Anna R. Thorner

Hexon-chimaeric adenovirus serotype 5 vectors circumvent pre-existing anti-vector immunity.

A common viral immune evasion strategy involves mutating viral surface proteins in order to evade host neutralizing antibodies. Such immune evasion tactics have not previously been intentionally applied to the development of novel viral gene delivery vectors that overcome the critical problem of anti-vector immunity. Recombinant, replication-incompetent adenovirus serotype 5 (rAd5) vector-based vaccines for human immunodeficiency virus type 1 and other pathogens have proved highly immunogenic in preclinical studies but will probably be limited by the high prevalence of pre-existing anti-Ad5 immunity in human populations, particularly in the developing world. Here we show that rAd5 vectors can be engineered to circumvent anti-Ad5 immunity. We constructed novel chimaeric rAd5 vectors in which the seven short hypervariable regions (HVRs) on the surface of the Ad5 hexon protein were replaced with the corresponding HVRs from the rare adenovirus serotype Ad48. These HVR-chimaeric rAd5 vectors were produced at high titres and were stable through serial passages in vitro. HVR-chimaeric rAd5 vectors expressing simian immunodeficiency virus Gag proved comparably immunogenic to parental rAd5 vectors in naive mice and rhesus monkeys. In the presence of high levels of pre-existing anti-Ad5 immunity, the immunogenicity of HVR-chimaeric rAd5 vectors was not detectably suppressed, whereas the immunogenicity of parental rAd5 vectors was abrogated. These data demonstrate that functionally relevant Ad5-specific neutralizing antibodies are focused on epitopes located within the hexon HVRs. Moreover, these studies show that recombinant viral vectors can be engineered to circumvent pre-existing anti-vector immunity by removing key neutralizing epitopes on the surface of viral capsid proteins. Such chimaeric viral vectors may have important practical implications for vaccination and gene therapy.

Comparative Seroprevalence and Immunogenicity of Six Rare Serotype Recombinant Adenovirus Vaccine Vectors from Subgroups B and D

ABSTRACT Recombinant adenovirus serotype 5 (rAd5) vector-based vaccines are currently being developed for both human immunodeficiency virus type 1 and other pathogens. The potential limitations associated with rAd5 vectors, however, have led to the construction of novel rAd vectors derived from rare Ad serotypes. Several rare serotype rAd vectors have already been described, but a detailed comparison of multiple rAd vectors from subgroups B and D has not previously been reported. Such a comparison is critical for selecting optimal rAd vectors for advancement into clinical trials. Here we describe the construction of three novel rAd vector systems from Ad26, Ad48, and Ad50. We report comparative seroprevalence and immunogenicity studies involving rAd11, rAd35, and rAd50 vectors from subgroup B; rAd26, rAd48, and rAd49 vectors from subgroup D; and rAd5 vectors from subgroup C. All six rAd vectors from subgroups B and D exhibited low seroprevalence in a cohort of 200 individuals from sub-Saharan Africa, and they elicited Gag-specific cellular immune responses in mice both with and without preexisting anti-Ad5 immunity. The rAd vectors from subgroup D were also evaluated using rhesus monkeys and were shown to be immunogenic after a single injection. The rAd26 vectors proved the most immunogenic among the rare serotype rAd vectors studied, although all rare serotype rAd vectors were still less potent than rAd5 vectors in the absence of anti-Ad5 immunity. These studies substantially expand the portfolio of rare serotype rAd vectors that may prove useful as vaccine vectors for the developing world.

Age Dependence of Adenovirus-Specific Neutralizing Antibody Titers in Individuals from Sub-Saharan Africa

ABSTRACT We assessed neutralizing antibody titers to adenovirus serotype 5 (Ad5) and six rare adenovirus serotypes, serotypes 11, 35, 50, 26, 48, and 49, in pediatric populations in sub-Saharan Africa. We observed a clear age dependence of Ad5-specific neutralizing antibody titers. These data will help to guide the development of Ad vector-based vaccines for human immunodeficiency virus type 1 and other pathogens.

Rocky Mountain Spotted Fever

Rocky Mountain spotted fever, the most prevalent rickettsial disease in the United States, is one of the most severe of all infectious diseases. It remains an important infectious disease because of its prevalence, the difficulty of clinical diagnosis, potentially fatal outcome, and lack of a widely available sensitive and specific diagnostic test during the acute stage of the illness.

Immunogenicity of Heterologous Recombinant Adenovirus Prime-Boost Vaccine Regimens Is Enhanced by Circumventing Vector Cross-Reactivity

ABSTRACT The high prevalence of preexisting immunity to adenovirus serotype 5 (Ad5) in human populations has led to the development of recombinant adenovirus (rAd) vectors derived from rare Ad serotypes as vaccine candidates for human immunodeficiency virus type 1 and other pathogens. Vaccine vectors have been constructed from Ad subgroup B, including rAd11 and rAd35, as well as from Ad subgroup D, including rAd49. However, the optimal combination of vectors for heterologous rAd prime-boost vaccine regimens and the extent of cross-reactive vector-specific neutralizing antibodies (NAbs) remain poorly defined. We have shown previously that the closely related vectors rAd11 and rAd35 elicited low levels of cross-reactive NAbs. Here we show that these cross-reactive NAbs correlated with substantial sequence homology in the hexon hypervariable regions (HVRs) and suppressed the immunogenicity of heterologous rAd prime-boost regimens. In contrast, vectors with lower hexon HVR homology, such as rAd35 and rAd49, did not elicit detectable cross-reactive vector-specific NAbs. Consistent with these findings, rAd35-rAd49 vaccine regimens proved more immunogenic than both rAd35-rAd5 and rAd35-rAd11 regimens in mice with anti-Ad5 immunity. These data suggest that optimal heterologous rAd prime-boost regimens should include two vectors that are both rare in human populations to circumvent preexisting antivector immunity as well as sufficiently immunologically distinct to avoid cross-reactive antivector immunity.

