April Kaur Randhawa

The two parallel antibody-mediated prevention (AMP) efficacy trials evaluated whether intravenous infusion of the anti-CD4 binding site broadly neutralizing antibody VRC01 prevents HIV-1 acquisition. Here, we analyzed HIV-1 acquisition in AMP through the week 104 final study visit. Against viruses considered highly sensitive to VRC01 [80% inhibitory concentration (IC ₈₀ ) < 1 microgram/milliliter], VRC01 prophylaxis maintained cumulative prevention efficacy of 66.3% (95% confidence interval: 32.4, 83.2%), suggesting that the antibody successfully blocked or cleared these infections. In the post–week 80 period (after the final dose at week 72), HIV diagnosis and resistance to VRC01 were more frequent and greater in the VRC01 groups versus placebo. For instance, more HIV diagnoses with viruses considered moderately sensitive or resistant to VRC01 (IC ₈₀ ≥ 5 microgram/milliliter) were made in the VRC01 groups compared with placebo groups (11 versus 1). Plausibly, as in vivo VRC01 concentration waned, suppressed viruses—often evolving greater resistance because of selective pressure—emerged as detectable infections. Our findings suggest that, whereas single antibodies can block sensitive strains, multiple antibodies are likely required to prevent both viral escape and breakthrough infections.

T cell correlates of COVID-19 risk are poorly defined, particularly in people with HIV (PWH). CoVPN 3008 (NCT05168813) Part A was a prospective 14,002-participant cohort study that administered one or two doses of mRNA-1273 COVID-19 vaccine, depending on baseline SARS-CoV-2 serostatus, in participants (83% PWH) in sub-Saharan Africa. Participants self-monitored for prespecified COVID-19 symptoms, defined by Centers for Disease Control and Prevention symptom criteria. Previous work showed that protection from COVID-19 was superior for hybrid versus vaccine-induced immunity, and that neutralizing antibody titers inversely associated with COVID-19 risk. In the present work, we measured T cell responses to Spike and Nucleocapsid at baseline and 4 weeks post last-vaccination (Peak) in a case-cohort study and assessed them as correlates of risk. In Hybrid Group PWH (n = 22 cases), COVID-19 risk over 6 months decreased with increasing Peak Spike BA.4/5-specific CD4 + T cell responses, from 15.8%, 4.7%, and 0% risk at 0.1%, 0.2%, and 0.3% IFN-γ and/or IL-2 response magnitude, respectively. Including baseline Spike-specific neutralizing antibody titer and Peak CD4 + T cell functionality score in the same model increased the association’s strength (overall p < 0.001). Thus, CD4 + T cell responses are an independent correlate of COVID-19 risk among PWH with pre-existing SARS-CoV-2 immunity.

Background: It is challenging to assess SARS-CoV-2 viral kinetics amidst viral variant evolution and changes in population-level immunity. However, understanding the relationship between host factors and viral replication deepens our understanding of viral fitness. Methods: In CoVPN 5001, we enrolled N = 953 adults diagnosed with acute SARS-CoV-2 from July 2020 to July 2022 across 51 sites. We confirmed SARS-CoV-2 infection by RT-PCR and identified the variant via viral genome sequencing. Using multivariable linear regression and median regression, we studied the association between host factors and either observed peak viral load (VL) or clinical viral shedding, respectively, accounting for viral variant effects in a demographically and clinically diverse longitudinal cohort. Results: In this observational study, we determine that while host factors, including age, BMI, sex, medical comorbidities, and HIV, have no significant associations with either observed peak VL or clinical viral shedding in the nasopharynx, viral variant is significantly associated with observed peak VL and clinical viral shedding. We show that neither observed peak VL nor shedding duration predict evolutionary success since the dominant variants in the SARS-CoV-2 pandemic did not all align with the variants with the highest peak and longest shedding duration. Conclusions: Altogether, our work shows that observed peak VL and shedding duration should be cautiously interpreted as predictors of viral fitness.

