Mpox infection protects against re-challenge in rhesus macaques.

The mpox outbreak of 2022-2023 involved rapid global spread in men who have sex with men. We infected 18 rhesus macaques with mpox by the intravenous, intradermal, and intrarectal routes and observed robust antibody and T cell responses following all three routes of infection. Numerous skin lesions and high plasma viral loads were observed following intravenous and intradermal infection. Skin lesions peaked on day 10 and resolved by day 28 following infection. On day 28, we re-challenged all convalescent and 3 naive animals with mpox. All convalescent animals were protected against re-challenge. Transcriptomic studies showed upregulation of innate and inflammatory responses and downregulation of collagen formation and extracellular matrix organization following challenge, as well as rapid activation of T cell and plasma cell responses following re-challenge. These data suggest key mechanistic insights into mpox pathogenesis and immunity. This macaque model should prove useful for evaluating mpox vaccines and therapeutics.

Vaccine protection against the SARS-CoV-2 Omicron variant in macaques.

The rapid spread of the SARS-CoV-2 Omicron (B.1.1.529) variant, including in highly vaccinated populations, has raised important questions about the efficacy of current vaccines. In this study, we show that the mRNA-based BNT162b2 vaccine and the adenovirus-vector-based Ad26.COV2.S vaccine provide robust protection against high-dose challenge with the SARS-CoV-2 Omicron variant in cynomolgus macaques. We vaccinated 30 macaques with homologous and heterologous prime-boost regimens with BNT162b2 and Ad26.COV2.S. Following Omicron challenge, vaccinated macaques demonstrated rapid control of virus in bronchoalveolar lavage, and most vaccinated animals also controlled virus in nasal swabs. However, 4 vaccinated animals that had moderate Omicron-neutralizing antibody titers and undetectable Omicron CD8+ T cell responses failed to control virus in the upper respiratory tract. Moreover, virologic control correlated with both antibody and T cell responses. These data suggest that both humoral and cellular immune responses contribute to vaccine protection against a highly mutated SARS-CoV-2 variant.

Low-dose Ad26.COV2.S protection against SARS-CoV-2 challenge in rhesus macaques.

We previously reported that a single immunization with an adenovirus serotype 26 (Ad26)-vector-based vaccine expressing an optimized SARS-CoV-2 spike (Ad26.COV2.S) protected rhesus macaques against SARS-CoV-2 challenge. To evaluate reduced doses of Ad26.COV2.S, 30 rhesus macaques were immunized once with 1 × 1011, 5 × 1010, 1.125 × 1010, or 2 × 109 viral particles (vp) Ad26.COV2.S or sham and were challenged with SARS-CoV-2. Vaccine doses as low as 2 × 109 vp provided robust protection in bronchoalveolar lavage, whereas doses of 1.125 × 1010 vp were required for protection in nasal swabs. Activated memory B cells and binding or neutralizing antibody titers following vaccination correlated with protective efficacy. At suboptimal vaccine doses, viral breakthrough was observed but did not show enhancement of disease. These data demonstrate that a single immunization with relatively low dose of Ad26.COV2.S effectively protected against SARS-CoV-2 challenge in rhesus macaques, although a higher vaccine dose may be required for protection in the upper respiratory tract.

PD-1 signaling limits expression of phospholipid phosphatase 1 and promotes intratumoral CD8+ T cell ferroptosis.

The tumor microenvironment (TME) promotes metabolic reprogramming and dysfunction in immune cells. Here, we examined the impact of the TME on phospholipid metabolism in CD8+ T cells. In lung cancer, phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were lower in intratumoral CD8+ T cells than in circulating CD8+ T cells. Intratumoral CD8+ T cells exhibited decreased expression of phospholipid phosphatase 1 (PLPP1), which catalyzes PE and PC synthesis. T cell-specific deletion of Plpp1 impaired antitumor immunity and promoted T cell death by ferroptosis. Unsaturated fatty acids in the TME stimulated ferroptosis of Plpp1-/- CD8+ T cells. Mechanistically, programmed death-1 (PD-1) signaling in CD8+ T cells induced GATA1 binding to the promoter region Plpp1 and thereby suppressed Plpp1 expression. PD-1 blockade increased Plpp1 expression and restored CD8+ T cell antitumor function but did not rescue dysfunction of Plpp1-/- CD8+ T cells. Thus, PD-1 signaling regulates phospholipid metabolism in CD8+ T cells, with therapeutic implications for immunotherapy.

