Table 2.
Saliva-assisted transmission of human pathogens transmitted by Ixodes ricinus
| Pathogen | Saliva factora | Activity | Reference |
|---|---|---|---|
| TBE virus (Far Eastern subtype) | Dermacentor marginatus adult SGE day 5 | “Adjuvant” activity enhancing transmission to ticks | [43] |
| TBE virus (European subtype) | I. ricinus female SGE day 5 | Enhanced transmission from guinea pigs to ticks | [44] |
| TBE virus (European subtype) | Co-feeding infected and uninfected I. ricinus | Non-viremic transmission | [45–47] |
| TBE virus (European subtype) | I. ricinus female saliva day 6 | Enhanced replication in murine spleen dendritic cells ex vivo | [48] |
| Louping ill virus | Co-feeding infected and uninfected I. ricinus | Non-viremic transmission | [49] |
| Borrelia burgdorferi s.s. | Co-feeding infected and uninfected I. ricinus | Non-systemic transmission | [50] |
| Borrelia burgdorferi s.s.; B. lusitaniae | I. ricinus nymph SGE day 2–3 | Enhanced spirochete load in mice | [51] |
| Borrelia afzelii | I. ricinus female SGE day 5 | Enhanced infection of mice and feeding ticks | [52] |
| Borrelia burgdorferi s.s. | I. ricinus female saliva/SGE day 6 | Enhanced transmission from mice to ticks | [53] |
| Borrelia burgdorferi s.s. | Salp15 Iscap | Facilitates transmission from ticks to miceb | [54] |
| Borrelia burgdorferi s.s. | Salp15 Iric-1 | Facilitates needle infection of immune mice | [55] |
| Borrelia burgdorferi s.s.; Borrelia garnii | Salp15 Iscap and Iric-1 | In vitro protection against complement-mediated killing | [56] |
| Borrelia burgdorferi s.s. | Salp15 Iric-1 | In vitro suppression of borrelia-induced keratinocyte inflammation | [57] |
| Borrelia burgdorferi s.s. | TSLPIc | Facilitates transmission from ticks to mice and from mice to ticksd | [58] |
| Borrelia burgdorferi s.s.; B. garinii | TSLPI Iric | In vitro reduction of complement-mediated killing | [59] |
| Borrelia garnii | Salp20 | In vitro protection against complement-mediated killing | [60] |
| Borrelia burgdorferi s.s. | tHRFe | Promotes late stage feeding and thereby facilitates tick to host transmission | [61] |
| Borrelia burgdorferi s.s. | Sialostatin L2e | Increases level of skin infection following syringe inoculation | [62] |
| Borrelia burgdorferi s.s. | Salp25De | Facilitates transmission from mice to ticks | [63] |
| Borrelia burgdorferi s.s. | BIPf | In vitro inhibition of OspA and OspC-induced B cell proliferation | [64] |
| Anaplasma phagocytophilum | Sialostatin L2e | Promotes infection of mice by impairing inflammasome formation | [65] |
| Francisella tularensis | I. ricinus female SGE day 5 | Accelerated proliferation in mice | [66] |
tHRF tick histamine release factor
aSalivary gland extract (SGE) or saliva collected at specified day of feeding, or specific saliva protein; recombinant proteins Iscap from I. scapularis and Iric from I. ricinus. Most studies involving specific saliva proteins are with I. scapularis-derived recombinant proteins.
bDirect evidence of Salp15-assisted transmission of B. burgdorferi has only been reported for I. scapularis [54]
cTick salivary lectin pathway inhibitor
dDirect evidence of TSLPI-assisted transmission of B. burgdorferi has only be reported for I. scapularis [58]
eDerived from I. scapularis
fB cell inhibitory protein from I. ricinus