Background: We previously showed that ancestral-specific anti-Spike binding IgG concentration and 50% inhibitory dilution neutralizing antibody titer (nAb-ID50) measured at 2 weeks postdose 2 (∼peak) were inverse correlates of risk (CoRs) of COVID-19 over 2 months post ∼peak in the PREVENT-19 trial of the NVX-CoV2373 vaccine; there were not sufficient data to assess CoRs of severe COVID-19. Methods: Here, we assessed, in the same vaccinated cohort, Delta- and ancestral-specific Spike IgG and nAb-ID50 at ∼peak and over time as CoRs of severe COVID-19 and of Delta COVID-19 over 3.5–10 months post ∼peak (287 breakthrough Delta cases, including 8 severe; 446 noncases). Results: Peak antibody levels were much higher for noncases versus severe cases (all inferred Delta), with nAb-ID50 Delta geometric mean 209.5 arbitrary units (AU)/mL (95% CI: 176.1, 249.1) versus 9.6 AU/mL (95% CI: 2.4, 38.6), respectively. Frequency of detectable nAb-ID50 titer was 98.3% (97.2, 99.0) for noncases versus 62.5% (22.3, 93.9) for severe cases. All markers were inverse CoRs of severe COVID-19, with a ∼peak hazard ratio (HR) of 0.13 (95% CI: .03, .57) per 10-fold nAb-ID50 Delta increase. Severe COVID-19 risk through 305 days postday 35 was 0.0338 (0.0043, 0.206) at the nAb-ID50 Delta 2.5th percentile (8.4 AU/mL), and 0.002 (0.0000, 0.0108) and 0.0002 (0.0000, 0.0035) at the 50th and 95th percentiles (210, 2522 AU/mL). Conclusions: Postvaccination NVX-CoV2373 antibody levels are stronger predictors of severe COVID-19 than any-severity Delta COVID-19. Low antibody responses indicate vulnerability to severe COVID-19.

People with HIV (PWH) are understudied in COVID-19 vaccine trials, leaving knowledge gaps on whether the identified immune correlates of protection also hold in PWH. CoVPN 3008 (NCT05168813) enrolled predominantly PWH and reported lower COVID-19 incidence for a Hybrid vs. Vaccine Group (baseline SARS-CoV-2-positive and one mRNA-1273 dose vs. negative and two doses). Using case-cohort sampling, antibody markers at enrolment (M0) and four weeks post-final vaccination (Peak) are assessed as immune correlates of COVID-19. For the Hybrid Group [n = 287 (195 PWH)], all M0 markers inversely correlate with COVID-19 through 230 days post-Peak, with 50% inhibitory dilution BA.4/5 neutralizing antibody titer (nAb-ID50 BA.4/5) the strongest and only independent correlate (HR per 10-fold increase=0.46, 95% CI 0.28, 0.75; P = 0.002). For the Vaccine Group [n = 115 (86 PWH)], Peak nAb-ID50 BA.4/5 correlates with reduced COVID-19 risk (1.9%, 1.1%, and 0.3% at titers 10, 100, and 1000 AU/ml) through 92, but not 165, days post-Peak. Using multivariable Cox analysis of binding and nAb, nAb titers predict COVID-19 in PWH. Two doses of a 100-µg Ancestral strain mRNA vaccine in baseline-SARS-CoV-2-negative individuals elicit sufficient cross-reacting Omicron antibodies to reduce COVID-19 incidence for 90 days post-Peak, but viral evolution and waning antibodies abrogate this protection thereafter.

Background: SARS-CoV-2 infection results in greater disease severity among immunocompromised individuals compared to healthy individuals. However, there is conflicting information about the impact of chronic HIV infection on immune responses to SARS-CoV-2 infection and vaccination. Method: We used a combination of machine learning approaches and network analysis to explore 56 immune markers and comprehensively profile humoral and cellular immunity in a cross-sectional observational cohort of people without HIV (PWOH; n = 216) and people living with HIV (PLWH; n = 43) who recovered from SARS-CoV-2 infection (13–131 days since SARS-COV-2 diagnosis) early in the pandemic. Results: PLWH recovered from symptomatic outpatient COVID-19 exhibit lower humoral and B cell responses to SARS-CoV-2 vs. PWOH but, surprisingly, both symptomatic outpatient and hospitalized PLWH have higher anti-endemic coronavirus antibody responses compared to PWOH counterparts and asymptomatic PLWH. The latter observation suggests that this was not strictly due to broadly elevated levels of anti-endemic coronavirus antibodies in PLWH. Moreover, correlation-based analysis reveals that while different compartments of the immune response to SARS-CoV-2 infection are positively correlated in PWOH recovered from symptomatic outpatient COVID-19, these correlations are weaker in PLWH. Conclusion: Our analyses reveal significant differences in the coordinated immune responses elicited by infection in PLWH compared to PWOH.

