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While progress has been made in characterizing humoral immunity to Zika virus (ZIKV) in humans, little is known regarding the corresponding T cell responses to ZIKV. Here, we investigate the kinetics and viral epitopes targeted by T cells responding to ZIKV and address the critical question of whether preexisting dengue virus (DENV) T cell immunity modulates these responses. We find that memory T cell responses elicited by prior infection with DENV or vaccination with tetravalent dengue attenuated vaccines (TDLAV) recognize ZIKV-derived peptides. This cross-reactivity is explained by the sequence similarity of the two viruses, as the ZIKV peptides recognized by DENV-elicited memory T cells are identical or highly conserved in DENV and ZIKV. DENV exposure prior to ZIKV infection also influences the timing and magnitude of the T cell response. ZIKV-reactive T cells in the acute phase of infection are detected earlier and in greater magnitude in DENV-immune patients. Conversely, the frequency of ZIKV-reactive T cells continues to rise in the convalescent phase in DENV-naive donors but declines in DENV-preexposed donors, compatible with more efficient control of ZIKV replication and/or clearance of ZIKV antigen. The quality of responses is also influenced by previous DENV exposure, and ZIKV-specific CD8 T cells from DENV-preexposed donors selectively upregulated granzyme B and PD1, unlike DENV-naive donors. Finally, we discovered that ZIKV structural proteins (E, prM, and C) are major targets of both the CD4 and CD8 T cell responses, whereas DENV T cell epitopes are found primarily in nonstructural proteins.IMPORTANCE The issue of potential ZIKV and DENV cross-reactivity and how preexisting DENV T cell immunity modulates Zika T cell responses is of great relevance, as the two viruses often cocirculate and Zika virus has been spreading in geographical regions where DENV is endemic or hyperendemic. Our data show that memory T cell responses elicited by prior infection with DENV recognize ZIKV-derived peptides and that DENV exposure prior to ZIKV infection influences the timing, magnitude, and quality of the T cell response. Additionally, we show that ZIKV-specific responses target different proteins than DENV-specific responses, pointing toward important implications for vaccine design against this global threat.

In 2018 there was a large yellow fever outbreak in São Paulo, Brazil, with a high fatality rate. Yellow fever virus can cause, among other symptoms, hemorrhage and disseminated intravascular coagulation, indicating a role for endothelial cells in disease pathogenesis. Here, we conducted a case-control study and measured markers related to endothelial damage in plasma and its association with mortality. We found that angiopoietin 2 is strongly associated with a fatal outcome and could serve as a predictive marker for mortality. This could be used to monitor severe cases and provide care to improve disease outcome. [ABSTRACT FROM AUTHOR]

Background: Yellow fever is a mosquito-borne zoonotic disease, caused by yellow fever virus (YFV). Between 2017-2019 more than 504 human cases and 176 deaths were confirmed in the outskirts of São Paulo city. Throughout this outbreak, studies suggested a potential association between YFV viremia and mortality.Methods: Viral RNA was measured using RT-qPCR in plasma samples collected at up to 5 time points, between 3-120 days after symptoms onset.Results: 84 patients with confirmed YFV infection were included. Most were males; median age was 42, and 30 (36%) died. Deceased patients were older than survivors (p = 0.003) and had a higher viremia across all time points (p = 0.0006). Mean values of viremia had a positive, statistically significant correlation with peak values of neutrophils, indirect bilirubin, AST, INR and creatinine. Finally, a Cox proportional hazards model adjusted for age and laboratory variables showed that viremia is independently associated with death, with a mean 1.84-fold increase (84%) in the hazard of death (p < 0.001) for each unit increase in mean log10 viremia.Conclusion: Our results raise the importance of monitoring YFV viremia and suggest a potential benefit of antiviral drugs or neutralizing monoclonal antibodies early in the course of this infection to improve disease outcomes. [ABSTRACT FROM AUTHOR]

Background:The aim of this study was to evaluate the frequency, spectrum, in-hospital mortality rate, and factors associated with death in people living with HIV/AIDS (PLWHA) presenting with neurological diseases from a middle-income country, as well as estimate its one-year global death rate. Methods:This prospective observational cohort study was conducted at a Brazilian tertiary health center between January and July 2017. HIV-infected patients above 18 years of age who were admitted due to neurological complaints were consecutively included. A standardized neurological examination and patient and/or medical assistant interviews were performed weekly until the patient's discharge or death. The diagnostic and therapeutic management of the included cases followed institutional routines. Results:A total of 105 (13.2%) patients were included among the 791 hospitalized PLWHA. The median age was 42.8 [34-51] years, and 61% were men. The median CD4+ lymphocyte cell count was 70 (27-160) cells/mm3, and 90% of patients were experienced in combined antiretroviral therapy. The main diseases were cerebral toxoplasmosis (36%), cryptococcal meningitis (14%), and tuberculous meningitis (8%). Cytomegalovirus causing encephalitis, polyradiculopathy, and/or retinitis was the third most frequent pathogen (12%). Moreover, concomitant neurological infections occurred in 14% of the patients, and immune reconstitution inflammatory syndrome-related diseases occurred in 6% of them. In-hospital mortality rate was 12%, and multivariate analysis showed that altered level of consciousness (P = 0.04; OR: 22.7, CI 95%: 2.6-195.1) and intensive care unit (ICU) admission (P = 0.014; OR: 6.2, CI 95%: 1.4-26.7) were associated with death. The one-year global mortality rate was 31%. Conclusion:In this study, opportunistic neurological diseases were predominant. Cytomegalovirus was a frequent etiological agent, and neurological concomitant diseases were common. ICU admission and altered levels of consciousness were associated with death. Although in-hospital mortality was relatively low, the one-year global death rate was higher. [ABSTRACT FROM AUTHOR]

