Peak Viral Load Research Articles

Prophylactic 2-week Glecaprevir/Pibrentasvir in Hepatitis C positive to negative kidney transplantation.

Hepatitis C virus (HCV) positive-to-negative kidney transplants (KT) require direct acting antiviral therapy, but the optimal timing and duration remain unclear. We hypothesized that 14-day prophylactic course of glecaprevir/pibrentasvir 300/120mg (GLE/PIB) would be safe and effective at treating donor-derived HCV viremia. This was a prospective, single-center, single-arm, open-label pilot study. 20 adult HCV negative recipients of HCV nucleic acid amplification test positive deceased-donor kidneys (HCV positive-to-negative) received a 14-day course of GLE/PIB, with the first dose pre-transplant. HCV RNA viral loads (VL) were monitored on post-operative days (POD) 1, 3, 7, and 13. If VL was undetectable on POD 13, GLE/PIB was stopped, and if detectable, GLE/PIB was continued to complete an 8-week course. Surveillance monitoring continued after treatment to ensure sustained viral response (SVR). The primary outcome was efficacy of 14-day prophylactic GLE/PIB. Secondary outcomes included patient and allograft survival, the incidence, timing, and clearance of HCV viremia, and safety events. 7/20 subjects (35%) never developed detectable HCV viremia. Only one subject had a detectable, but nonquantifiable, VL on POD 13 and completed an 8-week course. All subjects achieved SVR 12 weeks post-treatment with no relapses through 1-year follow-up. Mean time to undetectable HCV RNA VL was 10.5 (±4.7) days and mean peak VL was 371 (±715) copies/mL. 6-month and 1-year patient and allograft survival were 100% and 95%. A 14-day course of prophylactic GLE/PIB is safe and effective for HCV positive-to-negative KT and may prevent HCV transmission or significantly reduce the VL for those with detectable transmission allowing for rapid clearance within 2 weeks.

Impact of induction agents and maintenance immunosuppression on torque teno virus loads and year-one complications after kidney transplantation.

Torque teno virus load (TTVL) is gaining importance as a surrogate parameter to assess immunocompetence in kidney transplant recipients. Although the dynamics of TTVL have been investigated before, the impact of different induction agents and variations in immunosuppressive maintenance therapies on TTVL remain unknown. In this retrospective study, TTVL was quantified in 537 plasma or serum samples from 134 patients transplanted between 2018 and 2021. TTVL was examined pre-transplantation and 30-, 90-, 180-, and 360-days post-transplant. To assess the influence of induction therapy on TTVL, 67 patients receiving anti-thymocyte globulin (ATG) induction were matched with 67 patients receiving an interleukin-2 receptor antagonist (IL2-RA) induction in terms of age, sex, and donor modality. Following transplantation, there was a steep increase in TTVL post-transplant for all patients with peak viral loads at 90 days post-transplant (median TTVL [IQR] 7.97×106, [4.50×105-1.12×108]) followed by subsequently declining viral loads. Compared to patients receiving IL2-RA as induction therapy, patients receiving ATG had significantly higher peak viral loads 3 months post-transplant (median TTVL [IQR] 2.82×107 [3.93×106-1.30×108] vs. median TTVL [IQR] 2.40×106 [5.73×104-2.60×107]; P<0.001). Throughout all post-transplant time points, patients receiving additional rituximab for induction along with higher tacrolimus target levels exhibited the highest TTVL.Patients whose TTVL 3-months post-transplant exceeded the currently proposed cutoff to predict infections within the first year post-transplant [6.2 log10] showed a trend towards a higher risk of being hospitalized with an infection in the following 9 months, albeit without being statistically significant (HR=1.642, P=0.07). Higher TTVL reflects the greater immunosuppressive burden in immunological high-risk patients receiving intensive immunosuppression. The choice of induction agent and intensified immunosuppressive maintenance therapy notably affects TTVL at 3 months post-transplant and beyond, necessitating careful consideration when interpreting and applying TTVL cutoffs to monitor immunocompetence post-transplant.

Computation and analysis of optimal disturbances of periodic solution of the hepatitis B dynamics model

Abstract Optimal disturbances of the periodic solution of the hepatitis B dynamics model corresponding to the chronic recurrent form of the disease are found. The dependence of the optimal disturbance on the phase of periodic solution is analyzed. Four phases of the solution are considered, they correspond to clinically different periods of development of the immune response and severity of the disease, namely, activation of antiviral immune reactions, attenuation of reactions, peak and minimum viral load. The possibility of using optimal disturbances to exit the domain of attraction of the considered periodic solution using minimal impact is studied. The components of disturbances that may underlie the phenomenon of spontaneous recovery from chronic hepatitis B observed in clinical practice are identified.

