Medical Microbiology and Immunology最新文献

Human cytomegalovirus (CMV) is a widespread persistent herpes virus requiring lifelong immune surveillance to maintain latency. Such long-term interactions with the immune system may be associated with deleterious effects including immune exhaustion and senescence. Regarding the COVID-19 pandemic, we asked whether CMV-specific cellular and humoral activity could influence immune responses toward SARS-CoV-2 and/or disease severity. All adults with mild (n = 15) and severe (n = 14) COVID-19 were seropositive for anti-CMV IgG, but negative for IgM antibodies. Antibody titers did not correlate with COVID-19 severity. Six patients presented elevated frequencies of CMV-specific CD4 + and CD8 + T cells producing IFNγ, IL-17, and TNFα, designated as CMV high responders (hiT CMV). In comparison to low CMV responders, hiT CMV individuals exhibited higher frequencies of SARS-CoV-2-specific CD4 + IL-17 + and CD8 + IFNγ + , IL-17 + or TNFα + T cells. These results indicate that high frequencies of CMV-specific T cells may be associated with a SARS-CoV-2-reactive profile skewed toward Th17-dominated immunity.

The SARS-CoV-2 virus has been rapidly evolving over the time and the genetic variation has led to the generation of Variants of Concerns (VoC), which have shown increased fitness. These VoC viruses contain the key mutations in the spike protein which have allowed better survival and evasion of host defense mechanisms. The D614G mutation in the spike domain is found in the majority of VoC; additionally, the P681R/H mutation at the S1/S2 furin cleavage site junction is also found to be highly conserved in major VoCs; Alpha, Delta, Omicron, and its' current variants. The impact of these genetic alterations of the SARS-CoV-2 VoCs on the host cell entry, transmissibility, and infectivity has not been clearly identified. In our study, Delta and D614G + P681R synthetic double mutant pseudoviruses showed a significant increase in the cell entry, cell-to-cell fusion and infectivity. In contrast, the Omicron and P681H synthetic single mutant pseudoviruses showed TMPRSS2 independent cell entry, less fusion and infectivity as compared to Delta and D614G + P681R double mutants. Addition of exogenous trypsin further enhanced fusion in Delta viruses as compared to Omicron. Furthermore, Delta viruses showed susceptibility to both E64d and Camostat mesylate inhibitors suggesting, that the Delta virus could exploit both endosomal and TMPRSS2 dependent entry pathways as compared to the Omicron virus. Taken together, these results indicate that the D614G and P681R/H mutations in the spike protein are pivotal which might be favoring the VoC replication in different host compartments, and thus allowing a balance of mutation vs selection for better long-term adaptation.

Recent studies have noted an increasing number of Kawasaki-like cases in the pediatric population following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. In the literature, the condition is described as multiple inflammatory syndrome in children (MIS-C) or pediatric inflammatory syndrome (PIMS). A similar clinical course of Kawasaki disease (KD) and MIS-C causes difficulties in distinguishing between both conditions. However, the differential diagnosis is crucial since patients with MIS-C can present severe symptoms (myocardial dysfunction, fever, mucocutaneous symptoms) and require more extensive monitoring during treatment than children diagnosed with KD. Along with assessing epidemiological and genetic factors, it is imperative to estimate the risk of developing MIS-C in KD patients with confirmed SARS-CoV-2 infection. Genetic predispositions, such as the ITPKC gene polymorphism in KD, ACE deletion (D) polymorphism in SARS-CoV-2, and inborn errors of immunity (IEIs) in MIS-C affect the regulation of immune system complex clearances and cellular adaptations. The virus has a tropism for both vascular and respiratory cells, which further causes additional symptoms necessitating standard therapy with antithrombotic treatment. The diagnostic criteria for KD, MIS-C, and SARS-CoV-2 help differentiate each condition and optimize treatment strategies. Unfortunately, long-term outcomes in KD patients who develop MIS-C due to SARS-CoV-2 infection have been inadequately documented due to the timing of the pandemic, further displaying the need for longitudinal studies in these patients. This review underlines the differences in diagnosis and treatment of KD and MIS-C. Overall, children with KD may develop MIS-C in the setting of SARS-CoV-2 infection, but further research is needed to outline specific etiologies, prognostic factors, and diagnoses.

