Impact of Epstein-Barr virus co-infection on natural acquired Plasmodium vivax antibody response.

BACKGROUND: The simultaneous infection of Plasmodium falciparum and Epstein-Barr virus (EBV) could promote the development of the aggressive endemic Burkitt's Lymphoma (eBL) in children living in P. falciparum holoendemic areas. While it is well-established that eBL is not related to other human malaria parasites, the impact of EBV infection on the generation of human malaria immunity remains largely unexplored. Considering that this highly prevalent herpesvirus establishes a lifelong persistent infection on B-cells with possible influence on malaria immunity, we hypothesized that EBV co-infection could have impact on the naturally acquired antibody responses to P. vivax, the most widespread human malaria parasite. METHODOLOGY/PRINCIPAL FINDINGS: The study design involved three cross-sectional surveys at six-month intervals (baseline, 6 and 12 months) among long-term P. vivax exposed individuals living in the Amazon rainforest. The approach focused on a group of malaria-exposed individuals whose EBV-DNA (amplification of balf-5 gene) was persistently detected in the peripheral blood (PersVDNA, n = 27), and an age-matched malaria-exposed group whose EBV-DNA could never be detected during the follow-up (NegVDNA, n = 29). During the follow-up period, the serological detection of EBV antibodies to lytic/ latent viral antigens showed that IgG antibodies to viral capsid antigen (VCA-p18) were significantly different between groups (PersVDNA > NegVDNA). A panel of blood-stage P. vivax antigens covering a wide range of immunogenicity confirmed that in general PersVDNA group showed low levels of antibodies as compared with NegVDNA. Interestingly, more significant differences were observed to a novel DBPII immunogen, named DEKnull-2, which has been associated with long-term neutralizing antibody response. Differences between groups were less pronounced with blood-stage antigens (such as MSP1-19) whose levels can fluctuate according to malaria transmission. CONCLUSIONS/SIGNIFICANCE: In a proof-of-concept study we provide evidence that a persistent detection of EBV-DNA in peripheral blood of adults in a P. vivax semi-immune population may impact the long-term immune response to major malaria vaccine candidates.

Endemic Burkitt lymphoma: a complication of asymptomatic malaria in sub-Saharan Africa based on published literature and primary data from Uganda, Tanzania, and Kenya.

BACKGROUND: Endemic Burkitt lymphoma (eBL) is an aggressive B cell non-Hodgkin lymphoma associated with antigenic stimulation from Plasmodium falciparum malaria. Whether eBL risk is related to malaria parasite density is unknown. To address this issue, children with eBL, asymptomatic and clinical malaria, as a surrogate of malaria parasite density, were assessed. METHODS: Malaria-related laboratory results (parasite density, haemoglobin, platelet count, and white cell count [WBC]) count) were compiled for 4019 eBL cases and 80,532 subjects evaluated for asymptomatic malaria or clinical malaria (severe malaria anaemia, hyperparasitaemia, cerebral malaria, malaria prostration, moderate malaria, and mild malaria) in 21 representative studies published in Africa (mostly East Africa) and 850 eBL cases and 2878 controls with primary data from the Epidemiology of Burkitt Lymphoma in East African Children and Minors (EMBLEM) case-control study in Uganda, Tanzania, and Kenya. The average values of malaria-related laboratory results were computed by condition and trends across single-year age groups were assessed using regression and spline models. RESULTS: Overall, malaria infection or malaria was diagnosed in 37,089 of children compiled from the literature. Children with eBL and asymptomatic parasitaemia/antigenaemia, but not those with clinical malaria, were closest in their mean age (age 7.1-7.2 vs. 7.4-9.8 years), haemoglobin level (10.0-10.4 vs. 11.7-12.3 g/dL), malaria parasite density (2800 vs. 1827-7780 parasites/µL), platelet count (347,000-353,000 vs. 244,000-306,000 platelets/µL), and WBC count (8180-8890 vs. 7100-7410 cells/µL). Parasite density in these two groups peaked between four to five years, then decreased steadily thereafter; conversely, haemoglobin showed a corresponding increase with age. Children with clinical malaria were markedly different: all had an average age below 5 years, had dramatically elevated parasite density (13,905-869,000 parasites/µL) and dramatically decreased platelet count (< 159,000 platelets/µL) and haemoglobin (< 7 g/dL). CONCLUSIONS: eBL and asymptomatic parasitaemia/antigenaemia, but not clinical malaria, were the most similar conditions with respect to mean age and malaria-related laboratory results. These results suggest that children with asymptomatic parasitaemia/antigenaemia may be the population at risk of eBL.

