Consistent neutralization of circulating omicron sub-variants by hybrid immunity up to 6 months after booster vaccination.

The current COVID-19 vaccination program requires frequent booster vaccination to maintain sufficient neutralization levels against immune evasive SARS-CoV-2 variants. However, prior studies found more potent and durable immune response in convalescing individuals, raising the possibility of less frequent booster vaccination for them. Here, we conducted a longitudinal immunological study based on two prospective cohorts of booster vaccinated convalescing COVID-19 patients or healthcare workers (HCW) without COVID-19 history in Xiangyang, China. Comparing to 1-month post-boosting, pseudovirus neutralization titers (pVNT50) of ancestral Wuhan-Hu-1 and circulating omicron sub-variants BA.5, BF.7, BA.4.6, BA.2.75, and BA.2.75.2 spikes were stable or even increased in convalescing samples at 6-month post-boosting, when HCW samples showed substantial drop of neutralization titers across the spectrum. Variant-to-Wuhan-Hu-1 pVNT50 ratios showed no significant variation during the 17 months from pre-vaccination to 6-month post-boosting in convalescing individuals, indicating that the high durability of hybrid immunity was likely sustained by continuously improving neutralization potency that compensated immune decay. Our data provide mechanistic insight into prior epidemiological findings that vaccine-elicited humoral immune response was more durable in convalescing individuals than those without SARS-CoV-2 infection, and suggest further research into potential extension of boosting intervals for convalescing individuals.

Vaccine-elicited CD8+ T cells cure mesothelioma by overcoming tumor-induced immunosuppressive environment.

Eradicating malignant tumors by vaccine-elicited host immunity remains a major medical challenge. To date, correlates of immune protection remain unknown for malignant mesothelioma. In this study, we demonstrated that antigen-specific CD8(+) T-cell immune response correlates with the elimination of malignant mesothelioma by a model PD-1-based DNA vaccine. Unlike the nonprotective tumor antigen WT1-based DNA vaccines, the model vaccine showed complete and long-lasting protection against lethal mesothelioma challenge in immunocompetent BALB/c mice. Furthermore, it remained highly immunogenic in tumor-bearing animals and led to therapeutic cure of preexisting mesothelioma. T-cell depletion and adoptive transfer experiments revealed that vaccine-elicited CD8(+) T cells conferred to the protective efficacy in a dose-dependent way. Also, these CD8(+) T cells functioned by releasing inflammatory IFNγ and TNFα in the vicinity of target cells as well as by initiating TRAIL-directed tumor cell apoptosis. Importantly, repeated DNA vaccinations, a major advantage over live-vectored vaccines with issues of preexisting immunity, achieve an active functional state, not only preventing the rise of exhausted PD-1(+) and Tim-3(+) CD8(+) T cells but also suppressing tumor-induced myeloid-derived suppressive cells and Treg cells, with the frequency of antigen-specific CD8(+) T cells inversely correlating with tumor mass. Our results provide new insights into quantitative and qualitative requirements of vaccine-elicited functional CD8(+) T cells in cancer prevention and immunotherapy.

PD1-based DNA vaccine amplifies HIV-1 GAG-specific CD8+ T cells in mice.

Viral vector-based vaccines that induce protective CD8+ T cell immunity can prevent or control pathogenic SIV infections, but issues of preexisting immunity and safety have impeded their implementation in HIV-1. Here, we report the development of what we believe to be a novel antigen-targeting DNA vaccine strategy that exploits the binding of programmed death-1 (PD1) to its ligands expressed on dendritic cells (DCs) by fusing soluble PD1 with HIV-1 GAG p24 antigen. As compared with non-DC-targeting vaccines, intramuscular immunization via electroporation (EP) of the fusion DNA in mice elicited consistently high frequencies of GAG-specific, broadly reactive, polyfunctional, long-lived, and cytotoxic CD8+ T cells and robust anti-GAG antibody titers. Vaccination conferred remarkable protection against mucosal challenge with vaccinia GAG viruses. Soluble PD1-based vaccination potentiated CD8+ T cell responses by enhancing antigen binding and uptake in DCs and activation in the draining lymph node. It also increased IL-12-producing DCs and engaged antigen cross-presentation when compared with anti-DEC205 antibody-mediated DC targeting. The high frequency of durable and protective GAG-specific CD8+ T cell immunity induced by soluble PD1-based vaccination suggests that PD1-based DNA vaccines could potentially be used against HIV-1 and other pathogens.

CCR5 antagonist TD-0680 uses a novel mechanism for enhanced potency against HIV-1 entry, cell-mediated infection, and a resistant variant.

