Suppression of p24 antigen in sera from HIV-infected individuals with low-dose alpha-interferon and zidovudine: a pilot study

Genetic and phenotypic analyses of sequential vpu alleles from HIV-infected IFN-treated patients

Treatment of HIV-infected patients with IFN-α results in significant, but clinically insufficient, reductions of viremia. IFN induces the expression of several antiviral proteins including BST-2, which inhibits HIV by multiple mechanisms. The viral protein Vpu counteracts different effects of BST-2. We thus asked if Vpu proteins from IFN-treated patients displayed improved anti-BST-2 activities as compared to Vpu from baseline. Deep-sequencing analyses revealed that in five of seven patients treated by IFN-α for a concomitant HCV infection in the absence of antiretroviral drugs, the dominant Vpu sequences differed before and during treatment. In three patients, vpu alleles that emerged during treatment improved virus replication in the presence of IFN-α, and two of them conferred improved virus budding from cells expressing BST-2. Differences were observed for the ability to down-regulate CD4, while all Vpu variants potently down-modulated BST-2 from the cell surface. This report discloses relevant consequences of IFN-treatment on HIV properties.

Soluble mediators of inflammation in HIV and their implications for therapeutics and vaccine development

From early in the HIV epidemic it was appreciated that many inflammatory markers such as neopterin and TNF-α were elevated in patients with AIDS. With the advent of modern technology able to measure a broad array of cytokines, we now know that from the earliest points of infection HIV induces a cytokine storm. This review will focus on how cytokines are disturbed in HIV infection and will explore potential therapeutic uses of cytokines. These factors can be used directly as therapy during HIV infection, either to suppress viral replication or prevent deleterious immune effects of infection, such as CD4+ T cell depletion. Cytokines also show great promise as adjuvants in the development of HIV vaccines, which would be critical for the eventual control of the epidemic.

Cell-cell spread of human immunodeficiency virus type 1 overcomes tetherin/BST-2-mediated restriction in T cells

Direct cell-to-cell spread of human immunodeficiency virus type 1 (HIV-1) between T cells at the virological synapse (VS) is an efficient mechanism of viral dissemination. Tetherin (BST-2/CD317) is an interferon-induced, antiretroviral restriction factor that inhibits nascent cell-free particle release. The HIV-1 Vpu protein antagonizes tetherin activity; however, whether tetherin also restricts cell-cell spread is unclear. We performed quantitative cell-to-cell transfer analysis of wild-type (WT) or Vpu-defective HIV-1 in Jurkat and primary CD4(+) T cells, both of which express endogenous levels of tetherin. We found that Vpu-defective HIV-1 appeared to disseminate more efficiently by cell-to-cell contact between Jurkat cells under conditions where tetherin restricted cell-free virion release. In T cells infected with Vpu-defective HIV-1, tetherin was enriched at the VS, and VS formation was increased compared to the WT, correlating with an accumulation of virus envelope proteins on the cell surface. Increasing tetherin expression with type I interferon had only minor effects on cell-to-cell transmission. Furthermore, small interfering RNA (siRNA)-mediated depletion of tetherin decreased VS formation and cell-to-cell transmission of both Vpu-defective and WT HIV-1. Taken together, these data demonstrate that tetherin does not restrict VS-mediated T cell-to-T cell transfer of Vpu-defective HIV-1 and suggest that under some circumstances tetherin might promote cell-to-cell transfer, either by mediating the accumulation of virions on the cell surface or by regulating integrity of the VS. If so, inhibition of tetherin activity by Vpu may balance requirements for efficient cell-free virion production and cell-to-cell transfer of HIV-1 in the face of antiviral immune responses.

Adjuvant high-dose interferon-{alpha} for resected melanoma in a patient with HIV infection

Adjuvant interferon (IFN)-alpha remains the standard adjuvant therapy for intermediate and high-risk melanoma after definitive surgical resection. Data addressing the role and safety of adjuvant immunotherapy in HIV-infected patients with melanoma are lacking. We report on an HIV(+) patient who received IFN-alpha as adjuvant treatment for high-risk melanoma. To our knowledge, this is the first reported case of such an approach.