Endemic Burkitt lymphoma - an aggressive childhood cancer linked to Plasmodium falciparum exposure, but not to exposure to other malaria parasites.

Burkitt lymphoma (BL) is an aggressive non-Hodgkin lymphoma. The prevalence of BL is ten-fold higher in areas with stable transmission of Plasmodium falciparum malaria, where it is the most common childhood cancer, and is referred to as endemic BL (eBL). In addition to its association with exposure to P. falciparum infection, eBL is strongly associated with Epstein-Barr virus (EBV) infection (>90%). This is in contrast to BL as it occurs outside P. falciparum-endemic areas (sporadic BL), where only a minority of the tumours are EBV-positive. Although the striking geographical overlap in the distribution of eBL and P. falciparum was noted shortly after the first detailed description of eBL in 1958, the molecular details of the interaction between malaria and eBL remain unresolved. It is furthermore unexplained why exposure to P. falciparum appears to be essentially a prerequisite to the development of eBL, whereas other types of malaria parasites that infect humans have no impact. In this brief review, we summarize how malaria exposure may precipitate the malignant transformation of a B-cell clone that leads to eBL, and propose an explanation for why P. falciparum uniquely has this capacity.

Associations between IgG reactivity to Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) antigens and Burkitt lymphoma in Ghana and Uganda case-control studies.

BACKGROUND: Endemic Burkitt lymphoma (eBL) is an aggressive childhood B-cell lymphoma linked to Plasmodium falciparum (Pf) malaria in sub-Saharan Africa. We investigated antibody reactivity to several human receptor-binding domains of the Pf erythrocyte membrane protein 1 (PfEMP1) that play a key role in malaria pathogenesis and are targets of acquired immunity to malaria. METHODS: Serum/plasma IgG antibody reactivity was measured to 22 Pf antigens, including 18 to PfEMP1 CIDR domains between cases and controls from two populations (149 eBL cases and 150 controls from Ghana and 194 eBL cases and 600 controls from Uganda). Adjusted odds ratios (aORs) for case-control associations were estimated by logistic regression. FINDINGS: There was stronger reactivity to the severe malaria associated CIDRα1 domains than other CIDR domains both in cases and controls. eBL cases reacted to fewer antigens than controls (Ghana: p = 0·001; Uganda: p = 0·03), with statistically significant lower ORs associated with reactivity to 13+ antigens in Ghana (aOR 0·39, 95% CI 0·24-0·63; pheterogeneity = 0·00011) and Uganda (aOR 0·60, 95% CI 0.41-0·88; pheterogeneity = 0·008). eBL was inversely associated with reactivity, coded as quartiles, to group A variant CIDRδ1 (ptrend = 0·035) in Ghana and group B CD36-binding variants CIDRα2·2 (ptrend = 0·006) and CIDRα2·4 (ptrend = 0·033) in Uganda, and positively associated with reactivity to SERA5 in Ghana (ptrend = 0·017) and Uganda (ptrend = 0·007) and group A CIDRα1·5 variant in Uganda only (ptrend = 0·034). INTERPRETATION: eBL cases reacted to fewer antigens than controls using samples from two populations, Ghana and Uganda. Attenuated humoral immunity to Pf EMP1 may contribute to susceptibility to low-grade malaria and eBL risk. FUNDING: Intramural Research Program, National Cancer Institute and National Institute of Allergy and Infectious Diseases, National Institutes of Health, Department of Health and Human Services.

Evaluating the Causal Link Between Malaria Infection and Endemic Burkitt Lymphoma in Northern Uganda: A Mendelian Randomization Study.

