Search

The results of our study presented here establishes that gonadotropin-releasing hormone (GnRH) acts directly on the corpus luteum, leading to suppressed production and release of progesterone and thus disrupting pregnancy. A GnRH-agonist (GnRH-Ag) treatment suppressed the luteal and serum progesterone levels. This suppression is neither mediated by a fall in ovarian testosterone production nor its conversion to estradiol. Although the treatment suppressed the nuclear estradiol-receptor content and binding sites for LH in the corpus luteum, it had no effect on the luteal binding sites for GnRH and prolactin within 24 h. GnRH-Ag augmented the plasma levels of luteinizing hormone, decreased the magnitude of nocturnal surges of prolactin, and had no effect on luteal cyclic adenosine 5′-monotriphosphate levels. Yet, the treatment had no effect on the luteal content of free cholesterol. We have also demonstrated, for the first time, the presence of steroidogenic acute regulatory protein and peripheral benzodiazepine receptor in the rat corpus luteum, and the suppression of these proteins by GnRH-Ag leads to reduced steroidogenesis by the corpus luteum. Concomitantly, P450 side-chain cleavage enzyme, its activity, and its mRNA content and 3β-hydroxy-steroid dehydrogenase content in the corpus luteum decreased. The treatment suppressed the plasma levels of pregnenolone and 20α-dihydroprogesterone. These data suggest that the suppression of luteal steroidogenesis by GnRH-Ag may be due to its inhibitory effect on the cholesterol transport and/or on the enzymes involved in the steroidogenic pathway. Furthermore, based on other observations made in our laboratory, we propose a hypothesis that an endogenous GnRH is present in the corpus luteum/ovary during pregnancy in the rat and that this GnRH may play a physiological role in the regulation, maintenance, and/or termination of pregnancy.

BALB/c mice immunized with nanoparticle vaccines comprising RSV G protein CX3C polypeptides in absence of adjuvant had a neutralizing antibody response associated with reduced lung titers following RSV challenge. These mice also had an increased level of RSV G protein-specific IL-4 and IFNγ secreting cells in the lung, and an increased level of RSV M2-specific IL-4 and IFNγ CD8 T cells. There was a significant increase in M2-specific CD8 T cells that trafficked to the lung following RSV challenge despite the mice being vaccinated with a G protein epitope. Pulmonary cell analysis revealed no significant increase in neutrophils (Ly6Ghi Ly6Cint CD125loSiglecF-) or eosinophils (Ly6Gint Ly6Chi CD125hi SiglecF+) in vaccinated mice before or after RSV challenge. The results show that RSV G protein nanoparticle vaccination is safe and effective, induces a neutralizing protective antibody response, increased RSV G protein- and M2-specific T cell responses, and is not associated with pulmonary disease pathogenesis.

Nanoparticle vaccines synthesized via layer-by-layer (LbL) fabrication were loaded with designed peptides representing epitopes of the attachment (G) and matrix (M2) proteins of respiratory syncytial virus. The CX3C chemokine mimic epitope of RSV-G has been proposed to contribute to inflammatory responses post-challenge while CD8+ T-cell responses against RSV M2 have been shown to limit the severity of infection and inflammatory pathology. Both monovalent designs (G or M2) and multivalent designs (G+M2) were tested. Mice immunized with RSV-G nanoparticles produced antibody responses that recognized the CX3C epitope only in its folded conformation and not in a linearized state. The same sera also bound native RSV-G protein, inhibited binding of RSV-G protein to the CX3CR1 chemokine receptor, and inhibited migration of human leukocytes toward RSV-G protein. Mice immunized with RSV M2 nanoparticles generated CD8+ T-cell responses and in vitro CTL activity against M2-labeled target cells. The multivalent vaccines containing both G and M2 elicited higher antibody responses to RSV-G and, surprisingly, more potent cellular responses against RSV-M2. These novel nanoparticle vaccines are currently being tested for the induction of neutralizing antibody responses and protection from viral challenge. If successful, the LbL nanoparticle fabrication strategy will provide an innovative approach to formulating safe and effective subunit vaccines for respiratory pathogens including RSV.