Catherine Suzanne Forconi

Background: Current licensed malaria vaccines are modestly protective against severe Plasmodium falciparum malaria but do not contain components which control blood-stage infection. We evaluated the impact of antibodies to 3 blood-stage candidate antigens (P. falciparum glutamic acid-rich protein [PfGARP], P. falciparum schizont egress antigen 1 [PfSEA-1], and P. falciparum glycophorin-binding protein 130 [PfGBP130]) on P. falciparum infection and disease in a longitudinal cohort of children living in a holoendemic region of Western Kenya. Methods: We enrolled and followed up 266 children aged 2–7 years living in Western Kenya. Over the course of a 3-year follow-up period, we actively assessed their health status weekly, collected blood samples monthly to assess P. falciparum infection incidence and intensity and measure immunoglobulin G antibody levels to blood-stage vaccine candidate antigens. Results: Children with high levels of immunoglobulin G antibodies to PfGBP130 or PfGARP, but not PfSEA-1, experienced 3.4- and 1.9-fold lower parasite densities, respectively, than those with low antibody levels (both P < .002). In addition, children with high levels of both anti-PfGBP130 and anti-PfGARP had significantly lower risk of clinical malaria than children with low antibody levels (hazard ratio, 0.58 [95% confidence interval, .85–.40]). Over the 3-year follow-up period, individuals with elevated anti-PfGBP130 and anti-PfGARP antibody levels experienced an average of 4.51 cases of clinical malaria while those with lower levels experienced an average of 7.11 cases (P = .005). Conclusions: Higher antibody levels to PfGBP130 and PfGARP predict significantly lower parasite densities and lower risks of clinical malaria among 2–7-year-old children residing in a holoendemic area of Kenya.

Burkitt lymphoma (BL) is an aggressive B-cell lymphoma that remains a leading cause of childhood cancer mortality in sub-Saharan Africa. Although the epidemiological link between Plasmodium falciparum (Pf) malaria and BL has been established, our understanding of the underlying immunological mechanisms conducive to tumorigenesis is incomplete. To address a noted gap in our knowledge of the immune landscape, we conducted a prospective study to profile neutrophil subsets from children with different exposure histories to Pf -malaria and children diagnosed with BL from Western Kenya, along with healthy malaria low-exposed Kenyan adults. Using multiparameter flow cytometry, we characterized neutrophils by expression of CD15, CD16, CD10, CD11b, CD182, CD184, and CD62L and found that malaria-exposed children exhibited increased frequencies of aged neutrophil subsets, accompanied by a reduction in the mature active subset frequencies compared to malaria low-exposed children. Notably, a positive correlation (rs = 0.7; p < 0.0001) was observed in immature neutrophils between malaria-exposed healthy and BL children, revealing a possible similar expansion of this subset in both groups. These findings suggest a malaria-associated expansion of the immature neutrophil subset. While functional assays were not performed in this study, previous reports indicate that immature neutrophils can exhibit tumor-promoting functions. Therefore, the observed shift in neutrophil profiles may reflect phenotypic changes associated with malaria exposure that could contribute to a permissive environment for BL.

/ Summary: Survival outcomes for pediatric Burkitt lymphoma (BL) substantially vary depending on geography (50-90%), which also serves as a proxy for the prevalence of Epstein-Barr virus (EBV) within the tumors. Although BL is considered an immunologically “cold” tumor with few tumor-infiltrating lymphocytes (TILs), their functional status has not been fully evaluated, especially for EBV-positive disease. Here, we characterize the exhaustion and activation profiles of T cells in the tumor microenvironment (TME) of EBV-positive BL using orthogonal methods, single-cell gene expression analysis, spectral flow cytometry, and immuno-histochemistry staining (IHC). We found that CD8+ TILs displayed a mosaic of immune inhibitory gene expression encoding, PD1 , TIGIT , LAG3 and HAVCR2/ TIM3. IHC validated the expression of PD1 and TIGIT on CD8+ TILs, as well as their respective ligands, PDL-1, PVR, and Nectin-2 on malignant B cells. Despite exhaustion-associated signatures, CD8+ TILs retain cytotoxic potential, expressing granules (i.e. Granzyme A, Perforin) and cytokines (i.e. IFNγ) and demonstrate an increased uptake of metabolites such as glucose, arginine, and methionine. In peripheral blood, pediatric BL patients exhibited a significantly higher abundance of PD1+TIGIT+ CD8+ T cells compared to healthy children. Notably, these circulating T cells from BL patients express significantly lower levels of TOX, suggesting they are not irreversibly dysfunctional. Together, our results indicate that CD8+ T cells both in the TME and in circulation of children with BL are not terminally exhausted but remain poised for functional re-invigoration. These findings support the potential integration of immune checkpoint inhibitors into combination chemotherapeutic regimens to improve outcomes for these children. Significance: EBV-positive BL tumors contain functional, metabolically active CD8+ T cells. Circulating PD1+TIGIT+CD8+ T cells found in BL patients’ blood are a biomarker for those in the tumor microenvironment.

