Paula Andrea Velilla

Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infection significantly affects innate immune responses, particularly those of natural killer (NK) cells, which play an important role in antiviral defence. This review combines phenotypic, functional, and transcriptomic findings to explain the disruption of NK cell subsets in COVID‐19. Flow cytometry studies have shown generalised lymphopenia and a significant reduction in the CD56bright and CD56 ^dim CD16 ⁺ subsets. This change is linked to an increase in the CD56 ^dim CD16 ⁻ and CD56 ⁻ CD16 ⁺ populations, which correlate with disease severity. At the molecular level, there is an imbalance between activating and inhibitory receptors. This includes increases in NKG2A, PD‐1, and LAG‐3, along with decreases in NKp30, NKp46, and NKG2D. These findings are consistent with an exhausted phenotype and weakened cytotoxicity. Single‐cell RNA sequencing (scRNA‐seq) studies have identified an increase in proliferative, cytotoxic, and platelet‐associated CD56 ^dim NK subpopulations in severe cases and a reduction of CD56 ^bright cells. Transcriptomic profiling showed that upregulation of interferon‐stimulated genes (ISGs) and inflammatory pathways driven by STAT1/3, NF‐κB activation, and transforming growth factor‐beta (TGF‐β) signalling suppresses NK effector functions. Collectively, these findings suggest a model in which progressive NK cell dysfunction may be associated with the immunopathogenesis of COVID‐19. The integration of multi‐omic and phenotypic approaches provides a comprehensive view of NK cell responses to SARS‐CoV‐2 and suggests potential biomarkers and therapeutic targets to restore NK cell antiviral activity.

Background: The COVID-19 pandemic remains a global health problem. As in other viral infections, the humoral immune response against SARS-CoV-2 is thought to be crucial for controlling the infection. However, the dynamic of B cells in the clinical spectrum of this disease is still controversial. This study aimed to characterize B cell subsets and neutralizing responses in COVID-19 patients according to disease severity through a one-month follow-up.Methods: A cohort of 71 individuals with SARS-CoV-2 infection confirmed by RT-PCR were recruited and classified into four groups: i) asymptomatic; ii) symptomatic outpatients; iii) hospitalized in ward, and iv) intensive care unit patients (ICU). Samples were taken at days 0 (inclusion to the study), 7 and 30. B cell subsets and neutralizing antibodies were assessed using multiparametric flow cytometry and plaque reduction neutralization, respectively.Results: Older age, male gender and body mass index over 25 were common factors among hospitalized and ICU patients, compared to those with milder clinical presentations. In addition, those requiring hospitalization had more comorbidities. A significant increase in the frequencies of CD19⁺ cells at day 0 was observed in hospitalized and ICU patients compared to asymptomatic and symptomatic groups. Likewise, the frequency of plasmablasts was significantly increased at the first sample in the ICU group compared to the asymptomatic group, but then waned over time. The frequency of naïve B cells decreased at days 7 and 30 compared to day 0 in hospitalized and ICU patients. The neutralizing antibody titers were higher as the severity of COVID-19 increased; in asymptomatic individuals, it was strongly correlated with the percentage of IgM⁺ switched memory B cells, and a moderate correlation was found with plasmablasts.Conclusion: The humoral immune response is variable among SARS-CoV-2 infected people depending on the severity and time of clinical evolution. In severe COVID-19 patients, a higher plasmablast frequency and neutralizing antibody response were observed, suggesting that, despite having a robust humoral immunity, this response could be late, having a low impact on disease outcome.

