Rapid determination of SARS-CoV-2 antibody neutralization titer using Bio-Rad Bio-Plex correlates strongly with pseudovirus-determined neutralization titer.

Accurate and rapid evaluation of SARS-CoV-2 half-maximal neutralizing antibody (nAb) titer (NT50) is an important research tool for measuring nAb responses after prophylaxis or therapeutics for COVID-19 prevention and management. Compared with ACE2-competitive enzyme immunoassays for nAb detection, pseudovirus assays remain low-throughput and labor intensive. A novel application of the Bio-Rad Bio-Plex Pro Human SARS-CoV-2 D614G S1 Variant nAb Assay was used to determine NT50 from COVID-19-vaccinated individuals and showed strong correlation to a laboratory-developed SARS-CoV-2 pseudovirus nAb assay. The Bio-Plex nAb assay could provide a rapid, high-throughput, culture-free method for NT50 determination in sera.

HIV-1 drug resistance among individuals who seroconverted in the ASPIRE dapivirine ring trial.

INTRODUCTION: A potential concern with the use of dapivirine (DPV) for HIV prevention is the selection of a drug-resistant virus that could spread and reduce the effectiveness of non-nucleoside reverse transcriptase (NNRTI)-based first-line antiretroviral therapy. We evaluated HIV-1 seroconversions in MTN-020/ASPIRE for selection of drug resistance and evaluated the genetic basis for observed reductions in susceptibility to DPV. METHODS: MTN-020/ASPIRE was a placebo-controlled, Phase III safety and effectiveness study of DPV ring for HIV-1 prevention conducted at 15 sites in South Africa, Zimbabwe, Malawi and Uganda between 2012 and 2015. Plasma from individuals who seroconverted in ASPIRE was analysed for HIV-1 drug resistance using both population Sanger sequencing and next-generation sequencing (NGS) with unique molecular identifiers to report mutations at ≥1% frequency. DPV susceptibility of plasma-derived recombinant HIV-1 containing bulk-cloned full-length reverse transcriptase sequences from MTN-020/ASPIRE seroconversions was determined in TZM-bl cells. Statistical significance was calculated using the Fisher's exact test. RESULTS: Plasma from all 168 HIV seroconversions were successfully tested by Sanger sequencing; 57 of 71 DPV arm and 82 of 97 placebo (PLB) arm participants had NGS results at 1% sensitivity. Overall, 18/168 (11%) had NNRTI mutations including K101E, K103N/S, V106M, V108I, E138A/G, V179D/I/T and H221Y. Five samples from both arms had low-frequency NNRTI mutations that were not detected by Sanger sequencing. The frequency of NNRTI mutations from the DPV arm (11%) was not different from the PLB arm (10%; p = 0.80). The E138A mutation was detected in both the DPV (3 of 71 [4.2%]) and PLB arm (5 of 97 [5.2%]) and conferred modest reductions in DPV susceptibility in some reverse transcriptase backgrounds but not others. CONCLUSIONS: HIV-1 drug resistance including NNRTI resistance did not differ between the DPV and placebo arms of the MTN-020/ASPIRE study, indicating that drug resistance was not preferentially acquired or selected by the DPV ring and that the preventive benefit of DPV ring outweighs resistance risk.

Frequent Cross-Resistance to Dapivirine in HIV-1 Subtype C-Infected Individuals after First-Line Antiretroviral Therapy Failure in South Africa.

A vaginal ring containing dapivirine (DPV) has shown moderate protective efficacy against HIV-1 acquisition, but the activity of DPV against efavirenz (EFV)- and nevirapine (NVP)-resistant viruses that could be transmitted is not well defined. We investigated DPV cross-resistance of subtype C HIV-1 from individuals on failing NVP- or EFV-containing antiretroviral therapy (ART) in South Africa. Plasma samples were obtained from individuals with >10,000 copies of HIV RNA/ml and with HIV-1 containing at least one non-nucleoside reverse transcriptase (NNRTI) mutation. Susceptibility to NVP, EFV, and DPV in TZM-bl cells was determined for recombinant HIV-1LAI containing bulk-amplified, plasma-derived, full-length reverse transcriptase sequences. Fold change (FC) values were calculated compared with a composite 50% inhibitory concentration (IC50) from 12 recombinant subtype C HIV-1LAI plasma-derived viruses from treatment-naive individuals in South Africa. A total of 25/100 (25%) samples showed >500-FCs to DPV compared to treatment-naive samples with IC50s exceeding the maximum DPV concentration tested (132 ng/ml). A total of 66/100 (66%) samples displayed 3- to 306-FCs, with a median IC50 of 17.6 ng/ml. Only 9/100 (9%) samples were susceptible to DPV (FC < 3). Mutations L100I and K103N were significantly more frequent in samples with >500-fold resistance to DPV compared to samples with a ≤500-fold resistance. A total of 91% of samples with NNRTI-resistant HIV-1 from individuals on failing first-line ART in South Africa exhibited ≥3-fold cross-resistance to DPV. This level of resistance exceeds expected plasma concentrations, but very high genital tract DPV concentrations from DPV ring use could block viral replication. It is critically important to assess the frequency of transmitted and selected DPV resistance in individuals using the DPV ring.