A series of potent, broadly neutralizing HIV antibodies have been isolated from B cells of HIV-infected individuals. VRC01 represents a subset of these antibodies that mediate neutralization with a ...restricted set of IGHV genes. The memory B cells expressing these antibodies were isolated years after infection; thus, the B-cell subpopulation from which they originated and the extent of participation in the initial HIV antibody response, if any, are unclear. Here we evaluated the frequency of anti-gp120 B cells in follicular (FO) and marginal zone (MZ) B-cell compartments of naïve WT mice and comparable human populations in uninfected individuals. We found that in non–HIV-exposed humans and mice, the majority of gp120-reactive B cells are of naïve and FO phenotype, respectively. Murine FO B cells express a diverse antibody repertoire to recognize gp120. In contrast, mouse MZ B cells recognize gp120 less frequently but preferentially use IGHV1-53 to encode gp120-specific antibodies. Notably, IGHV1-53 shows high identity to human IGHV1-2 * 02 , which has been repeatedly found to encode broadly neutralizing mutated HIV antibodies, such as VRC01. Finally, we show that human MZ-like B cells express IGHV1-2 *02 , and that IGHV1-53 expression is enriched in mouse MZ B cells. These data suggest that efforts toward developing an HIV vaccine might consider eliciting protective HIV antibody responses selectively from alternative B-cell populations harboring IGHV gene segments capable of producing protective antibodies.
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Background:
Success in conducting clinical trials during the coronavirus disease of 2019 pandemic requires the ability to innovate and adapt. There are well-established procedures for the blinding of ...investigational agents, especially medications, in placebo-controlled randomized clinical trials within the Veterans Health Administration. However, these procedures, managed by research pharmacists, may not apply to investigational agents that are not exclusively managed by pharmacy, such as blood products, including coronavirus disease of 2019 convalescent plasma (plasma). In the absence of established blinding procedures, such studies require special design considerations to minimize uncertainty or bias.
Methods:
We describe the processes and procedures developed for blinding of plasma in “Veterans Affairs CoronavirUs Research and Efficacy Studies-1” as a prototypical study using this class of investigational therapeutic agents. Veterans Affairs CoronavirUs Research and Efficacy Studies-1 is an ongoing multicenter randomized clinical trial testing the efficacy of plasma added to conventional therapy for severe acute respiratory syndrome coronavirus-2 infection.
Results:
We report the design of procedures to supply investigational blood products or 0.9% normal saline (saline) control while ensuring the integrity of the blind. Key aspects include workflow considerations, physical blinding strategies, and methods for engaging stakeholders. These procedures leverage the well-established Veterans Affairs research pharmacist’s research infrastructure, and Blood Bank Services, which is responsible for blood-based investigational products.
Conclusion:
By describing the methods used to deliver blood products in a blinded manner in Veterans Affairs CoronavirUs Research and Efficacy Studies-1, we strive both to educate and to increase awareness to improve the implementation of these biological therapeutics for future, high-quality research studies.
