Post-primary Infection Research Articles

CD4+ T cells re-wire granuloma cellularity and regulatory networks to promote immunomodulation following Mtb reinfection

Immunological priming-in the context of either prior infection or vaccination-elicits protective responses against subsequent Mycobacterium tuberculosis (Mtb) infection. However, the changes that occur in the lung cellular milieu post-primary Mtb infection and their contributions to protection upon reinfection remain poorly understood. Using clinical and microbiological endpoints in a non-human primate reinfection model, we demonstrated that prior Mtb infection elicited a long-lasting protective response against subsequent Mtb exposure and was CD4+ Tcell dependent. By analyzing data from primary infection, reinfection, and reinfection-CD4+ Tcell-depleted granulomas, we found that the presence of CD4+ Tcells during reinfection resulted in a less inflammatory lung milieu characterized by reprogrammed CD8+ Tcells, reduced neutrophilia, and blunted type 1 immune signaling among myeloid cells. These results open avenues for developing vaccines and therapeutics that not only target lymphocytes but also modulate innate immune cells to limit tuberculosis (TB) disease.

Long-lived central memory γδ T cells confer protection against murine cytomegalovirus reinfection.

The involvement of γδ TCR-bearing lymphocytes in immunological memory has gained increasing interest due to their functional duality between adaptive and innate immunity. γδ T effector memory (TEM) and central memory (TCM) subsets have been identified, but their respective roles in memory responses are poorly understood. In the present study, we used subsequent mouse cytomegalovirus (MCMV) infections of αβ T cell deficient mice in order to analyze the memory potential of γδ T cells. As for CMV-specific αβ T cells, MCMV induced the accumulation of cytolytic, KLRG1+CX3CR1+ γδ TEM that principally localized in infected organ vasculature. Typifying T cell memory, γδ T cell expansion in organs and blood was higher after secondary viral challenge than after primary infection. Viral control upon MCMV reinfection was prevented when masking γδ T-cell receptor, and was associated with a preferential amplification of private and unfocused TCR δ chain repertoire composed of a combination of clonotypes expanded post-primary infection and, more unexpectedly, of novel expanded clonotypes. Finally, long-term-primed γδ TCM cells, but not γδ TEM cells, protected T cell-deficient hosts against MCMV-induced death upon adoptive transfer, probably through their ability to survive and to generate TEM in the recipient host. This better survival potential of TCM cells was confirmed by a detailed scRNASeq analysis of the two γδ T cell memory subsets which also revealed their similarity to classically adaptive αβ CD8 T cells. Overall, our study uncovered memory properties of long-lived TCM γδ T cells that confer protection in a chronic infection, highlighting the interest of this T cell subset in vaccination approaches.

Evaluation of the In Vitro Capacity of Anti-Human Cytomegalovirus Antibodies to Initiate Antibody-Dependent Cell Cytotoxicity.

In the setting of infectious diseases, antibodies show different functions beyond neutralizing activity. In this study, we investigated the activation of NK cells in vitro in the presence of human cytomegalovirus (HCMV)-specific antibodies and their potential role in the control of HCMV infection through antibody-dependent cell cytotoxicity (ADCC). Retinal pigmented epithelial cells (ARPE-19) infected with the HCMV strain VR1814 were co-cultured with cytokine-activated peripheral blood mononuclear cells (PBMCs) in the presence of sera collected from 23 HCMV-seropositive and 9 HCMV-seronegative donors. Moreover, 13 pregnant women sampled 3 and 6 months after HCMV primary infection and 13 pregnant women with pre-conception immunity were tested and compared. We determined the percentage of activated NK cells via the analysis of CD107a expression as a marker of degranulation. Significantly higher levels of NK-cell activation were observed using 1/100 and 1/10 dilutions of sera from HCMV-seropositive individuals, and when cells were infected for 96 and 120 h, suggesting that NK cells are activated by antibodies directed against late antigens. In the absence of serum NK cells, activation was negligible. In seropositive subjects, the median percentages of CD107a-positive NK cells in the presence of autologous serum and pooled HCMV-positive serum were similar (14.03% [range 0.00-33.56] and 12.42% [range 1.01-46.00], respectively), while NK-cell activation was negligible using an HCMV-negative serum pool. In HCMV-seronegative subjects, the median percentage of activated NK cells was 0.90% [range 0.00-3.92] with autologous serum and 2.07% [0.00-5.76] in the presence of the HCMV-negative serum pool, while it was 8.97% [0.00-26.49] with the pool of HCMV-positive sera. NK-cell activation using hyperimmune globulin is comparable to what is obtained using autologous serum. Sera from subjects at 3 and 6 months post primary infection showed a lower capacity of NK-cell activation than sera from subjects with past infection (p < 0.001). NK activation against HCMV-infected epithelial cells is dependent on the presence of HCMV-specific antibodies. This serum activity increases with time after the onset of HCMV infection. The protective role of NK-cell activation by HCMV-specific serum antibodies should be verified in clinical settings.

