Cell-mediated immunologic memory in prevention and treatment of HIV disease

Intradermal and oral immunization with recombinant Mycobacterium bovis BCG expressing the simian immunodeficiency virus Gag protein induces long-lasting, antigen-specific immune responses in guinea pigs

To develop a new recombinant BCG (rBCG) vaccine, we constructed rBCG that expresses the full-length Gag protein of simian immunodeficiency virus (rBCG-SIVGag) at a level of 0.5 ng/mg after 3 weeks of bacterial cell culture. Intradermal (i.d.) inoculation of guinea pigs with 0.1 mg of rBCG-SIVGag resulted in the induction of delayed-type hypersensitivity (DTH) responses to both purified protein derivative (PPD) of tuberculin and SIV Gag p27 protein; responses that were maintained for the duration of the 50-week study. In contrast, guinea pigs orally vaccinated with 160 mg of the same antigen exhibited a long-lasting DTH response to the SIV Gag p27 protein, but mounted no response to PPD. Proliferative responses to SIV Gag p27 and PPD antigens were detected in both i.d. and orally immunized animals; however, the levels of PPD-specific responses were significantly higher in guinea pigs immunized by the i.d. than the oral route. A significant increase in the level of PPD- and SIV Gag p27-specific IFNgamma mRNA expression was also detected in both immunization groups receiving rBCG-SIVGag. In addition, both i.d. and oral immunization with rBCG-SIVGag induced PPD- and SIV Gag p27-specific serum IgG responses. Insertion of the SIV gag gene into BCG did not appear to change the ability of rBCG-immunized animals to elicit PPD-specific immune responses. These results indicate that rBCG-SIVGag has the ability to effectively induce long-lasting, cell-mediated and humoral immunity against both viral and bacterial antigens in guinea pigs, suggesting that rBCG-Gag has the potential to elicit immunities specific not only for tuberculosis but also for HIV at human doses.

Th1/Th2 cells in inflammatory disease states: therapeutic implications

Inflammation is initiated as a protective response by the host, but can often result in systemic pathology. Among cells of the immune system, T lymphocytes play a major role in the inflammatory response. T cell inflammation is characterised histologically by an infiltration of mononuclear cells. Key regulators of this response are a subset of T lymphocytes called T helper (Th) cells. These cells secrete soluble mediators called cytokines, which orchestrate the immune response. The appropriate regulation of Th cell immunity is critical in the control and prevention of diverse disease states. This review will focus on the role of Th cells in the inflammatory process involved in allergic disease, diabetes, infectious disease, rheumatoid arthritis, heart disease, multiple sclerosis and cancer. In the area of autoimmunity, in particular, a basic understanding of Th cells and cytokines has contributed to the development of clinically efficacious biological agents. This review also examines current and novel treatment strategies under investigation at present that regulate Th cell immunity, which may result in better treatments for immune-mediated diseases.

Combined intrarectal/intradermal inoculation of recombinant Mycobacterium bovis bacillus Calmette-Guérin (BCG) induces enhanced immune responses against the inserted HIV-1 V3 antigen

The development of a successful recombinant Mycobacterium bovis bacillus Calmette-Guérin (rBCG) vector-based vaccine for human immunodeficiency virus type 1 (HIV-1) requires the induction of high levels of HIV-1-specific immunity while at the same time maintaining immunity to tuberculosis. To examine a combined vaccination strategy for enhancement of immune responses specific for HIV-1, guinea pigs were inoculated with either a single or combination intradermal (i.d.), intrarectal (i.r.) and intranasal (i.n.) administration of rBCG-pSOV3J1 which secretes a chimeric protein of HIV-1 V3J1 peptide and alpha-antigen. Significant level of delayed-type hypersensitivity to both V3J1 peptide and tuberculin was induced in guinea pigs inoculated with human doses of rBCG-pSOV3J1 by a combination of intrarectal and intradermal routes. Guinea pigs inoculated by combined routes also had significantly higher titers of HIV-1-specific serum IgG and IgA compared with those animals immunized only intrarectally, which led to the enhanced neutralization activity against HIV-1(MN). In addition, the induction of high levels of IFNgamma and interleukin-2 (IL-2) mRNA in PBMC, splenocytes, and intraepithelial lymphocytes from the immunized animals was detected until at least 110 weeks post-inoculation. These results suggest that enhanced immune responses specific for HIV-1 are efficiently induced by combined intrarectal and intradermal immunization with rBCG-HIV, and antigen-specific Th1-type memory cells are maintained for more than 2 years in the immunized animals. Thus, inoculation with rBCG-HIV by combined routes represents an effective vaccination strategy to elicit high levels of HIV-1-specific immune responses.