Virologic and immunologic activity of PegIntron in HIV disease

OBJECTIVE

The primary objectives of this study were to evaluate the safety, tolerability, and antiviral activity of pegylated interferon-alpha (PegIntron) in HIV-1 treatment-experienced patients failing their current antiretroviral regimen.

DESIGN

This was a phase II, multicenter, randomized, double-blind, placebo-controlled study.

METHODS

Patients were randomized to receive either weekly subcutaneous PegIntron 0.5, 1.0, 1.5, or 3 microg/kg or placebo added to their failing antiretroviral regimen for the first 4 weeks of study. Individuals who achieved more than 0.5 log10 reduction in HIV RNA at week 4 were allowed to continue study medication with optimization of their antiretroviral therapy for an additional 24 weeks.

RESULTS

In the 259 patients included in the intent-to-treat analysis, changes in plasma HIV RNA from baseline to week 4 were -0.25 (P > 0.5), -0.46 (P = 0.024), -0.39 (P = 0.008), -0.53 (P < 0.001), and -0.17 (P > 0.5) log10 copies/ml in the 0.5, 1.0, 1.5, and 3.0 microg/kg and placebo arms, respectively. No significant changes were seen in CD4 T-cell parameters in any of the treatment or control arms. Adverse events (most commonly fever, flu-like symptoms, other constitutional symptoms, and psychiatric symptoms) resulted in discontinuation of study medication in 13, 17, 16, 28, and 2% of patients in the 0.5, 1.0, 1.5, 3.0 microg/kg, and placebo group, respectively.

CONCLUSION

The demonstration of significant antiviral activity in a heavily pretreated patient population with acceptable toxicity and only weekly dosing makes PegIntron a potentially valuable therapy for patients with HIV infection that warrants further investigation in a broader population of patients.

Partial inhibition of human immunodeficiency virus replication by type I interferons: impact of cell-to-cell viral transfer

Type I interferons (IFN) inhibit several steps of the human immunodeficiency virus type 1 (HIV) replication cycle. Some HIV proteins, like Vif and Vpu, directly counteract IFN-induced restriction factors. Other mechanisms are expected to modulate the extent of IFN inhibition. Here, we studied the impact of IFN on various aspects of HIV replication in primary T lymphocytes. We confirm the potent effect of IFN on Gag p24 production in supernatants. Interestingly, IFN had a more limited effect on HIV spread, measured as the appearance of Gag-expressing cells. Primary isolates displayed similar differences in the inhibition of p24 release and virus spread. Virus emergence was the consequence of suboptimal inhibition of HIV replication and was not due to the selection of resistant variants. Cell-to-cell HIV transfer, a potent means of virus replication, was less sensitive to IFN than infection by cell-free virions. These results suggest that IFN are less active in cell cultures than initially thought. They help explain the incomplete protection by naturally secreted IFN during HIV infection and the unsatisfactory outcome of IFN treatment in HIV-infected patients.

Cytokine therapy or structured treatment interruptions in HIV infection: which is best?

Continuous highly active antiretroviral therapy (HAART) is the treatment of choice for HIV patients in order to prevent opportunistic infection or AIDS-related morbidity and mortality. However, new HIV treatment strategies are needed to face the emerging problems related to long-term toxicities and failures of HAART. Moreover, total eradication and complete restoration of immune system function cannot be achieved by HAART alone. Therefore, in an attempt to increase the natural immunity of HIV-infected patients, immune-based therapies have been investigated. This review is intended to provide an update on the use of immune-based therapies, in particular structured treatment interruptions and cytokines, such as IL-2 and IFN-alpha, as potential stimulants of the immune system of patients with HIV-infections and to discuss risks and benefits of each alternative. Ongoing and future clinical trials will provide a rationale for their use in clinical practice and will determine how these strategies can be combined to optimise HAART.

