Immunosuppressed Organ Transplant Recipients Research Articles

Local blockade of tacrolimus promotes T-cell-mediated tumor regression in systemically immunosuppressed hosts

BackgroundImmunosuppressive drugs such as tacrolimus have revolutionized our ability to transplant organs between individuals. Tacrolimus acts systemically to suppress the activity of T-cells within and around transplanted organs. However, tacrolimus...

Identification of Genetic Risk Factors for Keratinocyte Cancer in Immunosuppressed Solid Organ Transplant Recipients: A Case-Control Study

Because of long-term immunosuppression, solid organ transplant recipients are at increased risk for keratinocyte cancer. We matched solid organ transplant patients (n = 150), cases with keratinocyte cancers and tumor-free controls, considering the most important risk factors for keratinocyte cancer in solid organ transplant recipients. Using whole exome data of germline DNA from this patient cohort, we identified several genetic loci associated with the occurrence of multiple keratinocyte cancers. We found one genome-wide significant association of a common single nucleotide polymorphism located in EXOC3 (rs72698504). In addition, we found several variants with a p-value of less than 10−5 associated with the number of keratinocyte cancers. These variants were located in the genes CYB561, WASHC1, PITRM1-AS1, MUC8, ABI3BP, and THBS2-AS1. Using whole exome sequencing data, we performed groupwise tests for rare missense variants in our dataset and found robust associations (p < 10−6, Burden Zeggini test) between MC1R, EPHA8, EPO, MYCT1, ADGRG3, and MGME1 and keratinocyte cancer. Thus, overall, we detected genes involved in pigmentation/UV protection, tumor suppression, immunomodulation, intracellular traffic, and response to UV as genetic risk factors for multiple keratinocyte cancers in solid organ transplant recipients. We also grouped selected genes to pathways and found a selection of genes involved in the “cellular response to UV” to be significantly associated with multiple keratinocyte cancers.

BI02 Disseminated toxoplasmosis presenting as panniculitis in an immunocompromised patient

Abstract Inflammatory dermatoses and inflammatory reaction patterns to underlying systemic disease are relatively uncommon in immunosuppressed organ transplant recipients (OTRs) and infection should always be suspected as a possible cause. We present an OTR with biopsy-proven panniculitis resulting from disseminated toxoplasmosis, only identified after extensive histological analysis. A 45-year-old Nigerian woman who was profoundly immunocompromised through a combination of a kidney transplant 12 months earlier, hyposplenism due to sickle cell anaemia and a CD4+ count 74 × 106 cells L–1 (> 455 × 106 L–1) presented with a 3-month history of > 20 painful, red–purple and hyperpigmented subcutaneous nodules and plaques up to 2 cm in diameter limited to her legs, associated with fatigue and weight loss. She only had childhood contact with cats. There was no lymphoedema or lymphadenopathy, and she was HIV negative. Urgent skin biopsy excluded Kaposi sarcoma and demonstrated a lobular, necrotizing panniculitis, a mixed inflammatory cell infiltrate and evidence of vasculitis. The cause was unclear; cultures for mycobacterial, fungal and bacterial infections were negative. However, on rereview of histology, within areas of inflammation and necrosis in the subcutaneous fat, there were a few scattered structures (10–30 μm in diameter) consisting of small basophilic periodic acid–Schiff-positive ‘dots’ within bright eosinophilic cytoplasm, raising the possibility of toxoplasmosis. Toxoplasma immuno­staining was positive. Further tertiary review of histology and immunostaining by the Hospital for Tropical Diseases agreed that there was no other causative organism and the panniculitis and vasculitis were consistent with active toxoplasmosis. The diagnosis of toxoplasma reactivation was supported by positive toxoplasma IgG on pretransplant bloods. Magnetic resonance imaging of the head was consistent with cerebral toxoplasmosis. She received treatment with clindamycin, pyrimethamine and folinic acid and, thereafter, long-term cotrimoxazole prophylaxis. Cutaneous toxoplasmosis is rare, with only three reported cases over the last 10 years. Historically, a wide spectrum of clinical morphologies has been described, including maculopapular rashes, nodules, ulcers, dermatomyositis and even mimicry of varicella and graft-versus-host disease. Most cases affect immunocompromised patients. In our patient, this was the result of reactivation of latent infection, which is more common in West Africa, coinciding with profound immunosuppression. In our case, a diagnosis was only made after extensive histological review. Given the varied morphologies of clinical presentations, it is possible that this condition may be easily missed, with potentially serious consequences. In summary, we highlight the importance of maintaining a high index of suspicion for infection and the need for careful clinicopathological correlation in OTRs presenting with apparently atypical inflammatory skin lesions.