Effectiveness and duration of additional immune defense provided by SARS-CoV-2 infection before and after receiving the mRNA COVID-19 vaccine BNT162b2

BackgroundOur investigation focused whether infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) before or after receiving the mRNA COVID-19 vaccine can increase immune protection. And we also investigated relationship of infection acquired. MethodsThree shots of the mRNA coronavirus disease 2019 (COVID-19) vaccine BNT162b2 were administered to 736 healthcare workers at Tokyo Shinagawa Hospital. Serum samples were collected before the first shot (P1), at one month (P2), and at six months (P3) after the second shot and at one month after the third shot (P4). The presence of infection was assessed using IgG against the nucleocapsid (IgG (N) and RBD in the spike protein of SARS-CoV-2. We defined infection before P2 as natural infection (NI) and infection between P2 and P3 as breakthrough infection (BI) and compared susceptibility to further infection between the NI (−) and NI (+) groups and between BI (−) and BI (+) groups. Events in 485 participants who had a complete dataset of IgG (N) and IgG (RBD) from P1 to P4 were analyzed. ResultsThe presence of SARS-CoV-2 infection before P2 were examined by examining the titers of IgG (N)P1, IgG (N) P2, and IgG (RBD) P1 that exceeded the cutoff values. Consequently, 35 participants (7.22 %) were categorized into the NI (+) group, whereas 450 (92.8 %) were categorized into the NI (−) group. Between P2 and P3, the NI (−) group showed a higher rate of SARS-CoV-2 infection than the NI (+) group; however, there was no significant difference in the infection rate between P3 and P4. The infection rate was significantly lower in the BI (+) group than in the BI (−) group. Pre-primary vaccination infection significantly increased IgG (RBD) levels between P1 and P3. Post-primary vaccination infection significantly increased IgG (RBD) levels between P3 and P4. ConclusionsInfection with SARS-CoV-2 before or after receiving the mRNA COVID-19 vaccine can increase immune protection; however, the duration of this effect may be limited.

SARS-CoV-2-specific T cell responses wane profoundly in convalescent individuals 10 months after primary infection

A key question in the coronavirus disease 2019 (COVID-19) pandemic is the duration of specific T cell responses against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) post primary infection, which is difficult to address due to the large-scale COVID-19 vaccination and re-exposure to the virus. Here, we conducted an analysis of the long-term SARS-CoV-2-specific T cell responses in a unique cohort of convalescent individuals (CIs) that were among the first to be infected worldwide and without any possible antigen re-exposure since then. The magnitude and breadth of SARS-CoV-2-specific T cell responses correlated inversely with the time that had elapsed from disease onset and the age of those CIs. The mean magnitude of SARS-CoV-2-specific CD4 and CD8 T cell responses decreased about 82% and 76%, respectively, over the time period of ten months after infection. Accordingly, the longitudinal analysis also demonstrated that SARS-CoV-2-specific T cell responses waned significantly in 75% of CIs during the follow-up. Collectively, we provide a comprehensive characterization of the long-term memory T cell response in CIs, suggesting that robust SARS-CoV-2-specific T cell immunity post primary infection may be less durable than previously expected.

