LaSap vaccine: Immunotherapy and immunochemotherapy associated with allopurinol in dogs naturally infected with Leishmania infantum.

Canine visceral leishmaniasis is a parasitic zoonosis that has a profound impact on public health in countries where it is endemic. Chemotherapeutic treatments cannot keep dogs stable for long periods, and the risk of generating parasitic resistance must be considered. Forty-four symptomatic and naturally infected dogs with Leishmania infantum were tested with two treatment protocols (i) immunotherapy with LaSap vaccine and (ii) immunochemotherapy with LaSap vaccine plus allopurinol. At 90 days after the end of the treatment, it was verified that, although both protocols had generated significant clinical improvements with a greater production of IFN-γ/IL-10, in relation to the parasite load, mainly in the skin, the dogs treated only with immunotherapy maintained the same profile. These results indicate that LaSap is a good strategy to control dog parasitism.

Infection in asymptomatic carriers of SARS-CoV-2 can interfere with the achievement of robust immunity on a population scale.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to spread worldwide as a severe pandemic, and a significant portion of the infected population may remain asymptomatic. Given this, five surveys were carried out between May and September 2020 with a total of 3585 volunteers in the municipality of Foz do Iguaçu, State of Paraná, a triple border region between Brazil/Argentina/Paraguay. Five months after the first infection, volunteers were re-analysed for the production of IgG anti-Spike and anti-RBD-Spike, in addition to analyses of cellular immunity. Seroconversion rates ranged from 4.4 % to a peak of 37.21 % followed by a reduction in seroconversion to 21.1 % in September, indicating that 25 % of the population lost their circulating anti-SARS-CoV-2 antibodies 3 months after infection. Analyses after 5 months of infection showed that only 17.2 % of people still had anti-RBD-Spike antibodies, however, most volunteers had some degree of cellular immune response. The strategy of letting people become naturally infected with SARS-CoV-2 to achieve herd immunity is flawed, and the first contact with the virus may not generate enough immunogenic stimulus to prevent a possible second infection.

Immunogenicity of HLA-DR1 and HLA-A2 peptides derived from Leishmania major Gp63 in golden hamsters.

AIMS: This study aimed to evaluate the toxicity and humoral and cellular immune response of three heterologous vaccines against Leishmania infantum, yet containing synthetic peptides from Leishmania major in the experimental model in hamsters. METHODS AND RESULTS: Through bioinformatics analyses, two Leishmania major Gp63 peptides were predicted and selected for vaccine formulations. Hamsters were divided into four groups, with each group receiving doses of three vaccine formulations containing HLA-DR1 or HLA-A2 peptides plus MontanideTM or both associated with the adjuvant. The animals received three vaccine doses and were evaluated for toxicity after each dose, in addition to being analysed for the production of antibodies and lymphoproliferation on day 211 after the last vaccine dose. Peptides predicted in association with oily adjuvant induced a humoral response and strong lymphoproliferation to Leishmania infantum antigen-specific stimulation.

One-year timeline kinetics of cytokine-mediated cellular immunity in dogs vaccinated against visceral leishmaniasis.

BACKGROUND: The main control strategy for visceral leishmaniasis in Brazil has been based on the elimination of seropositive dogs, although this is not widely accepted. In this context, the use of a long-lasting protective vaccine against canine visceral leishmaniasis (CVL) has been highly expected. The aim of this work was to determine the timeline kinetics of the cytokine microenvironment derived from circulating leukocytes as supportive immunological biomarkers triggered by Leishmune® vaccine. Cross-sectional kinetic analysis of cellular immunity cytokines was carried out at three times (1, 6 and 12 months) after primovaccination with Leishmune®. In vitro short-term whole blood cultures were stimulated with Leishmania infantum soluble antigen (SLAg). The secreted cytokine signatures and their major sources were determined. RESULTS: At six months after vaccination, Leishmune® induced an increase in IL-8, IFN-γ, IL-17a and TNF-α levels and a decrease in IL-10. Cytokine signature analysis revealed a shift in the microenvironment towards a pro-inflammatory profile mediated by IL-8 and IFN-γ. Both, CD4(+) (↑TNF-α(+) and ↑IFN-γ (+)) and CD8(+) (↑IL-17a and ↓IL-4) T-cells contributed to the acquired immune responses observed after stimulation with SLAg. CONCLUSIONS: The changes observed in the cytokine profile suggested that Leishmune® was able to induce an effective response at six months after primovaccination. After one year, it returned to baseline suggesting the need of additional boosting.

Cross-sectional spatial and epidemiological analysis of canine visceral leishmaniasis cases in the triple border region, Brazil, Argentina and Paraguay, between 2015 and 2020.

