Circulating Levels of sFlt1 Splice Variants as Predictive Markers for the Development of Preeclampsia.

Angiogenic biomarkers, including soluble fms-like tyrosine kinase 1 (sFlt1), are thought to be predictors of preeclampsia onset; however, improvement is needed before a widespread diagnostic test can be utilized. Here we describe the development and use of diagnostic monoclonal antibodies specific to the two main splice variants of sFlt1, sFlt1-1 and sFlt1-14. These antibodies were selected for their sensitivity and specificity to their respective sFlt1 isoform in a capture ELISA format. Data from this pilot study suggest that sFlt1-1 may be more predictive of preeclampsia than total sFlt1. It may be possible to improve current diagnostic platforms if more specific antibodies are utilized.

Identification of a human monoclonal antibody to replace equine diphtheria antitoxin for treatment of diphtheria intoxication.

Diphtheria antitoxin (DAT) has been the cornerstone of the treatment of Corynebacterium diphtheriae infection for more than 100 years. Although the global incidence of diphtheria has declined steadily over the last quarter of the 20th century, the disease remains endemic in many parts of the world, and significant outbreaks still occur. DAT is an equine polyclonal antibody that is not commercially available in the United States and is in short supply globally. A safer, more readily available alternative to DAT would be desirable. In the current study, we obtained human monoclonal antibodies (hMAbs) directly from antibody-secreting cells in the circulation of immunized human volunteers. We isolated a panel of diverse hMAbs that recognized diphtheria toxoid, as well as a variety of recombinant protein fragments of diphtheria toxin. Forty-five unique hMAbs were tested for neutralization of diphtheria toxin in in vitro cytotoxicity assays with a 50% effective concentration of 0.65 ng/ml for the lead candidate hMAb, 315C4. In addition, 25 µg of 315C4 completely protected guinea pigs from intoxication in an in vivo lethality model, yielding an estimated relative potency of 64 IU/mg. In comparison, 1.6 IU of DAT was necessary for full protection from morbidity and mortality in this model. We further established that our lead candidate hMAb binds to the receptor-binding domain of diphtheria toxin and physically blocks the toxin from binding to the putative receptor, heparin-binding epidermal growth factor-like growth factor. The discovery of a specific and potent human neutralizing antibody against diphtheria toxin holds promise as a potential therapeutic.

Human monoclonal antibody HCV1 effectively prevents and treats HCV infection in chimpanzees.

Hepatitis C virus (HCV) infection is a leading cause of liver transplantation and there is an urgent need to develop therapies to reduce rates of HCV infection of transplanted livers. Approved therapeutics for HCV are poorly tolerated and are of limited efficacy in this patient population. Human monoclonal antibody HCV1 recognizes a highly-conserved linear epitope of the HCV E2 envelope glycoprotein (amino acids 412-423) and neutralizes a broad range of HCV genotypes. In a chimpanzee model, a single dose of 250 mg/kg HCV1 delivered 30 minutes prior to infusion with genotype 1a H77 HCV provided complete protection from HCV infection, whereas a dose of 50 mg/kg HCV1 did not protect. In addition, an acutely-infected chimpanzee given 250 mg/kg HCV1 42 days following exposure to virus had a rapid reduction in viral load to below the limit of detection before rebounding 14 days later. The emergent virus displayed an E2 mutation (N415K/D) conferring resistance to HCV1 neutralization. Finally, three chronically HCV-infected chimpanzees were treated with a single dose of 40 mg/kg HCV1 and viral load was reduced to below the limit of detection for 21 days in one chimpanzee with rebounding virus displaying a resistance mutation (N417S). The other two chimpanzees had 0.5-1.0 log(10) reductions in viral load without evidence of viral resistance to HCV1. In vitro testing using HCV pseudovirus (HCVpp) demonstrated that the sera from the poorly-responding chimpanzees inhibited the ability of HCV1 to neutralize HCVpp. Measurement of antibody responses in the chronically-infected chimpanzees implicated endogenous antibody to E2 and interference with HCV1 neutralization although other factors may also be responsible. These data suggest that human monoclonal antibody HCV1 may be an effective therapeutic for the prevention of graft infection in HCV-infected patients undergoing liver transplantation.

The roles of MAD1, MAD2 and MAD3 in meiotic progression and the segregation of nonexchange chromosomes.

Errors in meiotic chromosome segregation are the leading cause of spontaneous abortions and birth defects. In humans, chromosomes that fail to experience crossovers (or exchanges) are error-prone, more likely than exchange chromosomes to mis-segregate in meiosis. We used a yeast model to investigate the mechanisms that partition nonexchange chromosomes. These studies showed that the spindle checkpoint genes MAD1, MAD2 and MAD3 have different roles. We identified a new meiotic role for MAD3; though dispensable for the segregation of exchange chromosomes, it is essential for the segregation of nonexchange chromosomes. This function of Mad3p could also be carried out by human BubR1. MAD1 and MAD2 act in a surveillance mechanism that mediates a metaphase delay in response to nonexchange chromosomes, whereas MAD3 acts as a crucial meiotic timer, mediating a prophase delay in every meiosis. These findings suggest plausible models for the basis of errant meiotic segregation in humans.