Importance of Physiotherapy in Post Pneumonectomy Renal Transplant Recipient: A Case Report

Pulmonary mucormycosis is a rare but opportunistic fungal infection that complicates immunosuppressed solid organ transplant recipients. Although antifungal medication is the remedial dependence in management of pulmonary mucormycosis, early surgical intervention provides advantage over medical treatment alone. However, major impairments and complications such as altered pulmonary and physical function induced by surgery are known to occur. We report the case of a 25-year-old male post renal transplantation on immunosuppression who developed invasive pulmonary mucormycosis in right middle and lower lobe. Liposomal Amphotericin B therapy provided insufficient infection control and lesion invaded the adjacent chest wall, ribs and intercostal muscles. After right pneumonectomy combined with anterior chest wall resection, the initial post-operative physiotherapy assessment was carried out. The patient was found to have productive cough, dyspnoea, chest pain, reduced chest expansion and excursion, limited range of motion of shoulder on affected side and limited activities of daily living. Six weeks of inpatient physiotherapy regime was given which included breathing exercises, thoracic mobility exercises, incentive spirometry, active range of motion exercises, positioning, bed mobility and early ambulation. Follow up assessment showed reduced pain intensity and improvement in oxygen saturation, dyspnoea, Timed up and go test (TUG) time, handgrip strength, activities of daily living and quality of life [Short form 36 (SF-36)]. Keywords: Pneumonectomy, Thoracic Surgery, Renal Transplant, Physiotherapy

Disparities in vaccination rates in solid organ transplant patients.

Vaccinations against preventable respiratory infections such as Streptococcus pneumoniae and influenza are important in immunosuppressed solid organ transplant (SOT) recipients. Little is known about the role of age, race, ethnicity, sex, and sociodemographic factors including rurality, or socioeconomic status (SES) associated with vaccine uptake in this population. We conducted a population-based study using the Rochester Epidemiology Project, a medical records linkage system, to assess socioeconomic and demographic factors associated with influenza and pneumococcal vaccination rates among adult recipients of solid organ transplantation (aged 19-64 years) living in four counties in southeastern Minnesota. Vaccination data were obtained from the Minnesota Immunization Information Connection from June 1, 2010 to June 30, 2020. Vaccination rate was assessed with Poisson and logistic regression models. A total of 468 SOT recipients were identified with an overall vaccination rate of 57%-63% for influenza and 56% for pneumococcal vaccines. As expected, vaccination for pneumococcal vaccine positively correlated with influenza vaccination. Rural patients had decreased vaccination in both compared to urban patients, even after adjusting for age, sex, race, ethnicity, and SES. Although the population was mostly White and non-Hispanic, neither vaccination differed by race or ethnicity, but influenza vaccination did by SES. Among organ transplant groups, liver and lung recipients were least vaccinated for influenza, and heart recipients were least up-to-date on pneumococcal vaccines. Rates of vaccination were below national goals. Rurality was associated with undervaccination. Further investigation is needed to understand and address barriers to vaccination among transplant recipients.

Vaccine Effectiveness Against the SARS-CoV-2 B.1.1.529 Omicron Variant in Solid Organ and Islet Transplant Recipients in England: A National Retrospective Cohort Study.

The effectiveness of vaccines against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) B.1.1.529 Omicron variant in immunosuppressed solid organ and islet transplant (SOT) recipients is unclear. National registries in England were linked to identify SARS-CoV-2 positive tests, noninjury hospitalization within 14 d, and deaths within 28 d between December 7, 2020, and March 31, 2022 in adult SOT recipients. Incidence rate ratios (IRRs) for infection, and hospitalization or death, were adjusted for recipient demographics and calendar month for the Omicron-dominant period (December 20, 2021, to March 31, 2022). Mortality risk following SARS-CoV-2 infection was adjusted for recipient demographics and dominant variant using a Cox proportional-hazards model for the entire time period. During the Omicron-dominant period, infection IRRs (95% confidence intervals) were higher in those receiving 2, 3, and 4 vaccine doses than in unvaccinated patients (1.25 [1.08-1.45], 1.46 [1.28-1.67], and 1.79 [1.54-2.06], respectively). However, hospitalization or death IRRs during this period were lower in those receiving 3 or 4 vaccine doses than in unvaccinated patients (0.62 [0.45-0.86] and 0.39 [0.26-0.58], respectively). Risk-adjusted analyses for deaths after SARS-CoV-2 infection between December 7, 2020, and March 31, 2022, found hazard ratios (95% confidence intervals) of 0.67 (0.46-0.98), 0.46 (0.30-0.69), and 0.18 (0.09-0.35) for those with 2, 3, and 4 vaccine doses, respectively, when compared with the unvaccinated group. In immunosuppressed SOT recipients, vaccination is associated with incremental, dose-dependent protection against hospitalization or death after SARS-CoV-2 infection, including against the Omicron variant.

