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

Viral Oncogenesis: Synergistic Role of Genome Integration and Persistence

Persistence is a strategy used by many viruses to evade eradication by the immune system, ensuring their permanence and transmission within the host and optimizing viral fitness. During persistence, viruses can trigger various phenomena, including target organ damage, mainly due to an inflammatory state induced by infection, as well as cell proliferation and/or immortalization. In addition to immune evasion and chronic inflammation, factors contributing to viral persistence include low-level viral replication, the accumulation of viral mutants, and, most importantly, maintenance of the viral genome and reliance on viral oncoprotein production. This review focuses on the process of genome integration, which may occur at different stages of infection (e.g., HBV), during the chronic phase of infection (e.g., HPV, EBV), or as an essential part of the viral life cycle, as seen in retroviruses (HIV, HTLV-1). It also explores the close relationship between integration, persistence, and oncogenesis. Several models have been proposed to describe the genome integration process, including non-homologous recombination, looping, and microhomology models. Integration can occur either randomly or at specific genomic sites, often leading to genome destabilization. In some cases, integration results in the loss of genomic regions or impairs the regulation of oncogene and/or oncosuppressor expression, contributing to tumor development.

How Epstein Barr Virus Causes Lymphomas

Since Epstein-Barr Virus (EBV) was isolated 60 years ago, it has been studied clinically, epidemiologically, immunologically, and molecularly in the ensuing years. These combined studies allow a broad mechanistic understanding of how this ubiquitous human pathogen which infects more than 90% of adults can rarely cause multiple types of lymphomas. We survey these findings to provide a coherent description of its oncogenesis.

The Nociceptive and Inflammatory Responses Induced by the Ehrlich Solid Tumor Are Changed in Mice Healed of Plasmodium berghei Strain ANKA Infection after Chloroquine Treatment

Comorbidities that involve infectious and noninfectious diseases, such as malaria and cancer, have been described. Cancer and malaria induce changes in the nociceptive and inflammatory responses through similar pathophysiological mechanisms. However, it is unclear whether malaria and antimalarial treatment can change the inflammatory and nociceptive responses induced by solid cancer. Therefore, the present study experimentally evaluated the effect of infection by Plasmodium berghei strain ANKA and chloroquine treatment on the nociceptive and inflammatory responses induced by the solid Ehrlich tumor in male BALB/c mice. On the 1st experimental day, mice were infected with Plasmodium berghei and injected with tumor cells in the left hind paw. From the 7th to the 9th experimental day, mice were treated daily with chloroquine. The parasitemia was evaluated on the 7th and 10th days after infection. On the 11th experimental day, mice were evaluated on the von Frey filament test, the hot plate test, and the paw volume test. At the end of the experimental tests on the 11th day, the peripheral blood of all mice was collected for dosing of IL-1β and TNF-α. The blood parasitemia significantly increased from the 7th to the 10th day. The chloroquine treatment significantly decreased the parasitemia on the 10th day. The presence of the tumor did not significantly change the parasitemia on the 7th and 10th days in mice treated and nontreated with chloroquine. On the 11th day, the mechanical and thermal nociceptive responses significantly increased in mice with tumors. The treatment with antimalarial significantly reduced the mechanical nociceptive response induced by tumors. The hyperalgesia induced by tumors did not change with malaria. The mechanical and thermal hyperalgesia induced by the tumor was significantly reduced in mice treated and healed from malaria. On the 11th day, the volume of the paw injected by the tumor was significantly increased. The mice treated with chloroquine, infected with malaria, or healed of malaria showed reduced paw edema induced by the tumor. Mice with tumors did not show a change in IL-β and TNF-α serum levels. Mice with tumors showed a significant increase in serum levels of IL-1β but not TNF-α when treated with chloroquine, infected with malaria, or healed of malaria. In conclusion, the results show that malaria infection and chloroquine treatment can influence, in synergic form, the nociceptive and inflammatory responses induced by the solid tumor. Moreover, the mechanical antinociception, the thermal hyperalgesia, and the antiedema effect observed in mice treated with chloroquine and healed from malaria can be related to the increase in the serum level of IL-1β.