Evaluation of CMV T-cell Mediated Immunity in Children with CMV DNAemia After Allogeneic Hematopoietic Cell Transplantation

Abstract Background Cytomegalovirus (CMV) is among the most common infectious complications following allogeneic hematopoietic cell transplantation (allo-HCT). A commercially available CMV T-cell immune panel (CMV-TCIP, Viracor®), reported as percentages of CMV-specific interferon gamma releasing CD4 and CD8 cells (%CMV-CD4 or %CMV-CD8 IFN-γ), may be used to assess CMV cell-mediated immunity (CMV-CMI). However, the utility of this assay among pediatric allo-HCT recipients remains unknown. Methods A retrospective analysis among pediatric allo-HCT recipients (age ≤18 years) from 1/2020 to 11/2023 who developed CMV DNAemia and had CMV-TCIP testing was performed. Per institutional protocol, weekly quantitative plasma CMV PCR was performed until day +100. Clinically significant CMV infection (csCMVi) was defined as CMV viral load (VL) ≥500IU/ml and pre-emptive therapy (PET) was provided for csCMVi. The most frequent indications for CMV-TCIP testing were to evaluate CMV-CMI to inform the need of CMV virus-specific T-cell therapy (CMV-VST) in the setting of resistant/refractory CMV, to monitor CMV-CMI as a proxy of VST expansion post CMV-VST, or to evaluate the need of ongoing secondary antiviral prophylaxis. A %CMV-CD4 or %CMV-CD8 IFN-γ ≤0.2% was categorized as a poor response, whereas a result &amp;gt;0.2% was classified as an adequate response. Specimens with insufficient quality, high background, or discrepant results from %CMV-CD4 or %CMV-CD8 were classified as a discordant response. Demographics, underlying condition, HCT type, conditioning regimen, antiviral agents and use of VST, VL, and CMV-TCIP results were recorded. Descriptive and nonparametric statistics (median, interquartile range [IQR]) were used for analysis. Results Twenty-seven CMV-TCIP results from 10 unique allo-HCT recipients were analyzed. The median age at transplant was 8.5 years (IQR 2.75-14.3), predominantly for hematologic malignancy (70%). CMV donor/recipient (D/R) serostatus were D+/R+ (60%), D-/R+ (30%) and D+/R- (10%). CMV DNAemia developed post-HCT in 80% (8/10) with median onset of 4 days post-HCT (IQR 3-40) and 2 subjects had known DNAemia prior to HCT. Nine (90%) subjects were started on PET for csCMVi, whereas 1 (10%) received antiviral therapy when VL was &amp;lt;500IU/ml. The first CMV-TCIP was obtained at median of 112 days (IQR 42-130) post-HCT. Despite appropriate antiviral therapy, patients with a peak VL ≥500 IU/mL (obtained within 1 week before and after CMV-TCIP testing) demonstrated significantly lower absolute CD4 (median 12 vs. 198 cells/uL, p=0.02) and CD8 (median 79 vs. 443 cells/uL, p=0.04) counts and %CMV-CD4 IFN-γ (0.04% vs. 0.36%, p=0.02) compared to those with a peak VL &amp;lt;500 IU/mL. Conclusion Our results suggest that CMV-CMI, particularly %CMV-CD4 IFN-γ &amp;gt;0.2%, was observed concurrently with downward trending VL, and may serve as a proxy of VST expansion in patients receiving CMV-VSTs. Figure 1A. The distribution of peak VLs over time based on %CMV-CD4 and %CMV-CD8 IFN-γ are demonstrated in Figure 1B. CMV peak VLs were lower with TCIP testing results reported as adequate combined responses compared to those with poor combined responses. In five subjects (50%) who received CMV-VSTs as part of CMV therapy, increased %CMV-CD4 and %CMV-CD8 IFN-γ were observed post-infusion with an observed downward trend in VL.

Viral load dynamics in asymptomatic and symptomatic patients during Omicron BA.2 outbreak in Shanghai, China, 2022: A longitudinal cohort study

The SARS-CoV-2 virus, particularly the Omicron BA.2 variant, led to a significant surge in Shanghai, 2022. However, the viral load dynamic in Omicron infections with varying clinical severities remain unclear. This prospective cohort included 48,830 hospitalized coronavirus disease 2019 (COVID-19) patients across three hospitals in Shanghai, China, between 23 March and 15 May, 2022. Systematic nucleic acid testing was performed using RT-PCR Cycle threshold (Ct) value as a proxy of viral load. We analyzed the kinetic characteristics of viral shedding by clinical severity and identified associated risk factors. The study comprised 31.06% asymptomatic cases, 67.66% mild-moderate cases, 1.00% severe cases, 0.29% critical and fatal cases. Upon admission, 57% of patients tested positive, with peak viral load observed at 4 days (median Ct value 27.5), followed by a decrease and an average viral shedding time (VST) of 6.1 days (Interquartile range, 4.0–8.8 days). Although viral load exhibited variation by age and clinical severity, peak Ct values occurred at similar times. Unvaccinated status, age exceeding 60, and comorbidities including hypertension, renal issues kidney dialysis and kidney transplantation, neurological disorders, rheumatism, and psychotic conditions were found to correlate with elevated peak viral load and extended VST. Asymptomatic cases demonstrated a 40% likelihood of contagiousness within 6 days of detection, while mild-moderate and severe cases exhibited post-symptom resolution infectious probabilities of 27% and over 50%, respectively. These findings revealed that the initial Ct values serve as a predictive indicator of severe outcomes. Unvaccinated elderly individuals with particular comorbidities are at high-risk for elevated viral load and prolonged VST.