Zika Virus Persistence in the Central Nervous System and Lymph Nodes of Rhesus Monkeys.

Zika virus (ZIKV) is associated with severe neuropathology in neonates as well as Guillain-Barré syndrome and other neurologic disorders in adults. Prolonged viral shedding has been reported in semen, suggesting the presence of anatomic viral reservoirs. Here we show that ZIKV can persist in cerebrospinal fluid (CSF) and lymph nodes (LN) of infected rhesus monkeys for weeks after virus has been cleared from peripheral blood, urine, and mucosal secretions. ZIKV-specific neutralizing antibodies correlated with rapid clearance of virus in peripheral blood but remained undetectable in CSF for the duration of the study. Viral persistence in both CSF and LN correlated with upregulation of mechanistic target of rapamycin (mTOR), proinflammatory, and anti-apoptotic signaling pathways, as well as downregulation of extracellular matrix signaling pathways. These data raise the possibility that persistent or occult neurologic and lymphoid disease may occur following clearance of peripheral virus in ZIKV-infected individuals.

Rapid Inflammasome Activation following Mucosal SIV Infection of Rhesus Monkeys.

The earliest events following mucosal HIV-1 infection, prior to measurable viremia, remain poorly understood. Here, by detailed necropsy studies, we show that the virus can rapidly disseminate following mucosal SIV infection of rhesus monkeys and trigger components of the inflammasome, both at the site of inoculation and at early sites of distal virus spread. By 24 hr following inoculation, a proinflammatory signature that lacked antiviral restriction factors was observed in viral RNA-positive tissues. The early innate response included expression of NLRX1, which inhibits antiviral responses, and activation of the TGF-ß pathway, which negatively regulates adaptive immune responses. These data suggest a model in which the virus triggers specific host mechanisms that suppress the generation of antiviral innate and adaptive immune responses in the first few days of infection, thus facilitating its own replication. These findings have important implications for the development of vaccines and other strategies to prevent infection.

Mucosal boosting enhances vaccine protection against SARS-CoV-2 in macaques.

A limitation of current SARS-CoV-2 vaccines is that they provide minimal protection against infection with current Omicron subvariants1,2, although they still provide protection against severe disease. Enhanced mucosal immunity may be required to block infection and onward transmission. Intranasal administration of current vaccines has proven inconsistent3-7, suggesting that alternative immunization strategies may be required. Here we show that intratracheal boosting with a bivalent Ad26-based SARS-CoV-2 vaccine results in substantial induction of mucosal humoral and cellular immunity and near-complete protection against SARS-CoV-2 BQ.1.1 challenge. A total of 40 previously immunized rhesus macaques were boosted with a bivalent Ad26 vaccine by the intramuscular, intranasal and intratracheal routes, or with a bivalent mRNA vaccine by the intranasal route. Ad26 boosting by the intratracheal route led to a substantial expansion of mucosal neutralizing antibodies, IgG and IgA binding antibodies, and CD8+ and CD4+ T cell responses, which exceeded those induced by Ad26 boosting by the intramuscular and intranasal routes. Intratracheal Ad26 boosting also led to robust upregulation of cytokine, natural killer, and T and B cell pathways in the lungs. After challenge with a high dose of SARS-CoV-2 BQ.1.1, intratracheal Ad26 boosting provided near-complete protection, whereas the other boosting strategies proved less effective. Protective efficacy correlated best with mucosal humoral and cellular immune responses. These data demonstrate that these immunization strategies induce robust mucosal immunity, suggesting the feasibility of developing vaccines that block respiratory viral infections.

Protective efficacy of a global HIV-1 mosaic vaccine against heterologous SHIV challenges in rhesus monkeys.

