HIV BG505 SOSIP.664 trimer with 3M-052-AF/alum induces human autologous tier-2 neutralizing antibodies

Stabilized trimers preserving the native-like HIV envelope structure may be key components of a preventive HIV vaccine regimen to induce broadly neutralizing antibodies (bnAbs). We evaluated trimeric BG505 SOSIP.664 gp140, formulated with a novel TLR7/8 signaling adjuvant, 3M-052-AF/Alum, for safety, adjuvant dose-finding and immunogenicity in a first-in-healthy adult (n=17), randomized, placebo-controlled trial (HVTN 137A). The vaccine regimen appeared safe. Robust, trimer-specific antibody, B-cell and CD4+ T-cell responses emerged post-vaccination. Five vaccinees developed serum autologous tier-2 nAbs (ID50 titer, 1:28-1:8647) after 2-3 doses targeting C3/V5 and/or V1/V2/V3 Env regions by electron microscopy and mutated pseudovirus-based neutralization analyses. Trimer-specific, B-cell-derived monoclonal antibody activities confirmed these results and showed weak heterologous neutralization in the strongest responder. Our findings demonstrate the clinical utility of the 3M-052-AF/alum adjuvant and support further improvements of trimer-based Env immunogens to focus responses on multiple broad nAb epitopes.

KEY TAKEAWAY/TAKE-HOME MESSAGES

HIV BG505 SOSIP.664 trimer with novel 3M-052-AF/alum adjuvant in humans appears safe and induces serum neutralizing antibodies to matched clade A, tier 2 virus, that map to diverse Env epitopes with relatively high titers. The novel adjuvant may be an important mediator of vaccine response.

Potent and long-lasting humoral and cellular immunity against varicella zoster virus induced by mRNA-LNP vaccine

Varicella zoster virus (VZV) is a highly contagious human herpes virus responsible for causing chickenpox (varicella) and shingles (herpes zoster). Despite the approval of a highly effective vaccine, Shingrix®, the global incidence of herpes zoster is increasing and the economic burden to the health care system and society are substantial due to significant loss of productivity and health complications, particularly among elderly and immunocompromised individuals. This is primarily because access to the vaccines remains mostly limited to countries within developed economies, such as USA and Canada. Therefore, similarly effective vaccines against VZV that are more accessible to the rest-of-the-world are necessary. In this study, we aimed to evaluate immunogenicity and memory response induced by three mRNA-LNP-based vaccine candidates targeting VZV's surface glycoprotein E (gE). C57BL/6 mice were immunized with each candidate vaccine, and humoral and cellular immune responses were assessed. Our results demonstrate that the mRNA-LNP-based vaccine candidates elicited robust and durable humoral responses specific to the gE antigen. Notably, mice vaccinated with the mRNA-LNP vaccines exhibited significantly higher antigen-specific T-cell cytokine production compared to the group receiving Shingrix®, the current standard of care vaccine. Additionally, mRNA-LNP vaccines induced long-lasting memory response, as evidenced by detection of persistent gE-specific Long-Lived Plasma Cells (LLPCs) and memory T cells four months after final immunization. These findings underscore the potential of our mRNA-LNP-based vaccine candidates in generating potent immune responses against VZV, offering promising prospects for their clinical development as an effective prophylactic vaccine against herpes zoster.

Safety, immunogenicity and efficacy of an mRNA-based COVID-19 vaccine, GLB-COV2-043, in preclinical animal models

Several COVID-19 vaccines, some more efficacious than others, are now available and deployed, including multiple mRNA- and viral vector-based vaccines. With the focus on creating cost-effective solutions that can reach the low- and medium- income world, GreenLight Biosciences has developed an mRNA vaccine candidate, GLB-COV2-043, encoding for the full-length SARS-CoV-2 Wuhan wild-type spike protein. In pre-clinical studies in mice, GLB-COV2-043 induced robust antigen-specific binding and virus-neutralizing antibody responses targeting homologous and heterologous SARS-CoV-2 variants and a TH1-biased immune response. Boosting mice with monovalent or bivalent mRNA-LNPs provided rapid recall and long-lasting neutralizing antibody titers, an increase in antibody avidity and breadth that was held over time and generation of antigen-specific memory B- and T- cells. In hamsters, vaccination with GLB-COV2-043 led to lower viral loads, reduced incidence of SARS-CoV-2-related microscopic findings in lungs, and protection against weight loss after heterologous challenge with Omicron BA.1 live virus. Altogether, these data indicate that GLB-COV2-043 mRNA-LNP vaccine candidate elicits robust protective humoral and cellular immune responses and establishes our mRNA-LNP platform for subsequent clinical evaluations.

Rapid cGMP manufacturing of COVID-19 monoclonal antibody using stable CHO cell pools

Therapeutic proteins, including monoclonal antibodies, are typically manufactured using clonally derived, stable host cell lines, since consistent and predictable cell culture performance is highly desirable. However, selecting and preparing banks of stable clones takes considerable time, which inevitably extends overall development timelines for new therapeutics by delaying the start of subsequent activities, such as the scale-up of manufacturing processes. In the context of the coronavirus disease 2019 (COVID-19) pandemic, with its intense pressure for accelerated development strategies, we used a novel transposon-based Leap-In Transposase® system to rapidly generate high-titer stable pools and then used them directly for large scale-manufacturing of an anti-severe acute respiratory syndrome coronavirus 2 monoclonal antibody under cGMP. We performed the safety testing of our non-clonal cell bank, then used it to produce material at a 200L-scale for preclinical safety studies and formulation development work, and thereafter at 2000L scale for supply of material for a Phase 1 clinical trial. Testing demonstrated the comparability of critical product qualities between the two scales and, more importantly, that our final clinical trial product met all pre-set product quality specifications. The above expediated approach provided clinical trial material within 4.5 months, in comparison to 12-14 months for production of clinical trial material via the conventional approach.

