Current status of mannose receptor-targeted drug delivery for improved anti-HIV therapy

In the pursuit of achieving better therapeutic outcomes in the treatment of HIV, innovative drug delivery strategies have been extensively explored. Mannose receptors, which are primarily found on macrophages and dendritic cells, offer promising targets for drug delivery due to their involvement in HIV pathogenesis. This review article comprehensively evaluates recent drug delivery system advancements targeting the mannose receptor. We have systematically described recent developments in creating and utilizing drug delivery platforms, including nanoparticles, liposomes, micelles, noisomes, dendrimers, and other nanocarrier systems targeted at the mannose receptor. These strategies aim to enhance drug delivery specificity, bioavailability, and therapeutic efficacy while decreasing off-target effects and systemic toxicity. Furthermore, the article delves into how mannose receptors and HIV interact, highlighting the potential for exploiting this interaction to enhance drug delivery to infected cells. The review covers essential topics, such as the rational design of nanocarriers for mannose receptor recognition, the impact of physicochemical properties on drug delivery performance, and how targeted delivery affects the pharmacokinetics and pharmacodynamics of anti-HIV agents. The challenges of these novel strategies, including immunogenicity, stability, and scalability, and future research directions in this rapidly growing area are discussed. The knowledge synthesis presented in this review underscores the potential of mannose receptor-based targeted drug delivery as a promising avenue for advancing HIV treatment. By leveraging the unique properties of mannose receptors, researchers can design drug delivery systems that cater to individual needs, overcome existing limitations, and create more effective and patient-friendly treatments in the ongoing fight against HIV/AIDS.

Lectins and lectibodies: potential promising antiviral agents

In nature, lectins are widely dispersed proteins that selectively recognize and bind to carbohydrates and glycoconjugates via reversible bonds at specific binding sites. Many viral diseases have been treated with lectins due to their wide range of structures, specificity for carbohydrates, and ability to bind carbohydrates. Through hemagglutination assays, these proteins can be detected interacting with various carbohydrates on the surface of cells and viral envelopes. This review discusses the most robust lectins and their rationally engineered versions, such as lectibodies, as antiviral proteins. Fusion of lectin and antibody’s crystallizable fragment (Fc) of immunoglobulin G (IgG) produces a molecule called a “lectibody” that can act as a carbohydrate-targeting antibody. Lectibodies can not only bind to the surface glycoproteins via their lectins and neutralize and clear viruses or infected cells by viruses but also perform Fc-mediated antibody effector functions. These functions include complement-dependent cytotoxicity (CDC), antibody-dependent cell-mediated cytotoxicity (ADCC), and antibody-dependent cell-mediated phagocytosis (ADCP). In addition to entering host cells, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein S1 binds to angiotensin-converting enzyme 2 (ACE2) and downregulates it and type I interferons in a way that may lead to lung disease. The SARS-CoV-2 spike protein S1 and human immunodeficiency virus (HIV) envelope are heavily glycosylated, which could make them a major target for developing vaccines, diagnostic tests, and therapeutic drugs. Lectibodies can lead to neutralization and clearance of viruses and cells infected by viruses by binding to glycans located on the envelope surface (e.g., the heavily glycosylated SARS-CoV-2 spike protein).

Abnormal saccharides affecting cancer multi-drug resistance (MDR) and the reversal strategies

Clinically, chemotherapy is the mainstay in the treatment of multiple cancers. However, highly adaptable and activated survival signaling pathways of cancer cells readily emerge after long exposure to chemotherapeutics drugs, resulting in multi-drug resistance (MDR) and treatment failure. Recently, growing evidences indicate that the molecular action mechanisms of cancer MDR are closely associated with abnormalities in saccharides. In this review, saccharides affecting cancer MDR development are elaborated and analyzed in terms of aberrant aerobic glycolysis and its related enzymes, abnormal glycan structures and their associated enzymes, and glycoproteins. The reversal strategies including depletion of ATP, circumventing the original MDR pathway, activation by or inhibition of sugar-related enzymes, combination therapy with traditional cytotoxic agents, and direct modification on the sugar moiety, are ultimately proposed. It follows that abnormal saccharides have a significant effect on cancer MDR development, providing a new perspective for overcoming MDR and improving the outcome of chemotherapy.

Rational Design of A Novel Small-Molecule HIV-1 Inactivator Targeting Both gp120 and gp41 of HIV-1

Virus inactivator can inactivate cell-free virions without relying on their replication cycle, potentially reducing the impact of viral infection on cells. Previously, we successfully constructed a HIV-1 protein inactivator, 2DLT, by conjugating the D1D2 region of CD4 to the fusion inhibitor T1144 via a 35-amino acid linker. Therefore, it targets both the CD4 binding site in gp120 and NHR region in gp41. Considering that small-molecule agents have the advantages of fast production, low cost, good stability, and oral availability, we herein report the design of a new small-molecule HIV-1 inactivator, FD028, by conjugating FD016 (an analog of NBD-556, a gp120-CD4 binding inhibitor) with FD017 (an analog of 11d, an HIV-1 fusion inhibitor). The results showed that FD028 inactivated cell-free virions at a moderate nanomolar concentration by targeting both HIV-1 gp120 and gp41. Moreover, FD028 has broad-spectrum inhibition and inactivation activity against HIV-1 resistant strains and primary isolates of different subtypes without significant cytotoxicity. Therefore, FD028 has potential for further development as an HIV-1 inactivator-based therapeutic.

