Antibody correlates of protection from SARS-CoV-2 reinfection prior to vaccination: A nested case-control within the SIREN study

Subjects who developed SARS-CoV-2 specific IgM after vaccination show a longer humoral immunity and a lower frequency of infection

“…We found no such indication through the study, as only 1/33 NI subjects who had never become infected showed evidence of IgM-S presence at all the analysed time points after w0. In our study, therefore, protection does not appear to be mediated by the persistence of IgM-S but rather by the increased IgG-S response in subjects who elicited IgM-S. A recent study, in which higher levels of IgG-S were associated with a lower risk of infection, 20 supports this hypothesis.…”

“…Furthermore, it has been reported that the expansion of hCoV-specific IgG correlates negatively with the induction of SARS-CoV-2 specific IgG/IgM 25 and consequentially with protection against infection and hospitalizations. 20 Moreover, it was shown that if a second boost, in this case vaccination, recalls the primary antigen, this trigger will define future immune responses leading to the expansion of recalled IgG rather than antigen-specific IgG. 26 In accordance with these observations, in our study none of the subjects who had not developed IgM-S in response to vaccination showed evidence of IgM-S following the breakthrough infection, suggesting that the initial immunological imprinting after vaccination shaped the consequential response.…”

Shielding under endemic SARS-CoV-2 conditions is easier said than done: a model-based analysis

“…Where titer is the individual's neutralizing antibody titer normalized to peak convalescent level, h is the Hill coefficient, and EC 50,infection is the neutralizing antibody titer required for 50% protection from infection. EC 50,infection was assumed to be 35% of the peak convalescent plasma level because we found this to be approximately consistent with clinical data suggesting median protection from reinfection is 83% over 5 months after infection 83,84 . The exposure results in successful infection if a random value between 0 and 1 is less than p(infection | exposure).…”

Use of Hu-PBL Mice to Study Pathogenesis of Human-Restricted Viruses

“…Hu-PBL models have the advantage of faithfully mimicking the so-called patient memory immune response in the mouse. In particular, it was demonstrated that the hu-PBL/DC model enables the investigation of correlates of immunity in EVD survivors [ 43 ], which might be expanded to the investigation of other viral infections, such as infection with Rift Valley fever virus (RVFV) [ 116 ], SARS-CoV-2 infection and reinfection [ 117 , 118 , 119 , 120 , 121 , 122 , 123 , 124 , 125 , 126 ], or yellow fever virus (YFV) infection [ 127 ]. In this way, it is also possible to analyze the interactions that take place between the immune cells throughout the development of a specific disease given that they have been demonstrated to enable the sequential engraftment of distinct cell types [ 39 ].…”