Malaria resistance genes are associated with the levels of IgG subclasses directed against Plasmodium falciparum blood-stage antigens in Burkina Faso

Uncovering lupus nephritis-specific genes and the potential of TNFRSF17-targeted immunotherapy: a high-throughput sequencing study

Introduction

Lupus nephritis (LN) is a severe manifestation of systemic lupus erythematosus (SLE). This study aimed to identify LN specific-genes and potential therapeutic targets.

Methods

We performed high-throughput transcriptome sequencing on peripheral blood mononuclear cells (PBMCs) from LN patients. Healthy individuals and SLE patients without LN were used as controls. To validate the sequencing results, qRT-PCR was performed for 5 upregulated and 5 downregulated genes. Furthermore, the effect of the TNFRSF17-targeting drug IBI379 on patient plasma cells and B cells was evaluated by flow cytometry.

Results

Our analysis identified 1493 and 205 differential genes in the LN group compared to the control and SLE without LN groups respectively, with 70 genes common to both sets, marking them as LN-specific. These LN-specific genes were significantly enriched in the 'regulation of biological quality' GO term and the cell cycle pathway. Notably, several genes including TNFRSF17 were significantly overexpressed in the kidneys of both LN patients and NZB/W mice. TNFRSF17 levels correlated positively with urinary protein levels, and negatively with complement C3 and C4 levels in LN patients. The TNFRSF17-targeting drug IBI379 effectively induced apoptosis in patient plasma cells without significantly affecting B cells.

Discussion

Our findings suggest that TNFRSF17 could serve as a potential therapeutic target for LN. Moreover, IBI379 is presented as a promising treatment option for LN.

Whole transcriptome analysis of HCT-8 cells infected by Cryptosporidium parvum

BACKGROUND

Cryptosporidium species are zoonotic protozoans that are important causes of diarrhoeal disease in both humans and animals. Non-coding RNAs (ncRNAs) play an important role in the innate immune defense against Cryptosporidium infection, but the underlying molecular mechanisms in the interaction between human ileocecal adenocarcinoma (HCT-8) cells and Cryptosporidium species have not been entirely revealed.

METHODS

The expression profiles of messenger RNAs (mRNAs), long non-coding RNAs (lncRNAs), microRNAs (miRNAs) and circular RNAs (circRNAs) in the early phase of infection of HCT-8 cells with Cryptosporidium parvum and at 3 and 12 h post infection were analyzed using the RNA-sequencing technique. The biological functions of differentially expressed RNAs (dif-RNAs) were discovered through Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. The targeting relationships between three ncRNAs and mRNAs were analyzed using bioinformatics methods, followed by building a competing endogenous RNA (ceRNA) regulatory network centered on miRNAs.

RESULTS

After strictly filtering the raw data, our analysis revealed 393 dif-lncRNAs, 69 dif-miRNAs and 115 dif-mRNAs at 3 hpi, and 450 dif-lncRNAs, 129 dif-miRNAs, 117 dif-mRNAs and one dif-circRNA at 12 hpi. Of these, 94 dif-lncRNAs, 24 dif-miRNAs and 22 dif-mRNAs were detected at both post-infection time points. Eleven dif-lncRNAs, seven dif-miRNAs, eight dif-mRNAs and one circRNA were randomly selected and confirmed using the quantitative real-time PCR. Bioinformatics analyses showed that the dif-mRNAs were significantly enriched in nutritional absorption, metabolic processes and metabolism-related pathways, while the dif-lncRNAs were mainly involved in the pathways related to the infection and pathogenicity of C. parvum (e.g. tight junction protein) and immune-related pathways (e.g. cell adhesion molecules). In contrast, dif-miRNAs and dif-circRNA were significantly enriched in apoptosis and apoptosis-related pathways. Among the downregulated RNAs, the miRNAs has-miR-324-3p and hsa-miR-3127-5p appear to be crucial miRNAs which could negatively regulate circRNA, lncRNA and mRNA.

CONCLUSIONS

The whole transcriptome profiles of HCT-8 cells infected with C. parvum were obtained in this study. The results of the GO and KEGG pathway analyses suggest significant roles for these dif-RNAs during the course of C. parvum infection. A ceRNA regulation network containing miRNA at its center was constructed for the first time, with hsa-miR-324-3p and hsa-miR-3127-5p being the crucial miRNAs. These findings provide novel insights into the responses of human intestinal epithelial cells to C. parvum infection.

