Long-primed germinal centres with enduring affinity maturation and clonal migration

Germinal centres are the engines of antibody evolution. Here, using human immunodeficiency virus (HIV) Env protein immunogen priming in rhesus monkeys followed by a long period without further immunization, we demonstrate germinal centre B (BGC) cells that last for at least 6 months. A 186-fold increase in BGC cells was present by week 10 compared with conventional immunization. Single-cell transcriptional profiling showed that both light- and dark-zone germinal centre states were sustained. Antibody somatic hypermutation of BGC cells continued to accumulate throughout the 29-week priming period, with evidence of selective pressure. Env-binding BGC cells were still 49-fold above baseline at 29 weeks, which suggests that they could remain active for even longer periods of time. High titres of HIV-neutralizing antibodies were generated after a single booster immunization. Fully glycosylated HIV trimer protein is a complex antigen, posing considerable immunodominance challenges for B cells1,2. Memory B cells generated under these long priming conditions had higher levels of antibody somatic hypermutation, and both memory B cells and antibodies were more likely to recognize non-immunodominant epitopes. Numerous BGC cell lineage phylogenies spanning more than the 6-month germinal centre period were identified, demonstrating continuous germinal centre activity and selection for at least 191 days with no further antigen exposure. A long-prime, slow-delivery (12 days) immunization approach holds promise for difficult vaccine targets and suggests that patience can have great value for tuning of germinal centres to maximize antibody responses.

Highly mutated antibodies capable of neutralizing N276 glycan-deficient HIV after a single immunization with an Env trimer

Elicitation of HIV broadly neutralizing antibodies (bnAbs) is challenging because unmutated bnAb precursors are rare and seldom bind HIV envelope glycoprotein (Env) trimers. One strategy to initiate bnAb responses is to use germline-targeting (GT) immunogens with high affinity to bnAb-class precursor B cells and then shepherd affinity maturation with booster immunogens that successively look more like native Env. In a mouse model where the frequency of VRC01-precursor (VRC01gHL) B cells mimics that of humans, we show that following a GT HIV Env trimer protein prime, VRC01-class B cells in the germinal center (GC) acquire high-affinity VRC01-class B cell somatic hypermutations (SHMs). Many GC-derived VRC01gHL antibodies robustly bind N276 glycan-deficient Env trimers and neutralize several N276 glycan-deficient tier 2 HIV strains. These results are encouraging for GT Env trimer vaccine designs and demonstrate accumulation of substantial SHMs, including deletions, uncommon point mutations, and functional bnAb features, after a single immunization.

Phosphate-mediated coanchoring of RBD immunogens and molecular adjuvants to alum potentiates humoral immunity against SARS-CoV-2

There is a need for additional rapidly scalable, low-cost vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to achieve global vaccination. Aluminum hydroxide (alum) adjuvant is the most widely available vaccine adjuvant but elicits modest humoral responses. We hypothesized that phosphate-mediated coanchoring of the receptor binding domain (RBD) of SARS-CoV-2 together with molecular adjuvants on alum particles could potentiate humoral immunity by promoting extended vaccine kinetics and codelivery of vaccine components to lymph nodes. Modification of RBD immunogens with phosphoserine (pSer) peptides enabled efficient alum binding and slowed antigen clearance, leading to notable increases in germinal center responses and neutralizing antibody titers in mice. Adding phosphate-containing CpG or saponin adjuvants to pSer-RBD:alum immunizations synergistically enhanced vaccine immunogenicity in mice and rhesus macaques, inducing neutralizing responses against SARS-CoV-2 variants. Thus, phosphate-mediated coanchoring of RBD and molecular adjuvants to alum is an effective strategy to enhance the efficacy of SARS-CoV-2 subunit vaccines.

