Immunodomination of Serotype-Specific CD4+ T-Cell Epitopes Contributed to the Biased Immune Responses Induced by a Tetravalent Measles-Vectored Dengue Vaccine.

Dengue is an emerging mosquito-borne disease, and the use of prophylactic vaccines is still limited. We previously developed a tetravalent dengue vaccine (rMV-TDV) by a recombinant measles virus (MV) vector expressing envelope protein domain III (ED3). In this study, we used dengue-susceptible AG129 mice to evaluate the protective and/or pathogenic immune responses induced by rMV-TDV. Consistent with the previous study, rMV-TDV-immunized mice developed a significant neutralizing antibody response against all serotypes of DENV, as well as a significant IFN-γ response biased to DENV-3, compared to the vector controls. We further demonstrated that this DENV-3-specific IFN-γ response was dominated by one CD4+ T-cell epitope located in E349-363. After DENV-2 challenge, rMV-TDV-immunized mice showed a significantly lower viremia and no inflammatory cytokine increase compared to the vector controls, which had an ~100 times higher viremia and a significant increase in IFN-γ and TNF-α. As a correlate of protection, a robust memory IFN-γ response specific to DENV-2 was boosted in rMV-TDV-immunized mice after challenge. This result suggested that pre-existing DENV-3-dominated T-cell responses did not cross-react, but a DENV-2-specific IFN-γ response, which was undetectable during immunization, was recalled. Interestingly, this recalled T-cell response recognized the epitope in the same position as the E349-363 but in the DENV-2 serotype. This result suggested that immunodomination occurred in the CD4+ T-cell epitopes between dengue serotypes after rMV-TDV vaccination and resulted in a DENV-3-dominated CD4+ T-cell response. Although the significant increase in IgG against both DENV-2 and -3 suggested that cross-reactive antibody responses were boosted, the increased neutralizing antibodies and IgG avidity still remained DENV-2 specific, consistent with the serotype-specific T cell response post challenge. Our data reveal that immunodomination caused a biased T-cell response to one of the dengue serotypes after tetravalent dengue vaccination and highlight the roles of cross-reactive T cells in dengue protection.

Candida albicans Colonizes and Disseminates to the Gastrointestinal Tract in the Presence of the Microbiota in a Severe Combined Immunodeficient Mouse Model.

Candida albicans is the leading cause of candidemia or other invasive candidiasis. Gastrointestinal colonization has been considered as the primary source of candidemia. However, few established mouse models that mimic this infection route are available. In the present study, we established a mouse model of disseminated candidiasis developed through the translocation of Candida from the gut. In this study, we developed a novel C. albicans GI colonization and dissemination animal model by using severe combined immunodeficient Rag2-/-IL2γc-/- (Rag2γc) mice, which lack functional T, B, NK cells, and IL2γc-dependent signaling. Rag2γc mice were highly susceptible to C. albicans gastrointestinal infection even in the presence of the gut microbiota. Within 4 weeks post infection, Rag2γc mice showed dose-dependent weight loss and disseminated candidiasis in more than 58% (7/12) of moribund mice. Histological analysis demonstrated abundant hyphae penetrating the mucosa, with significant neutrophilic infiltration in mice infected with wild-type C. albicans but not a filamentation-defective mutant. In moribund Rag2γc mice, the necrotic lesions and disrupted epithelial cells were associated with C. albicans hyphae. Notably, removal of the gut microbiota by antibiotics exacerbated the severity of fungal infection in Rag2γc mice, as demonstrated by elevated fungal burdens and accelerated weight loss and death. Furthermore, higher fungal burden and IL-1ß expression were prominently noted in the stomach of Rag2γc mice. In fact, a significant increase in circulating proinflammatory cytokines, including IL-6, TNF-α, and IL-10, indicative of a septic response, was evident in infected Rag2γc mice. Additionally, Rag2γc mice exhibited significantly lower levels of IL-22 but not IFN-γ or IL-17A than wild-type B6 mice, suggesting that IL-22 plays a role in C. albicans gastrointestinal infection. Collectively, our analysis of the Rag2γc mouse model revealed features of C. albicans gastrointestinal colonization and dissemination without the interference from antibiotics or chemotherapeutic agents, thus offering a new investigative tool for delineating the pathogenesis of C. albicans and its cross-talk with the gut microbiota.