Highly Heterogeneous Kaposi Sarcoma-Associated Herpesvirus Oral Shedding Kinetics Among People With and Without Kaposi Sarcoma and Human Immunodeficiency Virus Coinfection.

An improved understanding of oral Kaposi sarcoma-associated herpesvirus (KSHV) viral dynamics could provide insights into transmission risk and guide vaccine development. We evaluated KSHV oral shedding dynamics in Ugandan adults stratified by Kaposi sarcoma (KS) and human immunodeficiency virus (HIV) status. Participants were followed for ≥4 weeks, with daily home oral swab collection to quantify KSHV using polymerase chain reaction. Shedding rates were defined by number of days with KSHV DNA detected divided by total days with swabs and compared by group using hurdle models. Two hundred ninety-five participants were enrolled; median age was 35 years (range, 18-71 years), and 134 (45%) were male. KSHV was detected more frequently among participants with KS (HIV positive [HIV+]/KS+, 56/76 [74%]; HIV negative [HIV-]/KS+, 9/18 [50%]) than those without KS (HIV+/KS-, 36/125 [29%]; HIV-/KS-, 16/76 [21%]); odds of shedding did not differ significantly by HIV status. Among participants with KSHV detected, shedding rates did not differ significantly by group. Median per-participant viral loads among positive samples were lowest in HIV+/KS+ (3.1 log10 copies/mL) and HIV-/KS+ (3.3 log10 copies/mL) participants relative to HIV+/KS- (3.8 log10 copies/mL) and HIV-/KS- (4.0 log10 copies/mL) participants. All groups had participants with low viral load intermittent shedding and participants with high viral load persistent shedding. Within each group, individual KSHV shedding rate positively correlated with median KSHV log10 copies/mL, and episode duration positively correlated with peak viral load. Oral KSHV shedding is highly heterogeneous across Ugandan adults with and without KS and HIV. Persistent shedding is associated with higher median viral loads regardless of HIV and KS status.

Influence of stocking density and interaction variability on disease progression of white spot syndrome virus-infected shrimp under different risk scenarios

White spot syndrome virus (WSSV), the causative agent of white spot disease (WSD), is the most significant viral pathogen affecting farmed shrimp. As the culture model for whiteleg shrimp has evolved into a higher-intensity model, the need to study the influence of stocking density on disease progression in pond culture systems has been reinforced. Therefore, we assessed WSD progression by deriving a direct correlation between seasonal disease outbreak risk, stocking density, and viral shedding rate (WSSV genome copies/L/g) using three different stocking densities: high (210 shrimp/m2), medium (140 shrimp/m2), and low (70 shrimp/m2). In Experiment 1 (three stocking densities at 25 °C) and Experiment 2 (stocking density × temperature conditions), shrimp showed relatively high cumulative mortality within the temperature range of optimal WSSV replication (23–29 °C). Notably, the mortality trend, peak viral loads, and viral shedding of WSSV-infected shrimp occurred earlier under high-density conditions, regardless of temperature. Thereafter, this study established WSD risk scenarios based on water temperature conditions and confirmed a significant difference in mortality trends between vulnerable and less vulnerable water temperature scenarios under high- and low-density conditions. The vulnerable water temperature scenario included constant (25 °C), shifting-up (20 °C to 30 °C), and shifting-down (30 °C to 20 °C) conditions, whereas the less vulnerable water temperature scenario included constant 20 °C and 30 °C conditions. Based on mortality trends, the WSD risk scenarios revealed that the times to 50 % mortality for shrimp at high, medium, and low densities were 4, 5, and 6 days post-infection (dpi) in the vulnerable water temperature scenario, and 6, 7, and 9 dpi in the less vulnerable water temperature scenario. Viral shedding variability was evaluated based on the correlation between viral loads and viral shedding rate, and linear regression analysis revealed a significant positive correlation between viral shedding rates and viral loads in shrimp, regardless of WSD risk scenarios or stocking density conditions. Notably, a relatively enhanced viral shedding rate was observed at higher stocking densities (from low- to high-density conditions) and under vulnerable water temperature scenarios. This study suggests that increased stocking density and vulnerable water temperature scenarios could induce greater interactions among WSSV-infected shrimp. It also confirmed the potential role of risk scenarios, stocking density, and viral shedding in WSD progression, providing insights into the disease outbreak mechanisms on shrimp farms.

