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BACKGROUND. Intravenous Ig (IVIg), plasma exchange, and immunoadsorption are frequently used in the management of severe autoimmune diseases mediated by pathogenic IgG autoantibodies. These approaches modulating IgG levels can, however, be associated with some severe adverse reactions and a substantial burden to patients. Targeting the neonatal Fc receptor (FcRn) presents an innovative and potentially more effective, safer, and more convenient alternative for clearing pathogenic IgGs. METHODS. A randomized, double-blind, placebo-controlled first-in-human study was conducted in 62 healthy volunteers to explore single and multiple ascending intravenous doses of the FcRn antagonist efgartigimod. The study objectives were to assess safety, tolerability, pharmacokinetics, pharmacodynamics, and immunogenicity. The findings of this study were compared with the pharmacodynamics profile elicited by efgartigimod in cynomolgus monkeys. RESULTS. Efgartigimod treatment resulted in a rapid and specific clearance of serum IgG levels in both cynomolgus monkeys and healthy volunteers. In humans, single administration of efgartigimod reduced IgG levels up to 50%, while multiple dosing further lowered IgGs on average by 75% of baseline levels. Approximately 8 weeks following the last administration, IgG levels returned to baseline. Efgartigimod did not alter the homeostasis of albumin or Igs other than IgG, and no serious adverse events related to efgartigimod infusion were observed. CONCLUSION. Antagonizing FcRn using efgartigimod is safe and results in a specific, profound, and sustained reduction of serum IgG levels. These results warrant further evaluation of this therapeutic approach in IgG-driven autoimmune diseases. TRIAL REGISTRATION. Clinicaltrials.gov {"type":"clinical-trial","attrs":{"text":"NCT03457649","term_id":"NCT03457649"}}NCT03457649. FUNDING. argenx BVBA.

This study examines the feasibility of marking Lygus hesperus Knight adults externally by submersion in rabbit immunoglobulin G(IgG) solution. Rabbit IgG retention time was measured in the laboratory on insects submerged in an IgG solution. We marked insects with rabbit IgG and ran an enzyme-linked immunosorbent assay (ELISA) with its complementary antibody (antirabbit IgG). We concurrently ran an ELISA assay using the same samples against an egg-specific L. hesperus monoclonal antibody (MAb)to measure the presence of L. hesperus egg antigen in the insect. A previously developed egg-specific MAb to L. hesperus enabled us to assay simultaneously adult females (which possess the egg antigen) and adult males for the presence of L. hesperus egg antigen. This combination of techniques will enable us to examine the gut contents of potential predators of L. hesperus eggs or adult females using whole body macerates while simultaneously evaluating the efficiency of lab-reared predators for augmentative biological control.

Development of murine monoclonal antibodies to weakly immunogenic antigens was accomplished by combining both in vivo and in vitro immunizations. Following immunization of mice with Treponema hyodysenteriae outer membrane antigens, Manduca sexta apolipoproteins, and Drosophila melanogaster DNA polymerase, respectively, a significant increase in percentage of antibody-producing hybrids were identified when immune spleens were subjected to an in vitro immunization prior to fusion with SP2/0 myeloma cells. The hybrids developed, produced Abs to a T. hyodysenteriae 14 Kd carbohydrate, M. sexta apolipoproteins I, II, and III, and D. melanogaster DNA polymerase. The use of both in vivo and in vitro immunizations may increase the likelihood of generating monoclonal antibodies to weakly immunogenic antigens.

Infections with Encephalitozoon (phylum Microspora) protozoa in immunodeficient patients have emerged worldwide. The prevalence of infections due to Encephalitozoon species in nonclinical populations remains unclear. We conducted a cross-sectional survey of two rural highland villages in Mexico by using monoclonal antibody 3B6 to Encephalitozoon in immunofluorescence to assess the prevalence of Encephalitozoon spores in human stools. We found that 20 (7.84%) of the 255 subjects were positive and that 15 (21.4%) of the 70 households had at least one member who was positive. These results suggest that Encephalitozoon species, most likely Encephalitozoon intestinalis, may be commonly present in community settings.

