The influence of centrifugation and incubation temperatures on various veterinary and human chlamydial species

Bacterial ghosts engineered with lipidated antigens as an adjuvant-free vaccine for Chlamydia abortus

Bacterial ghosts (BGs) provide novel vaccine delivery platforms because of their inherent adjuvant properties and efficient antigen delivery capabilities. However, effective engineering strategies are required to modify them for different antigens. In this study, the Escherichia coli (E. coli) ghost was modified by using a lpp'-ompA chimera, a widely used bacterial surface display vector, with a protective antigen macrophage infectivity potentiator (MIP) of Chlamydia abortus (C. abortus), and its protective effect was evaluated in a mouse model. The MIP fusion protein accumulated at 1.2% of the ghost total protein mass and a significant portion of the protein was modified into lipoproteins upon translocation to the BG surface. Lipidated MIP-modified recombinant E. coli ghosts (rECG-lpp'-MIP) effectively promoted antigen-presenting cells (APCs) uptake of antigens and stimulated APCs activation in vivo and in vitro. Immunization with rECG-lpp'-MIP and no adjuvant induced intense specific humoral responses as well as Th1-biased cellular immune responses, which significantly improved the efficiency of C. abortus infection clearance in mice and reduced pathological damage to the uterus. In summary, this study demonstrates that recombinant E. coli ghosts modified with lipidated antigens could help to develop an effective C. abortus vaccine and aid in the development of a universal adjuvant-free vaccine platform.

Comparison of the immune effects of the Chlamydia abortus MOMP antigen displayed in different parts of bacterial ghosts

Bacterial ghosts (BGs) are promising vaccine platforms owing to their high adjuvant properties and delivery efficiency. Heterologous antigens can be anchored to different parts of BGs using genetic engineering strategies to prepare vaccines. However, several key issues need to be resolved, including the efficient preparation of BGs and determining the optimal anchoring position of exogenous antigens in the BGs. Here, we prepared an efficient temperature-controlled lysis system using lysis gene E of phage PhiX174 and used the major outer membrane protein (MOMP) of Chlamydia abortus (C. abortus) as a model antigen to explore the optimal display location of exogenous antigens in BGs. We demonstrated that the constructed recombinant temperature-controlled lysis plasmid can still stably inhibit E gene expression at 37°C, and the lysis efficiency of E. coli can reach above 99.9%. Four recombinant MOMP Escherichia coli (E. coli) ghost vaccines were constructed using different anchor sequences. These vaccines all induced strong specific antibody responses and secrete high levels of IFN-γ in immunized mice and significantly increased the clearance of C. abortus in a mouse infection model. Notably, the strongest immune effect was observed when MOMP was displayed on the surface of E. coli ghosts (rECG-InpN-M), which resulted in the clearance of C. abortus in mice 6 days earlier than that with the recombinant MOMP vaccine. Altogether, we constructed an efficient BG temperature-controlled lysis system and provided a feasible strategy for developing a BG delivery platform with enhanced immune effects.

Neisseria gonorrhoeae Coinfection during Chlamydia muridarum Genital Latency Does Not Modulate Murine Vaginal Bacterial Shedding

