Hepatitis C virus (HCV) infection is a worldwide public health problem. Chronic infection with HCV can lead to liver cirrhosis or cancer. Although some immune-competent individuals can clear the virus, others develop chronic HCV disease due to viral mutations or an impaired immune response. IFNs type I and III and the signal transduction induced by them are essential for a proper antiviral effect. Research on the viral cycle and immune escape mechanisms has formed the basis of therapeutic strategies to achieve a sustained virological response (SVR). The first therapies were based on IFNα; then, IFNα plus ribavirin (IFN–RBV); and then, pegylated-IFNα-RBV (PEGIFNα-RIV) to improve cytokine pharmacokinetics. However, the maximum SVR was 60%, and several significant side effects were observed, decreasing patients’ treatment adherence. The development of direct-acting antivirals (DAAs) significantly enhanced the SVR (>90%), and the compounds were able to inhibit HCV replication without significant side effects, even in paediatric populations. The management of coinfected HBV–HCV and HCV–HIV patients has also improved based on DAA and PEG-IFNα-RBV (HBV–HCV). CD4 cells are crucial for an effective antiviral response. The IFNλ3, IL28B, TNF-α, IL-10, TLR-3, and TLR-9 gene polymorphisms are involved in viral clearance, therapeutic responses, and hepatic pathologies. Future research should focus on searching for strategies to circumvent resistance-associated substitution (RAS) to DAAs, develop new therapeutic schemes for different medical conditions, including organ transplant, and develop vaccines for long-lasting cellular and humoral responses with cross-protection against different HCV genotypes. The goal is to minimise the probability of HCV infection, HCV chronicity and hepatic carcinoma.

Nutrition is essential in developing and maintaining a robust immune system and is vital for immune homeostasis. The pediatric population is particularly vulnerable to dietary changes, as their growth and development require a high energy intake. Malnutrition in infants can have immediate and long-lasting effects, increasing the risk of morbidity and mortality. Under and overnutrition can slow down the immune response to infections, which can delay recovery. To effectively defend against SARS-CoV-2 infection and enhance viral clearance, it is essential to maintain a healthy diet that includes sufficient macro and micronutrients. Several studies, most of which have been performed in adults, have shown that vitamins such as C, B12, folate, D, and E, as well as the minerals selenium, copper, iron, zinc, and magnesium, can help reduce the symptoms and duration of an infection. Supplementation with micronutrients has been shown to help with childhood malnutrition and can contribute to a more favorable clinical course of COVID-19. In children with obesity, it is also essential to monitor cardiometabolic and thrombotic risks, based on data from studies in adults. This review analyses the impact of the nutritional status of pediatric patients with SARS-CoV-2 infection, its contribution to clinical severity, and potential therapeutic interventions.

Dengue virus (DENV) causes the most prevalent arboviral infection worldwide. Alt-hough classically regarded as an acute illness, growing evidence describes Post-Dengue Syndrome (PDS) as a chronic entity with profound sequelae. This narrative review an-alyzes its pathophysiology: the cytokine storm, antibody-dependent enhancement, and NS1-triggered molecular mimicry, together with the cells that execute them—dendritic cells, mononuclear phagocytes, NK cells, platelets, and complement on the innate side; plasmablast expansion, follicular helper T cell activation, defective regulatory control, and PD-L1/PD-1-mediated exhaustion on the adaptive side. Genetic susceptibility is examined through polymorphisms of HLA, FcγRIIa, Toll-like receptor, and cytokine genes. Multisystemic manifestations are described—persistent fatigue, fibromyal-gia-like myalgia and arthralgia, alopecia, brain fog, and mood disturbance—alongside neurological complications, categorized into direct neuroinvasion and post-infectious immune-mediated damage such as Guillain-Barré syndrome and encephalomyelitis. Recent population-based data linking dengue to acute neurological events and to later cognitive decline are examined critically, as is the unsettled question of whether post-dengue neuroinflammation amounts to neurodegeneration. Finally, the influence of age and sex is addressed, and therapeutic and research priorities are outlined, of-fering an immunoclinical perspective for the multidisciplinary management of these patients.