CD8⁺ T-cells play a crucial role in the control of HIV replication. HIV-specific CD8⁺ T-cell responses rapidly expand since the acute phase of the infection, and it has been observed that HIV controllers harbor CD8⁺ T-cells with potent anti-HIV capacity. The development of CD8⁺ T-cell-based vaccine against HIV-1 has focused on searching for immunodominant epitopes. However, the strong immune pressure of CD8⁺ T-cells causes the selection of viral variants with mutations in immunodominant epitopes. Since HIV-1 mutations are selected under the context of a specific HLA-I, the circulation of viral variants with these mutations is highly predictable based on the most prevalent HLA-I within a population. We previously demonstrated the adaptation of circulating strains of HIV-1 to the HLA-A*02 molecule by identifying mutations under positive selection located in GC9 and SL9 epitopes derived from the Gag protein. Also, we used an in silico prediction approach and evaluated whether the mutations found had a higher or lower affinity to the HLA-A*02. Although this strategy allowed predicting the interaction between mutated peptides and HLA-I, the functional response of CD8⁺ T-cells that these peptides induce is unknown. In the present work, peripheral blood mononuclear cells from 12 HIV-1⁺ HLA-A*02:01⁺ individuals were stimulated with the mutated and wild-type peptides derived from the GC9 and SL9 epitopes. The functional profile of CD8⁺ T-cells was evaluated using flow cytometry, and the frequency of subpopulations was determined according to their number of functions and the polyfunctionality index. The results suggest that the quality of the response (polyfunctionality) could be associated with the binding affinity of the peptide to the HLA molecule, and the functional profile of specific CD8⁺ T-cells to mutated epitopes in individuals under cART is maintained.

Introduction: Immunological markers have been described during COVID-19 and persist after recovery. These immune markers are associated with clinical features among SARSCoV-2 infected individuals. Nevertheless, studies reporting a comprehensive analysis of the immune changes occurring during SARS-CoV-2 infection are still limited.Objective: To evaluate the production of proinflammatory cytokines, the antibody response, and the phenotype and function of NK cells and T cells in a Colombian family cluster with SARS-CoV-2 infection.Materials and methods: Proinflammatory cytokines were evaluated by RT-PCR and ELISA. The frequency, phenotype, and function of NK cells (cocultures with K562 cells) and T-cells (stimulated with spike/RdRp peptides) were assessed by flow cytometry. Anti-SARS-CoV-2 antibodies were determined using indirect immunofluorescence and plaque reduction neutralization assay.Results: During COVID-19, we observed a high proinflammatory-cytokine production and a reduced CD56bright-NK cell and cytotoxic response. Compared with healthy controls, infected individuals had a higher frequency of dysfunctional CD8+ T cells CD38+HLA-DR-. During the acute phase, CD8+ T cells stimulated with viral peptides exhibited a monofunctional response characterized by high IL-10 production. However, during recovery, we observed a bifunctional response characterized by the co-expression of CD107a and granzyme B or perforin.Conclusion: Although the proinflammatory response is a hallmark of SARS-CoV-2 infection, other phenotypic and functional alterations in NK cells and CD8+ T cells couldbe associated with the outcome of COVID-19. However, additional studies are required to understand these alterations and to guide future immunotherapy strategies.