COVID-19 mortality may be reduced among fully vaccinated solid organ transplant recipients.

Solid organ transplant (SOT) recipients are at increased risk for morbidity and mortality from COVID-19 due to their immunosuppressed state and reduced immunogenicity from COVID-19 mRNA vaccines. This investigation examined the association between COVID-19 mRNA vaccination status and mortality among SOT recipients diagnosed with COVID-19. A retrospective, registry-based chart review was conducted investigating COVID-19 mortality among immunosuppressed solid organ transplant (SOT) recipients in a large metropolitan healthcare system in Houston, Texas, USA. Electronic health record data was collected from consecutive SOT recipients who received a diagnostic SARS-CoV-2 test between March 1, 2020, and October 1, 2021. The primary exposure was COVID-19 vaccination status at time of COVID-19 diagnosis. Patients were considered 'fully vaccinated' at fourteen days after completing their vaccine course. COVID-19 mortality within 60 days and intensive care unit admission within 30 days were primary and secondary endpoints, respectively. Among 646 SOT recipients who were diagnosed with COVID-19 at Houston Methodist Hospital between March 2020, and October 2021, 70 (10.8%) expired from COVID-19 within 60 days. Transplanted organs included 63 (9.8%) heart, 355 (55.0%) kidney, 108 (16.7%) liver, 70 (10.8%) lung, and 50 (7.7%) multi-organ. Increasing age was a risk factor for COVID-19 mortality, while vaccination within 180 days of COVID-19 diagnosis was protective in Cox proportional hazard models with hazard ratio 1.04 (95% CI: 1.01-1.06) and 0.31 (0.11-0.90), respectively). These findings were confirmed in the propensity score matched cohort between vaccinated and unvaccinated patients. This investigation found COVID-19 mortality may be significantly reduced among immunosuppressed SOT recipients within 6 months following vaccination. These findings can inform vaccination policies targeting immunosuppressed populations worldwide.

COVID-19 Infection Does Not Alter HLA Antibody Reactivity

The requirement for immunosuppression in organ transplant recipients, particularly suppression of the T cell response, has made this population especially vulnerable to prolonged and severe infections during the ongoing SARS-CoV-2 pandemic.1 Acknowledgment of this increased risk led to the reduction of deceased-donor organ transplantation, and for many programs, complete cessation of living-donor operations during the early periods of the COVID-19 pandemic.2,3 Nevertheless, for transplant recipients, the risk of contracting viral disease does not exist in a vacuum.

Ablative Fractional Laser-assisted Low-irradiance Photodynamic Therapy for Treatment of Actinic Keratoses in Organ Transplant Recipients: A Prospective, Randomized, Intraindividual Controlled Trial.

Pain and inferior efficacy are major limiting factors of conventional photodynamic therapy for the field treatment of actinic keratoses in immunosuppressed organ transplant recipients. This prospective randomized controlled study evaluates the efficacy and tolerability of ablative fractional laser system pretreatment combined with low-irradiance photodynamic therapy (18.5 mW/cm2) compared with conventional photodynamic therapy (61.67 mW/cm2) in the treatment of actinic keratoses on the face and scalp in organ transplant recipients, using a red light-emitting diode lamp at a total light dose of 37 J/cm2. Low-irradiance photodynamic therapy combined with Er:YAG pretreatment achieved a significantly superior lesion response rate (mean ± standard deviation 77.3 ± 23.6%) compared with conventional photodynamic therapy (61.8 ± 21.4%; p = 0.025) in intra-individual fields at 3 months without negatively impacting pain (p = 0.777) or cosmetic outcome (p = 0.157).