New highly antigenic linear B cell epitope peptides from PvAMA-1 as potential vaccine candidates

Peptide-based vaccines have demonstrated to be an important way to induce long-lived immune responses and, therefore, a promising strategy in the rational of vaccine development. As to malaria, among the classic vaccine targets, the Apical membrane antigen (AMA-1) was proven to have important B cell epitopes that can induce specific immune response and, hence, became key players for a vaccine approach. The peptides selection was carried out using a bioinformatic approach based on Hidden Markov Models profiles of known antigens and propensity scale methods based on hydrophilicity and secondary structure prediction. The antigenicity of the selected B-cell peptides was assessed by multiple serological assays using sera from acute P.vivax infected subjects. The synthetic peptides were recognized by 45.5%, 48.7% and 32.2% of infected subjects for peptides I, II and III respectively. Moreover, when synthetized together (tripeptide), the reactivity increases up to 62%, which is comparable to the reactivity found against the whole protein PvAMA-1 (57%). Furthermore, IgG reactivity against the tripeptide after depletion was reduced by 42%, indicating that these epitopes may be responsible for a considerable part of the protein immunogenicity. These results represent an excellent perspective regarding future chimeric vaccine constructions that may come to contemplate several targets with the potential to generate the robust and protective immune response that a vivax malaria vaccine needs to succeed.

IgG acquisition against PfEMP1 PF11_0521 domain cassette DC13, DBLβ3_D4 domain, and peptides located within these constructs in children with cerebral malaria

The Plasmodium falciparum erythrocyte-membrane-protein-1 (PF3D7_1150400/PF11_0521) contains both domain cassette DC13 and DBLβ3 domain binding to EPCR and ICAM-1 receptors, respectively. This type of PfEMP1 proteins with dual binding specificity mediate specific interactions with brain micro-vessels endothelium leading to the development of cerebral malaria (CM). Using plasma collected from children at time of hospital admission and after 30 days, we study an acquisition of IgG response to PF3D7_1150400/PF11_0521 DC13 and DBLβ3_D4 recombinant constructs, and five peptides located within these constructs, specifically in DBLα1.7_D2 and DBLβ3_D4 domains. We found significant IgG responses against the entire DC13, PF11_0521_DBLβ3_D4 domain, and peptides. The responses varied against different peptides and depended on the clinical status of children. The response was stronger at day 30, and mostly did not differ between CM and uncomplicated malaria (UM) groups. Specifically, the DBLβ3 B3-34 peptide that contains essential residues involved in the interaction between PF11_0521 DBLβ3_D4 domain and ICAM-1 receptor demonstrated significant increase in reactivity to IgG1 and IgG3 antibodies at convalescence. Further, IgG reactivity in CM group at time of admission against functionally active (ICAM-1-binding) PF11_0521 DBLβ3_D4 domain was associated with protection against severe anemia. These results support development of vaccine based on the PF3D7_1150400/PF11_0521 structures to prevent CM.

Genetics of Malaria Inflammatory Responses: A Pathogenesis Perspective

Despite significant progress in combating malaria in recent years the burden of severe disease and death due to Plasmodium infections remains a global public health concern. Only a fraction of infected people develops severe clinical syndromes motivating a longstanding search for genetic determinants of malaria severity. Strong genetic effects have been repeatedly ascribed to mutations and allelic variants of proteins expressed in red blood cells but the role of inflammatory response genes in disease pathogenesis has been difficult to discern. We revisited genetic evidence provided by inflammatory response genes that have been repeatedly associated to malaria, namely TNF, NOS2, IFNAR1, HMOX1, TLRs, CD36, and CD40LG. This highlighted specific genetic variants having opposing roles in the development of distinct malaria clinical outcomes and unveiled diverse levels of genetic heterogeneity that shaped the complex association landscape of inflammatory response genes with malaria. However, scrutinizing genetic effects of individual variants corroborates a pathogenesis model where pro-inflammatory genetic variants acting in early infection stages contribute to resolve infection but at later stages confer increased vulnerability to severe organ dysfunction driven by tissue inflammation. Human genetics studies are an invaluable tool to find genes and molecular pathways involved in the inflammatory response to malaria but their precise roles in disease pathogenesis are still unexploited. Genome editing in malaria experimental models and novel genotyping-by-sequencing techniques are promising approaches to delineate the relevance of inflammatory response gene variants in the natural history of infection thereby will offer new rational angles on adjuvant therapeutics for prevention and clinical management of severe malaria.

Host genetic polymorphisms and serological response against malaria in a selected population in Sri Lanka

BACKGROUND

Antibodies against the merozoite surface protein 1-19 (MSP1-19) and the apical membrane antigen 1 (AMA1) of the malaria parasite (Plasmodium vivax) are proven to be important in protection against clinical disease. Differences in the production/maintenance of antibodies may be due to many factors including host genetics. This paper discusses the association of 4 anti-malarial antibodies with selected host genetic markers.