Cytomegalovirus viral load at initiation of pre-emptive antiviral therapy impacts cytomegalovirus dynamics in pediatric allogeneic hematopoietic cell transplantation recipients.

Cytomegalovirus (CMV) contributes to morbidity and mortality in allogeneic hematopoietic cell transplantation (allo-HCT) recipients. Pre-emptive antiviral therapy (PET) reduces the incidence of CMV end-organ disease (EOD), though relevant viral thresholds to initiate PET remain undefined. We evaluated the impact of viral loads (VLs) at PET initiation on virologic and clinical outcomes following pediatric allo-HCT. Single-center retrospective cohort analysis of children who underwent their first allo-HCT from January 2014 to December 2020. Weekly quantitative plasma CMV polymerase chain reaction was performed until Day +100 and PET was initiated once VL exceeded a pre-defined threshold per institutional guidelines. Patients were followed for 1-year post-HCT to evaluate virologic and clinical outcomes including end-organ disease (EOD), overall survival (OS), and non-relapse mortality (NRM). Among 146 allo-HCT recipients, CMV DNAemia occurred in 40 patients (27%) at a median of 15 days post-HCT (interquartile range 6-28.5). Ten percent (n = 4) had spontaneous resolution of DNAemia, while 90% (n = 36) required PET. PET initiated when CMV VL was ≥ 1000 IU/mL (n = 21) vs when VL < 1000 IU/mL (n = 15) resulted in higher peak CMV VL (12,670vs. 1284 IU/mL, p = 0.0001) and longer time to CMV DNAemia resolution (36vs. 24 days, p = 0.035). There were no differences in EOD, OS, or NRM at 12 months post-HCT based on VL at PET initiation. Initiating PET when CMV VL was ≥1000 IU/mL resulted in significantly higher peak VL and prolonged DNAemia, with no differences in EOD, OS, or NRM at 12 months post pediatric HCT.

High throughput profiling identified PA-L106R amino acid substitution in A(H1N1)pdm09 influenza virus that confers reduced susceptibility to baloxavir in vitro

Baloxavir acid (BXA) is a pan-influenza antiviral that targets the cap-dependent endonuclease of the polymerase acidic (PA) protein required for viral mRNA synthesis. To gain a comprehensive understanding on the molecular changes associated with reduced susceptibility to BXA and their fitness profile, we performed a deep mutational scanning at the PA endonuclease domain of an A (H1N1)pdm09 virus. The recombinant virus libraries were serially passaged in vitro under increasing concentrations of BXA followed by next-generation sequencing to monitor PA amino acid substitutions with increased detection frequencies. Enriched PA amino acid changes were each introduced into a recombinant A (H1N1)pdm09 virus to validate their effect on BXA susceptibility and viral replication fitness in vitro. The I38 T/M substitutions known to confer reduced susceptibility to BXA were invariably detected from recombinant virus libraries within 5 serial passages. In addition, we identified a novel L106R substitution that emerged in the third passage and conferred greater than 10-fold reduced susceptibility to BXA. PA-L106 is highly conserved among seasonal influenza A and B viruses. Compared to the wild-type virus, the L106R substitution resulted in reduced polymerase activity and a minor reduction of the peak viral load, suggesting the amino acid change may result in moderate fitness loss. Our results support the use of deep mutational scanning as a practical tool to elucidate genotype-phenotype relationships, including mapping amino acid substitutions with reduced susceptibility to antivirals.

Relationship between acute SARS-CoV-2 viral clearance with Long COVID Symptoms: a cohort study.

The relationship between SARS-CoV-2 viral dynamics during acute infection and the development of long COVID is largely unknown. A total of 7361 asymptomatic community-dwelling people enrolled in the Test Us at Home parent study between October 2021 and February 2022. Participants self-collected anterior nasal swabs for SARS-CoV-2 RT-PCR testing every 24-48 hours for 10-14 days, regardless of symptom or infection status. Participants who had no history of COVID-19 at enrollment and who were subsequently found to have ≥1 positive SARS-CoV-2 RT-PCR test during the parent study were recontacted in August 2023 and asked whether they had experienced long COVID, defined as the development of new symptoms lasting 3 months or longer following SARS-CoV-2 infection. Participant's cycle threshold values were converted into viral loads, and slopes of viral clearance were modeled using post-nadir viral loads. Using a log binomial model with the modeled slopes as the exposure, we calculated the relative risk of subsequently developing long COVID with 1-2 symptoms, 3-4 symptoms, or 5+ symptoms, adjusting for age, number of symptoms, and SARS-CoV-2 variant. Adjusted relative risk (aRR) of individual long COVID symptoms based on viral clearance was also calculated. 172 participants were eligible for analyses, and 59 (34.3%) reported experiencing long COVID. The risk of long COVID with 3-4 symptoms and 5+ symptoms increased by 2.44 times (aRR: 2.44; 95% CI: 0.88-6.82) and 4.97 times (aRR: 4.97; 95% CI: 1.90-13.0) per viral load slope-unit increase, respectively. Participants who developed long COVID had significantly longer times from peak viral load to viral clearance during acute disease than those who never developed long COVID (8.65 [95% CI: 8.28-9.01] vs. 10.0 [95% CI: 9.25-10.8]). The slope of viral clearance was significantly positively associated with long COVID symptoms of fatigue (aRR: 2.86; 95% CI: 1.22-6.69), brain fog (aRR: 4.94; 95% CI: 2.21-11.0), shortness of breath (aRR: 5.05; 95% CI: 1.24-20.6), and gastrointestinal symptoms (aRR: 5.46; 95% CI: 1.54-19.3). We observed that longer time from peak viral load to viral RNA clearance during acute COVID-19 was associated with an increased risk of developing long COVID. Further, slower clearance rates were associated with greater number of symptoms of long COVID. These findings suggest that early viral-host dynamics are mechanistically important in the subsequent development of long COVID.

