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Frontiers in Immunology 2024Malaria remains a global health challenge, necessitating the development of effective vaccines. The RTS,S vaccination prevents (Pf) malaria but is ineffective against...
Malaria remains a global health challenge, necessitating the development of effective vaccines. The RTS,S vaccination prevents (Pf) malaria but is ineffective against (Pv) disease. Herein, we evaluated the murine immunogenicity of a recombinant PvCSP incorporating prevalent polymorphisms, adjuvanted with Alhydrogel or Poly I:C. Both formulations induced prolonged IgG responses, with IgG1 dominance by the Alhydrogel group and high titers of all IgG isotypes by the Poly I:C counterpart. Poly I:C-adjuvanted vaccination increased splenic plasma cells, terminally-differentiated memory cells (MBCs), and precursors relative to the Alhydrogel-combined immunization. Splenic B-cells from Poly I:C-vaccinated mice revealed an antibody-secreting cell- and MBC-differentiating gene expression profile. Biological processes such as antibody folding and secretion were highlighted by the Poly I:C-adjuvanted vaccination. These findings underscore the potential of Poly I:C to strengthen immune responses against Pv malaria.
Topics: Poly I-C; Plasmodium vivax; Immunity, Humoral; Immunity, Cellular; Protozoan Proteins; Malaria Vaccines; Aluminum Hydroxide; Immunoglobulin G; Male; Animals; Plasma Cells; Female; Mice, Inbred C57BL; Recombinant Proteins; Vaccination; Adjuvants, Vaccine; Immunogenicity, Vaccine; Malaria, Vivax
PubMed: 38650939
DOI: 10.3389/fimmu.2024.1331474 -
BMC Medicine Apr 2024The stalling global progress in malaria control highlights the need for novel tools for malaria elimination, including transmission-blocking vaccines.... (Randomized Controlled Trial)
Randomized Controlled Trial
BACKGROUND
The stalling global progress in malaria control highlights the need for novel tools for malaria elimination, including transmission-blocking vaccines. Transmission-blocking vaccines aim to induce human antibodies that block parasite development in the mosquito and mosquitoes becoming infectious. The Pfs48/45 protein is a leading Plasmodium falciparum transmission-blocking vaccine candidate. The R0.6C fusion protein, consisting of Pfs48/45 domain 3 (6C) and the N-terminal region of P. falciparum glutamate-rich protein (R0), has previously been produced in Lactococcus lactis and elicited functional antibodies in rodents. Here, we assess the safety and transmission-reducing efficacy of R0.6C adsorbed to aluminium hydroxide with and without Matrix-M™ adjuvant in humans.
METHODS
In this first-in-human, open-label clinical trial, malaria-naïve adults, aged 18-55 years, were recruited at the Radboudumc in Nijmegen, the Netherlands. Participants received four intramuscular vaccinations on days 0, 28, 56 and 168 with either 30 µg or 100 µg of R0.6C and were randomised for the allocation of one of the two different adjuvant combinations: aluminium hydroxide alone, or aluminium hydroxide combined with Matrix-M1™ adjuvant. Adverse events were recorded from inclusion until 84 days after the fourth vaccination. Anti-R0.6C and anti-6C IgG titres were measured by enzyme-linked immunosorbent assay. Transmission-reducing activity of participants' serum and purified vaccine-specific immunoglobulin G was assessed by standard membrane feeding assays using laboratory-reared Anopheles stephensi mosquitoes and cultured P. falciparum gametocytes.
RESULTS
Thirty-one participants completed four vaccinations and were included in the analysis. Administration of all doses was safe and well-tolerated, with one related grade 3 adverse event (transient fever) and no serious adverse events occurring. Anti-R0.6C and anti-6C IgG titres were similar between the 30 and 100 µg R0.6C arms, but higher in Matrix-M1™ arms. Neat participant sera did not induce significant transmission-reducing activity in mosquito feeding experiments, but concentrated vaccine-specific IgGs purified from sera collected two weeks after the fourth vaccination achieved up to 99% transmission-reducing activity.
CONCLUSIONS
R0.6C/aluminium hydroxide with or without Matrix-M1™ is safe, immunogenic and induces functional Pfs48/45-specific transmission-blocking antibodies, albeit at insufficient serum concentrations to result in transmission reduction by neat serum. Future work should focus on identifying alternative vaccine formulations or regimens that enhance functional antibody responses.
TRIAL REGISTRATION
The trial is registered with ClinicalTrials.gov under identifier NCT04862416.