Visceral Leishmaniasis is one of the most important vector-borne zoonoses in the world. In 2013, the first autochthonous canine case of the disease in the state of Paraná, southern region of Brazil, was reported in Foz do Iguaçu, on the triple border between Brazil, Argentina and Paraguay. In 2015, the first human case was related. Once the endemic was confirmed, the Zoonoses Control Center (ZCC), an agency of the Municipal Health Department, started actions to implement the Human Visceral Leishmaniasis (HVL) Surveillance and Control Program (VLSCP), of the Ministry of Health. Between 2015 and 2020, 12,205 dog samples were analyzed for the diagnosis of the disease. A prevalence of 37.94% (4,630 samples) was found: 2016 had the highest prevalence, with 46.25%, and the year with the lowest prevalence was 2020, with 25.98%. Possible risk factors for dogs were analyzed, and the results obtained were: whether the request for the exam was performed by the ZCC was a significant protective factor, with a lower prevalence (37.5%) than dogs coming from private clinics (OR = 0.89, p-value = 0.016). Males were significantly more infected than females, with 41.1% and 35.7% positivity, respectively (OR = 1.24, p < 0.0001). Companion dogs and mixed breed dogs were significantly less affected than the other groups tested (OR = 0.44, p < 0.001; OR = 0.79, p = 0.012, respectively). The dogs' dark coat color was a significant risk factor with respect to the other color categories. Short and medium coat sizes were significantly considered risk factors, with 41.3% and 31.3% positivity. Long-haired dogs had only 22.7% positivity. In univariate analyses, giant, large and medium dogs were significantly more affected than small dogs. Dogs up to four years of age were significantly less affected than those in other age groups. There was a coincidence of human and canine cases in the spatial distribution. However, according to the literature, a higher incidence would be expected in humans, due to the high prevalence found in dogs. Therefore, further studies should be carried out to understand the dynamics of the disease in this region.

Bivalent Vaccine against Streptococcus agalactiae and Aeromonas hydrophila in Nile Tilapia (Oreochromis niloticus): A Laboratory-Phase and Large-Scale Study.

One of the main factors limiting tilapia's production is the occurrence of infections caused by Aeromonas and Streptococcus species. This work intended to evaluate a bivalent vaccine against A. hydrophila and S. agalactiae by intraperitoneal (i.p) administration in Nile tilapia (Oreochromis niloticus) in Brazil. The study was carried out in two phases: one in the laboratory, on a small scale, and from the results obtained, the study was expanded to a large scale in a production system in cages. The vaccine proved to be safe and effective in laboratory tests, with a vaccine efficacy (VE) of 93.66%. However, in large-scale tests with 12,000 tilapias, the VE was 59.14%, with a better food conversion ratio (1.54 kg) in the vaccinated group compared to the control group (1.27 kg). These results corroborate the efficiency of this tested vaccine; however, they indicate the need for field tests to attest to real protection.

Polymeric Delivery Systems as a Potential Vaccine against Visceral Leishmaniasis: Formulation Development and Immunogenicity.

Recent studies suggest that the association of antigens in microparticles increases the anti-Leishmania vaccine immunogenicity. This study aims to investigate the in situ effect of the adjuvant performance consisting of chitosan-coated poly(D,L-lactic) acid submicrometric particles (SMP) and analyze the inflammatory profile and toxicity. Two formulations were selected, SMP1, containing poly(D,L-lactide) (PLA) 1% wt/v and chitosan 1% wt/v; and SMP2, containing PLA 5% wt/v and chitosan 5% wt/v. After a single dose of the unloaded SMP1 or SMP2 in mice, the SMPs promoted cell recruitment without tissue damage. In addition, besides the myeloperoxidase (MPO) activity having demonstrated similar results among the analyzed groups, a progressive reduction in the levels of N-acetyl-ß-D-glucosaminidase (NAG) until 72 h was observed for SMPs. While IL-6 levels were similar among all the analyzed groups along the kinetics, only the SMPs groups had detectable levels of TNF-α. Additionally, the Leishmania braziliensis antigen was encapsulated in SMPs (SMP1Ag and SMP2Ag), and mice were vaccinated with three doses. The immunogenicity analysis by flow cytometry demonstrated a reduction in NK (CD3-CD49+) cells in all the SMPs groups, in addition to impairment in the T cells subsets (CD3+CD4+) and CD3+CD8+) and B cells (CD19+) of the SMP2 group. The resulting data demonstrate that the chitosan-coated SMP formulations stimulate the early events of an innate immune response, suggesting their ability to increase the immunogenicity of co-administered Leishmania antigens.

Using an Aluminum Hydroxide-Chitosan Matrix Increased the Vaccine Potential and Immune Response of Mice against Multi-Drug-Resistant Acinetobacter baumannii.