Changes in HCMV immune cell frequency and phenotype are associated with chronic lung allograft dysfunction.

Human cytomegalovirus (HCMV) infection is common and often severe in lung transplant recipients (LTRs), and it is a risk factor associated with chronic lung allograft dysfunction (CLAD). The complex interplay between HCMV and allograft rejection is still unclear. Currently, no treatment is available to reverse CLAD after diagnosis, and the identification of reliable biomarkers that can predict the early development of CLAD is needed. This study investigated the HCMV immunity in LTRs who will develop CLAD. This study quantified and phenotyped conventional (HLA-A2pp65) and HLA-E-restricted (HLA-EUL40) anti-HCMV CD8+ T (CD8 T) cell responses induced by infection in LTRs developing CLAD or maintaining a stable allograft. The homeostasis of immune subsets (B, CD4T, CD8 T, NK, and γδT cells) post-primary infection associated with CLAD was also investigated. At M18 post-transplantation, HLA-EUL40 CD8 T responses were less frequently found in HCMV+ LTRs (21.7%) developing CLAD (CLAD) than in LTRs (55%) keeping a functional graft (STABLE). In contrast, HLA-A2pp65 CD8 T was equally detected in 45% of STABLE and 47.8% of CLAD LTRs. The frequency of HLA-EUL40 and HLA-A2pp65 CD8 T among blood CD8 T cells shows lower median values in CLAD LTRs. Immunophenotype reveals an altered expression profile for HLA-EUL40 CD8 T in CLAD patients with a decreased expression for CD56 and the acquisition of PD-1. In STABLE LTRs, HCMV primary infection causes a decrease in B cells and inflation of CD8 T, CD57+/NKG2C+ NK, and δ2-γδT cells. In CLAD LTRs, the regulation of B, total CD8 T, and δ2+γδT cells is maintained, but total NK, CD57+/NKG2C+ NK, and δ2-γδT subsets are markedly reduced, while CD57 is overexpressed across T lymphocytes. CLAD is associated with significant changes in anti-HCMV immune cell responses. Our findings propose that the presence of dysfunctional HCMV-specific HLA-E-restricted CD8 T cells together with post-infection changes in the immune cell distribution affecting NK and γδT cells defines an early immune signature for CLAD in HCMV+ LTRs. Such a signature may be of interest for the monitoring of LTRs and may allow an early stratification of LTRs at risk of CLAD.

Distinctive phenotype for HLA-E- versus HLA-A2-restricted memory CD8 αβT cells in the course of HCMV infection discloses features shared with NKG2C+CD57+NK and δ2-γδT cell subsets.

The human cytomegalovirus (HCMV) triggers both innate and adaptive immune responses, including protective CD8+ αβT cells (CD8T) that contributes to the control of the infection. In addition to CD8T restricted by classical HLA class Ia molecules, HCMV also triggers CD8T recognizing peptides from the HCMV UL40 leader peptide and restricted by HLA-E molecules (HLA-EUL40 CD8T). This study investigated the frequency, phenotype and functions of HLA-EUL40 CD8T in comparison to the immunodominant HLA-A2pp65 CD8T upon acute (primary or secondary infection) or chronic infection in kidney transplant recipients (KTR) and in seropositive (HCMV+) healthy volunteer (HV) hosts. The frequency of hosts with detected HLA-EUL40 CD8T was similar after a primary infection (24%) and during viral latency in HCMV+ HV (26%) and equal to the frequency of HLA-A2pp65 CD8T cells in both conditions (29%). Both CD8T subsets vary from 0.1% to >30% of total circulating CD8T according to the host. Both HLA-EUL40 and HLA-A2pp65 CD8T display a phenotype specific of CD8+ TEMRA (CD45RA+/CCR7-) but HLA-EUL40 CD8T express distinctive level for CD3, CD8 and CD45RA. Tim3, Lag-3, 4-1BB, and to a lesser extend 2B4 are hallmarks for T cell priming post-primary infection while KLRG1 and Tigit are markers for restimulated and long lived HCMV-specific CD8T responses. These cell markers are equally expressed on HLA-EUL40 and HLA-A2pp65 CD8T. In contrast, CD56 and PD-1 are cell markers discriminating memory HLA-E- from HLA-A2-restricted CD8T. Long lived HLA-EUL40 display higher proliferation rate compared to HLA-A2pp65 CD8T consistent with elevated CD57 expression. Finally, a comparative immunoprofiling indicated that HLA-EUL40 CD8T, divergent from HLA-A2pp65 CD8T, share the expression of CD56, CD57, NKG2C, CD158 and the lack of PD-1 with NKG2C+CD57+ NK and δ2-γδT cells induced in response to HCMV and thus defines a common immunopattern for these subsets.

