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The Human CD4+ T Cell Response against Mumps Virus Targets a Broadly Recognized Nucleoprotein Epitope.

ABSTRACT: Mumps outbreaks among vaccinated young adults stress the need for a better understanding of mumps virus (MuV)-induced immunity. Antibody responses to MuV are well characterized, but studies on T cell responses are limited. We recently isolated a MuV-specific CD4+ T cell clone by stimulating peripheral blood mononuclear cells (PBMCs) from a mumps case with the viral nucleoprotein (MuV-N). In this study, we further explored the identity and relevance of the epitope recognized by the CD4+ T cell clone and ex vivo by T cells in a cohort of mumps cases. Using a two-dimensional matrix peptide pool of 15-mer peptides covering the complete MuV-N, we identified the epitope recognized by the T cell clone as MuV-N110-124 GTYRLIPNARANLTA, present in a well-conserved region of the viral protein. Upon peptide-specific stimulation, the T cell clone expressed the activation marker CD137 and produced gamma interferon, tumor necrosis factor, and interleukin-10 in a HLA-DR4-restricted manner. Moreover, the CD4+ T cells exerted a cytotoxic phenotype and specifically killed cells presenting MuV-N110-124 Furthermore, the identified peptide is widely applicable to the general population since it is predicted to bind various common HLA-DR molecules, and epitope-specific CD4+ T cells displaying cytotoxic/Th1-type properties were found in all tested mumps cases expressing different HLA-DR alleles. This first broadly recognized human MuV-specific CD4+ T cell epitope could provide a useful tool to detect and evaluate virus-specific T cell responses upon MuV infection or following vaccination.IMPORTANCE Recent outbreaks of mumps among vaccinated young adults have been reported worldwide. Humoral responses against mumps virus (MuV) are well characterized, although no correlate of protection has been elucidated, stressing the need to better understand cellular MuV-specific immunity. In this study, we identified the first MuV T cell epitope, which is derived from the viral nucleoprotein (MuV-N) and was recognized by a cytotoxic/Th1 CD4+ T cell clone that was isolated from a mumps case. Moreover, the epitope was predicted to bind a broad variety of common HLA-DRB1 alleles, which was confirmed by the epitope-specific cytotoxic/Th1 CD4+ T cell responses observed in multiple mumps cases with various HLA-DRB1 genotypes. The identified epitope is completely conserved among various mumps strains. These findings qualify this promiscuous MuV T cell epitope as a useful tool for further in-depth exploration of MuV-specific T cell immunity after natural mumps virus infection or induced by vaccination.

SUBMITTER: de Wit J

PROVIDER: S-EPMC6401470 | biostudies-literature | 2019 Mar

REPOSITORIES: biostudies-literature

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The Human CD4<sup>+</sup> T Cell Response against Mumps Virus Targets a Broadly Recognized Nucleoprotein Epitope.

de Wit Jelle J Emmelot Maarten E ME Poelen Martien C M MCM Lanfermeijer Josien J Han Wanda G H WGH van Els Cécile A C M CACM Kaaijk Patricia P

Journal of virology 20190305 6

Mumps outbreaks among vaccinated young adults stress the need for a better understanding of mumps virus (MuV)-induced immunity. Antibody responses to MuV are well characterized, but studies on T cell responses are limited. We recently isolated a MuV-specific CD4<sup>+</sup> T cell clone by stimulating peripheral blood mononuclear cells (PBMCs) from a mumps case with the viral nucleoprotein (MuV-N). In this study, we further explored the identity and relevance of the epitope recognized by the CD4 ...[more]

PMID: 30626672

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Project description:UnlabelledThe HIV-1 surface envelope glycoprotein (Env) trimer mediates entry into CD4(+) CCR5(+) host cells. Env possesses conserved antigenic determinants, such as the gp120 primary receptor CD4 binding site (CD4bs), a known neutralization target. Env also contains variable regions and protein surfaces occluded within the trimer that elicit nonneutralizing antibodies. Here we engineered additional N-linked glycans onto a cysteine-stabilized gp120 core (0G) deleted of its major variable regions to preferentially expose the conformationally fixed CD4bs. Three, 6, 7, and 10 new NXT/S glycan (G) motifs were engineered into 0G to encode 3G, 6G, 7G, and 10G cores. Following purification, most glycoproteins, except for 10G, were recognized by broadly neutralizing CD4bs-directed antibodies. Gel and glycan mass spectrometry confirmed that additional N-glycans were posttranslationally added to the redesigned cores. Binding kinetics revealed high-affinity recognition by seven broadly neutralizing CD4bs-directed antibodies and low to no binding by non-broadly neutralizing CD4bs-directed antibodies. Rabbits inoculated with the hyperglycosylated cores elicited IgM and IgG responses to each given protein that were similar in their neutralization characteristics to those elicited by parental 0G. Site-specific glycan masking effects were detected in the elicited sera, and the antisera competed with b12 for CD4bs-directed binding specificity. However, the core-elicited sera showed limited neutralization activity. Trimer priming or boosting of the core immunogens elicited tier 1-level neutralization that mapped to both the CD4bs and V3 and appeared to be trimer dependent. Fine mapping at the CD4bs indicated that conformational stabilization of the cores and addition of N-glycans altered the molecular surface of Env sites of vulnerability to neutralizing antibody, suggesting an explanation for why the elicited neutralization was not improved by this rational design strategy.ImportanceMajor obstacles to developing an effective HIV-1 vaccine include the variability of the envelope surface glycoproteins and its high-density glycan shield, generated by incorporation of host (human) glycosylation. HIV-1 does harbor highly conserved sites on the exposed envelope protein surface of gp120, one of which is the virus receptor (CD4) binding site. Several broadly neutralizing antibodies elicited from HIV patients do target this gp120 CD4 binding site (CD4bs); however, gp120 immunogens do not elicit broadly neutralizing antibodies. In this study, we targeted the CD4bs by conformational stabilization and additional glycan masking. We used the atomic-level structure to reengineer gp120 cores to preferentially present the cysteine-stabilized CD4bs and to mask (by glycan) nonneutralizing determinants. Importantly, glycan masking did successfully focus antibody responses to the CD4bs; however, the elicited CD4bs-directed antibodies did not neutralize HIV or bind to unmodified gp120, presumably due to the structure-guided modifications of the modified gp120 core.

Dataset Information

The Human CD4+ T Cell Response against Mumps Virus Targets a Broadly Recognized Nucleoprotein Epitope.

Publications

The Human CD4<sup>+</sup> T Cell Response against Mumps Virus Targets a Broadly Recognized Nucleoprotein Epitope.

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