BACKGROUND: Plasmodium falciparum (Pf) malaria infection is suspected to cause endemic Burkitt Lymphoma (eBL), but the evidence remains unsettled. An inverse relationship between sickle cell trait (SCT) and eBL, which supports that between malaria and eBL, has been reported before, but in small studies with low power. We investigated this hypothesis in children in a population-based study in northern Uganda using Mendelian Randomization. METHODS: Malaria-related polymorphisms (SCT, IL10, IL1A, CD36, SEMA3C, and IFNAR1) were genotyped in 202 eBL cases and 624 controls enrolled during 2010-2015. We modeled associations between genotypes and eBL or malaria using logistic regression. FINDINGS: SCT was associated with decreased risk of eBL (adjusted odds ratio [OR] 0·37, 95% CI 0·21-0·66; p=0·0003). Decreased risk of eBL was associated with IL10 rs1800896-CT (OR 0·73, 95% CI 0·50-1·07) and -CC genotypes (OR 0·53, 95% CI 0·29-0·95, ptrend=0·019); IL1A rs2856838-AG (OR 0·56, 95% CI 0·39-0·81) and -AA genotype (OR 0·50, 95% CI 0·28-1·01, ptrend=0·0016); and SEMA3C rs4461841-CT or -CC genotypes (OR 0·57, 95% CI 0·35-0·93, p=0·0193). SCT and IL10 rs1800896, IL1A rs2856838, but not SEMA3C rs4461841, polymorphisms were associated with decreased risk of malaria in the controls. INTERPRETATION: Our results support a causal effect of malaria infection on eBL.

Malaria, Epstein-Barr virus infection and the pathogenesis of Burkitt's lymphoma.

A geographical and causal connection has long been recognized between malaria, Epstein-Barr virus (EBV) infection and Burkitt's lymphoma (BL), but the underlying mechanisms remain obscure. Potential clues are that the malaria parasite Plasmodium falciparum selectively absorbs vitamin A from the host and depends on it for its biological activities; secondly, alterations in vitamin A (retinoid) metabolism have been implicated in many forms of cancer, including BL. The first author has proposed that the merozoite-stage malaria parasite, emerging from the liver, uses its absorbed vitamin A as a cell membrane destabilizer to invade the red blood cells, causing anemia and other signs and symptoms of the disease as manifestations of an endogenous form of hypervitaminosis A (Mawson AR, Path Global Health 2013;107(3):122-9). Repeated episodes of malaria would therefore be expected to expose the tissues of affected individuals to potentially toxic doses of vitamin A. It is proposed that such episodes activate latent EBV infection, which in turn activates retinoid-responsive genes. Expression of these genes enhances viral replication and induces germinal center (GC) B cell expansion, activation-induced cytidine deaminase (AID) expression, and c-myc translocation, which in turn predisposes to BL. Thus, an endogenous form of retinoid toxicity related to malaria infection may be the common factor linking frequent malaria, EBV infection and BL, whereby prolonged exposure of lymphatic tissues to high concentrations of retinoids may combine to induce B-cell translocation and increase the risk of Burkitt's lymphoma.

Burkitt lymphoma expresses oncofetal chondroitin sulfate without being a reservoir for placental malaria sequestration.

Burkitt lymphoma (BL) is a malignant disease, which is frequently found in areas with holoendemic Plasmodium falciparum malaria. We have previously found that the VAR2CSA protein is present on malaria-infected erythrocytes and facilitates a highly specific binding to the placenta. ofCS is absent in other non-malignant tissues and thus VAR2CSA generally facilitates parasite sequestration and accumulation in pregnant women. In this study, we show that the specific receptor for VAR2CSA, the oncofetal chondroitin sulfate (ofCS), is likewise present in BL tissue and cell lines. We therefore explored whether ofCS in BL could act as anchor site for VAR2CSA-expressing infected erythrocytes. In contrast to the placenta, we found no evidence of in vivo sequestering of infected erythrocytes in the BL tissue. Furthermore, we found VAR2CSA-specific antibody titers in children with endemic BL to be lower than in control children from the same malaria endemic region. The abundant presence of ofCS in BL tissue and the absence of ofCS in non-malignant tissue encouraged us to examine whether recombinant VAR2CSA could be used to target BL. We confirmed the binding of VAR2CSA to BL-derived cells and showed that a VAR2CSA drug conjugate efficiently killed the BL-derived cell lines in vitro. These results identify ofCS as a novel therapeutic BL target and highlight how VAR2CSA could be used as a tool for the discovery of novel approaches for directing BL therapy.