The global diversity of HIV-1 represents a critical challenge facing HIV-1 vaccine development. HIV-1 mosaic antigens are bioinformatically optimized immunogens designed for improved coverage of HIV-1 diversity. However, the protective efficacy of such global HIV-1 vaccine antigens has not previously been evaluated. Here, we demonstrate the capacity of bivalent HIV-1 mosaic antigens to protect rhesus monkeys against acquisition of infection following heterologous challenges with the difficult-to-neutralize simian-human immunodeficiency virus SHIV-SF162P3. Adenovirus/poxvirus and adenovirus/adenovirus vector-based vaccines expressing HIV-1 mosaic Env, Gag, and Pol afforded a significant reduction in the per-exposure acquisition risk following repetitive, intrarectal SHIV-SF162P3 challenges. Protection against acquisition of infection correlated with vaccine-elicited binding, neutralizing, and functional nonneutralizing antibodies, suggesting that the coordinated activity of multiple antibody functions may contribute to protection against difficult-to-neutralize viruses. These data demonstrate the protective efficacy of HIV-1 mosaic antigens and suggest a potential strategy for the development of a global HIV-1 vaccine. PAPERCLIP:

Vaccines elicit highly conserved cellular immunity to SARS-CoV-2 Omicron.

The highly mutated SARS-CoV-2 Omicron (B.1.1.529) variant has been shown to evade a substantial fraction of neutralizing antibody responses elicited by current vaccines that encode the WA1/2020 spike protein1. Cellular immune responses, particularly CD8+ T cell responses, probably contribute to protection against severe SARS-CoV-2 infection2-6. Here we show that cellular immunity induced by current vaccines against SARS-CoV-2 is highly conserved to the SARS-CoV-2 Omicron spike protein. Individuals who received the Ad26.COV2.S or BNT162b2 vaccines demonstrated durable spike-specific CD8+ and CD4+ T cell responses, which showed extensive cross-reactivity against both the Delta and the Omicron variants, including in central and effector memory cellular subpopulations. Median Omicron spike-specific CD8+ T cell responses were 82-84% of the WA1/2020 spike-specific CD8+ T cell responses. These data provide immunological context for the observation that current vaccines still show robust protection against severe disease with the SARS-CoV-2 Omicron variant despite the substantially reduced neutralizing antibody responses7,8.

Optimization of non-coding regions for a non-modified mRNA COVID-19 vaccine.

The CVnCoV (CureVac) mRNA vaccine for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) was recently evaluated in a phase 2b/3 efficacy trial in humans1. CV2CoV is a second-generation mRNA vaccine containing non-modified nucleosides but with optimized non-coding regions and enhanced antigen expression. Here we report the results of a head-to-head comparison of the immunogenicity and protective efficacy of CVnCoV and CV2CoV in non-human primates. We immunized 18 cynomolgus macaques with two doses of 12 µg lipid nanoparticle-formulated CVnCoV or CV2CoV or with sham (n = 6 per group). Compared with CVnCoV, CV2CoV induced substantially higher titres of binding and neutralizing antibodies, memory B cell responses and T cell responses as well as more potent neutralizing antibody responses against SARS-CoV-2 variants, including the Delta variant. Moreover, CV2CoV was found to be comparably immunogenic to the BNT162b2 (Pfizer) vaccine in macaques. Although CVnCoV provided partial protection against SARS-CoV-2 challenge, CV2CoV afforded more robust protection with markedly lower viral loads in the upper and lower respiratory tracts. Binding and neutralizing antibody titres were correlated with protective efficacy. These data demonstrate that optimization of non-coding regions can greatly improve the immunogenicity and protective efficacy of a non-modified mRNA SARS-CoV-2 vaccine in non-human primates.

Immunogenicity of Ad26.COV2.S vaccine against SARS-CoV-2 variants in humans.

