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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 afforded by UV-inactivated parental or chimeric viruses.Groups of mice previously vaccinated with 5μg prime and boost of each UV-inactivated parental (CHIKV or SFV) or chimeric (ΔDomA, ΔDomB or ΔDomC, ΔDomA+B) virus were challenged with 105 PFU of either wild-type CHIKV or SFV. Five days post-infection, 3 mice from each group were euthanized and brains and footpads were harvested for SFV and CHIKV challenge groups, respectively. Tissues were processed for hematoxylin and eosin (H&E) staining. A-G. Hippocampal neurons from SFV challenged mice using a 25x objective. (A) Uninfected control, (B) CHIKV, (C) SFV, (D) ΔDomA, (E) ΔDomB, (F) ΔDomC, (G) ΔDomA+B. Scale bars represent 50 μM. Black arrows signify neuron degeneration. H-N. Decalcified footpads of CHIKV challenged mice using a 10x objective. (H) Uninfected control, (I) CHIKV, (J) SFV, (K) ΔDomA, (L) ΔDomB, (M) ΔDomC, (N) ΔDomA+B. Scale bars represent 100 μM. White arrows represent areas of mononuclear cell infiltration into the tissue.
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pntd.0004163.g005: Protection afforded by UV-inactivated parental or chimeric viruses.Groups of mice previously vaccinated with 5μg prime and boost of each UV-inactivated parental (CHIKV or SFV) or chimeric (ΔDomA, ΔDomB or ΔDomC, ΔDomA+B) virus were challenged with 105 PFU of either wild-type CHIKV or SFV. Five days post-infection, 3 mice from each group were euthanized and brains and footpads were harvested for SFV and CHIKV challenge groups, respectively. Tissues were processed for hematoxylin and eosin (H&E) staining. A-G. Hippocampal neurons from SFV challenged mice using a 25x objective. (A) Uninfected control, (B) CHIKV, (C) SFV, (D) ΔDomA, (E) ΔDomB, (F) ΔDomC, (G) ΔDomA+B. Scale bars represent 50 μM. Black arrows signify neuron degeneration. H-N. Decalcified footpads of CHIKV challenged mice using a 10x objective. (H) Uninfected control, (I) CHIKV, (J) SFV, (K) ΔDomA, (L) ΔDomB, (M) ΔDomC, (N) ΔDomA+B. Scale bars represent 100 μM. White arrows represent areas of mononuclear cell infiltration into the tissue.

Mentions: Five days after challenge, three mice from each group were sacrificed to monitor histopathological changes in the brain and footpad for SFV and CHIKV-challenged groups, respectively. Mice administered diluent only maintained intact hippocampal neurons, as expected (Fig 5a). In contrast, mice vaccinated with inactivated CHIKV displayed moderate to severe neuron degeneration in the hippocampus following SFV challenge (Fig 5b). SFV-vaccinated mice consistently showed little neuron degeneration in the same region (Fig 5c). In addition, groups vaccinated with ΔDomA, ΔDomC or ΔDomA+B viruses exhibited moderate-to-severe neuron degeneration, similar to CHIKV-vaccinated mice (Fig 5d–5g). Mice immunized with ΔDomB, however, demonstrated mild hippocampal neuron degeneration following SFV challenge, consistent with SFV-vaccinated mice (Fig 5e).


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 afforded by UV-inactivated parental or chimeric viruses.Groups of mice previously vaccinated with 5μg prime and boost of each UV-inactivated parental (CHIKV or SFV) or chimeric (ΔDomA, ΔDomB or ΔDomC, ΔDomA+B) virus were challenged with 105 PFU of either wild-type CHIKV or SFV. Five days post-infection, 3 mice from each group were euthanized and brains and footpads were harvested for SFV and CHIKV challenge groups, respectively. Tissues were processed for hematoxylin and eosin (H&E) staining. A-G. Hippocampal neurons from SFV challenged mice using a 25x objective. (A) Uninfected control, (B) CHIKV, (C) SFV, (D) ΔDomA, (E) ΔDomB, (F) ΔDomC, (G) ΔDomA+B. Scale bars represent 50 μM. Black arrows signify neuron degeneration. H-N. Decalcified footpads of CHIKV challenged mice using a 10x objective. (H) Uninfected control, (I) CHIKV, (J) SFV, (K) ΔDomA, (L) ΔDomB, (M) ΔDomC, (N) ΔDomA+B. Scale bars represent 100 μM. White arrows represent areas of mononuclear cell infiltration into the tissue.
© Copyright Policy
Related In: Results  -  Collection

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

pntd.0004163.g005: Protection afforded by UV-inactivated parental or chimeric viruses.Groups of mice previously vaccinated with 5μg prime and boost of each UV-inactivated parental (CHIKV or SFV) or chimeric (ΔDomA, ΔDomB or ΔDomC, ΔDomA+B) virus were challenged with 105 PFU of either wild-type CHIKV or SFV. Five days post-infection, 3 mice from each group were euthanized and brains and footpads were harvested for SFV and CHIKV challenge groups, respectively. Tissues were processed for hematoxylin and eosin (H&E) staining. A-G. Hippocampal neurons from SFV challenged mice using a 25x objective. (A) Uninfected control, (B) CHIKV, (C) SFV, (D) ΔDomA, (E) ΔDomB, (F) ΔDomC, (G) ΔDomA+B. Scale bars represent 50 μM. Black arrows signify neuron degeneration. H-N. Decalcified footpads of CHIKV challenged mice using a 10x objective. (H) Uninfected control, (I) CHIKV, (J) SFV, (K) ΔDomA, (L) ΔDomB, (M) ΔDomC, (N) ΔDomA+B. Scale bars represent 100 μM. White arrows represent areas of mononuclear cell infiltration into the tissue.
Mentions: Five days after challenge, three mice from each group were sacrificed to monitor histopathological changes in the brain and footpad for SFV and CHIKV-challenged groups, respectively. Mice administered diluent only maintained intact hippocampal neurons, as expected (Fig 5a). In contrast, mice vaccinated with inactivated CHIKV displayed moderate to severe neuron degeneration in the hippocampus following SFV challenge (Fig 5b). SFV-vaccinated mice consistently showed little neuron degeneration in the same region (Fig 5c). In addition, groups vaccinated with ΔDomA, ΔDomC or ΔDomA+B viruses exhibited moderate-to-severe neuron degeneration, similar to CHIKV-vaccinated mice (Fig 5d–5g). Mice immunized with ΔDomB, however, demonstrated mild hippocampal neuron degeneration following SFV challenge, consistent with SFV-vaccinated mice (Fig 5e).

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