1
|
Reddy SB, Nagy N, Rönnberg C, Chiodi F, Lugaajju A, Heuts F, Szekely L, Wahlgren M, Persson KEM. Direct contact between Plasmodium falciparum and human B-cells in a novel co-culture increases parasite growth and affects B-cell growth. Malar J 2021; 20:303. [PMID: 34225761 PMCID: PMC8256226 DOI: 10.1186/s12936-021-03831-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2020] [Accepted: 06/24/2021] [Indexed: 11/17/2022] Open
Abstract
Background Plasmodium falciparum parasites cause malaria and co-exist in humans together with B-cells for long periods of time. Immunity is only achieved after repeated exposure. There has been a lack of methods to mimic the in vivo co-occurrence, where cells and parasites can be grown together for many days, and it has been difficult with long time in vitro studies. Methods and results A new method for growing P. falciparum in 5% CO2 with a specially formulated culture medium is described. This knowledge was used to establish the co-culture of live P. falciparum together with human B-cells in vitro for 10 days. The presence of B-cells clearly enhanced parasite growth, but less so when Transwell inserts were used (not allowing passage of cells or merozoites), showing that direct contact is advantageous. B-cells also proliferated more in presence of parasites. Symbiotic parasitic growth was verified using CESS cell-line and it showed similar results, indicating that B-cells are indeed the cells responsible for the effect. In malaria endemic areas, people often have increased levels of atypical memory B-cells in the blood, and in this assay it was demonstrated that when parasites were present there was an increase in the proportion of CD19 + CD20 + CD27 − FCRL4 + B-cells, and a contraction of classical memory B-cells. This effect was most clearly seen when direct contact between B-cells and parasites was allowed. Conclusions These results demonstrate that P. falciparum and B-cells undoubtedly can affect each other when allowed to multiply together, which is valuable information for future vaccine studies.
Collapse
Affiliation(s)
| | - Noemi Nagy
- Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Caroline Rönnberg
- Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.,Department of Clinical Microbiology, Karolinska University Hospital, Huddinge, Stockholm, Sweden
| | - Francesca Chiodi
- Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Allan Lugaajju
- Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.,Makerere University, Kampala, Uganda
| | - Frank Heuts
- Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Laszlo Szekely
- Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Mats Wahlgren
- Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Kristina E M Persson
- Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden. .,Department of Laboratory Medicine, Skåne University Hospital, Lund University, Lund, Sweden.
| |
Collapse
|
2
|
Zhou J, Feng G, Beeson J, Hogarth PM, Rogerson SJ, Yan Y, Jaworowski A. CD14(hi)CD16+ monocytes phagocytose antibody-opsonised Plasmodium falciparum infected erythrocytes more efficiently than other monocyte subsets, and require CD16 and complement to do so. BMC Med 2015; 13:154. [PMID: 26149666 PMCID: PMC4493812 DOI: 10.1186/s12916-015-0391-7] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Accepted: 06/03/2015] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND With more than 600,000 deaths from malaria, mainly of children under five years old and caused by infection with Plasmodium falciparum, comes an urgent need for an effective anti-malaria vaccine. Limited details on the mechanisms of protective immunity are a barrier to vaccine development. Antibodies play an important role in immunity to malaria and monocytes are key effectors in antibody-mediated protection by phagocytosing antibody-opsonised infected erythrocytes (IE). Eliciting antibodies that enhance phagocytosis of IE is therefore an important potential component of an effective vaccine, requiring robust assays to determine the ability of elicited antibodies to stimulate this in vivo. The mechanisms by which monocytes ingest IE and the nature of the monocytes which do so are unknown. METHODS Purified trophozoite-stage