The Ad26.COV2.S vaccine1-3 has demonstrated clinical efficacy against symptomatic COVID-19, including against the B.1.351 variant that is partially resistant to neutralizing antibodies1. However, the immunogenicity of this vaccine in humans against SARS-CoV-2 variants of concern remains unclear. Here we report humoral and cellular immune responses from 20 Ad26.COV2.S vaccinated individuals from the COV1001 phase I-IIa clinical trial2 against the original SARS-CoV-2 strain WA1/2020 as well as against the B.1.1.7, CAL.20C, P.1 and B.1.351 variants of concern. Ad26.COV2.S induced median pseudovirus neutralizing antibody titres that were 5.0-fold and 3.3-fold lower against the B.1.351 and P.1 variants, respectively, as compared with WA1/2020 on day 71 after vaccination. Median binding antibody titres were 2.9-fold and 2.7-fold lower against the B.1.351 and P.1 variants, respectively, as compared with WA1/2020. Antibody-dependent cellular phagocytosis, complement deposition and natural killer cell activation responses were largely preserved against the B.1.351 variant. CD8 and CD4 T cell responses, including central and effector memory responses, were comparable among the WA1/2020, B.1.1.7, B.1.351, P.1 and CAL.20C variants. These data show that neutralizing antibody responses induced by Ad26.COV2.S were reduced against the B.1.351 and P.1 variants, but functional non-neutralizing antibody responses and T cell responses were largely preserved against SARS-CoV-2 variants. These findings have implications for vaccine protection against SARS-CoV-2 variants of concern.

Correlates of protection against SARS-CoV-2 in rhesus macaques.

Recent studies have reported the protective efficacy of both natural1 and vaccine-induced2-7 immunity against challenge with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in rhesus macaques. However, the importance of humoral and cellular immunity for protection against infection with SARS-CoV-2 remains to be determined. Here we show that the adoptive transfer of purified IgG from convalescent rhesus macaques (Macaca mulatta) protects naive recipient macaques against challenge with SARS-CoV-2 in a dose-dependent fashion. Depletion of CD8+ T cells in convalescent macaques partially abrogated the protective efficacy of natural immunity against rechallenge with SARS-CoV-2, which suggests a role for cellular immunity in the context of waning or subprotective antibody titres. These data demonstrate that relatively low antibody titres are sufficient for protection against SARS-CoV-2 in rhesus macaques, and that cellular immune responses may contribute to protection if antibody responses are suboptimal. We also show that higher antibody titres are required for treatment of SARS-CoV-2 infection in macaques. These findings have implications for the development of SARS-CoV-2 vaccines and immune-based therapeutic agents.

Protective efficacy of Ad26.COV2.S against SARS-CoV-2 B.1.351 in macaques.

The emergence of SARS-CoV-2 variants that partially evade neutralizing antibodies poses a threat to the efficacy of current COVID-19 vaccines1,2. The Ad26.COV2.S vaccine expresses a stabilized spike protein from the WA1/2020 strain of SARS-CoV-2, and has recently demonstrated protective efficacy against symptomatic COVID-19 in humans in several geographical regions-including in South Africa, where 95% of sequenced viruses in cases of COVID-19 were the B.1.351 variant3. Here we show that Ad26.COV2.S elicits humoral and cellular immune responses that cross-react with the B.1.351 variant and protects against B.1.351 challenge in rhesus macaques. Ad26.COV2.S induced lower binding and neutralizing antibodies against B.1.351 as compared to WA1/2020, but elicited comparable CD8 and CD4 T cell responses against the WA1/2020, B.1.351, B.1.1.7, P.1 and CAL.20C variants. B.1.351 infection of control rhesus macaques resulted in higher levels of virus replication in bronchoalveolar lavage and nasal swabs than did WA1/2020 infection. Ad26.COV2.S provided robust protection against both WA1/2020 and B.1.351, although we observed higher levels of virus in vaccinated macaques after B.1.351 challenge. These data demonstrate that Ad26.COV2.S provided robust protection against B.1.351 challenge in rhesus macaques. Our findings have important implications for vaccine control of SARS-CoV-2 variants of concern.

Elicitation of Robust Tier 2 Neutralizing Antibody Responses in Nonhuman Primates by HIV Envelope Trimer Immunization Using Optimized Approaches.

