Christian Hofmann

University of California, Los Angeles | UCLA · Division of Infectious Diseases

Background: Although mRNA vaccines have overall efficacy preventing morbidity/mortality from SARS-CoV-2 infection, immunocompromised persons remain at risk. Antibodies mostly prevent early symptomatic infection, but cellular immunity, particularly the virus-specific CD8+ T cell response, is protective against disease. Defects in T cell responses t...

Introduction While antibodies raised by SARS-CoV-2 mRNA vaccines have had compromised efficacy to prevent breakthrough infections due to both limited durability and spike sequence variation, the vaccines have remained highly protective against severe illness. This protection is mediated through cellular immunity, particularly CD8+ T cells, and last...

CD8⁺ T cells have key protective roles in many viral infections. While an overall Th1-biased cellular immune response against SARS-CoV-2 has been demonstrated, most reports of anti-SARS-CoV-2 cellular immunity have evaluated bulk T cells using pools of predicted epitopes, without clear delineation of the CD8⁺ subset and its magnitude and targeting....

As SARS-CoV-2 evolves to become better suited for circulating in humans, mutations have occurred in the spike protein it uses for attaching to cells it infects. Protective antibodies from prior infection or vaccination target the spike protein to interfere with its function.

Two mRNA vaccines (BNT162b2 and mRNA-1273) against severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) are globally authorized as a two-dose regimen. Understanding the magnitude and duration of protective immune responses is vital to curbing the pandemic. We enrolled 461 high-risk health services workers at the University of California, Lo...

SARS-CoV-2 continues to evolve in humans. Spike protein mutations increase transmission and potentially evade antibodies raised against the original sequence used in current vaccines. Our evaluation of serum neutralizing activity in both persons soon after SARS-CoV-2 infection (in April 2020 or earlier) or vaccination without prior infection confir...

Mammalian cell transfection is a powerful technique commonly used in molecular biology to express exogenous DNA or RNA in cells and study gene and protein function. Although several transfection strategies have been developed, there is a wide variation with regards to transfection efficiency, cell toxicity and reproducibility. Thus, a sensitive and...

Objective: To assess whether weakly recognized epitope variants induce anergy in HIV-1-specific CD8 T lymphocyte (CTL) clones as a mechanism of dysfunction. Design: HIV-1-specific CTL clones were exposed to suboptimally recognized epitope variants, and screened for anergy and other T-cell dysfunction markers, and subsequent capability to kill ta...

Transfection is one of the most frequently used techniques in molecular biology that is also applicable for gene therapy studies in humans. One of the biggest challenges to investigate the protein function and interaction in gene therapy studies is to have reliable monospecific detection reagents, particularly antibodies, for all human gene product...

Author summary Certain MHC class I types are associated with superior immune containment of HIV-1, underscoring the importance of CD8⁺ cytotoxic T lymphocytes (CTLs). Epitope escape mutations for these types is limited, indicating reduced immune evasion. Two proposed mechanisms are: 1) CTL targeting of highly sequence-constrained epitopes, or 2) mo...

CTLs utilized in this study suppress HIV-1 replication. T1 cells were infected with HIV-1 NL4-3.1 (with the subtype B consensus SL9 epitope sequence) and co-cultured with CTL clone 1.9, followed by monitoring of supernatant p24 antigen. Results are plotted for viral replication in the presence (closed triangles) or absence (open circles) of CTL co-...

Numbers of SL9 epitope variants attaining various thresholds for enrichment by CTLs. For each epitope variant (including immediately flanking residues) with initial library frequencies above 10−4 in both replicates, first columns indicate relative enrichment versus consensus without CTLs (RE-CTL), second columns indicate relative enrichment with ad...

Numbers of KF11 epitope variants attaining various thresholds for enrichment by CTLs. For each epitope variant (including immediately flanking residues) with initial library frequencies above 10−4 in both replicates, first columns indicate relative enrichment versus consensus without CTLs (RE-CTL), second columns indicate relative enrichment with a...