PfEMP1 and var genes - Still of key importance in Plasmodium falciparum malaria pathogenesis and immunity

The most severe form of malaria, caused by infection with Plasmodium falciparum parasites, continues to be an important cause of human suffering and poverty. The P. falciparum erythrocyte membrane protein 1 (PfEMP1) family of clonally variant antigens, which mediates the adhesion of infected erythrocytes to the vascular endothelium in various tissues and organs, is a central component of the pathogenesis of the disease and a key target of the acquired immune response to malaria. Much new knowledge has accumulated since we published a systematic overview of the PfEMP1 family almost ten years ago. In this chapter, we therefore aim to summarize research progress since 2015 on the structure, function, regulation etc. of this key protein family of arguably the most important human parasite. Recent insights regarding PfEMP1-specific immune responses and PfEMP1-specific vaccination against malaria, as well as an outlook for the coming years are also covered.

Modulation of Epstein-Barr-Virus (EBV)-Associated Cancers by Co-Infections

The oncogenic and persistent Epstein Barr virus (EBV) is carried by more than 95% of the human adult population. While asymptomatic in most of these, EBV can cause a wide variety of malignancies of lymphoid or epithelial cell origin. Some of these are also associated with co-infections that either increase EBV-induced tumorigenesis or weaken its immune control. The respective pathogens include Kaposi-sarcoma-associated herpesvirus (KSHV), Plasmodium falciparum and human immunodeficiency virus (HIV). In this review, I will discuss the respective tumor entities and possible mechanisms by which co-infections increase the EBV-associated cancer burden. A better understanding of the underlying mechanisms could allow us to identify crucial features of EBV-associated malignancies and defects in their immune control. These could then be explored to develop therapies against the respective cancers by targeting EBV and/or the respective co-infections with pathogen-specific therapies or vaccinations.

Distinctive Kaposi Sarcoma-Associated Herpesvirus Serological Profile during Acute Plasmodium falciparum Malaria Episodes

The seroprevalence of Kaposi sarcoma-associated herpesvirus (KSHV) and the incidence of endemic Kaposi sarcoma (KS) overlap with regions of malaria endemicity in sub-Saharan Africa. Multiple studies have shown an increased risk of KSHV seroconversion in children from high malaria compared to low malaria regions; however, the impact of acute episodes of Plasmodium falciparum (P. falciparum) malaria on KSHV's biphasic life cycle and lytic reactivation has not been determined. Here, we examined KSHV serological profiles and viral loads in 134 children with acute malaria and 221 healthy children from high malaria regions in Kisumu, as well as 77 healthy children from low malaria regions in Nandi. We assayed KSHV, Epstein-Barr virus (EBV), and P. falciparum malaria antibody responses in these three by multiplexed Luminex assay. We confirmed that KSHV seroprevalence was significantly associated with malaria endemicity (OR = 1.95, 1.18-3.24 95% CI, p = 0.01) with 71-77% seropositivity in high-malaria (Kisumu) compared to 28% in low-malaria (Nandi) regions. Furthermore, KSHV serological profiles during acute malaria episodes were distinct from age-matched non-malaria-infected children from the same region. Paired IgG levels also varied after malaria treatment, with significantly higher anti-ORF59 at day 0 but elevated ORF38, ORF73, and K8.1 at day 3. Acute malaria episodes is characterized by perturbation of KSHV latency in seropositive children, providing further evidence that malaria endemicity contributes to the observed increase in endemic KS incidence in sub-Saharan Africa.

Spatial distribution of incident pediatric Burkitt lymphoma in central and northern Malawi and association with malaria prevalence

BACKGROUND

Burkitt lymphoma (BL) accounts for 90% of pediatric lymphomas in sub-Saharan Africa. Plasmodium falciparum malaria is considered an etiological factor of BL. We describe the geographic distribution of pediatric BL in Malawi and association with P. falciparum malaria prevalence rate (PfPR).