METHODS

Blood was collected from individuals (n = 242) with a history of malaria within past 15 years for DNA and serum. ELISA was carried out for serum to determine the concentration of anti-malarial antibodies MSP1-19 and AMA1 for both vivax and falciparum malaria. 170 SNPs related to malaria were genotyped. Associations between seropositivity, antibody levels and genetic, non-genetic factors were determined.

RESULTS

Age ranged 13-74 years (mean age = 40.21 years). Majority were females. Over 90% individuals possessed either one or more type(s) of anti-malarial antibodies. Five SNPs were significantly associated with seropositivity. One SNP was associated with MSP1-19_Pv(rs739718); 4 SNPs with MSP1-19_Pf (rs6874639, rs2706379, rs2706381 and rs2075820) and1 with AMA1_Pv (rs2075820). Eleven and 7 genotypes (out of 15) were significantly associated with either presence or absence of antibodies. Three SNPs were found to be significantly associated with the antibody levels viz. rs17411697 with MSP1-19_Pv, rs2227491 with AMA1_Pv and rs229587 with AMA1_Pf. Linkage of the markers in the two groups was similar, but lower LOD scores were observed in seropositives compared to seronegatives.

DISCUSSION AND CONCLUSIONS

The study suggests that several SNPs in the human genome that exist in Sri Lankan populations are significantly associated with anti-malarial antibodies, either with generation and/or maintenance of antibodies for longer periods, which can be due to either individual polymorphisms or most probably a combined effect of the markers.

IgG subclass responses to excreted-secreted antigens of Plasmodium falciparum in a low-transmission malaria area of the Peruvian Amazon

Background

Malaria in Peru is concentrated in the Amazon region, especially in Loreto, and transmission is focused in rural and peri-urban communities. The government has approved a malaria elimination plan with a community approach and seeks to reduce the risk of transmission through preventive interventions, but asymptomatic and low-parasite-density infections are challenges for disease control and elimination. IgG antibodies play a critical role in combating infection through their ability to reduce parasitaemia and clinical symptoms. In particular, IgG subclasses have important roles in controlling malaria disease and may provide new insight into the development of malaria control strategies and understanding of malaria transmission. Through the use of excreted-secreted antigens from Plasmodium falciparum, were evaluated the responses of the four IgG subclasses in symptomatic and asymptomatic malarial infections.

Results

Higher levels of whole IgG were observed in asymptomatic carriers (P < 0.05). IgG3 and IgG1 were the most prevalent subclasses and did not show differences in their antibody levels in either type of carrier. All symptomatic carriers were positive for IgG4, and the presence of IgG3 and IgG2 were correlated with protection against parasitaemia. IgG2 showed lower prevalence and antibody titers in comparison to other subclasses.

Conclusions

This is the first study that characterizes the IgG subclass response in the Peruvian Amazon, and these results show that even in populations from regions with low malaria transmission, a certain degree of naturally acquired immunity can develop when the right antibody subclasses are produced. This provides important insight into the potential mechanisms regulating protective immunity.

Electronic supplementary material

The online version of this article (10.1186/s12936-018-2471-6) contains supplementary material, which is available to authorized users.

Plasmodium vivax Cell-Traversal Protein for Ookinetes and Sporozoites: Naturally Acquired Humoral Immune Response and B-Cell Epitope Mapping in Brazilian Amazon Inhabitants

The cell-traversal protein for ookinetes and sporozoites (CelTOS), a highly conserved antigen involved in sporozoite motility, plays an important role in the traversal of host cells during the preerythrocytic stage of Plasmodium species. Recently, it has been considered an alternative target when designing novel antimalarial vaccines against Plasmodium falciparum. However, the potential of Plasmodium vivax CelTOS as a vaccine target is yet to be explored. This study evaluated the naturally acquired immune response against a recombinant P. vivax CelTOS (PvCelTOS) (IgG and IgG subclass) in 528 individuals from Brazilian Amazon, as well as the screening of B-cell epitopes in silico and peptide assays to associate the breadth of antibody responses of those individuals with exposition and/or protection correlates. We show that PvCelTOS is naturally immunogenic in Amazon inhabitants with 94 individuals (17.8%) showing specific IgG antibodies against the recombinant protein. Among responders, the IgG reactivity indexes (RIs) presented a direct correlation with the number of previous malaria episodes (p = 0.003; r = 0.315) and inverse correlation with the time elapsed from the last malaria episode (p = 0.031; r = −0.258). Interestingly, high responders to PvCelTOS (RI > 2) presented higher number of previous malaria episodes, frequency of recent malaria episodes, and ratio of cytophilic/non-cytophilic antibodies than low responders (RI < 2) and non-responders (RI < 1). Moreover, a high prevalence of the cytophilic antibody IgG1 over all other IgG subclasses (p < 0.0001) was observed. B-cell epitope mapping revealed five immunogenic regions in PvCelTOS, but no associations between the specific IgG response to peptides and exposure/protection parameters were found. However, the epitope (PvCelTOS_I136-E143) was validated as a main linear B-cell epitope, as 92% of IgG responders to PvCelTOS were also responders to this peptide sequence. This study describes for the first time the natural immunogenicity of PvCelTOS in Amazon individuals and identifies immunogenic regions in a full-length protein. The IgG magnitude was mainly composed of cytophilic antibodies (IgG1) and associated with recent malaria episodes. The data presented in this paper add further evidence to consider PvCelTOS as a vaccine candidate.

