Broadly neutralizing antibodies targeting HIV: Progress and challenges

Nanoscale warriors against viral invaders: a comprehensive review of Nanobodies as potential antiviral therapeutics

Viral infections remain a significant global health threat, with emerging and reemerging viruses causing epidemics and pandemics. Despite advancements in antiviral therapies, the development of effective treatments is often hindered by challenges, such as viral resistance and the emergence of new strains. In this context, the development of novel therapeutic modalities is essential to combat notorious viruses. While traditional monoclonal antibodies are widely used for the treatment of several diseases, nanobodies derived from heavy chain-only antibodies have emerged as promising "nanoscale warriors" against viral infections. Nanobodies possess unique structural properties that enhance their ability to recognize diverse epitopes. Their small size also imparts properties, such as improved bioavailability, solubility, stability, and proteolytic resistance, making them an ideal class of therapeutics for viral infections. In this review, we discuss the role of nanobodies as antivirals against various viruses. Techniques used for developing nanobodies, delivery strategies are covered, and the challenges and opportunities associated with their use as antiviral therapies are discussed. We also offer insights into the future of nanobody-based antiviral research to support the development of new strategies for managing viral infections.

Subcutaneous liposomal delivery improves monoclonal antibody pharmacokinetics in vivo

Background Monoclonal antibodies (mAbs) effectively treat and prevent various diseases, but their clinical application is hindered by issues related to the route of administration and pharmacokinetics (PK). Intravenous (IV) administration is cumbersome, while subcutaneous (SC) administration is hampered by lower bioavailability and potential for immunogenicity. This study evaluated the efficacy of liposomal formulations in enhancing the subcutaneous (SC) delivery and PK of broadly neutralizing antibodies (bNAbs) directed against HIV.

METHODS

mAbs were encapsulated in liposomes with and without PEGylation. The liposomes were characterized for particle size, polydispersity index, zeta potential, and release. Thereafter, mice were injected with free mAbs or liposome-encapsulated mAbs, and PK was evaluated.

RESULTS

Liposomes exhibited sizes of 85-92 nm with negative surface charges. Encapsulation efficiencies were 61 % for PEGylated and 58 % for non-PEGylated liposomes. Stability testing over 16 weeks revealed that formulations remained stable at 4 °C but showed leakage at 37 C. Cytotoxicity assays confirmed that the liposomal formulations did not affect cell viability or induce apoptosis in HMEC-1 cells. In vivo, PK studies in humanized FcRn mice indicated that the PEGylated formulations generally had higher half-life, Cmax, AUC, and MRT, and lower CL values compared to their non-PEGylated formulations of the same injection type. Both liposomal formulations showed improvements in bioavailability and extended half-life compared to free mAbs administered via SC and IV routes. Compared to the gold standard of IV free mAb injection, SC injection of antibodies encapsulated in PEGylated liposome had up to 80 % higher bioavailability and 45 % extension of half-life. Compared to the SC free mAb injection, the differences were even more pronounced, with liposomal SC injection having up to 113 % higher bioavailability and 81 % extension of half-life.

CONCLUSION

Overall, liposomal encapsulation effectively protected SC injected mAbs from degradation, facilitated sustained release, and improved PK profiles, suggesting a promising strategy for enhancing the therapeutic potential of mAbs in conditions that need repeated injections. Future work should further optimize liposomal formulations to increase loading capacity, stability, and release kinetics.

STATEMENT OF SIGNIFICANCE

This study addresses a challenge in the administration of monoclonal antibodies (mAbs). Intravenous administration requires additional resources, including nursing staff, making it time-consuming and costly. Although subcutaneous (SC) administration offers a less expensive and more patient-friendly option, it suffers from lower bioavailability and potentially shorter half-life. In this study, we encapsulated mAbs in liposomal formulations specifically designed to enhance their pharmacokinetics by promoting efficient lymphatic transport. Compared with both SC and even IV administration of free antibodies, liposomal formulations of mAbs remarkably improve bioavailability and extend the half-life. This innovative approach combines the comfort of SC administration with enhanced pharmacokinetics, addressing the limitations of current SC delivery methods. Liposomal formulations have the ability to greatly improve SC mAb administration by reducing the amount of antibody needed to be administered, reducing the frequency of injections, and potentially protecting against immunogenicity.