METHODS

We enrolled 220 pathologically confirmed incident pediatric BL cases (2013-2018) into an observational clinical cohort at Kamuzu Central Hospital (KCH) in Lilongwe district. KCH is the main tertiary cancer referral center serving the central and northern regions of Malawi. Using an ecological study design, we calculated district-level annual BL incidence rate using census population estimates. District-level PfPR was extracted from the National Malaria Control Program 2010 report. BL incidence and PfPR maps were constructed in QGIS. Moran's I  test was used to identify BL spatial clusters. Pearson's correlation and multiple linear regression analyses were used to statistically examine the relationship between PfPR and BL.

RESULTS

BL incidence was higher in central region districts (8.2 cases per million) than northern districts (2.9 cases per million) and was elevated in lakeshore districts. Districts with elevated PfPR tended to have elevated BL incidence. A low-risk BL cluster was detected in the north. Statistically, BL incidence was positively correlated with PfPR (r = .77, p < .01). A 1% increase in PfPR predicted an increase in BL incidence of 0.2 cases per million (p = .03), when controlling for travel time from referral district hospital to KCH.

CONCLUSION

Our study supports evidence for an association between P. falciparum and BL and highlights a need to improve geographic accessibility to tertiary cancer services in Malawi's northern region.

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.

A brief overview of the Epstein Barr virus and its association with Burkitt's lymphoma

Epstein Barr virus (EBV) is known as an oncovirus and associates with several human malignancies such as Burkitt's lymphoma, other non-Hodgkin lymphomas, nasopharyngeal carcinoma, Hodgkin's disease, gastric adenocarcinoma, etc. in Burkitt's lymphoma, and the key event is the translocation of MYC gene, that increase of cell survival and aberrant expression of MYC gene. The biology of EBV and its function in the development of Burkitt's lymphoma are discussed in this review

Promising effects of parasite-derived compounds on tumor regression: a systematic review of in vitro and in vivo studies

The parasites are repeatedly confronting their host to take advantage of nutrients for multiplication and survival. In this sense, a wide spectrum of molecules is released from both sides, with immune-regulatory activity, accompanying this biological battle. Such parasites and their valuable molecules can be directed toward microbial-based cancer therapy. Herein, we contrived a systematic review to gather information on the antitumor activity of parasite-derived compounds. Following systematic search in Web of Science, ScienceDirect, Scopus, PubMed, ProQuest and Embase until 31 December 2019, a total number of 51 articles (54 datasets) were finally included in this review. Thirteen parasitic agents were found to possess possible antitumor activity, comprising protozoan species Toxoplasma gondii, Trypanosoma cruzi, Trichomonas vaginalis, Acanthamoeba castellanii, Besnoitia jellisoni, Leishmania major, Plasmodium yoelii, and Plasmodium lophurae, as well as parasitic helminths Toxocara canis, Echinococcus granulosus, Taenia crassiceps, Trichinella spiralis, and Schistosoma mansoni. Most experiments were done based on antigenic preparations from T. gondii (16 studies), E. granulosus (10 studies), T. spiralis (8 studies), and T. cruzi (6 studies). Possible antitumor properties of the selected parasites were revealed in this review. However, precise molecular basis of anticancer activity for each parasite remains to be elucidated in the future.

How Does Epstein–Barr Virus Interact With Other Microbiomes in EBV-Driven Cancers?