P. falciparum IE were stained with ethidium bromide, opsonised with anti-erythrocyte antibodies and incubated with fresh whole blood. Phagocytosis of IE and TNF production by individual monocyte subsets was measured by flow cytometry. Ingestion of IE was confirmed by imaging flow cytometry. RESULTS CD14(hi)CD16+ monocytes phagocytosed antibody-opsonised IE and produced TNF more efficiently than CD14(hi)CD16- and CD14(lo)CD16+ monocytes. Blocking experiments showed that Fcγ receptor IIIa (CD16) but not Fcγ receptor IIa (CD32a) or Fcγ receptor I (CD64) was necessary for phagocytosis. CD14(hi)CD16+ monocytes ingested antibody-opsonised IE when peripheral blood mononuclear cells were reconstituted with autologous serum but not heat-inactivated autologous serum. Antibody-opsonised IE were rapidly opsonised with complement component C3 in serum (t1/2 = 2-3 minutes) and phagocytosis of antibody-opsonised IE was inhibited in a dose-dependent manner by an inhibitor of C3 activation, compstatin. Compared to other monocyte subsets, CD14(hi)CD16+ monocytes expressed the highest levels of complement receptor 4 (CD11c) and activated complement receptor 3 (CD11b) subunits. CONCLUSIONS We show a special role for CD14(hi)CD16+ monocytes in phagocytosing opsonised P. falciparum IE and production of TNF. While ingestion was mediated by Fcγ receptor IIIa, this receptor was not sufficient to allow phagocytosis; despite opsonisation with antibody, phagocytosis of IE also required complement opsonisation. Assays which measure the ability of vaccines to elicit a protective antibody response to P. falciparum should consider their ability to promote phagocytosis and fix complement.
Collapse
Affiliation(s)
- Jingling Zhou
- Centre for Biomedical Research, Burnet Institute, Melbourne, Victoria, 3004, Australia.
| | - Gaoqian Feng
- Centre for Biomedical Research, Burnet Institute, Melbourne, Victoria, 3004, Australia.
| | - James Beeson
- Centre for Biomedical Research, Burnet Institute, Melbourne, Victoria, 3004, Australia. .,Department of Medicine, University of Melbourne, Melbourne, Victoria, 3050, Australia. .,Department of Microbiology, Monash University, Melbourne, Victoria, 3800, Australia.
| | - P Mark Hogarth
- Centre for Biomedical Research, Burnet Institute, Melbourne, Victoria, 3004, Australia.
| | - Stephen J Rogerson
- Department of Medicine, University of Melbourne, Melbourne, Victoria, 3050, Australia.
| | - Yan Yan
- Department of Chemical and Biomolecular Engineering, University of Melbourne, Melbourne, Victoria, 3800, Australia.
| | - Anthony Jaworowski
- Centre for Biomedical Research, Burnet Institute, Melbourne, Victoria, 3004, Australia. .,Department of Infectious Diseases, Monash University, Melbourne, Victoria, 3800, Australia. .,Department of Immunology, Monash University, Melbourne, Victoria, 3800, Australia.
| |
Collapse
|
3
|
Khaw LT, Ball HJ, Mitchell AJ, Grau GE, Stocker R, Golenser J, Hunt NH. Brain endothelial cells increase the proliferation of Plasmodium falciparum through production of soluble factors. Exp Parasitol 2014; 145:34-41. [PMID: 25045850 DOI: 10.1016/j.exppara.2014.07.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Revised: 05/06/2014] [Accepted: 07/08/2014] [Indexed: 01/01/2023]
Abstract
We here describe the novel finding that brain endothelial cells in vitro can stimulate the growth of Plasmodium falciparum through the production of low molecular weight growth factors. By using a conditioned medium approach, we show that the brain endothelial cells continued to release these factors over time. If this mirrors the in vivo situation, these growth factors potentially would provide an advantage, in terms of enhanced growth, for sequestered parasitised red blood cells in the brain microvasculature. We observed this phenomenon with brain endothelial cells from several sources as well as a second P. falciparum strain. The characteristics of the growth factors included: <3 kDa molecular weight, heat stable, and in part chloroform soluble. Future efforts should be directed at identifying these growth factors, since blocking their production or actions might be of benefit for reducing parasite load and, hence, malaria pathology.