Chronic inflammation in psoriasis promotes visceral adipose tissue association with lipid-rich necrotic core through atherogenic myeloid score

Background/Introduction

Psoriasis is a chronic inflammatory condition associated with adipose dysfunction and high-risk coronary artery disease features, including non-calcified coronary burden (NCB) and lipid-rich necrotic core (LRNC). Visceral adipose tissue (VAT) is a metabolically-active depot that secretes inflammatory and proatherogenic factors, and is associated with increased NCB. Additionally, an atherogenic myeloid score (AMS) comprised of classical monocytes, low-density granulocytes, and platelets was shown to associate with psoriasis severity and NCB.

Purpose

To investigate the relationship between VAT and high-risk plaque features and test whether this relationship was potentially mediated by myeloid cells.

Methods

A cohort of 131 psoriasis patients were included in this study. Atherogenic myeloid score components were calculated using complete blood count data (platelets) and by flow cytometry (monocytes, LDGs). Coronary NCB and LRNC were quantified using QAngio and vascuCAP respectively. VAT was defined as intra-abdominal fat and was quantified using an automated contouring software with abdominal CT scans. Statistical analyses were performed using STATA 12.

Results

The cohort was middle-aged 50 (42–61) (median (IQR)), and predominantly male (61%). High VAT vs low VAT groups differed significantly in their NCB ((0.910±0.279) vs (1.431±0.517)); p<0.001), (mean ± SD). After adjustment for cardiovascular risk factors, VAT associated with the atherogenic myeloid score (β=0.221, p=0.044), with LRNC (β=0.128, p=0.047), and atherogenic myeloid score associated with LRNC (β=0.161, p=0.003). The relationship of VAT to LRNC was partially mediated by atherogenic myeloid score (25.14%, p=0.029) (Figure 1).

Conclusions

VAT associated with LRNC, and this relationship was partially mediated by the atherogenic myeloid score. These findings suggest that bioactive VAT may impart risk on coronary artery disease in part through myeloid cells.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Heart, Lung, and Blood Institute Intramural Research Program in Bethesda, Maryland Figure 1. Log-transformed atherogenic myeloid score partially mediates the relationship between VAT and log-transformed LRNC. Adjusted by Framingham Risk Score, PASI score, biologic therapy, statin therapy, type 2 diabetes, hyperlipidemia, and subcutaneous adipose tissue volume. Red arrow: represents indirect effect; Beta: standard regression coefficient.

The C3/465 glycan hole cluster in BG505 HIV-1 envelope is the major neutralizing target involved in preventing mucosal SHIV infection

Stabilized HIV-1 envelope (Env) trimers elicit tier 2 autologous neutralizing antibody (nAb) responses in immunized animals. We previously demonstrated that BG505 SOSIP.664.T332N gp140 (BG505 SOSIP) immunization of rhesus macaques (RM) provided robust protection against autologous intra-vaginal simian-human immunodeficiency virus (SHIV) challenge that was predicted by high serum nAb titers. Here, we show that nAb in these protected RM targeted a glycan hole proximal to residue 465 in gp120 in all cases. nAb also targeted another glycan hole at residues 241/289 and an epitope in V1 at varying frequencies. Non-neutralizing antibodies directed at N611-shielded epitopes in gp41 were also present but were more prevalent in RM with low nAb titers. Longitudinal analysis demonstrated that nAb broadened in some RM during sequential immunization but remained focused in others, the latter being associated with increases in nAb titer. Thirty-eight monoclonal antibodies (mAbs) isolated from a protected RM with an exceptionally high serum neutralization titer bound to the trimer in ELISA, and four of the mAbs potently neutralized the BG505 Env pseudovirus (PV) and SHIV. The four neutralizing mAbs were clonally related and targeted the 465 glycan hole to varying degrees, mimicking the serum. The data demonstrate that the C3/465 glycan hole cluster was the dominant neutralization target in high titer protected RM, despite other co-circulating neutralizing and non-neutralizing specificities. The isolation of a neutralizing mAb family argues that clonotype expansion occurred during BG505 SOSIP immunization, leading to high titer, protective nAb and setting a desirable benchmark for HIV vaccines.

Characterization of Co-Formulated High-Concentration Broadly Neutralizing Anti-HIV-1 Monoclonal Antibodies for Subcutaneous Administration

The discovery of numerous potent and broad neutralizing antibodies (bNAbs) against Human Immunodeficiency Virus type 1 (HIV-1) envelope glycoprotein has invigorated the potential of using them as an effective preventative and therapeutic agent. The majority of the anti-HIV-1 antibodies, currently under clinical investigation, are formulated singly for intra-venous (IV) infusion. However, due to the high degree of genetic variability in the case of HIV-1, a single broad neutralizing antibody will likely not be sufficient to protect against the broad range of viral isolates. To that end, delivery of two or more co-formulated bnAbs against HIV-1 in a single subcutaneous (SC) injection is highly desired. We, therefore, co-formulated two anti-HIV bnAbs, 3BNC117-LS and 10-1074-LS, to a total concentration of 150 mg/mL for SC administration and analyzed them using a panel of analytical techniques. Chromatographic based methods, such as RP-HPLC, CEX-HPLC, SEC-HPLC, were developed to ensure separation and detection of each antibody in the co-formulated sample. In addition, we used a panel of diverse pseudoviruses to detect the functionality of individual antibodies in the co-formulation. We also used these methods to test the stability of the co-formulated antibodies and believe that such an approach can support future efforts towards the formulation and characterization of multiple high-concentration antibodies for SC delivery.