The global emergency arising from the rapid spread of the severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) virus, the etiological agent responsible for coronavirus disease 2019 (Covid-19), has resulted in a significant loss of more than 2.5 million human lives across the world until now. On March 12, 2020, Colombia's authorities declared a state of emergency due to Covid-19, and, by March 25, 2021, have reported 2,359,942 cases and 62,519 deaths attributed to the infection (https://www.ins.gov.co). Following the recommendation of the World Health Organization (WHO), just a year ago, Colombia's national government adopted mandatory preventive isolation to reduce new cases of Covid-19. However, despite implementing an early lockdown and having a 97,78% health coverage by the end of 2020, there is still great concern about the quality of care to respond effectively to the needs of infected patients, considering the 29% of accumulated excess of total mortality in 2020, compared with the national historical average.[1] Besides the direct impact of the novel disease on individual health, the Covid-19 crisis has had significant consequences on the economic growth of the affected populations. Although the non-pharmaceutical interventions applied in most countries, including Colombia, to control the viral transmission and prevent the collapse of health care services, such as lockdowns, isolation, social distancing, and quarantine measures, have shown to be beneficial, they prompted a decline in productivity with a subsequent economic downturn, representing a significant challenge in some vulnerable countries with less developed health systems and lacking the financial ability to respond to the pandemic.[2] Economic and social changes triggered by the widespread community transmission of the SARS-CoV-2 infection also negatively affect the population who wants to get pregnant, influencing fertility and birth rates. The changes imposed by the pandemic not only affected the prenatal control program in Colombia, but also altered the mental state, intimacy, relationship dynamics, and reproductive desires in various ways worldwide. For instance, many Italian couples trying to conceive abandoned their intention to do so, precisely due to concerns of further economic difficulties and the repercussions on gestation.[3] Moreover, it has been reported that physiological changes during pregnancy may impact on the outcomes of mothers and newborns with Covid-19,[4] increasing the perception of pregnancy as a threat on the part of couples attempting conception. Collected statistics of existing research on sexual health during the pandemic closely relate to such remarks. Studies[5] report a significant decrease in sexual activity, probably due to the major changes at the beginning of the epidemic plus the perceived high risk of sexual practices. Altogether, current evidence thus raises awareness about the impairment in sexual and reproductive health and its forthcoming impact on the demographic composition of the affected nations. An analysis using information from the Colombian National Administrative Department of Statistics (DANE, https://www.dane.gov.co/) regarding reports on births in Colombia from 2014 to 2020 was recorded for this letter. The data from 2014 to 2019 was consolidated and compared with the data reported for 2020. Birth records for 2020 (preliminary report) were also compared with the average of the last 6 years (2014 to 2019) by yearly range ([Fig. 1]). The number of live births in Colombia during the last 6 years (2014 to 2019) is broadly stable ([Fig. 1a]). However, there is a notable reduction of 5.32% in total births in 2020 compared with the mean national value for the past 6 years. When comparing the national average of the previous 6 years with 2020 ranges per age ([Fig. 1b]), we also observed a decline in births in most age groups, with the highest decrease in women aged 10 to 14. Although throughout the first 3 quarters of 2020 the number of births remained stable and comparable to that of previous years, it was in the last quarter of 2020 that births started to decline progressively, not redressing the rise in the mortality rate and the fatality rate of Covid-19. A similar situation occurs in France, Spain, and the United States, where there are important drops in births, contrary to the expected baby boom at this pandemic stage, based on prior epidemiological predictions. The decrease in total births in Colombia in 2020, compared with average birth rates, has several implications. First, the social measures aimed to flatten the Covid-19 curve and lessen the economic impact are probably the main cause behind the negative effect on the fertility rate, both in high- and lower-to-middle-income economies. Notably, the economic crisis and employment uncertainty derived from policies against the spread of the virus might be the most significant circumstances accountable for such a decline, given their known influence in the reproductive decision-making as, in general, falling income has been associated to the postponement and abandonment of planned births, which may not be reversed regardless of improvements in economic indexes.[6] [7] After that, the fall in fertility and birth rates has implications on the demographic structure, and ultimately, on the age distribution of the population, having an aggregate effect on economic affluence.[8] The drop in the number of total births in 2020 in Colombia, will probably be followed by a gradual and modest increase in fertility rates in subsequent years, once the social and economic turbulence is over, in a pattern similar to how most epidemics affect demographyics.[9] As for now, even when vaccine efforts are being successful, the economic fallout will plausibly continue; hence, it is unlikely that the declining fertility trends alleviate in the short term, notwithstanding an apparent economic recovery. Furthermore, it is...

Background: : The diversity of the HIV proteome influences the cellular response and development of an effective vaccine, particularly due to the generation of viral variants with mutations located within CD8+ T-cell epitopes. These mutations can affect the recognition of the epitopes, that may result in the selection of HIV variants with mutated epitopes (autologous epitopes) and different CD8+ T-cell functional profiles.Objective:: To determine the phenotype and functionality of CD8+ T-cell from HIV-infected Colombian patients in response to autologous and consensus peptides derived from HIV-1 clade B protease and reverse transcriptase (RT).Methods:: By flow cytometry, we compared the ex vivo CD8+ T-cell responses from HIV-infected patients to autologous and consensus peptides derived from HIV-1 clade B protease and RT, restricted by HLA-B*35, HLA-B*44 and HLA-B*51 alleles.Results:: Although autologous peptides restricted by HLA-B*35 and HLA-B*44 did not show any differences compared with consensus peptides, we observed the induction of a higher polyfunctional profile of CD8+ T-cells by autologous peptides restricted by HLA-B*51, particularly by the production of interferon-γ and macrophage inflammatory protein-1β. The response by different memory CD8+ T-cell populations was comparable between autologous vs. consensus peptides. In addition, the magnitude of the polyfunctional response induced by the HLA-B*51-restricted QRPLVTIRI autologous epitope correlated with low viremia.Conclusion:: Autologous peptides should be considered for the evaluation of HIV-specific CD8+ Tcell responses and to reveal some relevant epitopes that could be useful for therapeutic strategies aiming to promote polyfunctional CD8+ T-cell responses in a specific population of HIV-infected patients.