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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

Neutralization and protection following vaccination with UV-inactivated viruses.Six-week old C57bl/6 mice were vaccinated with 5μg of each parental (CHIK or SFV) or chimeric viruses (ΔDomA, ΔDomB, ΔDomC, ΔDomA+B) inactivated with ultraviolet (UV) radiation. Mice received a second injection 28 days later. Groups of mice were then challenged with 105 PFU of either CHIKV or SFV. A) Neutralizing antibody responses against both CHIK and SFV were assessed prior to challenge using a luciferase based assay. Infectious virus was mixed with a 1:20 dilution of serum and used to infect cells following incubation overnight at 4°C. Luciferase activity was measured in cell lysates after five hours of infection. Data are expressed as fold neutralization, normalized to mock serum. Mice challenged with SFV were monitored for B) weight loss and C) survival. Weight loss is expressed as the mean percentage of starting weight of the group. D) Change in footpad width was used as a marker of CHIKV disease. Data are presented as percent change as compared to pre-challenge levels.
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pntd.0004163.g004: Neutralization and protection following vaccination with UV-inactivated viruses.Six-week old C57bl/6 mice were vaccinated with 5μg of each parental (CHIK or SFV) or chimeric viruses (ΔDomA, ΔDomB, ΔDomC, ΔDomA+B) inactivated with ultraviolet (UV) radiation. Mice received a second injection 28 days later. Groups of mice were then challenged with 105 PFU of either CHIKV or SFV. A) Neutralizing antibody responses against both CHIK and SFV were assessed prior to challenge using a luciferase based assay. Infectious virus was mixed with a 1:20 dilution of serum and used to infect cells following incubation overnight at 4°C. Luciferase activity was measured in cell lysates after five hours of infection. Data are expressed as fold neutralization, normalized to mock serum. Mice challenged with SFV were monitored for B) weight loss and C) survival. Weight loss is expressed as the mean percentage of starting weight of the group. D) Change in footpad width was used as a marker of CHIKV disease. Data are presented as percent change as compared to pre-challenge levels.

Mentions: In order to reduce the likelihood of other viral proteins and cell-mediated immunity confounding protection, we next vaccinated C57bl/6 mice with UV-inactivated virus. Groups of mice (n = 6) were immunized with 5 μg of inactivated virus in the left hind footpad followed by a second immunization 28 days later (boost). To determine the cross neutralization potential of mice vaccinated with inactivated viruses, mice were bled four weeks post-boost to measure levels of neutralizing antibodies against both CHIKV and SFV. Mice vaccinated with inactivated CHIKV or SFV displayed neutralization against homologous virus but very little cross-neutralization was observed (Fig 4a). Mice vaccinated with ΔDomA chimeric virus neutralized CHIKV but poorly neutralized SFV (p<0.01). In contrast, the ΔDomB virus showed a reverse pattern, losing much of its neutralization capacity to CHIKV while gaining significant neutralization to SFV (p<0.05). Neutralization was significantly reduced in mice vaccinated with either ΔDomC or ΔDomA+B viruses against CHIKV (p<0.05 and p<0.01) and neither virus produced detectable neutralizing antibodies to SFV.


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)

Neutralization and protection following vaccination with UV-inactivated viruses.Six-week old C57bl/6 mice were vaccinated with 5μg of each parental (CHIK or SFV) or chimeric viruses (ΔDomA, ΔDomB, ΔDomC, ΔDomA+B) inactivated with ultraviolet (UV) radiation. Mice received a second injection 28 days later. Groups of mice were then challenged with 105 PFU of either CHIKV or SFV. A) Neutralizing antibody responses against both CHIK and SFV were assessed prior to challenge using a luciferase based assay. Infectious virus was mixed with a 1:20 dilution of serum and used to infect cells following incubation overnight at 4°C. Luciferase activity was measured in cell lysates after five hours of infection. Data are expressed as fold neutralization, normalized to mock serum. Mice challenged with SFV were monitored for B) weight loss and C) survival. Weight loss is expressed as the mean percentage of starting weight of the group. D) Change in footpad width was used as a marker of CHIKV disease. Data are presented as percent change as compared to pre-challenge levels.
© Copyright Policy
Related In: Results  -  Collection

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

pntd.0004163.g004: Neutralization and protection following vaccination with UV-inactivated viruses.Six-week old C57bl/6 mice were vaccinated with 5μg of each parental (CHIK or SFV) or chimeric viruses (ΔDomA, ΔDomB, ΔDomC, ΔDomA+B) inactivated with ultraviolet (UV) radiation. Mice received a second injection 28 days later. Groups of mice were then challenged with 105 PFU of either CHIKV or SFV. A) Neutralizing antibody responses against both CHIK and SFV were assessed prior to challenge using a luciferase based assay. Infectious virus was mixed with a 1:20 dilution of serum and used to infect cells following incubation overnight at 4°C. Luciferase activity was measured in cell lysates after five hours of infection. Data are expressed as fold neutralization, normalized to mock serum. Mice challenged with SFV were monitored for B) weight loss and C) survival. Weight loss is expressed as the mean percentage of starting weight of the group. D) Change in footpad width was used as a marker of CHIKV disease. Data are presented as percent change as compared to pre-challenge levels.
Mentions: In order to reduce the likelihood of other viral proteins and cell-mediated immunity confounding protection, we next vaccinated C57bl/6 mice with UV-inactivated virus. Groups of mice (n = 6) were immunized with 5 μg of inactivated virus in the left hind footpad followed by a second immunization 28 days later (boost). To determine the cross neutralization potential of mice vaccinated with inactivated viruses, mice were bled four weeks post-boost to measure levels of neutralizing antibodies against both CHIKV and SFV. Mice vaccinated with inactivated CHIKV or SFV displayed neutralization against homologous virus but very little cross-neutralization was observed (Fig 4a). Mice vaccinated with ΔDomA chimeric virus neutralized CHIKV but poorly neutralized SFV (p<0.01). In contrast, the ΔDomB virus showed a reverse pattern, losing much of its neutralization capacity to CHIKV while gaining significant neutralization to SFV (p<0.05). Neutralization was significantly reduced in mice vaccinated with either ΔDomC or ΔDomA+B viruses against CHIKV (p<0.05 and p<0.01) and neither virus produced detectable neutralizing antibodies to SFV.

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