Topics: Adolescent; Adult; Animals; Female; Humans; Male; Middle Aged; Young Adult; Adjuvants, Immunologic; Aluminum Hydroxide; Antibodies, Protozoan; Malaria Vaccines; Malaria, Falciparum; Membrane Glycoproteins; Netherlands; Plasmodium falciparum; Protozoan Proteins
PubMed: 38649867
DOI: 10.1186/s12916-024-03379-y -
Malaria Journal Apr 2024Sporozoites (SPZ), the infective form of Plasmodium falciparum malaria, can be inoculated into the human host skin by Anopheline mosquitoes. These SPZ migrate at...
BACKGROUND
Sporozoites (SPZ), the infective form of Plasmodium falciparum malaria, can be inoculated into the human host skin by Anopheline mosquitoes. These SPZ migrate at approximately 1 µm/s to find a blood vessel and travel to the liver where they infect hepatocytes and multiply. In the skin they are still low in number (50-100 SPZ) and vulnerable to immune attack by antibodies and skin macrophages. This is why whole SPZ and SPZ proteins are used as the basis for most malaria vaccines currently deployed and undergoing late clinical testing. Mosquitoes typically inoculate SPZ into a human host between 14 and 25 days after their previous infective blood meal. However, it is unknown whether residing time within the mosquito affects SPZ condition, infectivity or immunogenicity. This study aimed to unravel how the age of P. falciparum SPZ in salivary glands (14, 17, or 20 days post blood meal) affects their infectivity and the ensuing immune responses.
METHODS
SPZ numbers, viability by live/dead staining, motility using dedicated sporozoite motility orienting and organizing tool software (SMOOT), and infectivity of HC-04.j7 liver cells at 14, 17 and 20 days after mosquito feeding have been investigated. In vitro co-culture assays with SPZ stimulated monocyte-derived macrophages (MoMɸ) and CD8 T-cells, analysed by flow cytometry, were used to investigate immune responses.
RESULTS
SPZ age did not result in different SPZ numbers or viability. However, a markedly different motility pattern, whereby motility decreased from 89% at day 14 to 80% at day 17 and 71% at day 20 was observed (p ≤ 0.0001). Similarly, infectivity of day 20 SPZ dropped to ~ 50% compared with day 14 SPZ (p = 0.004). MoMɸ were better able to take up day 14 SPZ than day 20 SPZ (from 7.6% to 4.1%, p = 0.03) and displayed an increased expression of pro-inflammatory CD80, IL-6 (p = 0.005), regulatory markers PDL1 (p = 0.02), IL-10 (p = 0.009) and cytokines upon phagocytosis of younger SPZ. Interestingly, co-culture of these cells with CD8 T-cells revealed a decreased expression of activation marker CD137 and cytokine IFNγ compared to their day 20 counterparts. These findings suggest that older (day 17-20) P. falciparum SPZ are less infectious and have decreased immune regulatory potential.
CONCLUSION
Overall, this data is a first step in enhancing the understanding of how mosquito residing time affects P. falciparum SPZ and could impact the understanding of the P. falciparum infectious reservoir and the potency of whole SPZ vaccines.
Topics: Animals; Humans; Sporozoites; CD8-Positive T-Lymphocytes; Malaria, Falciparum; Malaria Vaccines; Culicidae; Aging; Plasmodium falciparum
PubMed: 38641838
DOI: 10.1186/s12936-024-04946-7 -
Frontiers in Microbiology 2024Leishmaniasis is a vector-borne disease caused by the protozoan parasite of genus and is a complex disease affecting mostly tropical regions of the world.... (Review)
Review
Leishmaniasis is a vector-borne disease caused by the protozoan parasite of genus and is a complex disease affecting mostly tropical regions of the world. Unfortunately, despite the extensive effort made, there is no vaccine available for human use. Undoubtedly, a comprehensive understanding of the host-vector-parasite interaction is substantial for developing an effective prophylactic vaccine. Recently the role of sandfly saliva on disease progression has been uncovered which can make a substantial contribution in vaccine design. In this review we try to focus on the strategies that most probably meet the prerequisites of vaccine development (based on the current understandings) including live attenuated/non-pathogenic and subunit DNA vaccines. Innovative approaches such as reverse genetics, CRISP/R-Cas9 and antibiotic-free selection are now available to promisingly compensate for intrinsic drawbacks associated with these platforms. Our main goal is to call more attention toward the prerequisites of effective vaccine development while controlling the disease outspread is a substantial need.
PubMed: 38633699
DOI: 10.3389/fmicb.2024.1326369 -
Malaria Journal Apr 2024To gain a deeper understanding of protective immunity against relapsing malaria, this study examined sporozoite-specific T cell responses induced by a chemoprophylaxis...
