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Identifying the Role of E2 Domains on Alphavirus Neutralization and Protective Immune Responses.

Weger-Lucarelli J, Aliota MT, Kamlangdee A, Osorio JE - PLoS Negl Trop Dis (2015)

Bottom Line: The alphavirus E2, the receptor-binding envelope protein, is considered to be the predominant target of the protective host immune response.Using chimeric viruses, it was determined that the alphavirus E2 domain B was the critical target of neutralizing antibodies in both mice and humans.Therefore, chimeric viruses may have more relevance for vaccine discovery than peptide-based approaches, which only detect linear epitopes.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathobiological Sciences, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.

ABSTRACT

Background: Chikungunya virus (CHIKV) and other alphaviruses are the etiologic agents of numerous diseases in both humans and animals. Despite this, the viral mediators of protective immunity against alphaviruses are poorly understood, highlighted by the lack of a licensed human vaccine for any member of this virus genus. The alphavirus E2, the receptor-binding envelope protein, is considered to be the predominant target of the protective host immune response. Although envelope protein domains have been studied for vaccine and neutralization in flaviviruses, their role in alphaviruses is less characterized. Here, we describe the role of the alphavirus E2 domains in neutralization and protection through the use of chimeric viruses.

Methodology/principal findings: Four chimeric viruses were constructed in which individual E2 domains of CHIKV were replaced with the corresponding domain from Semliki Forest virus (SFV) (ΔDomA/ΔDomB/ΔDomC/ ΔDomA+B). Vaccination studies in mice (both live and inactivated virus) revealed that domain B was the primary determinant of neutralization. Neutralization studies with CHIKV immune serum from humans were consistent with mouse studies, as ΔDomB was poorly neutralized.

Conclusions/significance: Using chimeric viruses, it was determined that the alphavirus E2 domain B was the critical target of neutralizing antibodies in both mice and humans. Therefore, chimeric viruses may have more relevance for vaccine discovery than peptide-based approaches, which only detect linear epitopes. This study provides new insight into the role of alphavirus E2 domains on neutralization determinants and may be useful for the design of novel therapeutic technologies.

No MeSH data available.


Related in: MedlinePlus

Protection and neutralizing antibody response elicited by chimeric CHIKV/SFV.Adult C57bl/6 mice (n = 6) were infected with 105 PFU of CHIK, SFV, or chimeric viruses (ΔDomA, ΔDomB or ΔDomC) in the left hind footpad. Two months later, mice were bled for neutralizing antibodies and challenged with 105 PFU SFV. A) Levels of neutralizing antibodies against SFV were measured by incubating serum from vaccinated mice with a SFV construct expressing nano-luciferase overnight at 4°C. The next day, the virus:serum mixture was used to infect BHK-21 cells in 96 well plates. After one hour adsorption period, cells were washed and fresh media was added. After five hours infection, cells were lysed and luciferase signal measured. Relative luminescence was normalized to a mock vaccinated control serum. SFV is not included as all infected mice rapidly succumbed to infection. B) Challenged mice were monitored for 15 days following infection. Data are expressed as percent survival.
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pntd.0004163.g002: Protection and neutralizing antibody response elicited by chimeric CHIKV/SFV.Adult C57bl/6 mice (n = 6) were infected with 105 PFU of CHIK, SFV, or chimeric viruses (ΔDomA, ΔDomB or ΔDomC) in the left hind footpad. Two months later, mice were bled for neutralizing antibodies and challenged with 105 PFU SFV. A) Levels of neutralizing antibodies against SFV were measured by incubating serum from vaccinated mice with a SFV construct expressing nano-luciferase overnight at 4°C. The next day, the virus:serum mixture was used to infect BHK-21 cells in 96 well plates. After one hour adsorption period, cells were washed and fresh media was added. After five hours infection, cells were lysed and luciferase signal measured. Relative luminescence was normalized to a mock vaccinated control serum. SFV is not included as all infected mice rapidly succumbed to infection. B) Challenged mice were monitored for 15 days following infection. Data are expressed as percent survival.

Mentions: C57bl/6 mice were selected for initial characterization of immune responses generated against CHIKV/SFV chimeras because they serve as an immunocompetent arthritis model for CHIKV [34] and a lethal encephalitis model for SFV [35]. Groups of mice (n = 6) were administered either viral diluent (mock infected) or 105 PFU of each virus (except ΔDomA+B) in the hind left footpad (hereafter designated as vaccinated). Mice administered SFV succumbed rapidly, while all other groups remained healthy besides footpad swelling (Weger-Lucarelli et al. in revision). Serum samples from mice that were vaccinated with the chimeric viruses were assessed for neutralization against SFV using a luciferase-based assay [31], and there were no significant differences observed between mean neutralization titers against SFV when comparing ΔDomA or ΔDomB to CHIKV infected mice (One-way ANOVA with Tukey’s correction) (p = .13 and .15, for ΔDomA and ΔDomB respectively)) (Fig 2a). Serum from mice infected with ΔDomC had significantly reduced mean neutralization capacity as compared to either ΔDomA or ΔDomB (p<0.01 for both groups). However, serum from mice that were infected with chimeric viruses ΔDomA and ΔDomB did have a highly significant difference in variances (F test p<0.001) in neutralizing titers against SFV, indicating that both domains A and B are important for developing consistent neutralizing antibody responses.