Collapse
Affiliation(s)
- L T Khaw
- Molecular Immunopathology Unit, School of Medical Sciences and Bosch Institute, Sydney Medical School, University of Sydney, NSW 2006, Australia; Department of Parasitology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia
| | - H J Ball
- Molecular Immunopathology Unit, School of Medical Sciences and Bosch Institute, Sydney Medical School, University of Sydney, NSW 2006, Australia
| | - A J Mitchell
- Molecular Immunopathology Unit, School of Medical Sciences and Bosch Institute, Sydney Medical School, University of Sydney, NSW 2006, Australia; Immune Imaging Program, Centenary Institute, Sydney, NSW 2050, Australia
| | - G E Grau
- Vascular Immunology Unit, School of Medical Sciences and Bosch Institute, Sydney Medical School, University of Sydney, NSW 2006, Australia
| | - R Stocker
- Vascular Biology Division, Victor Chang Cardiac Research Institute, Lowy Packer Building, 405 Liverpool Street, Darlinghurst, NSW 2010, Australia
| | - J Golenser
- Department of Microbiology and Molecular Genetics, Kuvin Centre for the Study of Tropical and Infectious Diseases, Hebrew University of Jerusalem, Jerusalem, Israel
| | - N H Hunt
- Molecular Immunopathology Unit, School of Medical Sciences and Bosch Institute, Sydney Medical School, University of Sydney, NSW 2006, Australia.
| |
Collapse
|
4
|
Quelhas D, Puyol L, Quintó L, Nhampossa T, Serra-Casas E, Macete E, Aide P, Sanz S, Aponte JJ, Doolan DL, Alonso PL, Menéndez C, Dobaño C. Intermittent preventive treatment with sulfadoxine-pyrimethamine does not modify plasma cytokines and chemokines or intracellular cytokine responses to Plasmodium falciparum in Mozambican children. BMC Immunol 2012; 13:5. [PMID: 22280502 PMCID: PMC3398260 DOI: 10.1186/1471-2172-13-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2011] [Accepted: 01/26/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Cytokines and chemokines are key mediators of anti-malarial immunity. We evaluated whether Intermittent Preventive Treatment in infants with Sulfadoxine-Pyrimethamine (IPTi-SP) had an effect on the acquisition of these cellular immune responses in Mozambican children. Multiple cytokines and chemokines were quantified in plasma by luminex, and antigen-specific cytokine production in whole blood was determined by intracellular cytokine staining and flow cytometry, at ages 5, 9, 12 and 24 months. RESULTS IPTi-SP did not significantly affect the proportion of CD3+ cells producing IFN-γ, IL-4 or IL-10. Overall, plasma cytokine or chemokine concentrations did not differ between treatment groups. Th1 and pro-inflammatory responses were higher than Th2 and anti-inflammatory responses, respectively, and IFN-γ:IL-4 ratios were higher for placebo than for SP recipients. Levels of cytokines and chemokines varied according to age, declining from 5 to 9 months. Plasma concentrations of IL-10, IL-12 and IL-13 were associated with current infection or prior malaria episodes. Higher frequencies of IFN-γ and IL-10 producing CD3+ cells and elevated IL-10, IFN-γ, MCP-1 and IL-13 in plasma were individually associated with increased malaria incidence, at different time points. When all markers were analyzed together, only higher IL-17 at 12 months was associated with lower incidence of malaria up to 24 months. CONCLUSIONS Our work has confirmed that IPTi-SP does not negatively affect the development of cellular immune response during early childhood. This study has also provided new insights as to how these cytokine responses are acquired upon age and exposure to P. falciparum, as well as their associations with malaria susceptibility. TRIAL REGISTRATION ClinicalTrials.gov: NCT00209795.
