Anti-Human IgG3 polyclonal antibody

The human commensal yeast Candida is the fourth most common cause of hospital-acquired bloodstream infections, with Candida albicans accounting for the majority of the > 400,000 life-threatening infections annually. Diagnosis of invasive candidiasis (IC), a disease encompassing candidemia (blood-borne yeast infection) and deep-seated organ infections, is a major challenge since clinical manifestations of the disease are indistinguishable from viral, bacterial and other fungal diseases, and diagnostic tests for biomarkers in the bloodstream such as PCR, ELISA, and pan-fungal beta-D-glucan lack either standardization, sensitivity, or specificity. Blood culture remains the gold standard for diagnosis, but test sensitivity is poor and turn-around time slow. Furthermore, cultures can only be obtained when the yeast resides in the bloodstream, with samples recovered from hematogenous infections often yielding negative results. Consequently, there is a pressing need for a diagnostic test that allows the identification of metastatic foci in deep-seated Candida infections, without the need for invasive biopsy. Here, we report the development of a highly specific mouse IgG3 monoclonal antibody (MC3) that binds to a putative beta-1,2-mannan epitope present in high molecular weight mannoproteins and phospholipomannans on the surface of yeast and hyphal morphotypes of C. albicans, and its use as a [Cu-64] NODAGA-labeled tracer for whole-body pre-clinical imaging of deep-seated C. albicans infections using antibody-guided positron emission tomography and magnetic resonance imaging (immunoPET/MRI). When used in a mouse intravenous (i.v.) challenge model that faithfully mimics disseminated C. albicans infections in humans, the [Cu-64] NODAGA-MC3 tracer accurately detects infections of the kidney, the principal site of blood-borne candidiasis in this model. Using a strain of the emerging human pathogen Candida auris that reacts with MC3 in vitro, but which is non-infective in i.v. challenged mice, we demonstrate the accuracy of the tracer in diagnosing invasive infections in vivo. This pre-clinical study demonstrates the principle of using antibody-guided molecular imaging for detection of deep organ infections in IC, without the need for invasive tissue biopsy.

Background: The identification of immunogens is crucial for human immunodeficiency virus type 1 (HIV-1) vaccine development. In our previous study, we demonstrated that HIV-1 envelope glycoprotein mutants based on the equine infectious anemia virus (EIAV) attenuated vaccine enhance immunogenicity, both for DNA immunization alone and as a combined DNA prime-vaccinia boost immunization. An RV144 clinical trial has demonstrated that an envelope protein boost may provide some degree of protection against HIV-1 infection. Methods: In order to explore the antibody immune responses to two HIV-1 envelope glycoprotein mutants based on the EIAV vaccine and wild-type envelope glycoprotein, mice and guinea pigs were immunized using a DNA prime-protein boost immunization strategy. Results: The result showed, compared with wild-type gp140, gp140 2M (which contained 2 sites amino acid mutations) and gp140 5M (which contained 5 sites amino acid mutations) increased env-specific IgG and IgG3 binding antibody titers. Gp140 2M resulted in a slight improvement in the neutralizing antibody response against sensitive HIV-1 isolates compared with gp140. Conclusion: These findings have implications for HIV-1 vaccine development based on the HIV-1 CN54 envelope glycoprotein.