Longitudinal Analysis of Memory T-Cell Responses in Survivors of Middle East Respiratory Syndrome.

BACKGROUND: Middle East respiratory syndrome (MERS) is a highly lethal respiratory disease caused by a zoonotic betacoronavirus. The development of effective vaccines and control measures requires a thorough understanding of the immune response to this viral infection. METHODS: We investigated cellular immune responses up to 5 years after infection in a cohort of 59 MERS survivors by performing enzyme-linked immunospot assay and intracellular cytokine staining after stimulation of peripheral blood mononuclear cells with synthetic viral peptides. RESULTS: Memory T-cell responses were detected in 82%, 75%, 69%, 64%, and 64% of MERS survivors from 1-5 years post-infection, respectively. Although the frequency of virus-specific interferon gamma (IFN-γ)-secreting T cells tended to be higher in moderately/severely ill patients than in mildly ill patients during the early period of follow-up, there was no significant difference among the different clinical severity groups across all time points. While both CD4+ and CD8+ T cells were involved in memory T-cell responses, CD4+ T cells persisted slightly longer than CD8+ T cells. Both memory CD4+ and CD8+ T cells recognized the E/M/N proteins better than the S protein and maintained their polyfunctionality throughout the period examined. Memory T-cell responses correlated positively with antibody responses during the initial 3-4 years but not with maximum viral loads at any time point. CONCLUSIONS: These findings advance our understanding of the dynamics of virus-specific memory T-cell immunity after MERS-coronavirus infection, which is relevant to the development of effective T cell-based vaccines.

Clinical Characteristics and Risk Factors for Mortality in Critical Coronavirus Disease 2019 Patients 50 Years of Age or Younger During the Delta Wave: Comparison With Patients > 50 Years in Korea.

BACKGROUND: Numerous patients around the globe are dying from coronavirus disease 2019 (COVID-19). While age is a known risk factor, risk analysis in the young generation is lacking. The present study aimed to evaluate the clinical features and mortality risk factors in younger patients (≤ 50 years) with a critical case of COVID-19 in comparison with those among older patients (> 50 years) in Korea. METHODS: We analyzed the data of adult patients only in critical condition (requiring high flow nasal cannula oxygen therapy or higher respiratory support) hospitalized with PCR-confirmed COVID-19 at 11 hospitals in Korea from July 1, 2021 to November 30, 2021 when the delta variant was a dominant strain. Patients' electronic medical records were reviewed to identify clinical characteristics. RESULTS: During the study period, 448 patients were enrolled. One hundred and forty-two were aged 50 years or younger (the younger group), while 306 were above 50 years of age (the older group). The most common pre-existing conditions in the younger group were diabetes mellitus and hypertension, and 69.7% of the patients had a body mass index (BMI) > 25 kg/m². Of 142 younger patients, 31 of 142 patients (21.8%, 19 women) did not have these pre-existing conditions. The overall case fatality rate among severity cases was 21.0%, and it differed according to age: 5.6% (n = 8/142) in the younger group, 28.1% in the older group, and 38% in the ≥ 65 years group. Age (odds ratio [OR], 7.902; 95% confidence interval [CI], 2.754-18.181), mechanical ventilation therapy (OR, 17.233; 95% CI, 8.439-35.192), highest creatinine > 1.5 mg/dL (OR, 17.631; 95% CI, 8.321-37.357), and combined blood stream infection (OR, 7.092; 95% CI, 1.061-18.181) were identified as independent predictors of mortality in total patients. Similar patterns were observed in age-specific analyses, but most results were statistically insignificant in multivariate analysis due to the low number of deaths in the younger group. The full vaccination rate was very low among study population (13.6%), and only three patients were fully vaccinated, with none of the patients who died having been fully vaccinated in the younger group. Seven of eight patients who died had a pre-existing condition or were obese (BMI > 25 kg/m²), and the one remaining patient died from a secondary infection. CONCLUSION: About 22% of the patients in the young critical group did not have an underlying disease or obesity, but the rate of obesity (BMI > 25 kg/m²) was high, with a fatality rate of 5.6%. The full vaccination rate was extremely low compared to the general population of the same age group, showing that non-vaccination has a grave impact on the progression of COVID-19 to a critical condition. The findings of this study highlight the need for measures to prevent critical progression of COVID-19, such as vaccinations and targeting young adults especially having risk factors.

Sustained Responses of Neutralizing Antibodies Against Middle East Respiratory Syndrome Coronavirus (MERS-CoV) in Recovered Patients and Their Therapeutic Applicability.

BACKGROUND: Zoonotic coronaviruses have emerged as a global threat by causing fatal respiratory infections. Given the lack of specific antiviral therapies, application of human convalescent plasma retaining neutralizing activity could be a viable therapeutic option that can bridges this gap. METHODS: We traced antibody responses and memory B cells in peripheral blood collected from 70 recovered Middle East respiratory syndrome coronavirus (MERS-CoV) patients for 3 years after the 2015 outbreak in South Korea. We also used a mouse infection model to examine whether the neutralizing activity of collected sera could provide therapeutic benefit in vivo upon lethal MERS-CoV challenge. RESULTS: Anti-spike-specific IgG responses, including neutralizing activity and antibody-secreting memory B cells, persisted for up to 3 years, especially in MERS patients who suffered from severe pneumonia. Mean antibody titers gradually decreased annually by less than 2-fold. Levels of antibody responses were significantly correlated with fever duration, viral shedding periods, and maximum viral loads observed during infection periods. In a transgenic mice model challenged with lethal doses of MERS-CoV, a significant reduction in viral loads and enhanced survival was observed when therapeutically treated with human plasma retaining a high neutralizing titer (> 1/5000). However, this failed to reduce pulmonary pathogenesis, as revealed by pathological changes in lungs and initial weight loss. CONCLUSIONS: High titers of neutralizing activity are required for suppressive effect on the viral replication but may not be sufficient to reduce inflammatory lesions upon fatal infection. Therefore, immune sera with high neutralizing activity must be carefully selected for plasma therapy of zoonotic coronavirus infection.