Helminth induced monocytosis conveys protection from respiratory syncytial virus infection in mice.

Respiratory syncytial virus (RSV) infection in infants is a major cause of viral bronchiolitis and hospitalisation. We have previously shown in a murine model that ongoing infection with the gut helminth Heligmosomoides polygyrus protects against RSV infection through type I interferon (IFN-I) dependent reduction of viral load. Yet, the cellular basis for this protection has remained elusive. Given that recruitment of mononuclear phagocytes to the lung is critical for early RSV infection control, we assessed their role in this coinfection model. Mice were infected by oral gavage with H. polygyrus. Myeloid immune cell populations were assessed by flow cytometry in lung, blood and bone marrow throughout infection and after secondary infection with RSV. Monocyte numbers were depleted by anti-CCR2 antibody or increased by intravenous transfer of enriched monocytes. H. polygyrus infection induces bone marrow monopoiesis, increasing circulatory monocytes and lung mononuclear phagocytes in a IFN-I signalling dependent manner. This expansion causes enhanced lung mononuclear phagocyte counts early in RSV infection that may contribute to the reduction of RSV load. Depletion or supplementation of circulatory monocytes prior to RSV infection confirms that these are both necessary and sufficient for helminth induced antiviral protection. H. polygyrus infection induces systemic monocytosis contributing to elevated mononuclear phagocyte numbers in the lung. These cells are central to an anti-viral effect that reduces the peak viral load in RSV infection. Treatments to promote or modulate these cells may provide novel paths to control RSV infection in high risk individuals.

#1569 Cytomegalovirus (CMV) infection in renal transplant patients managed with early pre-emptive treatment

Abstract Background and Aims Human Cytomegalovirus (CMV) can cause significant morbidity in transplant recipients. Primary CMV infection in CMV seronegative recipients (R−) and reactivation of CMV in seropositive recipients (R+) post-transplant can lead to CMV end organ disease (EOD). At Royal Free Hospital (RFH), London, United Kingdom, CMV EOD is prevented through pre-emptive therapy (PET), which utilises quantitative real-time PCR (qPCR) in whole blood to monitor all transplant patients and guide therapeutic interventions (1). PET is started in D+R− transplant patients following the first detectable CMV DNA (≥200 copies/ml) in blood (2). For CMV seropositive patients, PET is started when CMV DNA is ≥3000 copies/ml. This differs from many transplant centres which provide CMV anti-viral prophylaxis for the first 3-6 months post-transplant to patients at high risk of developing CMV EOD. In this observational study, the effectiveness of our PET approach and differences in CMV viral replication kinetics was retrospectively analysed in renal transplant recipients of differing CMV serostatus. Method A retrospective review of results from electronic patient records and laboratory information management system for patients who underwent renal transplantation from April 2021 to January 2023 was conducted. Patients were divided into four groups based on organ donor and recipient CMV IgG serostatus (D+R−, D+R+, D−R+, D−R−). Those who were followed up for less than 90 days or had unknown donor serostatuses were excluded. Results A total of 227 patients who received renal transplantation between April 2021 to January 2023 were identified. Of which, 11% (25/227) were D+R−, 42.3% (96/227) were D+R+, 33% (75/227) were D−R+ and 13.7% (31/227) were D−R−. Within each group, 60% (15/25) of D+R−, 61.5% (59/96) of D+R+ and 48% (36/75) of D−R+ patients developed CMV viraemia during the monitoring period. Of CMV viraemic patients, all D+R− (15/15), 54.2% (32/59) of D+R+ and 27.8% (10/36) of D−R+ patients were treated with valganciclovir as per our PET protocol. None of the D−R− patients developed any CMV viraemia. The mean peak viral load for patients with viraemia requiring treatment with valganciclovir was 4772 copies/ml (range 210-30000 copies/ml) in D+R−, 5050 copies/ml (range 3000-30000 copies/ml) and 5050 copies/ml (range 3300-18000 copies/ml) in D+R+ and D−R+ groups respectively. The mean time to first viraemia was 59 days (range 15-332) for the D+R−, 40 days (range 7-177) for D+R+ and 43 days (range 15-91) for D−R+ patients. Furthermore, the mean duration of viraemia was 34 days for D+R−, 37.5 days for D+R+ and 30.5 days for D−R+ groups. 19 patients had CMV viraemia recurrence requiring re-treatment, 63%were D+R− (12/19), 32% were D+R+ (6/19) and 5% (1/19) were D−R+. Across all four groups, two patients developed CMV EOD. One D+R+ patient was found to have CMV in respiratory sample and one D−R+ patient had CMV on colon biopsy. One D+R− patient developed UL97 mutations (M460I and A594V) conferring ganciclovir resistance due to poor compliance and was treated with maribavir. Conclusion PET is a safe and effective approach which reduces the risk of CMV EOD and antiviral medication resistance in SOT patients. Our PET approach provides monitoring of all patients regardless of CMV serostatus thereby reducing the risk of CMV EOD in all patients by ensuring early treatment of viraemia.

