Vaccine Protection against Multidrug-Resistant Klebsiella pneumoniae in a Nonhuman Primate Model of Severe Lower Respiratory Tract Infection

Abstract

Klebsiella pneumoniae is a human gut communal organism and notorious opportunistic pathogen. The relative high burden of asymptomatic colonization by K. pneumoniae is often compounded by multidrug resistance—a potential problem for individuals with significant comorbidities or other risk factors for infection. A carbapenem-resistant K. pneumoniae strain classified as multilocus sequence type 258 (ST258) is widespread in the United States and is usually multidrug resistant. Thus, treatment of ST258 infections is often difficult. Inasmuch as new preventive and/or therapeutic measures are needed for treatment of such infections, we developed an ST258 pneumonia model in cynomolgus macaques and tested the ability of an ST258 capsule polysaccharide type 2 (CPS2) vaccine to moderate disease severity. Compared with sham-vaccinated animals, those vaccinated with ST258 CPS2 had significantly less disease as assessed by radiography 24 h after intrabronchial installation of 108 CFU of ST258. All macaques vaccinated with CPS2 ultimately developed ST258-specific antibodies that significantly enhanced serum bactericidal activity and killing of ST258 by macaque neutrophils ex vivo. Consistent with a protective immune response to CPS2, transcripts encoding inflammatory mediators were increased in infected lung tissues obtained from CPS-vaccinated animals compared with control, sham-vaccinated macaques. Taken together, our data provide support for the idea that vaccination with ST258 CPS can be used to prevent or moderate infections caused by ST258. As with studies performed decades earlier, we propose that this prime-boost vaccination approach can be extended to include multiple capsule types. IMPORTANCE Multidrug-resistant bacteria continue to be a major problem worldwide, especially among individuals with significant comorbidities and other risk factors for infection. K. pneumoniae is among the leading causes of health care-associated infections, and the organism is often resistant to multiple classes of antibiotics. A carbapenem-resistant K. pneumoniae strain known as multilocus sequence type 258 (ST258) is the predominant carbapenem-resistant Enterobacteriaceae in the health care setting in the United States. Infections caused by ST258 are often difficult to treat and new prophylactic measures and therapeutic approaches are needed. To that end, we developed a lower respiratory tract infection model in cynomolgus macaques in which to test the ability of ST258 CPS to protect against severe ST258 infection.

The Role of IgG Subclass in Antibody-Mediated Protection against Carbapenem-Resistant Klebsiella pneumoniae

“…Data in humans has shown that neutropenic patients may have reduced survival in cases of bacteremia caused by CR-Kp and other carbapenem-resistant Enterobacteriaceae (23). In mice, some studies have shown neutrophils to be important in CR-Kp clearance (15,27), while others have shown them to be less valuable (25). Using a tube-based incubation assay with human neutrophils, we observed both antibodies to promote neutrophil-dependent killing of MMC39 in the presence of 5% autologous serum at 40 g/ml (Fig.…”

“…The relative contributions of macrophages, monocytes, and neutrophils to CR-Kp clearance has been disputed. While evidence using cell-specific depletions in mice strongly suggested that lung clearance of CR-Kp is predominantly mediated by CCR2positive macrophages over neutrophils (25), studies examining the role of human and primate neutrophils in CR-Kp clearance have shown their efficacy in clearing bacteria in vitro (15,27,47). These contributions matter significantly to the field of anti-infective antibody therapy in the context of CR-Kp, as up to 86% of patients with CR-Kp bacteremia are neutropenic, and these patients have been found to face worse prognoses than patients without neutropenia (19,23).…”

“…Therefore, future studies of CR-Kp anticapsular antibodies should investigate several to better sample their potential. Finally, future studies of anti-CR-Kp antibodies must innovate the field of in vivo models used to study CR-Kp infection, as convenient and effective models that reproduce the chronic, persistent infection caused by CR-Kp in humans have been difficult to develop (27).…”

The Role of IgG Subclass in Antibody-Mediated Protection against Carbapenem-ResistantKlebsiella pneumoniae

“…In mice, some studies have shown neutrophils to be important in CR-Kp clearance (15,29), while others have shown them to be less valuable (26). Using a tube-based incubation assay with human neutrophils, we observed both antibodies to promote neutrophil-dependent killing of MMC39 in the presence of 5% autologous serum at 40µg/mL ( Figure 3C).…”

“…The relative contributions of macrophages, monocytes, and neutrophils to CR-Kp clearance has been disputed. While evidence using cell-specific depletions in mice strongly suggested that lung clearance of CR-Kp is predominantly mediated by CCR2 positive macrophages over neutrophils (26), studies examining the role of human and primate neutrophils in CR-Kp clearance have shown their efficacy in clearing bacteria in vitro (15,29,49). These contributions matter significantly to the field of anti-infective antibody therapy in the context of CR-Kp, as up to 86% of patients with CR-Kp bacteremia are neutropenic, and these patients have been found to fare worse prognoses than patients without neutropenia (19,28).…”