Assessment of immune correlates of severe COVID-19 has been hampered by the low numbers of severe cases in COVID-19 vaccine efficacy (VE) trials. We assess neutralizing and binding antibody levels at 4 weeks post-Ad26.COV2.S vaccination as correlates of risk and of protection against severe-critical COVID-19 through 220 days post-vaccination in the ENSEMBLE trial (NCT04505722), constituting ~4.5 months longer follow-up than our previous correlates analysis and enabling inclusion of 42 severe-critical vaccine-breakthrough cases. Neutralizing antibody titer is a strong inverse correlate of severe-critical COVID-19, with estimated hazard ratio (HR) per 10-fold increase 0.35 (95% CI: 0.13, 0.90). In a multivariable model, HRs are 0.31 (0.11, 0.89) for neutralizing antibody titer and 1.22 (0.49, 3.02) for anti-Spike binding antibody concentration. VE against severe-critical COVID-19 rises with neutralizing antibody titer: 63.1% (95% CI: 40.0%, 77.3%) at unquantifiable [th percentile (30.2 IU50/ml). At the same titers, VE against moderate COVID-19 is 32.5% (11.8%, 48.4%), 33.9% (19.1%, 59.3%), and 60.7% (40.4%, 76.4%). Protection against moderate vs. severe disease may require higher antibody levels, and very low antibody levels and/or other immune responses may associate with protection against severe disease.

In the phase 3 trial of the AZD1222 (ChAdOx1 nCoV-19) vaccine conducted in the U.S., Chile, and Peru, anti-spike binding IgG concentration (spike IgG) and pseudovirus 50% neutralizing antibody titer (nAb ID50) measured four weeks after two doses were assessed as correlates of risk and protection against PCR-confirmed symptomatic SARS-CoV-2 infection (COVID-19). These analyses of SARS-CoV-2 negative participants were based on case-cohort sampling of vaccine recipients (33 COVID-19 cases by 4 months post dose two, 463 non-cases). The adjusted hazard ratio of COVID-19 was 0.32 (95% CI: 0.14, 0.76) per 10-fold increase in spike IgG concentration and 0.28 (0.10, 0.77) per 10-fold increase in nAb ID50 titer. At nAb ID50 below the limit of detection (< 2.612 IU50/ml), 10, 100, and 270 IU50/ml, vaccine efficacy was −5.8% (−651%, 75.6%), 64.9% (56.4%, 86.9%), 90.0% (55.8%, 97.6%) and 94.2% (69.4%, 99.1%). These findings provide further evidence towards defining an immune marker correlate of protection to help guide regulatory/approval decisions for COVID-19 vaccines.

In the PREVENT-19 phase 3 trial of the NVX-CoV2373 vaccine (NCT04611802), anti-spike binding IgG concentration (spike IgG), anti-RBD binding IgG concentration (RBD IgG), and pseudovirus 50% neutralizing antibody titer (nAb ID50) measured two weeks post-dose two are assessed as correlates of risk and as correlates of protection against COVID-19. Analyses are conducted in the U.S. cohort of baseline SARS-CoV-2 negative per-protocol participants using a case-cohort design that measures the markers from all 12 vaccine recipient breakthrough COVID-19 cases starting 7 days post antibody measurement and from 639 vaccine recipient non-cases. All markers are inversely associated with COVID-19 risk and directly associated with vaccine efficacy. In vaccine recipients with nAb ID50 titers of 50, 100, and 7230 international units (IU50)/ml, vaccine efficacy estimates are 75.7% (49.8%, 93.2%), 81.7% (66.3%, 93.2%), and 96.8% (88.3%, 99.3%). The results support potential cross-vaccine platform applications of these markers for guiding decisions about vaccine approval and use.