The Cross-Species Immunity During Acute Babesia Co-Infection in Mice.

Babesiosis causes high morbidity and mortality in immunocompromised individuals. An earlier study suggested that lethal Babesia rodhaini infection in murine can be evaded by Babesia microti primary infection via activated macrophage-based immune response during the chronic stage of infection. However, whether the same immune dynamics occur during acute B. microti co-infection is not known. Hence, we used the mouse model to investigate the host immunity during simultaneous acute disease caused by two Babesia species of different pathogenicity. Results showed that B. microti primary infection attenuated parasitemia and conferred immunity in challenge-infected mice as early as day 4 post-primary infection. Likewise, acute Babesia co-infection undermined the splenic immune response, characterized by the significant decrease in splenic B and T cells leading to the reduction in antibody levels and decline in humoral immunity. Interestingly, increased macrophage and natural killer splenic cell populations were observed, depicting their subtle role in the protection. Pro-inflammatory cytokines (i.e. IFN-γ, TNF-α) were downregulated, while the anti-inflammatory cytokine IL-10 was upregulated in mouse sera during the acute phase of Babesia co-infection. Herein, the major cytokines implicated in the lethality caused by B. rodhaini infection were IFN- γ and IL-10. Surprisingly, significant differences in the levels of serum IFN- γ and IL-10 between co-infected survival groups (day 4 and 6 challenge) indicated that even a two-day delay in challenge infection was crucial for the resulting pathology. Additionally, oxidative stress in the form of reactive oxygen species contributed to the severity of pathology during acute babesiosis. Histopathological examination of the spleen showed that the erosion of the marginal zone was more pronounced during B. rodhaini infection, while the loss of cellularity of the marginal zone was less evident during co-infection. Future research warrants investigation of the roles of various immune cell subtypes in the mechanism involved in the protection of Babesia co-infected hosts.

Immune durability and protection against SARS-CoV-2 re-infection in Syrian hamsters

ABSTRACT Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has caused a pandemic. As immunity to endemic human coronaviruses (i.e. NL63 or OC43) wanes leading to re-infection, it was unknown if SARS-CoV-2 immunity would also decline permitting repeat infections. Recent case reports confirm previously infected individuals can become re-infected; however, re-infection may be due to heterogeneity in the initial infection or the host immune response, or may be the result of infection with a variant strain that escapes pre-existing immunity. To control these variables, we utilized the Syrian hamster model to evaluate the duration of immunity and susceptibility to re-infection with SARS-CoV-2. Hamsters were given a primary mock or SARS-CoV-2 infection (culture media or 105 TCID50 USA/WA1/2020 isolate, respectively). Mock and SARS-CoV-2 infected hamsters were then given a secondary SARS-CoV-2 infection at 1, 2, 4, or 6 months post-primary infection (n = 14/time point/group). After the primary SARS-CoV-2 infection, hamsters developed anti-spike protein IgG, IgA, and neutralizing antibodies, and these antibodies were maintained for at least 6 months. Upon secondary SARS-CoV-2 challenge, previously SARS-CoV-2 infected animals were protected from weight loss, while all previously mock-infected animals became infected and lost weight. Importantly, despite having high titres of antibodies, one SARS-CoV-2 infected animal re-challenged at 4 months had a breakthrough infection with replicating virus in the upper and lower respiratory tract. These studies demonstrate immunity to SARS-CoV-2 is maintained for 6 months; however, protection may be incomplete and, even in the presence of high antibody titres, previously infected hosts may become re-infected.

