A novel rabbit monoclonal antibody platform to dissect the diverse repertoire of antibody epitopes for HIV-1 Env immunogen design.

The majority of available monoclonal antibodies (MAbs) in the current HIV vaccine field are generated from HIV-1-infected people. In contrast, preclinical immunogenicity studies have mainly focused on polyclonal antibody responses in experimental animals. Although rabbits have been widely used for antibody studies, there has been no report of using rabbit MAbs to dissect the specificity of antibody responses for AIDS vaccine development. Here we report on the production of a panel of 12 MAbs from a New Zealand White (NZW) rabbit that was immunized with an HIV-1 JR-FL gp120 DNA prime and protein boost vaccination regimen. These rabbit MAbs recognized a diverse repertoire of envelope (Env) epitopes ranging from the highly immunogenic V3 region to several previously underappreciated epitopes in the C1, C4, and C5 regions. Nine MAbs showed cross-reactivity to gp120s of clades other than clade B. Increased somatic mutation and extended CDR3 were observed with Ig genes of several molecularly cloned rabbit MAbs. Phylogenic tree analysis showed that the heavy chains of MAbs recognizing the same region on gp120 tend to segregate into an independent subtree. At least three rabbit MAbs showed neutralizing activities with various degrees of breadth and potency. The establishment of this rabbit MAb platform will significantly enhance our ability to test optimal designs of Env immunogens to gain a better understanding of the structural specificity and evolution process of Env-specific antibody responses elicited by candidate AIDS vaccines.

Pilot study on the immunogenicity of paired Env immunogens from mother-to-child transmitted HIV-1 isolates.

Recent studies have reported that founder viruses play unique roles in establishing HIV-1 infection. Understanding the biological and immunological features of envelope glycoproteins (Env) from such viruses may facilitate the development of effective vaccines against HIV-1. In this report, we evaluated the immunogenicity of gp120 immunogens from two pairs of clade B and two pairs of clade C mother-to-child transmitted (MTCT) HIV-1 variants that had various levels of sensitivity to broadly neutralizing monoclonal antibodies. Individual gp120 DNA and protein vaccines were produced from each of the eight MTCT Env antigens included in the current study. Rabbits were immunized with these gp120 immunogens by the DNA prime-protein boost approach. High level Env-specific antibody responses were elicited by all MTCT gp120 immunogens. However, their abilities to elicit neutralizing antibody (NAb) responses differed and those from relatively neutralization-resistant variants tended to be more effective in eliciting broader NAb. Results of this pilot study indicated that not all MTCT Env proteins have the same potential to elicit NAb. Understanding the mechanism(s) behind such variation may provide useful information in formulating the next generation of HIV vaccines.

A single base pair mutation encoding a premature stop codon in the MIS type II receptor is responsible for canine persistent Müllerian duct syndrome.

Müllerian inhibiting substance (MIS), a secreted glycoprotein in the transforming growth factor-beta family of growth factors, mediates regression of the Müllerian ducts during embryonic sex differentiation in males. In persistent Müllerian duct syndrome (PMDS), rather than undergoing involution, the Müllerian ducts persist in males, giving rise to the uterus, fallopian tubes, and upper vagina. Genetic defects in MIS or its receptor (MISRII) have been identified in patients with PMDS. The phenotype in the canine model of PMDS derived from the miniature schnauzer breed is strikingly similar to that of human patients. In this model, PMDS is inherited as a sex-limited autosomal recessive trait. Previous studies indicated that a defect in the MIS receptor or its downstream signaling pathway was likely to be causative of the canine syndrome. In this study, the canine PMDS phenotype and clinical sequelae are described in detail. Affected and unaffected members of this pedigree are genotyped, identifying a single base pair substitution in MISRII that introduces a stop codon in exon 3. The homozygous mutation terminates translation at 80 amino acids, eliminating much of the extracellular domain and the entire transmembrane and intracellular signaling domains. Findings in this model could enable insights to be garnered from correlation of detailed clinical descriptions with molecular defects, which are not otherwise possible in the human syndrome.

Key factors in the regulation of fetal and postnatal Leydig cell development.

The primary function of testicular Leydig cells is the production of androgens to promote sexual differentiation in the fetus, secondary sexual maturation at puberty, and spermatogenesis in the adult. The fetal and postnatal (adult) populations of Leydig cells differ morphologically and have distinct profiles of gene expression. As postnatal Leydig cells differentiate, they transition through three discrete maturational stages characterized by decreasing proliferative rate and increasing testosterone biosynthetic capacity. In this review, we discuss the development of both fetal and postnatal Leydig cells and review the regulation of this process by some of the key hormones and growth factors.