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IgA1 proteases (IgA1P) from diverse pathogenic bacteria specifically cleave human immunoglobulin A1 (IgA1) at the hinge region, thereby thwarting protective host immune responses. Streptococcus ...pneumoniae (S. pneumoniae) IgA1P shares no sequence conservation with serine or cysteine types of IgA1Ps or other known proteins, other than a conserved HExxH Zn‐binding motif (1604‐1608) found in metalloproteases. We have developed a novel expression system to produce the mature S. pneumoniae IgA1P and we have discovered that this form is both attached to the bacterial cell surface and released in its full form. Our data demonstrate that the S. pneumoniae IgA1P comprises two distinct regions that associate to form an active metalloprotease, the first such example of a metalloprotease that can be split in vitro and recombined to form an active enzyme. By capitalizing on this novel domain architecture, we show that the N‐terminal region of S. pneumoniae IgA1P comprises the primary binding region for IgA1, although the C‐terminal region of S. pneumoniae IgA1P is necessary for cleavage of IgA1. Our findings lend insight into the protein domain architecture of the S. pneumoniae IgA1P and function of this important virulence factor for S. pneumoniae infection.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Background. Among infants exposed to human immunodeficiency virus (HIV) type 1, mixed breastfeeding is associated with higher postnatal HIV-1 transmission than exclusive breastfeeding, but the ...mechanisms of this differential risk are uncertain. Methods. HIV-1–exposed Ugandan infants were prospectively assessed during the first year of life for feeding practices and T-cell maturation, intestinal homing (β7ʰⁱ), activation, and HIV-1 coreceptor (CCR5) expression in peripheral blood. Infants receiving only breast milk and those with introduction of other foods before 6 months were categorized as exclusive and nonexclusive, respectively. Results. Among CD4⁺ and CD8⁺ T cells, the expression of memory, activation, and CCR5 markers increased rapidly from birth to week 2, peaking at week 6, whereas cells expressing the intestinal homing marker increased steadily in the central memory (CM) and effector memory T cells over 48 weeks. At 24 weeks, when feeding practices had diverged, nonexclusively breastfed infants showed increased frequencies and absolute counts of β7ʰⁱ CM CD4⁺ and CD8⁺ T cells, including the HIV-1–targeted cells with CD4⁺β7ʰⁱ/CCR5⁺ coexpression, as well as increased activation. Conclusions. The T-cell phenotype associated with susceptibility to HIV-1 infection (CCR5⁺, gut-homing, CM CD4⁺ T cells) was preferentially expressed in nonexclusively breastfed infants, a group of infants at increased risk for HIV-1 acquisition.
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Identifying HIV-1-associated B cell defects and responses to activation may direct interventions to circumvent their impaired antibody responses to infection and vaccines.
Among 34 viremic ...HIV-1-infected and 20 seronegative control adults, we measured baseline frequencies and activation of B and T cell subsets, expression of activation-induced cytidine deaminase (AID), potential determinants of B cell activation in vivo and B and T cell responses in vitro.
At baseline, HIV-1 infection was associated with increased IgM memory and decreased anergic cell frequencies, as well as increased activation in all 10 B cell subsets compared with controls. HIV-1 status, TFH activation, and BAFF were significant potential drivers of B cell activation. Despite high baseline activation among HIV-1-infected subjects, stimulation in vitro with combined surrogates for antigen (anti-IgM), cognate (CD40 ligand) and soluble T cell factors (IL-4) elicited comparable B cell activation, transitions from naïve to class-switched memory cells and AID expression in both groups.
In summary, viremic HIV-1 infection perturbs circulating B cell subsets and activation at each stage of B cell maturation. However, that appropriate stimulation of B cells elicits effective activation and maturation provides impetus for advancing vaccine development to prevent secondary infections by circumventing early B cell defects.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK, ZRSKP
BACKGROUND:Mother-to-child transmission (MTCT) of HIV remains a significant problem in resource-limited settings, despite the advent of antiretroviral therapies. Because perturbations in vaginal ...microbial communities are associated with sexual transmission of HIV, we determined whether perinatal MTCT is associated with the vaginal microbiotas of HIV-infected mothers.
METHODS:We conducted a retrospective analysis of cervicovaginal microbiotas by pyrosequencing of bacterial 16S rRNA genes (median 350 sequences per sample) from 10 transmitters and 54 nontransmitters during a perinatal MTCT prevention clinical trial of azidothymidine and the microbicide benzalkonium chloride. Logistic regression was performed adjusting for multiple covariates, including CD4 T-cell numbers and treatment group, to correlate abundances of microbial taxa with perinatal MTCT.
RESULTS:The vaginal microbiotas of these subjects were dominated by several lactobacilli species, although a subset of subjects was colonized by diverse anaerobic species. MTCT of HIV was associated with significantly greater relative abundances of several groups of microorganisms. Most notably, among the abundant bacterial species, Gardnerella vaginalis was significantly enriched in cases of antepartum transmission, compared with nontransmission (odds ratio 1.7; P = 0.004). Neither azidothymidine nor benzalkonium chloride treatment was associated with shifts in microbial distributions compared with the placebo control group.
CONCLUSIONS:These data suggest that alterations in vaginal microbial communities are associated with an increased risk for perinatal MTCT, consistent with results with horizontal transmission of HIV. Therefore, determining the mucosal features associated with alterations in vaginal microbial communities may guide efforts to modulate the risk for HIV MTCT.