Collapse
Affiliation(s)
- Diana Quelhas
- Centro de Investigação em Saúde da Manhiça, Manhiça, Mozambique
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
5
|
Abstract
Previous work has shown that human donors vary in the magnitude and pattern of cytokines induced when peripheral blood mononuclear cells (PBMCs) are co-cultured with Plasmodium falciparum–infected erythrocytes. Whether P. falciparum strains vary in their ability to induce cytokines has not been studied in detail and is an important question, because variation in cytokine induction could affect parasite virulence and patterns of clinical disease. We investigated the early inflammatory cytokine response to four P. falciparum laboratory strains and five field isolates. Initial studies showed that parasite strain, parasitaemia and PBMC donor all had significant effects on the magnitude of pro-inflammatory cytokine responses (IFN-γ, GM-CSF, IL-1β, TNF-α, IL-6, P < 0·005 in all cases). However, we noticed that the most highly inducing parasite strain consistently reached schizont rupture more rapidly than the other strains. When timing of schizont rupture was taken into account, parasite strains no longer differed in their cytokine induction (P = 0·383), although donor effects remained significant (P < 0·001). These data do not support the hypothesis that P. falciparum strains vary in induction of early innate cytokine responses from PBMCs, and instead are consistent with the suggestion that conserved parasite products such as haemozoin or GPI-anchors are the parasite-derived stimuli for cytokine induction.
Collapse
Affiliation(s)
- R A Corrigan
- Centre for Immunity, Infection and Evolution, Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | | |
Collapse
|
6
|
Feng G, Aitken E, Yosaatmadja F, Kalilani L, Meshnick SR, Jaworowski A, Simpson JA, Rogerson SJ. Antibodies to variant surface antigens of Plasmodium falciparum-infected erythrocytes are associated with protection from treatment failure and the development of anemia in pregnancy. J Infect Dis 2009; 200:299-306. [PMID: 19500037 DOI: 10.1086/599841] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
BACKGROUND In pregnancy-associated malaria (PAM), Plasmodium falciparum-infected erythrocytes (IEs) express variant surface antigens (VSA-PAM) that evade existing immunity and mediate placental sequestration. Antibodies to VSA-PAM develop with gravidity and block placental adhesion or opsonize IEs for phagocytic clearance, helping to prevent maternal anemia and low birth weight in infants. METHODS Using serum samples from 141 pregnant Malawian women with parasitemia enrolled in a randomized trial of antimalarials and VSA-PAM-expressing CS2 IEs, we quantified levels of immunoglobulin (Ig) G to VSA-PAM by flow cytometry and levels of opsonizing antibodies by measuring uptake of IEs by THP1 promonocytes. RESULTS After controlling for gravidity and antimalarial treatment, higher levels of IgG to VSA-PAM were associated with decreased anemia at delivery (odds ratio [OR], 0.66 [95% confidence interval {CI}, 0.46-0.93]; P = .018) and were weakly associated with decreased parasitological failure (OR, 0.78 [95% CI, 0.60-1.03]; P = .075), especially reinfection (OR, 0.73 [95% CI, 0.53-1.01]; P = .057). Higher levels of opsonizing antibodies to CS2 IEs were associated with less maternal anemia (OR, 0.31 [95% CI, 0.13-0.74]; P = .008) and treatment failure (OR, 0.48 [95% CI, 0.25-0.90]; P = .023), primarily because of recrudescent infection (OR, 0.49 [95% CI, 0.21-1.12]; P = .089). CONCLUSION Higher levels of both IgG antibodies to VSA-PAM and opsonizing antibodies, a functional measure of immunity, correlate with parasite clearance and less anemia in pregnancy malaria.
Collapse
Affiliation(s)
- Gaoqian Feng
- Department of Medicine, Royal Melbourne Hospital, Melbourne, Australia
| | | | | | | | | | | | | | | |
Collapse
|
7
|
Bouyou-Akotet MK, Mavoungou E. Natural killer cell IFN-gamma-activity is associated with Plasmodium falciparum infection during pregnancy. Exp Parasitol 2009; 123:265-8. [PMID: 19651125 DOI: 10.1016/j.exppara.2009.07.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2009] [Revised: 07/24/2009] [Accepted: 07/27/2009] [Indexed: 10/20/2022]
Abstract
The ability of natural killer (NK) cells to produce gamma interferon (IFN-gamma) after ex vivo stimulation with crude schizont lysate of Plasmodium falciparum was studied in uninfected and P. falciparum-infected pregnant Gabonese women segregated according to the gravidity at the time of delivery. This activity was measured in purified NK cells as well as in whole blood from the periphery and cord. Crude schizont lysate-stimulated NK cells from primiparous women produced significantly more IFN-gamma than those from multiparous women (P<0.001). Women with malaria infection produced more IFN-gamma than negative women in peripheral blood (P<0.001) indicating that immunological determinants regulating the susceptibility to malaria in pregnant women are parasite-specific. These findings reveal that NK cells are major source of IFN-gamma when exposed to P. falciparum antigens in vitro in absence of any other co-stimulant.
