acute respiratory syndrome Archives - Amazing Health Advances

Mild COVID-19 Disease May Trigger Long-Term Immunity

AHA Publisher — Wed, 25 Nov 2020 08:00:49 +0000

Sally Robertson, B.Sc. via News-Medical Net – Researchers in the United States have conducted a study showing that individuals who have recovered from mild coronavirus disease 2019 (COVID-19) developed sustained protective immune memory against the causative agent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The team’s longitudinal analysis of recovered patients who had been mildly symptomatic found that these individuals had developed multifaceted SARS-CoV-2-specific immunological memory that was maintained for the duration of the study. As recently reported in the journal Cell, the participants developed SARS-CoV-2 specific immunoglobulin g (IgG) antibodies, neutralizing plasma, memory B cells, and memory T cells that persisted for at least three months. The team – from the University of Washington and Benaroya Research Institute in Seattle – also found that populations of virus-specific memory T and B cells expanded and exhibited protective antiviral functions. “Therefore, mild COVID-19 elicits memory lymphocytes that persist and display functional hallmarks of antiviral immunity,” said Marion Pepper (University of Washington School of Medicine) and colleagues. Establishing whether mild disease can induce persistent immune memory is vital Since the first cases of SARS-CoV-2 were identified in Wuhan, China, late last year (2019), the unprecedented spread of the COVID-19-pandemic has now led to 59.59 million cases of infection and caused more than 1.4 million deaths. The vast majority of infected individuals experience mildly symptomatic disease and do not require hospitalization. However, whether this mild disease can induce persistent immune memory that could protect against future reinfection and therefore reduce transmission is not yet known. “While a vaccine is needed to safely reach herd immunity against SARS-CoV-2, understanding if natural infection induces viral-specific immunological memory that could influence transmission and disease severity is critical to controlling this pandemic,” writes the team. The role the adaptive immune system plays in immune memory The adaptive immune system primarily mediates immunologic memory. Following viral infection, B cells and T cells bind to viral proteins, which triggers their expansion, differentiation, and secretion of effector molecules to combat the infection. Once the virus is cleared, most of these virus-specific effector cells die, but about 10% persists as memory cells that can produce a continuous supply of effector molecules. Strategically located dormant memory cells are also quickly reactivated in response to repeat infection and induce the same effector processes as those that occurred during the primary immune response. Following reinfection, pathogen-specific memory B cells (MBCs) differentiate into plasmablasts that secrete protective IgG antibodies. Reactivated memory T cells also proliferate, which can help to activate MBCs. In addition, the reactivated T cells secrete cytokines such as interferon-γ (IFN-γ) to stimulate the innate immune system and deliver cytolytic molecules that destroy infected cells. “These quantitatively and qualitatively enhanced virus-specific memory populations coordinate to quickly clear the virus, thereby preventing disease and reducing the chance of transmission,” said Pepper and colleagues. “It is therefore critical to assess the full cadre of SARS-CoV-2-specific immune memory responses to determine if mild infection induces a multilayered defense that lasts.” What did the researchers do? The team performed an analysis of SARS-CoV-2 specific immune responses at one month and three months following symptom onset among individuals who had recovered from mild COVID-19. The majority of participants developed SARS-CoV-2 -specific IgG antibodies, neutralizing antibodies, and memory B and T cells that persisted for at least three months. Three months following symptom onset, recovered individuals had formed an expanded arsenal of virus-specific memory cells that exhibited hallmarks of antiviral immunity. This included an increased population of pathogen-specific memory B cells (MBCs) that were capable of expressing neutralizing antibodies against the virus. “These data suggest that upon re-exposure to SARS-CoV-2, these individuals will have MBCs that can rapidly generate neutralizing SARS-CoV-2 antibody titers and help control the infection,” say the researchers. Memory T cells also secreted cytokines and this cell population expanded upon antigen re-encounter. The number of CXCR5-expressing circulating T follicular helper cells (which can influence B cell activation) increased, as did the number of CXCR3-expressing CD4+ T memory cells and IFN-γ-producing CD8+ T cells. What are the implications of the study? “Together, these data demonstrate that all of the recovered individuals in our cohort formed a multifaceted defense, which suggests attenuated virus vaccines are likely to be similarly successful in eliciting a functional immune memory response,” write Pepper and colleagues. The team says that while further studies are needed to determine how long memory to SARS-CoV-2 infection lasts, the findings suggest that mild COVID-19 induces persistent, multifaceted immune memory. “These functional antiviral memory lymphocytes are poised for a coordinated response to SARS-CoV-2 re-exposure that could contribute to immunity and help to curtail the pandemic,” concludes the team. Journal reference: Pepper M, et al. Functional SARS-CoV-2-specific immune memory persists after mild COVID-19. Cell, 2020. doi: https://doi.org/10.1016/j.cell.2020.11.029, https://www.cell.com/cell/fulltext/S0092-8674(20)31565-8 To read the original article click here.