Immunological memory to SARS-CoV-2 assessed for up to 8 months after infection

Understanding immune memory to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is critical for improving diagnostics and vaccines and for assessing the likely future course of the COVID-19 pandemic. We analyzed multiple compartments of circulating immune memory to SARS-CoV-2 in 254 samples from 188 COVID-19 cases, including 43 samples at ≥6 months after infection. Immunoglobulin G (IgG) to the spike protein was relatively stable over 6+ months. Spike-specific memory B cells were more abundant at 6 months than at 1 month after symptom onset. SARS-CoV-2-specific CD4+ T cells and CD8+ T cells declined with a half-life of 3 to 5 months. By studying antibody, memory B cell, CD4+ T cell, and CD8+ T cell memory to SARS-CoV-2 in an integrated manner, we observed that each component of SARS-CoV-2 immune memory exhibited distinct kinetics.

Modulating the quantity of HIV Env-specific CD4 T cell help promotes rare B cell responses in germinal centers

Immunodominance to nonneutralizing epitopes is a roadblock in designing vaccines against several diseases of high interest. One hypothetical possibility is that limited CD4 T cell help to B cells in a normal germinal center (GC) response results in selective recruitment of abundant, immunodominant B cells. This is a central issue in HIV envelope glycoprotein (Env) vaccine designs, because precursors to broadly neutralizing epitopes are rare. Here, we sought to elucidate whether modulating the quantity of T cell help can influence recruitment and competition of broadly neutralizing antibody precursor B cells at a physiological precursor frequency in response to Env trimer immunization. To do so, two new Env-specific CD4 transgenic (Tg) T cell receptor (TCR) mouse lines were generated, carrying TCR pairs derived from Env-protein immunization. Our results suggest that CD4 T cell help quantitatively regulates early recruitment of rare B cells to GCs.

Immunological memory to SARS-CoV-2 assessed for up to eight months after infection

Understanding immune memory to SARS-CoV-2 is critical for improving diagnostics and vaccines, and for assessing the likely future course of the COVID-19 pandemic. We analyzed multiple compartments of circulating immune memory to SARS-CoV-2 in 254 samples from 188 COVID-19 cases, including 43 samples at ≥ 6 months post-infection. IgG to the Spike protein was relatively stable over 6+ months. Spike-specific memory B cells were more abundant at 6 months than at 1 month post symptom onset. SARS-CoV-2-specific CD4 + T cells and CD8 + T cells declined with a half-life of 3-5 months. By studying antibody, memory B cell, CD4 + T cell, and CD8 + T cell memory to SARS-CoV-2 in an integrated manner, we observed that each component of SARS-CoV-2 immune memory exhibited distinct kinetics.

Exploration of roles of CD4 T cell help in recruitment of rare B cells to germinal centers

The elicitation of broadly neutralizing antibody (bnAb) responses is a major goal for developing an efficacious HIV vaccine. The HIV Env trimer is a weak immunogen, but it will be a necessary component in a HIV vaccine immunization schedule to drive affinity maturation to bnAbs. There are substantial biological challenges; bnAb precursor B cells are rare in humans, and B cell responses are typically directed to non-neutralizing immunodominant Env epitopes. HIV bnAb development relies heavily on germinal centers (GC) for affinity maturation. The survival of GC B cells is dependent on help from follicular helper CD4 T cells (TFH). Here, we have studied whether the modulation of TFH cells affect B cell immunodominance and competitiveness of rare B cells. We generated Env-specific TCR transgenic mice specific for a I-Ab MHCII epitope we mapped in Env. By utilizing our previously defined VRC01gHL B cell transfer model (Abbott et al., Immunity 2018), combined with co-transfer of CD4 T cells from our new Env-specific TCR transgenic mouse, we examined the competitive fitness of VRC01gHL B cells responding to Env antigens engineered to exhibit varying affinities for VRC01gHL. Increased availability of Env-specific CD4 T cells accelerated the initial expansion of GC VRC01gHL cells in response to a high affinity immunogen. However, improvements in early GC VRC01gHL cells were not observed for low affinity Env trimer immunogens. We are actively exploring whether slow delivery immunization strategies (Cirelli et al., Cell 2019) enhance the ability of Env-specific CD4 T cells to recruit rare VRC01-class B cells to GCs in mice.