Deep Thought on the HIV Cured Cases: Where Have We Been and What Lies Ahead?

Antiretroviral therapy (ART) can effectively suppress the replication of human immunodeficiency virus (HIV), but it cannot completely eradicate the virus. The persistent existence of the HIV reservoir is a major obstacle in the quest for a cure. To date, there have been a total of seven cured cases of HIV worldwide. These patients all cleared HIV while undergoing allogeneic stem cell transplantation (allo-HSCT) for hematological malignancies. However, in these cases, the specific mechanism by which allo-HSCT leads to the eradication of HIV remains unclear, so it is necessary to conduct an in-depth analysis. Due to the difficulty in obtaining donors and the risks associated with transplantation, this treatment method is not applicable to all HIV patients. There is still a need to explore new treatment strategies. In recent years, emerging therapies such as neutralizing antibody immunotherapy, chimeric antigen receptor T cell (CAR-T) therapy, gene editing, and antiviral therapies targeting the reservoir have attracted wide attention due to their ability to effectively inhibit HIV replication. This article first elaborates on the nature of the HIV reservoir, then deeply explores the treatment modalities and potential success factors of HIV cured cases, and finally discusses the current novel treatment methods, hoping to provide comprehensive and feasible strategies for achieving the cure of HIV.

Unpredicted Protective Function of Fc-Mediated Inhibitory Antibodies for HIV and SARS-CoV-2 Vaccines

Developing effective vaccines is necessary in combating new virus pandemics. For human immunodeficiency virus (HIV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the induction of neutralizing antibodies (NAb) is important for vaccine protection; however, the exact mechanisms underlying protection require further study. Recent data emphasize that even Abs that do not exhibit neutralizing activity may contribute to immune defense by Ab Fc-mediated inhibition. Abs exhibiting this function may counter virus mutations, which are acquired to escape from NAbs, and therefore broaden the protective Ab response induced by vaccination. The steps leading to inhibition are complex. How can these functions be measured in vitro? What inhibitory assay is physiologically relevant at mimicking effective in vivo protection? This review provides a comprehensive update on the current knowledge gaps on the Ab Fc-mediated functions involved in HIV and SARS-CoV-2 protection. Understanding the inhibitory effects of these Abs is vital for designing the next generation of protective HIV and SARS-CoV-2 vaccines.

Assessing bnAb potency in the context of HIV-1 envelope conformational plasticity

For use in prevention and treatment, HIV-1 broadly neutralizing antibodies (bnAbs) have to overcome Env conformational heterogeneity of viral quasispecies and neutralize with constant high potency. Comparative analysis of neutralization data from the CATNAP database revealed a nuanced relationship between bnAb activity and Env conformational flexibility, with substantial epitope-specific variation of bnAb potency ranging from increased to decreased activity against open, neutralization-sensitive Env. To systematically investigate the impact of variability in Env conformation on bnAb potency we screened 126 JR-CSF point mutants for generalized neutralization sensitivity to weakly neutralizing antibodies (weak-nAbs) depending on trimer opening and plasma from people with chronic HIV-1 infection. 23 mutations resulted in a highly neutralization sensitive phenotype, which was associated with de-stabilization of the closed, prefusion conformation. Including 19 of these mutants into a Sensitivity Env mutant panel (SENSE-19), we classified bnAbs according to potency variations in response to trimer opening. To verify that these sensitivity patterns are independent of the in vitro assay system, replication-competent SENSE-19 mutant viruses were tested on primary CD4 T cells. While loss of potency on SENSE-19 was registered for bnAbs from several classes recognizing quaternary epitopes on pre-triggered Env, structural destabilization benefitted MPER bnAbs and other inhibitors known to have post-CD4 attachment neutralization activity. Importantly, for a subset of CD4bs bnAbs, and the interface bnAb PGT151, particularly low potency variation was noted, suggesting that Env conformational tolerance can be achieved but is not the rule. In summary, SENSE-19 screens revealed distinct tolerance levels to Env conformational intermediates between bnAbs that provide mechanistic insights in their function and broaden current neutralization breadth assessments.