Longevity of seropositivity and neutralizing antibodies in recovered MERS patients: a 5-year follow-up study.

OBJECTIVES: We aimed to assess the longevity of spike-specific antibody responses and neutralizing activity in the plasma of recovered Middle East respiratory syndrome (MERS) patients. METHODS: We traced the antibody responses and neutralizing activity against MERS coronavirus (MERS-CoV) in peripheral blood samples collected from 70 recovered MERS patients for 5 years after the 2015 MERS outbreak in South Korea. We also measured the half-life of neutralizing antibody titres in the longitudinal specimens. RESULTS: The seropositivity rate persisted for up to 4 years (50.7-56.1%), especially in MERS patients who suffered from severe pneumonia, and then decreased (35.9%) in the fifth year. Although the spike-specific antibody responses decreased gradually, the neutralizing antibody titres decreased more rapidly (half-life: 20 months) in 19 participants without showing negative seroconversion during the study period. Only five (26.3%) participants had neutralizing antibody titres greater than 1/1000 of PRNT50, and a high neutralizing antibody titre over 1/5000 was not detected in the participants at five years after infection. DISCUSSION: The seropositivity rate of the recovered MERS patients persisted up to 4 years after infection and significantly dropped in the fifth year, whereas the neutralizing antibody titres against MERS-CoV decreased more rapidly and were significantly reduced at 4 years after infection.

Viral kinetics of SARS-CoV-2 over the preclinical, clinical, and postclinical period.

BACKGROUND: It is necessary to know the viral kinetics and conduct epidemiological investigations of confirmers to prevent the spread of the new infectious disease COVID-19 to the community. To date, no study has been published on viral kinetics during the preclinical and clinical periods of SARS-CoV-2. METHODS: A confirmed case was defined as a patient with positive results by real-time reverse transcription polymerase chain reaction (RT-PCR) assay for SARS-CoV-2. Both specimen types were collected over the whole clinical course in all patients. Asymptomatic patients who had been screened for COVID-19 due to a strong epidemiological link were also enrolled. The study population included 54 hospitalized patients with confirmed COVID-19. RESULTS: COVID-19 shows a very high viral load on the day of symptom development, which then decreases overall. Rapid viral proliferation was observed 0-5 days before symptoms developed. Cycle threshold (Ct) value was the lowest in the clinical course from 5 days before symptoms to 10 days after symptoms occurred (Ct < 30). The rRT-PCR results were negative approximately 3 weeks after the onset of symptoms. However, there was a continuous pattern that was negative and positive for up to 6 weeks and more. CONCLUSION: Considering the characteristic that COVID-19 has a high viral load before symptoms appear, it is necessary to consider to expand the scope of epidemiological investigations. As there is a very low possibility of transmission after 10 days of symptom occurrence, it may be considered to release isolation after 10 days of symptom occurrence in limited resource situations. This study allows for the planning of epidemiological investigations, patient's ward supply, and follow-up of patients through sequential changes in viral loads over the entire clinical course. In addition, it is possible to estimate the clinical time at which the patient is present.

Risk Factors for Mortality and Respiratory Support in Elderly Patients Hospitalized with COVID-19 in Korea.

BACKGROUND: The mortality risk of coronavirus disease 2019 (COVID-19) is higher in patients with older age, and many elderly patients are reported to require advanced respiratory support. METHODS: We reviewed medical records of 98 patients aged ≥ 65 years who were hospitalized with COVID-19 during a regional outbreak in Daegu/Gyeongsangbuk-do province of Korea. The outcome measures were in-hospital mortality and the treatment with mechanical ventilation (MV) or high-flow nasal cannula (HFNC). RESULTS: The median age of the patients was 72 years; 55.1% were female. Most (74.5%) had at least one underlying condition. Overall case fatality rate (CFR) was 20.4%, and median time to death after admission was 8 days. The CFR was 6.1% among patients aged 65-69 years, 22.7% among those aged 70-79 years, and 38.1% among those aged ≥ 80 years. The CFR among patients who required MV was 43.8%, and the proportion of patients received MV/HFNC was 28.6%. Nosocomial acquisition, diabetes, chronic lung diseases, and chronic neurologic diseases were significant risk factors for both death and MV/HFNC. Hypotension, hypoxia, and altered mental status on admission were also associated with poor outcome. CRP > 8.0 mg/dL was strongly associated with MV/HFNC (odds ratio, 26.31; 95% confidence interval, 7.78-88.92; P < 0.001), and showed better diagnostic characteristics compared to commonly used clinical scores. CONCLUSION: Patients aged ≥ 80 years had a high risk of requiring MV/HFNC, and mortality among those severe patients was very high. Severe initial presentation and laboratory abnormalities, especially high CRP, were identified as risk factors for mortality and severe hospital course.

Three cases of treatment with nafamostat in elderly patients with COVID-19 pneumonia who need oxygen therapy.

No effective treatment for COVID-19 has been well established yet. Nafamostat, known as anticoagulant, has potential anti-inflammatory and anti-viral activities against COVID-19. We report three cases of COVID-19 pneumonia who progressed while using antiviral drugs and needed supplementary oxygen therapy, improved after treatment with nafamostat. These preliminary findings show the possibility that Nafamostat can be considered to be used in elderly patients with COVID-19 pneumonia who need oxygen therapy. The effectiveness of nafamostat should be evaluated in further studies.