Chlamydia trachomatis and Neisseria gonorrhoeae are the most frequently reported agents of bacterial sexually transmitted disease worldwide. Nonetheless, C. trachomatis/N. gonorrhoeae coinfection remains understudied. C. trachomatis/N. gonorrhoeae coinfections are more common than expected by chance, suggesting C. trachomatis/N. gonorrhoeae interaction, and N. gonorrhoeae infection may reactivate genital chlamydial shedding in women with latent (quiescent) chlamydial infection. We hypothesized that N. gonorrhoeae would reactivate latent genital Chlamydia muridarum infection in mice. Two groups of C. muridarum-infected mice were allowed to transition into genital latency. One group was then vaginally inoculated with N. gonorrhoeae; a third group received N. gonorrhoeae alone. C. muridarum and N. gonorrhoeae vaginal shedding was measured over time in the coinfected and singly infected groups. Viable C. muridarum was absent from vaginal swabs but detected in rectal swabs, confirming C. muridarum genital latency and consistent with the intestinal tract as a C. muridarum reservoir. C. muridarum inclusions were observed in large intestinal, but not genital, tissues during latency. Oviduct dilation was associated with C. muridarum infection, as expected. Contradicting our hypothesis, N. gonorrhoeae coinfection did not reactivate latent C. muridarum vaginal shedding. In addition, latent C. muridarum infection did not modulate recovery of vaginal viable N. gonorrhoeae. Evidence for N. gonorrhoeae-dependent increased C. muridarum infectivity has thus not been demonstrated in murine coinfection, and the ability of C. muridarum coinfection to potentiate N. gonorrhoeae infectivity may depend on actively replicating vaginal C. muridarum. The proportion of mice with increased vaginal neutrophils (PMNs) was higher in N. gonorrhoeae-infected than in C. muridarum-infected mice, as expected, while that of C. muridarum/N. gonorrhoeae-coinfected mice was intermediate to the singly infected groups, suggesting latent C. muridarum murine infection may limit PMN response to subsequent N. gonorrhoeae infection. IMPORTANCE Our work builds upon the limited understanding of C. muridarum/N. gonorrhoeae coinfection. Previously, N. gonorrhoeae infection of mice with acute (actively replicating) vaginal C. muridarum infection was shown to increase recovery of viable vaginal N. gonorrhoeae and vaginal PMNs, with no effect on C. muridarum vaginal shedding (R. A. Vonck et al., Infect Immun 79:1566-1577, 2011). It has also been shown that chlamydial infection of human and murine PMNs prevents normal PMN responses, including the response to N. gonorrhoeae (K. Rajeeve et al., Nat Microbiol 3:824-835, 2018). Our findings show no effect of latent genital C. muridarum infection on the recovery of viable N. gonorrhoeae, in contrast to the previously reported effect of acute C. muridarum infection, and suggesting that acute versus latent C. muridarum infection may have distinct effects on PMN function in mice. Together, these studies to date provide evidence that Chlamydia/N. gonorrhoeae synergistic interactions may depend on the presence of replicating Chlamydia in the genital tract, while chlamydial effects on vaginal PMNs may extend beyond acute infection.

Beta lactamase-producing Neisseria gonorrhoeae alleviates Amoxicillin-induced chlamydial persistence in a novel in vitro co-infection model

Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) cause most bacterial sexually transmitted infections (STIs) worldwide. Epidemiological studies have shown high percentages of co-infections with CT/NG and indicate that NG co-infection can reactivate CT shedding during persistent chlamydial infection. These data also suggest that biological interaction between the two bacteria may increase susceptibility or transmissibility. CT is an obligate intracellular bacterium with a developmental cycle that alternates between two forms: infectious elementary bodies (EBs) which invade the epithelium and non-infectious reticulate bodies (RBs) which divide and replicate inside the inclusion. Adverse environmental conditions can interrupt chlamydial development, with a consequent temporary halt in RB division, reduction in infectious EB production and formation of enlarged chlamydiae (aberrant bodies, ABs) - characterizing chlamydial persistence. When the stressor is removed, the chlamydial developmental cycle is restored, together with production of infectious EBs. The beta-lactam amoxicillin (AMX) induces chlamydial persistence, both in vitro and in mice. We investigated the impact of penicillinase-producing NG strain (PPNG) on AMX-persistent chlamydial infection utilizing our recently developed, contact-independent in vitro model of co-infection. We hypothesized that co-infection with PPNG could prevent and/or reverse AMX-induced chlamydial persistence. Our results showed that PPNG can ameliorate AMX-persistence in two chlamydial species, CT and C. muridarum (CM), providing novel evidence for a range of Chlamydia/NG interactions.

Refinement of water-filtered infrared A (wIRA) irradiations of in vitro acute and persistent chlamydial infections

Water-filtered infrared A (wIRA) alone or in combination with visible light (VIS) exerts anti-chlamydial effects in vitro and in vivo in acute infection models. However, it has remained unclear whether reduced irradiation duration and irradiance would still maintain anti-chlamydial efficacy. Furthermore, efficacy of this non-chemical treatment option against persistent (chronic) chlamydial infections has not been investigated to date. To address this knowledge gap, we evaluated 1) irradiation durations of 5, 15 or 30 min in genital and ocular Chlamydia trachomatis acute infection models, 2) irradiances of 100, 150 or 200 mW/cm² in the acute genital infection model and 3) anti-chlamydial activity of wIRA and VIS against C. trachomatis serovar B and E with amoxicillin (AMX)- or interferon γ (IFN-γ)-induced persistence. Reduction of irradiation duration reduced anti-chlamydial efficacy. Irradiances of 150 to 200 mW/cm², but not 100 mW/cm², induced anti-chlamydial effects. For persistent infections, wIRA and VIS irradiation showed robust anti-chlamydial activity independent of the infection status (persistent or recovering), persistence inducer (AMX or IFN-γ) or chlamydial strain (serovar B or E). This study clarifies the requirement of 30 min irradiation duration and 150 mW/cm² irradiance to induce significant anti-chlamydial effects in vitro, supports the use of irradiation in the wIRA and VIS spectrum as a promising non-chemical treatment for chlamydial infections and provides important information for follow-up in vivo studies. Notably, wIRA and VIS exert anti-chlamydial effects on persistent chlamydiae which are known to be refractory to antibiotic treatment.