Broadly neutralizing antibodies for HIV prevention: a comprehensive review and future perspectives

SUMMARYThe human immunodeficiency virus (HIV) epidemic remains a formidable global health concern, with 39 million people living with the virus and 1.3 million new infections reported in 2022. Despite anti-retroviral therapy's effectiveness in pre-exposure prophylaxis, its global adoption is limited. Broadly neutralizing antibodies (bNAbs) offer an alternative strategy for HIV prevention through passive immunization. Historically, passive immunization has been efficacious in the treatment of various diseases ranging from oncology to infectious diseases. Early clinical trials suggest bNAbs are safe, tolerable, and capable of reducing HIV RNA levels. Although challenges such as bNAb resistance have been noted in phase I trials, ongoing research aims to assess the additive or synergistic benefits of combining multiple bNAbs. Researchers are exploring bispecific and trispecific antibodies, and fragment crystallizable region modifications to augment antibody efficacy and half-life. Moreover, the potential of other antibody isotypes like IgG3 and IgA is under investigation. While promising, the application of bNAbs faces economic and logistical barriers. High manufacturing costs, particularly in resource-limited settings, and logistical challenges like cold-chain requirements pose obstacles. Preliminary studies suggest cost-effectiveness, although this is contingent on various factors like efficacy and distribution. Technological advancements and strategic partnerships may mitigate some challenges, but issues like molecular aggregation remain. The World Health Organization has provided preferred product characteristics for bNAbs, focusing on optimizing their efficacy, safety, and accessibility. The integration of bNAbs in HIV prophylaxis necessitates a multi-faceted approach, considering economic, logistical, and scientific variables. This review comprehensively covers the historical context, current advancements, and future avenues of bNAbs in HIV prevention.

A library-on-library screen reveals the breadth expansion landscape of a broadly neutralizing betacoronavirus antibody

Broadly neutralizing antibodies (bnAbs) typically evolve cross-reactivity breadth through acquiring somatic hypermutations. While evolution of breadth requires improvement of binding to multiple antigenic variants, most experimental evolution platforms select against only one antigenic variant at a time. In this study, a yeast display library-on-library approach was applied to delineate the affinity maturation of a betacoronavirus bnAb, S2P6, against 27 spike stem helix peptides in a single experiment. Our results revealed that the binding affinity landscape of S2P6 varies among different stem helix peptides. However, somatic hypermutations that confer general improvement in binding affinity across different stem helix peptides could also be identified. We further showed that a key somatic hypermutation for breadth expansion involves long-range interaction. Overall, our work not only provides a proof-of-concept for using a library-on-library approach to analyze the evolution of antibody breadth, but also has important implications for the development of broadly protective vaccines.

The Use of Broadly Neutralizing Antibodies (bNAbs) in HIV-1 Treatment and Prevention

BACKGROUND

Although antiretroviral therapy (ART) effectively halts disease progression in HIV infection, the complete eradication of the virus remains elusive. Additionally, challenges such as long-term ART toxicity, drug resistance, and the demanding regimen of daily and lifelong adherence required by ART highlight the imperative need for alternative therapeutic and preventative approaches. In recent years, broadly neutralizing antibodies (bNAbs) have emerged as promising candidates, offering potential for therapeutic, preventative, and possibly curative interventions against HIV infection.

OBJECTIVE

This review aims to provide a comprehensive overview of the current state of knowledge regarding the passive immunization of bNAbs in HIV-1-infected individuals.

MAIN FINDINGS

Recent findings from clinical trials have highlighted the potential of bNAbs in the treatment, prevention, and quest for an HIV-1 cure. While monotherapy with a single bNAb is insufficient in maintaining viral suppression and preventing viral escape, ultimately leading to viral rebound, combination therapy with potent, non-overlapping epitope-targeting bNAbs have demonstrated prolonged viral suppression and delayed time to rebound by effectively restricting the emergence of escape mutations, albeit largely in individuals with bNAb-sensitive strains. Additionally, passive immunization with bNAb has provided a "proof of concept" for antibody-mediated prevention against HIV-1 acquisition, although complete prevention has not been obtained. Therefore, further research on the use of bNAbs in HIV-1 treatment and prevention remains imperative.