Spectrum of Nonkeratinocyte Skin Cancer Risk Among Solid Organ Transplant Recipients in the US

Nonkeratinocyte skin cancers are an important cause of morbidity and mortality for immunosuppressed solid organ transplant recipients (SOTRs), but the spectrum of disease and risk factor characteristics are unknown. To characterize the spectrum of disease and risk factors for common and rare nonkeratinocyte skin cancers in SOTRs. This population-based cohort study included 444 497 SOTRs who underwent a transplant in the US between January 1, 1987, and December 31, 2017, using linked data from the national transplant registry and 32 cancer registries. Data analysis was conducted from April 1, 2021, to September 30, 2021. Standardized incidence ratios (SIRs) were used to assess risk relative to the general population, and Poisson regression was used to evaluate risk factors. A total of 2380 nonkeratinocyte skin cancers were identified among 444 497 SOTRs (median age at transplant, 50 years; range, 0-96 years; 274 276 [61.7%] male; 272 241 [61.2%] non-Hispanic White). Melanoma was the most common cancer (1471 [61.8%]), followed by Merkel cell carcinoma (334 [14.0%]), Kaposi sarcoma (186 [7.8%]), sebaceous carcinoma (170 [7.1%]), and cutaneous lymphomas (108 [4.5%]). Risks were most strongly elevated for cancers associated with viruses, including Kaposi sarcoma (SIR, 20.5; 95% CI, 17.7-23.7), Merkel cell carcinoma (SIR, 16.2; 95% CI, 14.5-18.1), and extranodal natural killer/T-cell lymphoma (SIR, 44.3; 95% CI, 5.37-160). Risks were also significantly elevated for sebaceous carcinoma (SIR, 15.2; 95% CI, 13.0-17.7), anaplastic large cell lymphoma (SIR, 6.82; 95% CI, 4.53-9.85), and diffuse large B-cell lymphoma (SIR, 5.17; 95% CI, 3.28-7.76). Several characteristics were independently associated with greater risk for multiple skin cancer types, including male sex, older age at transplant, factors associated with UV radiation exposure (non-Hispanic White race and ethnicity, living in an area with higher UV radiation exposure, and posttransplant diagnosis of keratinocyte carcinoma), and increasing time since transplantation. Treatment with mammalian target of rapamycin inhibitors was associated with reduced melanoma incidence (incidence rate ratio, 0.75; 95% CI, 0.57-0.98). A total of 847 skin cancers (39.4%) occurred on the head and neck. The findings of this cohort study suggest that viruses, UV radiation exposure, and immunosuppression are associated with the development of skin cancer in SOTRs. Certain high-risk subgroups may benefit from increased skin surveillance, and treatment with mammalian target of rapamycin inhibitors could be effective for melanoma chemoprevention in the transplant population.

Virucidal and Immunostimulating Activities of Monogalactosyl Diacylglyceride from Coccomyxa sp. KJ, a Green Microalga, against Murine Norovirus and Feline Calicivirus.

Human noroviruses are the most common pathogens causing acute gastroenteritis and may lead to more severe illnesses among immunosuppressed people, including elderly and organ transplant recipients. To date, there are no safe and effective vaccines or antiviral agents for norovirus infections. In the present study, we aimed to demonstrate the antiviral activity of monogalactosyl diacylglyceride (MGDG) isolated from a microalga, Coccomyxa sp. KJ, against murine norovirus (MNV) and feline calicivirus (FCV), the surrogates for human norovirus. MGDG showed virucidal activities against these viruses in a dose- and time-dependent manner—MGDG at 100 μg/mL reduced the infectivity of MNV and FCV to approximately 10% after 60 min incubation. In the animal experiments of MNV infection, intraoral administration of MGDG (1 mg/day) exerted a therapeutic effect by suppressing viral shedding in the feces and produced high neutralizing antibody titers in sera and feces. When MGDG was orally administered to immunocompromised mice treated with 5-fluorouracil, the compound exhibited earlier stopping of viral shedding and higher neutralizing antibody titers of sera than those in the control mice administered with distilled water. Thus, MGDG may offer a new therapeutic and prophylactic alternative against norovirus infections.

Post-transplant Malignancies Show Reduced T-cell Abundance and Tertiary Lymphoid Structures as Correlates of Impaired Cancer Immunosurveillance.