Slow Delivery Immunization Enhances HIV Neutralizing Antibody and Germinal Center Responses via Modulation of Immunodominance

Conventional immunization strategies will likely be insufficient for the development of a broadly neutralizing antibody (bnAb) vaccine for HIV or other difficult pathogens because of the immunological hurdles posed, including B cell immunodominance and germinal center (GC) quantity and quality. We found that two independent methods of slow delivery immunization of rhesus monkeys (RMs) resulted in more robust T follicular helper (TFH) cell responses and GC B cells with improved Env-binding, tracked by longitudinal fine needle aspirates. Improved GCs correlated with the development of >20-fold higher titers of autologous nAbs. Using a new RM genomic immunoglobulin locus reference, we identified differential IgV gene use between immunization modalities. Ab mapping demonstrated targeting of immunodominant non-neutralizing epitopes by conventional bolus-immunized animals, whereas slow delivery-immunized animals targeted a more diverse set of epitopes. Thus, alternative immunization strategies can enhance nAb development by altering GCs and modulating the immunodominance of non-neutralizing epitopes.

Human Blood Monocyte Subsets: A New Gating Strategy Defined Using Cell Surface Markers Identified by Mass Cytometry

OBJECTIVE

Human monocyte subsets are defined as classical (CD14⁺⁺CD16^-), intermediate (CD14⁺⁺CD16⁺), and nonclassical (CD14⁺CD16⁺). Alterations in monocyte subset frequencies are associated with clinical outcomes, including cardiovascular disease, in which circulating intermediate monocytes independently predict cardiovascular events. However, delineating mechanisms of monocyte function is hampered by inconsistent results among studies.

APPROACH AND RESULTS

We use cytometry by time-of-flight mass cytometry to profile human monocytes using a panel of 36 cell surface markers. Using the dimensionality reduction approach visual interactive stochastic neighbor embedding (viSNE), we define monocytes by incorporating all cell surface markers simultaneously. Using viSNE, we find that although classical monocytes are defined with high purity using CD14 and CD16, intermediate and nonclassical monocytes defined using CD14 and CD16 alone are frequently contaminated, with average intermediate and nonclassical monocyte purity of ≈86.0% and 87.2%, respectively. To improve the monocyte purity, we devised a new gating scheme that takes advantage of the shared coexpression of cell surface markers on each subset. In addition to CD14 and CD16, CCR2, CD36, HLA-DR, and CD11c are the most informative markers that discriminate among the 3 monocyte populations. Using these additional markers as filters, our revised gating scheme increases the purity of both intermediate and nonclassical monocyte subsets to 98.8% and 99.1%, respectively. We demonstrate the use of this new gating scheme using conventional flow cytometry of peripheral blood mononuclear cells from subjects with cardiovascular disease.

CONCLUSIONS

Using cytometry by time-of-flight mass cytometry, we have identified a small panel of surface markers that can significantly improve monocyte subset identification and purity in flow cytometry. Such a revised gating scheme will be useful for clinical studies of monocyte function in human cardiovascular disease.

[A study on contamination from Legionella spp. at a home for the elderly in Toyohashi City]

OBJECTIVE

Legionnaires disease has been attributed to Legionella spp. in the water distribution systems of buildings. However, recently cases due to contamination of thermal-bath water have been reported in Japan. In this investigation, we examined the supervision of baths and the presence of Legionella spp. in thermal-bath water of homes for the elderly in Toyohashi city.

METHODS

The research was conducted through questionnaires on bathing facilities at 50 sites. Thermal baths were found to be installed at 14 of the sites. We then tested 22 samples from the 14 sites for Legionella spp. and other materials.

RESULTS

From the genus Legionella, only Legionella pneumophila was detected, in 8 samples from 4 sites. Coliforms were also detected. Moreover, disinfectant was not detected in any of the Legionella positive samples of bath water. Legionella positive sites had, however, been replacing their water once a day.

CONCLUSIONS

These findings indicate that the use of disinfectant and the proper supervision of bathing facilities are important in controlling Legionella spp. Legionnaires disease can be averted in homes for the elderly through appropriate measures.

