Relative transcription of autophagy-related genes in Amblyomma sculptum and Rhipicephalus microplus ticks

Ticks endure stressful off-host periods and perform as vectors of a diversity of infectious agents, thus engaging pathways that expectedly demand for autophagy. Little is known of ticks' autophagy, a conserved eukaryotic machinery assisting in homeostasis processes that also participates in tissue-dependent metabolic functions. Here, the autophagy-related ATG4 (autophagin-1), ATG6 (beclin-1) and ATG8 (LC3) mRNAs from the human diseases vector Amblyomma sculptum and the cattle-tick Rhipicephalus microplus were identified. Comparative qPCR quantifications evidenced different transcriptional status for the ATG genes in the salivary glands (SG), ovaries and intestines of actively feeding ticks. These ATGs had increased relative transcription under nutrient-deprivation, as determined by validation tests with R. microplus embryo-derivative cells BME26 and A. sculptum SG explants incubations in HBSS. Starvation lead to 4-31.8× and ~ 60-500× increments on the ATGs mRNA loads in BME26 and A. sculptum SG explants, respectively. PI3K inhibitor 3MA treatment also affected ATGs expression in BME26. Some ATGs were more transcribed in the SGs than in the ovaries of cattle-ticks. Amblyomma sculptum/R. microplus interspecific comparisons showed that ATG4 and ATG6 were 0.18× less expressed in A. sculptum SGs, but ~ 10-100× more expressed in their ovaries when compared to R. microplus organs. ATG4 and ATG8a transcript loads were ~ 120× and ~ 40× higher, respectively, in A. sculptum intestines when compared to cattle-ticks of similar weight category. ATGs expression in A. sculptum intestines increased with tick weight, indicating Atgs contribution to intracellular blood digestion. Possible roles of the autophagy machinery and their organ-specific expression profile on vector biology are discussed.

Resting Cysts of the Pigmented Ciliate Blepharisma sinuosum Sawaya, 1940 (Ciliophora: Heterotrichea)

The morphology of Blepharisma sinuosum resting cysts and the dynamics of pigmentation at different stages of encystment are presented for the first time. Cyst morphometrics are similar to other Blepharisma species, with three-wall layers, bacteria surrounding the ectocyst, a conical plug, and wrinkly surface toward the plug in mature stages. The vegetative moniliform macronucleus changes to a horseshoe shape, and at early stages, the cystic cytoplasm is homogeneously pigmented, comprising a contractile vacuole; later, pigments polarize toward the plug, decorate the cortical layer, and become brownish. This work reinforces the potential role of pigment dynamics on cyst biology.

Comparative growth of spotted fever group Rickettsia spp. strains in Vero cells

In Brazil, the spotted fever group (SFG) Rickettsia rickettsii and Rickettsia parkeri related species are the etiological agents of spotted fever rickettsiosis. However, the SFG, Rickettsia rhipicephali, that infects humans, has never been reported. The study of growth dynamics can be useful for understanding the infective and invasive capacity of these pathogens. Here, the growth rates of the Brazilian isolates R. rickettsii str. Taiaçu, R. parkeri str. At#24, and R. rhipicephali HJ#5, were evaluated in Vero cells by quantitative polymerase chain reaction. R. rhipicephali showed different kinetic growth compared to R. rickettsii and R. parkeri.

Rickettsia amblyommii infecting Amblyomma sculptum in endemic spotted fever area from southeastern Brazil

The Rickettsia bacteria include the aetiological agents for the human spotted fever (SF) disease. In the present study, a SF groupRickettsia amblyommii related bacterium was detected in a field collected Amblyomma sculptum (Amblyomma cajennense species complex) tick from a Brazilian SF endemic site in southeastern Brazil, in the municipality of Juiz de Fora, state of Minas Gerais. Genetic analysis based on genes ompA,ompB and htrA showed that the detected strain, named R. amblyommii str. JF, is related to the speciesR. amblyommii.

