No abstract

This review attempts to analyze the mechanism of action and immunity of class IIa bacteriocins. These peptides are promising alternative food preservatives and they have a great potential application in medical sciences. Class IIa bacteriocins act on the cytoplasmic membrane of Gram-positive cells dissipating the transmembrane electrical potential by forming pores. However, their toxicity and immunity mechanism remains elusive. Here we discuss the role of the mannose phosphotransferase system (man-PTS) as the receptor for class IIa bacteriocins and the influence of the membrane composition on the activity of these antimicrobial peptides. A model that is consistent with experimental results obtained by different researchers involves the non-specific binding of the bacteriocin to the negatively charged membrane of target bacteria. This step would facilitate a specific binding to the receptor protein, altering its functionality and forming an independent pore in which the bacteriocin is inserted in the membrane. An immunity protein could specifically recognize and block the pore. Bacteriocins function in bacterial ecosystems and energetic costs associated with their production are also discussed. Theoretical models based on solid experimental evidence are vital to understand bacteriocins mechanism of action and to promote new technological developments.

We hypothesized that in individuals with previous SARS-CoV-2 infection, the first vaccine dose would work as a booster, eliciting a faster and more intense immune response. We herein describe antibody responses to the first and second doses of Gam-COVID-Vac (SPUTNIK V) vaccine in health personnel of Tucuman, Argentina, with previous COVID-19 and compared it with uninfected personnel. Individuals with anti-SARS-CoV-2 titers at baseline showed significantly higher responses to the first dose than people with no prior history of disease (p <0.0001), with titers higher to those registered after the second dose in the control group, representing a clear secondary antibody response. This suggests that a single dose of SPUTNIK V for people with previous SARS-CoV-2 infection could contribute to a better use of available doses.

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has caused a global pandemic with dramatic health and socioeconomic consequences. The Coronavirus Disease 2019 (COVID-19) challenges health systems to quickly respond by developing new diagnostic strategies that contribute to identify infected individuals, monitor infections, perform contact-tracing, and limit the spread of the virus. In this brief report, we developed a highly sensitive, specific, and precise “In-House” ELISA to correctly discriminate previously SARS-CoV-2-infected and non-infected individuals and study population seroprevalence. Among 758 individuals evaluated for anti-SARS-CoV-2 serology in the province of Tucumán, Argentina, we found a weak correlation between antibodies elicited against the RBD, the receptor-binding domain of the Spike protein, and the nucleocapsid (N) antigens of this virus. Additionally, we detected mild levels of anti-RBD IgG antibodies in 33.6% of individuals diagnosed with COVID-19, while only 19% showed sufficient antibody titers to be considered as plasma donors. No differences in IgG anti-RBD titers were found between women and men, neither in between different age groups ranging from 18 to 60. Surprisingly, individuals from a high altitude village displayed elevated and longer lasting anti-RBD titers compared to those from a lower altitude city. To our knowledge, this is the first report correlating altitude with increased humoral immune response against SARS-CoV-2 infection.