Effect of acetate on glycogen replenishment in liver and skeletal muscles after exhaustive swimming in rats

Immediately after exhaustive swimming, rats were given one of the following orally: distilled water (W), glucose (G); acetic acid (A); citric acid (C); glucose and acetic acid (GA); and glucose and citric acid (GC), and they were killed 2 h after ingestion (each trial: n=4). Exhaustive exercise resulted in a significant reduction of the glycogen store in the gastrocnemius muscle. The glycogen stores in the liver were significantly higher following ingestion in groups GA and GC, in the gastrocnemius in groups G, GA and GC, and in the soleus in group GC, than immediately post exercise. These results suggest that oral acetic acid with glucose can facilitate liver glycogen restoration during the early period of recovery, and that acetate has about the same physiological effects as citrate on glycogen replenishment.

Regulation of glycolysis during acclimation of scallops (Patinopecten yessoensis Jay) to anaerobiosis

Some glycolytic metabolites in the adductor muscle were measured after transfer of scallops from aerobic to anaerobic saltwater for 12 h. The level of octopine increased gradually during the initial 3 h incubation, and thereafter the level increased rapidly up to 12 h. The ATP level also did not show any significant change for the initial 3 h, and then decreased rapidly. The fructose 2,6-biphosphate (Fru 2,6-BP) level increased drastically during the initial 3 h incubation, but thereafter the level did not show any significant change up to 12 h. In the short-term effects of anaerobiosis for 90 min, the level of fructose 6-phosphate (Fru 6-P) increased just after transfer to anaerobiosis, and then its level decreased. In contrast, the fructose 1,6-biphosphate (Fru 1,6-BP) level increased greatly, at the time when both glucose 6-phosphate (Glc 6-P) and Fru 6-P decreased. The Fru 2,6-BP level did not any significant change during the initial 15 min incubation, but thereafter the level increased gradually up to 90 min. Scallop 6-phosphofructo 1-kinase (EC 2.7.1.11) (PFK1) was strongly activated by 1 microM Fru 2,6-BP when 0.2 mM Fru 6-P was used as a substrate, but the activity was not affected at 5 mM Fru 6-P. In view of these results, the regulation mechanism of glycolysis is discussed.

Extracellular superoxide dismutase in tissues from obese (ob/ob) mice

We have examined the protein content and gene expression of three superoxide dismutase (SOD) isoenzymes in eight tissues from obese ob/ob mice, particularly placing the focus on extracellular-SOD (EC-SOD) in the white adipose tissue (WAT). Obesity significantly increased EC-SOD level in liver, kidney, testis, gastrocnemius muscle, WAT, brown adipose tissue (BAT), and plasma, but significantly decreased the isoenzyme level in lung. Tumor necrosis factor-alpha and interleukin-1beta contents in WAT were significantly higher in obese mice than in lean control mice. Immunohistochemically, both WAT and BAT from obese mice could be stained deeply with anti-mouse EC-SOD antibody compared with those from lean mice. Each primary culture per se almost time-dependently enhanced EC-SOD production, and overtly expressed its mRNA. The loss of heparin-binding affinity of EC-SOD type C with high affinity for heparin occurred in kidney of obese mice. These results suggest that the physiological importance of this SOD isoenzyme in WAT may be a compensatory adaptation to oxidative stress.

Effects of swimming training on three superoxide dismutase isoenzymes in mouse tissues

The purpose of the present study was to investigate the effects of swimming training on the changes in three superoxide dismutase (SOD) isoenzymes in mice. The trained mice underwent a 6-wk swimming program (1 h/day, 5 days/wk) in water at 35-36 degrees C. Immunoreactive extracellular SOD (EC-SOD), copper- and zinc-containing SOD (CuZn-SOD), and manganese-containing SOD (Mn-SOD) contents and their mRNA abundance were determined in serum, heart, lung, liver, kidney, and gastrocnemius muscle. EC-SOD content in liver and kidney was significantly increased with training. After training, CuZn-SOD content rose significantly only in kidney but decreased significantly in heart, lung, and liver. Mn-SOD content showed a significant increase in lung, kidney, and skeletal muscle but a significant decrease in liver. In most tissues, however, the changes in SOD isoenzyme contents were not concomitant with those in their mRNA levels. The results obtained thus suggest that, except for kidney, the responses in mouse tissues of three SOD isoenzymes (protein levels and mRNA abundance) to swimming training are different and that kidney may be one of the most sensitive organs to adapt to oxidative stress during physical training, although the mechanism remains vague.

