Klebsiella pneumoniae presents as two circulating pathotypes: classical K. pneumoniae (cKp) and hypervirulent K. pneumoniae (hvKp). Classical isolates are considered urgent threats due to their antibiotic resistance profiles, while hvKp isolates have historically been antibiotic susceptible. Recently, however, increased rates of antibiotic resistance have been observed in both hvKp and cKp, further underscoring the need for preventive and effective immunotherapies. Two distinct surface polysaccharides have gained traction as vaccine candidates against K. pneumoniae: capsular polysaccharide and the O-antigen of lipopolysaccharide. While both targets have practical advantages and disadvantages, it remains unclear which of these antigens included in a vaccine would provide superior protection against matched K. pneumoniae strains. Here, we report the production of two bioconjugate vaccines, one targeting the K2 capsular serotype and the other targeting the O1 O-antigen. Using murine models, we investigated whether these vaccines induced specific antibody responses that recognize K2:O1 K. pneumoniae strains. While each vaccine was immunogenic in mice, both cKp and hvKp strains exhibited decreased O-antibody binding in the presence of capsule. Further, O1 antibodies demonstrated decreased killing in serum bactericidal assays with encapsulated strains, suggesting that the presence of K. pneumoniae capsule blocks O1-antibody binding and function. Finally, the K2 vaccine outperformed the O1 vaccine against both cKp and hvKp in two different murine infection models. These data suggest that capsule-based vaccines may be superior to O-antigen vaccines for targeting hvKp and some cKp strains, due to capsule blocking the O-antigen.

O-antigen, capsular polysaccharide, Klebsiella pneumoniae

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

*O[C@H]1[C@H]([C@H](O)CO)O[C@@H](O[C@@H]2[C@@H](O)[C@@H](*)O[C@H](CO)[C@@H]2O)[C@@H]1O

324.282 g/mol (C₁₂H₂₀R₂O₁₀, R = next and previous repeats, not counted in mol weight)

Klebsiella pneumoniae presents as two circulating pathotypes: classical K. pneumoniae (cKp) and hypervirulent K. pneumoniae (hvKp). Classical isolates are considered urgent threats due to their antibiotic resistance profiles, while hvKp isolates have historically been antibiotic susceptible. Recently, however, increased rates of antibiotic resistance have been observed in both hvKp and cKp, further underscoring the need for preventive and effective immunotherapies. Two distinct surface polysaccharides have gained traction as vaccine candidates against K. pneumoniae: capsular polysaccharide and the O-antigen of lipopolysaccharide. While both targets have practical advantages and disadvantages, it remains unclear which of these antigens included in a vaccine would provide superior protection against matched K. pneumoniae strains. Here, we report the production of two bioconjugate vaccines, one targeting the K2 capsular serotype and the other targeting the O1 O-antigen. Using murine models, we investigated whether these vaccines induced specific antibody responses that recognize K2:O1 K. pneumoniae strains. While each vaccine was immunogenic in mice, both cKp and hvKp strains exhibited decreased O-antibody binding in the presence of capsule. Further, O1 antibodies demonstrated decreased killing in serum bactericidal assays with encapsulated strains, suggesting that the presence of K. pneumoniae capsule blocks O1-antibody binding and function. Finally, the K2 vaccine outperformed the O1 vaccine against both cKp and hvKp in two different murine infection models. These data suggest that capsule-based vaccines may be superior to O-antigen vaccines for targeting hvKp and some cKp strains, due to capsule blocking the O-antigen.

O-antigen, capsular polysaccharide, Klebsiella pneumoniae

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

*O[C@H]1[C@@H](O)[C@@H](CO)O[C@H](O[C@@H]2[C@@H](O)[C@H](*)O[C@H](CO)[C@@H]2O)[C@@H]1O

324.282 g/mol (C₁₂H₂₀R₂O₁₀, R = next and previous repeats, not counted in mol weight)

Klebsiella pneumoniae presents as two circulating pathotypes: classical K. pneumoniae (cKp) and hypervirulent K. pneumoniae (hvKp). Classical isolates are considered urgent threats due to their antibiotic resistance profiles, while hvKp isolates have historically been antibiotic susceptible. Recently, however, increased rates of antibiotic resistance have been observed in both hvKp and cKp, further underscoring the need for preventive and effective immunotherapies. Two distinct surface polysaccharides have gained traction as vaccine candidates against K. pneumoniae: capsular polysaccharide and the O-antigen of lipopolysaccharide. While both targets have practical advantages and disadvantages, it remains unclear which of these antigens included in a vaccine would provide superior protection against matched K. pneumoniae strains. Here, we report the production of two bioconjugate vaccines, one targeting the K2 capsular serotype and the other targeting the O1 O-antigen. Using murine models, we investigated whether these vaccines induced specific antibody responses that recognize K2:O1 K. pneumoniae strains. While each vaccine was immunogenic in mice, both cKp and hvKp strains exhibited decreased O-antibody binding in the presence of capsule. Further, O1 antibodies demonstrated decreased killing in serum bactericidal assays with encapsulated strains, suggesting that the presence of K. pneumoniae capsule blocks O1-antibody binding and function. Finally, the K2 vaccine outperformed the O1 vaccine against both cKp and hvKp in two different murine infection models. These data suggest that capsule-based vaccines may be superior to O-antigen vaccines for targeting hvKp and some cKp strains, due to capsule blocking the O-antigen.