[Parasites and cancer: is there a causal link?] / Parasites et cancer : existe-t-il un lien ?

Over 20 % of cancers have infectious origins, including well-known examples of microbes such as viruses (HPV, EBV) and bacteria (H. pylori). The contribution of intracellular eukaryotic parasites to cancer etiology is largely unexplored. Epidemiological and clinical reports indicate that eukaryotic protozoan, such as intracellular apicomplexan that cause diseases of medical or economic importance, can be linked to various cancers: Theileria and Cryptosporidium induce host cell transformation while Plasmodium was linked epidemiologically to the "African lymphoma belt" over fifty years ago. These intracellular eukaryotic parasites hijack cellular pathways to manipulate the host cell epigenome, cellular machinery, signaling pathways and epigenetic programs and marks, such as methylation and acetylation, for their own benefit. In doing so, they tinker with the same pathways as those deregulated during cancer onset. Here we discuss how epidemiological evidence linking eukaryotic intracellular parasites to cancer onset are further strengthened by recent mechanistic studies in three apicomplexan parasites.

Puzzling and ambivalent roles of malarial infections in cancer development and progression.

Scientific evidence strongly suggests that parasites are directly or indirectly associated with carcinogenesis in humans. However, studies have also indicated that parasites or their products might confer resistance to tumour growth. Plasmodium protozoa, the causative agents of malaria, exemplify the ambivalent link between parasites and cancer. Positive relationships between malaria and virus-associated cancers are relatively well-documented; for example, malaria can reactivate the Epstein-Barr Virus, which is the known cause of endemic Burkitt lymphoma. Nevertheless, possible anti-tumour properties of malaria have also been reported and, interestingly, this disease has long been thought to be beneficial to patients suffering from cancers. Current knowledge of the potential pro- and anti-cancer roles of malaria suggests that, contrary to other eukaryotic parasites affecting humans, Plasmodium-related cancers are principally lymphoproliferative disorders and attributable to virus reactivation, whereas, similar to other eukaryotic parasites, the anti-tumour effects of malaria are primarily associated with carcinomas and certain sarcomas. Moreover, malarial infection significantly suppresses murine cancer growth by inducing both innate and specific adaptive anti-tumour responses. This review aims to present an update regarding the ambivalent association between malaria and cancer, and further studies may open future pathways to develop novel strategies for anti-cancer therapies.

Does EBV alter the pathogenesis of malaria?

Plasmodium falciparum infections have been implicated in immune deficiencies resulting in ineffective control of Epstein-Barr virus, thereby increasing the risk of endemic Burkitt lymphoma in children. However, the impact of Epstein-Barr virus infections on the development of immunity to P. falciparum has not been studied in depth. In this review, we examine novel findings from animal co-infection models and human immuno-epidemiologic studies to speculate on the impact of acute gammaherpesvirus co-infection on malarial disease severity. Children are often concurrently or sequentially infected with multiple pathogens, and this has implications for understanding the development of protective immunity as well as in the evaluation of vaccine efficacy.

A multifactorial role for P. falciparum malaria in endemic Burkitt's lymphoma pathogenesis.

