Comparative analysis of peripheral whole blood transcriptome from asymptomatic carriers reveals upregulation of subsets of surface proteins implicated in Plasmodium falciparum phenotypic plasticity.

The molecular mechanism underlying Plasmodium falciparum's persistence in the asymptomatic phase of infection remains largely unknown. However, large-scale shifts in the parasites' gene expression during asymptomatic infections may enhance phenotypic plasticity, maximizing their fitness and leading to the persistence of the asymptomatic infections. To uncover these mechanisms, we aimed to identify parasite genetic factors implicated in asymptomatic infections through whole transcriptome analysis. We analyzed publicly available transcriptome datasets containing asymptomatic malaria (ASM), uncomplicated malaria (SM), and malaria-naïve (NSM) samples from 35 subjects for differentially expressed genes (DEGs) and long noncoding RNAs. Our analysis identified 755 and 1773 DEGs in ASM vs SM and NSM, respectively. These DEGs revealed sets of genes coding for proteins of unknown functions (PUFs) upregulated in ASM vs SM and ASM, suggesting their role in underlying fundamental molecular mechanisms during asymptomatic infections. Upregulated genes in ASM vs SM revealed a subset of 24 clonal variant genes (CVGs) involved in host-parasite and symbiotic interactions and modulation of the symbiont of host erythrocyte aggregation pathways. Moreover, we identified 237 differentially expressed noncoding RNAs in ASM vs SM, of which 11 were found to interact with CVGs, suggesting their possible role in regulating the expression of CVGs. Our results suggest that P. falciparum utilizes phenotypic plasticity as an adaptive mechanism during asymptomatic infections by upregulating clonal variant genes, with long noncoding RNAs possibly playing a crucial role in their regulation. Thus, our study provides insights into the parasites' genetic factors that confer a fitness advantage during asymptomatic infections.

Implications of asymptomatic malaria infections on hematologic parameters in adults living with HIV in malaria-endemic regions with varying transmission intensities.

OBJECTIVES: HIV and malaria coinfection impacts disease management and clinical outcomes. This study investigated hematologic abnormalities in malaria-asymptomatic people living with HIV (PLHIV) in regions with differing malaria transmission. METHODS: Study participants were enrolled in the African Cohort Study: two sites in Kenya, one in Uganda, and one in Nigeria. Data was collected at enrollment and every 6 months. Logistic regression estimated odds ratios for associations between HIV/malaria status and anemia, thrombocytopenia, and leucopenia. RESULTS: Samples from 1587 participants with one or more visits comprising 1471 (92.7%) from PLHIV and 116 (7.3%) without HIV were analyzed. Parasite point prevalence significantly differed across the study sites (P <0.001). PLHIV had higher odds of anemia, with males at lower odds compared to females; the odds of anemia decreased with age, reaching significance in those ≥50 years old. Participants in Kisumu, Kenya had higher odds of anemia compared to other sites. PLHIV had higher odds of leucopenia, but malaria co-infection was not associated with worsened leucopenia. The odds of thrombocytopenia were decreased in HIV/malaria co-infection compared to the uninfected group. CONCLUSION: Hematological parameters are important indicators of health and disease. In PLHIV with asymptomatic malaria co-infection enrolled across four geographic sites in three African countries, abnormalities in hematologic parameters differ in different malaria transmission settings and are region-specific.

Epidemiological and clinical implications of asymptomatic malaria and schistosomiasis co-infections in a rural community in western Kenya.

BACKGROUND: Malaria and schistosomiasis present considerable disease burden in tropical and sub-tropical areas and severity is worsened by co-infections in areas where both diseases are endemic. Although pathogenesis of these infections separately is well studied, there is limited information on the pathogenic disease mechanisms and clinical disease outcomes in co-infections. In this study, we investigated the prevalence of malaria and schistosomiasis co-infections, and the hematologic and blood chemistry abnormalities in asymptomatic adults in a rural fishing community in western Kenya. METHODS: This sub-study used samples and data collected at enrollment from a prospective observational cohort study (RV393) conducted in Kisumu County, Kenya. The presence of malaria parasites was determined using microscopy and real-time-PCR, and schistosomiasis infection by urine antigen analysis (CCA). Hematological analysis and blood chemistries were performed using standard methods. Statistical analyses were performed to compare demographic and infection data distribution, and hematologic and blood chemistry parameters based on different groups of infection categories. Clinically relevant hematologic conditions were analyzed using general linear and multivariable Poisson regression models. RESULTS: From February 2017 to May 2018, we enrolled 671 participants. The prevalence of asymptomatic Plasmodium falciparum was 28.2% (157/556) and schistosomiasis 41.2% (229/562), with 18.0% (100/556) of participants co-infected. When we analyzed hematological parameters using Wilcoxon rank sum test to evaluate median (IQR) distribution based on malarial parasites and/or schistosomiasis infection status, there were significant differences in platelet counts (p = 0.0002), percent neutrophils, monocytes, eosinophils, and basophils (p < 0.0001 each). Amongst clinically relevant hematological abnormalities, eosinophilia was the most prevalent at 20.6% (116/562), whereas thrombocytopenia was the least prevalent at 4.3% (24/562). In univariate model, Chi-Square test performed for independence between participant distribution in different malaria parasitemia/schistosomiasis infection categories within each clinical hematological condition revealed significant differences for thrombocytopenia and eosinophilia (p = 0.006 and p < 0.0001, respectively), which was confirmed in multivariable models. Analysis of the pairwise mean differences of liver enzyme (ALT) and kidney function (Creatinine Clearance) indicated the presence of significant differences in ALT across the infection groups (parasite + /CCA + vs all other groups p < .003), but no differences in mean Creatinine Clearance across the infection groups. CONCLUSIONS: Our study demonstrates the high burden of asymptomatic malaria parasitemia and schistosomiasis infection in this rural population in Western Kenya. Asymptomatic infection with malaria or schistosomiasis was associated with laboratory abnormalities including neutropenia, leukopenia and thrombocytopenia. These abnormalities could be erroneously attributed to other diseases processes during evaluation of diseases processes. Therefore, evaluating for co-infections is key when assessing individuals with laboratory abnormalities. Additionally, asymptomatic infection needs to be considered in control and elimination programs given high prevalence documented here.