Tissue distribution of immunoreactive mouse extracellular superoxide dismutase

Protein content and mRNA expression of extracellular superoxide dismutase (EC-SOD) were investigated in 16 mouse tissues. We developed a double-antibody sandwich ELISA using the affinity-purified IgG against native mouse EC-SOD. EC-SOD could be detected in all of the tissues examined (lung, kidney, testis, brown fat, liver, adrenal gland, pancreas, colon, white fat, thymus, stomach, spleen, heart, skeletal muscle, ileum, and brain, in decreasing order of content measured as microg/g wet tissue). Lung showed a markedly higher value of EC-SOD than other tissues. Interestingly, white fat had a high content of EC-SOD in terms of micrograms per milligram protein, which corresponded to that of lung. Kidney showed the strongest expression of EC-SOD mRNA. Relatively strong expression of the mRNA was observed in lung, white fat, adrenal gland, brown fat, and testis. Heart and brain showed only weak signals, and no such expression could be detected in either digestive organs or skeletal muscle. Immunohistochemically, EC-SOD was localized mainly to connective tissues and vascular walls in the tissues examined. Deep staining in the cytosol was observed in the cortical tubular cells of kidney. These results suggest that EC-SOD is distributed systemically in mice and that the physiological importance of this enzyme may be a compensatory adaptation to oxidative stress, particularly in lung and kidney.

Education of advanced practice nurses. Serving vulnerable populations

Vulnerable populations are camouflaged, stigmatized, and often lacking in health care services. They may also be distrustful of assistance from traditional health care providers. To better serve vulnerable populations, professionals guiding intervention programs need specialized knowledge and skills as well as problem-solving abilities.

[Blood biochemical properties in male workers analysed according to body type]

The characteristics of body type, serum lipids and blood pressure in male blue workers were evaluated. The subjects were 1,705 healthy men aged 40.3 +/- 4.33 years, and were classified into 4 groups according to body mass index: BMI; lean (group L: BMI < 20), normal (group N: 20 < or = BMI < 24), mildly obese (group MO: BMI 24 to 26.5) and obese group (group O: BMI > 26.5). The physical characteristics, blood pressure and 14 blood constituent items were measured. Groups L, N, MO and O accounted for 8.5, 53.4, 28.6, and 9.4% of all subjects, that is the obese body type (MO and O groups) occupied 38%. Rest systolic and diastolic blood pressure were positively related to BMI. Most blood constituent items biochemically analyzed increased in proportion to BMI values. The Trigriceride level was 88.5, 112.2, 152.8 and 171.9 mg/dl in groups L, N, MO and O, respectively. The Trigriceride level in groups MO and O were about the upper limit of the normal range. The total cholesterol level was in the normal range in 4 groups, but was higher in the MO and O groups than in groups L and N. The HDL-cholesterol level was low in inverse proportion to BMI, that is 58.2, 51.3, 47.6, and 42.6 mg/dl in groups L, N, MO, and O, respectively. Especially the values in group O were similar to the values in the aged and adult disease patients. A greater percentage of Japanese male workers were obese men and they risked developing atherosclerosis and adult diseases. the present study suggests that health education regarding exercise prescription and nutrition intake in daily life should be provided.

