Daniel C. Freed

Bio: Daniel C. Freed is an academic researcher from Merck & Co.. The author has contributed to research in topics: Antibody & Epitope. The author has an hindex of 35, co-authored 69 publications receiving 5759 citations. Previous affiliations of Daniel C. Freed include United States Military Academy.

Replication-incompetent adenoviral vaccine vector elicits effective anti-immunodeficiency-virus immunity.

Abstract: Recent studies of human immunodeficiency virus type 1 (HIV-1) infection in humans and of simian immunodeficiency virus (SIV) in rhesus monkeys have shown that resolution of the acute viral infection and control of the subsequent persistent infection are mediated by the antiviral cellular immune response. We comparatively assessed several vaccine vector delivery systems-three formulations of a plasmid DNA vector, the modified vaccinia Ankara (MVA) virus, and a replication incompetent adenovirus type 5 (Ad5) vector-expressing the SIV gag protein for their ability to elicit such immune responses in monkeys. The vaccines were tested either as a single modality or in combined modality regimens. Here we show that the most effective responses were elicited by a replication-incompetent Ad5 vector, used either alone or as a booster inoculation after priming with a DNA vector. After challenge with a pathogenic HIV-SIV hybrid virus (SHIV), the animals immunized with Ad5 vector exhibited the most pronounced attenuation of the virus infection. The replication-defective adenovirus is a promising vaccine vector for development of an HIV-1 vaccine.

Pd-1 binding proteins

Abstract: The present invention features PD-1 binding proteins, a subset of which inhibits binding of PD-L1 to the PD-1 receptor. These binding proteins can be employed to modulate the immune system through the manipulation of the PD-1 signaling pathway, enhancing host immunity to treat infections and cancer.

Comparative immunogenicity in rhesus monkeys of DNA plasmid, recombinant vaccinia virus, and replication-defective adenovirus vectors expressing a human immunodeficiency virus type 1 gag gene

Abstract: Cellular immune responses, particularly those associated with CD3 CD8 cytotoxic T lymphocytes (CTL), play a primary role in controlling viral infection, including persistent infection with human immunodeficiency virus type 1 (HIV-1). Accordingly, recent HIV-1 vaccine research efforts have focused on establishing the optimal means of eliciting such antiviral CTL immune responses. We evaluated several DNA vaccine formulations, a modified vaccinia virus Ankara vector, and a replication-defective adenovirus serotype 5 (Ad5) vector, each expressing the same codon-optimized HIV-1 gag gene for immunogenicity in rhesus monkeys. The DNA vaccines were formulated with and without one of two chemical adjuvants (aluminum phosphate and CRL1005). The Ad5-gag vector was the most effective in eliciting anti-Gag CTL. The vaccine produced both CD4 and CD8 T-cell responses, with the latter consistently being the dominant component. To determine the effect of existing antiadenovirus immunity on Ad5-gag-induced immune responses, monkeys were exposed to adenovirus subtype 5 that did not encode antigen prior to immunization with Ad5-gag. The resulting anti-Gag T-cell responses were attenuated but not abolished. Regimens that involved priming with different DNA vaccine formulations followed by boosting with the adenovirus vector were also compared. Of the formulations tested, the DNA-CRL1005 vaccine primed T-cell responses most effectively and provided the best overall immune responses after boosting with Ad5-gag. These results are suggestive of an immunization strategy for humans that are centered on use of the adenovirus vector and in which existing adenovirus immunity may be overcome by combined immunization with adjuvanted DNA and adenovirus vector boosting.

Potent, protective anti-HIV immune responses generated by bimodal HIV envelope DNA plus protein vaccination.

Abstract: It is generally thought that an effective vaccine to prevent HIV-1 infection should elicit both strong neutralizing antibody and cytotoxic T lymphocyte responses. We recently demonstrated that potent, boostable, long-lived HIV-1 envelope (Env)-specific cytotoxic T lymphocyte responses can be elicited in rhesus monkeys using plasmid-encoded HIV-1 env DNA as the immunogen. In the present study, we show that the addition of HIV-1 Env protein to this regimen as a boosting immunogen generates a high titer neutralizing antibody response in this nonhuman primate species. Moreover, we demonstrate in a pilot study that immunization with HIV-1 env DNA (multiple doses) followed by a final immunization with HIV-1 env DNA plus HIV-1 Env protein (env gene from HXBc2 clone of HIV IIIB; Env protein from parental HIV IIIB) completely protects monkeys from infection after i.v. challenge with a chimeric virus expressing HIV-1 env (HXBc2) on a simian immmunodeficiency virusmac backbone (SHIV-HXBc2). The potent immunity and protection seen in these pilot experiments suggest that a DNA prime/DNA plus protein boost regimen warrants active investigation as a vaccine strategy to prevent HIV-1 infection.