Endemic Burkitt's lymphoma (eBL) arises from the germinal center (GC). It is a common tumor of young children in tropical Africa and its occurrence is closely linked geographically with the incidence of P. falciparum malaria. This association was noted more than 50 years ago. Since then we have learned that eBL contains the oncogenic herpes virus Epstein-Barr virus (EBV) and a defining translocation that activates the c-myc oncogene. However the link to malaria has never been explained. Here we provide evidence for a mechanism arising in the GC to explain this association. Accumulated evidence suggests that eBL arises in the GC when deregulated expression of AID (Activation-induced cytidine deaminase) causes a c-myc translocation in a cell latently infected with Epstein-Barr virus (EBV). Here we show that P. falciparum targets GC B cells via multiple pathways to increase the risk of eBL. 1. It causes deregulated expression of AID, thereby increasing the risk of a c-myc translocation. 2. It increases the number of B cells transiting the GC. 3. It dramatically increases the frequency of these cells that are infected with EBV and therefore protected from c-myc induced apoptosis. We propose that these activities combine synergistically to dramatically increase the incidence of eBL in individuals infected with malaria.

Role of parasites in cancer.

BACKGROUND: In areas of parasitic endemicity, the occurrence of cancer that is not frequent may be linked with parasitic infection. Epidemiological correlates between some parasitic infections and cancer is strong, suggesting a strong aetiological association. The common parasites associated with human cancers are schistosomiasis, malaria, liver flukes (Clonorchis sinenses, Opistorchis viverrini). OBJECTIVE: To review the pathology, literature and methods of diagnosis. METHOD: Literature review from peer reviewed Journals cited in PubMed and local journals. CONCLUSION: Parasites may serve as promoters of cancer in endemic areas of infection.

Recurrent Plasmodium falciparum malaria infections in Kenyan children diminish T-cell immunity to Epstein Barr virus lytic but not latent antigens.

Plasmodium falciparum malaria (Pf-malaria) and Epstein Barr Virus (EBV) infections coexist in children at risk for endemic Burkitt's lymphoma (eBL); yet studies have only glimpsed the cumulative effect of Pf-malaria on EBV-specific immunity. Using pooled EBV lytic and latent CD8+ T-cell epitope-peptides, IFN-γ ELISPOT responses were surveyed three times among children (10 months to 15 years) in Kenya from 2002-2004. Prevalence ratios (PR) and 95% confidence intervals (CI) were estimated in association with Pf-malaria exposure, defined at the district-level (Kisumu: holoendemic; Nandi: hypoendemic) and the individual-level. We observed a 46% decrease in positive EBV lytic antigen IFN-γ responses among 5-9 year olds residing in Kisumu compared to Nandi (PR: 0.54; 95% CI: 0.30-0.99). Individual-level analysis in Kisumu revealed further impairment of EBV lytic antigen responses among 5-9 year olds consistently infected with Pf-malaria compared to those never infected. There were no observed district- or individual-level differences between Pf-malaria exposure and EBV latent antigen IFN-γ response. The gradual decrease of EBV lytic antigen but not latent antigen IFN-γ responses after primary infection suggests a specific loss in immunological control over the lytic cycle in children residing in malaria holoendemic areas, further refining our understanding of eBL etiology.

The company malaria keeps: how co-infection with Epstein-Barr virus leads to endemic Burkitt lymphoma.

PURPOSE OF REVIEW: Co-infection with Plasmodium falciparum malaria and Epstein-Barr virus (EBV) are implicated in the cause of endemic Burkitt lymphoma (eBL), the most prevalent pediatric cancer in equatorial Africa. Although the causal association between EBV and eBL has been established, P. falciparum malaria's role is not as clearly defined. This review focuses on how malaria may disrupt EBV persistence and immunity. RECENT FINDINGS: Two mutually compatible theories have been proposed. One suggests that P. falciparum malaria induces polyclonal B-cell expansion and lytic EBV reactivation, leading to the expansion of latently infected B cells and the likelihood of a c-myc translocation, a hallmark of Burkitt lymphoma tumors. The other advocates that EBV-specific T-cell immunity is impaired during P. falciparum malaria co-infection, either as a cause or consequence of enhanced EBV replication, leading to loss of viral control. Advancements in our ability to query the complexity of human responses to infectious diseases have stimulated interest in eBL pathogenesis. SUMMARY: EBV is necessary but not sufficient to cause eBL. A more dynamic model encompasses incremental contributions from both chronic and acute P. falciparum malaria leading to alterations in EBV persistence and EBV-specific immunity that culminate in eBL. A better understanding of how P. falciparum malaria modifies EBV infections in children may allow us to anticipate reductions in eBL incidence coinciding with malaria control programs.