The understanding of the host immune response to SARS-CoV-2 variants of concern is critical for improving diagnostics, therapy development, and vaccines. Here, we analyzed the level of neutralizing antibodies against SARS-CoV-2 D614G, Delta, Gamma, Mu, and Omicron variants in D614G infected healthcare workers during a follow-up up to 6 months after recovery. We followed up 76 patients: 60.5% were women and 39.5% men. The 96.1% and 3.9% were symptomatic and asymptomatic, respectively. The most frequent symptoms were headache, myalgia, and cough. The 65.8%, 65.8%, and 92.1% of the infected individuals were positive for neutralizing antibodies against D614G variant at 2, 4, and 6 months of follow-up, respectively. The 26.3%, 48.7% and 65.8% of patients neutralized Delta variant, 19.7%, 32.9% and 52.6% of patients neutralized Gamma, 7.9%, 19.7% and 44.7% of patients neutralized Mu, and 4.0%, 9.2% and 15.8% of patients neutralized Omicron. Low neutralization against Gamma and Mu variants was observed during the follow-up, and very low against the Omicron variant was detected during the same period. The median of neutralizing antibody titers against D614G and Delta variants increased significantly during the follow-up. An association was observed between the levels of neutralizing antibodies against D614G and Delta variants and the severity of the disease. Our results suggest an immune escape from neutralizing antibodies with the Omicron variant because of the many mutations localized in the S protein.

During 2022, the COVID-19 pandemic has been dominated by the variant of concern (VoC) Omicron (B.1.1.529) and its rapidly emerging subvariants, including Omicron-BA.1 and -BA.2. Rapid antigen tests (RATs) are part of national testing strategies to identify SARS-CoV-2 infections on site in a community setting or to support layman's diagnostics at home. We and others have recently demonstrated an impaired RAT detection of infections caused by Omicron-BA.1 compared to Delta. Here, we evaluated the performance of five SARS-CoV-2 RATs in a single-centre laboratory study examining a total of 140 SARS-CoV-2 PCR-positive respiratory swab samples, 70 Omicron-BA.1 and 70 Omicron-BA.2, as well as 52 SARS-CoV-2 PCR-negative swabs collected from March 8th until April 10th, 2022. One test did not meet minimal criteria for specificity. In an assessment of the analytical sensitivity in clinical specimen, the 50% limit of detection (LoD50) ranged from 4.2 × 10⁴ to 9.2 × 10⁵ RNA copies subjected to the RAT for Omicron-BA.1 compared to 1.3 × 10⁵ to 1.5 × 10⁶ for Omicron-BA.2. Overall, intra-assay differences for the detection of Omicron-BA.1-containing and Omicron-BA.2-containing samples were non-significant, while a marked overall heterogeneity among the five RATs was observed. To score positive in these point-of-care tests, up to 22-fold (LoD50) or 68-fold (LoD95) higher viral loads were required for the worst performing compared to the best performing RAT. The rates of true-positive test results for these Omicron subvariant-containing samples in the highest viral load category (Ct values < 25) ranged between 44.7 and 91.1%, while they dropped to 8.7 to 22.7% for samples with intermediate Ct values (25-30). In light of recent reports on the emergence of two novel Omicron-BA.2 subvariants, Omicron-BA.2.75 and BJ.1, awareness must be increased for the overall reduced detection rate and marked differences in RAT performance for these Omicron subvariants.

It has been reported that IL-33 receptor ST2 deficiency mitigates Cryptococcus neoformans (C. neoformans) pulmonary infection in BALB/c mice. IL-33 may modulate immune responses in ST2-dependent and ST2-independent manners. The host genetic background (i.e., BALB/c, C57BL/6 J) influences immune responses against C. neoformans. In the present study, we aimed to explore the roles of IL-33 and ST2 in pulmonary C. neoformans-infected mice on a C57BL/6 J genetic background. C. neoformans infection increased IL-33 expression in lung tissues. IL-33 deficiency but not ST2 deficiency significantly extended the survival time of C. neoformans-infected mice. In contrast, either IL-33 or ST2 deficiency reduced fungal burdens in lung, spleen and brain tissues from the mice following C. neoformans intratracheal inoculation. Similarly, inflammatory responses in the lung tissues were more pronounced in both the IL-33^-/- and ST2^-/- infected mice. However, mucus production was decreased in IL-33^-/- infected mice alone, and the level of IL-5 in bronchoalveolar lavage fluid (BALF) was substantially decreased in the IL-33^-/- infected mice but not ST2^-/- infected mice. Moreover, IL-33 deficiency but not ST2 deficiency increased iNOS-positive macrophages. At the early stage of infection, the reduced pulmonary fungal burden in the IL-33^-/- and ST2^-/- mice was accompanied by increased neutrophil infiltration. Collectively, IL-33 regulated pulmonary C. neoformans infection in an ST2-dependent and ST2-independent manner in C57BL/6 J mice.

