Biology subjects

Sachithanandham, J.

Publications and source records attributed to Sachithanandham, J..

4 recordsLinked to original sources

bioRxiv2024

A Third COVID-19 Vaccine Dose in Kidney Transplant Recipients Induces Antibody Response to Vaccine and Omicron Variants but Shows Limited Ig Subclass Switching

Solid organ transplant recipients (SOTRs) suffer more frequent and more severe infections due to their compromised immune responses resulting from immunosuppressive treatments designed to prevent organ rejection. Pharmacological immunosuppression can adversely affect immune responses to vaccination. A cohort of kidney transplant recipients (KTRs) received their third dose of ancestral, monovalent COVID-19 vaccine in the context of a clinical trial and antibody responses to the vaccine strain, as well as to Omicron variants BA.1 and BA.5 were investigated and compared with healthy controls. Total IgG and live virus neutralizing antibody titers were reduced in KTRs compared to controls for all variants. KTRs displayed altered IgG subclass switching, with significantly lower IgG3 antibodies. Responses in KTRs were also very heterogeneous, with some individuals showing strong responses but a significant number showing no Omicron-specific neutralizing antibodies. Taken together, immune responses after COVID-19 vaccination in KTRs were not only lower than healthy controls but highly variable, indicating that simply increasing the number of vaccine doses alone may not be sufficient to provide greater protection in this population. ImportanceThis study addresses the challenges faced by kidney transplant recipients (KTRs) in mounting effective immune responses against COVID-19. By evaluating the antibody responses to a third dose of monovalent mRNA COVID-19 vaccine and its effectiveness against Omicron subvariants (BA.1 and BA.5), this study reveals significant reductions in both binding and neutralizing antibodies in KTRs compared to healthy controls. The research highlights altered IgG subclass switching and heterogeneous responses within the KTR population. Reduced recognition of variants, coupled with differences in IgG subclasses, decreases both the quality and quantity of protective antibodies after vaccination in KTRs. These findings underscore the need for tailored vaccination strategies for immunosuppressed populations such as KTRs. Alternative formulations and doses of COVID-19 vaccines should be considered for people with severely compromised immune systems, as more frequent vaccinations may not significantly improve the response, especially regarding neutralizing antibodies.

immunology↗

bioRxiv2024

SARS-CoV-2 variants from long-term, persistently infected immunocompromised patients have altered syncytia formation, temperature-dependent replication, and serum neutralizing antibody escape

SARS-CoV-2 infection of immunocompromised individuals often leads to prolonged detection of viral RNA and infectious virus in nasal specimens, presumably due to the lack of induction of an appropriate adaptive immune response. Mutations identified in virus sequences obtained from persistently infected patients bear signatures of immune evasion and have some overlap with sequences present in variants of concern. We characterized virus isolates from two COVID-19 patients undergoing immunosuppressive cancer therapy, with all isolates obtained greater than 100 days after the initial COVID-19 diagnoses and compared to an isolate from the start of the infection. Isolates from an individual who never mounted an antibody response specific to SARS-CoV-2 despite the administration of convalescent plasma showed slight reductions in plaque size and some showed temperature-dependent replication attenuation on human nasal epithelial cell culture compared to the virus that initiated infection. An isolate from another patient - who did mount a SARS-CoV-2 IgM response - showed temperature dependent changes in plaque size as well as increased syncytia formation and escape from serum neutralizing antibody. Our results indicate that not all virus isolates from immunocompromised COVID-19 patients display clear signs of phenotypic change, but increased attention should be paid to monitoring virus evolution in this patient population.

microbiology↗

bioRxiv2024

Antigen-display exosomes provide adjuvant-free protection against SARS-CoV-2 disease at nanogram levels of spike protein

As the only bionormal nanovesicle, exosomes have high potential as a nanovesicle for delivering vaccines and therapeutics. We show here that the loading of type-1 membrane proteins into the exosome membrane is induced by exosome membrane anchor domains, EMADs, that maximize protein delivery to the plasma membrane, minimize protein sorting to other compartments, and direct proteins into exosome membranes. Using SARS-CoV-2 spike as an example and EMAD13 as our most effective exosome membrane anchor, we show that cells expressing a spike-EMAD13 fusion protein produced exosomes that carry dense arrays of spike trimers on 50% of all exosomes. Moreover, we find that immunization with spike-EMAD13 exosomes induced strong neutralizing antibody responses and protected hamsters against SARS-CoV-2 disease at doses of just 0.5-5 ng of spike protein, without adjuvant, demonstrating that antigen-display exosomes are particularly immunogenic, with important implications for both structural and expression-dependent vaccines.

bioengineering↗

bioRxiv2023

Convergent Evolution of A-Lineage (Clade 19B) SARS-CoV-2 Spike Sequences with B-Lineage Variants of Concern Affects Virus Replication in a Temperature-Dependent Manner on Human Nasal Epithelial Cell Cultures

The first three months of the COVID-19 pandemic was dominated by two SARS-CoV-2 lineages: A-lineages (Clade 19B) and B-lineages (Clade 19A). However, with the emergence of the Spike D614G substitution in B.1 lineages (Clade 20A), both early lineages were outcompeted and remained near-extinction from mid-2020 onwards. In early-2021, there was a re-emergence and persistence of novel A-lineage variants with substitutions in the Spike gene resembling those found in Variants of Concern (VOCs). An early A.3 variant (MD-HP00076/2020) and three A.2.5 variants (MD-HP02153/2021, MD-HP05922/2021 and CA-VRLC091/2021) were isolated and characterized for their genomic sequences, antibody neutralization, and in vitro replication. All A.2.5 isolates had five Spike mutations relative to the A.3 variant sequence: D614G, L452R, {Delta}141-143, D215A, and ins215AGY. Plaque reduction neutralization assays demonstrated that A.2.5 isolates had a 2.5 to 5-fold reduction in neutralization using contemporaneous COVID-19 convalescent plasma when compared to A.3. In vitro viral characterization in VeroE6 cell lines revealed that the A.3 isolate grew faster and spread more than A.2.5. On VeroE6-TMPRSS2 cells, significant syncytia formation was also observed with the A.2.5 isolates, however Spike cleavage efficiency did not explain these differences. In human nasal epithelial cell (hNEC) cultures, the A.2.5 isolates grew significantly faster and to higher total infectious virus titers than A.3. All A.2.5 lineage isolates grew significantly faster at 37{degrees}C than at 33{degrees}C irrespective of cell type, and to higher peak titers except compared to A.3. This suggests A.2.5s adapted to improve replication using similar mutations found in the B-lineage SARS-CoV-2 variants. ImportanceWhile both A- and B-lineage SARS-CoV-2 variants emerged and circulated together during the early months of the pandemic, the B-lineages that acquired Spike D614G eventually outcompeted all other variants. We show that the A-lineage variants eventually evolved mutations including Spike D614G and Spike L452R that improved their in vitro replication in human nasal epithelial cells in a temperature dependent manner, suggesting there are some highly selectable mutation landscapes that SARS-CoV-2 can acquire to adapt to replication and transmission in humans.

microbiology↗