Collapse
Affiliation(s)
- Marielle K Bouyou-Akotet
- Département de Parasitologie, Mycologie, Médecine Tropicale, Université des Sciences de la Santé, Libreville, Gabon
| | | |
Collapse
|
8
|
Cellular tumor necrosis factor, gamma interferon, and interleukin-6 responses as correlates of immunity and risk of clinical Plasmodium falciparum malaria in children from Papua New Guinea. Infect Immun 2009; 77:3033-43. [PMID: 19380468 DOI: 10.1128/iai.00211-09] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The role of early to intermediate Plasmodium falciparum-induced cellular responses in the development of clinical immunity to malaria is not well understood, and such responses have been proposed to contribute to both immunity and risk of clinical malaria episodes. To investigate whether P. falciparum-induced cellular responses are able to function as predictive correlates of parasitological and clinical outcomes, we conducted a prospective cohort study of children (5 to 14 years of age) residing in a region of Papua New Guinea where malaria is endemic Live, intact P. falciparum-infected red blood cells were applied to isolated peripheral blood mononuclear cells obtained at baseline. Cellular cytokine production, including production of interleukin-2 (IL-2), IL-4, IL-6, IL-10, tumor necrosis factor (TNF) (formerly tumor necrosis factor alpha), and gamma interferon (IFN-gamma), was measured, and the cellular source of key cytokines was investigated. Multicytokine models revealed that increasing P. falciparum-induced IL-6 production was associated with an increased incidence of P. falciparum clinical episodes (incidence rate ratio [IRR], 1.75; 95% confidence interval [CI], 1.20 to 2.53), while increasing P. falciparum-induced TNF and IFN-gamma production was associated with a reduced incidence of clinical episodes (IRR for TNF, 0.55 [95% CI, 0.38 to 0.80]; IRR for IFN-gamma, 0.71 [95% CI, 0.55 to 0.90]). Furthermore, we found that monocytes/macrophages and gammadelta-T cells are important for the P. falciparum-induced production of IL-6 and TNF. Early to intermediate cellular cytokine responses to P. falciparum may therefore be important correlates of immunity and risk of symptomatic malaria episodes and thus warrant detailed investigation in relation to the development and implementation of effective vaccines.
Collapse
|
9
|
Walther M, Woodruff J, Edele F, Jeffries D, Tongren JE, King E, Andrews L, Bejon P, Gilbert SC, De Souza JB, Sinden R, Hill AVS, Riley EM. Innate Immune Responses to Human Malaria: Heterogeneous Cytokine Responses to Blood-Stage Plasmodium falciparum Correlate with Parasitological and Clinical Outcomes. THE JOURNAL OF IMMUNOLOGY 2006; 177:5736-45. [PMID: 17015763 DOI: 10.4049/jimmunol.177.8.5736] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Taking advantage of a sporozoite challenge model established to evaluate the efficacy of new malaria vaccine candidates, we have explored the kinetics of systemic cytokine responses during the prepatent period of Plasmodium falciparum infection in 18 unvaccinated, previously malaria-naive subjects, using a highly sensitive, bead-based multiplex assay, and relate these data to peripheral parasite densities as measured by quantitative real-time PCR. These data are complemented with the analysis of cytokine production measured in vitro from whole blood or PBMC, stimulated with P. falciparum-infected RBC. We found considerable qualitative and quantitative interindividual variability in the innate responses, with subjects falling into three groups according to the strength of their inflammatory response. One group secreted moderate levels of IFN-gamma and IL-10, but no detectable IL-12p70. A second group produced detectable levels of circulating IL-12p70 and developed very high levels of IFN-gamma and IL-10. The third group failed to up-regulate any significant proinflammatory responses, but showed the highest levels of TGF-beta. Proinflammatory responses were associated with more rapid control of parasite growth but only at the cost of developing clinical symptoms, suggesting that the initial innate response may have far-reaching consequences on disease outcome. Furthermore, the in vitro observations on cytokine kinetics presented here, suggest that intact schizont-stage infected RBC can trigger innate responses before rupture of the infected RBC.