Neisseria gonorrhoeae Limits Chlamydia trachomatis Inclusion Development and Infectivity in a Novel In Vitro Co-Infection Model

Chlamydia trachomatis (Ct) and Neisseria gonorrhoeae (Ng) are the most common bacterial sexually transmitted infections (STIs) worldwide. The primary site of infection for both bacteria is the epithelium of the endocervix in women and the urethra in men; both can also infect the rectum, pharynx and conjunctiva. Ct/Ng co-infections are more common than expected by chance, suggesting Ct/Ng interactions increase susceptibility and/or transmissibility. To date, studies have largely focused on each pathogen individually and models exploring co-infection are limited. We aimed to determine if Ng co-infection influences chlamydial infection and development and we hypothesized that Ng-infected cells are more susceptible to chlamydial infection than uninfected cells. To address this hypothesis, we established an in vitro model of Ct/Ng co-infection in cultured human cervical epithelial cells. Our data show that Ng co-infection elicits an anti-chlamydial effect by reducing chlamydial infection, inclusion size, and subsequent infectivity. Notably, the anti-chlamydial effect is dependent on Ng viability but not extracellular nutrient depletion or pH modulation. Though this finding is not consistent with our hypothesis, it provides evidence that interaction of these bacteria in vitro influences chlamydial infection and development. This Ct/Ng co-infection model, established in an epithelial cell line, will facilitate further exploration into the pathogenic interplay between Ct and Ng.

Evidence for the existence of a new genus Chlamydiifrater gen. nov. inside the family Chlamydiaceae with two new species isolated from flamingo (Phoenicopterus roseus): Chlamydiifrater phoenicopteri sp. nov. and Chlamydiifrater volucris sp. nov

The family Chlamydiaceae currently comprises a single genus Chlamydia, with 11 validly published species and seven more taxa. It includes the human pathogens Chlamydia (C.) trachomatis, C. pneumoniae and C. psittaci, a zoonotic agent causing avian chlamydiosis and human psittacosis, as well as other proven or potential pathogens in ruminants, birds, snakes, reptiles and turtles. During routine testing of 15 apparently healthy captive flamingos in a zoo in 2011, an atypical strain of Chlamydiaceae was detected by real-time PCR of cloacal swab samples. Sequence analysis of the 16S rRNA gene revealed high similarity to the uncultured Chlamydiales bacterium clone 122, which previously had been found in gulls. As more samples were collected during annual campaigns of the flamingo ringing program in southern France from 2012 to 2015, Chlamydiaceae-specific DNA was detected by PCR in 30.9% of wild birds. From these samples, three strains were successfully grown in cell culture. Ultrastructural analysis, comparison of 16S and 23S rRNA gene sequences, whole-genome analysis based on de novo hybrid-assembled sequences of the new strains as well as subsequent calculation of taxonomic parameters revealed that the relatedness of the flamingo isolates to established members of the family Chlamydiaceae was sufficiently distant to indicate that the three strains belong to two distinct species within a new genus. Based on these data, we propose the introduction of Chlamydiifrater gen. nov., as a new genus, and Chlamydiifrater phoenicopteri sp. nov. and Chlamydiifrater volucris sp. nov., as two new species of the genus.

