SARS-CoV-2 Vaccine Immunogenicity in Patients with Gastrointestinal Cancer Receiving Systemic Anti-Cancer Therapy.

INTRODUCTION: Patients with gastrointestinal (GI) cancers have an increased risk of serious complications and death from SARS-CoV-2 infection. The immunogenicity of vaccines in patients with GI cancers receiving anti-cancer therapies is unclear. We conducted a prospective study to evaluate the prevalence of neutralizing antibodies in a cohort of GI cancer patients receiving chemotherapy following SARS-CoV-2 vaccination. MATERIALS AND METHODS: Between September 2020 and April 2021, patients with cancer undergoing chemotherapy were enrolled. At baseline (day 0), days 28, 56, and 84, we assessed serum antibodies to SARS-CoV-2 spike (anti-S) and anti-nucleocapsid (anti-NP) and concomitantly assessed virus neutralization using a pseudovirus neutralization assay. Patients received either the Pfizer/BioNTech BNT162b2, or the Oxford/AstraZeneca ChAdOx1 vaccine. RESULTS: All 152 patients enrolled had a prior diagnosis of cancer; colorectal (n = 80, 52.6%), oesophagogastric (n = 38, 25.0%), and hepato pancreatic biliary (n = 22, 12.5%). Nearly all were receiving systemic anti-cancer therapy (99.3%). Of the 51 patients who did not receive a vaccination prior to, or during the study, 5 patients had detectable anti-NP antibodies. Ninety-nine patients received at least one dose of vaccine prior to, or during the study. Within 19 days following the first dose of vaccine, 30.0% had anti-S detected in serum which increased to 70.2% at days 20-39. In the 19 days following a second dose, anti-S positivity was 84.2% (32/38). However, pseudovirus neutralization titers (pVNT80) decreased from days 20 to 39. CONCLUSION: Despite the immunosuppressive effects of chemotherapy, 2 doses of SARS-CoV-2 vaccines are able to elicit a protective immune response in patients' ongoing treatment for gastrointestinal cancers. Decreases in pseudoviral neutralization were observed after 20-39 days, re-affirming the current recommendation for vaccine booster doses. CLINICAL TRIAL REGISTRATION NUMBER: NCT04427280.

IgG Seroconversion and Pathophysiology in Severe Acute Respiratory Syndrome Coronavirus 2 Infection.

We investigated the dynamics of seroconversion in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. During March 29-May 22, 2020, we collected serum samples and associated clinical data from 177 persons in London, UK, who had SARS-CoV-2 infection. We measured IgG against SARS-CoV-2 and compared antibody levels with patient outcomes, demographic information, and laboratory characteristics. We found that 2.0%-8.5% of persons did not seroconvert 3-6 weeks after infection. Persons who seroconverted were older, were more likely to have concurrent conditions, and had higher levels of inflammatory markers. Non-White persons had higher antibody concentrations than those who identified as White; these concentrations did not decline during follow-up. Serologic assay results correlated with disease outcome, race, and other risk factors for severe SARS-CoV-2 infection. Serologic assays can be used in surveillance to clarify the duration and protective nature of humoral responses to SARS-CoV-2 infection.

The QuantuMDx Q-POC SARS-CoV-2 RT-PCR assay for rapid detection of COVID-19 at point-of-care: preliminary evaluation of a novel technology.

Accurate and rapid point-of-care (PoC) diagnostics are critical to the control of the COVID-19 pandemic. The current standard for accurate diagnosis of SARS-CoV-2 is laboratory-based reverse transcription polymerase chain reaction (RT-PCR) assays. Here, a preliminary prospective performance evaluation of the QuantuMDx Q-POC SARS-CoV-2 RT-PCR assay is reported. Between November 2020 and March 2021, 49 longitudinal combined nose/throat (NT) swabs from 29 individuals hospitalised with RT-PCR confirmed COVID-19 were obtained at St George's Hospital, London. In addition, 101 mid-nasal (MN) swabs were obtained from healthy volunteers in June 2021. These samples were used to evaluate the Q-POC SARS-CoV-2 RT-PCR assay. The primary analysis was to compare the sensitivity and specificity of the Q-POC test against a reference laboratory-based RT-PCR assay. The overall sensitivity of the Q-POC test compared with the reference test was 96.88% (83.78- 99.92% CI) for a cycle threshold (Ct) cut-off value for the reference test of 35 and 80.00% (64.35-90.95% CI) without altering the reference test's Ct cut-off value of 40. The Q-POC test is a sensitive, specific and rapid PoC test for SARS-CoV-2 at a reference Ct cut-off value of 35. The Q-POC test provides an accurate option for RT-PCR at PoC without the need for sample pre-processing and laboratory handling, enabling rapid diagnosis and clinical triage in acute care and other settings.

Production and use of encapsidated RNA mimics as positive control reagents for SARS-CoV-2 RT-qPCR diagnostics.

The current gold standard technique for SARS-CoV-2 diagnostics is hydrolysis probe-based RT-qPCR. Reliable testing requires reliable control reagents to monitor the efficiency of RNA extraction, reverse transcription and PCR amplification. Here we describe a custom RNA packaging system from the plant virus cowpea mosaic virus to produce virus-like particles that encapsidate specifically designed portions of the genome of SARS-CoV-2, the causative agent of COVID-19. These encapsidated mimics are highly stable particles which can be used either to spike patient swab samples for use as an in-tube extraction and reaction positive control in multiplex RT-qPCR, or alone as a side-by-side mock-positive control reagent. The selection of sequences in the packaged pseudogenomes ensures that these mimics are compatible with the most commonly used primer/probe combinations for SARS-CoV-2 diagnostics (including German Berlin Charité Hospital, American CDC, and Chinese CDC protocols). The plant transient expression system used to produce these encapsidated mimics is inherently low-cost, and sufficiently high-yielding that a single laboratory-scale preparation can provide enough positive control reagent for millions of tests.

SARS-CoV-2 enzyme-linked immunosorbent assays as proxies for plaque reduction neutralisation tests.

Severe acute respiratory coronavirus 2 (SARS-CoV-2) has spread globally since its emergence in 2019. Most SARS-CoV-2 infections generate immune responses leading to rising levels of immunoglobulins (Ig) M, A and G which can be detected using diagnostic tests including enzyme-linked immunosorbent assays (ELISA). Whilst implying previous SARS-CoV-2 infection, the detection of Ig by ELISA does not guarantee the presence of neutralising antibodies (NAb) that can prevent the virus infecting cells. Plaque reduction neutralisation tests (PRNT) detect NAb, but are not amenable to mass testing as they take several days and require use of SARS-CoV-2 in high biocontainment laboratories. We evaluated the ability of IgG and IgM ELISAs targeting SARS-CoV-2 spike subunit 1 receptor binding domain (S1-RBD), and spike subunit 2 (S2) and nucleocapsid protein (NP), at predicting the presence and magnitude of NAb determined by PRNT. IgG S2 + NP ELISA was 96.8% [95% CI 83.8-99.9] sensitive and 88.9% [95% CI 51.8-99.7] specific at predicting the presence of NAbs (PRNT80 > 1:40). IgG and IgM S1-RBD ELISAs correlated with PRNT titre, with higher ELISA results increasing the likelihood of a robust neutralising response. The IgM S1-RBD assay can be used as a rapid, high throughput test to approximate the magnitude of NAb titre.