Report of the Cent Gardes HIV Vaccine Conference: The B-cell Response to HIV. Part 1: Broadly Neutralizing Antibodies Fondation Mérieux Conference Center, Veyrier du Lac, France, 5-7 November 2012

CCR10 expression is required for the adjuvant activity of the mucosal chemokine CCL28 when delivered in the context of an HIV-1 Env DNA vaccine

An effective prophylactic vaccine targeting HIV must induce a robust humoral response and must direct the bulk of this response to the mucosa-the primary site of HIV transmission. The chemokine, CCL28, is secreted by epithelial cells at mucosal surfaces and recruits' cells expressing its receptor CCR10. CCR10 is predominantly expressed by IgA + ASCs. We hypothesized that co-immunization with plasmid DNA encoding consensus envelope antigens with plasmid-encoded CCL28 would enhance anti-HIV IgA responses at mucosal surfaces. Indeed, animals receiving pCCL28 and pEnvA/C had significantly increased HIV-specific IgA in fecal extract. Surprisingly, CCL28 co-immunization induced a significant increase in anti-HIV IgG in the serum in mice compared to those receiving pEnvA/C alone. These robust antibody responses were not associated with changes in the frequency of germinal center B cells but depended upon the expression of CCR10, as these responses we abolished in CCR10-deficient animals. Finally, immunization with CCL28 led to increased frequencies in HIV-specific CCR10 + and CCR10 + IgA + B cells in the small intestine and Peyer's patches of vaccinated animals as compared to those receiving pEnvA/C alone. These data indicate that CCL28 administration can enhance antigen-specific humoral responses systemically and at mucosal surfaces.

Broadly neutralizing antibodies and the promise of universal vaccines: where are we now?

Recent research has provided strong support for the utility of broadly neutralizing antibodies generated against viruses, which inherently possess a high degree of antigenic variability (such as influenza virus or HIV) as a feasible means to prevent infection. Many of these antibodies share the ability to bind to highly conserved regions within the stem of the virus ‘spike’ or surface glycoprotein, in such a way that they interfere with virus entry, including membrane fusion. As a result, broadly neutralizing antibodies could be supplied to patients as a form of passive immunotherapy, as well as play a role in the design of new ‘universal’ vaccines and antiviral agents. The following article describes the most recent innovations in this exciting field.

HIV-1 suppression and durable control by combining single broadly neutralizing antibodies and antiretroviral drugs in humanized mice

Effective control of HIV-1 infection in humans is achieved using combinations of antiretroviral therapy (ART) drugs. In humanized mice (hu-mice), control of viremia can be achieved using either ART or by immunotherapy using combinations of broadly neutralizing antibodies (bNAbs). Here we show that treatment of HIV-1-infected hu-mice with a combination of three highly potent bNAbs not only resulted in complete viremic control but also led to a reduction in cell-associated HIV-1 DNA. Moreover, lowering the initial viral load by coadministration of ART and immunotherapy enabled prolonged viremic control by a single bNAb after ART was withdrawn. Similarly, a single injection of adeno-associated virus directing expression of one bNAb produced durable viremic control after ART was terminated. We conclude that immunotherapy reduces plasma viral load and cell-associated HIV-1 DNA and that decreasing the initial viral load enables single bNAbs to control viremia in hu-mice.