An increased risk to develop cancer is one of the most challenging negative side effects of long-term immunosuppression in organ transplant recipients and impaired cancer immunosurveillance is assumed as underlying mechanism. This study aims to elucidate transplant-related changes in the tumor immune microenvironment (TME) of cancer. Data from 123 organ transplant recipients (kidney, heart, lung, and liver) were compared with historic data from non-immunosuppressed patients. Digital image analysis of whole-section slides was used to assess abundance and spatial distribution of T cells and tertiary lymphoid structures (TLS) in the TME of 117 tumor samples. Expression of programmed cell death 1 ligand 1 (PD-L1) and human-leucocyte-antigen class I (HLA-I) was assessed on tissue microarrays. We found a remarkably reduced immune infiltrate in the center tumor (CT) regions as well as the invasive margins (IM) of post-transplant cancers. These differences were more pronounced in the IM than in the CT and larger for CD8+ T cells than for CD3+ T cells. The Immune-score integrating results from CT and IM was also lower in transplant recipients. Density of TLS was lower in cancer samples of transplant recipients. The fraction of samples with PD-L1 expression was higher in controls whereas decreased expression of HLA-I was more common in transplant recipients. Our study demonstrates the impact of immunosuppression on the TME and supports impaired cancer immunosurveillance as important cause of post-transplant cancer. Modern immunosuppressive protocols and cancer therapies should consider the distinct immune microenvironment of post-transplant malignancies.

Changes in the skin microbiome associated with squamous cell carcinoma in transplant recipients

Actinic keratoses (AK) arise in severely photo-damaged skin and can progress to squamous cell carcinomas (SCC). AK and SCC are common in Caucasian populations, and immunosuppressed individuals have a markedly higher risk of developing SCC. An overabundance of Staphylococcus aureus has been reported in AK and SCC lesions of immunocompetent individuals, however, the AK/SCC microbiome in immunosuppressed cohorts has not been investigated. Here, the microbial profile and bacterial load of AK, SCC and control skin swabs from 32 immunosuppressed organ transplant recipients were characterised via SSU rRNA gene sequencing and qPCR, and compared to a previously described immunocompetent cohort. Although the taxonomic composition of skin swab samples was mostly subject-specific, significant differences were observed between control skin, AK, and SCC in both cohorts. Surface bacterial load was increased and alpha diversity decreased in AK and SCC compared to control skin due to an increased abundance of Staphylococcus species and relative decrease of skin commensals. Staphylococcus epidermidis predominated on SCC from transplant recipients in contrast to SCC of immunocompetent subjects dominated by S. aureus. In conclusion, AK and SCC of immunosuppressed and immunocompetent subjects present with distinctive microbial dysbioses, which may be relevant to SCC pathogenesis and progression.

Real-world Effectiveness of the Pfizer-BioNTech BNT162b2 and Oxford-AstraZeneca ChAdOx1-S Vaccines Against SARS-CoV-2 in Solid Organ and Islet Transplant Recipients.

Background.The clinical effectiveness of vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in immunosuppressed solid organ and islet transplant (SOT) recipients is unclear.Methods.We linked 4 national registries to retrospectively identify laboratory-confirmed SARS-CoV-2 infections and deaths within 28 d in England between September 1, 2020, and August 31, 2021, comparing unvaccinated adult SOT recipients and those who had received 2 doses of ChAdOx1-S or BNT162b2 vaccine. Infection incidence rate ratios were adjusted for recipient demographics and calendar month using a negative binomial regression model, with 95% confidence intervals. Case fatality rate ratios were adjusted using a Cox proportional hazards model to generate hazard ratio (95% confidence interval).Results.On August 31, 2021, it was found that 3080 (7.1%) were unvaccinated, 1141 (2.6%) had 1 vaccine dose, and 39 260 (90.3%) had 2 vaccine doses. There were 4147 SARS-CoV-2 infections and 407 deaths (unadjusted case fatality rate 9.8%). The risk-adjusted infection incidence rate ratio was 1.29 (1.03-1.61), implying that vaccination was not associated with reduction in risk of testing positive for SARS-CoV-2 RNA. Overall, the hazard ratio for death within 28 d of SARS-CoV-2 infection was 0.80 (0.63-1.00), a 20% reduction in risk of death in vaccinated patients (P = 0.05). Two doses of ChAdOx1-S were associated with a significantly reduced risk of death (hazard ratio, 0.69; 0.52-0.92), whereas vaccination with BNT162b2 was not (0.97; 0.71-1.31).Conclusions.Vaccination of SOT recipients confers some protection against SARS-CoV-2–related mortality, but this protection is inferior to that achieved in the general population. SOT recipients require additional protective measures, including further vaccine doses, antiviral drugs, and nonpharmaceutical interventions.