Superior protection in a relapsing Plasmodium cynomolgi rhesus macaque model by a chemoprophylaxis with sporozoite immunization regimen with atovaquone-proguanil followed by primaquine.
BACKGROUND
To gain a deeper understanding of protective immunity against relapsing malaria, this study examined sporozoite-specific T cell responses induced by a chemoprophylaxis with sporozoite (CPS) immunization in a relapsing Plasmodium cynomolgi rhesus macaque model.
METHODS
The animals received three CPS immunizations with P. cynomolgi sporozoites, administered by mosquito bite, while under two anti-malarial drug regimens. Group 1 (n = 6) received artesunate/chloroquine (AS/CQ) followed by a radical cure with CQ plus primaquine (PQ). Group 2 (n = 6) received atovaquone-proguanil (AP) followed by PQ. After the final immunization, the animals were challenged with intravenous injection of 10 P. cynomolgi sporozoites, the dose that induced reliable infection and relapse rate. These animals, along with control animals (n = 6), were monitored for primary infection and subsequent relapses. Immunogenicity blood draws were done after each of the three CPS session, before and after the challenge, with liver, spleen and bone marrow sampling and analysis done after the challenge.
RESULTS
Group 2 animals demonstrated superior protection, with two achieving protection and two experiencing partial protection, while only one animal in group 1 had partial protection. These animals displayed high sporozoite-specific IFN-γ T cell responses in the liver, spleen, and bone marrow after the challenge with one protected animal having the highest frequency of IFN-γ CD8, IFN-γ CD4, and IFN-γ γδ T cells in the liver. Partially protected animals also demonstrated a relatively high frequency of IFN-γ CD8, IFN-γ CD4, and IFN-γ γδ T cells in the liver. It is important to highlight that the second animal in group 2, which experienced protection, exhibited deficient sporozoite-specific T cell responses in the liver while displaying average to high T cell responses in the spleen and bone marrow.
CONCLUSIONS
This research supports the notion that local liver T cell immunity plays a crucial role in defending against liver-stage infection. Nevertheless, there is an instance where protection occurs independently of T cell responses in the liver, suggesting the involvement of the liver's innate immunity. The relapsing P. cynomolgi rhesus macaque model holds promise for informing the development of vaccines against relapsing P. vivax.
Topics: Animals; Primaquine; Sporozoites; Macaca mulatta; Plasmodium cynomolgi; Immunization; Malaria Vaccines; Chemoprevention; CD8-Positive T-Lymphocytes; Proguanil; Drug Combinations; Atovaquone
PubMed: 38632607
DOI: 10.1186/s12936-024-04933-y -
Traffic (Copenhagen, Denmark) Apr 2024The protozoan parasites Plasmodium falciparum, Leishmania spp. and Trypanosoma cruzi continue to exert a significant toll on the disease landscape of the human...
The protozoan parasites Plasmodium falciparum, Leishmania spp. and Trypanosoma cruzi continue to exert a significant toll on the disease landscape of the human population in sub-Saharan Africa and Latin America. Control measures have helped reduce the burden of their respective diseases-malaria, leishmaniasis and Chagas disease-in endemic regions. However, the need for new drugs, innovative vaccination strategies and molecular markers of disease severity and outcomes has emerged because of developing antimicrobial drug resistance, comparatively inadequate or absent vaccines, and a lack of trustworthy markers of morbid outcomes. Extracellular vesicles (EVs) have been widely reported to play a role in the biology and pathogenicity of P. falciparum, Leishmania spp. and T. cruzi ever since they were discovered. EVs are secreted by a yet to be fully understood mechanism in protozoans into the extracellular milieu and carry a cargo of diverse molecules that reflect the originator cell's metabolic state. Although our understanding of the biogenesis and function of EVs continues to deepen, the question of how EVs in P. falciparum, Leishmania spp. and T. cruzi can serve as targets for a translational agenda into clinical and public health interventions is yet to be fully explored. Here, as a consortium of protozoan researchers, we outline a plan for future researchers and pose three questions to direct an EV's translational agenda in P. falciparum, Leishmania spp. and T. cruzi. We opine that in the long term, executing this blueprint will help bridge the current unmet needs of these medically important protozoan diseases in sub-Saharan Africa and Latin America.
Topics: Animals; Humans; Parasites; Trypanosoma cruzi; Chagas Disease; Leishmania; Extracellular Vesicles
PubMed: 38629580
DOI: 10.1111/tra.12935 -
Malaria Journal Apr 2024Malaria remains a significant global health burden affecting millions of people, children under 5 years and pregnant women being most vulnerable. In 2019, the World...