Background: Dengue is a major public health problem worldwide. Assessment of adaptive immunity is important to understanding immunopathology and to define correlates of protection against dengue virus (DENV). To enable global assessment of CD4+ T cell responses, we mapped HLA-DRB1-restricted DENV-specific CD4+ T cell epitopes in individuals previously exposed to DENV in the general population of the dengue-endemic region of Managua, Nicaragua. Methods: HLA class II epitopes in the population of Managua were identified by an in vitro IFNγ ELISPOT assay. CD4+ T cells purified by magnetic bead negative selection were stimulated with HLA-matched epitope pools in the presence of autologous antigen-presenting cells, followed by pool deconvolution to identify specific epitopes. The epitopes identified in this study were combined with those previously identified in the DENV endemic region of Sri Lanka, to generate a "megapool" (MP) consisting of 180 peptides specifically designed to achieve balanced HLA and DENV serotype coverage. The DENV CD4MP180 was validated by intracellular cytokine staining assays. Results: We detected responses directed against a total of 431 epitopes, representing all 4 DENV serotypes, restricted by 15 different HLA-DRB1 alleles. The responses were associated with a similar pattern of protein immunodominance, overall higher magnitude of responses, as compared to what was observed previously in the Sri Lanka region. Based on these epitope mapping studies, we designed a DENV CD4 MP180 with higher and more consistent coverage, which allowed the detection of CD4+ T cell DENV responses ex vivo in various cohorts of DENV exposed donors worldwide, including donors from Nicaragua, Brazil, Singapore, Sri Lanka, and U.S. domestic flavivirus-naïve subjects immunized with Tetravalent Dengue Live-Attenuated Vaccine (TV005). This broad reactivity reflects that the 21 HLA-DRB1 alleles analyzed in this and previous studies account for more than 80% of alleles present with a phenotypic frequency ≥5% worldwide, corresponding to 92% phenotypic coverage of the general population (i.e., 92% of individuals express at least one of these alleles). Conclusion: The DENV CD4 MP180 can be utilized to measure ex vivo responses to DENV irrespective of geographical location. [ABSTRACT FROM AUTHOR]

In 2018 there was a large yellow fever outbreak in São Paulo, Brazil, with a high fatality rate. Yellow fever virus can cause, among other symptoms, hemorrhage and disseminated intravascular coagulation, indicating a role for endothelial cells in disease pathogenesis. Here, we conducted a case-control study and measured markers related to endothelial damage in plasma and its association with mortality. We found that angiopoietin 2 is strongly associated with a fatal outcome and could serve as a predictive marker for mortality. This could be used to monitor severe cases and provide care to improve disease outcome., Competing Interests: Potential conflicts of interest. All authors: No reported conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed., (© The Author(s) 2023. Published by Oxford University Press on behalf of Infectious Diseases Society of America.)

Background: Dengue is a major public health problem worldwide. Assessment of adaptive immunity is important to understanding immunopathology and to define correlates of protection against dengue virus (DENV). To enable global assessment of CD4 + T cell responses, we mapped HLA-DRB1-restricted DENV-specific CD4 + T cell epitopes in individuals previously exposed to DENV in the general population of the dengue-endemic region of Managua, Nicaragua., Methods: HLA class II epitopes in the population of Managua were identified by an in vitro IFNγ ELISPOT assay. CD4 + T cells purified by magnetic bead negative selection were stimulated with HLA-matched epitope pools in the presence of autologous antigen-presenting cells, followed by pool deconvolution to identify specific epitopes. The epitopes identified in this study were combined with those previously identified in the DENV endemic region of Sri Lanka, to generate a "megapool" (MP) consisting of 180 peptides specifically designed to achieve balanced HLA and DENV serotype coverage. The DENV CD4MP 180 was validated by intracellular cytokine staining assays., Results: We detected responses directed against a total of 431 epitopes, representing all 4 DENV serotypes, restricted by 15 different HLA-DRB1 alleles. The responses were associated with a similar pattern of protein immunodominance, overall higher magnitude of responses, as compared to what was observed previously in the Sri Lanka region. Based on these epitope mapping studies, we designed a DENV CD4 MP 180 with higher and more consistent coverage, which allowed the detection of CD4 + T cell DENV responses ex vivo in various cohorts of DENV exposed donors worldwide, including donors from Nicaragua, Brazil, Singapore, Sri Lanka, and U.S. domestic flavivirus-naïve subjects immunized with Tetravalent Dengue Live-Attenuated Vaccine (TV005). This broad reactivity reflects that the 21 HLA-DRB1 alleles analyzed in this and previous studies account for more than 80% of alleles present with a phenotypic frequency ≥5% worldwide, corresponding to 92% phenotypic coverage of the general population (i.e., 92% of individuals express at least one of these alleles)., Conclusion: The DENV CD4 MP 180 can be utilized to measure ex vivo responses to DENV irrespective of geographical location.