Tetravalent Immunogen Assembled from Conserved Regions of HIV-1 and Delivered as mRNA Demonstrates Potent Preclinical T-Cell Immunogenicity and Breadth

A vaccine will likely be one of the key tools for ending the HIV-1/AIDS epidemic by preventing HIV-1 spread within uninfected populations and achieving a cure for people living with HIV-1. The currently prevailing view of the vaccine field is to introduce protective antibodies, nevertheless, a vaccine to be effective may need to harness protective T cells. We postulated that focusing a T-cell response on the most vulnerable regions of the HIV-1 proteome while maximizing a perfect match between the vaccine and circulating viruses will control HIV-1 replication. We currently use a combination of replication-deficient simian (chimpanzee) adenovirus and poxvirus modified vaccinia virus Ankara to deliver bivalent conserved-mosaic immunogens to human volunteers. Here, we exploit the mRNA platform by designing tetravalent immunogens designated as HIVconsvM, and demonstrate that mRNA formulated in lipid nanoparticles induces potent, broad and polyfunctional T-cell responses in a pre-clinical model. These results support optimization and further development of this vaccine strategy in experimental medicine trials in humans.

Rapid development and deployment of high-volume vaccines for pandemic response

Overcoming pandemics, such as the current Covid‐19 outbreak, requires the manufacture of several billion doses of vaccines within months. This is an extremely challenging task given the constraints in small‐scale manufacturing for clinical trials, clinical testing timelines involving multiple phases and large‐scale drug substance and drug product manufacturing. To tackle these challenges, regulatory processes are fast‐tracked, and rapid‐response manufacturing platform technologies are used. Here, we evaluate the current progress, challenges ahead and potential solutions for providing vaccines for pandemic response at an unprecedented scale and rate. Emerging rapid‐response vaccine platform technologies, especially RNA platforms, offer a high productivity estimated at over 1 billion doses per year with a small manufacturing footprint and low capital cost facilities. The self‐amplifying RNA (saRNA) drug product cost is estimated at below 1 USD/dose. These manufacturing processes and facilities can be decentralized to facilitate production, distribution, but also raw material supply. The RNA platform technology can be complemented by an a priori Quality by Design analysis aided by computational modeling in order to assure product quality and further speed up the regulatory approval processes when these platforms are used for epidemic or pandemic response in the future.

cGMP production and analysis of BG505 SOSIP.664, an extensively glycosylated, trimeric HIV-1 envelope glycoprotein vaccine candidate

We describe the properties of BG505 SOSIP.664 HIV‐1 envelope glycoprotein trimers produced under current Good Manufacturing Practice (cGMP) conditions. These proteins are the first of a new generation of native‐like trimers that are the basis for many structure‐guided immunogen development programs aimed at devising how to induce broadly neutralizing antibodies (bNAbs) to HIV‐1 by vaccination. The successful translation of this prototype demonstrates the feasibility of producing similar immunogens on an appropriate scale and of an acceptable quality for Phase I experimental medicine clinical trials. BG505 SOSIP.664 trimers are extensively glycosylated, contain numerous disulfide bonds and require proteolytic cleavage, all properties that pose a substantial challenge to cGMP production. Our strategy involved creating a stable CHO cell line that was adapted to serum‐free culture conditions to produce envelope glycoproteins. The trimers were then purified by chromatographic methods using a 2G12 bNAb affinity column and size‐exclusion chromatography. The chosen procedures allowed any adventitious viruses to be cleared from the final product to the required extent of >12 log₁₀. The final cGMP production run yielded 3.52 g (peptidic mass) of fully purified trimers (Drug Substance) from a 200 L bioreactor, a notable yield for such a complex glycoprotein. The purified trimers were fully native‐like as judged by negative‐stain electron microscopy, and were stable over a multi‐month period at room temperature or below and for at least 1 week at 50°C. Their antigenicity, disulfide bond patterns, and glycan composition were consistent with trimers produced on a research laboratory scale. The methods reported here should pave the way for the cGMP production of other native‐like Env glycoprotein trimers of various designs and genotypes.

Generation and Characterization of a Bivalent HIV-1 Subtype C gp120 Protein Boost for Proof-of-Concept HIV Vaccine Efficacy Trials in Southern Africa

The viral envelope glycoprotein (Env) is the major target for antibody (Ab)-mediated vaccine development against the Human Immunodeficiency Virus type 1 (HIV-1). Although several recombinant Env antigens have been evaluated in clinical trials, only the surface glycoprotein, gp120, (from HIV-1 subtype B, MN, and subtype CRF_01AE, A244) used in the ALVAC prime-AIDSVAX gp120 boost RV144 Phase III HIV vaccine trial was shown to contribute to protective efficacy, although modest and short-lived. Hence, for clinical trials in southern Africa, a bivalent protein boost of HIV-1 subtype C gp120 antigens composed of two complementary gp120s, from the TV1.C (chronic) and 1086.C (transmitted founder) HIV-1 strains, was selected. Stable Chinese Hamster Cell (CHO) cell lines expressing these gp120s were generated, scalable purification methods were developed, and a detailed analytical analysis of the purified proteins was conducted that showed differences and complementarity in the antigenicity, glycan occupancy, and glycan content of the two gp120 molecules. Moreover, mass spectrometry revealed some disulfide heterogeneity in the expressed proteins, particularly in V1V2-C1 region and most prominently in the TV1 gp120 dimers. These dimers not only lacked binding to certain key CD4 binding site (CD4bs) and V1V2 epitope-directed ligands but also elicited reduced Ab responses directed to those epitopes, in contrast to monomeric gp120, following immunization of rabbits. Both monomeric and dimeric gp120s elicited similarly high titer Tier 1 neutralizing Abs as measured in standard virus neutralization assays. These results provide support for clinical evaluations of bivalent preparations of purified monomeric TV1.C and 1086.C gp120 proteins.