COVID-19 infection in post liver transplant children: a year follow up showing good short term but poor long term outcome

Background and Aim: Current pandemic due to coronavirus 19 is of major concern in immunosuppressed pediatric solid organ transplant recipients. Data is scarce in the pediatrics apart from few case series, especially from developing world. We herein report a single-center experience of COVID-19-positive transplant recipients who were ‰¤ 18 years of age at time of transplantation.

Expression of p53 up-regulated modulator of apoptosis (PUMA) in non-melanoma skin cancer of long-term immunosuppressed solid organ transplant recipients compared to immunocompetent patients.

The risk of UV radiation (UVR)-induced non-melanoma skin cancer (NMSC) is dramatically increased in immunosuppressed organ transplant recipients compared to immunocompetent patients. In the skin, p53 up-regulated modulator of apoptosis (PUMA) is a central regulator of apoptosis in response to UVR damage and immune response regulation. Data on the expression of PUMA in patients with NMSC relative to immune status is limited To study differences in the expression and distribution of PUMA in cutaneous SCC and BCC by immunohistochemistry between immunocompetent patients and organ transplant recipients, and the effect of CsA-containing immunosuppressive maintenance regimens on this expression. PUMA expression in SCC (n = 34) and BCC (n = 20) was analysed comparatively by immunohistochemical staining in matched cohorts of 27 immunocompetent patients and 27 organ transplant recipients SCC and BCC showed unequivocal positive PUMA expression, however, there was no significant difference in NMSC between organ transplant recipients and immunocompetent patients. A 17% reduction in staining score for PUMA in SCC, but not in BCC, of organ transplant recipients treated with a cyclosporin (CsA)-containing regimen was noted compared to organ transplant recipients without chronic CsA intake (p = 0.0381) PUMA expression in SCC, but not BCC, is significantly reduced by CsA-containing therapy, suggesting a disturbance of apoptosis by iatrogenic immunosuppression with a divergent impact on SCC and BCC.

239 Cutaneous squamous cell carcinoma and mortality in end stage renal disease

Multiple factors related to immunosuppression are associated with cutaneous squamous cell carcinoma (cSCC), for example, the increased risk of cSCC observed in immunosuppressed organ transplant recipients, which in turn can lead to death. Patients with end-stage renal disease (ESRD) are known to have dysregulated immune systems; however, the impact of cSCC on mortality in ESRD has not been reported. Therefore, we addressed this question by analyzing the mortality of adult ESRD patients in the US Renal Data System between 2004 and 2014, excluding organ transplant recipients.

Dysregulation of tissue and serum microRNAs in organ transplant recipients with cutaneous squamous cell carcinomas.

Micro RNAs (miRNAs) are considered as promising biomarkers for skin cancer. By next generation sequencing (NGS), we measured and compared miRNA expression profiles of tumor, peri‐lesional, and control tissue of immunosuppressed organ transplant recipients (OTR), suffering from localized cutaneous squamous cell carcinoma (cSCC). Out of 490 miRNAs detected in cSCC tissue, 23 significantly regulated miRNAs were selected for quantitative targeted analysis in serum samples of our patients and control sera from OTR without cSCC. Two onco‐miRNAs (mir‐1290, mir‐1246), previously identified as crucial drivers for tumor initiation and cancer progression, were significantly and exclusively upregulated in both tumor tissue and serum. This finding suggests that miRNA dysregulation in cSCC tissue is reflected in serum even in patients without advanced disease and highly differentiated cSCCs.

