Differential expression of var subgroups and PfSir2a genes in afebrile Plasmodium falciparum malaria: a matched case–control study

• Published in: Malaria Journal
• Main Authors: Himanshu Gupta, Beatriz Galatas, Gloria Matambisso, Lidia Nhamussua, Pau Cisteró, Quique Bassat, Aina Casellas, Eusébio Macete, John J. Aponte, Charfudin Sacoor, Pedro Alonso, Francisco Saúte, Caterina Guinovart, Pedro Aide, Alfredo Mayor
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2019
• Subjects: Afebrile malaria; var genes; Gametocytes; PfSir2a; Mozambique; Arctic medicine. Tropical medicine; RC955-962; Infectious and parasitic diseases; RC109-216; Arctic
• Online Access: https://doi.org/10.1186/s12936-019-2963-z; https://doaj.org/article/68e0b7b03c3042acb1ab67459a334dc6

Abstract Background Poor knowledge on the afebrile Plasmodium falciparum biology limits elimination approaches to target asymptomatic malaria. Therefore, the association of parasite factors involved in cytoadhesion, parasite multiplication and gametocyte maturation with afebrile malaria was assessed. Methods Plasmodium falciparum isolates were collected from febrile (axillary temperature ≥ 37.5 °C or a reported fever in the previous 24 h) and afebrile (fever neither at the visit nor in the previous 24 h) individuals residing in Southern Mozambique. var, PfSir2a and Pfs25 transcript levels were determined by reverse transcriptase quantitative PCRs (RT-qPCRs) and compared among 61 pairs of isolates matched by parasite density, age and year of sample collection. Results The level of varC and PfSir2a transcripts was higher in P. falciparum isolates from afebrile individuals (P ≤ 0.006), while varB and DC8 genes (P ≤ 0.002) were higher in isolates from individuals with febrile infections. After adjusting the analysis by area of residence, doubling the relative transcript unit (RTU) of varC and PfSir2a was associated with a 29.7 (95% CI 4.6–192.3) and 8.5 (95% CI 1.9–32.2) fold increases, respectively, of the odds of being afebrile. In contrast, doubling the RTU of varB and DC8 was associated with a 0.8 (95% CI 0.05–0.6) and 0.2 (95% CI 0.04–0.6) fold changes, respectively, of the odds of being afebrile. No significant differences were found for Pfs25 transcript levels in P. falciparum isolates from afebrile and febrile individuals. Conclusions var and gametocyte-specific transcript patterns in febrile and afebrile infections from southern Mozambique matched by age, parasite density and recruitment period suggest similar transmissibility but differential expression of variant antigens involved in cytoadhesion and immune-evasion.