A cationic nanoemulsion for the delivery of next-generation RNA vaccines

Nucleic acid-based vaccines such as viral vectors, plasmid DNA, and mRNA are being developed as a means to address a number of unmet medical needs that current vaccine technologies have been unable to address. Here, we describe a cationic nanoemulsion (CNE) delivery system developed to deliver a self-amplifying mRNA vaccine. This nonviral delivery system is based on Novartis's proprietary adjuvant MF59, which has an established clinical safety profile and is well tolerated in children, adults, and the elderly. We show that nonviral delivery of a 9 kb self-amplifying mRNA elicits potent immune responses in mice, rats, rabbits, and nonhuman primates comparable to a viral delivery technology, and demonstrate that, relatively low doses (75 µg) induce antibody and T-cell responses in primates. We also show the CNE-delivered self-amplifying mRNA enhances the local immune environment through recruitment of immune cells similar to an MF59 adjuvanted subunit vaccine. Lastly, we show that the site of protein expression within the muscle and magnitude of protein expression is similar to a viral vector. Given the demonstration that self-amplifying mRNA delivered using a CNE is well tolerated and immunogenic in a variety of animal models, we are optimistic about the prospects for this technology.

Physicochemical and functional characterization of vaccine antigens and adjuvants

As novel vaccine antigens and adjuvants are being tested in humans, understanding of critical quality attributes essential for eliciting optimal vaccine response and vaccine antigen-adjuvant interactions is pivotal for vaccine safety and eliciting 'protective' immune responses. Therefore, the efforts to better characterize and evaluate vaccine antigen and antigen-adjuvant drug products need to begin very early during the discovery and development phase. In this review, we discuss the importance of characterization of physicochemical and functional properties in vaccine antigen, adjuvant and the final antigen-adjuvant drug product and emphasize the greater need for more extensive understanding of vaccine antigen-adjuvant interactions. We highlight the key parameters and quality attributes that are critical to measure during preclinical and clinical testing of the vaccine and discuss in some detail the technologies, and their limitations, used in analyzing the key physicochemical and functional attributes of vaccine antigen and antigen-adjuvant drug product.

Hepatitis C as a potential cause of IgA nephropathy

This is a case report of a 16-year-old boy presenting with a history of oliguria and anasarca. Workup revealed marked proteinuria to the tune of 8 g/day. He was subsequently found to be hepatitis C positive. Genotype was hepatitis C virus type 6. Renal biopsy revealed mesangioproliferative glomerulonephritis with IgA deposits consistent with IgA nephropathy (IgAN). Initiation of oral ribavirin and pegylated interferon caused a marked reduction in proteinuria after 8 weeks of treatment. It was postulated that hepatitis C manifested as IgAN. This case report thus sheds light on the possibility of an association between hepatitis C and IgAN.

Mixed adjuvant formulations reveal a new combination that elicit antibody response comparable to Freund's adjuvants

Adjuvant formulations capable of inducing high titer and high affinity antibody responses would provide a major advance in the development of vaccines to viral infections such as HIV-1. Although oil-in-water emulsions, such as Freund's adjuvant (FCA/FIA), are known to be potent, their toxicity and reactogenicity make them unacceptable for human use. Here, we explored different adjuvants and compared their ability to elicit antibody responses to FCA/FIA. Recombinant soluble trimeric HIV-1 gp140 antigen was formulated in different adjuvants, including FCA/FIA, Carbopol-971P, Carbopol-974P and the licensed adjuvant MF59, or combinations of MF59 and Carbopol. The antigen-adjuvant formulation was administered in a prime-boost regimen into rabbits, and elicitation of antigen binding and neutralizing antibodies (nAbs) was evaluated. When used individually, only FCA/FIA elicited significantly higher titer of nAbs than the control group (gp140 in PBS (p<0.05)). Sequential prime-boost immunizations with different adjuvants did not offer improvements over the use of FCA/FIA or MF59. Remarkably however, the concurrent use of the combination of Carbopol-971P and MF59 induced potent adjuvant activity with significantly higher titer nAbs than FCA/FIA (p<0.05). This combination was not associated with any obvious local or systemic adverse effects. Antibody competition indicated that the majority of the neutralizing activities were directed to the CD4 binding site (CD4bs). Increased antibody titers to the gp41 membrane proximal external region (MPER) and gp120 V3 were detected when the more potent adjuvants were used. These data reveal that the combination of Carbopol-971P and MF59 is unusually potent for eliciting nAbs to a variety of HIV-1 nAb epitopes.

Use of a polyanionic carbomer, Carbopol971P, in combination with MF59, improves antibody responses to HIV-1 envelope glycoprotein

Identification of optimal antigen(s) and adjuvant combination(s) to elicit potent, protective, and long-lasting immunity has been a major challenge for the development of effective vaccines against chronic viral pathogens, such as HIV-1, for which there are not yet any licensed vaccines. Here we describe the use of a novel adjuvant approach employing Carbopol 971P(®) NF (hereafter referred to as Carbopol971P), a cross-linked polyanionic carbomer, in combination with the Novartis proprietary oil-in-water adjuvant, MF59, as a potentially safe and effective adjuvant to augment humoral immune responses to the HIV-1 envelope glycoprotein (Env). Intramuscular immunization of small animals with recombinant Env glycoprotein (gp140) formulated in Carbopol971P plus MF59 gave significantly higher titers of binding and virus neutralizing antibodies as compared to immunization using gp140 with either MF59 or Carbopol971P alone. In addition, the antibodies generated were of higher avidity. Importantly, the use of Carbopol971P plus MF59 did not cause any serious adverse reactions or any obvious health problems in animals upon intramuscular administration. Hence, the Carbopol971P plus MF59 adjuvant formulation may provide a benefit for future vaccine applications.

