Methicillin-resistant S. aureus (MRSA) frequently causes disease outbreaks and has become endemic in many regions, adding to the morbidity, mortality, and cost of care associated with hospital-acquired infections. Enhanced surveillance and infection control measures have been adopted by healthcare institutions (HCIs) to address this unresolved problem (5). In particular, reporting of bloodstream infections (BSI) by MRSA is often mandatory and reduction of BSI rates is a performance target (5,12,21).In the Centre region of France, an extensive, prospective, longitudinal, region-wide survey of BSI has been under way since 2000. Data are collected for 3 months of each year in a large number of HCIs to establish a comprehensive picture of the epidemiology of severe hospital-acquired infections. MRSA BSI and methicillin-sensitive S. aureus (MSSA) BSI are extensively studied within this framework. All of the S. aureus strains isolated during successive study periods are sent to our central laboratory for susceptibility testing, molecular typing, and analysis of virulence genes with the aim of determining the spread and diversity of S. aureus strains in the region. The results obtained during the first 4 years of surveillance (2000 to 2003) of MRSA BSI have been reported previously (27).Here we report the data from 2004 to 2006. We looked for any major changes in the epidemiology of antibiotic resistance and of virulence genes in strains of S. aureus responsible for BSI. We identify a need to focus efforts on preventing both MRSA and MSSA BSI infections and raise the issue of whether the use of fluoroquinolones (FQs) has contributed to the acquisition of resistance and virulence genes by S. aureus strains. MATERIALS AND METHODSBSI epidemiological survey method. A BSI surveillance program in the Centre region of France (2.5 million inhabitants) and a microbiological study of S. aureus strains isolated from BSI cases have been conducted since 2000. Thirtytwo HCIs, comprising 6,027 short-stay beds, participated in this annual 3-month survey of all cases of BSI. Here, we report results for the years 2004 to 2006. The survey covered 2,007,681 patient days (PD). The methods, study design, and data for the years 2000 to 2003 have been reported elsewhere (27). Briefly, the variables studied included patient age and sex, portal of entry, community-or hospital-acquired BSI, occurrence of death within 7 days of BSI diagnosis, and duration of hospital stay. Data were analyzed with Epi Info v.6 software. Data were analyzed with a 2 test with five degrees of freedom. The incidences of community-acquired and nosocomial BSI were determined with respect to the number of PD.Microbiological methods. (i) Bacteriology. Three hundred fifty-eight BSIassociated S. aureus strains were collected during the three survey periods (2004, 2005, and 2006). The strains were sent to the reference laboratory of the Relais d'Hygiène du Centre. The isolates were identified as S. aureus according to previously described procedures (27).(ii) Antimicrobial ...

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In order to treat Toll like receptor 4 (TLR4)-mediated diseases, we generated a potent antagonistic antibody directed against human TLR4, Hu 15C1. This antibody's potency can be modulated by engaging not only TLR4 but also Fcg receptors (FcgR), a mechanism that is driven by avidity and not cell signaling. Here, using various formats of the antibody, we further dissect the relative contributions of the Fv and Fc portions of Hu 15C1, discovering that the relationship to potency of the different antibody arms is not linear. First, as could be anticipated, we observed that Hu 15C1 co-engages up to 3 receptors on the same plasma membrane, i.e., 2 TLR4 molecules (via its variable regions) and either FcgRI or FcgRIIA (via the Fc). The K d of these interactions are in the nM range (3 nM of the Fv for TLR4 and 47 nM of the Fc for FcgRI). However, unexpectedly, neutralization experiments revealed that, due to the low level of cell surface TLR4 expression, the avidity afforded by engagement through 2 Fv arms was significantly limited. In contrast, the antibody's neutralization capacity increases by 3 logs when able to exploit Fc-FcgR interactions. Taken together, these results demonstrate an unforeseen level of contribution by FcgRs to an antibody's effectiveness when targeting a cell surface protein of relatively low abundance. These findings highlight an exploitable mechanism by which FcgRbearing cells may be more powerfully targeted, envisioned to be broadly applicable to other reagents aimed at neutralizing cell surface targets on cells co-expressing FcgRs.