Cytokine gene polymorphisms are not associated with anti-PvDBP, anti-PvAMA-1 or anti-PvMSP-119 IgG antibody levels in a malaria-endemic area of the Brazilian Amazon

Background

The immune response against Plasmodium vivax immunogenic epitopes is regulated by pro- and anti-inflammatory cytokines that determine antibody levels and class switching. Cytokine gene polymorphisms may be responsible for changes in the humoral immune response against malaria. The aim of this study was to evaluate whether polymorphisms in the TNFA, IFNG and IL10 genes would alter the levels of anti-PvAMA1, PvDBP and -PvMSP-1₁₉ IgG antibodies in patients with vivax malaria.

Methods

Samples from 90 vivax malaria-infected and 51 uninfected subjects from an endemic area of the Brazilian Amazon were genotyped using polymerase chain reaction-restriction fragment length polymorphism (PCR–RFLP) to identify polymorphisms of the genes TNFA (−1031T > C, −308G > A, −238G > A), IFNG (+874T > A) and IL10 (−819C > T, −592C > A). The levels of total IgG against PvAMA1, PvDBP and PvMSP-1₁₉ were determined using an enzyme-linked immunosorbent assay (ELISA). Associations between the polymorphisms and the antibody response were assessed by means of logistic regression models.

Results

No significant differences were found in the levels of IgG antibodies against the PvAMA-1, PvDBP or PvMSP-1₁₉ proteins in relation to the studied polymorphisms.

Conclusions

Although no associations were found among the evaluated genotypes and alleles and anti-merozoite IgG class P. vivax antibody levels, this study helps elucidate the immunogenic profile involved in the humoral immune response in malaria.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-016-1414-3) contains supplementary material, which is available to authorized users.

Immunogenetic markers associated with a naturally acquired humoral immune response against an N-terminal antigen of Plasmodium vivax merozoite surface protein 1 (PvMSP-1)

Background

Humoral immune responses against proteins of asexual blood-stage malaria parasites have been associated with clinical immunity. However, variations in the antibody-driven responses may be associated with a genetic component of the human host. The objective of the present study was to evaluate the influence of co-stimulatory molecule gene polymorphisms of the immune system on the magnitude of the humoral immune response against a Plasmodium vivax vaccine candidate antigen.

Methods

Polymorphisms in the CD28, CTLA4, ICOS, CD40, CD86 and BLYS genes of 178 subjects infected with P. vivax in an endemic area of the Brazilian Amazon were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The levels of IgM, total IgG and IgG subclasses specific for ICB2-5, i.e., the N-terminal portion of P. vivax merozoite surface protein 1 (PvMSP-1), were determined by enzyme-linked immuno assay. The associations between the polymorphisms and the antibody response were assessed by means of logistic regression models.

Results

After correcting for multiple testing, the IgG1 levels were significantly higher in individuals recessive for the single nucleotide polymorphism rs3116496 in CD28 (p = 0.00004). Furthermore, the interaction between CD28 rs35593994 and BLYS rs9514828 had an influence on the IgM levels (p = 0.0009).

Conclusions

The results of the present study support the hypothesis that polymorphisms in the genes of co-stimulatory components of the immune system can contribute to a natural antibody-driven response against P. vivax antigens.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-016-1350-2) contains supplementary material, which is available to authorized users.

Naturally Acquired Antibody Responses to Plasmodium vivax and Plasmodium falciparum Merozoite Surface Protein 1 (MSP1) C-Terminal 19 kDa Domains in an Area of Unstable Malaria Transmission in Southeast Asia