Prolonged Protective Immunity Induced by Mild SARS-CoV-2 Infection of K18-hACE2 Mice.

Longevity of the immune response following viral exposure is an essential aspect of SARS-CoV-2 infection. Mild SARS-CoV-2 infection of K18-hACE2 mice was implemented for evaluating the mounting and longevity of a specific memory immune response. We show that the infection of K18-hACE2 mice induced robust humoral and cellular immunity (systemic and local), which persisted for at least six months. Virus-specific T cells and neutralizing antibody titers decreased over time, yet their levels were sufficient to provide sterile immunity against lethal rechallenge six months post-primary infection. The study substantiates the role of naturally induced immunity against SARS-CoV-2 infection for preventing recurring morbidity.

Effect of primary and secondary Fasciola gigantica infection on specific IgG responses, hepatic enzyme levels and weight gain in buffaloes

Buffaloes, as highly susceptible definitive hosts of Fasciola gigantica, suffer from a high infection rate of fasciolosis, which causes enormous economic losses. Repeat infection is responsible for this high rate; thus, elucidating the protective immunity mechanism in repeat infection is decisive in fasciolosis prevention. Herein, a secondary experimental infection model was established to preliminarily reveal the protective immunity that occurs in repeat infection. In brief, animals were assigned to three groups: group A (uninfected control), group B (primary infection) and group C (secondary infection). Buffaloes were autopsied 20weeks post-infection for measurements of the recovered flukes and hepatic examination. In addition, the detection of specific antibody (IgG) responses to F. gigantica excretory-secretory product (FgESP) throughout the whole period and weight gain throughout the first 4months as a percentage (%) of the starting weight were also determined. The serum hepatic enzyme gamma glutathione transferase (GGT) levels were monitored to assess hepatic damage throughout the study period. Infection establishment was compared between group B and group C. Similar specific IgG patterns were observed between group B and group C, and hepatic damage was more severe in group C than group B. Significant differences in weight gain as a percentage of the start weight were observed between group A and group B at the 3rd and 4th months postprimary infection, while significant differences were not observed between group A and group C or group B and group C. Our results suggest that challenge infection cannot induce resistance against F. gigantica in buffaloes, which is consistent with the protective immunity against Fasciola hepatica reinfection observed in sheep and goats.

Primary cytomegalovirus infection during pregnancy and congenital infection: a population-based, mother\u2013child, prospective cohort study

ObjectiveThis study assessed maternal cytomegalovirus antibodies, and the occurrence of primary and congenital cytomegalovirus infections, and risk factors of congenital infection after a maternal primary infection.Study designWe included 19,435 pregnant women in Japan, who were tested for serum cytomegalovirus antibodies before 20 gestational weeks. Immunoglobulin (Ig) G avidity was evaluated in women with both IgG and IgM antibodies; tests were repeated at ≥28 gestational weeks among women without IgG and IgM antibodies.ResultPrimary and congenital infections were 162 and 23 cases, respectively. The risk ratios for congenital infection were 8.18 (95% confidence interval: 2.44–27.40) in teenage versus older women, and 2.25 (95% confidence interval: 1.28–3.94) in parity ≥ 2 versus parity ≤ 1. Of 22 live birth congenital infection cases, three had abnormal neurological findings.ConclusionWe demonstrated teenage and parity ≥ 2 pregnant women as risk factors of post-primary congenital infection.

Assessment of the Risk of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Reinfection in an Intense Reexposure Setting.