The post Mild COVID-19 Disease May Trigger Long-Term Immunity appeared first on Amazing Health Advances.

COVID-19 Survivors May Have Protective Antibodies for 4 Months

AHA Publisher — Mon, 12 Oct 2020 07:00:52 +0000

Angela Betsaida B. Laguipo, BSN via News-Medical Net – A new study by researchers at Harvard Medical School and the Massachusetts General Hospital (MGH) aimed to determine how long severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immunity in COVID-19 survivors lasts. The researchers found that people who survive severe COVID-19 disease have long-lasting immune responses against SARS-CoV-2. The study, published in the journal Science Immunology, highlights the body’s immune response against COVID-19. Also, it offers hope that people who are infected with the SARS-CoV-2 virus will develop lasting protection against reinfection. The Study In the study, the researchers focused on the receptor-binding domain (RBD) of the virus “spike” protein, which binds to cells through the angiotensin-converting enzyme 2 (ACE2) receptors, leading to infection. The immune system generates proteins called antibodies when it senses that pathogens like the SARS-CoV-2 invade the body. Though the body produces an immune response, it is unclear how long these antibody responses last. To arrive at the study findings, the research team collected blood samples from 343 patients infected with SARS-CoV-2, most of whom had severe cases. These blood samples were obtained up to four months after the symptoms appeared. The researchers isolated the blood plasma and applied to laboratory plates coated with the RBD of the spike protein. They analyzed how different types of antibodies in the plasma attached to RBD. The study results were compared with blood samples collected from 1,548 people before the pandemic. The study findings showed that the immunoglobulin G (IgG) levels remained elevated in COVID-19 patients for four months and were tied to the presence of protective neutralizing antibodies, which exhibited a little reduction in activity over time. Hence, people are very likely to be protected for four months, which shows that key antibody responses to COVID-19 are present, the researchers concluded. IgG Level Measurements More Accurate Also, they found that measuring the IgG levels was more accurate in detecting people who had symptoms for at least 14 days. “These data suggest that RBD-targeted antibodies are excellent markers of previous and recent infection, that differential isotype measurements can help distinguish between recent and older infections, and those IgG responses persist over the first few months after infection and are highly correlated with neutralizing antibodies,” the researchers wrote in the paper. They added that since the standard test for SARS-CoV-2, the Polymerase chain reaction (PCR) nasal swab, loses sensitivity over time, supplementing it with an antibody test in patients who developed symptoms for at least eight days can aid in identifying some positive cases that may be missed. The team also added that people who were infected with the coronavirus had immunoglobulin A (IgA) and immunoglobulin M (IgM) responses that lasted for short periods decreasing to low levels in about two and a half months after infection. If patients tested positive for these antibodies, they might have been infected with COVID-19 in the past two months. Being aware of the duration of the body’s immune responses against SARS-CoV-2 by testing IgA and IgM levels will help provide more precise data about the spread of the infection. “There are a lot of infections in the community that we do not pick up through PCR testing during acute infection, and this is especially true in areas where access to testing is limited,” Jason Harris, a pediatric infectious disease specialist at MGH, explained. “Knowing how long antibody responses last is essential before we can use antibody testing to track the spread of COVID-19 and identify ‘hot spots’ of the disease,” he added. Of the more than 37.39 million cases of COVID-19 globally, more than 25.99 million have already recovered. Currently, numerous vaccines are being trialed to see if they are effective and safe to use by the general public. Having a better understanding of the body’s antibody responses to SARS-CoV-2 will also help scientists develop a vaccine that could offer protection against the raging virus. Sources: Harvard Medical School. (2020). https://news.harvard.edu/gazette/story/2020/10/covid-survivors-may-have-four-months-of-protection/ COVID-19 Dashboard by the Center for Systems Science and Engineering (CSSE) at Johns Hopkins University (JHU) – https://gisanddata.maps.arcgis.com/apps/opsdashboard/index.html#/bda7594740fd40299423467b48e9ecf6 To read the original article click here.

The post COVID-19 Survivors May Have Protective Antibodies for 4 Months appeared first on Amazing Health Advances.