Bacteria associated with Amblyomma cajennense tick eggs

Ticks represent a large group of pathogen vectors that blood feed on a diversity of hosts. In the Americas, the Ixodidae ticks Amblyomma cajennense are responsible for severe impact on livestock and public health. In the present work, we present the isolation and molecular identification of a group of culturable bacteria associated with A. cajennense eggs from females sampled in distinct geographical sites in southeastern Brazil. Additional comparative analysis of the culturable bacteria from Anocentor nitens, Rhipicephalus sanguineus and Ixodes scapularis tick eggs were also performed. 16S rRNA gene sequence analyses identified 17 different bacterial types identified as Serratia marcescens, Stenotrophomonas maltophilia, Pseudomonas fluorescens, Enterobacter spp., Micrococcus luteus, Ochrobactrum anthropi, Bacillus cereus and Staphylococcus spp., distributed in 12 phylogroups. Staphylococcus spp., especially S. sciuri, was the most prevalent bacteria associated with A. cajennense eggs, occurring in 65% of the samples and also frequently observed infecting A. nitens eggs. S. maltophilia, S. marcescens and B. cereus occurred infecting eggs derived from specific sampling sites, but in all cases rising almost as pure cultures from infected A. cajennense eggs. The potential role of these bacterial associations is discussed and they possibly represent new targets for biological control strategies of ticks and tick borne diseases.

Kinetics of Borrelia burgdorferi infection in larvae of refractory and competent tick vectors

The acquisition of Borrelia burgdorferi by the larvae of competent and refractory ixodid ticks was assessed by quantitative polymerase chain reaction (PCR). Larvae were fed on infected mice, and the spirochete loads were determined during feeding and up to 93 d postfeeding. Amblyomma americanum (L.) was refractory to B. burgdorferi infection, with almost no detection of spirochete DNA during or postfeeding. In contrast, Ixodes scapularis Say supported high loads of spirochetes (10(3)-10(4) per larva). In Dermacentor variabilis (Say), B. burgdorferi uptake was reduced, with an average of 16 spirochetes per larvae acquired after 4 d of feeding, representing 1/195 of the counts in I. scapularis. However, during the first day postfeeding, the spirochete growth rate in D. variabilis reached 0.076 generations per hour, 7.7 times greater than the highest growth rate detected in I. scapularis. D. variabilis supported intense spirochete growth up to the fourth day postinfection, when the counts increased to an average of 282 spirochetes per larvae or 1/8.5 of the I. scapularis counts 4 d postfeeding. The kinetics of spirochete growth was unstable in D. variabilis compared with I. scapularis, and transmission of B. burgdorferi by D. variabilis could not be demonstrated. A cofeeding experiment indicated that I. scapularis feeding increased A. americanum spirochete uptake. These collective results indicate suboptimal conditions for B. burgdorferi uptake and colonization within A. americanum or the presence of anti-Borrelia factor(s) in this nonpermissive tick species.

Capillary feeding of specific dsRNA induces silencing of the isac gene in nymphal Ixodes scapularis ticks

Ixodes scapularis transmits several pathogens including Borrelia burgdorferi. Bioactive compounds in tick saliva support tick feeding and influence pathogen transmission to the mammalian host. These studies utilized oral delivery of dsRNA to silence an anticomplement gene (isac) in I. scapularis nymphs. Silencing of isac significantly reduced fed-tick weight compared to delivery of control lacZ dsRNA, and immunoblots specific for FlaB protein indicated a reduction in spirochete load in isac-silenced infected nymphs. SDS-PAGE demonstrated that isac gene silencing affected expression of a number of salivary and non-salivary gland proteins in ticks. Finally, multiple isac cDNA homologues were cloned, and these may represent a new gene family coexpressed during tick feeding. This work presents a novel oral delivery approach for specific gene silencing in I. scapularis nymphs and characterizes the effect of isac on blood-feeding in an attempt to block transmission of B. burgdorferi.

Differential infectivity of the Lyme disease spirochete Borrelia burgdorferi derived from Ixodes scapularis salivary glands and midgut

Blood fed nymphal Ixodes scapularis Say infected with Borrelia burgdorferi were dissected to obtain salivary gland and midgut extracts. Extracts were inoculated into C3H/HeJ mice, and ear, heart, and bladder were cultured to determine comparative infectivity. Aliquots of extracts were then analyzed by quantitative polymerase chain reaction to determine the number of spirochetes inoculated into mice. A comparative median infectious dose (ID50) was determined for both salivary gland and midgut extract inoculations. Our data demonstrated a statistically significant difference (P < 0.002) in the ID50 derived from salivary gland (average = 18) versus midgut (average = 251) extracts needed to infect susceptible mice. A rationale for the differential infectivity of salivary and midgut derived spirochetes is discussed.