Low-dose IFN-alpha monotherapy in treatment-naive individuals with HIV-1 infection: evidence of potent suppression of viral replication

To evaluate the safety and antiviral action of interferon-alpha (IFN-alpha) in HIV-1 infection, we undertook a proof of concept study in 27 treatment-naive patients. Eligible patients comprised two groups: the IFN-alphaT group (n = 17), which received 5 MIU IFN-alpha s.c. daily for 32 consecutive days, and the IFN-alphaNT group (n = 10), which did not receive IFN-alpha prior to highly active antiretroviral therapy (HAART), which was commenced on day 28 in both groups. IFN-alphaTreatment was well tolerated in 14 of the 17 patients of the IFN-alphaT group who completed the study. The mean HIV RNA reduction in the IFN-alphaT group on day 14 was 1.1 log(10). Viral load suppression was inversely associated with baseline viral load (p = 0.031). Four weeks after initiation of HAART, IFN-alphaT and IFN-alphaNT group patients had 2.40 and 1.82 log(10) HIV RNA reduction from baseline, respectively (p < 0.001). There was no evidence of cross-resistance with existing antiretrovirals in patients with HIV-RNA rebound after initial plasma viral load decline > or = 1 log(10) during IFN-alpha monotherapy. Thus, low daily IFN-alpha exhibits potent anti-HIV-1 activity in vivo without serious adverse effects. These properties render IFN-alpha an attractive candidate for further assessment as a constituent of HAART.

A randomized trial of interferon alpha therapy for HIV type 1 infection

The immunologic and virologic efficacy and safety of interferon a (IFN-alpha) administered in combination with zidovudine (ZDV) and zalcitabine (ddC) was evaluated in HIV-infected subjects with CD4+ cell counts between 300 and 500 cells/ml and no more than 14 weeks of prior antiretroviral therapy. A total of 256 subjects enrolled in an open-label, randomized controlled trial. Subjects were randomized equally into treatment groups. All subjects received ZDV and ddC, while half also receive IFN-alpha (3 MU subcutaneously every 24 hr). At 48 weeks the median average area under the curve minus baseline (AAUCMB) for plasma HIV-1 RNA for the two-drug group was -0.68 versus -0.75 log10 copies/ml for the IFN-alpha group (p = 0.046). Mean HIV-1 RNA changes from baseline to 48 weeks for these groups were -0.65 and -1.12 log10 copies/ml, respectively (p = 0.010). The median AAUCMB for CD4+ cell count for the two-drug group was 28 versus -1 cells/mm3 for the IFN-alpha group (p = 0.011). Neutropenia, anemia, and drug intolerance were more common in the IFN-alpha group. This study demonstrates that IFN-alpha inhibits HIV-1 replication but attenuates the CD4+ cell response to dual therapy with ZDV and ddC.

Interferon treatment of two patients with quadruple infection with hepatitis C virus (HCV), human immunodeficiency virus (HIV), hepatitis G virus (HGV), and TT virus (TTV)

We administered interferon (IFN) to two patients who had quadruple infection with hepatitis C virus (HCV), human immunodeficiency virus (HIV), hepatitis G virus (HGV), and TT virus (TTV), a recently isolated novel DNA virus. Nine mega-units of natural alpha-IFN were administered daily during the first two weeks and thrice weekly during the following 22 weeks (total dose, 720 mega-units). In both cases, serum alanine aminotransferase (ALT) levels decreased during IFN administration but increased thereafter. The concentrations of HCV, HIV, HGV, and TTV declined with the administration of IFN. However, the concentrations of these 4 viruses increased after the cessation of IFN with the except of TTV in patient 2 which disappeared during treatment and did not subsequently reappear. IFN reduced the concentrations of 4 viruses, in an apparently independent manner.

