Abstract Oncolytic viruses are most commonly administered via intratumoral injection; however, their clinical efficacy in achieving tumor eradication remains limited by several challenges, including insufficient penetration into all tumor cells and the inability to elicit robust systemic antitumor immune responses capable of eliminating metastatic microtumors. Here, we report an oncolytic adenovirus, OAd-2B6, with an engineered adenoviral E1 region for tumor selectivity and carrying the prodrug- activating enzyme cytochrome P450 2B6 (CYP2B6) to activate the anticancer prodrug cyclophosphamide (Cytoxan, CTX). OAd-2B6 alone induced dose-dependent tumor cell killing across multiple human tumor cell lines and exhibited strong synergistic antitumor effects when combined with CTX. Importantly, OAd-2B6-mediated local activation of CTX resulted in a potent bystander killing effect that eliminated tumor cells not directly infected by the virus. In a H1299 lung cancer xenograft nude mouse model, intratumoral injection of OAd-2B6 combined with CTX significantly inhibited tumor growth and even achieved complete tumor regression, with markedly superior efficacy compared with monotherapy. In immunocompetent mice bearing 4T1 breast cancer xenografts, OAd-2B6 alone inhibited tumor growth and was accompanied by upregulation of IFN-γ and GzmB expression in the tumor-infiltrated T cells. CTX combination therapy further enhances this anti-tumor immune response, promoting the activation of T cells to suppress non-injected tumors at a distal site. Collectively, this study demonstrates that OAd-2B6 exerts potent antitumor effects through multiple mechanisms, including direct oncolysis, intratumoral prodrug activation leading to bystander killing, and enhancement of systemic antitumor immunity. These findings provide a promising strategy for improving the therapeutic efficacy of oncolytic therapy.

Human adenovirus types 55, 11, and 14 (HAdV-55, -11, and -14) are pathogenic respiratory viruses for which no drugs or vaccines are currently available. We report the generation of a replication-incompetent rAd55-5E4 with deleted E1 and E3 genes, which only replicates in cells that provide E1 proteins in trans. In mice and non-human primates, vaccination with live non-replicating rAd55-5E4 elicited robust and durable neutralizing antibody (nAb) and cell-mediated immune responses against HAdV-55, as well as cross-reactivity against HAdV-11 and HAdV-14. Furthermore, vaccination with the live non-replicating rAd55-5E4 elicited much stronger immune responses than inactivated rAd55-5E4. In transgenic mice that express human desmoglein-2, the cellular receptor for HAdV-55, -11 and -14, vaccination with rAd55-5E4 or passive transfer of macaque immune sera collected at 66 weeks post vaccination effectively protected against challenges with HAdV-55, HAdV-11, and HAdV-14. Epitope profiling revealed that nAbs mainly recognize epitopes on hexon hypervariable regions 1, 2, 5, and 7, as well as the fiber knob. This study supports the feasibility of developing replication-incompetent HAdVs as vaccines against pathogenic HAdVs.

Mucosal secretory IgA (sIgA) plays a central role in protecting against the invasion of respiratory pathogen via the upper respiratory tract. To understand how intranasal booster induces mucosal sIgA response in humans, we first used liquid chromatography-tandem mass spectrometry for peptide identification of immunoglobulin (MS Ig-seq) and single-cell B cell receptor sequencing (scBCR-seq) to identify 42 mucosal spike-specific sIgA monoclonal antibodies (mAbs) after intranasal booster. These mucosal sIgA mAbs exhibited enhanced neutralization up to 100-fold against SARS-CoV-2 variants compared with their monomeric IgG and IgA isotypes. Deep sequencing and longitudinal analysis of B cell receptor repertoires revealed that intranasal booster restimulates memory B cells primed by intramuscularvaccination to undergo IgA class switching, somatic hypermutation, and clonal expansion. Single-cell RNA-seq (scRNA-seq) revealed that intranasal booster upregulated the expression of mucosal homing receptors in spike-specific IgA-expressing B cells. This increase coincided with a transient increase of cytokines and chemokines that facilitate B cell recruitment in the nasal mucosa. Our findings demonstrate that intranasal booster can be an effective strategy for inducing upper respiratory mucosal sIgA and establishing mucosal immune protection.

