Leishmania HASP and SHERP Genes Are Required for In Vivo Differentiation, Parasite Transmission and Virulence Attenuation in the Host

Abstract

Differentiation of extracellular Leishmania promastigotes within their sand fly vector, termed metacyclogenesis, is considered to be essential for parasites to regain mammalian host infectivity. Metacyclogenesis is accompanied by changes in the local parasite environment, including secretion of complex glycoconjugates within the promastigote secretory gel and colonization and degradation of the sand fly stomodeal valve. Deletion of the stage-regulated HASP and SHERP genes on chromosome 23 of Leishmania major is known to stall metacyclogenesis in the sand fly but not in in vitro culture. Here, parasite mutants deficient in specific genes within the HASP/SHERP chromosomal region have been used to investigate their role in metacyclogenesis, parasite transmission and establishment of infection. Metacyclogenesis was stalled in HASP/SHERP mutants in vivo and, although still capable of osmotaxis, these mutants failed to secrete promastigote secretory gel, correlating with a lack of parasite accumulation in the thoracic midgut and failure to colonise the stomodeal valve. These defects prevented parasite transmission to a new mammalian host. Sand fly midgut homogenates modulated parasite behaviour in vitro, suggesting a role for molecular interactions between parasite and vector in Leishmania development within the sand fly. For the first time, stage-regulated expression of the small HASPA proteins in Leishmania (Leishmania) has been demonstrated: HASPA2 is expressed only in extracellular promastigotes and HASPA1 only in intracellular amastigotes. Despite its lack of expression in amastigotes, replacement of HASPA2 into the null locus background delays onset of pathology in BALB/c mice. This HASPA2-dependent effect is reversed by HASPA1 gene addition, suggesting that the HASPAs may have a role in host immunomodulation.

Distinct gene expression patterns in vector-residing Leishmania infantum identify parasite stage-enriched markers

“…Similarly, we have identified mRNA up-regulation of galactosyl-and mannosyltransferases in the leptomonad and metacyclic stages, consistent with elongation of LPG in the metacyclic stage [25]. A similar phenomenon was observed for genes linked to Leishmania differentiation into infective metacyclics, such as SHERP and HASPa [17]. In accordance with the stationary-phase specific expression of such proteins, the correspondent transcripts are up-regulated in the leptomonad and metacyclic stages.…”

“…For instance, the number of enriched histone genes, and their expression levels, gradually decreased from the procyclic to the metacyclic stage ( Fig 3A; Supplemental Table S5). Genes encoding the small hydrophilic endoplasmic reticulumassociated protein (SHERP) and hydrophilic acylated surface protein a (HASPa), associated to metacylogenesis [17], were up-regulated in leptomonads compared to nectomonads ( Fig 3B; Supplemental Table S5), and overall exhibited the highest expression in metacylics ( Fig 3B). On the other hand, the gene encoding the META1 protein, also associated to metacylogenesis [17], was up-regulated as early as the nectomonad stage compared to procyclic ( Fig 3B; Supplemental Table S5).…”

“…Genes encoding the small hydrophilic endoplasmic reticulumassociated protein (SHERP) and hydrophilic acylated surface protein a (HASPa), associated to metacylogenesis [17], were up-regulated in leptomonads compared to nectomonads ( Fig 3B; Supplemental Table S5), and overall exhibited the highest expression in metacylics ( Fig 3B). On the other hand, the gene encoding the META1 protein, also associated to metacylogenesis [17], was up-regulated as early as the nectomonad stage compared to procyclic ( Fig 3B; Supplemental Table S5). Regarding the genes involved in the elongation of the glycoconjugate LPG, transcripts for a mannosyltrasferase and the galactosyltransferases (SCG4, SCG7, SCGR3, and SCGR5) were up-regulated in leptomonads and metacyclics, respectively (Fig 3C; Supplemental Table S5).…”

A putative ATP/GTP binding protein affects Leishmania mexicana growth in insect vectors and vertebrate hosts

“…All differentiation events are characterized by dramatic changes in parasite morphology, composition of cell surface glycolipids, gene expression, and other cellular features [8–10]. Gene products involved in either differentiation or infection maintenance in both hosts are potential virulence factors, i.e.…”

Essential roles for deubiquitination inLeishmanialife cycle progression

“…Overall, the phenotypes observed in the pooled context of the Bar-seq experiment reflect well the individual phenotyping of the viability assay. To further validate how these null mutants behave during amastigote differentiation, a western blot against HASPB, a marker for amastigotes [24], was performed. Δ dub4 , Δ dub7 , Δ dub9 and Δ dub13 showed very low or no expression of HASPB 120 h after the initiation of differentiation (Fig.…”