Elicitation of neutralizing antibodies directed against CD4-induced epitope(s) using a CD4 mimetic cross-linked to a HIV-1 envelope glycoprotein

The identification of HIV-1 envelope glycoprotein (Env) structures that can generate broadly neutralizing antibodies (BNAbs) is pivotal to the development of a successful vaccine against HIV-1 aimed at eliciting effective humoral immune responses. To that end, the production of novel Env structure(s) that might induce BNAbs by presentation of conserved epitopes, which are otherwise occluded, is critical. Here, we focus on a structure that stabilizes Env in a conformation representative of its primary (CD4) receptor-bound state, thereby exposing highly conserved "CD4 induced" (CD4i) epitope(s) known to be important for co-receptor binding and subsequent virus infection. A CD4-mimetic miniprotein, miniCD4 (M64U1-SH), was produced and covalently complexed to recombinant, trimeric gp140 envelope glycoprotein (gp140) using site-specific disulfide linkages. The resulting gp140-miniCD4 (gp140-S-S-M64U1) complex was recognized by CD4i antibodies and the HIV-1 co-receptor, CCR5. The gp140-miniCD4 complex elicited the highest titers of CD4i binding antibodies as well as enhanced neutralizing antibodies against Tier 1 viruses as compared to gp140 protein alone following immunization of rabbits. Neutralization against HIV-2(7312/V434M) and additional serum mapping confirm the specific elicitation of antibodies directed to the CD4i epitope(s). These results demonstrate the utility of structure-based approach in improving immunogenic response against specific region, such as the CD4i epitope(s) here, and its potential role in vaccine application.

Stabilization of HIV-1 envelope in the CD4-bound conformation through specific cross-linking of a CD4 mimetic

CD4 binding on gp120 leads to the exposure of highly conserved regions recognized by the HIV co-receptor CCR5 and by CD4-induced (CD4i) antibodies. A covalent gp120-CD4 complex was shown to elicit CD4i antibody responses in monkeys, which was correlated with control of the HIV virus infection (DeVico, A., Fouts, T., Lewis, G. K., Gallo, R. C., Godfrey, K., Charurat, M., Harris, I., Galmin, L., and Pal, R. (2007) Proc. Natl. Acad. Sci. U.S.A. 104, 17477-17482). Because the inclusion of CD4 in a vaccine formulation should be avoided, due to potential autoimmune reactions, we engineered small sized CD4 mimetics (miniCD4s) that are poorly immunogenic and do not induce anti-CD4 antibodies. We made covalent complexes between such an engineered miniCD4 and gp120 or gp140, through a site-directed coupling reaction. These complexes were recognized by CD4i antibodies as well as by the HIV co-receptor CCR5. In addition, they elicit CD4i antibody responses in rabbits and therefore represent potential vaccine candidates that mimic an important HIV fusion intermediate, without autoimmune hazard.

Lack of complex N-glycans on HIV-1 envelope glycoproteins preserves protein conformation and entry function

The HIV-1 envelope glycoprotein complex (Env) is the focus of vaccine development aimed at eliciting humoral immunity. Env's extensive and heterogeneous N-linked glycosylation affects folding, binding to lectin receptors, antigenicity and immunogenicity. We characterized recombinant Env proteins and virus particles produced in mammalian cells that lack N-acetylglucosaminyltransferase I (GnTI), an enzyme necessary for the conversion of oligomannose N-glycans to complex N-glycans. Carbohydrate analyses revealed that trimeric Env produced in GnTI(-/-) cells contained exclusively oligomannose N-glycans, with incompletely trimmed oligomannose glycans predominating. The folding and conformation of Env proteins was little affected by the manipulation of the glycosylation. Viruses produced in GnTI(-/-) cells were infectious, indicating that the conversion to complex glycans is not necessary for Env entry function, although virus binding to the C-type lectin DC-SIGN was enhanced. Manipulating Env's N-glycosylation may be useful for structural and functional studies and for vaccine design.

A complete task analysis to measure the workload associated with operating an agricultural sprayer equipped with a navigation device

The objective of this study was to perform a complete task analysis to measure the workload associated with operating an agricultural sprayer equipped with a navigation device. The task analysis included a written questionnaire and subsequent observation of sprayer operators. The questionnaire revealed that the lightbar was the most important source of guidance information (as opposed to relying on guidance information from external field cues). Observation consisted of recording eye-glance behaviour and heart rate variability while operators were spraying in a field setting. The eye-glance data suggest that external cues are more important than the lightbar for providing the necessary navigation information. Thus, the questionnaire and observation data contradict each other. Based on heart rate variability, operators who used a lightbar navigation device experienced more mental workload than operators who used an auto-steer navigation device.

Structure of the HIV-1 gp41 membrane-proximal ectodomain region in a putative prefusion conformation

The conserved membrane-proximal external region (MPER) of the HIV-1 gp41 envelope protein is the established target for very rare but broadly neutralizing monoclonal antibodies (NAbs) elicited during natural human infection. Nevertheless, attempts to generate an HIV-1 neutralizing antibody response with immunogens bearing MPER epitopes have met with limited success. Here we show that the MPER peptide (residues 662-683) forms a labile alpha-helical trimer in aqueous solution and report the crystal structure of this autonomous folding subdomain stabilized by addition of a C-terminal isoleucine zipper motif. The structure reveals a parallel triple-stranded coiled coil in which the neutralization epitope residues are buried within the interface between the associating MPER helices. Accordingly, both the 2F5 and 4E10 NAbs recognize the isolated MPER peptide but fail to bind the trimeric MPER subdomain. We propose that the trimeric MPER structure represents the prefusion conformation of gp41, preceding the putative prehairpin intermediate and the postfusion trimer-of-hairpins structure. As such, the MPER trimer should inform the design of new HIV-1 immunogens to elicit broadly neutralizing antibodies.