Glycan-Imprinted Nanoparticle as Artificial Neutralizing Antibody for Efficient HIV-1 Recognition and Inhibition

The HIV-1 envelope is a heavily glycosylated class 1 trimeric fusion protein responsible for viral entry into CD4+ immune cells. Developing neutralizing antibodies against the specific envelope glycans is an alternative method for antiviral therapies. This work presents the first-ever development and characterization of artificial neutralizing antibodies using molecular imprinting technology to recognize and bind to the envelope protein of HIV-1. The prepared envelope glycan-imprinted nanoparticles (GINPs) can successfully prevent HIV-1 from infecting target cells by shielding the glycans on the envelope protein. In vitro experiments showed that GINPs have strong affinity toward HIV-1 (Kd = 36.7 ± 2.2 nM) and possess high anti-interference and specificity. GINPs demonstrate broad inhibition activity against both tier 1 and tier 2 HIV-1 strains with a pM-level IC50 and exhibit a significant inhibitory effect on long-term viral replication by more than 95%. The strategy provides a promising method for the inhibition and therapy of HIV-1 infection.

Rational Design and Characterization of Trispecific Antibodies Targeting the HIV-1 Receptor and Envelope Glycoprotein

Multitudinous broadly neutralizing antibodies (bNAbs) against HIV-1 have been developed as novel antiviral prophylactic and therapeutic agents. Combinations of bNAbs are generally even more effective than when they are applied individually, showing excellent neutralization coverage and limiting the emergence of escape mutants. In this study, we investigated the design and characterization of three trispecific antibodies that allow a single molecule to interact with independent HIV-1 envelope determinants-(1) the host receptor CD4, (2) the host co-receptor CCR5 and (3) distinct domains in the envelope glycoprotein of HIV-1-using an ELISA, an HIV-1 pseudovirus neutralization assay and in vivo antiviral experiments in humanized mice. We found that trispecific bNAbs and monovalent ones all had satisfactory binding activities against the corresponding antigens in the ELISA, exhibited higher potency and breadth than any previously described single bnAb in the HIV-1 pseudovirus neutralization assay and showed an excellent antiviral effect in vivo. The trispecific antibodies simultaneously recognize the host receptor CD4, host co-receptor CCR5 and HIV-1 envelope glycoprotein, which could mean they have promise as prophylactic and therapeutic agents against HIV-1.

Antibody and Cell-Based Therapies against Virus-Induced Cancers in the Context of HIV/AIDS

Infectious agents, notably viruses, can cause or increase the risk of cancer occurrences. These agents often disrupt normal cellular functions, promote uncontrolled proliferation and growth, and trigger chronic inflammation, leading to cancer. Approximately 20% of all cancer cases in humans are associated with an infectious pathogen. The International Agency for Research on Cancer (IARC) recognizes seven viruses as direct oncogenic agents, including Epstein-Barr Virus (EBV), Kaposi's Sarcoma-associated herpesvirus (KSHV), human T-cell leukemia virus type-1 (HTLV-1), human papilloma virus (HPV), hepatitis C virus (HCV), hepatitis B virus (HBV), and human immunodeficiency virus type 1 (HIV-1). Most viruses linked to increased cancer risk are typically transmitted through contact with contaminated body fluids and high-risk behaviors. The risk of infection can be reduced through vaccinations and routine testing, as well as recognizing and addressing risky behaviors and staying informed about public health concerns. Numerous strategies are currently in pre-clinical phases or undergoing clinical trials for targeting cancers driven by viral infections. Herein, we provide an overview of risk factors associated with increased cancer incidence in people living with HIV (PLWH) as well as other chronic viral infections, and contributing factors such as aging, toxicity from ART, coinfections, and comorbidities. Furthermore, we highlight both antibody- and cell-based strategies directed against virus-induced cancers while also emphasizing approaches aimed at discovering cures or achieving complete remission for affected individuals.