Understanding naturally acquired immunity to infections caused by Plasmodia in different malaria endemicity settings is needed for better vaccine designs and for exploring antibody responses as a proxy marker of malaria transmission intensity. This study investigated the sero-epidemiology of malaria along the international border between China and Myanmar, where malaria elimination action plans are in place. This study recruited 233 P. vivax and 156 P. falciparum infected subjects with acute malaria at the malaria clinics and hospitals. In addition, 93 and 67 healthy individuals from the same endemic region or from non-endemic region, respectively, were used as controls. Acute malaria infections were identified by microscopy. Anti-recombinant PfMSP1₁₉ and PvMSP1₁₉ antibody levels were measured by ELISA. Antibody responses to respective MSP1₁₉ were detected in 50.9% and 78.2% patients with acute P. vivax and P. falciparum infections, respectively. There were cross-reacting antibodies in Plasmodium patients against these two recombinant proteins, though we could not exclude the possibility of submicroscopic mixed-species infections. IgG1, IgG3 and IgG4 were the major subclasses. Interestingly, 43.2% of the healthy endemic population also had antibodies against PfMSP1₁₉, whereas only 3.9% of this population had antibodies against PvMSP1₁₉. Higher antibody levels were correlated with age and parasite density, but not with season, gender or malaria history. Both total IgG and individual IgG subclasses underwent substantial declines during the convalescent period in three months. This study demonstrated that individuals in a hypoendemic area with coexistence of P. vivax and P. falciparum can mount rapid antibody responses against both PfMSP1₁₉ and PvMSP1₁₉. The significantly higher proportion of responders to PfMSP1₁₉ in the healthy endemic population indicates higher prevalence of P. falciparum in the recent past. Specific antibodies against PvMSP1₁₉ could serve as a marker of recent exposure to P. vivax in epidemiological studies.

Polymorphisms in B Cell Co-Stimulatory Genes Are Associated with IgG Antibody Responses against Blood-Stage Proteins of Plasmodium vivax

The development of an effective immune response can help decrease mortality from malaria and its clinical symptoms. However, this mechanism is complex and has significant inter-individual variation, most likely owing to the genetic contribution of the human host. Therefore, this study aimed to investigate the influence of polymorphisms in genes involved in the costimulation of B-lymphocytes in the naturally acquired humoral immune response against proteins of the asexual stage of Plasmodium vivax. A total of 319 individuals living in an area of malaria transmission in the Brazilian Amazon were genotyped for four SNPs in the genes CD40, CD40L, BLYS and CD86. In addition, IgG antibodies against P. vivax apical membrane antigen 1 (PvAMA–1), Duffy binding protein (PvDBP) and merozoite surface protein 1 (PvMSP–1₁₉) were detected by ELISA. The SNP BLYS –871C>T was associated with the frequency of IgG responders to PvAMA–1 and PvMSP–1₁₉. The SNP CD40 –1C>T was associated with the IgG response against PvDBP, whereas IgG antibody titers against PvMSP–1₁₉ were influenced by the polymorphism CD86 +1057G>A. These data may help to elucidate the immunological aspects of vivax malaria and consequently assist in the design of malaria vaccines.

Major Histocompatibility Complex and Malaria: Focus on Plasmodium vivax Infection

The importance of host and parasite genetic factors in malaria resistance or susceptibility has been investigated since the middle of the last century. Nowadays, of all diseases that affect man, malaria still plays one of the highest levels of selective pressure on human genome. Susceptibility to malaria depends on exposure profile, epidemiological characteristics, and several components of the innate and adaptive immune system that influences the quality of the immune response generated during the Plasmodium lifecycle in the vertebrate host. But it is well known that the parasite's enormous capacity of genetic variation in conjunction with the host genetics polymorphism is also associated with a wide spectrum of susceptibility degrees to complicated or severe forms of the disease. In this scenario, variations in genes of the major histocompatibility complex (MHC) associated with host resistance or susceptibility to malaria have been identified and used as markers in host-pathogen interaction studies, mainly those evaluating the impact on the immune response, acquisition of resistance, or increased susceptibility to infection or vulnerability to disease. However, due to the intense selective pressure, number of cases, and mortality rates, the majority of the reported associations reported concerned Plasmodium falciparum malaria. Studies on the MHC polymorphism and its association with Plasmodium vivax, which is the most widespread Plasmodium and the most prevalent species outside the African continent, are less frequent but equally important. Despite punctual contributions, there are accumulated evidences of human genetic control in P. vivax infection and disease. Herein, we review the current knowledge in the field of MHC and derived molecules (HLA Class I, Class II, TNF-α, LTA, BAT1, and CTL4) regarding P. vivax malaria. We discuss particularly the results of P. vivax studies on HLA class I and II polymorphisms in relation to host susceptibility, naturally acquired immune response against specific antigens and the implication of this knowledge to overcome the parasite immune evasion. Finally, the potential impact of such polymorphisms on the development of vaccine candidate antigens against P. vivax will be studied.

Clinical relevance of single nucleotide polymorphisms within the 13 cytokine genes in North Indian trauma hemorrhagic shock patients

INTRODUCTION

The susceptibility to adverse outcome from critical injury (occurrence of sepsis, septic shock, organ dysfunction/failure, and mortality) varies dramatically due to different degrees of inflammatory response. We assessed the relationship of the genotype distribution of various cytokine gene polymorphisms (CGP) with regard to the development of sepsis, organ dysfunction or mortality in severely injured patients.