Structural and immunogenicity studies of a cleaved, stabilized envelope trimer derived from subtype A HIV-1

SOSIP gp140 trimers represent a soluble, stabilized, proteolytically cleaved form of the HIV-1 envelope (Env) glycoproteins. SOSIP gp140 derived from a subtype A HIV-1 isolate, KNH1144, forms exceptionally stable trimers that resemble virion-associated Env in antigenicity and topology. Here, we used electron microscopy to demonstrate that KNH1144 SOSIP gp140 trimers bound three soluble CD4 molecules in a symmetrical orientation similar to that seen for native Env. We compared the immunogenicities of KNH1144 SOSIP gp140 trimers and gp120 monomers in rabbits and found that the trimers were superior at eliciting neutralizing antibodies (NAbs) to homologous virus as well as neutralization-sensitive subtype B and C viruses. The NAb specificities for SOSIP antisera mapped in part to the CD4 binding site on gp120. We also observed adjuvant-dependent induction of antibodies to the residual levels of host cell proteins (HCPs) contained in the purified Env preparations. When present, HCP antibodies enhanced pseudovirus infection. Our findings are relevant for the further development of Env-based vaccines for HIV-1.

Biochemical and biophysical comparison of cleaved and uncleaved soluble, trimeric HIV-1 envelope glycoproteins

Human immunodeficiency virus type 1 (HIV-1) entry into host cells is mediated by the trimeric envelope glycoprotein complex (Env). Accordingly, the Env proteins are the targets for neutralizing antibodies (NAbs) and are the focus of vaccines intended to induce NAbs. Because the Env complex is labile, soluble recombinant Env (gp140) trimers require engineering to stabilize them sufficiently for use as immunogens. Trimeric forms of gp140 trimers can be created that are either cleavage-competent or cleavage-defective at the junction between the gp120 and gp41 subunits. As functional trimers are cleaved at this site, the question arises as to whether cleavage affects the antigenic structure of the Env complex in a way that is relevant to vaccine design. Here, we present a comparative analysis of the antigenicity profiles of cleaved and uncleaved gp140 trimers derived from the KNH1144 (subtype A) virus that are otherwise closely sequence-matched. While cleavage did not affect the exposure of NAb epitopes on the gp140 trimers, non-neutralizing antibodies to gp41 epitopes bound much more strongly to uncleaved trimers. Hence cleavage does alter the structure of the HIV-1 Env complex.

HIV-1 gp120 mannoses induce immunosuppressive responses from dendritic cells

The human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein gp120 is a vaccine immunogen that can signal via several cell surface receptors. To investigate whether receptor biology could influence immune responses to gp120, we studied its interaction with human, monocyte-derived dendritic cells (MDDCs) in vitro. Gp120 from the HIV-1 strain JR-FL induced IL-10 expression in MDDCs from 62% of donors, via a mannose C-type lectin receptor(s) (MCLR). Gp120 from the strain LAI was also an IL-10 inducer, but gp120 from the strain KNH1144 was not. The mannose-binding protein cyanovirin-N, the 2G12 mAb to a mannose-dependent gp120 epitope, and MCLR-specific mAbs inhibited IL-10 expression, as did enzymatic removal of gp120 mannose moieties, whereas inhibitors of signaling via CD4, CCR5, or CXCR4 were ineffective. Gp120-stimulated IL-10 production correlated with DC-SIGN expression on the cells, and involved the ERK signaling pathway. Gp120-treated MDDCs also responded poorly to maturation stimuli by up-regulating activation markers inefficiently and stimulating allogeneic T cell proliferation only weakly. These adverse reactions to gp120 were MCLR-dependent but independent of IL-10 production. Since such mechanisms might suppress immune responses to Env-containing vaccines, demannosylation may be a way to improve the immunogenicity of gp120 or gp140 proteins.

Dendritic cells (DCs) initiate immune responses to pathogens or vaccine antigens. The HIV-1 gp120 envelope glycoprotein is an antigen that is a focus of vaccine design strategies. We have studied how gp120 proteins interact with DCs in cell culture. Certain gp120s stimulate DCs from some, but not all, human donors to produce IL-10, a cytokine that is generally immunosuppressive. In addition, whether or not the DCs produce IL-10, their ability to mature properly when activated is impaired by gp120—the gp120-treated DCs have a reduced ability to stimulate T cell growth when the two cell types are cultured together. These various effects of gp120 are caused by its binding to cell surface receptors of the mannose C-type lectin receptor family, including (but probably not exclusively) one called DC-SIGN. Gp120 binds to these receptors via mannose residues that are present on some of the glycan structures that overlay much of its protein surface. Removing the mannoses by digesting gp120 with a suitable enzyme prevents IL-10 induction and impairment of DC maturation, as does the use of inhibitors of the binding of gp120 to DC-SIGN and similar receptors. This work could help with the design of better HIV-1 vaccines.