Acinetobacter baumannii is a Gram-negative, immobile, aerobic nosocomial opportunistic coccobacillus that causes pneumonia, septicemia, and urinary tract infections in immunosuppressed patients. There are no commercially available alternative antimicrobials, and multi-drug resistance is an urgent concern that requires emergency measures and new therapeutic strategies. This study evaluated a multi-drug-resistant A. baumannii whole-cell vaccine, inactivated and adsorbed on an aluminum hydroxide-chitosan (mAhC) matrix, in an A. baumannii sepsis model in immunosuppressed mice by cyclophosphamide (CY). CY-treated mice were divided into immunized, non-immunized, and adjuvant-inoculated groups. Three vaccine doses were given at 0D, 14D, and 28D, followed by a lethal dose of 4.0 × 108 CFU/mL of A. baumannii. Immunized CY-treated mice underwent a significant humoral response, with the highest IgG levels and a higher survival rate (85%); this differed from the non-immunized CY-treated mice, none of whom survived (p < 0.001), and from the adjuvant group, with 45% survival (p < 0.05). Histological data revealed the evident expansion of white spleen pulp from immunized CY-treated mice, whereas, in non-immunized and adjuvanted CY-treated mice, there was more significant organ tissue damage. Our results confirmed the proof-of-concept of the immune response and vaccine protection in a sepsis model in CY-treated mice, contributing to the advancement of new alternatives for protection against A. baumannii infections.

Methanolic Extracts of Chiococca alba in Aedes aegypti Biorational Management: Larvicidal and Repellent Potential, and Selectivity against Non-Target Organisms.

The use of formulations containing botanical products for controlling insects that vector human and animal diseases has increased in recent years. Plant extracts seem to offer fewer risks to the environment and to human health without reducing the application strategy's efficacy when compared to synthetic and conventional insecticides and repellents. Here, we evaluated the potential of extracts obtained from caninana, Chiococca alba (L.) Hitchc. (Rubiaceae), plants as a tool to be integrated into the management of Aedes aegypti, one of the principal vectors for the transmission of arborviruses in humans. We assessed the larvicidal and repellence performance against adult mosquitoes and evaluated the potential undesired effects of the extracts on non-target organisms. We assessed the susceptibility and predatory abilities of the nymphs of Belostoma anurum, a naturally occurring mosquito larva predator, and evaluated the C. alba extract's cytotoxic effects in mammalian cell lines. Our chromatographic analysis revealed 18 compounds, including rutin, naringin, myricetin, morin, and quercetin. The methanolic extracts of C. alba showed larvicidal (LC50 = 82 (72-94) mg/mL) activity without killing or affecting the abilities of B. anurum to prey upon mosquito larvae. Our in silico predictions revealed the molecular interactions between rutin and the AeagOBP1 receptor to be one possible mechanism for the repellent potential recorded for formulations containing C. alba extracts. Low cytotoxicity against mammalian cell lines reinforces the selectivity of C. alba extracts. Collectively, our findings highlight the potential of C. alba and one of its constituents (rutin) as alternative tools to be integrated into the management of A. aegypti mosquitoes.

Unraveling the susceptibility of paracoccidioidomycosis: Insights towards the pathogen-immune interplay and immunogenetics.

Paracoccidioidomycosis (PCM) is a life-threatening systemic mycosis caused by Paracoccidioides spp. This disease comprises three clinical forms: symptomatic acute and chronic forms (PCM disease) and PCM infection, a latent form without clinical symptoms. PCM disease differs markedly according to severity, clinical manifestations, and host immune response. Fungal virulence factors and adhesion molecules are determinants for entry, latency, immune escape and invasion, and dissemination in the host. Neutrophils and macrophages play a paramount role in first-line defense against the fungus through the recognition of antigens by pattern recognition receptors (PRRs), activating their microbicidal machinery. Furthermore, the clinical outcome of the PCM is strongly associated with the variability of cytokines and immunoglobulins produced by T and B cells. While the mechanisms that mediate susceptibility or resistance to infection are dictated by the immune system, some genetic factors may alter gene expression and its final products and, hence, modulate how the organism responds to infection and injury. This review outlines the main findings relative to this topic, addressing the complexity of the immune response triggered by Paracoccidioides spp. infection from preclinical investigations to studies in humans. Here, we focus on mechanisms of fungal pathogenesis, the patterns of innate and adaptive immunity, and the genetic and molecular basis related to immune response and susceptibility to the development of the PCM and its clinical forms. Immunogenetic features such as HLA system, cytokines/cytokines receptors genes and other immune-related genes, and miRNAs are likewise discussed. Finally, we point out the occurrence of PCM in patients with primary immunodeficiencies and call attention to the research gaps and challenges faced by the PCM field.