Viral Load Kinetics of SARS-CoV-2 In Hospitalized Individuals with COVID-19

SARS-CoV-2 kinetics remain understudied, including the impact of remdesivir. In hospitalized individuals, peak sputum viral load occurred in week 2 of symptoms while peak viremia occurred within a week of symptom-onset, suggesting early systemic seeding of SARS-CoV-2. Remdesivir treatment was associated with faster rates of viral decay.

West Nile Virus Infection in Ruffed Grouse (Bonasa umbellus): Experimental Infection and Protective Effects of Vaccination

Ruffed grouse ( Bonasa umbellus) population numbers in Pennsylvania dramatically declined during the early 2000s and have subsequently remained depressed throughout much of the state. While this decline has been temporally associated with the presence of West Nile virus (WNV), lack of information on the WNV susceptibility of this popular game bird species has limited the ability to interpret the potential impacts of WNV. To address this knowledge gap, virologic, immunologic, pathologic, and clinical responses as well as protective effects of vaccination following experimental WNV inoculation in ruffed grouse were assessed. Four of 10 (40%) naive, WNV-inoculated grouse succumbed to infection within 8 days and had moderate mean peak viremia titers (107.0 plaque-forming units [PFU]/ml serum); severe necrotizing myocarditis with widespread, corresponding immunohistochemical labeling; and minimal encephalitis. Grouse that survived to the prescribed end point of 14 days postinoculation (6/10; 60%) had slightly lower mean peak viremia titers (106.8 PFU/ml serum), moderate myocardial lesions, and more widespread brain lesions with rare corresponding immunohistochemical labeling. Vaccinated, WNV-inoculated birds ( n = 5) had lower mean peak viremia titers (103.6 PFU/ml serum) and minimal lesions, and sham-inoculated, in-contact control birds ( n = 3) had no evidence of infection. All surviving, inoculated birds seroconverted, and WNV-specific antibodies were detectable in serum and Nobuto filter paper strip–eluted blood samples. These data suggest that WNV could serve as an additional population pressure on ruffed grouse in regions where transmission levels are high and WNV competent, ornithophilic vectors exist.

Kyasanur forest disease virus: viremia and challenge studies in monkeys with evidence of cross-protection by Langat virus infection

Kyasanur Forest Disease Virus (KFDV), discovered in 1957, is a member of the tick-borne encephalitis virus (TBEV) complex. Diseases caused by members of the TBEV complex occur in many parts of the world. KFDV produces a hemorrhagic fever in humans in South India and fatal illnesses in both species of monkeys in the area, the black faced langur (Presbytis entellus) and the bonnet macaque (Macaca radiata). Experimental infection of the langur and the bonnet macaque with early mouse passage KFDV strain P9605 resulted in a viremia of up to 11 days duration, peak viremia titers as high as 109, and death in 82 = 100% of the animals. Prolonged passage of the KFDV strain P9605 in monkey kidney tissue culture resulted in a markedly reduced virulence of the virus for both species; peak viremia titers in monkeys decreased by 2.5 to 4.0 log LD 50 (p= 0.001), and the mortality decreased to 10% (p= 0.001). In challenge experiments, monkeys previously infected with tissue-culture-adapted KFDV, or with the related Langat virus from Malaysia, were fully protected against virulent KFDV. These studies in non-human primates lend support to the idea that a live virus vaccine from a member of the TBEV complex may be broadly protective against infections by other members of the TBEV complex.

