Biological effects of chlamydiaphage phiCPG1 capsid protein Vp1 on chlamydia trachomatis in vitro and in vivo

Insights into the Two Most Common Cancers of Primitive Gut-Derived Structures and Their Microbial Connections

The gastrointestinal and respiratory systems are closely linked in different ways, including from the embryological, anatomical, cellular, and physiological angles. The highest number (and various types) of microorganisms live in the large intestine/colon, and constitute the normal microbiota in healthy people. Adverse alterations of the microbiota or dysbiosis can lead to chronic inflammation. If this detrimental condition persists, a sequence of pathological events can occur, such as inflammatory bowel disease, dysplasia or premalignant changes, and finally, cancer. One of the most commonly identified bacteria in both inflammatory bowel disease and colon cancer is Escherichia coli. On the other hand, patients with inflammatory bowel disease are at risk of several other diseases-both intestinal (such as malnutrition and intestinal obstruction, besides cancer) and extraintestinal (such as arthritis, bronchiectasis, and cancer risk). Cancers of the lung and colon are the two most common malignancies occurring worldwide (except for female breast cancer). Like the bacterial role in colon cancer, many studies have shown a link between chronic Chlamydia pneumoniae infection and lung cancer. However, in colon cancer, genotoxic colibactin-producing E. coli belonging to the B2 phylogroup may promote tumorigenesis. Furthermore, E. coli is believed to play an important role in the dissemination of cancer cells from the primary colonic site. Currently, seven enteric pathogenic E. coli subtypes have been described. Conversely, three Chlamydiae can cause infections in humans (C. trachomatis may increase the risk of cervical and ovarian cancers). Nonetheless, striking genomic plasticity and genetic modifications allow E. coli to constantly adjust to the surrounding environment. Consequently, E. coli becomes resistant to antibiotics and difficult to manage. To solve this problem, scientists are thinking of utilizing suitable lytic bacteriophages (viruses that infect and kill bacteria). Several bacteriophages of E. coli and Chlamydia species are being evaluated for this purpose.

Potential for Phages in the Treatment of Bacterial Sexually Transmitted Infections

Bacterial sexually transmitted infections (BSTIs) are becoming increasingly significant with the approach of a post-antibiotic era. While treatment options dwindle, the transmission of many notable BSTIs, including Neisseria gonorrhoeae, Chlamydia trachomatis, and Treponema pallidum, continues to increase. Bacteriophage therapy has been utilized in Poland, Russia and Georgia in the treatment of bacterial illnesses, but not in the treatment of bacterial sexually transmitted infections. With the ever-increasing likelihood of antibiotic resistance prevailing and the continuous transmission of BSTIs, alternative treatments must be explored. This paper discusses the potentiality and practicality of phage therapy to treat BSTIs, including Neisseria gonorrhoeae, Chlamydia trachomatis, Treponema pallidum, Streptococcus agalactiae, Haemophilus ducreyi, Calymmatobacterium granulomatis, Mycoplasma genitalium, Ureaplasma parvum, Ureaplasma urealyticum, Shigella flexneri and Shigella sonnei. The challenges associated with the potential for phage in treatments vary for each bacterial sexually transmitted infection. Phage availability, bacterial structure and bacterial growth may impact the potential success of future phage treatments. Additional research is needed before BSTIs can be successfully clinically treated with phage therapy or phage-derived enzymes.

Applications of bacteriophages against intracellular bacteria

Infectious diseases pose a significant threat to both human and animal populations. Intracellular bacteria are a group of pathogens that invade and survive within the interior of eukaryotic cells, which in turn protect them from antibacterial drugs and the host immune system. Limited penetration of antibacterials into host cells results in insufficient bacterial clearance and treatment failure. Bacteriophages have, over the decades, been proved to play an important role in combating bacterial infections (phage therapy), making them an important alternative to classical antibiotic strategies today. Phages have been found to be effective at killing various species of extracellular bacteria, but little is still known about how phages control intracellular infections. With advances in phage genomics and mechanisms of delivery and cell uptake, the development of phage-based antibacterial strategies to address the treatment of intracellular bacteria has general potential. In this review, we present the current state of knowledge regarding the application of bacteriophages against intracellular bacteria. We cover phage deployment against the most common intracellular pathogens with special attention to therapeutic and preventive strategies.