Identifying the Role of E2 Domains on Alphavirus Neutralization and Protective Immune Responses.

Weger-Lucarelli J, Aliota MT, Kamlangdee A, Osorio JE - PLoS Negl Trop Dis (2015)

Protection and neutralizing antibody response elicited by chimeric CHIKV/SFV.Adult C57bl/6 mice (n = 6) were infected with 105 PFU of CHIK, SFV, or chimeric viruses (ΔDomA, ΔDomB or ΔDomC) in the left hind footpad. Two months later, mice were bled for neutralizing antibodies and challenged with 105 PFU SFV. A) Levels of neutralizing antibodies against SFV were measured by incubating serum from vaccinated mice with a SFV construct expressing nano-luciferase overnight at 4°C. The next day, the virus:serum mixture was used to infect BHK-21 cells in 96 well plates. After one hour adsorption period, cells were washed and fresh media was added. After five hours infection, cells were lysed and luciferase signal measured. Relative luminescence was normalized to a mock vaccinated control serum. SFV is not included as all infected mice rapidly succumbed to infection. B) Challenged mice were monitored for 15 days following infection. Data are expressed as percent survival.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4608762&req=5

pntd.0004163.g002: Protection and neutralizing antibody response elicited by chimeric CHIKV/SFV.Adult C57bl/6 mice (n = 6) were infected with 105 PFU of CHIK, SFV, or chimeric viruses (ΔDomA, ΔDomB or ΔDomC) in the left hind footpad. Two months later, mice were bled for neutralizing antibodies and challenged with 105 PFU SFV. A) Levels of neutralizing antibodies against SFV were measured by incubating serum from vaccinated mice with a SFV construct expressing nano-luciferase overnight at 4°C. The next day, the virus:serum mixture was used to infect BHK-21 cells in 96 well plates. After one hour adsorption period, cells were washed and fresh media was added. After five hours infection, cells were lysed and luciferase signal measured. Relative luminescence was normalized to a mock vaccinated control serum. SFV is not included as all infected mice rapidly succumbed to infection. B) Challenged mice were monitored for 15 days following infection. Data are expressed as percent survival.
Mentions: C57bl/6 mice were selected for initial characterization of immune responses generated against CHIKV/SFV chimeras because they serve as an immunocompetent arthritis model for CHIKV [34] and a lethal encephalitis model for SFV [35]. Groups of mice (n = 6) were administered either viral diluent (mock infected) or 105 PFU of each virus (except ΔDomA+B) in the hind left footpad (hereafter designated as vaccinated). Mice administered SFV succumbed rapidly, while all other groups remained healthy besides footpad swelling (Weger-Lucarelli et al. in revision). Serum samples from mice that were vaccinated with the chimeric viruses were assessed for neutralization against SFV using a luciferase-based assay [31], and there were no significant differences observed between mean neutralization titers against SFV when comparing ΔDomA or ΔDomB to CHIKV infected mice (One-way ANOVA with Tukey’s correction) (p = .13 and .15, for ΔDomA and ΔDomB respectively)) (Fig 2a). Serum from mice infected with ΔDomC had significantly reduced mean neutralization capacity as compared to either ΔDomA or ΔDomB (p<0.01 for both groups). However, serum from mice that were infected with chimeric viruses ΔDomA and ΔDomB did have a highly significant difference in variances (F test p<0.001) in neutralizing titers against SFV, indicating that both domains A and B are important for developing consistent neutralizing antibody responses.

Bottom Line: The alphavirus E2, the receptor-binding envelope protein, is considered to be the predominant target of the protective host immune response.Using chimeric viruses, it was determined that the alphavirus E2 domain B was the critical target of neutralizing antibodies in both mice and humans.Therefore, chimeric viruses may have more relevance for vaccine discovery than peptide-based approaches, which only detect linear epitopes.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathobiological Sciences, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.

ABSTRACT

Background: Chikungunya virus (CHIKV) and other alphaviruses are the etiologic agents of numerous diseases in both humans and animals. Despite this, the viral mediators of protective immunity against alphaviruses are poorly understood, highlighted by the lack of a licensed human vaccine for any member of this virus genus. The alphavirus E2, the receptor-binding envelope protein, is considered to be the predominant target of the protective host immune response. Although envelope protein domains have been studied for vaccine and neutralization in flaviviruses, their role in alphaviruses is less characterized. Here, we describe the role of the alphavirus E2 domains in neutralization and protection through the use of chimeric viruses.

Methodology/principal findings: Four chimeric viruses were constructed in which individual E2 domains of CHIKV were replaced with the corresponding domain from Semliki Forest virus (SFV) (ΔDomA/ΔDomB/ΔDomC/ ΔDomA+B). Vaccination studies in mice (both live and inactivated virus) revealed that domain B was the primary determinant of neutralization. Neutralization studies with CHIKV immune serum from humans were consistent with mouse studies, as ΔDomB was poorly neutralized.

Conclusions/significance: Using chimeric viruses, it was determined that the alphavirus E2 domain B was the critical target of neutralizing antibodies in both mice and humans. Therefore, chimeric viruses may have more relevance for vaccine discovery than peptide-based approaches, which only detect linear epitopes. This study provides new insight into the role of alphavirus E2 domains on neutralization determinants and may be useful for the design of novel therapeutic technologies.

No MeSH data available.


Related in: MedlinePlus