The commensal microbiome refers to a large spectrum of microorganisms which mainly consists of viruses and bacteria, as well as some other components such as protozoa and fungi. Epstein–Barr virus (EBV) is considered as a common component of the human commensal microbiome due to its spread worldwide in about 95% of the adult population. As the first oncogenic virus recognized in human, numerous studies have reported the involvement of other components of the commensal microbiome in the increasing incidence of EBV-driven cancers. Additionally, recent advances have also defined the involvement of host–microbiota interactions in the regulation of the host immune system in EBV-driven cancers as well as other circumstances. The regulation of the host immune system by the commensal microbiome coinfects with EBV could be the implications for how we understand the persistence and reactivation of EBV, as well as the progression of EBV-associated cancers, since majority of the EBV persist as asymptomatic carrier. In this review, we attempt to summarize the possible mechanisms for EBV latency, reactivation, and EBV-driven tumorigenesis, as well as casting light on the role of other components of the microbiome in EBV infection and reactivation. Besides, whether novel microbiome targeting strategies could be applied for curing of EBV-driven cancer is discussed as well.

Estimating the global burden of Epstein-Barr virus-related cancers

BACKGROUND

More than 90% of the adult population globally is chronically infected by the Epstein-Barr virus (EBV). It is well established that EBV is associated with a number of malignancies, and advances in knowledge of EBV-related malignancies are being made every year. Several studies have analysed the global epidemiology and geographic distribution of EBV-related cancers. However, most have only described a single cancer type or subtype in isolation or limited their study to the three or four most common EBV-related cancers. This review will present an overview on the spectrum of cancers linked to EBV based on observations of associations and proportions in the published literature while also using these observations to estimate the incidence and mortality burden of some of these cancers.

METHOD

We have reviewed the literature on defining features, distribution and outcomes across six cancers with a relatively large EBV-related case burden: Nasopharyngeal carcinoma (NPC), Gastric carcinoma (GC), Hodgkin lymphoma (HL), Burkitt lymphoma (BL), Diffuse large B-cell lymphoma (DLBCL) and Extranodal NK/T-cell lymphoma, Nasal type (ENKTL-NT). We retrieved published region-specific EBV-related case proportions for NPC, GC, HL and BL and performed meta-analyses on pooled region-specific studies of EBV-related case proportions for DLBCL and ENKTL-NT. We match these pooled proportions with their respective regional incidence and mortality numbers retrieved from a publicly available cancer database. Additionally, we also reviewed the literature on several other less common EBV-related cancers to summarize their key characteristics herein.

CONCLUSION

We estimated that EBV-related cases from these six cancers accounted for 239,700-357,900 new cases and 137,900-208,700 deaths in 2020. This review highlights the significant global impact of EBV-related cancers and extends the spectrum of disease that could benefit from an EBV-specific therapeutic.

Plasma EBV DNA: A Promising Diagnostic Marker for Endemic Burkitt Lymphoma

Endemic Burkitt lymphoma (eBL) is the most common childhood cancer in regions of equatorial Africa where P. falciparum malaria is holoendemic. The tumor is consistently associated with Epstein-Barr virus (EBV). Screening for EBV DNA in plasma in a high-risk population in Hong Kong has been shown to be useful in facilitating the early diagnosis of nasopharyngeal carcinoma, another EBV-associated tumor. Here, we investigate plasma EBV as a diagnostic marker for eBL in children in Uganda. We studied plasma specimens from 25 children with eBL and 25 controls matched for age (<3-16 years), gender and geography, including many with asymptomatic P. falciparum infection. These specimens were previously collected under the auspices of the EMBLEM (Epidemiology of Burkitt lymphoma in East African children and minors) study. After cell-free DNA isolation, plasma EBV DNA was measured using a quantitative PCR assay that amplifies the large internal repeats of the EBV genome. All children with eBL had measurable plasma EBV, as compared to 84% of control children. The median plasma EBV DNA level was 5.23 log₁₀ copies/mL (interquartile range 3.54-6.08 log₁₀ copies/mL) in children with eBL. In contrast, the median plasma EBV DNA level was 0.37 log₁₀ copies/mL (interquartile range 0.18-1.05 log₁₀ copies/mL) in children without lymphoma. An EBV threshold of 2.52 log₁₀ copies/mL yielded a sensitivity of.88 and a specificity of 1. The estimated AUC was 0.936 (95% CI: 0.8496 – 1.00) for the corresponding ROC curve. Plasma EBV copy number did not depend on age, gender, or malaria screening status. However, two control children with asymptomatic P. falciparum infection and parasitemia also had high plasma EBV copy number. Our analysis suggests that measurements of EBV copy number in plasma may be useful in identifying children with eBL versus control children. A promising area for future research is the differentiation of high copy number associated with tumor versus high copy number associated with asymptomatic parasitemia.