HHV-6 Viremia Is Frequent but the Incidence of Encephalitis Is Low in Double-Unit Cord Blood Transplant Recipients Transplanted without ATG

Abstract 459 Background: While cord blood transplantation is a known risk factor for Human Herpesvirus-6 (HHV-6) reactivation, recent studies have yielded inconsistent results in regard to the level of viremia which is associated with a high risk of HHV-6 encephalitis. Moreover, the association with graft failure or transplant-related mortality is controversial. Methods: We conducted a retrospective analysis of 125 patients who underwent double-unit cord blood transplantation (DCBT) for the treatment of hematologic malignancies from 2/2006-3/2012 who were monitored for HHV-6 reactivation to examine the incidence and severity of HHV-6 viremia, the incidence of encephalitis, and the association with DCBT outcome. HHV-6 viremia was measured by quantitive PCR of HHV-6 DNA from plasma (lower limit of detection 100 DNA copies/ml). Results: Of the 125 patients (median age 42, range 1–69), 93 (74%) received myeloablative conditioning and 32 (26%) received a non-myeloablative regimen followed by 4–6/6 HLA-A, B antigen, DRB1 allele matched DCBT for the treatment of AML (N = 43, 34%), ALL (N = 24, 19%), MDS/CML/other leukemia (N = 12, 10%), or lymphoma/CLL (N = 46, 37%). No patient received anti-thymocyte globulin (ATG). Of 125 monitored patients, 117 (94%) reactivated HHV-6 to a median peak of 7,600 (range 100–160,000) copies/ml at a median onset of 20 days (range 10–59) post-DCBT. The median time to peak viremia was 23 days (range 12–62) with a median viremia duration of 10 days (range 1–60 days). Fifty-one patients (41% of total, 44% of viremic patients) developed HHV-6 > 10,000 copies/ml (median peak viremia 31,200 copies/ml at 20 days, range 12–57). Only 6 patients (5% of total, 5% of viremic patients) developed HHV-6 > 100,000 copies/ml (median peak 130,000 copies/ml at 19 days, range 14–29). HHV-6 encephalitis occurred in 2 patients (1.6%, peak viremias 13,000 and 118,000, respectively). One patient died from encephalitis and the other had a complete recovery following therapy. Four additional viremic patients had HHV-6 isolated from bronchoalveolar lavage but did not meet criteria for HHV-6 pneumonia. Using a high level viremia definition of > 10,000 copies/ml from days 14–60 (a level reportedly associated with end-organ disease and decreased survival, Dulery, BBMT 2011), viremia was not associated with diagnosis or conditioning regimen. Engrafting unit-recipient HLA-match and TNC, CD34+ and CD3+ cell dose were not associated with high level viremia. Treating viremia as a time-dependent covariate in Cox regression analysis, no association was found between viremia and neutrophil or platelet engraftment. Specifically, there were two graft failures in patients with no or low level viremia and two in patients with high level viremia. There was also no association between viremia and CMV reactivation, day 100 grade II-IV aGVHD, day 100 TRM, relapse or overall survival. A second analysis was performed to examine effects of high level viremia defined as a level > 25,000 copies/ml (N = 31 patients, the highest peak viremia quartile during days 14–60) and no associations with DCBT outcomes were detected. Conclusions: In our DCBT population, nearly all patients have reactivated HHV-6. However, the incidence of end-organ disease is relatively low. We postulate the difference between our findings and other studies reporting higher rates of HHV-6 encephalitis in DCBT recipients could be due to our exclusion of ATG from the conditioning regimen. At this time our understanding of the significance of HHV-6 after CBT is incomplete. We are currently evaluating anti-viral treatment responses, and ultimately a prospective trial is needed to better define the causality between HHV-6 viremia and transplantation outcomes, and to investigate the risk-benefits of pre-emptive therapy. Disclosures: No relevant conflicts of interest to declare.

Progression from Sustained BK Viruria to Sustained BK Viremia with Immunosuppression Reduction Is Not Associated with Changes in the Noncoding Control Region of the BK Virus Genome

Changes in the BK virus archetypal noncoding control region (NCCR) have been associated with BK-virus-associated nephropathy (BKVAN). Whether sustained viremia, a surrogate for BKVAN, is associated with significant changes in the BK-NCCR is unknown. We performed PCR amplification and sequencing of (1) stored urine and (2) plasma samples from the time of peak viremia from 11 patients with sustained viremia who participated in a 200-patient clinical trial. The antimetabolite was withdrawn for BK viremia and reduction of the calcineurin inhibitor for sustained BK viremia. DNA sequencing from the 11 patients with sustained viremia revealed 8 insertions, 16 transversions, 3 deletions, and 17 transitions. None were deemed significant. No patient developed clinically evident BKVAN. Our data support, at a genomic level, the effectiveness of reduction of immunosuppression for prevention of progression from viremia to BKVAN.