Differences in susceptibility to persistent cryptosporidial infection between two strains of adult athymic nude mice prompted us to investigate the immune mechanism(s) that may control resistance to infection in these T-cell-deficient mice. We studied fecal oocyst shedding, serum and fecal parasite-specific antibody responses, and fecal immunoglobulin levels in athymic C57BL/6J nude and athymic BALB/cJ nude mice following oral inoculation with Cryptosporidium parvum oocysts at 8 to 9 weeks of age. C57BL/6J nude mice had significantly higher fecal parasite-specific immunoglobulin A (IgA) (days 27, 31, 35, and 42 postinoculation) and IgM (days 10, 17, 24, 28, 31, 38, 42, and 48 postinoculation) levels than BALB/cJ nude mice ( P < 0.05) and significantly higher serum parasite-specific IgA levels at 63 days postinoculation ( P < 0.03). Moreover, C57BL/6J nude mice shed significantly fewer C. parvum oocysts than BALB/cJ nude mice from days 52 to 63 postinoculation ( P < 0.05). In contrast, BALB/cJ nude mice had higher levels of non-parasite-specific IgA (days 38 to 63 postinoculation) and IgM (days 24, 35, 38, and 52 postinoculation) than C57BL/6J nude mice in feces ( P < 0.05). These data suggest that parasite-specific fecal antibodies may be associated with resistance to C. parvum in C57BL/6J nude mice.

Cryptosporidium parvum is an important diarrhea-causing protozoan parasite of immunocompetent and immunocompromised hosts. Immunoglobulin A (IgA) has been implicated in resistance to mucosal infections with bacteria, viruses, and parasites, but little is known about the role of IgA in the control of C. parvum infection. We assessed the role of IgA during C. parvum infection in neonatal mice. IgA-secreting hybridomas were developed by using Peyer’s patch lymphocytes from BALB/c mice which had been orally inoculated with viable C. parvum oocysts. Six monoclonal antibodies (MAbs) were selected for further study based on indirect immunofluorescence assay reactivity with sporozoite and merozoite pellicles and the antigen (Ag) deposited on glass substrate by gliding sporozoites. Each MAb was secreted in dimeric form and recognized a 23-kDa sporozoite Ag in Western immunoblots. The Ag recognized comigrated in sodium dodecyl sulfate-polyacrylamide gel electrophoresis with P23, a previously defined neutralization-sensitive zoite pellicle Ag. MAbs were evaluated for prophylactic or therapeutic efficacy against C. parvum , singly and in combinations, in neonatal BALB/c mice. A combination of two MAbs given prophylactically prior to and 12 h following oocyst challenge reduced the number of intestinal parasites scored histologically by 21.1% compared to the numbers in mice given an isotype-matched control MAb ( P < 0.01). Individual MAbs given therapeutically in nine doses over a 96-h period following oocyst challenge increased efficacy against C. parvum infection. Four MAbs given therapeutically each reduced intestinal infection 34.4 to 42.2% compared to isotype-matched control MAb-treated mice ( P < 0.05). One MAb reduced infection 63.3 and 72.7% in replicate experiments compared to isotype-matched control MAb-treated mice ( P < 0.0001). We conclude that IgA MAbs directed to neutralization-sensitive P23 epitopes may have utility in passive immunization against murine C. parvum infection.

The humoral antibody responses to salivary antigens of Simulium vittatum Zetterstedt were investigated in a BALB/c mouse laboratory model. Production of antisera was stimulated by intraperitoneal immunization with salivary gland extract or by feeding flies directly on depilated mice. Antibody responses in these two groups of mice were compared by western blotting, thus characterizing “true” salivary immunogens present in salivary gland extract. Immunized mice developed IgG, IgM, and IgE antibodies which recognized several salivary gland components, ranging in molecular weight between 26 and 67 kDa. Sera from bitten mice recognized fewer antigens, indicating that some components of the salivary gland extract were poorly immunogenic or absent from the saliva secreted during blood feeding. Antisera raised against S. vittatum also were used to identify cross-reactive immunogens and allergens in salivary gland extracts from other New World simuliids ( Simulium argus Williston, S. metallicum Bellardi, and S. ochraceum Walker). SDS—PAGE protein profiles indicated a high degree of similarity between salivary gland extract of S. vittatum and S. argus, and several cross-reacting antigens were identified by western blotting. In contrast, protein profiles of S. ochraceum and S. metallicum differed from the former species, both qualitatively and quantitatively. Antisera demonstrated a low degree of cross-reactivity against salivary gland extract of S. ochraceum, whereas no cross-reactivity was detected against S. metallicum. These observations were confirmed using a monoclonal antibody raised against S. vittatum salivary gland extract (designated SVSG.1.F10), which showed cross-reactivity against S. argus but failed to recognize salivary gland components of either S. ochraceum or S. metallicum.