METHOD

Observational, hospital-based cohort study of 114 severely injured North Indian patients from New Delhi admitted to the Emergency Department (ED) of Trauma Centre, AIIMS. Patients were monitored from day first to discharge or death, measuring SOFA score, sepsis and septic shock occurrences up to one month. We have analyzed 13 cytokine genes, including the SNPs of structural and regulatory regions at 22 positions.

RESULTS

Sequence-specific primer based PCR indicated that eight polymorphic loci IL-1α /-889, IL-1β/-511, IL-1R (pstI 1970), TGF-β/ code 10, TNF-α/-308, TNF-α/-238, IL-6/+565 and IL-10/-1082, out of 22 SNPs are significantly associated with sepsis morbidity and outcome. Theses SNPs might be used as risk determinants of the outcome. Patients with IL-10 (-1082A/A) genotypes were found significantly higher in post traumatic sepsis patients and had a significantly higher risk to developed sepsis complication (p < 0.05, OR = 0.86, C.I = 0.08-8.8).In case of TNF-α (-308) position, GA and GG genotype patients have a significantly lower risk of poor outcome (p < 0.05, OR = 0.25, C.I = 0.01-1.3) and (p < 0.05, OR = 0.22, C.I = 0.01-0.5) in comparison to AA genotype. In this study, two polymorphisms (IL-1β (-511) and IL-1R) were significantly associated with the development of MOF and mortality, where as IL-1α (-889) polymorphism associated with susceptibility for sepsis. The distribution of haplotypes of TGF-β and IL-6 were also associated with sepsis susceptibility and outcome.

CONCLUSION

In conclusion, we have found that the alternations in the genotype and allele frequency of IL-1β (-511C/T), TNF-α (-308 G/A), TNF-α (-238 G/A) and IL-10 (-1082 G/A) genes are associated with an higher risk of sepsis development in trauma patients and outcomes.

Genetic determinants of anti-malarial acquired immunity in a large multi-centre study

Background

Many studies report associations between human genetic factors and immunity to malaria but few have been reliably replicated. These studies are usually country-specific, use small sample sizes and are not directly comparable due to differences in methodologies. This study brings together samples and data collected from multiple sites across Africa and Asia to use standardized methods to look for consistent genetic effects on anti-malarial antibody levels.

Methods

Sera, DNA samples and clinical data were collected from 13,299 individuals from ten sites in Senegal, Mali, Burkina Faso, Sudan, Kenya, Tanzania, and Sri Lanka using standardized methods. DNA was extracted and typed for 202 Single Nucleotide Polymorphisms with known associations to malaria or antibody production, and antibody levels to four clinical grade malarial antigens [AMA1, MSP1, MSP2, and (NANP)₄] plus total IgE were measured by ELISA techniques. Regression models were used to investigate the associations of clinical and genetic factors with antibody levels.

Results

Malaria infection increased levels of antibodies to malaria antigens and, as expected, stable predictors of anti-malarial antibody levels included age, seasonality, location, and ethnicity. Correlations between antibodies to blood-stage antigens AMA1, MSP1 and MSP2 were higher between themselves than with antibodies to the (NANP)₄ epitope of the pre-erythrocytic circumsporozoite protein, while there was little or no correlation with total IgE levels. Individuals with sickle cell trait had significantly lower antibody levels to all blood-stage antigens, and recessive homozygotes for CD36 (rs321198) had significantly lower anti-malarial antibody levels to MSP2.

Conclusion

Although the most significant finding with a consistent effect across sites was for sickle cell trait, its effect is likely to be via reducing a microscopically positive parasitaemia rather than directly on antibody levels. However, this study does demonstrate a framework for the feasibility of combining data from sites with heterogeneous malaria transmission levels across Africa and Asia with which to explore genetic effects on anti-malarial immunity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-015-0833-x) contains supplementary material, which is available to authorized users.

Humoral immune responses against the malaria vaccine candidate antigen Plasmodium vivax AMA-1 and IL-4 gene polymorphisms in individuals living in an endemic area of the Brazilian Amazon

BACKGROUND

Several studies have recently demonstrated that the immune responses against malaria is governed by different factors, including the genetic components of the host. The IL-4 gene appears to be a strong candidate factor because of its role in the regulation of the Th2 response. The present study investigated the role of IL-4 polymorphisms in the development of IgG antibodies against PvAMA-1 and the IL-4 levels in individuals infected with Plasmodium vivax in a malaria endemic area in the Brazilian Amazon.