Breast-feeding and Transmission of HIV-1 John-Stewart, Grace; Mbori-Ngacha, Dorothy; Ekpini, Rene ...
Journal of acquired immune deficiency syndromes (1999),
2004-February-1, Volume:
35, Issue:
2
Journal Article
Peer reviewed
Open access
Breast-feeding substantially increases the risk of HIV-1 transmission from mother to child, and although peripartum antiretroviral therapy prophylaxis significantly decreases the risk of ...mother-to-child transmission around the time of delivery, this approach does not affect breast-feeding transmission. Increased maternal RNA viral load in plasma and breast milk is strongly associated with increased risk of transmission through breast-feeding, as is breast health, and it has been suggested that exclusive breast-feeding could be associated with lower rates of breast-feeding transmission than mixed feeding of both breast- and other milk or feeds. Transmission through breast-feeding can take place at any point during lactation, and the cumulative probability of acquisition of infection increases with duration of breast-feeding. HIV-1 has been detected in breast milk in cell-free and cellular compartments; infant gut mucosal surfaces are the most likely site at which transmission occurs. Innate and acquired immune factors may act most effectively in combination to prevent primary HIV-1 infection by breast milk.
To determine whether immune function is impaired among HIV-exposed but -uninfected (HEU) infants born to HIV-infected mothers and to identify potential vulnerabilities to vaccine-preventable ...infection, we characterized the mother-to-infant placental transfer of Haemophilus influenzae type b-specific IgG (Hib-IgG) and its levels and avidity after vaccination in Ugandan HEU infants and in HIV-unexposed U.S. infants. Hib-IgG was measured by enzyme-linked immunosorbent assay in 57 Ugandan HIV-infected mothers prenatally and in their vaccinated HEU infants and 14 HIV-unexposed U.S. infants at birth and 12, 24, and 48 weeks of age. Antibody avidity at birth and 48 weeks of age was determined with 1 M ammonium thiocyanate. A median of 43% of maternal Hib-IgG was transferred to HEU infants. Although its level was lower in HEU infants than in U.S. infants at birth (P < 0.001), Hib-IgG was present at protective levels (>1.0 μg/ml) at birth in 90% of HEU infants and all U.S. infants. HEU infants had robust Hib-IgG responses to a primary vaccination. Although Hib-IgG levels declined from 24 to 48 weeks of age in HEU infants, they were higher than those in U.S. infants (P = 0.002). Antibody avidity, comparable at birth, declined by 48 weeks of age in both populations. Early vaccination of HEU infants may limit an initial vulnerability to Hib disease resulting from impaired transplacental antibody transfer. While initial Hib vaccine responses appeared adequate, the confluence of lower antibody avidity and declining Hib-IgG levels in HEU infants by 12 months support Hib booster vaccination at 1 year. Potential immunologic impairments of HEU infants should be considered in the development of vaccine platforms for populations with high maternal HIV prevalence.
Summary
Most clinical isolates of Streptococcus pneumoniae consist of heterogeneous populations of at least two colony phenotypes, opaque and transparent, selected for in the bloodstream and ...nasopharynx, respectively. Microarray analysis revealed 24 orfs that demonstrated differences in expression greater than twofold between variants of independent strains. Twenty‐one of these showed increased expression in the transparent variants, including 11 predicted to be involved in sugar metabolism. A single genomic region contains seven of these loci including the gene that encodes the neuraminidase, NanA. In contrast to previous studies, there was no contribution of NanA to adherence of S. pneumoniae to epithelial cells or colonization in an animal model. However, we observed NanA‐dependent desialylation of human airway components that bind to the organism and may mediate bacterial clearance. Targets of desialylation included human lactoferrin, secretory component, and IgA2 that were shown to be present on the surface of the pneumococcus in vivo during pneumococcal pneumonia. The efficiency of desialylation was increased in the transparent variants and enhanced for host proteins binding to the surface of S. pneumoniae. Because deglycosylation affects the function of many host proteins, NanA may contribute to a protease‐independent mechanism to modify bound targets and facilitate enhanced survival of the bacterium.
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