BACKGROUND
Malaria remains a significant global health burden affecting millions of people, children under 5 years and pregnant women being most vulnerable. In 2019, the World Health Organization (WHO) endorsed the introduction of RTS,S/AS01 malaria vaccine as Phase IV implementation evaluation in three countries: Malawi, Kenya and Ghana. Acceptability and factors influencing vaccination coverage in implementing areas is relatively unknown. In Malawi, only 60% of children were fully immunized with malaria vaccine in Nsanje district in 2021, which is below 80% WHO target. This study aimed at exploring factors influencing uptake of malaria vaccine and identify approaches to increase vaccination.
METHODS
In a cross-sectional study conducted in April-May, 2023, 410 mothers/caregivers with children aged 24-36 months were selected by stratified random sampling and interviewed using a structured questionnaire. Vaccination data was collected from health passports, for those without health passports, data was collected using recall history. Regression analyses were used to test association between independent variables and full uptake of malaria vaccine.
RESULTS
Uptake of malaria vaccine was 90.5% for dose 1, but reduced to 87.6%, 69.5% and 41.2% for dose 2, 3, and 4 respectively. Children of caregivers with secondary or upper education and those who attended antenatal clinic four times or more had increased odds of full uptake of malaria vaccine [OR: 2.43, 95%CI 1.08-6.51 and OR: 1.89, 95%CI 1.18-3.02], respectively. Children who ever suffered side-effects following immunization and those who travelled long distances to reach the vaccination centre had reduced odds of full uptake of malaria vaccine [OR: 0.35, 95%CI 0.06-0.25 and OR: 0.30, 95%CI 0.03-0.39] respectively. Only 17% (n = 65) of mothers/caregivers knew the correct schedule for vaccination and 38.5% (n = 158) knew the correct number of doses a child was to receive.
CONCLUSION
Only RTS,S dose 1 and 2 uptake met WHO coverage targets. Mothers/caregivers had low level of information regarding malaria vaccine, especially on numbers of doses to be received and dosing schedule. The primary modifiable factor influencing vaccine uptake was mother/caregiver knowledge about the vaccine. Thus, to increase the uptake Nsanje District Health Directorate should strengthen communities' education about malaria vaccine. Programmes to strengthen mother/caregiver knowledge should be included in scale-up of the vaccine in Malawi and across sub-Saharan Africa.
Topics: Pregnancy; Child; Humans; Female; Infant; Child, Preschool; Malaria Vaccines; Malawi; Cross-Sectional Studies; Malaria; Vaccination
PubMed: 38627704
DOI: 10.1186/s12936-024-04938-7 -
Indian Journal of Medical Microbiology 2024
Topics: Humans; Malaria; Vaccination; Travel; Child; Endemic Diseases; Malaria Vaccines; Child, Preschool
PubMed: 38615989
DOI: 10.1016/j.ijmmb.2024.100593 -
The Lancet. Global Health May 2024
Topics: Humans; Malaria Vaccines; Burkina Faso; Cameroon
PubMed: 38614624
DOI: 10.1016/S2214-109X(24)00101-3 -
International Journal of Molecular... Mar 2024Chagas disease (CD) is a vector-borne Neglected Zoonotic Disease (NZD) caused by a flagellate protozoan, , that affects various mammalian species across America,... (Review)
Review
Chagas disease (CD) is a vector-borne Neglected Zoonotic Disease (NZD) caused by a flagellate protozoan, , that affects various mammalian species across America, including humans and domestic animals. However, due to an increase in population movements and new routes of transmission, infection is presently considered a worldwide health concern, no longer restricted to endemic countries. Dogs play a major role in the domestic cycle by acting very efficiently as reservoirs and allowing the perpetuation of parasite transmission in endemic areas. Despite the significant progress made in recent years, still there is no vaccine against human and animal disease, there are few drugs available for the treatment of human CD, and there is no standard protocol for the treatment of canine CD. In this review, we highlight human and canine Chagas Disease in its different dimensions and interconnections. Dogs, which are considered to be the most important peridomestic reservoir and sentinel for the transmission of infection in a community, develop CD that is clinically similar to human CD. Therefore, an integrative approach, based on the One Health concept, bringing together the advances in genomics, immunology, and epidemiology can lead to the effective development of vaccines, new treatments, and innovative control strategies to tackle CD.
Topics: Humans; Dogs; Animals; Chagas Disease; Animals, Domestic; Trypanosoma cruzi; Animal Diseases; Dog Diseases; Mammals
PubMed: 38612650
DOI: 10.3390/ijms25073840