Disseminated Geotrichum candidum infection in a patient with relapsed acute myelogenous leukemia following allogeneic stem cell transplantation and review of the literature

Abstract: We describe a woman with relapsed acute myelogenous leukemia after allogeneic stem cell transplantation who developed disseminated Geotrichum candidum infection during chemotherapy‐induced neutropenia. The isolate was susceptible to voriconazole, amphotericin B, and micafungin in vitro. We review the literature regarding invasive infections with G. candidum, which predominantly affect immunocompromised hosts, and discuss potential therapies for this rare pathogen.

Early versus delayed antiretroviral therapy in patients with HIV infection : a review of the current guidelines from an immunological perspective.

The development and implementation of highly active antiretroviral therapy (HAART) for the treatment of the human immunodeficiency virus has revolutionised the care of patients with this disease. Despite the positive impact that antiretroviral therapy has had on the lives of individuals with HIV infection, the adverse effects, potential long-term toxicities, complexity of regimens, development of drug resistance and cost have made decisions about when to initiate HAART difficult. The benefits and risks of antiretroviral therapy vary considerably among patients at different stages of disease, mainly as a result of the irreversible destruction of the immune system that occurs as HIV infection progresses. In acute HIV infection, the primary aim of treatment is preservation and reconstitution of HIV-specific immune function. In symptomatic or late-stage disease, the goal is control of viral replication with resulting improvement in non-HIV-specific immunity, which leads to decreased morbidity and increased survival. The most controversial decision involves when to start therapy in persons with asymptomatic chronic HIV, where the benefits are less well established and may be outweighed by the drawbacks, depending on the individual patient. In all patients, the advantages and disadvantages must be considered carefully, and the readiness and ability of the individual to adhere to a complex multidrug regimen needs to be assessed before the initiation of therapy.The development and implementation of highly active antiretroviral therapy (HAART) for the treatment of the human immunodeficiency virus has revolutionised the care of patients with this disease. Despite the positive impact that antiretroviral therapy has had on the lives of individuals with HIV infection, the adverse effects, potential long-term toxicities, complexity of regimens, development of drug resistance and cost have made decisions about when to initiate HAART difficult. The benefits and risks of antiretroviral therapy vary considerably among patients at different stages of disease, mainly as a result of the irreversible destruction of the immune system that occurs as HIV infection progresses.In acute HIV infection, the primary aim of treatment is preservation and reconstitution of HIV-specific immune function. In symptomatic or late-stage disease, the goal is control of viral replication with resulting improvement in non-HIV-specific immunity, which leads to decreased morbidity and increased survival. The most controversial decision involves when to start therapy in persons with asymptomatic chronic HIV, where the benefits are less well established and may be outweighed by the drawbacks, depending on the individual patient.In all patients, the advantages and disadvantages must be considered carefully, and the readiness and ability of the individual to adhere to a complex multidrug regimen needs to be assessed before the initiation of therapy.

Correlation Between UpToDate Searches and Reported Cases of Middle East Respiratory Syndrome During Outbreaks in Saudi Arabia

UpToDate search activity is useful for detecting and monitoring outbreaks of Middle East respiratory syndrome in Saudi Arabia.

Three Cases of Neurologic Syndrome Caused by Donor-Derived Microsporidiosis

Encephalitozoon cuniculi was transmitted from an infected donor to 3 solid organ recipients, 1 of whom died.

596. A Novel Replication Incompetent Human Subgroup D Adenoviral Vector Based on Type 49: Manufacture on PER.C6®, Cell Tropism and Immunogenicity

Recombinant adenoviral vectors based on type 5 (rAd5) show great promise as vaccine carrier. However, neutralizing activity against Ad5 is prevalent and high titered among human populations and significantly dampens Ad5-based vaccine modalities. The generation of alternative adenoviral vectors with low sero-prevalence thus receives much research interest. We have previously published that several members of human subgroup D adenoviruses display low sero-prevalence in Europe and here we demonstrate that one such member, i.e. Ad49, is immunologically distinct from Ad5. We next set out to construct a plasmid system that allows formation of replication incompetent adenovirus serotype 49 vaccine vectors (rAd49) and demonstrate that rAd49 can be successfully propagated to high titers on existing E1-complementing cell lines such as PER.C6|[reg]|. Using a rAd49 vector carrying the luciferase marker gene sero-prevalence studies were performed demonstrating that rAd49 has low sero-prevalence and neutralizing antibody titers worldwide. Also, we have initiated rAd49 vector receptor usage suggesting that rAd49 utilizes hCD46 as a cellular receptor. Next, we assessed the immunogenicity of the rAd49 vector and show that a rAd49.SIVGag vaccine induces strong anti-SIVGag CD8+T-lymphocytes in naive mice albeit approximately 1.5-fold less compared to a rAd5.SIVGag vaccine. However, in mice with high anti-Ad5 immunity the anti- SIVGag response was not statistically significant suppressed using the rAd49.SIVGag vaccine whereas the rAd5.SIVGag vaccine was severely blunted. Finally, rAd35.SIVGag prime-rAd49.SIVGag boost experiments in mice carrying high-level anti-Ad5 neutralizing activity demonstrated that the rAd49 based vaccine is not hampered by neither rAd5 nor rAd35 neutralizing activity. These data demonstrate the potential of a replication deficient human D-group adenoviral vector as stand-alone vaccine carrier or in prime-boost settings with other rare human adenoviral vectors.