Suite à une transplantation, les patients présentent un affaiblissement de leur système immunitaire laissant ainsi place libre aux infections opportunistes et principalement au CMV. L’implication de ce virus dans l’accélération de la mise en place du rejet chronique du greffon reste controversée et largement incomprise. Nos objectifs ont été d’une part de déterminer l’impact de l’infection à CMV du donneur sur la survie du greffon rénal et d’autre part d’identifier certains facteurs liés à la réponse immunitaire de l’hôte pouvant moduler ce risque. Selon nos résultats, l’infection à CMV du donneur est un facteur de risque indépendant de la perte des greffons rénaux, d’autant plus si le receveur est aussi infecté. Le SNP PD-1.3 est un facteur de risque génétique fort de la perte du greffon rénal associé au CMV du donneur et ce résultat est confirmé grâce à une cohorte de validation de patients transplantés pulmonaires. Ce travail suggère un lien fort entre ce SNP et l’épuisement de la réponse immunitaire anti-CMV et met en avant l’importance de la physiopathologie liée au CMV sur l’association clinique observée.

Africa has reported lower COVID-19 morbidity and mortality compared to other regions. Yet, the flat COVID-19 trajectory remains to be fully explained. Nigeria, Africa’s most populous country, accounted for less than 1% of global COVID-19 cases. The present study evaluated SARS-CoV-2 seroprevalence, vaccine uptake, and methodological differences in serological threshold setting among febrile patients attending peri-urban and urban clinics in Southern Nigeria. Between October 2022 and February 2023, 745 febrile participants were recruited from Owo (Ondo State) and Ikorodu (Lagos State). Serum samples were tested for IgG antibodies against wild-type and variant SARS-CoV-2 antigens using a multiplex bead-based antibody assay. Seropositivity was calculated using two classification boundary methods: (i) the conventional three standard deviations above the mean of negative controls (3STDV) and (ii) the open-source SeroNIST tool. Vaccine uptake and risk factors for exposure were assessed. Vaccine uptake was 66.0% and significantly higher in peri-urban Owo (80.2%) than urban Ikorodu (52.6%, p-value < 0.0001). Increasing age was positively associated with vaccination (p-value < 0.0001). Sex, education, and religion did not influence vaccine uptake. Vaccinated individuals had significantly lower odds of being positive for anti-N SARS-CoV-2 antibodies (p-value = 0.001), indicating a potential protective effect of the vaccine. Age, education, and religion did not influence anti-N SARS-CoV-2 seropositivity. Overall, our study revealed high S/RBD-based seroprevalences for all variants except Omicron among the unvaccinated participants (range: 89.1% - 100%). SARS-CoV-2 exposure in Southern Nigeria was likely widespread and underrecognized, with high seroprevalence among symptomatic peri-urban and urban populations. Peri-urban communities demonstrated higher vaccine uptake than urban counterparts, and age-targeted campaigns likely drove uptake among older individuals. Further, our study detected a potential protective effect of the vaccine among the study population. Finally, standardized thresholding methods such as SeroNIST are critical for accurate seroprevalence estimates.

Terminally differentiated CD56negCD16pos NK cells have been described after chronic viral and malaria infections, and in children diagnosed with Burkitt lymphoma (BL). Despite CD56neg NK cells appearing to be poor at direct cytotoxicity, they express high levels of cytotoxic granules (i.e. granzymes, perforin), activation markers, and Fc-γ receptors (CD32 and CD16) that are typically engaged in antibody-dependent cell cytotoxicity (ADCC). In addition, the abundance of CD56neg NK cells strongly correlates with IgG1 and IgG3 plasma levels, which are essential subclasses for ADCC. To determine whether CD56neg NK cells have superior ADCC capacity relative to CD56dim NK cells, we performed ADCC assays using effector cells from pediatric cancer patients and healthy children from malaria endemic regions of Kenya, targeting in vitro rituximab-treated commercial and newly established BL cell lines. We found that CD56neg NK cells were indeed capable of in vitro ADCC, showing a significant increase of CD107a-mediated degranulation in the presence of rituximab; however, they were not as efficient as CD56dim NK cells. Moreover, we found that the ADCC magnitude was significantly lower against EBV-Type 2 (EBV-T2) BL lines compared to EBV-Type 1 (EBV-T1). EBV-T2 tumor cell lines expressed significantly more lytic viral proteins than EBV-T1, making them more sensitive to direct cytotoxicity. Results from this study highlight the importance of assessing inter-patient variation in NK cell profiles in conjunction with ADCC sensitivity and EBV type within tumor cells when evaluating clinical outcomes for NK-mediated immunotherapies.