Quantitative cytokine level of TNF-α, IFN-γ, IL-10, TGF-β and circulating Epstein-Barr virus DNA load in individuals with acute Malaria due to P. falciparum or P. vivax or double infection in a Malaria endemic region in Indonesia

Plasmodium falciparum Malaria and Epstein-Barr Virus (EBV) infection are risk factors in the development of Burkitt’s lymphoma. In Indonesia, 100% of the population is persistently infected with EBV early in life and at risk of developing EBV-linked cancers. Currently, 10.7 million people in Indonesia are living in Malaria-endemic areas. This cross-sectional study was initiated to investigate how acute Malaria dysregulates immune control over latent EBV infection. Using blood and plasma samples of 68 patients with acute Malaria and 27 healthy controls, we measured the level of parasitemia for each plasmodium type (P. falciparum, P. vivax, and mixed) by microscopy and rapid test. The level of 4 regulatory cytokines was determined by quantitative ELISA and the level of circulating EBV genome by real-time PCR targeting the single copy EBNA-1 sequence. All Plasmodium-infected cases had high-level parasitemia (>1000 parasites/ul blood) except for one case. EBV-DNA levels were significantly more elevated in P. falciparum and P. vivax infections (P<0.05) compared to controls. EBV-DNA levels were not related to age, gender, Malaria symptoms, or plasmodium type. TNF-α and IL-10 levels were increased in Malaria cases versus controls, but IFN-γ and TGF- β levels were comparable between the groups. Only TNF-α levels in P. falciparum cases showed a clear correlation with elevated EBV DNA levels (R² = 0.8915). This is the first study addressing the relation between EBV (re)activation and cytokine responses during acute Malaria, revealing a clear correlation between pro-inflammatory cytokine TNF-α and EBV-DNA levels, specifically in P. falciparum cases, suggesting this cytokine to be key in dysregulating EBV homeostasis during acute P. falciparum Malaria.

Modification of EBV-Associated Pathologies and Immune Control by Coinfections

The oncogenic Epstein–Barr virus (EBV) persistently infects more than 95% of the human adult population. Even so it can readily transform human B cells after infection in vitro, it only rarely causes tumors in patients. A substantial proportion of the 1% of all human cancers that are associated with EBV occurs during coinfections, including those with the malaria parasite Plasmodium falciparum, the human immunodeficiency virus (HIV), and the also oncogenic and closely EBV-related Kaposi sarcoma-associated herpesvirus (KSHV). In this review, I will discuss how these infections interact with EBV, modify its immune control, and shape its tumorigenesis. The underlying mechanisms reveal new aspects of EBV-associated pathologies and point toward treatment possibilities for their prevention by the human immune system.

The Role of Coinfections in the EBV-Host Broken Equilibrium

The Epstein–Barr virus (EBV) is a well-adapted human virus, and its infection is exclusive to our species, generally beginning in the childhood and then persisting throughout the life of most of the affected adults. Although this infection generally remains asymptomatic, EBV can trigger life-threatening conditions under unclear circumstances. The EBV lifecycle is characterized by interactions with other viruses or bacteria, which increases the probability of awakening its pathobiont capacity. For instance, EBV infects B cells with the potential to alter the germinal center reaction (GCR)—an adaptive immune structure wherein mutagenic-driven processes take place. HIV- and Plasmodium falciparum-induced B cell hyperactivation also feeds the GCR. These agents, along with the B cell tropic KSHV, converge in the ontogeny of germinal center (GC) or post-GC lymphomas. EBV oral transmission facilitates interactions with local bacteria and HPV, thereby increasing the risk of periodontal diseases and head and neck carcinomas. It is less clear as to how EBV is localized in the stomach, but together with Helicobacter pylori, they are known to be responsible for gastric cancer. Perhaps this mechanism is reminiscent of the local inflammation that attracts different herpesviruses and enhances graft damage and chances of rejection in transplanted patients. In this review, we discussed the existing evidence suggestive of EBV possessing the potential to synergize or cooperate with these agents to trigger or worsen the disease.

