In this manuscript, a new approach in surface plasmon resonance microscopy is presented. The method provides optical real-time detection of single nanoparticles on surfaces. The potential of the method is demonstrated recording spherical dielectric particles as small as 40 nm in diameter and single HIV virus-like particles having diameters of ∼100 nm both immobilized on functionalized surfaces. The surface plasmon resonance signal in the binding spots was found to be almost linearly proportional to the size of the particles and, therefore, surpasses the intensity of Mie scattering on spherical particle (dependence ∼ r −6 ) by orders of magnitude for small objects. The physical reason leading to this strong effect is discussed.

BackgroundImmunization of rhesus macaques against Gag of SIV resulted in a more rapid appearance of Env antibodies after infection with SIV or SHIV challenge viruses although the vaccines lacked an Env component. We therefore explored whether T helper cells specific for internal HIV proteins could provide intrastructural help for Env-specific B cells and thus increase the Env antibody response.ResultsMice were immunized by adenoviral vector or DNA vaccines against GagPol and then boosted with virus-like particles (VLP) containing GagPol and Env. Env-specific antibody levels after the VLP booster immunizations were significantly higher in GagPol-immunized mice than in mock-vaccinated controls. Adoptive transfer of CD4+ T cells from GagPol-immunized mice also enhanced the Env antibody response to VLP immunization in the recipient mice. Depending on the presence of VLPs, co-cultivation of CD4+ T cells from GagPol-primed mice with BCR transgenic B cells specific for a protein presented on the surface of the VLPs also resulted in the activation of the B and T cells.ConclusionsOur study indicates that GagPol-specific T helper cells may provide intrastructural help for Env antibody responses. This cross-talk between immune responses directed against different components of the retroviral particle may be relevant for the immunopathogenesis of retroviral infections and allow to improve virus like particle vaccine approaches against HIV.

Exosomes have been proposed as candidates for therapeutic immunization. The present study demonstrates that incorporation of the G protein of vesicular stomatitis virus (VSV-G) into exosome-like vesicles (ELVs) enhances their uptake and induces the maturation of dendritic cells. Targeting of VSV-G and ovalbumin as a model antigen to the same ELVs increased the cross-presentation of ovalbumin via an endosomal acidification mechanism. Immunization of mice with VSV-G and ovalbumin containing ELVs led to an increased IgG2a antibody response, expansion of antigen-specific CD8 T cells, strong in vivo CTL responses, and protection from challenge with ovalbumin expressing tumor cells. Thus, incorporation of VSV-G and targeting of antigens to ELVs are attractive strategies to improve exosomal vaccines.

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Alcohol consumption is a consistent protective factor for the development of autoimmune diseases such as rheumatoid arthritis (RA). The underlying mechanism for this toleranceinducing effect of alcohol, however, is unknown. Here we show that alcohol and its metabolite acetate alter the functional state of T follicular helper (T FH ) cells in vitro and in vivo, thereby exerting immune regulatory and tolerance-inducing properties. Alcohol-exposed mice have reduced Bcl6 and PD-1 expression as well as IL-21 production by T FH cells, preventing proper spatial organization of T FH cells to form T FH :B cell conjugates in germinal centers. This effect is associated with impaired autoantibody formation, and mitigates experimental autoimmune arthritis. By contrast, T cell independent immune responses and passive models of arthritis are not affected by alcohol exposure. These data clarify the immune regulatory and toleranceinducing effect of alcohol consumption.

The importance of Fc-dependent effector functions of Abs induced by vaccination is increasingly recognized. However, vaccination of mice against HIV envelope (Env) induced a skewed Th cell response leading to Env-specific Abs with reduced effector function. To overcome this bias, GagPol-specific Th cells were harnessed to provide intrastructural help for Env-specific B cells after immunization with virus-like particles containing GagPol and Env. This led to a balanced Env-specific humoral immune response with a more inflammatory Fc glycan profile. The increased quality in the Ab response against Env was confirmed by FcγR activation assays. Because the Env-specific Th cell response was also biased in human vaccinees, intrastructural help is an attractive novel approach to increase the efficacy of prophylactic HIV Env-based vaccines and may also be applicable to other particulate vaccines.

Adenoviral vectors (AdV) have received considerable attention for vaccine development because of their high immunogenicity and efficacy. In previous studies, it was shown that DNA immunization of mice with codonoptimized expression plasmids encoding the fusion protein of respiratory syncytial virus (RSV F) resulted in enhanced protection against RSV challenge compared to immunization with plasmids carrying the wild-type cDNA sequence of RSV F. In this study, we constructed AdV carrying the codon-optimized full-length RSV F gene (AdV-F) or the soluble form of the RSV F gene (AdV-Fsol). BALB/c mice were immunized twice with AdV-F or AdV-Fsol and challenged with RSV intranasally. Substantial levels of antibody to RSV F were induced by both AdV vaccines, with peak neutralizing-antibody titers of 1:900. Consistently, the viral loads in lung homogenates and bronchoalveolar lavage fluids were significantly reduced by a factor of more than 60,000. The protection against viral challenge could be measured even 8 months after the booster immunization. AdV-F and AdV-Fsol induced similar levels of immunogenicity and protective efficacy. Therefore, these results encourage further development of AdV vaccines against RSV infection in humans.Human respiratory syncytial virus (RSV) is a highly infectious member of the paramyxovirus family causing upper and lower respiratory tract infections in humans. Serious acute RSV infections, including fatal cases of bronchiolitis and pneumonia, occur particularly in premature infants, immunocompromised adults, and patients with pre-existing chronic lung diseases or underlying heart defects (11,12,14,39,46,56). In young children, RSV is the most common respiratory tract pathogen, accounting for approximately 50% of hospitalizations due to lower respiratory tract infections (21). In population-based surveillance studies for hospitalization in Europe, RSV was identified in 42 to 45% of enrolled children younger than 2 years with lower respiratory tract infections, and the rate of hospitalization due to RSV-induced respiratory illnesses was estimated at 3 to 6% among industrialized nations (45). Children with severe RSV infections suffer from oxygen deficiency with cyanosis and require intensive medical care. Furthermore, RSV infection in childhood is suspected to be a risk factor for development of asthma (36,41,43,59). The urgent need for an RSV vaccine is further demonstrated by a study showing that levels of disease burden, mortality, and morbidity caused by RSV infections in the elderly are comparable to those induced by nonpandemic influenza A infections (11). However, the immunization of children with a formalininactivated (FI) RSV vaccine in the 1960s resulted in a more severe clinical illness, with two fatal cases, than in nonvaccinated infants following RSV infection, pointing out the difficulties in developing a safe and efficacious RSV vaccine (7,29). It was shown previously that the enhanced disease severity and the development of pulmonary eosinophilia are mainly attributable to a...

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