Lack of efficacy of low dose oral interferon alfa in symptomatic HIV-1 infection: a randomised, double blind, placebo controlled trial

BACKGROUND

Interferon alfa (IFN-alpha) exhibits dose related in vitro activity against human immunodeficiency virus (HIV), with complete inhibition of HIV replication at IFN-alpha concentrations > or = 256 IU/ml. In mid-1990, Kenyan investigators reported that oral administration of an extremely low dose (150 IU/day) of natural human (nHu) IFN-alpha resulted in complete alleviation of AIDS related complex and AIDS symptoms and resolution of opportunistic infections without additional treatment. Moreover, loss of HIV antibody seropositivity was reported in approximately 10% of treated patients. Subsequent small studies failed to substantiate these spectacular claims, but controversy on the efficacy of this treatment persisted.

METHODS

We studied 559 adult Ugandan patients with WHO stage 2-4 HIV infection and a Karnofsky performance score of more than 50, who had not received any drugs with antiretroviral activity in the previous 3 months. The patients were randomly assigned in a double blind fashion either to 150 IU oral nHuIFN-alpha/day or placebo. The duration of treatment was extended from 28 weeks to 60 weeks 9 months after enrollment had started. At that time 112 subjects had already received 28 weeks of treatment and been discontinued from the study.

RESULTS

Both study groups were comparable with respect to all baseline characteristics studied, except that the nHuIFN-alpha group had slightly lower absolute CD4+ lymphocyte counts (median 60.7 x 10(6)/l) than the placebo group (median 85.3 x 10(6)/l) (p = 0.033). Therefore, all analyses were adjusted for CD4+ lymphocyte counts at entry. In both treatment groups there was relentless progression of HIV disease. Subjects treated with nHuIFN-alpha and placebo had similar mortality, disease progression rates, decline of CD4+ lymphocyte counts and Karnofsky performance scores, and prevalence of symptoms. No patient reverted to HIV-1 seronegative antibody status. Serious adverse events were not seen. Quality control of the study medication documented that the active drug indeed contained IFN-alpha activity.

CONCLUSIONS

The current large, randomised, double blind, placebo controlled study did not show any benefit from oral treatment with 150 IU nHuIFN-alpha/day in a population of African patients with symptomatic HIV infection.

Differential effects of human immunodeficiency virus type 1 envelope protein gp120 on interferon production by mononuclear cells from adults and neonates

While considerable progress in examining the course of human immunodeficiency virus (HIV) infection in adults has been made, a better understanding of the natural history of perinatal HIV infection remains to be obtained. Dysregulation of the production and functions of various cytokines, especially the interferons (IFNs), during HIV infections has been reported. Using an in vitro model system, we examined the effects of the HIV type 1 envelope protein, gp120 (10, 50, and 100 ng/ml), on gamma IFN (IFN-gamma) and IFN-alpha production by lymphocytes from neonates and adults and also examined the potential regulatory effects of gp120 on phorbol 12-myristate acetate (PMA)- and Sendai virus-induced IFN-gamma and IFN-alpha production by lymphocytes. PMA at a concentration of 50 ng/ml plus 50 ng of calcium ionophore A23187 per ml was used to induce IFN-gamma, while 150 hemagglutinating units of Sendai virus was used to induce IFN-alpha production. The antiviral activity of both IFN-alpha and IFN-gamma in leukocyte culture supernatants was assayed on BG-9 cells by a dye uptake technique using vesicular stomatitis virus as a challenge virus. Placental cord blood leukocyte (CBL) samples from healthy, term infants and adult peripheral blood leukocytes (APBL) produced no IFN in response to gp120. However, CBL produced significantly decreased levels of IFN-gamma compared with APBL in response to PMA plus ionophore. gp120 significantly suppressed both Sendai virus-induced IFN-alpha and PMA-induced IFN-gamma production by both CBL and APBL in a dose-dependent manner. However, gp120-induced suppression of IFN-alpha and IFN-gamma was significantly greater with CBL than with APBL. Treatment of CBL and APBL with gp120 did not induce any phenotypic alteration of the CD45 RO+ subset. Increased suppression of IFN-alpha and IFN-gamma production by gp120 in neonates may partially explain their apparent increased susceptibility to the clinical progression of HIV infections compared with that of adults.