Parasite of genus Leishmania viz. L. donovani and L. infantum cause visceral leishmaniasis (VL) or Kala-azar, systemic disease with significant enlargement of the liver and spleen, weight loss, anemia, fever and immunosuppression. The silent expansion of vectors, reservoir hosts and resistant strains is also of great concern in VL control. Considering all these issues, the present study focused on in vitro and in vivo antileishmanial screening of ellagic acid (EA) against L. donovani. The in vitro study was performed against the protozoan parasite L. donovani and a 50% inhibitory concentration was calculated. The DNA arrest in the sub-G0/G1 phase of the cell cycle was studied. In vivo studies included the assessment of parasite burden and immunomodulation in response to treatment of ellagic acid in BALB/c mice. The levels of Th1 and Th2 cytokines and isotype antibodies were assessed in different groups of mice. EA showed in vitro parasiticidal activity with IC₅₀ 18.55 µg/mL and thwarted cell-cycle progression at the sub-G0/G1 phase. Administration of ellagic acid to the BALB/c mice reported diminution of splenic and hepatic parasite burden coupled with an expansion of CD4⁺ and CD8⁺ T lymphocytes. EA further potentiated a protective immune response with augmentation of Th1 type immune response evidenced by elevation of serum IgG2a levels and DTH response. EA was reported to be safe and non-toxic to the THP-1 cell line as well as to the liver and kidneys of mice. These findings endorse the therapeutic potential of EA with significant immunomodulation and can serve as a promising agent against this debilitating parasitic disease.

Measurement of anti-pneumococcal capsular polysaccharides (anti-PnPs) IgG titers is an important tool in the immunologic assessment of patients with suspected immunodeficiency disorders (ID) to reduce the morbi-mortality and minimize severe infections. Retrospectively, we studied the relationship among anti-PnPs IgG response to 3 doses of Prevenar®13, levels of immune system components, leukocyte populations, and clinical data in children with ID. Serum samples were collected at least 4 weeks post vaccination. Subsequently, multi-serotype enzyme-linked immunosorbent assay (ELISA) was performed. Eighty-seven children (under 12 years) were enrolled. Primary immunodeficiency disorder (PID) was the most common disorder (45) followed by possible immunodeficiency disorder (POID) (19), secondary immunodeficiency disorder (SID) (15), and mixed immunodeficiency disorder (MID) (8). The median age was 3 (1.50-5.33) years, 65% of patients were male. Deficient production of anti-PnPs IgG (titer ≤ 50 mg/L) was detected in 47 patients (54%), especially in the MID group, all of them under immunosuppressive therapy. In PCV13 responders, the mean of leukocyte population levels was higher with statistically significance differences in CD4 + /CD8 + T lymphocytes (p = 0.372, p = 0.014) and CD56 + /CD16 + NK (p = 0.016). Patients with previous bone marrow transplantation were the worst PCV13 responders. Pneumococcal IgG antibody titers (post-vaccination) along with clinical and analytical markers represented.

Interleukin-17 (IL-17) is involved in host defense against bacterial infection. Little is known about the role of IL-17 in A. baumannii-infected pneumonia. Our objective was to investigate the role of IL-17 in pulmonary A. baumannii infection in a mouse model. We infected C57BL/6 mice intra-tracheally (i.t.) with A. baumannii to establish pneumonia model and found A. baumannii infection elevated IL-17 expression in lungs. IL-17-deficient (Il17^-/-) mice were resistant to pulmonary A. baumannii infection, showing improved mice survival, reduced bacteria burdens, and alleviated lung inflammation. Further, treatment of A. baumannii-infected Il17^-/- mice with IL-17 exacerbated the severity of pneumonia. These data suggest a pathogenic role of IL-17 in pulmonary A. baumannii infection. Further, the infiltration and phagocytic function of neutrophils in broncho-alveolar lavage fluid were detected by flow cytometry. The results showed that Il17^-/- mice had increased neutrophil infiltration and enhanced phagocytosis in neutrophils at the early time of infection. Treatment of mice with IL-17 suppressed phagocytic function of neutrophils. All data suggest that IL-17 promotes susceptibility of mice to pulmonary A. baumannii infection by suppressing neutrophil phagocytosis at early time of infection. Targeting IL-17 might be a potential therapeutic strategy in controlling the outcome of A. baumannii pneumonia.