The gastrointestinal tract-restricted helminth H. polygyrus bakeri protects against SARS-CoV-2-induced lung disease in mice

Abstract Helminth-virus coinfection models can provide valuable insights into the regulation and modulation of host antiviral immunity. Epidemiological evidence suggests that pre-existing helminth infection is associated with reduced risk of severe SARS-CoV-2 infection. Several prior studies have reported that Heligmosomoides polygyrus bakeri (Hpb), an enteral murine helminth, protects against infection by respiratory viruses. Here, we developed an Hpb-SARS-CoV-2 coinfection model and show that coinfection with Hpb protects against mouse-adapted SARS-CoV-2 (MA10) induced weight loss and mortality. Compared to mice infected with MA10 alone, coinfected mice have a small reduction in peak lung viral load, increased eosinophil infiltrates in the lung and bronchoalveolar lavage fluid, and better lung function and blood oxygen levels. Using a series of knockout mice, we found that Hpb protects against SARS-CoV-2 independently of several canonical type 2 immunity pathways including STAT6, tuft cells, and IL-33 signaling as well as adaptive immunity. Coinfected mice that are depleted of eosinophils have a partial loss of protection. Together, these findings suggest that enhanced eosinophil production induced by Hpb infection protects mice from MA10-induced inflammation in a STAT6-independent manner.

How robust are estimates of key parameters in standard viral dynamic models?

Mathematical models of viral infection have been developed, fitted to data, and provide insight into disease pathogenesis for multiple agents that cause chronic infection, including HIV, hepatitis C, and B virus. However, for agents that cause acute infections or during the acute stage of agents that cause chronic infections, viral load data are often collected after symptoms develop, usually around or after the peak viral load. Consequently, we frequently lack data in the initial phase of viral growth, i.e., when pre-symptomatic transmission events occur. Missing data may make estimating the time of infection, the infectious period, and parameters in viral dynamic models, such as the cell infection rate, difficult. However, having extra information, such as the average time to peak viral load, may improve the robustness of the estimation. Here, we evaluated the robustness of estimates of key model parameters when viral load data prior to the viral load peak is missing, when we know the values of some parameters and/or the time from infection to peak viral load. Although estimates of the time of infection are sensitive to the quality and amount of available data, particularly pre-peak, other parameters important in understanding disease pathogenesis, such as the loss rate of infected cells, are less sensitive. Viral infectivity and the viral production rate are key parameters affecting the robustness of data fits. Fixing their values to literature values can help estimate the remaining model parameters when pre-peak data is missing or limited. We find a lack of data in the pre-peak growth phase underestimates the time to peak viral load by several days, leading to a shorter predicted growth phase. On the other hand, knowing the time of infection (e.g., from epidemiological data) and fixing it results in good estimates of dynamical parameters even in the absence of early data. While we provide ways to approximate model parameters in the absence of early viral load data, our results also suggest that these data, when available, are needed to estimate model parameters more precisely.

Characteristics of infections with ancestral, Beta and Delta variants of SARS-CoV-2 in the PHIRST-C community cohort study, South Africa, 2020-2021