O-antigen, capsular polysaccharide, Klebsiella pneumoniae

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

Warning = sub-repeat ending at aDGalp: unknown unit count was assumed to be 3
Warning = sub-repeat ending at aDGalp: unknown unit count was assumed to be 3
OC[C@@H](O)[C@@H]1O[C@@H](O[C@H]2[C@@H](O)[C@@H](CO)O[C@H](O)[C@@H]2O)[C@H](O)[C@H]1O[C@H]1O[C@H](CO)[C@H](O)[C@H](O[C@@H]2O[C@@H]([C@H](O)CO)[C@H](O[C@H]3O[C@H](CO)[C@H](O)[C@H](O[C@@H]4O[C@@H]([C@H](O)CO)[C@H](O[C@H]5O[C@H](CO)[C@H](O)[C@H](O[C@@H]6O[C@@H]([C@H](O)CO)[C@H](O[C@H]7O[C@H](CO)[C@H](O)[C@H](O[C@@H]8O[C@H](CO)[C@H](O)[C@H](O[C@H]9O[C@H](CO)[C@H](O)[C@H](O[C@@H]%10O[C@H](CO)[C@H](O)[C@H](O[C@H]%11O[C@H](CO)[C@H](O)[C@H](O[C@@H]%12O[C@H](CO)[C@H](O)[C@H](O)[C@H]%12O)[C@H]%11O)[C@H]%10O)[C@H]9O)[C@H]8O)[C@H]7O)[C@H]6O)[C@H]5O)[C@H]4O)[C@H]3O)[C@H]2O)[C@H]1O

2287.989 g/mol (C₈₄H₁₄₂O₇₁)

Klebsiella pneumoniae presents as two circulating pathotypes: classical K. pneumoniae (cKp) and hypervirulent K. pneumoniae (hvKp). Classical isolates are considered urgent threats due to their antibiotic resistance profiles, while hvKp isolates have historically been antibiotic susceptible. Recently, however, increased rates of antibiotic resistance have been observed in both hvKp and cKp, further underscoring the need for preventive and effective immunotherapies. Two distinct surface polysaccharides have gained traction as vaccine candidates against K. pneumoniae: capsular polysaccharide and the O-antigen of lipopolysaccharide. While both targets have practical advantages and disadvantages, it remains unclear which of these antigens included in a vaccine would provide superior protection against matched K. pneumoniae strains. Here, we report the production of two bioconjugate vaccines, one targeting the K2 capsular serotype and the other targeting the O1 O-antigen. Using murine models, we investigated whether these vaccines induced specific antibody responses that recognize K2:O1 K. pneumoniae strains. While each vaccine was immunogenic in mice, both cKp and hvKp strains exhibited decreased O-antibody binding in the presence of capsule. Further, O1 antibodies demonstrated decreased killing in serum bactericidal assays with encapsulated strains, suggesting that the presence of K. pneumoniae capsule blocks O1-antibody binding and function. Finally, the K2 vaccine outperformed the O1 vaccine against both cKp and hvKp in two different murine infection models. These data suggest that capsule-based vaccines may be superior to O-antigen vaccines for targeting hvKp and some cKp strains, due to capsule blocking the O-antigen.

O-antigen, capsular polysaccharide, Klebsiella pneumoniae

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
4,4	bDGlcp	103.6	73.5	83.8	71.6	77.5	62.2
4,3	aDGlcpA	102.7	72.8	74.6	72.6	72.9	?
4	bDManp	101.0	72.1	82.4	73.4	76.7	61.2
	aDGlcp	100.3	72.6	72.8	79.9	71.6	61.1


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
4,4	bDGlcp	4.54	3.38	3.65	3.54	3.54	3.74-3.98
4,3	aDGlcpA	5.22	3.57	3.82	3.62	4.34	-
4	bDManp	4.78	4.22	3.88	4.08	3.59	3.85-4.02
	aDGlcp	5.30	3.60	3.90	3.70	4.07	3.76-3.80


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
4,4	bDGlcp	103.6/4.54	73.5/3.38	83.8/3.65	71.6/3.54	77.5/3.54	62.2/3.74-3.98
4,3	aDGlcpA	102.7/5.22	72.8/3.57	74.6/3.82	72.6/3.62	72.9/4.34	
4	bDManp	101.0/4.78	72.1/4.22	82.4/3.88	73.4/4.08	76.7/3.59	61.2/3.85-4.02
	aDGlcp	100.3/5.30	72.6/3.60	72.8/3.90	79.9/3.70	71.6/4.07	61.1/3.76-3.80

The spectrum also has 1 signal at unknown position (not plotted).

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

*O[C@H]1[C@H](O)[C@@H](CO)O[C@@H](O[C@@H]2[C@@H](CO)O[C@@H](O[C@@H]3[C@@H](CO)O[C@H](*)[C@H](O)[C@H]3O)[C@@H](O)[C@H]2O[C@H]2O[C@H](C(=O)O)[C@@H](O)[C@H](O)[C@H]2O)[C@@H]1O

662.547 g/mol (C₂₄H₃₈R₂O₂₁, R = next and previous repeats, not counted in mol weight)