Regardless of the route of transmission, R5-tropic HIV-1 predominates early in infection, rendering C-C chemokine receptor type 5 (CCR5) antagonists as attractive agents not only for antiretroviral therapy but also for prevention. Here, we report the specificity, potency, and underlying mechanism of action of a novel small molecule CCR5 antagonist, TD-0680. TD-0680 displayed the greatest potency against a diverse group of R5-tropic HIV-1 and SIV strains when compared with its prodrug, TD-0232, the Food and Drug Administration-approved CCR5 antagonist Maraviroc, and TAK-779, with EC(50) values in the subnanomolar range (0.09-2.29 nm). Importantly, TD-0680 was equally potent at blocking envelope-mediated cell-cell fusion and cell-mediated viral transmission as well as the replication of a TAK-779/Maraviroc-resistant HIV-1 variant. Interestingly, TD-0232 and TD-0680 functioned differently despite binding to a similar transmembrane pocket of CCR5. Site-directed mutagenesis, drug combination, and antibody blocking assays identified a novel mechanism of action of TD-0680. In addition to binding to the transmembrane pocket, the unique exo configuration of this molecule protrudes and sterically blocks access to the extracellular loop 2 (ECL2) region of CCR5, thereby interrupting the interaction between virus and its co-receptor more effectively. This mechanism of action was supported by the observations of similar TD-0680 potency against CD4-dependent and -independent SIV strains and by molecular docking analysis using a CCR5 model. TD-0680, therefore, merits development as an anti-HIV-1 agent for therapeutic purposes and/or as a topical microbicide for the prevention of sexual transmission of R5-tropic HIV-1.

Viral interleukin-10 expressed by human cytomegalovirus during the latent phase of infection modulates latently infected myeloid cell differentiation.

The human cytomegalovirus UL111A gene is expressed during latent and productive infections, and it codes for homologs of interleukin-10 (IL-10). We examined whether viral IL-10 expressed during latency altered differentiation of latently infected myeloid progenitors. In comparison to infection with parental virus or mock infection, latent infection with a virus in which the gene encoding viral IL-10 has been deleted upregulated cytokines associated with dendritic cell (DC) formation and increased the proportion of myeloid DCs. These data demonstrate that viral IL-10 restricts the ability of latently infected myeloid progenitors to differentiate into DCs and identifies an immunomodulatory role for viral IL-10 which may limit the host's ability to clear latent virus.

The role of the human cytomegalovirus UL111A gene in down-regulating CD4+ T-cell recognition of latently infected cells: implications for virus elimination during latency.

The capacity of human cytomegalovirus (HCMV) to establish and maintain a latent infection from which it can later reactivate ensures its widespread distribution in the population, but the mechanisms enabling maintenance of latency in the face of a robust immune system are poorly understood. We examined the role of the HCMV UL111A gene, which encodes homologs of the immunosuppressive cytokine interleukin-10 in the context of latent infection of myeloid progenitor cells. A UL111A deletion virus was able to establish, maintain, and reactivate from experimental latency in a manner comparable with parental virus, but major histocompatibility complex class II levels increased significantly on the surfaces of cells infected with the deletion virus. Importantly, there was an increase in both allogeneic and autologous peripheral blood mononuclear cells and CD4(+) T-cell responses to UL111A deletion virus-infected myeloid progenitors, indicating that loss of the capacity to express viral interleukin-10 during latency results in latently infected cells becoming more readily recognizable by a critical arm of the immune response. The detection of a viral gene that suppresses CD4(+) T-cell recognition of latently infected cells identifies an immune evasion strategy that probably enhances the capacity of HCMV to persist in a latent state within the human host.

Microarrays for the study of viral gene expression during human cytomegalovirus latent infection.

Human cytomegalovirus (HCMV) is one of the largest known DNA viruses. It is ubiquitous, and following resolution of primary productive infection, it persists in the human host by establishing a lifelong latent infection in myeloid lineage cells such as monocytes and their progenitors. Most adults with HCMV infection are healthy but it can cause neurologic deficits in infants, and remains an important cause of morbidity and mortality in the immunosuppressed patient. Microarray-based studies of HCMV have provided useful information about genes that are transcriptionally active during both productive and latent phases of infection. This chapter describes how to study genes in HCMV using microarrays and two cell types (productively infected human foreskin fibroblasts, and latently infected primary human myeloid progenitor cells).

Viral gene expression during the establishment of human cytomegalovirus latent infection in myeloid progenitor cells.

Human cytomegalovirus (HCMV) establishes and maintains a latent infection in myeloid cells and can reactivate to cause serious disease in allograft recipients. To better understand the molecular events associated with the establishment of latency, we tracked the virus following infection of primary human myeloid progenitor cells at days 1, 2, 3, 5, and 11. At all time points, the viral genome was maintained in most cells at approximately 10 copies. Infectious virus was not detected, but virus could be reactivated by extended fibroblast coculture. In contrast to wild-type HCMV, the viral genome was rapidly lost from myeloid progenitors infected with ultraviolet (UV)-inactivated virus, suggesting viral gene expression was required for efficient establishment of latency. To identify viral genes associated with the establishment phase, RNA from each time point was interrogated using custom-made HCMV gene microarrays. Using this approach, we detected expression of viral RNAs at all time points. The pattern of expression differed from that which occurs during productive infection, and decreased over time. This study provides evidence that a molecular pathway into latency is associated with expression of a unique subset of viral transcripts. Viral genes expressed during the establishment phase may serve as targets for therapies to interrupt this process.