BackgroundData on the characteristics of individuals with mild and asymptomatic infections with different SARS-CoV-2 variants are limited. We therefore compared the characteristics of individuals infected with ancestral, Beta and Delta SARS-CoV-2 variants in South Africa.MethodsWe conducted a prospective cohort study in a rural and an urban site during July 2020-August 2021. Mid-turbinate nasal swabs were collected twice-weekly from household members irrespective of symptoms and tested for SARS-CoV-2 using real-time reverse transcription polymerase chain reaction (rRT-PCR). Differences in demographic and clinical characteristics, shedding and cycle threshold (Ct) value of infection episodes by variant were evaluated using multinomial regression. Overall and age-specific incidence rates of infection were compared by variant.ResultsWe included 1200 individuals from 222 households and 648 rRT-PCR-confirmed infection episodes (66, 10% ancestral, 260, 40% Beta, 322, 50% Delta). Symptomatic proportion was similar for ancestral (7, 11%), Beta (44, 17%), and Delta (46, 14%) infections (p=0.4). After accounting for previous infection, peak incidence shifted to younger age groups in successive waves (40-59 years ancestral, 19-39 years Beta, 13-18 years Delta). On multivariable analysis, compared to ancestral, Beta infection was more common in individuals aged 5-12 years (vs 19-39)(adjusted odds ratio (aOR) 2.6, 95% confidence interval (CI)1.1-6.6) and PCR cycle threshold (Ct) value <30 (vs >35)(aOR 3.2, 95%CI 1.3-7.9), while Delta was more common in individuals aged <5 (aOR 6.7, 95%CI1.4-31.2) and 5-12 years (aOR 6.6 95%CI2.6-16.7)(vs 19-39) and Ct value <30 (aOR 4.5, 95%CI 1.3-15.5) and 30-35 (aOR 6.0, 95%CI 2.3-15.7)(vs >35).ConclusionsConsecutive SARS-CoV-2 waves with Beta and Delta variants were associated with a shift to younger individuals. Beta and Delta infections were associated with higher peak viral loads, potentially increasing infectiousness.

HIV, HIV-Specific Factors, and Myocardial Disease in Women.

People with human immunodeficiency virus (HIV) (PWH) have an increased risk of cardiovascular disease (CVD). Cardiac magnetic resonance (CMR) has documented higher myocardial fibrosis, inflammation, and steatosis in PWH, but studies have mostly relied on healthy volunteers as comparators and focused on men. We investigated the associations of HIV and HIV-specific factors with CMR phenotypes in female participants enrolled in the Women's Interagency HIV Study's New York and San Francisco sites. Primary phenotypes included myocardial native (n) T1 (fibro-inflammation), extracellular volume fraction (fibrosis), and triglyceride content (steatosis). Associations were evaluated with multivariable linear regression, and results pooled or meta-analyzed across centers. Among 261 women with HIV (WWH, N = 362), 76.2% had undetectable viremia at CMR. For the 82.8% receiving continuous antiretroviral therapy (ART) in the preceding 5 years, adherence was 51.7%, and 69.4% failed to achieve persistent viral suppression (40.7% with peak viral load <200 cp/mL). Overall, WWH showed higher nT1 than women without HIV after full adjustment. This higher nT1 was more pronounced in those with antecedent or current viremia or nadir CD4+ count <200 cells/μL, with the latter also associated with higher extracellular volume fraction. WWH and current CD4+ count <200 cells/μL had less cardiomyocyte steatosis. Cumulative exposure to specific ART showed no associations. Compared with sociodemographically similar women without HIV, WWH on ART exhibit higher myocardial fibro-inflammation, which is more prominent with unsuppressed viremia or CD4+ lymphopenia. These findings support the importance of improved ART adherence strategies, along with better understanding of latent infection, to mitigate cardiac end-organ damage in this population.

Viral load kinetics and the clinical consequences of cytomegalovirus in kidney transplantation.

Despite advances in clinical management, cytomegalovirus (CMV) infection remains a serious complication and an important cause of morbidity and mortality following kidney transplantation. Here, we explore the importance of viral load kinetics as predictors of risk and potential guides to therapy to reduce transplant failure in a large longitudinal Genome Canada Transplant Consortium (GCTC) kidney transplant cohort. We examined the relationship between CMV infection rates and clinical characteristics, CMV viral load kinetics, and graft and patient outcomes in 2510 sequential kidney transplant recipients in the British Columbia Transplant Program. Transplants were performed between January 1, 2008, and December 31, 2018, were managed according to a standard protocol, and were followed until December 31, 2019, representing over 3.4 million days of care. Longitudinal CMV testing was performed in 2464 patients, of whom 434 (17.6%) developed a first episode of CMV viremia at a median of 120 (range: 9-3906) days post-transplant. Of these patients, 93 (21.4%) had CMV viremia only and 341 (78.6%) had CMV viremia with clinical complications, of whom 21 (4.8%) had resulting hospitalization. A total of 279 (11.3%) patients died and 177 (7.2%) patients lost their graft during the 12 years of follow-up. Patients with CMV infection were at significantly greater risk of graft loss (p=0.0041) and death (p=0.0056) than those without. Peak viral load ranged from 2.9 to 7.0 (median: 3.5) log10 IU/mL, the duration of viremia from 2 to 100 (15) days, and the viral load area under the curve from 9.4 to 579.8 (59.7) log10 IU/mL × days. All three parameters were closely inter-related and were significantly increased in patients with more severe clinical disease or with graft loss (p=0.001). Duration of the first CMV viremic episode greater than 15 days or a peak viral load ≥4.0 log10 IU/mL offered simple predictors of clinical risk with a 3-fold risk of transplant failure. Viral load kinetics are closely related to CMV severity and to graft loss following kidney transplantation and provide a simple index of risk which may be valuable in guiding trials and treatment to prevent transplant failure.

