Development of a Diagnostic Programmed Cell Death 1-Ligand 1 Immunohistochemistry Assay for Nivolumab Therapy in Melanoma.

Nivolumab is a monoclonal antibody that blocks the interaction between programmed cell death 1 (PD1) and programmed cell death 1-ligand 1 (PD-L1), resulting in enhanced antitumor activity by the immune system. Nivolumab is currently approved by the US Food and Drug Administration (FDA) for melanoma, non-small cell lung cancer (NSCLC), renal cell carcinoma, classical Hodgkin lymphoma, squamous cell carcinoma of the head and neck, and urothelial carcinoma. PD-L1 IHC 28-8 pharmDx is FDA-approved as a complementary diagnostic for immunohistochemical (IHC) detection of PD-L1 in non-squamous NSCLC and melanoma. We report validation of PD-L1 IHC 28-8 pharmDx for PD-L1 detection on formalin-fixed, paraffin-embedded human melanoma specimens using Autostainer Link 48. A prevalence assessment of 104 melanoma specimens indicated that PD-L1 was detected across the full expression level range (0% to 100% of tumor cells). Assay robustness and precision studies were conducted at Agilent Technologies, with additional reproducibility studies performed at 3 external laboratories. Precision studies evaluated at ≥1% and ≥5% expression levels revealed a range of average negative agreement from 89.5%, 95% CI (83.2, 93.6) to 100%, 95% CI (97.3, 100), and average positive agreement from 85.5%, 95% CI (77.6, 90.9) to 100%, 95% CI (97.9, 100). For external reproducibility, precise results were obtained. These results demonstrate PD-L1 IHC 28-8 pharmDx is a precise, robust, and reproducible assay for determining PD-L1 expression in melanoma. This is the first PD-L1 IHC test to receive FDA approval as a complementary diagnostic in melanoma patients whereby positive PD-L1 expression is correlated with the magnitude of nivolumab treatment effect.

Analytical Validation of the ReEBOV Antigen Rapid Test for Point-of-Care Diagnosis of Ebola Virus Infection.

BACKGROUND: Ebola virus disease (EVD) is a severe viral illness caused by Ebola virus (EBOV). The 2013-2016 EVD outbreak in West Africa is the largest recorded, with >11 000 deaths. Development of the ReEBOV Antigen Rapid Test (ReEBOV RDT) was expedited to provide a point-of-care test for suspected EVD cases. METHODS: Recombinant EBOV viral protein 40 antigen was used to derive polyclonal antibodies for RDT and enzyme-linked immunosorbent assay development. ReEBOV RDT limits of detection (LOD), specificity, and interference were analytically validated on the basis of Food and Drug Administration (FDA) guidance. RESULTS: The ReEBOV RDT specificity estimate was 95% for donor serum panels and 97% for donor whole-blood specimens. The RDT demonstrated sensitivity to 3 species of Ebolavirus (Zaire ebolavirus, Sudan ebolavirus, and Bundibugyo ebolavirus) associated with human disease, with no cross-reactivity by pathogens associated with non-EBOV febrile illness, including malaria parasites. Interference testing exhibited no reactivity by medications in common use. The LOD for antigen was 4.7 ng/test in serum and 9.4 ng/test in whole blood. Quantitative reverse transcription-polymerase chain reaction testing of nonhuman primate samples determined the range to be equivalent to 3.0 × 105-9.0 × 108 genomes/mL. CONCLUSIONS: The analytical validation presented here contributed to the ReEBOV RDT being the first antigen-based assay to receive FDA and World Health Organization emergency use authorization for this EVD outbreak, in February 2015.

Field Validation of the ReEBOV Antigen Rapid Test for Point-of-Care Diagnosis of Ebola Virus Infection.