Markers predicting progression of human immunodeficiency virus-related disease

Human immunodeficiency virus (HIV) interacts with the immune system throughout the course of infection. For most of the disease process, HIV activates the immune system, and the degree of activation can be assessed by measuring serum levels of molecules such as beta 2-microglobulin and neopterin, as well as other serum and cell surface phenotype markers. The levels of some of these markers correlate with clinical progression of HIV disease, and these markers may be useful as surrogate markers for development of clinical AIDS. Because the likelihood and timing of development of clinical AIDS following seroconversion, for any particular individual, are not readily predictable, the use of nonclinical disease markers has become critically important to patient management. Surrogate markers of HIV infection are, by definition, measurable traits that correlate with disease progression. An ideal marker should identify patients at highest risk of disease progression, provide information on how long an individual has been infected, help in staging HIV disease, predict development of opportunistic infections associated with AIDS, monitor the therapeutic efficacy of immunomodulating or antiviral treatments, and the easily quantifiable, reliable, clinically available, and affordable. This review examines the current state of knowledge and the role of surrogate markers in the natural history and treatment of HIV infection. The clinical usefulness of each marker is assessed with respect to the criteria outlined for the ideal surrogate marker for HIV disease progression.

Zidovudine. An update of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy

Zidovudine remains the mainstay in the treatment of patients infected with human immunodeficiency virus (HIV). The drug delays disease progression to acquired immunodeficiency syndrome (AIDS) and to AIDS-related complex (ARC), reduces opportunistic infections, and increases survival in patients with advanced HIV infection. There is evidence to suggest that zidovudine also delays disease progression in patients with mild symptomatic disease. Although one study has shown zidovudine to have no significant beneficial effects on survival or disease progression in patients with asymptomatic HIV infection, several other studies have shown zidovudine to delay disease progression in this patient group. Results from related ongoing studies are awaited with interest. Zidovudine reduces the incidence of AIDS dementia complex (ADC) and appears to prolong survival in these patients, and improves other neurological complications of HIV infection. The drug also appears to enhance the efficacy of interferon-alpha in patients with Kaposi's sarcoma. Although zidovudine is widely used as postexposure prophylaxis following accidental exposure to HIV, its efficacy in preventing seroconversion is unclear. Whether zidovudine prevents vertical transmission also remains to be determined. The overall efficacy of zidovudine in the treatment of children with HIV infection appears similar to that in adults despite more rapid disease progression in younger patients. Zidovudine-resistant isolates can emerge as early as after 2 months' therapy, and primary infection with zidovudine-resistant strains has been documented. Both zidovudine resistance and the syncytium-inducing HIV phenotype appear to be associated with poor clinical outcome. However, zidovudine resistance may revert on drug withdrawal or switching to an alternative therapy. Zidovudine-associated haematotoxicity may be dose-limiting. Nonhaematological adverse events associated with zidovudine therapy are generally mild and usually resolve spontaneously. Dosages of approximately 500 to 600 mg/day appear to be at least as effective as dosages of 1200 to 1500 mg/day and are better tolerated in patients with less advanced disease. However, optimal dosage are unclear. Despite beneficial effects, zidovudine monotherapy is not curative. There is evidence to suggest that the concomitant administration of zidovudine with didanosine or zalcitabine is effective in patients with HIV disease progression despite receiving zidovudine monotherapy, and there is some evidence that concomitant zidovudine plus didanosine therapy is more effective than alternating monotherapy. However, results from studies of combination therapy in asymptomatic patients, and from comparative combination therapy studies are awaited. Cotherapy with agents that augment haematopoiesis allows the continuation of therapeutic zidovudine dosages.(ABSTRACT TRUNCATED AT 400 WORDS)

Low-dose interferon alpha combined with zidovudine in patients with AIDS-associated Kaposi's sarcoma