Monitoring of adenoviremia in pediatric patients undergoing hematopoietic stem cell transplantation: Is it alone sufficient to predict adenoviral disease?

We aimed to evaluate our pediatric HSCT recipients routinely monitored for adenoviremia and to determine the adequacy of this monitoring in predicting adenoviral disease (AD). A retrospective cohort of patients who underwent allogeneic HSCT between January 2021 and August 2022, and routinely monitored for adenoviremia by real-time PCR was included in our survey. Demographic and clinical data of the patients were recorded. Incidence rates, risk factors, and mortality rates related to adenoviremia, and AD were analyzed. Among 104 HSCTs performed in 94 patients adenovirus (AdV) was revealed in 27 (26%) episodes and adenoviremia in 18 (17.3%) HSCT episodes. AD without adenoviremia developed in nine episodes (8.6%). Disseminated disease was significantly more frequently detected in episodes with adenoviremia (p = .008). GVHD was independent risk factor for AdV detection (OR: 8.6, 95% CI: 2.03-33.7, p = .001). Viremia developed within a shorter time interval after HSCT in isolated episodes of adenoviremia compared to those with concomitant AD (p = .006). Initial and peak viral loads were significantly higher in adenoviremia with AD (p < .001). Mortality was higher in the AdV-detected episodes (p < .001) than in the AdV-undetected episodes. AdV-related mortality was found to be 22.2%. Adenoviremia increased the risk of mortality (OR: 1.2, 95% CI: 0.22-1.33, p = .01). Adenoviremia monitoring is an important process in the detection of AD. Since some patients may develop AD without accompanying by adenoviremia, monitoring for AdV in blood samples should be supported with other monitoring methods in order to evaluate the probable involvement of different organs or systems.

Potent antibody-dependent cellular cytotoxicity of a V2-specific antibody is not sufficient for protection of macaques against SIV challenge.

Fc-mediated antibody effector functions, such as antibody-dependent cellular cytotoxicity (ADCC), can contribute to the containment HIV-1 replication but whether such activities are sufficient for protection is unclear. We previously identified an antibody to the variable 2 (V2) apex of the HIV-1 Env trimer (PGT145) that potently directs the lysis of SIV-infected cells by NK cells but poorly neutralizes SIV infectivity. To determine if ADCC is sufficient for protection, separate groups of six rhesus macaques were treated with PGT145 or a control antibody (DEN3) by intravenous infusion followed five days later by intrarectal challenge with SIVmac239. Despite high concentrations of PGT145 and potent ADCC activity in plasma on the day of challenge, all animals became infected and viral loads did not differ between the PGT145- and DEN3-treated animals. To determine if PGT145 can protect against a neutralization-sensitive virus, two additional groups of six macaques were treated with PGT145 and DEN3 and challenged with an SIVmac239 variant with a single amino acid change in Env (K180S) that increases PGT145 binding and renders the virus susceptible to neutralization by this antibody. Although there was no difference in virus acquisition, peak and chronic phase viral loads were significantly lower and time to peak viremia was significantly delayed in the PGT145-treated animals compared to the DEN3-treated control animals. Env changes were also selected in the PGT145-treated animals that confer resistance to both neutralization and ADCC. These results show that ADCC is not sufficient for protection by this V2-specific antibody. However, protection may be achieved by increasing the affinity of antibody binding to Env above the threshold required for neutralization.

The chemokine receptor CXCR3 promotes CD8+ T cell-dependent lung pathology during influenza pathogenesis.

The dual role of CD8+ T cells in influenza control and lung pathology is increasingly appreciated. To explore whether protective and pathological functions can be linked to specific subsets, we dissected CD8+ T responses in influenza-infected murine lungs. Our single-cell RNA-sequencing (scRNA-seq) analysis revealed notable diversity in CD8+ T subpopulations during peak viral load and infection-resolved state. While enrichment of a Cxcr3hi CD8+ T effector subset was associated with a more robust cytotoxic response, both CD8+ T effector and central memory exhibited equally potent effector potential. The scRNA-seq analysis identified unique regulons regulating the cytotoxic response in CD8+ T cells. The late-stage CD8+ T blockade in influenza-cleared lungs or continuous CXCR3 blockade mitigated lung injury without affecting viral clearance. Furthermore, adoptive transfer of wild-type CD8+ T cells exacerbated influenza lung pathology in Cxcr3-/- mice. Collectively, our data imply that CXCR3 interception could have a therapeutic effect in preventing influenza-linked lung injury.