Maraviroc, celastrol and azelastine alter Chlamydia trachomatis development in HeLa cells

Introduction . Chlamydia trachomatis (Ct) is an obligate intracellular bacterium, causing a range of diseases in humans. Interactions between chlamydiae and antibiotics have been extensively studied in the past.Hypothesis/Gap statement: Chlamydial interactions with non-antibiotic drugs have received less attention and warrant further investigations. We hypothesized that selected cytokine inhibitors would alter Ct growth characteristics in HeLa cells.Aim. To investigate potential interactions between selected cytokine inhibitors and Ct development in vitro.Methodology. The CCR5 receptor antagonist maraviroc (Mara; clinically used as HIV treatment), the triterpenoid celastrol (Cel; used in traditional Chinese medicine) and the histamine H1 receptor antagonist azelastine (Az; clinically used to treat allergic rhinitis and conjunctivitis) were used in a genital in vitro model of Ct serovar E infecting human adenocarcinoma cells (HeLa).Results. Initial analyses revealed no cytotoxicity of Mara up to 20 µM, Cel up to 1 µM and Az up to 20 µM. Mara exposure (1, 5, 10 and 20 µM) elicited a reduction of chlamydial inclusion numbers, while 10 µM reduced chlamydial infectivity. Cel 1 µM, as well as 10 and 20 µM Az, reduced chlamydial inclusion size, number and infectivity. Morphological immunofluorescence and ultrastructural analysis indicated that exposure to 20 µM Az disrupted chlamydial inclusion structure. Immunofluorescence evaluation of Cel-incubated inclusions showed reduced inclusion sizes whilst Mara incubation had no effect on inclusion morphology. Recovery assays demonstrated incomplete recovery of chlamydial infectivity and formation of structures resembling typical chlamydial inclusions upon Az removal.Conclusion. These observations indicate that distinct mechanisms might be involved in potential interactions of the drugs evaluated herein and highlight the need for continued investigation of the interaction of commonly used drugs with Chlamydia and its host.

Lipofectamine enhances Chlamydia infectivity in cell culture

Cultivation of Chlamydia species in cell lines requires centrifugation of the inoculum onto diethylaminoethyl-dextran-pretreated cell monolayers to improve the infection efficiency. Here we report that the addition of DNA transfection reagent Lipofectamine in the inoculum significantly enhances the infectivity of Chlamydia abortus in mouse fibroblast McCoy cells, with an infection efficiency equivalent to that of the centrifugation method. Similar enhancement effects of Lipofectamine on the infectivity of C. psittaci and C. trachomatis were also observed. This study provides an alternative and convenient method for the cultivation of Chlamydia species in vitro in the absence of centrifugation.

Thermal field formation during wIRA-hyperthermia: temperature measurements in skin and subcutis of piglets as a basis for thermotherapy of superficial tumors and local skin infections caused by thermosensitive microbial pathogens

Purpose: The temporal and spatial formation of the temperature field and its changes during/upon water-filtered infrared-A (wIRA)-irradiation in porcine skin and subcutis were investigated in vivo in order to get a detailed physical basis for thermotherapy of superficial tumors and infections caused by thermosensitive microbial pathogens (e.g., Mycobacterium ulcerans causing Buruli ulcer). Methods: Local wIRA-hyperthermia was performed in 11 anesthetized piglets using 85.0 mW cm^-2, 103.2 mW cm^-2 and 126.5 mW cm^-2, respectively. Invasive temperature measurements were carried out simultaneously in 1-min intervals using eight fiber-optical probes at different tissue depths between 2 and 20 mm, and by an IR thermometer at the skin surface. Results: Tissue temperature distribution depended on incident irradiance, exposure time, tissue depths and individual 'physiologies' of the animals. Temperature maxima were found at depths between 4 and 7 mm, exceeding skin surface temperatures by about 1-2 K. Tissue temperatures above 37 °C, necessary to eradicate M. ulcerans at depths <20 mm, were reached reliably. Conclusions: wIRA-hyperthermia may be considered as a novel therapeutic option for treatment of local skin infections caused by thermosensitive pathogens (e.g., in Buruli ulcer). To ensure temperatures required for heat treatment of superficial tumors deeper than 4 mm, the incident irradiance needed can be controlled either by (a) invasive temperature measurements or (b) control of skin surface temperature and considering possible temperature increases up to 1-2 K in underlying tissue.

A cluster of Chlamydia serpentis cases in captive snakes

Following the occurrence of sudden death cases in a zoo reptile collection, histological analyses conducted on tissues from two common adders suggested an infection due to Chlamydia. The survey was extended to 22 individual snakes from the same collection and a PCR analysis targeting a conserved gene in Chlamydiaceae revealed bacterial shedding in six of them. The infection resolved spontaneously in one snake whereas another one succumbed one month later. The antibiotic treatment administered (marbofloxacin) to the remaining four PCR positive animals stopped the mortalities and the shedding. Analysis of the 16S and 23S ribosomal gene sequences identified C. serpentis, a recently described novel chlamydial species in snakes. A PCR tool for a quick and specific identification of this new chlamydial species was developed in this study.