Preclinical efficacy, safety, and immunogenicity of PHH-1V, a second-generation COVID-19 vaccine, in non-human primates

SARS-CoV-2 emerged in December 2019 and quickly spread worldwide, continuously striking with an unpredictable evolution. Despite the success in vaccine production and mass vaccination programmes, the situation is not still completely controlled, and therefore accessible second-generation vaccines are required to mitigate the pandemic. We previously developed an adjuvanted vaccine candidate coded PHH-1V, based on a heterodimer fusion protein comprising the RBD domain of two SARS-CoV-2 variants. Here, we report data on the efficacy, safety, and immunogenicity of PHH-1V in cynomolgus macaques. PHH-1V prime-boost vaccination induces high levels of RBD-specific IgG and IgA binding and neutralising antibodies against several SARS-CoV-2 variants of concern, as well as a balanced Th1/Th2 cellular immune response. Remarkably, PHH-1V vaccination prevents SARS-CoV-2 replication in the lower respiratory tract and significantly reduces viral load in the upper respiratory tract after an experimental infection. These results highlight the potential use of the PHH-1V vaccine in humans, currently undergoing Phase III clinical trials.

Demonstration of antibodies against SARS-CoV-2, neutralizing or binding, in seroconversion panels after mRNA-1273, BNT-162b2 and Ad26.COV2.S vaccine administration.

Seroconversion panels were collected before and after vaccination with three COVID-19 vaccines: two mRNA vaccines (mRNA-1273 and BNT-162b2) and one adenovirus vector vaccine (Ad26.COV2.S). The panels were tested for antibody activity by chemiluminescent immunoassay, ELISA and one was tested in a pseudovirus neutralization assay. Participants positive for anti-SARS-CoV-2 antibodies before vaccination (18.6%) had a higher response to the first vaccine dose than participants who tested negative. For two-dose vaccines, older participants showed a lower response to the first dose than younger participants. All participants showed positive antibody responses after the second vaccine. For the adenovirus vector vaccine, two participants did not generate antibody responses two weeks and two months after vaccination. Three participants were negative at two weeks but positive at two months. Pseudovirus neutralization showed good correlation with antibody activity (correlation coefficient =0.78, p<0.0001). Antibody responses in participants over 45 years old tended to be less robust.

Cross-sectional study to assess the efficacy of SARS-CoV-2 vaccination in patients with monoclonal gammopathies

SARS-CoV-2 vaccination is the most effective strategy to protect patients with haematologic malignancies against severe COVID-19, but primary vaccine responses are less effective in this population. Here, we characterized the humoral responses following 3 months after mRNA-based vaccines in patients at different stages of the same plasma cell diseases, including monoclonal gammopathy of undetermined significance (MGUS), smoldering multiple myeloma (SMM) and multiple myeloma on first line therapy (MM), compared to a healthy control population matched by sex and age. We observed that plasmas from uninfected MM patients after 3 months post-vaccine have lower SARS-CoV-2 specific IgG and IgA antibodies and decreased neutralization capacity compared with MGUS and SMM individuals, and a group of healthy controls. Importantly, we detected significantly higher plasma neutralization capacity in MM individuals who recovered from COVID-19 compared to their uninfected counterparts, highlighting that hybrid immunity elicit stronger immune responses even in this immunocompromised population. In contrast to MM group, no differences in the vaccine-induced humoral response were observed between uninfected MGUS, SMM and healthy individuals. In conclusion, a booster vaccine dose is recommended in uninfected MM patients to develop an adequate and effective humoral response to SARS-CoV-2 vaccine.

Limited immune responses after three months of BNT162b2 vaccine in SARS-CoV-2 uninfected elders living in long-term care facilities

BackgroundSARS-CoV-2 vaccination is the most effective strategy to protect elders living in long-term care facilities (LTCF) against severe COVID-19, but primary vaccine responses are less effective in older adults. Here, we characterized the humoral responses following 3 months after mRNA/BNT162b2 vaccine in institutionalized elders. MethodsPlasma levels of specific SARS-CoV-2 total IgG, IgM and IgA antibodies were measured before and 3 months after vaccination in elders living in LTCF. Neutralization capacity was assessed in a pseudovirus neutralization assay against WH1 (original) and B.1.617.2/Delta variants. A group of younger adults was used as reference group. ResultsThree months after vaccination, uninfected-elders presented reduced specific SARS-CoV-2 IgG levels and significantly lower neutralization capacity against the WH1 and Delta virus compared to vaccinated uninfected younger individuals. In contrast, COVID-19 recovered elders showed significantly higher specific SARS-CoV-2 IgG levels after vaccination than younger counterparts, while showing similar neutralization activity against WH1 virus and increased neutralization capacity against Delta variant. Despite previously infected elders elicit potent cross-reactive immune responses similarly to younger individuals, higher quantities of specific SARS-CoV-2 IgG antibodies are required to reach the same neutralization levels. ConclusionsWhile hybrid immunity seems to be active in previously infected elders after three months from mRNA/BNT162b2 vaccination, humoral immune responses are diminished in COVID-19 uninfected vaccinated residents living in LTCF. These results suggests that a vaccine booster dose should be prioritized for this particularly vulnerable population. Word summaryWhile previously infected and vaccinated elders living in LTCF had comparable neutralizing antibody levels to younger individuals, vaccinated uninfected-residents showed limited neutralization capacity against both original and delta variants. Hybrid immunity seems to be active in elders and can be relevant to design vaccine boosting campaigns.

