Longitudinal evaluation of SARS-CoV-2 T cell immunity over 2 years following vaccination and infection.

BACKGROUND: Within a year of the SARS-CoV-2 pandemic, vaccines inducing a robust humoral and cellular immune response were implemented worldwide. However, emergence of novel variants and waning vaccine induced immunity led to implementation of additional vaccine boosters. METHODS: This prospective study evaluated the temporal profile of cellular and serological responses in a cohort of 639 SARS-CoV-2 vaccinated participants, of whom a large proportion experienced a SARS-CoV-2 infection. All participants were infection naïve at the time of their first vaccine dose. Proportions of SARS-CoV-2 Spike-specific T cells were determined after each vaccine dose using the Activation Induced Markers (AIM) assay, while levels of circulating SARS-CoV-2 antibodies were determined by the Meso Scale serology assay. RESULTS: We found a significant increase in SARS-CoV-2 Spike-specific CD4+ and CD8+ T cell responses following the third dose of a SARS-CoV-2 mRNA vaccine as well as enhanced CD8+ T cell responses after the fourth dose. Further, increased age was associated with a poorer response. Finally, we observed that SARS-CoV-2 infection boosts both the cellular and humoral immune response, relative to vaccine-induced immunity alone. CONCLUSION: Our findings highlight the boosting effect on T cell immunity of repeated vaccine administration. The combination of multiple vaccine doses and SARS-CoV-2 infections maintains population T cell immunity although with reduced levels in the elderly.

Efficacy of rifampicin combination therapy against MRSA prosthetic vascular graft infections in a rat model.

Staphylococcus aureus is a major cause of prosthetic vascular graft or endograft infections (VGEIs) and the optimal choice of antibiotics is unclear. We investigated various antibiotic choices as either monotherapy or combination therapy with rifampicin against MRSA in vitro and in vivo. Fosfomycin, daptomycin and vancomycin alone or in combination with rifampicin was used against MRSA USA300 FPR3757. Each antibiotic was tested for synergism or antagonism with rifampicin in vitro, and all antibiotic regimens were tested against actively growing bacteria in media and non-growing bacteria in buffer, both as planktonic cells and in biofilms. A rat model of VGEI was used to quantify the therapeutic efficacy of antibiotics in vivo by measuring bacterial load on grafts and in spleen, liver and kidneys. In vitro, rifampicin combinations did not reveal any synergism or antagonism in relation to growth inhibition. However, quantification of bactericidal activity revealed a strong antagonistic effect, both on biofilms and planktonic cells. This effect was only observed when treating active bacteria, as all antibiotics had little or no effect on inactive cells. Only daptomycin showed some biocidal activity against inactive cells. In vivo evaluation of therapy against VGEI contrasted the in vitro results. Rifampicin significantly increased the efficacy of both daptomycin and vancomycin. The combination of daptomycin and rifampicin was by far the most effective, curing 8 of 13 infected animals. Our study demonstrates that daptomycin in combination with rifampicin shows promising potential against VGEI caused by MRSA. Furthermore, we show how in vitro evaluation of antibiotic combinations in laboratory media does not predict their therapeutic effect against VGEI in vivo, presumably due to a difference in the metabolic state of the bacteria.

A high-throughput assay identifies molecules with antimicrobial activity against persister cells.

Introduction. Persister cells are transiently non-growing antibiotic-tolerant bacteria that cause infection relapse, and there is no effective antibiotic therapy to tackle these infections.Gap statement. High-throughput assays in drug discovery are biased towards detecting drugs that inhibit bacterial growth rather than killing non-growing bacteria. A new and simple assay to discover such drugs is needed.Aim. This study aims to develop a simple and high-throughput assay to identify compounds with antimicrobial activity against persister cells and use it to identify molecular motifs with such activity.Methodology. We quantified Staphylococcus aureus persister cells by enumeration of colony forming units after 24 h ciprofloxacin treatment. We first quantified how the cell concentration, antibiotic concentration, growth phase and presence/absence of nutrients during antibiotic exposure affected the fraction of persister cells in a population. After optimizing these parameters, we screened the antimicrobial activity of compound fragments to identify molecular structures that have activity against persister cells.Results. Exponential- and stationary-phase cultures transferred to nutrient-rich media displayed a bi-phasic time-kill curve and contained 0.001-0.07% persister cells. A short rifampicin treatment resulted in 100% persister cells for 7 h, after which cells resumed activity and became susceptible. Stationary-phase cultures displayed a low but constant death rate but ultimately resulted in similarly low survival rates as the exponential-phase cultures after 24 h ciprofloxacin treatment. The persister phenotype was only maintained in most of the population for 24 h if cells were transferred to a carbon-free minimal medium before exposure to ciprofloxacin. Keeping cells starved enabled the generation of high concentrations of S. aureus cells that tolerate 50× MIC ciprofloxacin, and we used this protocol for rapid screening for biocidal antibiotics. We identified seven compounds from four structural clusters with activity against antibiotic-tolerant S. aureus. Two compounds were moderately cytotoxic, and the rest were highly cytotoxic.Conclusion. Transferring a stationary-phase culture to a carbon-free minimal medium for antimicrobial testing is a simple strategy for high-throughput screening for new antibiotics that kill persister cells. We identified molecule fragments with such activity, but further screening is needed to identify motifs with lower general cytotoxicity.

