Distribution of Dengue and Zika Virus IgG Immunoglobulin

Introduction. Dengue Virus (DENV) and Zika Virus (ZIKV) are viruses that belong to the Flavivirus family. They are transmitted by the Aedes aegypti species of mosquitoes. Infection with DENV can result in no symptoms, mild symptoms which include fever, rash, and headache (dengue fever) or more severe symptoms which include hemorrhage, dengue hemorrhagic fever (DHF) and shock, dengue shock syndrome (DSS). ZIKV, until recently caused mild disease but an outbreak in Brazil was associated with fetal complications such as microcephaly or Guillain-Barré syndrome in adults. Due to the similarity between ZIKV and DENV, antibodies (Abs) generated in humans to these pathogens are of great interest. Methods We used an Enzyme-Linked Immunosorbent Assay (ELISA), to measure IgG subclass Abs (concentrations) in sera obtained from DENV and ZIKV immune donors. The sera were assayed to measure ZIKV and DENV-specific Abs using well characterized isotype-specific secondary Abs (IgG, IgG1-Fc, IgG1-Hinge, IgG2, IgG3 and IgG4). The data was analyzed to compare antibody responses to multiple flavivirus antigens in the sera. Antibody composition can provide information about B-cell mediated immune response. Results. Several observations were made after assessing Ab responses in the sera from immune donors. We observed high IgG Abs to ZIKV virus like particles (VLPs) in sera from all donors. Additionally, IgG1 responses were dominant among subtypes as expected. Conclusions. This study generated data that was used to develop a profile of DENV and ZIKV -specific Abs which can be used to further develop an understanding of the immune response to these flaviviruses

T lymphocyte responses to flaviviruses — diverse cell populations affect tendency toward protection and disease

Dengue virus (DENV), Yellow Fever virus, West Nile virus, Japanese encephalitis virus and Zika virus are medically important flaviviruses transmitted to humans by mosquitoes and circulate in overlapping geographic areas. Cross-reactive immune responses have been demonstrated among the flaviviruses, particularly the four DENV serotypes. The immunological imprint left by a flavivirus infection can therefore have profound effects on the responses to subsequent infections. In this review we summarize recent research focusing on T cell responses to DENV using clinical samples from prospective cohort studies in Asia. These data suggest that durability of different T cell populations after natural infection or vaccination is an important consideration for the outcome of subsequent flavivirus exposures and we argue for continued investigation in the context of longitudinal cohort studies

Analysis of Cell-Mediated Immune Responses in Support of Dengue Vaccine Development Efforts

Dengue vaccine development has made significant strides, but a better understanding of how vaccine-induced immune responses correlate with vaccine efficacy can greatly accelerate development, testing, and deployment as well as ameliorate potential risks and safety concerns. Advances in basic immunology knowledge and techniques have already improved our understanding of cell-mediated immunity of natural dengue virus infection and vaccination. We conclude that the evidence base is adequate to argue for inclusion of assessments of cell-mediated immunity as part of clinical trials of dengue vaccines, although further research to identify useful correlates of protective immunity is needed

Telomere length dynamics in human memory T cells specific for viruses causing acute or latent infections

BACKGROUND: Declining telomere length (TL) is associated with T cell senescence. While TL in naive and memory T cells declines with increasing age, there is limited data on TL dynamics in virus-specific memory CD4+ T cells in healthy adults. We combined BrdU-labeling of virus-stimulated T cells followed with flow cytometry-fluorescent in situ hybridization for TL determination. We analyzed TL in T cells specific for several virus infections: non-recurring acute (vaccinia virus, VACV), recurring-acute (influenza A virus, IAV), and reactivating viruses (varicella-zoster virus, VZV, and cytomegalovirus, CMV) in 10 healthy subjects. Additionally, five subjects provided multiple blood samples separated by up to 10 years. RESULTS: VACV- and CMV-specific T cells had longer average TL than IAV-specific CD4+ T cells. Although most virus-specific cells were CD45RA-, we observed a minor population of BrdU+ CD45RA+ T cells characterized by long telomeres. Longitudinal analysis demonstrated a slow decline in average TL in virus-specific T cells. However, in one subject, VZV reactivation led to an increase in average TL in VZV-specific memory T cells, suggesting a conversion of longer TL cells from the naive T cell repertoire. CONCLUSIONS: TLs in memory CD4+ T cells in otherwise healthy adults are heterogeneous and follow distinct virus-specific kinetics. These findings suggests that the distribution of TL and the creation and maintenance of long TL memory T cells could be important for the persistence of long-lived T cell memory

Defective pro-IL-1beta responses in macrophages from aged mice

BACKGROUND: Cytokines regulated by the inflammasome pathway have been extensively implicated in various age-related immune pathologies. We set out to elucidate the contribution of the nod-like receptor protein 3 (NLRP3) inflammasome pathway to the previously described deficiencies in IL-1beta production by macrophages from aged mice. We examined the production of pro-IL-1beta and its conversion into IL-1beta as two separate steps and compared these cytokine responses in bone marrow derived macrophages from young (6-8 weeks) and aged (18-24 months) C57BL/6 mice. FINDINGS: Relative to macrophages from young mice, macrophages from aged mice produced less pro-IL-1beta after TLR4 stimulation with LPS. However upon activation of the NLRP3 inflammasome with ATP, macrophages from young and aged mice were able to efficiently convert and secrete intracellular pro-cytokines as functional cytokines. CONCLUSIONS: Lower levels of IL-1beta production are a result of slower and lower overall production of pro-IL-1beta in macrophages from aged mice