Whole-killed gp120-depleted HIV-1 antigen in a murine model for prophylactic vaccination

In this study, the effects were examined of dose and adjuvant of whole-killed gp120-depleted HIV-1 antigen on antibody and cytokine responses in a murine model. Immunization with increasing doses of inactivated HIV-1 antigen in Incomplete Freund's Adjuvant (IFA) resulted in increased production of IL-4 and IgG1 antibody with decreased production of interferon gamma. Immunization with inactivated HIV-1 antigen in Detox PC adjuvant produced TH1 type predominant cytokine patterns along with IgG2a subclass antibody. Higher levels of interferon gamma were associated with immunization with inactivated HIV-1 antigen in Detox PC compared with inactivated HIV-1 in IFA or inactivated HIV-1 in saline. Inactivated HIV-1 antigen in Detox PC adjuvant produced a trend of lower levels of the beta-chemokine MIP-1 alpha compared with inactivated HIV-1 in IFA or saline. Dose and adjuvant play an important role in the type of immune response elicited to a whole-killed HIV vaccine. Low doses of inactivated HIV-1 antigen in Detox PC adjuvant are currently being studied in animal models in order to optimize cell-mediated immunity against HIV infection.

Combination therapies against HIV-1 infection: exploring the concept of combining antiretroviral drug treatments with HIV-1 immune-based therapies in asymptomatic individuals

The deleterious effect of HIV on the immune system begins at the time of infection. At seroconversion the virologic and immunologic factors that ultimately will dictate the rate of disease progression are believed to be already in place. The concept developed in this paper implies that, to impact significantly on the progression of disease, anti-HIV therapies should be initiated as early as possible in asymptomatic individuals. Published results have shown that combination drug therapies are potent in reducing HIV-1 RNA load in plasma in asymptomatic individuals, and that some HIV-1 immune-based therapies have a positive impact on immunological markers of disease progression, including HIV-1 cell-mediated immunity (CMI) and CD4 percent. The strategy discussed is to test a combination of antiretroviral therapy with HIV-1 immune-based therapy, such as the inactivated HIV-1 immunogen preparation, in asymptomatic individuals. The goal of this combination approach is to overcome the limitations of each therapy alone. Preliminary data suggest that antiretroviral therapy and the HIV-1 Immunogen can be combined with no noticeable interference and/or added toxicity in a broad range of HIV-1-infected individuals. Combining both therapies may enhance and expand the impact on key surrogate markers of disease progression, although they likely achieve this impact through different mechanisms. Thus, the primary question remains: Can these effects be synergistic?

Viral load, CD4 percentage, and delayed-type hypersensitivity in subjects receiving the HIV-1 immunogen and antiviral drug therapy

Two trials of subjects inoculated with the inactivated, gp120-depleted HIV-1 Immunogen are reported. In one study, in which 19 subjects received ZDV and 8 subjects received ddI, treatment with the HIV-1 Immunogen did not affect the pharmacokinetic parameters of the antiviral drugs. In another study, 65 subjects who were previously immunized with the HIV-1 Immunogen over a mean period of 4.0 years (range, 1.2-5.4 years) received inoculations at 0 and 6 months. At some point during this 48-week study, 72% of the subjects (47/65) were receiving antiviral drug therapy. The HIV-1 DNA load in CD4 cells and CD4 percentage were found to be stable over the 48-week period. Delayed-type hypersensitivity to HIV-1 antigens increased after two inoculations with the HIV-1 Immunogen. In these two trials, no serious treatment-related adverse events were documented in the subjects. The two studies presented herein are the first to suggest that an immune-based therapy such as the HIV-1 Immunogen can be combined safely with antiviral drugs, supporting further study to evaluate the clinical utility of this approach.