Potent, protective anti-HIV immune responses generated by bimodal HIV envelope DNA plus protein vaccination (CTLyvirus neutralizationyvaccineySHIVyT lymphocyte)

Abstract: It is generally thought that an effective vac- cine to prevent HIV-1 infection should elicit both strong neutralizing antibody and cytotoxic T lymphocyte responses. We recently demonstrated that potent, boostable, long-lived HIV-1 envelope (Env)-specific cytotoxic T lymphocyte re- sponses can be elicited in rhesus monkeys using plasmid- encoded HIV-1 env DNA as the immunogen. In the present study, we show that the addition of HIV-1 Env protein to this regimen as a boosting immunogen generates a high titer neutralizing antibody response in this nonhuman primate species. Moreover, we demonstrate in a pilot study that immunization with HIV-1 env DNA (multiple doses) followed by a final immunization with HIV-1 env DNA plus HIV-1 Env protein (env gene from HXBc2 clone of HIV IIIB; Env protein from parental HIV IIIB) completely protects monkeys from infection after i.v. challenge with a chimeric virus expressing HIV-1 env (HXBc2) on a simian immmunodeficiency virusmac backbone (SHIV-HXBc2). The potent immunity and protec- tion seen in these pilot experiments suggest that a DNA primeyDNA plus protein boost regimen warrants active in- vestigation as a vaccine strategy to prevent HIV-1 infection. Although the correlates for immune protection against HIV infection are currently unknown, it is probable that an effective HIV vaccine should elicit both strong neutralizing antibody and cytotoxic T lymphocyte (CTL) responses. Antibody re- sponses have provided protection from HIV infection in chimpanzee challenge models (1). Potential protective roles for CTL also have been recognized recently. It has become increasingly clear that CTL may play a key role in clearing viremia during primary HIV-1 infection in humans before the development of virus-neutralizing antibodies (2, 3) and in maintaining disease-free infection (4, 5). Furthermore, it has been suggested that anti-HIV CTL responses, detected in some HIV-exposed but uninfected individuals in the absence of HIV-specific antibodies, may have prevented establishment of infection (6, 7). Although a number of live vector, recombinant protein, and peptide vaccination strategies have been shown to elicit HIV- specific antibodies and CTL in nonhuman primate models and humans, it would be desirable if these responses were more potent and durable. The demonstration of the utility of plasmid DNA immunization for the induction of virus-specific CTL and neutralizing antibodies in a variety of animal disease models (8-11) suggests that this vaccine modality may prove useful for an AIDS vaccine. In fact, DNA vaccination has been shown to elicit HIV-specific CTL and antibody responses in rhesus monkeys (12-14). We recently demonstrated that im- munization regimens with HIV-1 env DNA elicit potent, long-lived envelope (Env)-specific CTL responses in rhesus monkeys (ref. 15 and unpublished work). These experiments demonstrated that (i) antigen-specific CTL responses were elicited in all monkeys after one or two vaccinations; (ii )a n additional immunization after several months of ''rest'' sub- stantially boosted CTL responses; and, (iii) these responses persisted at least 36 weeks. Although these HIV env DNA vaccines also elicited antigen-specific antibodies in monkeys, only low titers of virus-neutralizing antibodies generally were obtained (13). The full potential for the induction of HIV-specific immune responses using DNA immunization combined with other vaccine modalities has not been determined. In the present studies, we have immunized rhesus monkeys with HIV env DNA vaccines in combination with recombinant HIV-1 en- velope glycoprotein, characterized the resulting immune re- sponses, and assessed their protective efficacy against a SHIV- HXBc2 challenge.

Vaccination with ALVAC and AIDSVAX to Prevent HIV-1 Infection in Thailand

Abstract: In the intention-to-treat analysis involving 16,402 subjects, there was a trend toward the prevention of HIV-1 infection among the vaccine recipients, with a vaccine efficacy of 26.4% (95% confidence interval [CI], −4.0 to 47.9; P = 0.08). In the perprotocol analysis involving 12,542 subjects, the vaccine efficacy was 26.2% (95% CI, −13.3 to 51.9; P = 0.16). In the modified intention-to-treat analysis involving 16,395 subjects (with the exclusion of 7 subjects who were found to have had HIV-1 infection at baseline), the vaccine efficacy was 31.2% (95% CI, 1.1 to 52.1; P = 0.04). Vaccination did not affect the degree of viremia or the CD4+ T-cell count in subjects in whom HIV-1 infection was subsequently diagnosed. Conclusions This ALVAC-HIV and AIDSVAX B/E vaccine regimen may reduce the risk of HIV infection in a community-based population with largely heterosexual risk. Vaccination did not affect the viral load or CD4+ count in subjects with HIV infection. Although the results show only a modest benefit, they offer insight for future research. (ClinicalTrials.gov number, NCT00223080.)

T-cell quality in memory and protection: implications for vaccine design

Abstract: T cells mediate effector functions through a variety of mechanisms. Recently, multiparameter flow cytometry has allowed a simultaneous assessment of the phenotype and multiple effector functions of single T cells; the delineation of T cells into distinct functional populations defines the quality of the response. New evidence suggests that the quality of T-cell responses is crucial for determining the disease outcome to various infections. This Review highlights the importance of using multiparameter flow cytometry to better understand the functional capacity of effector and memory T-cell responses, thereby enabling the development of preventative and therapeutic vaccine strategies for infections.

Multifunctional TH1 cells define a correlate of vaccine-mediated protection against Leishmania major.

Abstract: CD4+ T cells have a crucial role in mediating protection against a variety of pathogens through production of specific cytokines. However, substantial heterogeneity in CD4+ T-cell cytokine responses has limited the ability to define an immune correlate of protection after vaccination. Here, using multiparameter flow cytometry to assess the immune responses after immunization, we show that the degree of protection against Leishmania major infection in mice is predicted by the frequency of CD4+ T cells simultaneously producing interferon-gamma, interleukin-2 and tumor necrosis factor. Notably, multifunctional effector cells generated by all vaccines tested are unique in their capacity to produce high amounts of interferon-gamma. These data show that the quality of a CD4+ T-cell cytokine response can be a crucial determinant in whether a vaccine is protective, and may provide a new and useful prospective immune correlate of protection for vaccines based on T-helper type 1 (TH1) cells.