Burkitt lymphoma (BL) is an aggressive B-cell lymphoma that remains a leading cause of childhood cancer mortality in sub-Saharan Africa. Although the epidemiological link between Plasmodium falciparum (Pf) malaria and BL has been established, our understanding of the underlying immunological mechanisms conducive to tumorigenesis is incomplete. To address a noted gap in our knowledge of the immune landscape, we profiled neutrophil subsets from children with different exposure histories to Pf -malaria and children diagnosed with BL from Western Kenya, along with healthy malaria-naive Kenyan adults. Using multiparameter flow cytometry, we characterized neutrophils by expression of CD15, CD16, CD10, CD11b, CD182, CD184, and CD62L and found that malaria-exposed children exhibited increased frequencies of aged neutrophil subsets, accompanied by a reduction in the mature subset frequencies compared to malaria-naive children. Malaria-exposed children also had neutrophil profiles that closely resembled those seen in the adults. Notably, a positive correlation (rs = 0 . 7; p < 0 . 0001) was observed in immature neutrophils between malaria-exposed healthy and BL children, indicating a similar expansion pattern of this subset in both groups. This finding suggests a malaria-driven expansion of the immature subset, potentially promoting a permissive environment for BL. Our data suggests that the observed shift in neutrophil profiles could contribute to the malaria-induced immunopathology associated with BL Visual Created in BioRender. Forconi, C. (2025) https://BioRender.com/oz60qvq

Circulating T-follicular helper (cT_FH) cells have the potential to provide an additional correlate of protection against Plasmodium falciparum (Pf) as they are essential to promote B-cell production of long-lasting antibodies. Assessing the specificity of cT_FH subsets to individual malaria antigens is vital to understanding the variation observed in antibody responses and identifying promising malaria vaccine candidates. Using spectral flow cytometry and unbiased clustering analysis, we assessed antigen-specific cT_FH cell recall responses in vitro to malaria vaccine candidates Pf-schizont egress antigen-1 (PfSEA-1A) and Pf-glutamic acid-rich protein (PfGARP) within a cross-section of children and adults living in a malaria-holoendemic region of western Kenya. In children, a broad array of cT_FH subsets (defined by cytokine and transcription factor expression) were reactive to both malaria antigens, PfSEA-1A and PfGARP, while adults had a narrow profile centering on cT_FH17- and cT_FH1/17-like subsets following stimulation with PfGARP only. Because T_FH17 cells are involved in the maintenance of memory antibody responses within the context of parasitic infections, our results suggest that PfGARP might generate longer-lived antibody responses compared to PfSEA-1A. These findings have intriguing implications for evaluating malaria vaccine candidates as they highlight the importance of including cT_FH profiles when assessing interdependent correlates of protective immunity.

Background Circulating T-follicular helper (cTFH) cells have the potential to provide an additional correlate of protection against Plasmodium falciparum (Pf) as they are essential to promote B-cell production of long-lasting antibodies. Assessing the specificity of cTFH subsets to individual malaria antigens is vital to understanding the variation observed in antibody responses and identifying promising malaria vaccine candidates. Methods Using spectral flow cytometry and unbiased clustering analysis, we assessed antigen-specific cTFH cell recall responses in vitro to malaria vaccine candidates Pf-schizont egress antigen-1 (PfSEA-1A) and Pf-glutamic acid-rich protein (PfGARP) within a cross-section of children and adults living in a malaria-holoendemic region of western Kenya. Findings In children, a broad array of cTFH subsets (defined by cytokine and transcription factor expression) were reactive to both malaria antigens, PfSEA-1A and PfGARP, while adults had a narrow profile centering on cTFH17- and cTFH1/17-like subsets following stimulation with PfGARP only. Interpretation Because TFH17 cells are involved in the maintenance of memory antibody responses within the context of parasitic infections, our results suggest that PfGARP might generate longer-lived antibody responses compared to PfSEA-1A. These findings have intriguing implications for evaluating malaria vaccine candidates as they highlight the importance of including cTFH profiles when assessing interdependent correlates of protective immunity.