METHODS

The study sample included 83 patients who were diagnosed with P. vivax infection using thick smear and confirmed by nested-PCR. The IL-4 -590C>T and IL-4 -33C>T polymorphisms were genotyped by PCR-RFLP, and the intron 3 VNTR was genotyped by PCR. A standardised ELISA protocol was used to measure the total IgG against PvAMA-1. The cytokine/chemokine levels were measured using a Milliplex multiplex assay (Millipore). All of the subjects were genotyped with 48 ancestry informative markers to determine the proportions of African, European and Amerindian ancestry using STRUCTURE software.

RESULTS

Of the 83 patients, 60 (73%) produced IgG antibodies against PvAMA-1. A significant decrease in the percentage of respondents was observed among the primo-infected individuals. No significant differences were observed in the frequencies of genotypes and haplotypes among individuals who were positive or negative for IgG antibodies against PvAMA-1. Furthermore, no significant correlation was observed between the IL-4 polymorphisms, antibody levels, IL-4 levels, and parasitemia.

CONCLUSIONS

This study indicated that the polymorphisms identified in the IL-4 gene are not likely to play a role in the regulation of the antibody response against PvAMA-1 and IL-4 production in vivax malaria.

The genetic control of immunity to Plasmodium infection

Background

Malaria remains a major worldwide public health problem with ~207 million cases and ~627,000 deaths per year, mainly affecting children under five years of age in Africa. Recent efforts at elaborating a genetic architecture of malaria have focused on severe malaria, leading to the identification of two new genes and confirmation of previously known variants in HBB, ABO and G6PD, by exploring the whole human genome in genome-wide association (GWA) studies. Molecular pathways controlling phenotypes representing effectiveness of host immunity, notably parasitemia and IgG levels, are of particular interest given the current lack of an efficacious vaccine and the need for new treatment options.

Results

We propose a global causal framework of malaria phenotypes implicating progression from the initial infection with Plasmodium spp. to the development of the infection through liver and blood-stage multiplication cycles (parasitemia as a quantitative trait), to clinical malaria attack, and finally to severe malaria. Genetic polymorphism may control any of these stages, such that preceding stages act as mediators of subsequent stages. A biomarker of humoral immunity, IgG levels, can also be integrated into the framework, potentially mediating the impact of polymorphism by limiting parasitemia levels. Current knowledge of the genetic basis of parasitemia levels and IgG levels is reviewed through key examples including the hemoglobinopathies, showing that the protective effect of HBB variants on malaria clinical phenotypes may partially be mediated through parasitemia and cytophilic IgG levels. Another example is the IgG receptor FcγRIIa, encoded by FCGR2A, such that H131 homozygotes displayed higher IgG2 levels and were protective against high parasitemia and onset of malaria symptoms as shown in a causal diagram.

Conclusions

We thus underline the value of parasitemia and IgG levels as phenotypes in the understanding of the human genetic architecture of malaria, and the need for applying GWA approaches to these phenotypes.

Effect of transmission intensity and age on subclass antibody responses to Plasmodium falciparum pre-erythrocytic and blood-stage antigens

Cytophilic immunoglobulin (IgG) subclass responses (IgG1 and IgG3) to Plasmodium falciparum antigens have been associated with protection from malaria, yet the relative importance of transmission intensity and age in generation of subclass responses to pre-erythrocytic and blood-stage antigens have not been clearly defined. We analyzed IgG subclass responses to the pre-erythrocytic antigens CSP, LSA-1, and TRAP and the blood-stage antigens AMA-1, EBA-175, and MSP-1 in asymptomatic residents age 2 years or older in stable (n=116) and unstable (n=96) transmission areas in Western Kenya. In the area of stable malaria transmission, a high prevalence of cytophilic (IgG1 and IgG3) antibodies to each antigen was seen in all age groups. Prevalence and levels of cytophilic antibodies to pre-erythrocytic and blood-stage P. falciparum antigens increased with age in the unstable transmission area, yet IgG1 and IgG3 responses to most antigens for all ages in the unstable transmission area were less prevalent and lower in magnitude than even the youngest age group from the stable transmission area. The dominance of cytophilic responses over non-cytophilic (IgG2 and IgG4) was more pronounced in the stable transmission area, and the ratio of IgG3 over IgG1 generally increased with age. In the unstable transmission area, the ratio of cytophilic to non-cytophilic antibodies did not increase with age, and tended to be IgG3-biased for pre-erythrocytic antigens yet IgG1-biased for blood-stage antigens. The differences between areas could not be attributed to active parasitemia status, as there were minimal differences in antibody responses between those positive and negative for Plasmodium infection by microscopy in the stable transmission area. Individuals in areas of unstable transmission have low cytophilic to non-cytophilic IgG subclass ratios and low IgG3:IgG1 ratios to P. falciparum antigens. These imbalances could contribute to the persistent risk of clinical malaria in these areas and serve as population-level, age-specific biomarkers of transmission.