N-terminal substitutions in HIV-1 gp41 reduce the expression of non-trimeric envelope glycoproteins on the virus

The native, functional HIV-1 envelope glycoprotein (Env) complex is a trimer of two non-covalently associated subunits: the gp120 surface glycoprotein and the gp41 transmembrane glycoprotein. However, various non-functional forms of Env are present on virus particles and HIV-1-infected cells, some of which probably arise as the native complex decays. The aberrant forms include gp120-gp41 monomers and oligomers, as well as gp41 subunits from which gp120 has dissociated. The presence of non-functional Env creates binding sites for antibodies that do not recognize native Env complexes and that are, therefore, non-neutralizing. Non-native Env forms (monomers, dimers, tetramers and aggregates) can also arise when soluble gp140 proteins, lacking the cytoplasmic and transmembrane domains of gp41, are expressed for vaccine studies. We recently identified five amino acids in the gp41 N-terminal region (I535, Q543, S553, K567 and R588) that promote gp140 trimerization. We have now studied their influence on the function and antigenic properties of JR-FL Env expressed on the surfaces of pseudoviruses and Env-transfected cells. The 5 substitutions in gp41 reduce the expression of non-trimeric gp160s, without affecting trimer levels. Pseudovirions bearing the mutant Env are fully infectious with similar kinetics of Env-mediated fusion. Various non-neutralizing antibodies bind less strongly to the Env mutant, but neutralizing antibody binding is unaffected. Hence the gp41 substitutions do not adversely affect Env structure, supporting their use for making new Env-based vaccines. The mutant Env might also help in studies intended to correlate antibody binding to virus neutralization. Of note is that the 5 residues are much more frequent, individually or collectively, in viruses from subtypes other than B.

Purified, proteolytically mature HIV type 1 SOSIP gp140 envelope trimers

HIV type 1 (HIV-1) envelope is a noncovalent trimer of gp120-gp41 heterodimers, and its lability has hindered structural studies. SOSIP gp140 is a soluble, proteolytically mature form of the HIV-1 envelope wherein gp120-gp41 interactions are stabilized via a disulfide bond and gp41 contains an additional trimer-stabilizing point mutation. We describe the isolation of a substantially pure preparation of SOSIP gp140 trimers derived from KNH1144, a subtype A isolate. Following initial purification, the only significant contaminant was higher-order gp140 aggregates; however, 0.05% Tween 20 quantitatively converted these aggregates into trimers. The surfactant effect was rapid, dose dependent, and similarly effective for a subtype B SOSIP gp140. Surfactant-treated SOSIP gp140 retained favorable antigenicity and formed compact trimers 12-13 nm in size as determined by electron microscopy. This report provides the first description of homogeneous, cleaved HIV-1 envelope trimers. These proteins may be useful as vaccine immunogens and for studying structure-function relationships within the HIV-1 envelope glycoproteins.

A comparative immunogenicity study in rabbits of disulfide-stabilized, proteolytically cleaved, soluble trimeric human immunodeficiency virus type 1 gp140, trimeric cleavage-defective gp140 and monomeric gp120

The human immunodeficiency virus type 1 (HIV-1) surface envelope glycoprotein (Env) complex, a homotrimer containing gp120 surface glycoprotein and gp41 transmembrane glycoprotein subunits, mediates the binding and fusion of the virus with susceptible target cells. The Env complex is the target for neutralizing antibodies (NAbs) and is the basis for vaccines intended to induce NAbs. Early generation vaccines based on monomeric gp120 subunits did not confer protection from infection; one alternative approach is therefore to make and evaluate soluble forms of the trimeric Env complex. We have directly compared the immunogenicity in rabbits of two forms of soluble trimeric Env and monomeric gp120 based on the sequence of HIV-1(JR-FL). Both protein-only and DNA-prime, protein-boost immunization formats were evaluated, DNA-priming having little or no influence on the outcome. One form of trimeric Env was made by disrupting the gp120-gp41 cleavage site by mutagenesis (gp140(UNC)), the other contains an intramolecular disulfide bond to stabilize the cleaved gp120 and gp41 moieties (SOSIP.R6 gp140). Among the three immunogens, SOSIP.R6 gp140 most frequently elicited neutralizing antibodies against the homologous, neutralization-resistant strain, HIV-1(JR-FL). All three proteins induced NAbs against more sensitive strains, but the breadth of activity against heterologous primary isolates was limited. When antibodies able to neutralize HIV-1(JR-FL) were detected, antigen depletion studies showed they were not directed at the V3 region but were targeted at other, undefined gp120 and also non-gp120 epitopes.

Specific amino acids in the N-terminus of the gp41 ectodomain contribute to the stabilization of a soluble, cleaved gp140 envelope glycoprotein from human immunodeficiency virus type 1

The HIV-1 envelope glycoprotein is expressed on the viral membrane as a trimeric complex, formed by three gp120 surface glycoproteins non-covalently associated with three membrane-anchored gp41 subunits. The labile nature of the association between gp120 and gp41 hinders the expression of soluble, fully cleaved, trimeric gp140 proteins for structural and immunization studies. Disruption of the primary cleavage site within gp160 allows the production of stable gp140 trimers, but cleavage-defective trimers are antigenically dissimilar from their cleaved counterparts. Soluble, stabilized, proteolytically cleaved, trimeric gp140 proteins can be generated by engineering an intermolecular disulfide bond between gp120 and gp41 (SOS), combined with a single residue change, I559P, within gp41 (SOSIP). We have found that SOSIP gp140 proteins based on the subtype A HIV-1 strain KNH1144 form particularly homogenous trimers compared to a prototypic strain (JR-FL, subtype B). We now show that the determinants of this enhanced stability are located in the N-terminal region of KNH11144 gp41 and that, when substituted into heterologous Env sequences (e.g., JR-FL and Ba-L) they have a similarly beneficial effect on trimer stability. The stabilized trimers retain the epitopes for several neutralizing antibodies (b12, 2G12, 2F5 and 4E10) and the CD4-IgG2 molecule, suggesting that the overall antigenic structure of the gp140 protein has not been adversely impaired by the trimer-stabilizing substitutions. The ability to increase the stability of gp140 trimers might be useful for neutralizing antibody-based vaccine strategies based on the use of this type of immunogen.