Interplay between Epstein-Barr virus infection and environmental xenobiotic exposure in cancer

Epstein-Barr virus (EBV) is a herpesvirus associated with lymphoid and epithelial malignancies. Both B cells and epithelial cells are susceptible and permissive to EBV infection. However, considering that 90% of the human population is persistently EBV-infected, with a minority of them developing cancer, additional factors are necessary for tumor development. Xenobiotics such as tobacco smoke (TS) components, pollutants, pesticides, and food chemicals have been suggested as cofactors involved in EBV-associated cancers. In this review, the suggested mechanisms by which xenobiotics cooperate with EBV for carcinogenesis are discussed. Additionally, a model is proposed in which xenobiotics, which promote oxidative stress (OS) and DNA damage, regulate EBV replication, promoting either the maintenance of viral genomes or lytic activation, ultimately leading to cancer. Interactions between EBV and xenobiotics represent an opportunity to identify mechanisms by which this virus is involved in carcinogenesis and may, in turn, suggest both prevention and control strategies for EBV-associated cancers.

Natural Killer Cell Responses during Human γ-Herpesvirus Infections

Herpesviruses are main sculptors of natural killer (NK) cell repertoires. While the β-herpesvirus human cytomegalovirus (CMV) drives the accumulation of adaptive NKG2C-positive NK cells, the human γ-herpesvirus Epstein–Barr virus (EBV) expands early differentiated NKG2A-positive NK cells. While adaptive NK cells support adaptive immunity by antibody-dependent cellular cytotoxicity, NKG2A-positive NK cells seem to preferentially target lytic EBV replicating B cells. The importance of this restriction of EBV replication during γ-herpesvirus pathogenesis will be discussed. Furthermore, the modification of EBV-driven NK cell expansion by coinfections, including by the other human γ-herpesvirus Kaposi sarcoma-associated herpesvirus (KSHV), will be summarized.

Malaria Infection and Risk for Endemic Burkitt Lymphoma: A Systematic Review and Meta-Analysis

Background: Malaria infection is reportedly linked to endemic Burkitt lymphoma (eBL) in malaria-endemic areas. This study aimed to pool the overall risk (or odds) of eBL among children with previous or concurrent malaria infection. Methods: We searched PubMed, Web of Science, Scopus, and reference lists of publications for potentially relevant studies on malaria infection and eBL. The quality of the included studies was assessed using the Joanna Briggs Institute for case-control studies. Random-effects meta-analysis was used to summarize whether the odds of eBL can be increased by (1) malaria infection or (2) elevated titer of IgGs to malaria antigen. The level of heterogeneity was evaluated using Cochran’s Q statistic and I². The individual study data, pooled odds, and confidence interval (CI) were illustrated using the forest plot. Publication bias was assessed using funnel plots and Egger’s test. Results: Ten studies were included, reporting the number of malaria cases in eBL and non-eBL (5 studied malaria infection and the odds of eBL; five studied the burden of IgGs to malarial antigens and the odds of eBL). According to the meta-analysis results, the odds of eBL was not increased by malaria infection (p = 0.562, OR: 0.87, 95% CI: 0.54–1.39, I²: 93.5%, malaria in eBL: 604/1506 cases, malaria in non-eBL: 2117/4549 cases) and the elevated titer of IgGs to malaria antigen (p = 0.051, OR: 1.50, 95% CI: 1.00–2.25, I²: 89%, increased IgG titer in eBL: 1059/1736 cases, increased IgG titer in non-eBL: 847/1722 cases). In meta-regression analysis, sex was not a confounding factor for the effect size of malaria infection and eBL (p = 0.10) and that of increased IgGs and eBL (p = 0.80). Conclusions: Malaria infection and IgG titer elevation did not increase the risk for eBL among children. However, the included studies, which are only few, do not generally agree on this point. Therefore, the risk for eBL in children diagnosed with malaria should be investigated further by longitudinal studies to confirm our evidence-based approach.