BackgroundRisk of reinfection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is unknown. We assessed the risk and incidence rate of documented SARS-CoV-2 reinfection in a cohort of laboratory-confirmed cases in Qatar.MethodsAll SARS-CoV-2 laboratory-confirmed cases with at least 1 polymerase chain reaction–positive swab that was ≥45 days after a first positive swab were individually investigated for evidence of reinfection. Viral genome sequencing of the paired first positive and reinfection viral specimens was conducted to confirm reinfection.ResultsOut of 133 266 laboratory-confirmed SARS-CoV-2 cases, 243 persons (0.18%) had at least 1 subsequent positive swab ≥45 days after the first positive swab. Of these, 54 cases (22.2%) had strong or good evidence for reinfection. Median time between the first swab and reinfection swab was 64.5 days (range, 45–129). Twenty-three of the 54 cases (42.6%) were diagnosed at a health facility, suggesting presence of symptoms, while 31 (57.4%) were identified incidentally through random testing campaigns/surveys or contact tracing. Only 1 person was hospitalized at the time of reinfection but was discharged the next day. No deaths were recorded. Viral genome sequencing confirmed 4 reinfections of 12 cases with available genetic evidence. Reinfection risk was estimated at 0.02% (95% confidence interval [CI], .01%–.02%), and reinfection incidence rate was 0.36 (95% CI, .28–.47) per 10 000 person-weeks.ConclusionsSARS-CoV-2 reinfection can occur but is a rare phenomenon suggestive of protective immunity against reinfection that lasts for at least a few months post primary infection.

Внебольничная пневмония. Дифференциальная диагностика. COVID-19

Introduction. The paper presents the results of X-ray examination of patients with lung lesions caused by diseases and computed tomography (CT) of patients with COVID-19 of varying degrees of infiltration according to the categorical CT scheme from CO-RADS 1 to CO-RADS 6, developed by the Dutch Radiological Society (NVvR). Good results can be achieved by detecting the early stage of the disease in COVID-19. The work considers indications, contraindications, methodology and interpretation, at different phases of infil-tration in COVID-19. Objective. To review the dynamic models of CT imaging of lungs affected by COVID-19, to define CT character of primary and post-primary infection and discuss the role of imaging in differential diagnostics and monitoring of the pathology. Materials and research methods. 85 patients (the median of 48 y.o. to the 17 to 84 y.o. range) were examined. All patients un-derwent CT procedure («Toshiba Corp.» 64-sl. CT). Results. At an early stage bilateral basal peripheral changes of the «ground glass» type opacity, generally of minuscule area, pre-dominate which precurse development of viral pneumonia in COVID-19. As the disease progresses areas of change in the tissue appear patterned according to the type of «patchwork», consolidation areas form resembling OP «reverse halo». Complete resorption of changes in lungs is likely. Resolution of pathological changes could be observed after a month and longer with a successful outcome. Conclusion. At the stage of the outbreak progression the role of CT imaging methods in assessing the condition of lungs could not be overestimated. They provide means to identify changes at the subclinical stage, to assess the severity of the course and conduct differential diagnostics, but also to inform about the likelihood of COVID-19 when PCR testing results are lacking. The role of CT is in-deed prevailing in clinical conditions of limited resources and while coping with a large patient cohort with acute respiratory diseases of undefined aetiology. Key words: Differential diagnosis; CT examination; COVID-19; CO-RADS scheme.

A serological framework to investigate acute primary and post-primary dengue cases reporting across the Philippines