Construction and characterization of soluble, cleaved, and stabilized trimeric Env proteins based on HIV type 1 Env subtype A

The generation of an antibody response capable of neutralizing a broad range of clinical isolates remains an important goal of human immunodeficiency virus type 1 (HIV-1) vaccine development. Envelope glycoprotein (Env)-based vaccine candidates will also need to take into account the extensive genetic diversity of circulating HIV-1 strains. We describe here the generation of soluble, stabilized, proteolytically cleaved, trimeric forms of Env (SOSIP gp140 proteins) based on contemporary Env subtype A viruses from East Africa. We discuss issues associated with the construction, purification, and characterization of such complex proteins; not all env sequences allow the expression of trimeric proteins. However, stabilized trimers from one such protein, KNH1144 SOSIP gp140, were successfully made. These proteins are now being prepared for preclinical immunogenicity studies.

An aptamer that neutralizes R5 strains of human immunodeficiency virus type 1 blocks gp120-CCR5 interaction

We recently described the isolation and structural characterization of 2'-fluoropyrimidine-substituted RNA aptamers that bind to gp120 of R5 strains of human immunodeficiency virus type 1 and thereby potently neutralize the infectivity of phylogenetically diverse R5 strains. Here we investigate the physical basis of their antiviral action. We show that both N-linked oligosaccharides and the variable loops V1/V2 and V3 are not required for binding of one aptamer, B40, to gp120. Using surface plasmon resonance binding analyses, we show that the aptamer binds to the CCR5-binding site on gp120 in a relatively CD4-independent manner, providing a mechanistic explanation for its neutralizing potency.

Structural characterization of an anti-gp120 RNA aptamer that neutralizes R5 strains of HIV-1

We recently described the isolation of 2'-fluoropyrimidine-substituted RNA aptamers that bind specifically to the surface glycoprotein (gp 120) of the R5 strain, HIV-1(Ba-L), as presented in a previous study. These aptamers potently neutralize HIV-1 infectivity in human peripheral blood mononuclear cells of both tissue culture lab-adapted strains and diverse R5 clinical isolates from multiple clades. Here, we report a detailed structural characterization of one such neutralizing aptamer, B40, using enzymatic and chemical probing methods. We identify the minimal region of the aptamer essential for binding gp120 and accordingly design a 77-nucleotide truncated aptamer, B40t77. We then quantitatively analyze the binding affinity and neutralization potency of the parental and truncated (minimal) aptamer, and show them to be comparable. Furthermore, using results from secondary structure analysis, RNA mutagenesis and BIAcore surface plasmon resonance (SPR) binding assays, we hypothesize that a folded RNA structure is required to present specific nucleotide sequences to allow gp120-recognition and binding. The information gained from this study may provide leads for development of novel anti-HIV-1 therapies and can be used to extend our understanding of the molecular interactions between the virus and its host cell.

Training of final year MBBS students in neonatal resuscitation

Sixty final year MBBS students were trained in the art of neonatal resuscitation based on the 'NALS' course material. The students scored 11.6 +/- 3.02 in the pretest and 17.85 +/- 4.42 (out of 20) in the post-test. The trainees felt that the programme was extremely useful. Majority of them said that the course content was optimum with appropriate use of teaching-learning media. It is recommended that this training may be imparted to all the undergraduate students at the entry of final year MBBS course before their labor room posting so that they can have effective reinforcement of the training.

Changing pattern of antimicrobial utilization in an Indian teaching hospital

A study was conducted at Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry, India, on the pattern of antimicrobial utilization in hospitalized patients. A retrospective study was conducted during a one-month period between January 18 to February 17, 1987. The data were analyzed according to modified Kunin's criteria. The results were compared with a similar study conducted a decade ago. The study revealed a marked increase in the use of antimicrobial agents (from 19.9% to 56.1%). A more appropriate use of antimicrobial agents was observed (from 66.8% to 79.5%). A significant increase in their appropriate use for therapeutic purpose (50% to 88.2%), but not for prophylaxis (79.05% to 71.18%) was seen. The study revealed a marked increase in the use of antimicrobial agents during the last decade resulting in the emergence of nosocomial infections of resistant strains of organisms.

Chelation reactions of adenine

Chelation reactions of the antimitotic drug, 6-amino-purine (adenine; abbr. ADN) with the metal ions: Be(II), Al(III), Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Pb(II), and UO2(II) have been investigated in aqueous solution at 30° using Bjerrum-Calvin pH titration technique. The formation constants have been determined at various ionic concentrations, and have been extrapolated to zero ionic strength to get the thermodynamic values of the constants.

Avidity of folic acid for carcinogenic metal ions aluminium(3), chromium(3), beryllium(II), lead(II) and uranium(VI)

Stepwise formation constants of folic acid, N-[p-[[ (2-amino-4-hydroxy-6-pteridyl) methyl] amino] benzyl] glutamic acid, with the carcinogenic metal ions, aluminium (III), chromium (III), beryllium (II), lead (II) and uranium (VI) have been determined at 30 °C, and at various ionic strengths, viz. 0.01 ᴍ, 0.05 ᴍ, 0.10 ᴍ, maintained by potassium nitrate solution. The formation of the chelate is evident from the shift between the (i) ligand and (ii) ligand and metal titration curves. From the values for the stepwise protonation constants and metal-ligand stability constants at various ionic strengths, thermodynamic formation constants were evaluated by extrapolation to zero ionic concentration. Logarithms of the overall thermodynamic stability constants (log Kμ=0) are: 20.40 for H-; 15.15 for Al-; 10.10 for Cr-; 9.35 for Be-; 6.50 for Pb-; 9.00 for U-chelates. Corresponding free energy changes (ΔF0) are -28.47, -21.14, -14.09, -13.05, -9.07, -12.56 K · Cal · mol-1 respectively