All-cause and AIDS-related mortality among people with HIV across Europe from 2001 to 2020: impact of antiretroviral therapy, tuberculosis and regional differences in a multicentre cohort study.

Background: All-cause and AIDS-mortality in Europe has been decreasing between 1996 and 2020. However, regional differences as well as their drivers remain unclear. This study investigates mortality differences and their drivers, including usage of and response to antiretroviral therapy (ART) and active tuberculosis (TB), among people with HIV across Europe. Methods: People with HIV enrolled in EuroSIDA were followed from 2001 through 2020. Immunologic-virologic status (IVS) was categorized as poor (CD4-cell count ≤350 cells/mm3 and viral load (VL) > 200 copies/ml), good (CD4 ≥ 500 and VL < 200), or intermediate (remaining combinations). Participants missing either CD4-cell count or VL were categorized as unknown. Regional differences in mortality were analyzed using multivariable Poisson regression with interaction analyses between regions of Europe and IVS, ART, or TB status. Findings: 20,364 people with HIV were included: 13,715/20,346 (67.3%) from Western, 3020/20,364 (14.8%) from Central Eastern, and 3629/20,364 (17.8%) from Eastern Europe. At enrolment, median age was 40 years (inter-quartile range (IQR): 33-48), median CD4-cell count 449 cells/mm3 (IQR: 291-638), and most were male 14,993/20,346 (73.3%). A total of 2639 died during 192,591 person-years of follow-up (crude mortality rate 13.7/1000 person-years, 95% CI: 13.2-14.2), 519/2639 (19.7%) from AIDS (2.7/1000 person-years, 2.5-2.9). All-cause and AIDS-mortality rates decreased over time but remained higher in Eastern Europe after adjusting for confounders. Being off ART (aIRR 2.42; 95% CI 2.14-2.74), poor IVS (aIRR 4.2; 95% CI 3.39-5.20) and prior TB (aIRR 3.33; 95% CI 2.75-4.03) were associated with higher all-cause mortality. For all-cause mortality the effect of ART (test for interaction: p < 0.001) and IVS (p = 0.02), but not TB (p = 0.5) varied across regions. Interpretation: Overall mortality and AIDS-mortality rates decreased over time, but remained higher in Eastern Europe. A poor IVS, being off ART and prior active TB were related to higher mortality. Eastern Europe had the highest proportion of people with poor or unknown IVS, emphasizing the continued need to improve HIV care with a focus on early diagnosis, ART initiation, and adherence. Funding: EuroSIDA has received funding from ViiV Healthcare LLC, Janssen Scientific Affairs, Janssen R&D, Bristol-Myers Squibb Company, Merck Sharp & Dohme Corp, Gilead Sciences and the European Union's Seventh Framework Programme for research, technological development and demonstration under EuroCoord grant agreement n˚ 260694. The study is also supported by a grant from the Danish National Research Foundation and by the International Cohort Consortium of Infectious Disease (RESPOND).

Development of antibody levels and subsequent decline in individuals with vaccine induced and hybrid immunity to SARS-CoV-2.

OBJECTIVES: This study aimed to compare antibody trajectories among individuals with SARS-CoV-2 hybrid and vaccine-induced immunity. METHODS: Danish adults receiving three doses of BTN162b2 or mRNA-1237 were included prior to first vaccination (Day 0). SARS-CoV-2 anti-spike IgG levels were assessed before each vaccine dose, at Day 90, Day 180, 28 days after 3rd vaccination (Day 251), Day 365, and prior to 4th vaccination (Day 535). SARS-CoV-2 PCR results were extracted from the national microbiology database. Mixed-effect multivariable linear regression investigated the impact of hybrid-immunity (stratified into 4 groups: no hybrid immunity, PCR+ prior to 3rd dose, PCR+ after 3rd dose and before Day 365, PCR+ after Day 365) on anti-spike IgG trajectories. RESULTS: A total of 4,936 individuals were included, 47% developed hybrid-immunity. Anti-spike IgG increases were observed in all groups at Day 251, with the highest levels in those PCR+ prior to 3rd dose (Geometric Mean; 535,647AU/mL vs. 374,665AU/mL with no hybrid-immunity, P<0.0001). Further increases were observed in participants who developed hybrid immunity after their 3rd dose. Anti-spike IgG levels declined from Day 251-535 in individuals without hybrid-immunity and in those who developed hybrid-immunity prior to their 3rd dose, with lower rate of decline in those with hybrid-immunity. CONCLUSION: Hybrid-immunity results in higher and more durable antibody trajectories in vaccinated individuals.