BackgroundIn dengue-endemic countries, targeting limited control interventions to populations at risk of severe disease could enable increased efficiency. Individuals who have had their first (primary) dengue infection are at risk of developing more severe secondary disease, thus could be targeted for disease prevention. Currently, there is no reliable algorithm for determining primary and post-primary (infection with more than one flavivirus) status from a single serum sample. In this study, we developed and validated an immune status algorithm using single acute serum samples from reporting patients and investigated dengue immuno-epidemiological patterns across the Philippines.MethodsDuring 2015/2016, a cross-sectional sample of 10,137 dengue case reports provided serum for molecular (anti-DENV PCR) and serological (anti-DENV IgM/G capture ELISA) assay. Using mixture modelling, we re-assessed IgM/G seroprevalence and estimated functional, disease day-specific, IgG:IgM ratios that categorised the reporting population as negative, historical, primary and post-primary for dengue. We validated our algorithm against WHO gold standard criteria and investigated cross-reactivity with Zika by assaying a random subset for anti-ZIKV IgM and IgG. Lastly, using our algorithm, we explored immuno-epidemiological patterns of dengue across the Philippines.ResultsOur modelled IgM and IgG seroprevalence thresholds were lower than kit-provided thresholds. Individuals anti-DENV PCR+ or IgM+ were classified as active dengue infections (83.1%, 6998/8425). IgG− and IgG+ active dengue infections on disease days 1 and 2 were categorised as primary and post-primary, respectively, while those on disease days 3 to 5 with IgG:IgM ratios below and above 0.45 were classified as primary and post-primary, respectively. A significant proportion of post-primary dengue infections had elevated anti-ZIKV IgG inferring previous Zika exposure. Our algorithm achieved 90.5% serological agreement with WHO standard practice. Post-primary dengue infections were more likely to be older and present with severe symptoms. Finally, we identified a spatio-temporal cluster of primary dengue case reporting in northern Luzon during 2016.ConclusionsOur dengue immune status algorithm can equip surveillance operations with the means to target dengue control efforts. The algorithm accurately identified primary dengue infections who are at risk of future severe disease.

Tracking the polyclonal neutralizing antibody response to a dengue virus serotype 1 type-specific epitope across two populations in Asia and the Americas

The four dengue virus serotypes (DENV1-4) cause major public health problems worldwide. Highly neutralizing type-specific human monoclonal antibodies (hmAbs) target conformation-dependent epitopes on the DENV envelope protein, including 1F4, a DENV1 type-specific hmAb. Using a recombinant DENV2 virus displaying the DENV1 1F4 epitope (rDENV2/1), we measured the proportion and kinetics of DENV1 neutralizing antibodies targeting the 1F4 epitope in individuals living in Asia and the Americas where different DENV1 genotypes were circulating. Samples from 20 individuals were analyzed 3 and 18 months post-primary DENV1 infection, alongside samples from 4 individuals collected annually for four years post-primary DENV1 infection, from two studies in Nicaragua. We also analyzed convalescent post-primary DENV1 plasma samples from Sri Lankan individuals. We found that neutralizing antibodies recognizing the 1F4 epitope vary in prevalence across both populations and were detected from 20 days to four years post-infection. Additionally, both populations displayed substantial variability, with a range of high to low proportions of DENV1 type-specific neutralizing antibodies recognizing the 1F4 epitope seen across individuals. Thus, the 1F4 epitope is a major but not exclusive target of type-specific neutralizing antibodies post-primary infection with different DENV1 genotypes in Asia and Latin America, and additional epitopes likely contribute to type-specific neutralization of DENV1.

Primary infection with dengue or Zika virus does not affect the severity of heterologous secondary infection in macaques.

Zika virus (ZIKV) and dengue virus (DENV) are genetically and antigenically related flaviviruses that now co-circulate in much of the tropical and subtropical world. The rapid emergence of ZIKV in the Americas in 2015 and 2016, and its recent associations with Guillain-Barré syndrome, birth defects, and fetal loss have led to the hypothesis that DENV infection induces cross-reactive antibodies that influence the severity of secondary ZIKV infections. It has also been proposed that pre-existing ZIKV immunity could affect DENV pathogenesis. We examined outcomes of secondary ZIKV infections in three rhesus and fifteen cynomolgus macaques, as well as secondary DENV-2 infections in three additional rhesus macaques up to a year post-primary ZIKV infection. Although cross-binding antibodies were detected prior to secondary infection for all animals and cross-neutralizing antibodies were detected for some animals, previous DENV or ZIKV infection had no apparent effect on the clinical course of heterotypic secondary infections in these animals. All animals had asymptomatic infections and, when compared to controls, did not have significantly perturbed hematological parameters. Rhesus macaques infected with DENV-2 approximately one year after primary ZIKV infection had higher vRNA loads in plasma when compared with serum vRNA loads from ZIKV-naive animals infected with DENV-2, but a differential effect of sample type could not be ruled out. In cynomolgus macaques, the serotype of primary DENV infection did not affect the outcome of secondary ZIKV infection.

