Pf bacteriophage are temperate phages that infect the bacterium Pseudomonas aeruginosa, a major cause of chronic lung infections in cystic fibrosis (CF) and other settings. Pf and other temperate phages have evolved complex, mutualistic relationships with their bacterial hosts that impact both bacterial phenotypes and chronic infection. We and others have reported that Pf phages are a virulence factor that promote the pathogenesis of P. aeruginosa infections in animal models and are associated with worse skin and lung infections in humans. Here we review the biology of Pf phage and what is known about its contributions to pathogenesis and clinical disease. First, we review the structure, genetics, and epidemiology of Pf phage. Next, we address the diverse and surprising ways that Pf phages contribute to P. aeruginosa phenotypes including effects on biofilm formation, antibiotic resistance, and motility. Then, we cover data indicating that Pf phages suppress mammalian immunity at sites of bacterial infection. Finally, we discuss recent literature implicating Pf in chronic P. aeruginosa infections in CF and other settings. Together, these reports suggest that Pf bacteriophage have direct effects on P. aeruginosa infections and that temperate phages are an exciting frontier in microbiology, immunology, and human health.

The zoonotic, vector-borne parasite Trypanosoma cruzi causes Chagas disease throughout the Americas, but human and veterinary health burdens in the United States are unknown. We conducted a cross-sectional prevalence study in indigent, medically underserved human and cohabiting canine populations of seven south Texas border communities, known as colonias. Defining positivity as those samples that were positive on two or more independent tests, we found 1.3% seroprevalence in 233 humans, including one child born in the United States with only short-duration travel to Mexico. Additionally, a single child with no travel outside south Texas was positive on only a single test. Among 209 dogs, seroprevalence was 19.6%, but adjusted to 31.6% when including those dogs positive on only one test and extrapolating potential false negatives. Parasite DNA was detected in five dogs, indicating potential parasitemia. Seropositive dogs lived in all sampled colonias with no difference in odds of positivity across age, sex, or breed. Colonia residents collected two adult Triatoma gerstaeckeri and one nymph triatomine from around their homes; one of three bugs was infected with T. cruzi, and blood meal hosts were molecularly determined to include dog, human, and raccoon. Dogs and the infected vector all harbored T. cruzi discrete typing unit I, which has previously been implicated in human disease in the United States. Colonias harbor active T. cruzi transmission cycles and should be a priority in outreach and vector control initiatives.

Pseudomonas aeruginosa (Pa) is a Gram-negative bacterium which is associated with chronic diabetic wounds as well as potentially deadly lung infections in cystic fibrosis patients. Approximately 51,000 cases of Pa infections occur annually; of these cases, 13% are resistant to antibiotics which results in the deaths of ~400 individuals every year. Diversity between Pa strains presents a challenge in developing a vaccine or therapeutic capable of resolving infections caused by different strains. Pf phage (a filamentous bacteriophage) has been found in Pa from chronic diabetic wound isolates and has been show to increase virulence of Pa. Recent findings by our team indicate that a Pf phage-targeted vaccine or monoclonal antibody provide protection from the establishment of Pa infection in mice. To further improve this innovative new vaccine targeting Pa, adjuvant systems were used to enhance humoral response to the vaccine. A consensus peptide from Pf Phage coat protein was conjugated to the carrier protein CRM197 and combined with novel adjuvants and delivery systems. Selected adjuvants significantly enhanced humoral immunity to the Pf Phage peptide in a dose-dependent manner. Combination adjuvant systems were also used to further enhance antigen-specific immunity to Pf Phage and cell-mediated immunity to the carrier protein. The development of an adjuvanted Pf phage vaccine to protect against Pa infections is a new and innovative strategy with the potential to protect patients at risk for opportunistic bacterial infections.

Pseudomonas aeruginosa (Pa) is a bacterial pathogen associated with chronic diabetic wounds as well as potentially deadly lung infections in cystic fibrosis patients. Pa is listed by the WHO as “Priority 1” in the Priority Pathogens list and results in hundreds of deaths each year. Pa diversity presents a challenge in developing a vaccine or therapeutic capable of resolving infections caused by different Pa clinical isolates. Filamentous Pf phages (a virus) infect the majority of Pa strains. Additionally, the presence Pf phage is a key virulence factor contributing to Pa infections. Pf is a filamentous-lysogenic phage that is primarily comprised of repeats of coat protein (CoaB). A consensus peptide derived from the coat protein was identified and used as the antigen for our phage vaccine targeted vaccine. This conjugate vaccine targeting Pf phage induced protection against Pa wound challenges in mice. Additionally, our team has implemented the use of a novel TLR4 agonist to further enhance antibody response against Pf coat protein intact Pf phage virions. Based on their amino acid sequence homology, clinical isolates of Pa and associated Pf phage were divided into two major clades. We prepared CRM-197 conjugates using the consensus peptides from both clades. Vaccination with these multivalent conjugates in combination with a novel synthetic TLR4 agonist (adjuvant) boosts antibody response against the peptides and promotes antibody cross-recognition between peptides. Creating a safe and effective vaccine that can mount a robust immune response against both clades of Pf phage is an important advancement towards the development and clinical testing of phage based vaccine targeting deadly Pa infections. Supported by R01 AI138981-01

Pseudomonas aeruginosa (Pa) is a Gram-negative bacterium which is associated with chronic diabetic wounds as well as potentially deadly lung infections in cystic fibrosis patients. Approximately 51,000 cases of Pa infections occur annually; of these cases, 13% are resistant to antibiotics which results in the deaths of ~400 individuals every year. Diversity between Pa strains presents a challenge in developing a vaccine or therapeutic capable of resolving infections caused by different strains. Pf phage (a filamentous bacteriophage) has been found in Pa from chronic diabetic wound isolates and has been show to increase virulence of Pa. Recent findings by our team indicate that a Pf phage-targeted vaccine or monoclonal antibody provide protection from the establishment of Pa infection in mice. To further improve this innovative new vaccine targeting Pa, adjuvant systems were used to enhance humoral response to the vaccine. A consensus peptide from Pf Phage coat protein was conjugated to the carrier protein CRM197 and combined with novel adjuvants and delivery systems. Selected adjuvants significantly enhanced humoral immunity to the Pf Phage peptide in a dose-dependent manner. Combination adjuvant systems were also used to further enhance antigen-specific immunity to Pf Phage and cell-mediated immunity to the carrier protein. The development of an adjuvanted Pf phage vaccine to protect against Pa infections is a new and innovative strategy with the potential to protect patients at risk for opportunistic bacterial infections.