Robust Intrapulmonary CD8 T Cell Responses and Protection with an Attenuated N1L Deleted Vaccinia Virus

BACKGROUND: Vaccinia viruses have been used as a model for viral disease and as a protective live vaccine. METHODOLOGY AND PRINCIPAL FINDINGS: We investigated the immunogenicity of an attenuated strain of vaccinia virus engineered to inactivate the N1L gene (vGK5). Using the intranasal route, this recombinant virus was 2 logs less virulent compared to the wildtype VACV-WR. Infection by the intranasal, intraperitoneal, and tail scarification routes resulted in the robust induction of cytolytic virus-specific CD8 T cells in the spleens and the lungs. VACV-specific antibodies were also detected in the sera of mice infected 3-5 months prior with the attenuated vGK5 virus. Finally, mice immunized with vGK5 were significantly protected when challenged with a lethal dose of VACV-WR. CONCLUSIONS: These results indicate that the attenuated vGK5 virus protects against subsequent infection and suggest that the N1L protein limits the strength of the early antiviral CD8 T cell response following respiratory infection

Longitudinal Analysis of Dengue Virus–Specific Memory T Cell Responses and Their Association With Clinical Outcome in Subsequent DENV Infection

Memory T cells resulting from primary dengue virus (DENV) infection are hypothesized to influence the clinical outcome of subsequent DENV infection. However, the few studies involving prospectively collected blood samples have found weak and inconsistent associations with outcome and variable temporal trends in DENV-specific memory T cell responses between subjects. This study used both ex-vivo and cultured ELISPOT assays to further evaluate the associations between DENV serotype-cross-reactive memory T cells and severity of secondary infection. Using ex-vivo ELISPOT assays, frequencies of memory T cells secreting IFN-γ in response to DENV structural and non-structural peptide pools were low in PBMC from multiple time points prior to symptomatic secondary DENV infection and showed a variable response to infection. There were no differences in responses between subjects who were not hospitalized (NH, n=6) and those who were hospitalized with dengue hemorrhagic fever (hDHF, n=4). In contrast, responses in cultured ELISPOT assays were more reliably detectable prior to secondary infection and showed more consistent increases after infection. Responses in cultured ELISPOT assays were higher in individuals with hDHF (n=8) compared to NH (n=9) individuals before the secondary infection, with no difference between these groups after infection. These data demonstrate an association of pre-existing DENV-specific memory responses with the severity of illness in subsequent DENV infection, and suggest that frequencies of DENV-reactive T cells measured after short-term culture may be of particular importance for assessing the risk for more severe dengue disease

Longitudinal Analysis of Memory B and T Cell Responses to Dengue Virus in a 5-Year Prospective Cohort Study in Thailand

Prior exposure to dengue virus (DENV) has a profound impact on the outcome of infection, which varies according to the interval between infections. Antibodies secreted by B cells and cytokines secreted by T cells are thought to contribute both to protective immunity against DENV and the pathogenesis of dengue disease. We analyzed peripheral blood mononuclear cells (PBMC) collected from Thai children over a 5-year prospective cohort study to define the dynamics of DENV-specific memory B and T cell responses and the impact of symptomatic or subclinical DENV infections. To measure B cell responses, PBMC were stimulated with IL-2 plus R848 and culture supernatants were tested for DENV-binding antibodies by ELISA. To measure T cell responses, PBMC were stimulated in dual-color ELISPOT assays with overlapping peptide pools of structural and non-structural proteins from the four DENV types. B cell responses were low to one or more DENV types prior to symptomatic infection and increased with reactivity to all four types after infection. Subjects who had a subclinical infection or who did not experience a DENV infection during the study period showed strong memory B cell responses to all four DENV types. T cell responses to DENV peptides demonstrated a cytokine hierarchy of IFN-γ \u3e IL-2 \u3e IFN-γ/IL-2. T cell responses were low or absent prior to secondary infections. The trends in T cell responses to DENV peptides over 3 year post-infection were highly variable, but subjects who had experienced a secondary DENV1 infection showed higher cytokine responses compared to subjects who had experienced a secondary DENV2 or subclinical infection. The longitudinal nature of our study demonstrates persistent memory B cell responses over years and a lasting but variable impact of secondary DENV infection on DENV-specific T cell responses

Cross-Reactivity and Expansion of Dengue-Specific T cells During Acute Primary and Secondary Infections in Humans

Serotype-cross-reactive memory T cells responding to secondary dengue virus (DENV) infection are thought to contribute to disease. However, epitope-specific T cell responses have not been thoroughly compared between subjects with primary versus secondary DENV infection. We studied CD8+ T cells specific for the HLA-A*1101-restricted NS3133 epitope in a cohort of A11+ DENV-infected patients throughout acute illness and convalescence. We compared the expansion, serotype-cross-reactivity, and activation of these cells in PBMC from patients experiencing primary or secondary infection and mild or severe disease by flow cytometry. Our results show expansion and activation of DENV-specific CD8+ T cells during acute infection, which are predominantly serotype-cross-reactive regardless of DENV infection history. These data confirm marked T cell activation and serotype-cross-reactivity during the febrile phase of dengue; however, A11-NS3133-specific responses did not correlate with prior antigenic exposure or current disease severity