Differential reactivity of TCR Vbeta10 alleles to a mouse mammary tumor virus superantigen

Role of TRPV3 in immune response to development of dermatitis

Background

Recently, it has been reported that the Gly573Ser substitution of transient receptor potential V3 (TRPV3) leads to increased ion-channel activity in keratinocytes. Our previous studies have indicated that the spontaneous hairless and dermatitis phenotypes of DS-Nh mice, which were newly established as an animal model of atopic dermatitis (AD), are caused by TRPV3^Gly573Ser. Although this substitution causes hairlessness in several kinds of rodents, in our investigations, dermatitis developed in only a few animals. Here, we generated NC/Nga-Nh mice to elucidate the role of TRPV3^Gly573Ser in NC/Nga mice, which is one of the most studied animal models of AD.

Methods

To establish and validate the new AD animal model, NC/Nga-Nh mice were generated using NC/Nga and DS-Nh mice, and their clinical features were compared. Next, T-cell receptor (TCR) Vβ usage in splenocytes, evaluation of bacterial colonization, and serological and histological analyses were carried out. Finally, repeated-hapten-application dermatitis was induced in these mice.

Results

NC/Nga-Nh mice did not develop spontaneous dermatitis, whereas DS-Nh mice displayed this phenotype when maintained under the same conditions. Serological analysis indicated that there really was a phenotypic difference between these mice, and TCR repertoire analysis indicated that TCRVβ haplotypes played an important role in the development of dermatitis. Artificial dermatitis developed in DS and NC/Nga-Nh mice, but not in DS-Nh and NC/Nga mice. Histological and serological analyses indicated that mouse strains were listed in descending order of number of skin mast cells: DS-Nh > DS ≈ NC/Nga-Nh > NC/Nga, and serum IgE levels were increased after 2,4,6 trinitrochlorobenzene application in these mice. Serum IgE level in DS-Nh mice was lower than that mesured in other strains.

Conclusion

Our results confirm the contribution of the TRPV3^Gly573Ser gene to the development of repeated hapten dermatitis, but not spontaneous dermatitis in NC/Nga mice.

Identification of key amino acids of the mouse mammary tumor virus superantigen involved in the specific interaction with T-cell receptor V(beta) domains

Mouse mammary tumor virus (MMTV) is a retrovirus encoding a superantigen that is recognized in association with major histocompatibility complex class II by the variable region of the beta chain (V(beta)) of the T-cell receptor. The C-terminal 30 to 40 amino acids of the superantigen of different MMTVs display high sequence variability that correlates with the recognition of particular T-cell receptor V(beta) chains. Interestingly, MMTV(SIM) and mtv-8 superantigens are highly homologous but have nonoverlapping T-cell receptor V(beta) specificities. To determine the importance of these few differences for specific V(beta) interaction, we studied superantigen responses in mice to chimeric and mutant MMTV(SIM) and mtv-8 superantigens expressed by recombinant vaccinia viruses. We show that only a few changes (two to six residues) within the C terminus are necessary to modify superantigen recognition by specific V(beta)s. Thus, the introduction of the MMTV(SIM) residues 314-315 into the mtv-8 superantigen greatly decreased its V(beta)12 reactivity without gain of MMTV(SIM)-specific function. The introduction of MMTV(SIM)-specific residues 289 to 295, however, induced a recognition pattern that was a mixture of MMTV(SIM)- and mtv-8-specific V(beta) reactivities: both weak MMTV(SIM)-specific V(beta)4 and full mtv-8-specific V(beta)11 recognition were observed while V(beta)12 interaction was lost. The combination of the two MMTV(SIM)-specific regions in the mtv-8 superantigen established normal MMTV(SIM)-specific V(beta)4 reactivity and completely abolished mtv-8-specific V(beta)5, -11, and -12 interactions. These new functional superantigens with mixed V(beta) recognition patterns allowed us to precisely delineate sites relevant for molecular interactions between the SIM or mtv-8 superantigen and the T-cell receptor V(beta) domain within the 30 C-terminal residues of the viral superantigen.