High-performance frontal analysis for the study of protein binding of troglitazone (CS-045) in albumin solution and in human plasma

An on-line frontal analysis HPLC system was developed for the determination of the unbound concentration of troglitazone (CS-045), a new oral antidiabetic agent, in human serum albumin (HSA) solution and in human plasma. This system consists of a high-performance frontal analysis (HPFA) column, an extraction column, and an analytical column, which are connected via two switching valves. After the direct injection of the sample solution into the HPFA column, the drug was eluted as a zonal peak with a plateau region. The unbound drug concentration was determined as the drug concentration in the plateau. As low as 0.3 nM unbound CS-045 was determined with good reproducibility. It was found that CS-045 strongly binds with HSA, and the bound fraction in the 550 microM HSA solution was 99.93%, which was very close to that in human plasma (99.89%). The bound fractions were constant within the total drug concentration range of 1-10 microM in the HSA solution and 250 nM-10 microM in human plasma.

Determination of the unbound concentration of hydrophobic drugs in albumin solutions by high-performance frontal analysis using a diol-silica column

High-performance frontal analysis (HPFA) using diol-silica column allows the determination of the unbound concentration of hydrophobic drugs under protein binding equilibrium, which is often difficult by the conventional methods. After the direct injection of a drug-protein mixed solution onto a diol-silica column, the drug is eluted as a zonal peak containing a plateau region under a mild mobile phase condition (phosphate buffer, pH 7.4, ionic strength = 0.17). The unbound drug concentration was determined as the drug concentration in the plateau region. The reliability of this method was confirmed by comparison with the results obtained by the conventional ultrafiltration-HPLC method. The versatility of the HPFA method using a diol-silica column was demonstrated by developing a novel on-line HPFA-chiral HPLC system for a simple and easy determination of the unbound concentration of nilvadipine (NV) enantiomers. The direct injection of 1.33 mL of a sample solution containing 20 nM-1 microM NV and 550 microM HSA gave the plateau region due to unbound NV, which was heart-cut and transferred on-line into a preconcentration and chiral HPLC separation system. As low as a few hundred picomolar level of unbound NV enantiomers was determined by use of UV detection (at 244 nm). The binding between NV and HSA is enantioselective; (R)-NV binds more strongly than (S)-NV.

Isolation and some properties of two fragments with inhibitory activity obtained from adzuki bean proteinase inhibitor by peptic digestion

Proteinase inhibitor II' from adzuki beans was subjected to peptic digestion. One of the resulting fragments, which inhibited chymotrypsin but not trypsin, was composed of 27 amino acid residues. The fragment was confirmed to be derived from the chymotrypsin-inhibitory domain of the original inhibitor. Another fragment, which inhibited trypsin only, contained 38 amino acid residues and consisted of two peptide chains. One of them, consisting of 25 amino acid residues, corresponded to the original reactive site region for trypsin. These fragments were also obtained from inhibitor II by peptic digestion. These findings, confirm that these inhibitors, which do not inhibit chymotrypsin and trypsin simultaneously, have separate and independent domains for the inhibition of each enzyme. The active fragments are homologous in chemical structures with the two fragments from soybean Bowman-Birk proteinase inhibitor. However, unlike the fragments from Bowman-Birk inhibitor, our chymotrypsin-inhibitory fragment was a potent inhibitor of the enzyme and was as resistant as the intact inhibitor to the attack of excess chymotrypsin. The trypsin-inhibitory fragment had a lower anti-tryptic action than the original inhibitor and was gradually inactivated by trypsin. These differences between our fragments and those of the Bowman-Birk inhibitor are probably a result of the replacement of a few amino acid residues in the reactive site regions.

Characterization of poliovirus isolates in Japan after the mass vaccination with live oral poliomyelitis vaccine (Sabin)

From 1962 to 1968, 127 poliovirus isolates (92 from clinical specimens and 35 from healthy subjects) were subjected to intratypic serodifferentiation by the modified Wecker and McBride techniques. The two techniques gave concordant results for 103 strains, 91 of which were classified as vaccine-like, 9 as nonvaccine-like, and 3 as intermediate; 20 were classified as vaccine-like by one technique and as intermediate by the other, and 4 as nonvaccine-like by one technique and as intermediate by the other. The origin of the nonvaccine-like strains is unknown, but it is unlikely that they had been circulating in the community long. An rct/40-marker test of the isolates revealed a higher positivity rate than that found in field trials of Sabin vaccine. The results indicate that wild poliovirus has been almost completely eradicated from Japan.