Vaccine-elicited CD4 T cells prevent the deletion of antiviral B cells in chronic infection

A virus-like particle candidate vaccine based on CRISPR/Cas9 gene editing technology elicits broad-spectrum protection against SARS-CoV-2

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants with frequent mutations has seriously damaged the effectiveness of the 2019 coronavirus disease (COVID-19) vaccine. There is an urgent need to develop a broad-spectrum vaccine while elucidating the underlying immune mechanisms. Here, we developed a SARS-CoV-2 virus-like particles (VLPs) vaccine based on the Canarypox-virus vector (ALVAC-VLPs) using CRISPR/Cas9. Immunization with ALVAC-VLPs showed the effectively induce SARS-CoV-2 specific T and B cell responses to resist the lethal challenge of mouse adaptive strains. Notably, ALVAC-VLPs conferred protection in golden hamsters against SARS-CoV-2 Wuhan-Hu-1 (wild-type, WT) and variants (Beta, Delta, Omicron BA.1, and BA.2), as evidenced by the prevention of weight loss, reduction in lung and turbinate tissue damage, and decreased viral load. Further investigation into the mechanism of immune response induced by ALVAC-VLPs revealed that toll-like receptor 4 (TLR4) mediates the recruitment of dendritic cells (DCs) to secondary lymphoid organs, thereby initiating follicle assisted T (Tfh) cell differentiation, the proliferation of germinal center (GC) B cells and plasma cell production. These findings demonstrate the immunogenicity and efficacy of the safe ALVAC-VLPs vaccine against SARS-CoV-2 and provide valuable insight into the development of COVID-19 vaccine strategies.

Central tolerance shapes the neutralizing B cell repertoire against a persisting virus in its natural host

Viral mimicry of host cell structures has been postulated to curtail the B cell receptor (BCR) repertoire against persisting viruses through tolerance mechanisms. This concept awaits, however, experimental testing in a setting of natural virus-host relationship. We engineered mouse models expressing a monoclonal BCR specific for the envelope glycoprotein of lymphocytic choriomeningitis virus (LCMV), a naturally persisting mouse pathogen. When the heavy chain of the LCMV-neutralizing antibody KL25 was paired with its unmutated ancestor light chain, most B cells underwent receptor editing, a behavior reminiscent of autoreactive clones. In contrast, monoclonal B cells expressing the same heavy chain in conjunction with the hypermutated KL25 light chain did not undergo receptor editing but exhibited low levels of surface IgM, suggesting that light chain hypermutation had lessened KL25 autoreactivity. Upon viral challenge, these IgMlow cells were not anergic but up-regulated IgM, participated in germinal center reactions, produced antiviral antibodies, and underwent immunoglobulin class switch as well as further affinity maturation. These studies on a persisting virus in its natural host species suggest that central tolerance mechanisms prune the protective antiviral B cell repertoire.

An advanced comprehensive muti-cell-type-specific model for predicting anti-PD-1 therapeutic effect in melanoma

Rationale: Immune checkpoint inhibitors targeting the programmed cell death (PD)-1/PD-L1 pathway have promise in patients with advanced melanoma. However, drug resistance usually results in limited patient benefits. Recent single-cell RNA sequencing studies have elucidated that MM patients display distinctive transcriptional features of tumor cells, immune cells and interstitial cells, including loss of antigen presentation function of tumor cells, exhaustion of CD8+T and extracellular matrix secreted by fibroblasts to prevents immune infiltration, which leads to a poor response to immune checkpoint inhibitors (ICIs). However, cell subgroups beneficial to anti-tumor immunity and the model developed by them remain to be further identified. Methods: In this clinical study of neoadjuvant therapy with anti-PD-1 in advanced melanoma, tumor tissues were collected before and after treatment for single-nucleus sequencing, and the results were verified using multicolor immunofluorescence staining and public datasets. Results: This study describes four cell subgroups which are closely associated with the effectiveness of anti-PD-1 treatment. It also describes a cell-cell communication network, in which the interaction of the four cell subgroups contributes to anti-tumor immunity. Furthermore, we discuss a newly developed predictive model based on these four subgroups that holds significant potential for assessing the efficacy of anti-PD-1 treatment. Conclusions: These findings elucidate the primary mechanism of anti-PD-1 resistance and offer guidance for clinical drug administration for melanoma.

Multiantigen pan-sarbecovirus DNA vaccines generate protective T cell immune responses

SARS-CoV-2 is the third zoonotic coronavirus to cause a major outbreak in humans in recent years, and many more SARS-like coronaviruses with pandemic potential are circulating in several animal species. Vaccines inducing T cell immunity against broadly conserved viral antigens may protect against hospitalization and death caused by outbreaks of such viruses. We report the design and preclinical testing of 2 T cell-based pan-sarbecovirus vaccines, based on conserved regions within viral proteins of sarbecovirus isolates of human and other carrier animals, like bats and pangolins. One vaccine (CoVAX_ORF1ab) encoded antigens derived from nonstructural proteins, and the other (CoVAX_MNS) encoded antigens from structural proteins. Both multiantigen DNA vaccines contained a large set of antigens shared across sarbecoviruses and were rich in predicted and experimentally validated human T cell epitopes. In mice, the multiantigen vaccines generated both CD8+ and CD4+ T cell responses to shared epitopes. Upon encounter of full-length spike antigen, CoVAX_MNS-induced CD4+ T cells were responsible for accelerated CD8+ T cell and IgG Ab responses specific to the incoming spike, irrespective of its sarbecovirus origin. Finally, both vaccines elicited partial protection against a lethal SARS-CoV-2 challenge in human angiotensin-converting enzyme 2-transgenic mice. These results support clinical testing of these universal sarbecovirus vaccines for pandemic preparedness.

Adoptive B cell therapy for chronic viral infection

T cell-based therapies have been widely explored for the treatment of cancer and chronic infection, but B cell-based therapies have remained largely unexplored. To study the effect of B cell therapy, we adoptively transferred virus-specific B cells into mice that were chronically infected with lymphocytic choriomeningitis virus (LCMV). Adoptive transfer of virus-specific B cells resulted in increase in antibody titers and reduction of viral loads. Importantly, the efficacy of B cell therapy was partly dependent on antibody effector functions, and was improved by co-transferring virus-specific CD4 T cells. These findings provide a proof-of-concept that adoptive B cell therapy can be effective for the treatment of chronic infections, but provision of virus-specific CD4 T cells may be critical for optimal virus neutralization.