The development of stabilized recombinant HIV envelope trimers that mimic the virion surface molecule has increased enthusiasm for a neutralizing antibody (nAb)-based HIV vaccine. However, there is limited experience with recombinant trimers as immunogens in nonhuman primates, which are typically used as a model for humans. Here, we tested multiple immunogens and immunization strategies head-to-head to determine their impact on the quantity, quality, and kinetics of autologous tier 2 nAb development. A bilateral, adjuvanted, subcutaneous immunization protocol induced reproducible tier 2 nAb responses after only two immunizations 8 weeks apart, and these were further enhanced by a third immunization with BG505 SOSIP trimer. We identified immunogens that minimized non-neutralizing V3 responses and demonstrated that continuous immunogen delivery could enhance nAb responses. nAb responses were strongly associated with germinal center reactions, as assessed by lymph node fine needle aspiration. This study provides a framework for preclinical and clinical vaccine studies targeting nAb elicitation.

Single-shot Ad26 vaccine protects against SARS-CoV-2 in rhesus macaques.

A safe and effective vaccine for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may be required to end the coronavirus disease 2019 (COVID-19) pandemic1-8. For global deployment and pandemic control, a vaccine that requires only a single immunization would be optimal. Here we show the immunogenicity and protective efficacy of a single dose of adenovirus serotype 26 (Ad26) vector-based vaccines expressing the SARS-CoV-2 spike (S) protein in non-human primates. Fifty-two rhesus macaques (Macaca mulatta) were immunized with Ad26 vectors that encoded S variants or sham control, and then challenged with SARS-CoV-2 by the intranasal and intratracheal routes9,10. The optimal Ad26 vaccine induced robust neutralizing antibody responses and provided complete or near-complete protection in bronchoalveolar lavage and nasal swabs after SARS-CoV-2 challenge. Titres of vaccine-elicited neutralizing antibodies correlated with protective efficacy, suggesting an immune correlate of protection. These data demonstrate robust single-shot vaccine protection against SARS-CoV-2 in non-human primates. The optimal Ad26 vector-based vaccine for SARS-CoV-2, termed Ad26.COV2.S, is currently being evaluated in clinical trials.

Current advances in bacteria-based cancer immunotherapy.

As the understanding of the tumor microenvironment has deepened, immunotherapy has become a promising strategy for cancer treatment. In contrast to traditional therapies, immunotherapy is more precise and induces fewer adverse effects. In this field, some bacteria have attracted increased attention because of their natural ability to preferentially colonize and proliferate inside tumor sites and exert antitumor effects. Moreover, bacterial components may activate innate and adaptive immunity to resist tumor progression. However, the application of bacteria-based cancer immunotherapy is hampered by potential infection-associated toxicity and unpredictable behavior in vivo. Owing to modern developments in genetic engineering, bacteria can be modified to weaken their toxicity and enhance their ability to eliminate tumor cells or activate the antitumor immune response. This review summarizes the roles of bacteria in the tumor microenvironment, current strategies for bacterial engineering, and the synergistic efficiency of bacteria with other immunotherapies. In addition, the prospects and challenges of the clinical translation of engineered bacteria are summarized.

Defining the determinants of protection against SARS-CoV-2 infection and viral control in a dose-down Ad26.CoV2.S vaccine study in nonhuman primates.

Despite the rapid creation of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) vaccines, the precise correlates of immunity against severe Coronavirus Disease 2019 (COVID-19) are still unknown. Neutralizing antibodies represent a robust surrogate of protection in early Phase III studies, but vaccines provide protection prior to the evolution of neutralization, vaccines provide protection against variants that evade neutralization, and vaccines continue to provide protection against disease severity in the setting of waning neutralizing titers. Thus, in this study, using an Ad26.CoV2.S dose-down approach in nonhuman primates (NHPs), the role of neutralization, Fc effector function, and T-cell immunity were collectively probed against infection as well as against viral control. While dosing-down minimally impacted neutralizing and binding antibody titers, Fc receptor binding and functional antibody levels were induced in a highly dose-dependent manner. Neutralizing antibody and Fc receptor binding titers, but minimally T cells, were linked to the prevention of transmission. Conversely, Fc receptor binding/function and T cells were linked to antiviral control, with a minimal role for neutralization. These data point to dichotomous roles of neutralization and T-cell function in protection against transmission and disease severity and a continuous role for Fc effector function as a correlate of immunity key to halting and controlling SARS-CoV-2 and emerging variants.

