Background: Mycoplasma genitalium is an emerging sexually transmitted pathogen that has been associated with significant reproductive tract inflammatory syndromes in women. In addition, the strong association between severity of M. genitalium infection and Human Immunodeficiency Virus type 1 (HIV-1) shedding from the cervix suggests that innate responses to M. genitalium may influence pathogenesis of other sexually transmitted infections. Epithelial cells (ECs) of the reproductive mucosa are the first cells contacted by sexually transmitted pathogens. Therefore, we first characterized the dynamics of intracellular and extracellular localization and resultant innate immune responses from human vaginal, ecto- and endocervical ECs to M. genitalium type strain G37 and a low-pass contemporary isolate, M2300. Results: Both M. genitalium strains rapidly attached to vaginal and cervical ECs by 2 h post-infection (PI). By 3 h PI, M. genitalium organisms also were found in intracellular membrane-bound vacuoles of which approximately 60% were adjacent to the nucleus. Egress of M. genitalium from infected ECs into the culture supernatant was observed but, after invasion, viable intracellular titers were significantly higher than extracellular titers at 24 and 48 h PI. All of the tested cell types responded by secreting significant levels of pro-inflammatory cytokines and chemokines in a pattern consistent with recruitment and stimulation of monocytes and macrophages. Based on the elaborated cytokines, we next investigated the cellular interaction of M. genitalium with human monocyte-derived macrophages and characterized the resultant cytokine responses. Macrophages rapidly phagocytosed M. genitalium resulting in a loss of bacterial viability and a potent pro-inflammatory response that included significant secretion of IL-6 and other cytokines associated with enhanced HIV-1 replication. The macrophage-stimulating capacity of M. genitalium was independent of bacterial viability but was sensitive to heat denaturation and proteinase-K digestion suggesting that M. genitalium protein components are the predominant mediators of inflammation. Conclusion: Collectively, the data indicated that human genital ECs were susceptible and immunologically responsive to M. genitalium infection that likely induced cellular immune responses. Although macrophage phagocytosis was an effective method for M. genitalium killing, intracellular localization within vaginal and cervical ECs may provide M. genitalium a survival niche and protection from cellular immune responses thereby facilitating the establishment and maintenance of reproductive tract infection.

The family Mesoniviridae (order Nidovirales) comprises of a group of positive-sense, single-stranded RNA ([+]ssRNA) viruses isolated from mosquitoes.

Three novel insect-specific flaviviruses, isolated from mosquitoes collected in Peru, Malaysia (Sarawak), and the United States, are characterized. The new viruses, designated La Tina, Kampung Karu, and Long Pine Key, respectively, are antigenically and phylogenetically more similar to the mosquito-borne flavivirus pathogens, than to the classical insect-specific viruses like cell fusing agent and Culex flavivirus. The potential implications of this relationship and the possible uses of these and other arbovirus-related insect-specific flaviviruses are reviewed.

Cat fleas, Ctenocephalides felis, are known biological vectors for Rickettsia felis. Rickettsial transmission can be vertical via transovarial transmission within a flea population, as well as horizontal between fleas through a bloodmeal. The previously undescribed infection kinetics of bloodmeal-acquired R. felis in cat fleas provides insight into the R. felis-flea interaction.

The genus Ehrlichia is composed of tick-borne obligate intracellular gram-negative alphaproteobacteria of the family Anaplasmataceae. Ehrlichia includes important pathogens affecting canids (E. canis, E. chaffeensis, and E. ewingii), rodents (E. muris), and ruminants (E. ruminantium). Ehrlichia minasensis, an Ehrlichia closely related to E. canis, was initially reported in Canada and Brazil. This bacterium has now been reported in Pakistan, Malaysia, China, Ethiopia, South Africa, and the Mediterranean island of Corsica, suggesting that E. minasensis has a wide geographical distribution. Previously, E. minasensis was found to cause clinical ehrlichiosis in an experimentally infected calf. The type strain E. minasensis UFMG-EV was successfully isolated from Rhipicephalus microplus ticks and propagated in the tick embryonic cell line of Ixodes scapularis (IDE8). However, the isolation and propagation of E. minasensis strains from cattle has remained elusive. In this study, the E. minasensis strain Cuiabá was isolated from an eight-month-old male calf of Holstein breed that was naturally infected with the bacterium. The calf presented clinical signs and hematological parameters of bovine ehrlichiosis. The in vitro culture of the agent was established in the canine cell line DH82. Ehrlichial morulae were observed using light and electron microscopy within DH82 cells. Total DNA was extracted, and the full genome of the E. minasensis strain Cuiabá was sequenced. A core-genome-based phylogenetic tree of Ehrlichia spp. and Anaplasma spp. confirmed that E. minasensis is a sister taxa of E. canis. A comparison of functional categories among Ehrlichia showed that E. minasensis has significantly less genes in the ‘clustering-based subsystems’ category, which includes functionally coupled genes for which the functional attributes are not well understood. Results strongly suggest that E. minasensis is a novel pathogen infecting cattle. The epidemiology of this Ehrlichia deserves further attention because these bacteria could be an overlooked cause of tick-borne bovine ehrlichiosis, with a wide distribution.

The E3 ubiquitin ligase Pellino 1 (Peli1) is a microglia-specific mediator of autoimmune encephalomyelitis. Its role in neurotropic flavivirus infection is largely unknown. Here, we report that mice deficient in Peli1 (Peli1^–/–) were more resistant to lethal West Nile virus (WNV) infection and exhibited reduced viral loads in tissues and attenuated brain inflammation. Peli1 mediates chemokine and proinflammatory cytokine production in microglia and promotes T cell and macrophage infiltration into the CNS. Unexpectedly, Peli1 was required for WNV entry and replication in mouse macrophages and mouse and human neurons and microglia. It was also highly expressed on WNV-infected neurons and adjacent inflammatory cells from postmortem patients who died of acute WNV encephalitis. WNV passaged in Peli1^–/– macrophages or neurons induced a lower viral load and impaired activation in WT microglia and thereby reduced lethality in mice. Smaducin-6, which blocks interactions between Peli1 and IRAK1, RIP1, and IKKε, did not inhibit WNV-triggered microglia activation. Collectively, our findings suggest a nonimmune regulatory role for Peli1 in promoting microglia activation during WNV infection and identify a potentially novel host factor for flavivirus cell entry and replication.