HIV-1 and its resistance to peptidic carbohydrate-binding agents (CBAs): an overview

The glycoproteins on the surfaces of enveloped viruses, such as HIV, can be considered as a unique target for antiviral therapy. Different carbohydrate-binding agents (CBAs) target specific glycans present on viral glycoproteins of enveloped viruses. It has been shown that long-term CBA pressure in vitro can result in mutant HIV-1 isolates with several N-linked glycan deletions on gp120. These studies demonstrated that mainly high-mannose type glycans are deleted. However, interestingly, N241, N262 and N356 on gp120 have never been found to be affected after prolonged CBA exposure. Here, we review the mutation and (cross)-resistance profiles of eleven specific generated CBA-resistant HIV-1 strains. We observed that the broad-neutralizing anti-carbohydrate binding mAb 2G12 became completely inactive against all the generated CBA-resistant HIV-1 clade B isolates. In addition, all of the CBAs discussed in this review, with the exception of NICTABA, interfered with the binding of 2G12 mAb to gp120 expressed on HIV-1-infected T cells. The cross-resistance profiles of mutant HIV-1 strains are varying from increased susceptibility to very high resistance levels, even among different classes of CBAs with dissimilar sugar specificities or binding moieties [e.g., α(1,3), α(1,2), α(1,6)]. Recent studies demonstrated promising results in non-topical formulations (e.g., intranasally or subcutaneously), highlighting their potential for prevention (microbicides) and antiviral therapy.

The role of N-glycans of HIV-1 gp41 in virus infectivity and susceptibility to the suppressive effects of carbohydrate-binding agents

BACKGROUND

Carbohydrate-binding agents (CBAs) are potent antiretroviral compounds that target the N-glycans on the HIV-1 envelope glycoproteins. The development of phenotypic resistance to CBAs by the virus is accompanied by the deletion of multiple N-linked glycans of the surface envelope glycoprotein gp120. Recently, also an N-glycan on the transmembrane envelope glycoprotein gp41 was shown to be deleted during CBA resistance development.

RESULTS

We generated HIV-1 mutants lacking gp41 N-glycans and determined the influence of these glycan deletions on the viral phenotype (infectivity, CD4 binding, envelope glycoprotein incorporation in the viral particle and on the transfected cell, virus capture by DC-SIGN(+) cells and transmission of DC-SIGN-captured virions to CD4(+) T-lymphocytes) and on the phenotypic susceptibility of HIV-1 to a selection of CBAs. It was shown that some gp41 N-glycans are crucial for the infectivity of the virus. In particular, lack of an intact N616 glycosylation site was shown to result in the loss of viral infectivity of several (i.e. the X4-tropic IIIB and NL4.3 strains, and the X4/R5-tropic HE strain), but not all (i.e. the R5-tropic ADA strain) studied HIV-1 strains. In accordance, we found that the gp120 levels in the envelope of N616Q mutant gp41 strains NL4.3, IIIB and HE were severely decreased. In contrast, N616Q gp41 mutant HIV-1ADA contained gp120 levels similar to the gp120 levels in WT HIV-1ADA virus. Concomitantly deleting multiple gp41 N-glycans was often highly detrimental for viral infectivity. Using surface plasmon resonance technology we showed that CBAs have a pronounced affinity for both gp120 and gp41. However, the antiviral activity of CBAs is not dependent on the concomitant presence of all gp41 glycans. Single gp41 glycan deletions had no marked effects on CBA susceptibility, whereas some combinations of two to three gp41 glycan-deletions had a minor effect on CBA activity.

CONCLUSIONS

We revealed the importance of some gp41 N-linked glycans, in particular the N616 glycan which was shown to be absolutely indispensable for the infectivity potential of several virus strains. In addition, we demonstrated that the deletion of up to three gp41 N-linked glycans only slightly affected CBA susceptibility.

Targeting strategies for delivery of anti-HIV drugs

Human Immunodeficiency Virus (HIV) infection remains a significant cause of mortality globally. Though antiretroviral therapy has significantly reduced AIDS-related morbidity and mortality, there are several drawbacks in the current therapy, including toxicity, drug–drug interactions, development of drug resistance, necessity for long-term drug therapy, poor bio-availability and lack of access to tissues and reservoirs. To circumvent these problems, recent anti-HIV therapeutic research has focused on improving drug delivery systems through drug delivery targeted specifically to host cells infected with HIV or could potentially get infected with HIV. In this regard, several surface molecules of both viral and host cell origin have been described in recent years, that would enable targeted drug delivery in HIV infection. In the present review, we provide a comprehensive overview of the need for novel drug delivery systems, and the successes and challenges in the identification of novel viral and host-cell molecules for the targeted drug delivery of anti-HIV drugs. Such targeted anti-retroviral drug delivery approaches could pave the way for effective treatment and eradication of HIV from the body.