Abstract PR08: Noninvasive epidermal sampling as a means of genomic UV dosimetry

Abstract It is now well accepted that normal-appearing, but chronically UV-exposed skin, can harbor tremendous mutational loads while maintaining homeostatic function. Even so, clones of keratinocytes harboring tumorigenic mutations can be readily observed using targeted and whole-exome sequencing. Therefore, it may be possible to objectively measure chronic, cumulative UV exposure as a means of predicting skin cancer risk and measuring molecular responses to chemoprevention by identifying UV-driven mutations or damage in epidermal keratinocytes. However, such a methodology requires the ability to noninvasively sample normal, nonlesional skin. We have previously optimized a novel surfactant mixture that, when coupled to ultrasound or mechanical abrasion, can noninvasively sample epidermis without scarring. This process can be tuned to selectively remove epidermis only. Within hours of application, a fibrinous exudate appears over the wound and this area heals completely within 2 weeks without scarring. Using a Hairless UV-driven model of squamous cell carcinoma, we have been able to sample and perform both exome and RNA sequencing with recovery rates of about 2.5-3.5 μg /cm2 of DNA and RNA. Using this model, we demonstrated a dose-dependent increase in mutational load in normal UV-exposed skin that reflects what is seen in humans. Mice were sampled and the DNA exome was sequenced (150X) following exposure to UV. Among the 28 most mutated genes across the exome, mice sampled after 1 month of UV exposure harbored variants in an average of 12 genes. After 3 months of UV exposure, followed by 2 months of no exposure, variants were observed in an average of 22 genes (80%) of the 28, suggesting continuing evolution of clones harboring mutations in exposed epidermis. Interestingly, at this relatively low coverage, none of the genes is strongly associated with skin cancer; instead, many are not expressed, reflecting the expansion of mutational burdens without strong selection on these alterations. We then extended our efforts into humans by sampling immunosuppressed solid organ transplant recipients with markedly elevated risk for skin cancer. Sun-exposed areas had an average of 4.5 times the number of variants than sun-protected areas across targeted exome sequencing of 348 cancer-related genes at a depth of ~5000X. Over 24 genes (including TP53, ATM, NOTCH, and KMT2 family members) were identified with nonsense C-T transitions, suggesting the presence of detectable (and potentially selected) mutational patterns in cancer-related genes that correlate with clinically relevant exposure. Our results collectively suggest that noninvasive sampling and genomic interrogation of normal-appearing epidermis is feasible and potentially useful as a risk prediction and chemoprevention assessment tool. This approach is easily extended to other surface epithelia, and we are currently enhancing the sensitivity of this assay based on identification of hotspots and nontranscribed genes as identified in our model. This abstract is also being presented as Poster A32. Citation Format: Kenneth Y. Tsai, Elnara Muradova, Sandy S. Ojeda, Charles H. Adelmann, Kimberly Nguyen, Samir Mitragotri, Nishit Patel. Noninvasive epidermal sampling as a means of genomic UV dosimetry [abstract]. In: Proceedings of the AACR Special Conference on Environmental Carcinogenesis: Potential Pathway to Cancer Prevention; 2019 Jun 22-24; Charlotte, NC. Philadelphia (PA): AACR; Can Prev Res 2020;13(7 Suppl): Abstract nr PR08.

The CD4+ T Cell Response to Human Cytomegalovirus in Healthy and Immunocompromised People.

While CD8+ T cells specific for human cytomegalovirus (HCMV) have been extensively studied in both healthy HCMV seropositive carriers and patients undergoing immunosuppression, studies on the CD4+ T cell response to HCMV had lagged behind. However, over the last few years there has been a significant advance in our understanding of the importance and contribution that CMV-specific CD4+ T cells make, not only to anti-viral immunity but also in the potential maintenance of latently infected cells. During primary infection with HCMV in adults, CD4+ T cells are important for the resolution of symptomatic disease, while persistent shedding of HCMV into urine and saliva is associated with a lack of HCMV specific CD4+ T cell response in young children. In immunosuppressed solid organ transplant recipients, a delayed appearance of HCMV-specific CD4+ T cells is associated with prolonged viremia and more severe clinical disease, while in haematopoietic stem cell transplant recipients, it has been suggested that HCMV-specific CD4+ T cells are required for HCMV-specific CD8+ T cells to exert their anti-viral effects. In addition, adoptive T-cell immunotherapy in transplant patients has shown that the presence of HCMV-specific CD4+ T cells is required for the maintenance of HCMV-specific CD8+ T cells. HCMV is a paradigm for immune evasion. The presence of viral genes that down-regulate MHC class II molecules and the expression of viral IL-10 both limit antigen presentation to CD4+ T cells, underlining the important role that this T cell subset has in antiviral immunity. This review will discuss the antigen specificity, effector function, phenotype and direct anti-viral properties of HCMV specific CD4+ T cells, as well as reviewing our understanding of the importance of this T cell subset in primary infection and long-term carriage in healthy individuals. In addition, their role and importance in congenital HCMV infection and during immunosuppression in both solid organ and haemopoietic stem cell transplantation is considered.