BACKGROUND: The 2013-2016 West African Ebola virus disease (EVD) epidemic is the largest recorded. Triage on the basis of clinical signs had limited success, and the time to diagnosis by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) could exceed 5 days. Here we describe the development and field validation of the ReEBOV Antigen Rapid Test (ReEBOV RDT) to aid triage of individuals with suspected EVD. METHODS: Samples from patients with suspected EVD were submitted to Kenema Government Hospital, Sierra Leone, for Lassa fever and EVD screening throughout 2014. Banked residual clinical samples were tested in November 2014 and January 2015 in a blinded field trial to estimate the clinical effectiveness of the ReEBOV RDT, compared with EBOV-specific qRT-PCR. RESULTS: Preliminary ReEBOV RDT performance demonstrated a positive percentage agreement (PPA) of 91.1% (195 of 214 results; 95% confidence interval [CI], 86.5%-94.6%) and a negative percentage agreement (NPA) of 90.2% (175 of 194; 95% CI, 85.1%-94.0%). The final estimates used by the Food and Drug Administration to determine whether to grant emergency use authorization for the test, which excluded a qRT-PCR reference method threshold cutoff, were a PPA of 62.1% (72 of 116 results; 95% CI, 52.6%-70.9%) and a NPA of 96.7% (58 of 60; 95% CI, 88.5%-99.6%), with a diagnostic likelihood of 18.6. A subsequent, independent evaluation by the World Health Organization generated results consistent with the preliminary performance estimates. CONCLUSIONS: The ReEBOV RDT demonstrated the potential to provide clinically effective rapid and accurate point-of-care test results and, thus, to be a powerful tool for increasing triage efficiency.

Lassa Virus Seroprevalence in Sibirilia Commune, Bougouni District, Southern Mali.

Lassa virus (LASV) is endemic to several nations in West Africa. In Mali, LASV was unknown until an exported case of Lassa fever was reported in 2009. Since that time, rodent surveys have found evidence of LASV-infected Mastomys natalensis rats in several communities in southern Mali, near the border with Côte d'Ivoire. Despite increased awareness, to date only a single case of Lassa fever has been confirmed in Mali. We conducted a survey to determine the prevalence of LASV exposure among persons in 3 villages in southern Mali where the presence of infected rodents has been documented. LASV IgG seroprevalence ranged from 14.5% to 44% per village. No sex bias was noted; however, seropositivity rates increased with participant age. These findings confirm human LASV exposure in Mali and suggest that LASV infection/Lassa fever is a potential public health concern in southern Mali.

Development of Prototype Filovirus Recombinant Antigen Immunoassays.

BACKGROUND: Throughout the 2014-2015 Ebola outbreak in West Africa, major gaps were exposed in the availability of validated rapid diagnostic platforms, protective vaccines, and effective therapeutic agents. These gaps potentiated the development of prototype rapid lateral flow immunodiagnostic (LFI) assays that are true point-of-contact platforms, for the detection of active Ebola infections in small blood samples. METHODS: Recombinant Ebola and Marburg virus matrix VP40 and glycoprotein (GP) antigens were used to derive a panel of monoclonal and polyclonal antibodies. Antibodies were tested using a multivariate approach to identify antibody-antigen combinations suitable for enzyme-linked immunosorbent assay (ELISA) and LFI assay development. RESULTS: Polyclonal antibodies generated in goats were superior reagents for capture and detection of recombinant VP40 in test sample matrices. These antibodies were optimized for use in antigen-capture ELISA and LFI assay platforms. Prototype immunoglobulin M (IgM)/immunoglobulin G (IgG) ELISAs were similarly developed that specifically detect Ebola virus-specific antibodies in the serum of experimentally infected nonhuman primates and in blood samples obtained from patients with Ebola from Sierra Leone. CONCLUSIONS: The prototype recombinant Ebola LFI assays developed in these studies have sensitivities that are useful for clinical diagnosis of acute ebolavirus infections. The antigen-capture and IgM/IgG ELISAs provide additional confirmatory assay platforms for detecting VP40 and other ebolavirus-specific immunoglobulins.