ISB 1442 is a bispecific antibody (BsAb) using Ichnos' proprietary Bispecific Engagement by Antibodies based on the T-cell receptor (BEAT ®) platform. A fully human BsAb with anti-CD38 and CD47 binding arms, ISB 1442 was developed for the treatment of relapsed/refractory multiple myeloma (rrMM). The CD38 binding arm consists of two bi-paratopic Fabs that strongly bind to CD38 through avidity-induced interactions. The anti-CD47 arm comprises a single Fab arm designed to block the interaction between CD47 and the signal-regulatory protein alpha (SIRPα) receptor present on phagocytes (including macrophages, monocytes and dendritic cells). With this design, the CD38 Fab arm preferentially drives binding to tumor cells and enables blocking of proximal CD47 receptors on the same cell via avidity-induced binding. Hence, ISB 1442 is anticipated to induce minimal unintended effects on red blood cell (RBC) hemagglutination compared to benchmark anti-CD47 monoclonal antibodies (mAb) magrolimab. The Fc portion of ISB 1442 is engineered to enhance antibody dependent cell phagocytosis (ADCP), antibody dependent cell cytotoxicity (ADCC) and complement dependent cytotoxicity (CDC). ISB 1442 is the first-in-class with these unique molecular attributes, which are designed to overcome mechanisms of resistance to daratumumab in rrMM patients. In vitro, ISB 1442 exhibited a higher killing potency compared to benchmark daratumumab across a broad range of CD38-expressing tumor cells. Specifically, ISB 1442 showed a high potency to kill CD38 high tumor cells through CDC and a superior potency to kill CD38 low expressing tumor cells through ADCC and ADCP compared to daratumumab. Additionally, ISB 1442 showed in vitro tumor killing potency through phagocytosis comparable to magrolimab, an anti-CD47 mAb (IgG4) acting mostly through ADCP. Consistent with its molecular design, which includes a functional Fc, ISB 1442 induced more potent killing of CD38 high and CD38 low tumor cells by CDC and ADCC compared to magrolimab. To characterize the complex mechanisms of action of ISB 1442 in a single system more fully, a multiple mode of action of killing (MMoAK) in vitro assay was established where autologous macrophages and PBMCs from healthy donors were incubated with CD38 low expressing tumor cells and human serum. With this approach, tumor cells can be targeted simultaneously by NK cells from PBMCs, autologous macrophages, and complement from human serum. In MMoAK, ISB 1442 exhibited prominent tumor cell killing that was twice as high as daratumumab. The presence of soluble CD38 or RBCs, the main source of antigen sinks for CD38 and CD47, did not affect the killing potency of ISB 1442 across in vitro assays using CD38 high or CD38 low expressing tumor cells. These data suggest that the molecular design of ISB 1442 mitigates the potential risk of CD47 and CD38 antigen sink and the related side effects. On-target specificity was evaluated in vitro by measuring binding to human RBCs, induction of hemagglutination and RBC depletion, hemolysis and platelet aggregation. ISB 1442 did not cause any detectable hemolysis, RBC depletion or platelet aggregation in vitro and showed a marked reduction in human RBC hemagglutination relative to magrolimab, suggesting a more favorable on-target specificity profile. Finally, the potency of ISB 1442 was assessed in vivo in a therapeutic model of subcutaneously established Raji tumor xenograft in CB17/SCID mice which have functional complement, macrophages and NK cells of murine origin. ISB 1442 induced higher tumor growth inhibition relative to daratumumab and comparable tumor regression compared to magrolimab. In summary, we report a novel approach for the treatment for rrMM by co-targeting CD38 and CD47 using a 2+1 biparatopic bispecific antibody. Based on its unique design and multiple mechanisms of action, ISB 1442 is anticipated to enhance antitumor activity in rrMM patients relative to anti-CD38 mAbs by overcoming primary and acquired tumor escape mechanisms of resistance. Disclosures No relevant conflicts of interest to declare.

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