Roles of Lytic Viral Replication and Co-Infections in the Oncogenesis and Immune Control of the Epstein-Barr Virus

Epstein-Barr virus (EBV) is the prototypic human tumor virus whose continuous lifelong immune control is required to prevent lymphomagenesis in the more than 90% of the human adult population that are healthy carriers of the virus. Here, we review recent evidence that this immune control has not only to target latent oncogenes, but also lytic replication of EBV. Furthermore, genetic variations identify the molecular machinery of cytotoxic lymphocytes as essential for this immune control and recent studies in mice with reconstituted human immune system components (humanized mice) have begun to provide insights into the mechanistic role of these molecules during EBV infection. Finally, EBV often does not act in isolation to cause disease. Some of EBV infection-modulating co-infections, including human immunodeficiency virus (HIV) and Kaposi sarcoma-associated herpesvirus (KSHV), have been modeled in humanized mice. These preclinical in vivo models for EBV infection, lymphomagenesis, and cell-mediated immune control do not only promise a better understanding of the biology of this human tumor virus, but also the possibility to explore vaccine candidates against it.

Malaria and risk of lymphoid neoplasms and other cancer: a nationwide population-based cohort study

BACKGROUND

Malaria is associated with Burkitt lymphoma among children in Sub-Saharan Africa. No longitudinal studies have assessed the long-term risk of other lymphoma or cancer overall. Here, we investigated the risk of lymphoid neoplasms and other cancer after malaria.

METHODS

We included 4125 patients diagnosed with malaria in Sweden in 1987-2015, identified either through the National Surveillance Database at the Public Health Agency of Sweden, the National Inpatient and Outpatient Register, or by reports from microbiology departments. A comparator cohort (N = 66,997) matched on sex, age and birth region was retrieved from the general population and an additional cohort with all individuals born in Sub-Saharan Africa registered in the Total Population Register in 1987-2015 (N = 171,756). Incident lymphomas and other cancers were identified through linkage with the Swedish Cancer Register. Hazard ratios (HRs) were assessed using Cox regression with attained age as the timescale.

RESULTS

A total of 20 lymphoid neoplasms and 202 non-haematological cancers were identified among malaria patients during a mean follow-up of 13.3 and 13.7 years, respectively. The overall risk of lymphoid neoplasms was not significantly increased (hazard ratio [HR] 1.24, 95% confidence interval [CI] 0.79-1.94), neither did we find any association with all-site non-haematological cancer (HR 0.89, 95% CI 0.77-1.02). However, in the Sub-Saharan Africa cohort, we observed an increased risk of lymphoid neoplasms after malaria diagnosis (HR 2.39, 95% CI 1.06-5.40), but no difference in the risk of other cancer (HR 1.01, 95% CI 0.70-1.45). The association could not be explained by co-infection with HIV or chronic hepatitis B or C, since the risk estimate was largely unchanged after excluding patients with these comorbidities (HR 2.63, 95% CI 1.08-6.42). The risk became more pronounced when restricting analyses to only including non-Hodgkin and Hodgkin lymphomas (HR 3.49, 95% CI 1.42-8.56).

CONCLUSION

Individuals born in malaria-endemic areas and diagnosed with malaria in Sweden had an increased risk of lymphoid neoplasms, especially B cell lymphoma. There was no association with cancer overall nor did single malaria episodes confer an increased risk in travellers.

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.