Dengue virus (DENV) causes the most prevalent arboviral infection worldwide. Although classically regarded as an acute illness, growing evidence describes Post-Dengue Syndrome (PDS) as a chronic entity affecting a subset of patients, with pooled estimates placing post-infectious fatigue at 20.0% (95% CI 10–36) and no standardized case definition yet available. This narrative review analyzes its pathophysiology: the cytokine storm, antibody-dependent enhancement, and NS1-triggered molecular mimicry, together with the cells that execute them—dendritic cells, mononuclear phagocytes, NK cells, platelets, and complement on the innate side, and plasmablast expansion, follicular helper T cell activation, defective regulatory control, and PD-L1/PD-1-mediated exhaustion on the adaptive side. Almost all of these immunological mechanisms have been characterized during acute infection; few studies have sampled the same patients during convalescence, and even fewer have compared those who developed persistent symptoms with those who recovered. They are therefore established features of acute dengue and, at present, hypotheses about PDS rather than demonstrated features. Genetic susceptibility is examined through polymorphisms of HLA, FcγRIIa, Toll-like receptor, and cytokine genes. Multisystemic manifestations are described—persistent fatigue, fibromyalgia-like myalgia and arthralgia, alopecia, brain fog, and mood disturbance—alongside neurological complications, categorized into direct neuroinvasion and post-infectious immune-mediated damage such as Guillain–Barré syndrome and encephalomyelitis. Recent population-based data linking dengue to acute neurological events and to later cognitive decline are examined critically, as is the unsettled question of whether post-dengue neuroinflammation amounts to neurodegeneration. Finally, the authors address the influence of age and sex and outline therapeutic and research priorities, offering an immunoclinical perspective for the multidisciplinary management of these patients.

Hepatitis C virus (HCV) infection is a worldwide public health problem. Chronic infection by HCV can lead to liver cirrhosis or cancer. Although some immune-competent individuals can clear the virus, others develop chronic HCV disease due to viral mutations or an impaired immune response. IFNs type I and III and the signal transduction induced by them are essential for a proper antiviral effect. Research on the viral cycle and immune escape mechanisms have generated the basis of therapeutic strategies to achieve a sustained virological response (SVR). The first therapies were based on IFN-, then IFN-α plus ribavirin (IFN-RBV); then, pegylated-IFN--RBV (PEGIFNα-RIV) to improve cytokine pharmacokinetics. However, the maximum SVR was 60%, and several significant side effects were observed, decreasing the patients' treatment adherence. The development of direct-acting antivirals (DAAs) significantly enhanced SVR (> 90%); the compounds were able to inhibit HCV replication without significant side effects, even in pediatric populations. The management of coinfected patients HBV-HCV and HCV-HIV has also improved based on DAA and PEG-IFNα-RBV (HBV-HCV). CD4 cells are crucial for an effective antiviral response. IFNλ3, IL28B, TNF-α, IL-10, TLR-3, and TLR-9 gene polymorphisms are involved in viral clearance, therapeutic responses, and hepatic pathologies. Future research focuses on searching for strategies to circumvent resistance-associated substitution (RAS) to DAAs, develop new therapeutic schemes for different medical conditions, including organ transplant, and develop vaccines for long-lasting cellular and humoral responses with cross-protection to different HCV genotypes. The goal is to minimise the probability of HCV infection, HCV chronicity and hepatic carcinoma.

Background: Vaccines are crucial for preventing infectious diseases, as both humoral and cellular immune responses play a vital role in combating viral infections. The cellular immune response is crucial against SARS-CoV-2, particularly with the emergence of new variants that evade antibody neutralization. This study focuses on the immune memory response in individuals who have been vaccinated with the Sinopharm BBIBP-CorV vaccine. Methods: A cross-sectional study evaluated lymphocyte subpopulations using flow cytometry in 52 vaccinated adults (30 females) who had been exposed to SARS-CoV-2 or diagnosed with COVID-19. Conducted from February to June 2023 during the Omicron variant's circulation, the study assessed antigens: CD154 on CD4+ T cells, CD107 and CD314 on CD8+ T cells, CD314 in NK cells, and CD86 on CD19 B cells, after stimulation with viral peptides and an inactivated virus. Granzyme B and IFN-γ were quantified using ELISA. Results: The memory response, regardless of gender, age, or Body Mass Index (BMI), was mild but significant upon exposure to viral antigen or inactivated virus. An increase in the secretion of IFN-γ and granzyme B was also observed. Conclusions: It is suggested that the vaccine was able to generate a mild long-term memory against the SARS-CoV-2 virus in vaccinated adult individuals, independent of gender and BMI.