High Frequency of Prior Severe Acute Respiratory Syndrome Coronavirus 2 Infection by Sensitive Nucleocapsid Assays.

Prior infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is typically measured by nucleocapsid serology assays. In this study, we show that the Simoa serology assay and T-cell intracellular cytokine staining assay are more sensitive than the clinical Elecsys assay for detection of nucleocapsid-specific immune responses. These data suggest that the prevalence of prior SARS-CoV-2 infection in the population may be higher than currently appreciated.

Novel Polystyrene-Binding Nanobody for Enhancing Immunoassays: Insights into Affinity, Immobilization, and Application Potential.

Nanobodies, which represent the next generation of antibodies due to their unique properties, face a significant limitation in their poor physical adsorption on solid supports. In this study, we successfully discovered polystyrene binding nanobodies from a synthetic nanobody library. Notably, bivalent nanobody B2 exhibited high affinity for polystyrene (0.7 nM for ELISA saturation binding analysis and 15.6 nM for isothermal titration calorimetry), displaying a pH-dependent behavior. Remarkably, hydrophobic and electrostatic interactions contribute minimally to the binding process. Molecular modeling provided insights into the interaction between B2 and polystyrene, revealing that the Trp51 residue within the CDR2 loop formed an aromatic H-bond with polystyrene at a distance of 2.74 Å, thus explaining the observed reduction in B2 affinity caused by Trp51 mutations. To explore B2's potential in protein immobilization, we constructed a bispecific nanobody by fusing B2 to an anticarcinoembryonic antigen nanobody 11C12, which cannot be immobilized on polystyrene through passive adsorption. Remarkably, the fusion construct achieved effective immobilization on polystyrene within 5 min by passing the need for periplasmic protein purification despite its low expression level. Moreover, the fusion construct demonstrated excellent linearity in the chemiluminescent enzyme immunoassay. For the first time, this study reports a simplified and seamless platform for the oriented immobilization of nanobody. Importantly, the entire process eliminated the need for protein purification, enabling efficient and rapid immobilization of fusion proteins directly from crude cell extracts, even when the expression level was low. Our developed process dramatically reduced the processing time from 2.5 days to just 5 min.

Melatonin improves cholestatic liver disease via the gut-liver axis.

Cholestatic liver disease is characterized by disturbances in the intestinal microbiota and excessive accumulation of toxic bile acids (BA) in the liver. Melatonin (MT) can improve liver diseases. However, the underlying mechanism remains unclear. This study aimed to explore the mechanism of MT on hepatic BA synthesis, liver injury, and fibrosis in 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-fed and Mdr2-/- mice. MT significantly improved hepatic injury and fibrosis with a significant decrease in hepatic BA accumulation in DDC-fed and Mdr2-/- mice. MT reprogramed gut microbiota and augmented fecal bile salt hydrolase activity, which was related to increasing intestinal BA deconjugation and fecal BA excretion in both DDC-fed and Mdr2-/- mice. MT significantly activated the intestinal farnesoid X receptor (FXR)/fibroblast growth factor 15 (FGF-15) axis and subsequently inhibited hepatic BA synthesis in DDC-fed and Mdr2-/- mice. MT failed to improve DDC-induced liver fibrosis and BA synthesis in antibiotic-treated mice. Furthermore, MT provided protection against DDC-induced liver injury and fibrosis in fecal microbiota transplantation mice. MT did not decrease liver injury and fibrosis in DDC-fed intestinal epithelial cell-specific FXR knockout mice, suggesting that the intestinal FXR mediated the anti-fibrosis effect of MT. In conclusion, MT ameliorates cholestatic liver diseases by remodeling gut microbiota and activating intestinal FXR/FGF-15 axis-mediated inhibition of hepatic BA synthesis and promotion of BA excretion in mice.