TY - JOUR
T1 - Correctly folded - but not necessarily functional - influenza virus neuraminidase is required to induce protective antibody responses in mice
AU - McMahon, Meagan
AU - Strohmeier, Shirin
AU - Rajendran, Madhusudan
AU - Capuano, Christina
AU - Ellebedy, Ali H.
AU - Wilson, Patrick C.
AU - Krammer, Florian
N1 - Funding Information:
This work was supported in part by the National Institute of Allergy and Infectious Disease (NIAID) Collaborative Influenza Vaccine Innovation Centers (CIVIC) contract 75N93019C00051 , NIAID Centers of Excellence for Influenza Research and Surveillance (CEIRS) contract ( HHSN272201400008C ) and NIAID grant AI117287 .
Publisher Copyright:
© 2020 Elsevier Ltd
PY - 2020/10/21
Y1 - 2020/10/21
N2 - The influenza virus neuraminidase (NA) plays an integral role in the influenza virus life cycle through the release of virions from infected cells. NA-specific antibodies can impede virus replication by binding to the NA and blocking its enzymatic activity, providing significant protection from influenza-associated morbidity and mortality. NA included in current seasonal influenza virus vaccines exhibits low immunogenicity, potentially caused by compromised antigenic integrity during vaccine production. To determine how certain types of “stress” could influence the antigenicity of NA we performed a series of in vitro experiments where we treated NA with formalin, EDTA or heat and measured the impact of these treatments on NA enzymatic activity and structural integrity. We found that increasing concentrations of formalin or EDTA and increasing temperature abolished the enzymatic activity of both H1N1, H3N2, and influenza B purified viruses and recombinant NA proteins. However, formalin and EDTA treatment did not drastically affect conformational epitopes found on the NA, whereas heat treatment abolished conformational epitopes. We next performed a vaccination experiment, where mice were vaccinated with recombinant N2 NA treated with 0.3% formalin or 0.125 M EDTA (which both inactivated NA activity) were protected from virus challenge while animals vaccinated with heat treated NA were not. We next tested the protective effect of monomeric (no enzymatic activity) versus tetrameric (highly active) N1 NA. Again, only the tetrameric form protected mice from challenge while the monomeric form did not. Together, our data demonstrate that enzymatically active NA is not required to induce protective antibody responses as a vaccine, however a correctly folded NA is essential.
AB - The influenza virus neuraminidase (NA) plays an integral role in the influenza virus life cycle through the release of virions from infected cells. NA-specific antibodies can impede virus replication by binding to the NA and blocking its enzymatic activity, providing significant protection from influenza-associated morbidity and mortality. NA included in current seasonal influenza virus vaccines exhibits low immunogenicity, potentially caused by compromised antigenic integrity during vaccine production. To determine how certain types of “stress” could influence the antigenicity of NA we performed a series of in vitro experiments where we treated NA with formalin, EDTA or heat and measured the impact of these treatments on NA enzymatic activity and structural integrity. We found that increasing concentrations of formalin or EDTA and increasing temperature abolished the enzymatic activity of both H1N1, H3N2, and influenza B purified viruses and recombinant NA proteins. However, formalin and EDTA treatment did not drastically affect conformational epitopes found on the NA, whereas heat treatment abolished conformational epitopes. We next performed a vaccination experiment, where mice were vaccinated with recombinant N2 NA treated with 0.3% formalin or 0.125 M EDTA (which both inactivated NA activity) were protected from virus challenge while animals vaccinated with heat treated NA were not. We next tested the protective effect of monomeric (no enzymatic activity) versus tetrameric (highly active) N1 NA. Again, only the tetrameric form protected mice from challenge while the monomeric form did not. Together, our data demonstrate that enzymatically active NA is not required to induce protective antibody responses as a vaccine, however a correctly folded NA is essential.
KW - Activity
KW - Immunogenicity
KW - Influenza
KW - Neuraminidase
UR - http://www.scopus.com/inward/record.url?scp=85090984994&partnerID=8YFLogxK
U2 - 10.1016/j.vaccine.2020.08.067
DO - 10.1016/j.vaccine.2020.08.067
M3 - Article
C2 - 32943267
AN - SCOPUS:85090984994
SN - 0264-410X
VL - 38
SP - 7129
EP - 7137
JO - Vaccine
JF - Vaccine
IS - 45
ER -