The continuous emergence of highly immune-evasive SARS-CoV-2 variants has challenged vaccine efficacy. A vaccine that can provide broad protection is desirable. We evaluated the immunogenicity of a series of monovalent and bivalent adenovirus-vectored vaccines containing the spikes of Wildtype (WT), Beta, Delta, Omicron subvariants BA.1, BA.2, BA.2.12.1, BA.2.13, BA.3, BA.5, BQ.1.1, and XBB. Vaccination in mice using monovalent vaccines elicited the highest neutralizing titers against each self-matched strain, but against other variants were reduced 2- to 73-fold. A bivalent vaccine consisting of WT and BA.5 broadened the neutralizing breadth against pre-Omicron and Omicron subvariants except XBB. Among bivalent vaccines based on the strains before the emergence of XBB, a bivalent vaccine consisting of BA.2 and BA.5 elicited the most potent neutralizing antibodies against Omicron subvariants, including XBB. In mice primed with injected WT vaccine, intranasal booster with a bivalent vaccine containing XBB and BA.5 could elicit broad serum and respiratory mucosal neutralizing antibodies against all late Omicron subvariants, including XBB. In mice that had been sequentially vaccinated with WT and BA.5, intranasal booster with a monovalent XBB vaccine elicited greater serum and mucosal XBB neutralizing antibodies than bivalent vaccines containing XBB. Both monovalent and bivalent XBB vaccines induced neutralizing antibodies against EG.5. Unlike the antibody response, which is highly variant-specific, mice receiving either monovalent or bivalent vaccines elicited comparable T-cell responses against all variants. Furthermore, intranasal but not intramuscular booster induced antigen-specific lung resident T cells. This study provides insights into the design of the COVID-19 vaccine and vaccination strategies.

The highly contagious SARS-CoV-2 Omicron subvariants severely attenuated the effectiveness of currently licensed SARS-CoV-2 vaccines based on ancestral strains administered via intramuscular injection. In this study, we generated a recombinant, replication-incompetent human adenovirus type 5, Ad5-S-Omicron, that expresses Omicron BA.1 spike. Intranasal, but not intramuscular vaccination, elicited spike-specific respiratory mucosal IgA and residential T cell immune responses, in addition to systemic neutralizing antibodies and T cell immune responses against most Omicron subvariants. We tested intranasal Ad5-S-Omicron as a heterologous booster in mice that previously received intramuscular injection of inactivated ancestral vaccine. In addition to inducing serum broadly neutralizing antibodies, there was a significant induction of respiratory mucosal IgA and neutralizing activities against Omicron subvariants BA.1, BA.2, BA.5, BA.2.75, BF.7 as well as pre-Omicron strains Wildtype, Beta, and Delta. Serum and mucosal neutralizing activities against recently emerged XBB, BQ.1, and BQ.1.1 could also be detected but were much lower. Nasal lavage fluids from intranasal vaccination contained multimeric IgA that can bind to at least 10 spike proteins, including Omicron subvariants and pre-Omicron strains, and possessed broadly neutralizing activities. Intranasal vaccination using Ad5-S-Omicron or instillation of intranasal vaccinee’s nasal lavage fluids in mouse nostrils protected mice against Omicron challenge. Taken together, intranasal Ad5-S-Omicron booster on the basis of ancestral vaccines can establish effective mucosal and systemic immunity against Omicron subvariants and multiple SARS-CoV-2 variants. This candidate vaccine warrants further development as a safe, effective, and user-friendly infection and transmission-blocking vaccine.

ABSTRACTProlonged infection and possible evolution of SARS-CoV-2 in patients living with uncontrolled HIV-1 infection highlight the importance of an effective vaccination regimen, yet the immunogenicity of COVID-19 vaccines and predictive immune biomarkers have not been well investigated. Herein, we report that the magnitude and persistence of antibody and cell-mediated immunity (CMI) elicited by an Ad5-vectored COVID-19 vaccine are impaired in SIV-infected macaques with high viral loads (> 105 genome copies per ml plasma, SIVhi) but not in macaques with low viral loads (< 105, SIVlow). After a second vaccination, the immune responses are robustly enhanced in all uninfected and SIVlow macaques. These responses also show a moderate increase in 70% SIVhi macaques but decline sharply soon after. Further analysis reveals that decreased antibody and CMI responses are associated with reduced circulating follicular helper T cell (TFH) counts and aberrant CD4/CD8 ratios, respectively, indicating that dysregulation of CD4+ T cells by SIV infection impairs the COVID-19 vaccine-induced immunity. Ad5-vectored COVID-19 vaccine shows no impact on SIV loads or SIV-specific CMI responses. Our study underscores the necessity of frequent booster vaccinations in HIV-infected patients and provides indicative biomarkers for predicting vaccination effectiveness in these patients.