Initial studies on active immunization of HIV-infected subjects using a gp120-depleted HIV-1 Immunogen: long-term follow-up

In 1987, exploratory clinical studies were initiated to determine whether the development of AIDS in HIV-infected individuals might be delayed or prevented by immunization with an inactivated HIV preparation. Preclinical studies had shown the preparation to be safe and immunogenic. Twenty-three patients with biopsy-confirmed persistent generalized lymphadenopathy (CDC III) and two with asymptomatic HIV infection and CD4 lymphocyte counts between 135 and 769/mm3 were studied, of whom eight (32%) had additional HIV-related symptoms. Over a 3-year period, they received a median of eight open-label inoculations of 100 micrograms of inactivated gp 120-depleted HIV-1 Immunogen in incomplete Freund's adjuvant (IFA). Clinical, general laboratory, immunologic, and virologic parameters were followed for up to 6 years. No serious treatment-related adverse experiences were reported, nor was accelerated HIV disease progression seen. Twelve patients developed a delayed-type hypersensitivity response (HIV-DTH) to the immunogen and nine showed fourfold or greater increases in anti-p24 antibody titers. In the follow-up period, 10 of the 25 patients developed AIDS and one with Kaposi's sarcoma (KS) at baseline progressed. Of the 12 patients who became HIV-DTH-responsive, one developed an opportunistic infection (OI), occurring approximately 5 years from study onset, and subsequently died. One additional HIV-DTH responder developed KS. Of the 13 patients who remained HIV-DTH-nonresponsive, nine (69%) progressed to AIDS and seven of these have died. Differences were also observed in terms of HIV-DNA copy number, CD4 percentages, and anti-p24 antibody patterns between the HIV-DTH-responsive and -nonresponsive groups, suggesting a more favorable clinical course in the former. HIV-1 Immunogen in IFA appears to be safe and immunogenic. Further studies are indicated to determine clinical efficacy of the HIV Immunogen as well as the significance of the apparent correlation between HIV-DTH responsivity and a more favorable clinical course.

Inhibition of in vitro HIV infection by dialysable leucocyte extracts

Dialysable Leucocyte Extract (DLE) is a low molecular weight dialysable material of disrupted peripheral human leucocytes with widespread effects on the immune system. We described the in vitro anti-HIV activity of DLE as well as its three chromatographic fractions (Fa, Fb and Fc). To determine the levels of inhibition on HIV replication by DLE we infected MT-4 cell cultures, using the Bru viral isolate at 0.05, 0.1, 0.5 and 1 m.o.i. Previously, MT-4 cells cultures were treated with DLE or fractions at non-toxic concentrations. Reverse transcriptase (RT) activity and p24 antigen were evaluated in culture supernatants at seven days postinfection. No effect was observed when MT-4 cells were incubated with DLE for 3 h. Whereas inhibition of HIV production was observed when MT-4 cells were pre-treated for a longer period of time. DLE inhibited p24 production and RT activity more than 50% at 0.1 m.o.i. More than 80% of inhibition was observed for all doses of DLE tested at 0.05 m.o.i. Higher viral doses (m.o.i. 0.5 and 1) were used to assess the antiviral activity of DLE fractions. Fraction Fb inhibits viral production more than 80%. Otherwise, fractions Fa and Fc did not show inhibitory effect for any viral dose used. These results indicate that DLE is able to modulate cell susceptibility to viral infection in vitro.