Numbers of KK10 epitope variants attaining various thresholds for enrichment by CTLs. For each epitope variant (including immediately flanking residues) with initial library frequencies above 10−4 in both replicates, first columns indicate relative enrichment versus consensus without CTLs (RE-CTL), second columns indicate relative enrichment with a...

Schematic describing the passaging of HIV-1 epitope mutant virus libraries under selective pressure from CTLs. Plasmid libraries created as described in Fig 1 were transfected into 293T cells to produce starting virus libraries, which were then passaged in the presence or absence of CTLs for two consecutive rounds of 7 days each. Deep sequencing of...

HIV-1 epitope variants with stop codons generally decay during passaging of the epitope variant libraries. For each stop codon present above a threshold frequency of 10−4 in the starting virus library, the frequency over time after passaging in the absence of CTLs is plotted. Each value represents the average of experimental duplicates for each lib...

Objectives: Strategies to cure HIV-1-infection require the eradication of viral reservoirs. An innovative approach for boosting the cytotoxic T lymphocyte response is the transfer of T-cell receptors (TCRs). Previously, we have shown that electroporation of TCR-encoding mRNA is able to reprogram CD8 T-cells derived from healthy donors. So far, it...

There is an error in the first sentence under the subheading Study Subject, in the Materials and Methods section. The correct sentence is: A 27 year-old woman (HLA A1, B8, B72, DR8, DR17, DQ2, and DQ4) was the recipient of a right hand from a male donor (HLA A2, A11, B35, B51, DR4, DR7, DQ2, and DQ8).

Immune prophylaxis and treatment of transplanted tissue rejection act indiscriminately, risking serious infections and malignancies. Although animal data suggest that cellular immune responses causing rejection may be rather narrow and predictable based on genetic background, there are only limited data regarding the clonal breadth of anti-donor re...

Human adenovirus infection is life threatening after allogeneic haematopoietic stem cell transplantation (HSCT). Immunotherapy with donor-derived adenovirus-specific T cells is promising; however, 20% of all donors lack adenovirus-specific T cells. To overcome this, we transfected α/β T cells with mRNA encoding a T-cell receptor (TCR) specific for...

Human adenovirus infection is life threatening after allogeneic haematopoietic stem cell transplantation (HSCT). Immunotherapy with donor-derived adenovirus-specific T cells is promising; however, 20% of all donors lack adenovirus-specific T cells. To overcome this, we transfected alpha/beta T cells with mRNA encoding a T-cell receptor (TCR) specif...

Efficient monitoring of HIV-1-specific T-cells is crucial for the development of HIV-1 vaccines and immunotherapies. Currently, mainly peptides and vaccinia vectors are used for detection of HIV-1-specific cytotoxic T-lymphocytes (CTL), however, as HIV-1 is a variable virus, it is unknown to what extent the T-cell response against the autologous vi...

Adoptive TCR transfer against rapidly mutating targets, such as HIV-1 or cancer, must counteract corresponding immune escape. Hence, we generated T cells expressing two additional receptors (TETARs) specific for HIV-1 by TCR mRNA electroporation. An HLA-A2-restricted gag-specific TCR and an HLA-B13-restricted nef-specific TCR were chosen. When both...

Sequencing, cloning and functional testing of T-cell-receptor (TCR) alpha- and beta-chains from T-cell clones is often required in immunotherapy and in immunological research. However, the determination of the TCR chains by a simple PCR is not possible, since, in contrast to the 3' constant domain and untranslated region (UTR), no conserved sequenc...

Human immunodeficiency virus type 1 (HIV-1) gene expression and replication are regulated by the promoter/enhancer located in the U3 region of the proviral 5′ long terminal repeat (LTR). The binding of cellular transcription factors to specific regulatory sites in the 5′ LTR is a key event in the replication cycle of HIV-1. Since transcriptional ac...

HIV-1-specific cytotoxic T lymphocytes, which recognize conserved epitopes of the virus, are correlated with prolonged survival of infected individuals. Unfortunately, most HIV-1-infected patients are unable to generate such an immune response. Antigen-specific cytotoxic T lymphocytes can be generated by T-cell receptor transfer. This is commonly d...