The ΦCPG1 chlamydiaphage can infect Chlamydia trachomatis and significantly reduce its infectivity

Recent years have seen a significant increase in rates of persistent, antibiotic-resistant infection of Chlamydia trachomatis (CT) infections, representing an increasingly serious public health threat. At present there are no effective vaccines or antibodies available to treat CT, prompting the need for novel treatment strategies. One potential solution to this issue is the use of ΦCPG1, a chlamydia-specific lytic phage which has over 90% nucleotide sequence identity with other chlamydiaphages. Previous work has shown the Vp1 capsid protein of ΦCPG1 to exhibit broad inhibitory activity against all CT serotypes, inhibiting CT-mediated host cell toxicity. Patients with CT infections exhibit circulating antibodies against this Vp1 protein, suggesting that this or similar phages may be present in vivo in the context of CT infections, even though no phages have been specifically detected to date. Given these previous findings, we hypothesized that the ΦCPG1 chlamydiaphage may be able to infect CT, thereby inhibiting its growth and proliferation. To test this, we generated a recombinant pGFP-ΦCPG1 phage which we used to explore its effects on CT and chlamydia conjunctivitis of guinea pigs (GPIC). We found that pGFP insertion did not alter the packaging or infectivity of ΦCPG1, and that this recombinant phage was readily able to infect CT and GPIC and inhibit CT and GPIC in a dose-dependent fashion. This inhibition was most pronounced during the mid and late stages of the CT infection, disrupting the reticular body (RB) to EB transition, leading to the formation of enlarged RBs. These results indicate that ΦCPG1 is able to infect CT, highlighting this phage as a novel potential therapeutic agent for treating chlamydia infections. In addition, by engineering pGFP to express ΦCPG1, we have produced an valuable experimental tool useful for future studies of drug resistance, pathogenicity, and vaccine research aimed at improving CT treatment.

Capsid protein Vp1 from chlamydiaphage φCPG1 effectively alleviates cytotoxicity induced by Chlamydia trachomatis

Chlamydia trachomatis is the leading cause of sexually transmitted bacterial infections. C. trachomatis genital infection may lead to pelvic inflammatory disease, ectopic pregnancy and tubal infertility, which are major public health problems. However, the pathogenic mechanisms of this bacterium remain unclear, and the efficacy of clinical therapeutics is unsatisfactory. In the current study, whether Vp1 can alleviate the cytotoxicity induced by Chlamydia trachomatis infection was investigated. C. trachomatis was pre-treated with BSA or purified Vp1 protein and used to infect HeLa cells. It was observed that Vp1 significantly inhibited the infectivity of C. trachomatis in cell cultures. In addition, the Vp1 pretreatment reduced the chlamydial Hsp60 protein levels and decreased the C. trachomatis inclusion number. The Vp1 pretreatment also prevented C. trachomatis-induced cytotoxicity in host cells. Furthermore, the chlamydial suppression of host cell proapoptotic p53 protein and the induction of antiapoptotic cIAP-2 and Mcl-1 gene expression were reversed by the Vp1 pretreatment. These observations suggest that Vp1 has a clear inhibitory effect on C. trachomatis growth in vitro.

PmpI antibody reduces the inhibitory effect of Vp1 on Chlamydia trachomatis infectivity

Chlamydia trachomatis is the most common cause of bacterial sexually transmitted infections. The effect of antibiotic treatment is not satisfactory, and there is currently no vaccine to prevent C. trachomatis infection. Our results showed that Chlamydia virus CPG1 capsid protein Vp1 treatment significantly inhibited C. trachomatis growth in cell culture, and the inclusion numbers of different C. trachomatis serotypes were decreased. In addition, we conducted a preliminary investigation of the possible mechanisms behind the Vp1 inhibition effects and the C. trachomatis molecules targeted by Vp1. Using far-western blot and GST pull-down assay, we found that purified Vp1 can bind to the C. trachomatis outer membrane protein PmpI. PmpI polyclonal antibody treatment markedly reduced the inhibitory effect of Vp1 on C. trachomatis infectivity. On the basis of these experimental results, we infer that PmpI participates in the inhibitory effect of Vp1 and may be a potential receptor of Vp1 in the outer membrane of C. trachomatis. Our research provides clues regarding the molecular mechanisms underlying the interactions between chlamydia virus and chlamydia.