The successful induction of T-cell and antibody responses by a recombinant measles virus-vectored tetravalent dengue vaccine provides partial protection against dengue-2 infection.

Dengue has a major impact on global public health, and the use of dengue vaccine is very limited. In this study, we evaluated the immunogenicity and protective efficacy of a dengue vaccine made from a recombinant measles virus (MV) that expresses envelope protein domain III (ED3) of dengue-1 to 4. Following immunization with the MV-vectored dengue vaccine, mice developed specific interferon-gamma and antibody responses against dengue virus and MV. Neutralizing antibodies against MV and dengue viruses were also induced, and protective levels of FRNT50 ≥ 10 to 4 serotypes of dengue viruses were detected in the MV-vectored dengue vaccine-immunized mice. In addition, specific interferon-gamma and antibody responses to dengue viruses were still induced by the MV-vectored dengue vaccine in mice that were pre-infected with MV. This finding suggests that the pre-existing immunity to MV did not block the initiation of immune responses. By contrast, mice that were pre-infected with dengue-3 exhibited no effect in terms of their antibody responses to MV and dengue viruses, but a dominant dengue-3-specific T-cell response was observed. After injection with dengue-2, a detectable but significantly lower viremia and a higher titer of anti-dengue-2 neutralizing antibodies were observed in MV-vectored dengue vaccine-immunized mice versus the vector control, suggesting that an anamnestic antibody response that provided partial protection against dengue-2 was elicited. Our results with regard to T-cell responses and the effect of pre-immunity to MV or dengue viruses provide clues for the future applications of an MV-vectored dengue vaccine.

The Immunodominance Change and Protection of CD4+ T-Cell Responses Elicited by an Envelope Protein Domain III-Based Tetravalent Dengue Vaccine in Mice.

Dengue is the leading cause of mosquito-borne viral infections and no vaccine is available now. Envelope protein domain III (ED3) is the major target for the binding of dengue virus neutralizing antibodies; however, the ED3-specifc T-cell response is less well understood. To investigate the T-cell responses to four serotypes of dengue virus (DENV-1 to 4), we immunized mice using either a tetravalent ED3-based DNA or protein vaccine, or combined both as a DNA prime-protein boost strategy (prime-boost). A significant serotype-dependent IFN-γ or IL-4 response was observed in mice immunized with either the DNA or protein vaccine. The IFN-γ response was dominant to DENV-1 to 3, whereas the IL-4 response was dominant to DENV-4. Although the similar IgG titers for the four serotypes were observed in mice immunized with the tetravalent vaccines, the neutralizing antibody titers varied and followed the order of 2 = 3>1>4. Interestingly, the lower IFN-γ response to DENV-4 is attributable to the immunodominance change between two CD4+ T-cell epitopes; one T-cell epitope located at E349-363 of DENV-1 to 3 was more immunogenic than the DENV-4 epitope E313-327. Despite DENV-4 specific IFN-γ responses were suppressed by immunodominance change, either DENV-4-specific IFN-γ or neutralizing antibody responses were still recalled after DENV-4 challenge and contributed to virus clearance. Immunization with the prime-boost elicited both IFN-γ and neutralizing antibody responses and provided better protection than either DNA or protein immunization. Our findings shed light on how ED3-based tetravalent dengue vaccines sharpen host CD4 T-cell responses and contribute to protection against dengue virus.

Advantage management strategy in competition via technological race perspective: empirical evidence from the Taiwanese manufacturing industry.

This study investigated the advantage management strategies of a firm regarding the technological race in the manufacturing sector. This is to reveal whether firms adopt a catch-up or leapfrogging strategy in the competition for innovation. The results show that competition is fierce in the Taiwanese manufacturing industry. Taiwanese manufacturing firms (mostly SMEs) tend to adopt the "catch-up" strategy to keep up with their competitors in order to remain in the technological race. The result indicates that, under financial constraints, Taiwanese manufacturing firms attempt to invest in R&D to catch up with their rivals or to avoid being eliminated from the race.