African swine fever (ASF) is an acute and highly contagious lethal infectious disease in swine that severely threatens the global pig industry. At present, a safe and efficacious vaccine is urgently required to prevent and control the disease. In this study, we evaluated the safety and immunogenicity of replication-incompetent type-2 adenoviruses carrying African swine fever virus (ASFV) antigens, namely CP204L (p30), E183L (p54), EP402R (CD2v), B646L (p72), and B602L (p72 chaperone). A vaccine cocktail delivered by simultaneous intramuscular (IM) and intranasal (IN) administration robustly elicited both systemic and mucosal immune responses against AFSV in mice and swine and provided highly effective protection against the circulating ASFV strain in farmed pigs. This multi-antigen cocktail vaccine was well tolerated in the vaccinated animals. No significant interference among antigens was observed. The combined IM and IN vaccination using this adenovirus-vectored antigen cocktail vaccine warrants further evaluation for providing safe and effective protection against ASFV infection and transmission.

Human adenovirus type 55 (HAdV55) represents an emerging respiratory pathogen and causes severe pneumonia with high fatality in humans. The cellular receptors, which are essential for understanding the infection and pathogenesis of HAdV55, remain unclear. In this study, we found that HAdV55 binding and infection were sharply reduced by disrupting the interaction of viral fiber protein with human desmoglein-2 (hDSG2) but only slightly reduced by disrupting the interaction of viral fiber protein with human CD46 (hCD46). Loss-of-function studies using soluble receptors, blocking antibodies, RNA interference, and gene knockout demonstrated that hDSG2 predominantly mediated HAdV55 infection. Nonpermissive rodent cells became susceptible to HAdV55 infection when hDSG2 or hCD46 was expressed, but hDSG2 mediated more efficient HAd55 infection than hCD46. We generated two transgenic mouse lines that constitutively express either hDSG2 or hCD46. Although nontransgenic mice were resistant to HAdV55 infection, infection with HAdV55 was significantly increased in hDSG2(+/+) mice but was much less increased in hCD46(+/+) mice. Our findings demonstrate that both hDSG2 and hCD46 are able to mediate HAdV55 infection but hDSG2 plays the major roles. The hDSG2 transgenic mouse can be used as a rodent model for evaluation of HAdV55 vaccine and therapeutics. IMPORTANCE Human adenovirus type 55 (HAdV55) has recently emerged as a highly virulent respiratory pathogen and has been linked to severe and even fatal pneumonia in immunocompetent adults. However, the cellular receptors mediating the entry of HAdV55 into host cells remain unclear, which hinders the establishment of HAdV55-infected animal models and the development of antiviral approaches. In this study, we demonstrated that human desmoglein-2 (hDSG2) plays the major roles during HAdV55 infection. Human CD46 (hCD46) could also mediate the infection of HAdV55, but the efficiency was much lower than for hDSG2. We generated two transgenic mouse lines that express either hDSG2 or hCD46, both of which enabled HAd55 infection in otherwise nontransgenic mice. hDSG2 transgenic mice enabled more efficient HAdV55 infection than hCD46 transgenic mice. Our study adds to our understanding of HAdV55 infection and provides an animal model for evaluating HAdV55 vaccines and therapeutics.

The rapid spread of coronavirus SARS-CoV-2 greatly threatens global public health but no prophylactic vaccine is available. Here, we report the generation of a replication-incompetent recombinant serotype 5 adenovirus, Ad5-S-nb2, carrying a codon-optimized gene encoding Spike protein (S). In mice and rhesus macaques, intramuscular injection with Ad5-S-nb2 elicits systemic S-specific antibody and cell-mediated immune (CMI) responses. Intranasal inoculation elicits both systemic and pulmonary antibody responses but weaker CMI response. At 30 days after a single vaccination with Ad5-S-nb2 either intramuscularly or intranasally, macaques are protected against SARS-CoV-2 challenge. A subsequent challenge reveals that macaques vaccinated with a 10-fold lower vaccine dosage (1 × 10 10 viral particles) are also protected, demonstrating the effectiveness of Ad5-S-nb2 and the possibility of offering more vaccine dosages within a shorter timeframe. Thus, Ad5-S-nb2 is a promising candidate vaccine and warrants further clinical evaluation.