inducer in L. donovani and L. major in a dose-dependent manner, yet completely safe for normal murine macrophages. Moreover, PC-SA/HO-3867 treatment induced L. donovani metacaspase and PARP1 activation along with downregulation of the Sir2 gene. PC-SA/HO-3867 arrested intracellular L. donovani amastigote burden in vitro, with reactive oxygen species (ROS) and nitric oxide (NO)-mediated parasite killing. These data suggest that liposomal HO-3867 represents a highly promising and non-toxic nanoparticle-based therapeutic platform against leishmaniasis inspiring further preclinical developments.

Nanovaccine: an emerging strategy

INTRODUCTION

Vaccination is so far the most effective way of eradicating infections. Rapidly emerging drug resistance against infectious diseases and chemotherapy-related toxicities in cancer warrant immediate vaccine development to save mankind. Subunit vaccines alone, however, fail to elicit sufficiently strong and long-lasting protective immunity against deadly pathogens. Nanoparticle (NP)-based delivery vehicles like microemulsions, liposomes, virosomes, nanogels, micelles and dendrimers offer promising strategies to overcome limitations of traditional vaccine adjuvants. Nanovaccines can improve targeted delivery, antigen presentation, stimulation of body's innate immunity, strong T cell response combined with safety to combat infectious diseases and cancers. Further, nanovaccines can be highly beneficial to generate effective immutherapeutic formulations against cancer.

AREAS COVERED

This review summarizes the emerging nanoparticle strategies highlighting their success and challenges in preclinical and clinical trials in infectious diseases and cancer. It provides a concise overview of current nanoparticle-based vaccines, their adjuvant potential and their cellular delivery mechanisms.

EXPERT OPINION

The nanovaccines (50-250 nm in size) are most efficient in terms of tissue targeting, prolonged circulation and preferential uptake by the professional APCs chiefly due to their small size. More rational designing, improved antigen loading, extensive functionalization and targeted delivery are some of the future goals of ideal nanovaccines.

Biomimetic polymeric nanoparticle-based photodynamic immunotherapy and protection against tumor rechallenge

In this study, we sought to design a bionanomaterial that could exert anticancer effects against primary tumors and protect against rechallenged tumorsviaphotodynamic immunotherapy.