Serum Removal from Culture Induces Growth Arrest, Ploidy Alteration, Decrease in Infectivity and Differential Expression of Crucial Genes in Leishmania infantum Promastigotes

Leishmania infantum is one of the species responsible for visceral leishmaniasis. This species is distributed basically in the Mediterranean basin. A recent outbreak in humans has been reported in Spain. Axenic cultures are performed for most procedures with Leishmania spp. promastigotes. This model is stable and reproducible and mimics the conditions of the gut of the sand fly host, which is the natural environment of promastigote development. Culture media are undefined because they contain mammalian serum, which is a rich source of complex lipids and proteins. Serum deprivation slows down the growth kinetics and therefore, yield in biomass. In fact, we have confirmed that the growth rate decreases, as well as infectivity. Ploidy is also affected. Regarding the transcriptome, a high-throughput approach has revealed a low differential expression rate but important differentially regulated genes. The most remarkable profiles are: up-regulation of the GINS Psf3, the fatty acyl-CoA synthase (FAS1), the glyoxylase I (GLO1), the hydrophilic surface protein B (HASPB), the methylmalonyl-CoA epimerase (MMCE) and an amastin gene; and down-regulation of the gPEPCK and the arginase. Implications for metabolic adaptations, differentiation and infectivity are discussed herein.

利什曼原虫属中的婴儿利什曼原虫是导致内脏利什曼病的病原体之一。该物种主要分布在地中海盆地地区。近期在西班牙发生了人类感染病例的爆发。在大多数涉及利什曼原虫属无性生殖体（promastigotes）的实验过程中，均采用无菌培养。该模型稳定且可重复，能够模拟沙蝇宿主肠道环境，后者是无性生殖体发育的自然场所。培养基成分未明，因其含有哺乳动物血清，而血清是复杂脂质和蛋白质的丰富来源。血清剥夺会减缓生长动力学，从而降低生物量产量。事实上，我们已经证实，生长速率和感染性均有所下降，此外，倍性也受到影响。关于转录组，高通量测序方法揭示了低差异表达率，但存在重要的差异调控基因。最显著的基因表达模式包括：GINS Psf3、脂肪酸酰基辅酶A合成酶（FAS1）、甘露醇酸酶I（GLO1）、亲水性表面蛋白B（HASPB）、甲基马内酰辅酶A异构酶（MMCE）和一种amastin基因的上调表达；以及gPEPCK和精氨酸酶的下调表达。本文讨论了这些发现对代谢适应、分化和感染性的影响。