Preclinical efficacy, safety, and immunogenicity of PHH-1V, a second-generation COVID-19 vaccine candidate based on a novel recombinant RBD fusion heterodimer of SARS-CoV-2.

The current COVID-19 vaccines have been associated with a decline in infection rates, prevention of severe disease and decrease in mortality rates. However, new variants of concern (VoCs) are continuously evolving, making the development of new accessible COVID-19 vaccines essential in order to mitigate the pandemic. Here we present data on preclinical studies in mice of a receptor-binding domain (RBD)-based recombinant protein vaccine candidate (PHH-1V) consisting of an RBD fusion heterodimer containing the B.1.351 and B.1.1.7 SARS-CoV-2 VoCs and formulated with the SQBA adjuvant, an oil-in-water emulsion produced by HIPRA. BALB/c and K18-hACE2 mice were immunized with different recombinant RBD fusion heterodimer doses, following a two-dose prime-and-boost schedule. Vaccination induced a CD4+ and CD8+ T cell response and RBD-binding antibodies with neutralising activity against various VoCs with a good tolerability profile. Significantly, a 10-{micro}g or 20-{micro}g RBD fusion heterodimer/dose vaccination conferred 100% efficacy, preventing mortality in SARS-CoV-2 infected K18-hACE2 mice. These findings demonstrate the feasibility of this recombinant vaccine strategy.

Clinical course impacts early kinetics and long-term magnitude and amplitude of SARS-CoV-2 neutralizing antibodies beyond one year after infection

BackgroundUnderstanding the determinants of long-term immune responses to SARS-CoV-2 and the concurrent impact of vaccination and emerging variants of concern will guide optimal strategies to achieve global protection against the COVID-19 pandemic. MethodsA prospective cohort of 332 COVID-19 patients was followed beyond one year. Plasma neutralizing activity was evaluated using HIV-based reporter pseudoviruses expressing different SARS-CoV-2 spikes and was longitudinally analyzed using mixed-effects models. FindingsLong-term neutralizing activity was stable beyond one year after infection in mild/asymptomatic and hospitalized participants. However, longitudinal models suggest that hospitalized individuals generate both short- and long-lived memory B cells, while outpatient responses were dominated by long-lived B cells. In both groups, vaccination boosted responses to natural infection, although viral variants, mainly B.1.351, reduced the efficacy of neutralization. Importantly, despite showing higher neutralization titers, hospitalized patients showed lower cross-neutralization of B.1.351 variant compared to outpatients. Multivariate analysis identified severity of primary infection as the factor that independently determines both the magnitude and the inferior cross-neutralization activity of long-term neutralizing responses. ConclusionsNeutralizing response induced by SARS-CoV-2 is heterogeneous in magnitude but stable beyond one year after infection. Vaccination boosts these long-lasting natural neutralizing responses, counteracting the significant resistance to neutralization of new viral variants. Severity of primary infection determines higher magnitude but poorer quality of long-term neutralizing responses.

Previous SARS-CoV-2 infection increases B.1.1.7 cross-neutralization by vaccinated individuals.

To assess the potential impact of predominant circulating SARS-CoV-2 variants on neutralizing activity of infected and/or vaccinated individuals, we analyzed neutralization of pseudoviruses expressing the spike of the original Wuhan strain, the D614G and B.1.1.7 variants. Our data show that parameters of natural infection (time from infection and infecting variant) determined cross-neutralization. Importantly, upon vaccination, previously infected individuals developed equivalent B.1.1.7 and Wuhan neutralizing responses. In contrast, uninfected vaccinees showed reduced neutralization against B.1.1.7. FundingThis study was funded by Grifols, the Departament de Salut of the Generalitat de Catalunya, the Spanish Health Institute Carlos III, CERCA Programme/Generalitat de Catalunya, and the crowdfunding initiatives #joemcorono, BonPreu/Esclat and Correos.

Stable neutralizing antibody levels six months after mild and severe COVID-19 episode

Understanding mid-term kinetics of immunity to SARS-CoV-2 is the cornerstone for public health control of the pandemic and vaccine development. However, current evidence is rather based on limited measurements, thus losing sight of the temporal pattern of these changes1-6. In this longitudinal analysis, conducted on a prospective cohort of COVID-19 patients followed up to 242 days, we found that individuals with mild or asymptomatic infection experienced an insignificant decay in neutralizing activity that persisted six months after symptom onset or diagnosis. Hospitalized individuals showed higher neutralizing titers, which decreased following a two-phase pattern, with an initial rapid decline that significantly slowed after day 80. Despite this initial decay, neutralizing activity at six months remained higher among hospitalized individuals. The slow decline in neutralizing activity at mid-term contrasted with the steep slope of antibody titers change, reinforcing the hypothesis that the quality of immune response evolves over the post-convalescent stage4,5.