The NF-kappa B regulator Bcl-3 is critical factor for memory CD8+ T cell generation

Abstract Bcl-3 is an atypical member of the IκB family. Unlike classical IκBs, Bcl-3 is not degraded in response to activation signals, but instead its expression is often induced and it acts in the nucleus to modulate transcription of NF-κB target genes by associating with p50/NF-κB1 and p52/NF-κB2 homodimers. The latter complexes do not trans-activate autonomously, and association with Bcl-3 may promote or inhibit transcription in a highly gene- and context-dependent manner. Bcl-3 has been shown in mouse models to have important biological roles in promoting adaptive and innate immune responses to infectious agents as well as autoimmunity; however, the mechanisms have not been clearly defined. Here we investigate the role of Bcl-3 in primary and secondary T cell responses to lymphocytic choriomeningitis virus (LCMV) infection. Acutely infected mixed bone marrow chimeric mice generated from WT and Bcl-3 KO mice had defective LCMV antigen-specific CD8+ T cell recall responses in the absence of Bcl-3 upon challenge with LCMV (clone 13), despite having comparable primary CD8+ T cell responses at day 8 post primary infection (acute). Bcl-3 deficient CD8+ T cells instead exhibited significantly reduced proportions of LCMV epitope specific cells after 8 weeks of acute infection. Single cell RNA sequencing analysis of sorted LCMV epitope (GP33) specific CD8+ T cells at day 8 after acute infection showed a reduced proportion of memory precursor effector cells (MPECs) in the absence of Bcl-3. This suggests a crucial role of Bcl-3 in memory CD8+ T cell generation by regulating the formation or maintenance of MPECs during the primary response.

Dynamics of Viral and Host Immune Cell MicroRNA Expression during Acute Infectious Mononucleosis.

Epstein–Barr virus (EBV) is the etiological agent of acute infectious mononucleosis (IM). Since acute IM is a self-resolving disease with most patients regaining health in 1–3 weeks there have been few studies examining molecular signatures in early acute stages of the disease. MicroRNAs (miRNAs) have been shown, however, to influence immune cell function and consequently the generation of antibody responses in IM. In this study, we performed a comprehensive analysis of differentially expressed miRNAs in early stage uncomplicated acute IM. miRNAs were profiled from patient peripheral blood obtained at the time of IM diagnosis and at subsequent time points, and pathway analysis performed to identify important immune and cell signaling pathways. We identified 215 differentially regulated miRNAs at the most acute stage of infection when the patients initially sought medical help. The number of differentially expressed miRNAs decreased to 148 and 68 at 1 and 2 months post-primary infection, with no significantly changed miRNAs identified at 7 months post-infection. Interferon signaling, T and B cell signaling and antigen presentation were the top pathways influenced by the miRNAs associated with IM. Thus, a dynamic and regulated expression profile of miRNA accompanies the early acute immune response, and resolution of infection, in IM.

Analysis of antioxidant status (Superoxide dismutase and Catalase) in primary and secondary infection of Eimeria tenella in chicken

In the present study, Superoxide Dismutase (SOD) concentration and Catalase (CAT) activity in caecal tissue of broiler chicken was determined in primary and secondary infection of Eimeria tenella. Primary infection groups were infected once with 1×104sporulated E. tenella oocysts at 3rd week of age. Secondary infection with 1×104 sporulated oocysts was performed at day 14 post- primary infection in the secondary infection group. Chickens were sacrificed by cervical dislocation at 0 hour, 2, 6, 12, 24, 48, 72 and 96 hour post primary and secondary infection and the caeca were removed. SOD and CAT enzyme were estimated from the caecal tissue homogenate. In this study, it was observed that SOD and CAT, both the enzymes were increased in initial stage of primary and secondary infection, where as in later stage of primary infection SOD was increased and CAT activity reduced, and in secondary infection vice versa.