CMV Specific T Cells Prevent Progression From Low to High Level Viremia In D+R+ but Not D-R+ Patients.

Abstract 4532 Background. Cytomegalovirus (CMV) reactivates (becomes detectable in blood) in most seropositive hematopoietic cell transplant (HCT) recipients. In some reactivating patients, low level viremia (<50,000 DNA copies/ml plasma, ie, less than our institutional threshold for preemtive therapy) progresses to high level viremia or CMV disease, which is potentially fatal. We hypothesized that low level viremia progresses in patients with low specific T cell counts and spontaneously resolves in patients with high specific T cell counts. Methods. In 30 CMV seropositive HCT recipients monitored weekly for reactivation by real-time PCR, blood was drawn for specific T cell counts within 4 days from the first episode of low level viremia. Fourteen patients received grafts from seropositive donors (D+R+), and 16 patients from seronegative donors (D-R+). Mononuclear cells were stimulated overnight with CMV lysate, pp65 overlapping peptides, no stimulus (negative control) or staphylococcal enterotoxin B (positive control). T cells producing IFNγ, TNFα and/or IL2 were enumerated by flow cytometry. Results. Among D+R+ patients, counts of CMV lysate and pp65 specific CD4 T cells producing IFNγ and TNFα (and not IL2) were higher in patients with spontaneous resolution than patients with progression (p=0.02 for CMV lysate, p=0.004 for pp65). Also, there was an inverse correlation between pp65 specific CD8 T cells producing IFNγ and TNFα and peak viremia (r=-0.94, p=0.005) in D+R+ patients who progressed to high level viremia/disease. In contrast, among D-R+ patients, CMV lysate and pp65 specific T cell counts were similar in patients with spontaneous resolution and patients with progression, and there was no correlation between specific T cell counts and peak viremia. Conclusion. CMV specific T cells play a role in preventing progression from low to high level CMV reactivation/disease in D+R+ patients. Other immune mechanisms (eg, NK cells?) play the role in D-R+ patients. Disclosures: No relevant conflicts of interest to declare.

Simian Immunodeficiency Virus Disease Course Is Predicted by the Extent of Virus Replication during Primary Infection

ABSTRACT To elucidate the relationship between early viral infection events and immunodeficiency virus disease progression, quantitative-competitive and branched-DNA methods of simian immunodeficiency virus (SIV) RNA quantitation were cross-validated and used to measure viremia following infection of rhesus macaques with the pathogenic SIVmac251 virus isolate. Excellent correlation between the methods suggests that both accurately approximate SIV copy number. Plasma viremia was evident 4 days postinfection, and rapid viral expansion led to peak viremia levels of 107 to 109 SIV RNA copies/ml by days 8 to 17. Limited resolution of primary viremia was accompanied by relatively short, though variable, times to the development of AIDS (81 to 630 days). The persistent high-level viremia observed following intravenous inoculation of SIVmac251 explains the aggressive disease course in this model. Survival analyses demonstrated that the disease course is established 8 to 17 days postinfection, when peak viremia is observed. The most significant predictor of disease progression was the extent of viral decline following peak viremia; larger decrements in viremia were associated with both lower steady-state viremia (P = 0.0005) and a reduced hazard of AIDS (P = 0.004). The data also unexpectedly suggested that following SIVmac251 infection, animals with the highest peak viremia were better able to control virus replication rather than more rapidly developing disease. Analysis of early viral replication dynamics should help define host responses that protect from disease progression and should provide quantitative measures to assess the extent to which protective responses may be induced by prophylactic vaccination.