Genome-wide significant linkage to IgG subclass responses against Plasmodium falciparum antigens on chromosomes 8p22-p21, 9q34 and 20q13

A genome-wide scan was conducted for the levels of total immunoglobulin G (IgG) and IgG subclasses directed against Plasmodium falciparum antigens in an urban population living in Burkina Faso. Non-parametric multipoint linkage analysis provided three chromosomal regions with genome-wide significant evidence (logarithm of the odds (LOD) score >3.6), and five chromosomal regions with genome-wide suggestive evidence (LOD score >2.2). IgG3 levels were significantly linked to chromosomes 8p22-p21 and 20q13, whereas IgG4 levels were significantly linked to chromosome 9q34. In addition, we detected suggestive linkage of IgG1 levels to chromosomes 18p11-q12 and 18q12-q21, IgG4 levels to chromosomes 1p31 and 12q24 and IgG levels to chromosome 6p24-p21. Moreover, we genotyped genetic markers located within the regions of interest in a rural population living in Burkina Faso. We detected genome-wide significant and suggestive linkage results when combining the two study populations for chromosomes 1p31, 6p24-p21, 8p22-p21, 9q34, 12q24 and 20q13. Because high anti-parasite IgG3 and low anti-parasite IgG4 levels were associated with malaria resistance, the chromosomal regions linked to IgG3 and IgG4 levels are of special interest. Although the results should be confirmed in an independent population, they may provide new insights in understanding both the genetic control of IgG production and malaria resistance.

Genomics and infectious disease: a call to identify the ethical, legal and social implications for public health and clinical practice

Advances in genomics are contributing to the development of more effective, personalized approaches to the prevention and treatment of infectious diseases. Genetic sequencing technologies are furthering our understanding of how human and pathogen genomic factors - and their interactions - contribute to individual differences in immunologic responses to vaccines, infections and drug therapies. Such understanding will influence future policies and procedures for infectious disease management. With the potential for tailored interventions for particular individuals, populations or subpopulations, ethical, legal and social implications (ELSIs) may arise for public health and clinical practice. Potential considerations include balancing health-related benefits and harms between individuals and the larger community, minimizing threats to individual privacy and autonomy, and ensuring just distribution of scarce resources. In this Opinion, we consider the potential application of pathogen and host genomic information to particular viral infections that have large-scale public health consequences but differ in ELSI-relevant characteristics such as ease of transmission, chronicity, severity, preventability and treatability. We argue for the importance of anticipating these ELSI issues in advance of new scientific discoveries, and call for the development of strategies for identifying and exploring ethical questions that should be considered as clinical, public health and policy decisions are made.

Variations in ncRNA gene LOC284889 and MIF-794CATT repeats are associated with malaria susceptibility in Indian populations

BACKGROUND

There are increasing evidences on the role of non-coding RNA (ncRNA) as key regulator of cellular homeostasis. LOC284889 is an uncharacterized ncRNA gene on reverse strand to MIF mapped to 22q11.23. MIF, a lymphokine, regulates innate immune response by up-regulating the expression of TLR4, suppressing the p53 activity and has been shown to be involved in malaria pathogenesis.

METHODS

In this study, the possible effect of MIF variations on malaria susceptibility was investigated by re-sequencing the complete MIF gene along with 1 kb each of 5' and 3' region in 425 individuals from malaria endemic regions of the Orissa and Chhattisgarh states of India. The subjects comprised of 160 cases of severe malaria, 101 of mild malaria and 164 ethnically matched asymptomatic controls. Data were statistically compared between cases and controls for their possible association with Plasmodium falciparum malarial outcome.

RESULTS

It is the first study, which shows that the allele A (rs34383331T > A) in ncRNA is significantly associated with increased risk to P. falciparum malaria [severe: OR = 2.08, p = 0.002 and mild: OR = 2.09, P = 0.005]. In addition, it has been observed that the higher MIF-794CATT repeats (>5) increases malaria risk (OR = 1.61, p = 0.01). Further, diplotype (MIF-794CATT and rs34383331T > A) 5 T confers protection to severe malaria (OR = 0.55, p = 0.002) while 6A (OR = 3.07, p = 0.001) increases malaria risk.

CONCLUSIONS

These findings support the involvement of ncRNA in malarial pathogenesis and further emphasize the complex genetic regulation of malaria outcome. In addition, the study shows that the higher MIF-794CATT repeats (>5) is a risk factor for severe malaria. The study would help in identifying people who are at higher risk to malaria and adapt strategies for prevention and treatment.