Collapse
Affiliation(s)
- Michael Walther
- Center for Clinical Vaccinology and Tropical Medicine, Nuffield Department of Clinical Medicine, Oxford University, Churchill Hospital, Oxford, United Kingdom.
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Cox SE, Arthur P, Kirkwood BR, Yeboah-Antwi K, Riley EM. Vitamin A supplementation increases ratios of proinflammatory to anti-inflammatory cytokine responses in pregnancy and lactation. Clin Exp Immunol 2006; 144:392-400. [PMID: 16734607 PMCID: PMC1941972 DOI: 10.1111/j.1365-2249.2006.03082.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Vitamin A supplementation reduces child mortality in populations at risk of vitamin A deficiency and may also reduce maternal mortality. One possible explanation for this is that vitamin A deficiency is associated with altered immune function and cytokine dysregulation. Vitamin A deficiency in pregnancy may thus compound the pregnancy-associated bias of cellular immune responses towards Th-2-like responses and exacerbate susceptibility to intracellular pathogens. We assessed mitogen and antigen-induced cytokine responses during pregnancy and lactation in Ghanaian primigravidae receiving either vitamin A supplementation or placebo. This was a double-blind, randomized, placebo-controlled trial of weekly vitamin A supplementation in pregnant and lactating women. Pregnancy compared to postpartum was associated with a suppression of cytokine responses, in particular of the proinflammatory cytokines interferon (IFN)-gamma and tumour necrosis factor (TNF)-alpha. Mitogen-induced TNF-alpha responses were associated with a decreased risk of peripheral parasitaemia during pregnancy. Furthermore, vitamin A supplementation was significantly associated with an increased ratio of mitogen-induced proinflammatory cytokine (IFN-gamma) to anti-inflammatory cytokine (IL-10) during pregnancy and in the postpartum period. The results of this study indicate that suppression of proinflammatory type 1 immune responses and hence immunity to intracellular infections, resulting from the combined effects of pregnancy and vitamin A deficiency, might be ameliorated by vitamin A supplementation.
Collapse
Affiliation(s)
- S E Cox
- Department of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine (LSHTM), London, UK.
| | | | | | | | | |
Collapse
|
11
|
Abstract
It is widely perceived that immunity to malaria is, to an extent, defective and that one component of this defective immune response is the inability to induce or maintain long-term memory responses. If true, this is likely to pose problems for development of an effective vaccine against malaria. In this article, we critically review and challenge this interpretation of the epidemiological and experimental evidence. While evasion and modulation of host immune responses clearly occurs and naturally acquired immunity is far from optimal, mechanisms to control blood-stage parasites are acquired and maintained by individuals living in endemic areas, allowing parasite density to be kept below the threshold for induction of acute disease. Furthermore, protective immunity to severe pathology is achieved relatively rapidly and is maintained in the absence of boosting by re-infection. Nevertheless, there are significant challenges to overcome. The need for multiple infections to acquire immunity means that young children remain at risk of infection for far too long. Persistent or frequent exposure to antigen seems to be required to maintain anti-parasite immunity (premunition). Lastly, pre-erythrocytic and sexual stages of the life cycle are poorly immunogenic, and there is little evidence of effective pre-erythrocytic or transmission-blocking immunity at the population level. While these problems might theoretically be due to defective immunological memory, we suggest alternative explanations. Moreover, we question the extent to which these problems are malaria-specific rather than generic (i.e. result from inherent limitations of the vertebrate immune system).
Collapse
Affiliation(s)
- Siske S Struik
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK
| | | |
Collapse
|