Endemic Burkitt's lymphoma as a polymicrobial disease: new insights on the interaction between Plasmodium falciparum and Epstein-Barr virus.

Despite the well-established relationship between endemic Plasmodium falciparum malaria and Epstein-Barr virus (EBV) infection in the genesis of endemic Burkitt's lymphoma (eBL), very little research has examined the interaction between these two pathogens. eBL, the most prevalent childhood cancer in equatorial Africa where malaria is holoendemic, is a high-grade B cell lymphoma characterized by a c-myc translocation and the consistent presence of EBV. After primary infection, EBV establishes a life-long persistent infection characterized by virus shedding into saliva. African children are infected early in life and most have sero-converted by 3 years of age while sero-conversion tends to occur later in developed countries. Acute and chronic malaria infections profoundly affect the B cell compartment, inducing polyclonal activation, hyper-gammaglobulinemia and a dramatic increase in the levels of circulating EBV. In this review we present and discuss recent data suggesting a molecular link between the parasite, the B cell and EBV and provide evidence that adds to the concept of polymicrobial disease pathogenesis in eBL. Following the observation of EBV reactivation in children living in malaria endemic areas and its relationship with acute malaria infection, we identified the cystein-rich inter-domain region 1 alpha (CIDR1 alpha) of the Plasmodium falciparum membrane protein 1 as a polyclonal B cell activator. CIDR1 alpha increases B cell survival and preferentially activates the memory compartment where EBV is known to persist. Analysis of the mechanisms of interaction between CIDR1 alpha and EBV in the context of B cells demonstrated that CIDR1 alpha induces virus production in the EBV-infected B cell line Akata and in latently infected primary B cells derived from the peripheral blood of healthy carriers and children with eBL. This is the first demonstration that EBV can be reactivated directly by another pathogen. Our results suggest that P. falciparum antigens such as PfEMP1 can directly induce EBV reactivation during malaria infections. The increased viral load and the concomitant polyclonal B cell activation with enhanced B cell survival may augment the risk of eBL development in children living in malaria-endemic areas.

Spatial distribution of Burkitt's lymphoma in Kenya and association with malaria risk.

Endemic Burkitt's lymphoma (BL) is the most common paediatric malignancy in equatorial Africa and was originally shown to occur at high-incidence rates in regions where malaria transmission is holoendemic. New ecological models of malaria that are based on both parasite prevalence and disease have been described. In this study, we examined district level data collected from paediatric BL cases in Kenya from 1988 through 1997 and assessed whether the distribution of district level incidence rates could be explained by new ecologic estimates of malaria risk. Chi-square tests and log-linear regression models were used to evaluate these associations. An association with tribe of origin as a factor also was examined. The 10-year average annual incidence rate (IR) for Kenya was 0.61 per 100,000 children. Incidence rates varied by malaria transmission intensity as follows: low malaria risk (BL IR = 0.39), arid/seasonal (0.25), highland (0.66), endemic coast (0.68), and endemic lake (1.23) (chi(2) = 11.32, P = 0.002). In a log-linear model, BL rates were 3.5 times greater in regions with chronic and intense malaria transmission intensity than in regions with no or sporadic malaria transmission (odds ratio = 3.47, 95% confidence interval = 1.30-9.30), regardless of tribe. Although crude tribe-specific incidence rates ranged between 0.0 and 3.26, tribe was not associated with BL after controlling for malaria. These findings support the aetiologic role of intense malaria transmission intensity in BL.

Endemic Burkitt's lymphoma: a polymicrobial disease?

Endemic Burkitt's lymphoma is the most common childhood cancer in equatorial Africa. Two ubiquitous human pathogens are thought to be responsible for the aetiology of this disease: Epstein-Barr virus and Plasmodium falciparum malaria. New data suggest how these two pathogens might interact to result in disease and provide insights into the emerging concepts of polymicrobial disease pathogenesis.