Forty patients with AIDS-associated Kaposi's sarcoma (KS) treated with the combination of interferon alpha-2b (IFN-alpha) 10-20 MU day-1 and zidovudine (ZDV), 500-800 mg day-1, were evaluated for safety and efficacy. Eighteen patients (45%) had an overall response (CR+PR) at 3 months and a response persisting for a median of 14 (3-27) months. Patients with a CD4 count of less than 300 mm-3, prior to opportunistic infections or constitutional symptoms, were less likely to respond. However, between 28.5% and 36% of patients with a low CD4 count did respond to combined therapy. This is higher than would be predicted from single agent IFN-alpha therapy. Twelve of 28 patients (42.8%) receiving 10 MU day-1 of IFN-alpha (low dose) had an overall response. In addition, patients tolerated this dose of IFN-alpha better, presenting fewer flu-like symptoms and displayed a trend toward less anaemia. p24 antigen decreased in six out of nine evaluable cases, four of whom were treated with low-dose IFN-alpha. Low-dose IFN-alpha plus ZDV seems to be a useful and well-tolerated therapy for KS with antitumoral and antiviral activity. Patients without 'bad prognostic markers' are most likely to show improvement.

Treatment of HIV infection: the antiretroviral nucleoside analogues. Nucleoside analogues: combination therapy

Combination antiretroviral therapy is an important development in the management of HIV infection. AZT with ddC is the first such combination to be approved for clinical use. Several issues remain, however, including the precise clinical benefit and toxicity of combination therapy, its effect on drug resistance, and the development of ever more effective therapeutic strategies.

Interferon-alpha treatment in HTLV-I-associated myelopathy. Studies of clinical and immunological aspects

We treated 17 patients with HTLV-I-associated myelopathy (HAM) with interferon-alpha (IFN-alpha) in an open, nonrandomized, uncontrolled study. They were administered 1.5-9.0 x 10(6) international units of IFN-alpha daily for 4 weeks, and 4 patients showed a marked clinical response, 7 showed a moderate response and the others did not show any clinical response. Increased unstimulated (spontaneous) peripheral blood lymphocyte (PBL) proliferation was observed in all patients who were measured lymphocyte transformation. Spontaneous PBL proliferation was significantly inhibited by IFN-alpha treatment (P less than 0.01), whereas anti-HTLV-I-antibodies did not show any significant changes. Likewise, decreased stimulation indices to phytohemagglutinin (SI) due to increased spontaneous PBL proliferation were significantly increased after IFN-alpha treatment (P less than 0.01). In the patients who showed marked clinical responses, the changes of SI in IFN-alpha treatment were higher than those in other patients. These data indicate that further studies are warranted for evaluation of IFN-alpha treatment of HAM in a randomized, controlled study.

Metabolic interaction of recombinant interferon-beta and zidovudine in AIDS patients

Zidovudine (AZT), the only currently approved drug for treatment of human immunodeficiency virus (HIV) in AIDS, is known to be metabolized by mammalian systems to a variety of metabolites including 3'-azido-3'-deoxy-5'-O-glucuronide (GAZT). Interferons (IFNs) are known to alter the microsomal enzyme system responsible for the metabolism of some compounds. The aim of the present study was to investigate the effect of combination therapy of recombinant (r) IFN-beta and AZT on the rates of metabolism of AZT in AIDS patients. AZT was given orally (200 mg every 4 h) for 8 weeks prior to initiation of rIFN-beta therapy (45 X 10(6) U/day, s.c.). Serum samples from 8 patients were obtained prior to and at days 3 and 15 following initiation of rIFN-beta therapy. Serum was analyzed by high-performance liquid chromatography (HPLC) for both AZT and GAZT. The serum data were analyzed by a computer-assisted pharmacokinetics program that calculates rates of AZT metabolism. The half life for AZT was increased approximately two-fold by day 15. The rate of metabolism of AZT was diminished from 1.43 h-1 prior to IFN-beta therapy, to 0.4 h-1 and 0.05 h-1 at days 3 and 15, respectively. The volume of distribution of AZT was 2 l/kg at day 0 and increased to 3.2 and 3.5 l/kg on days 3 and 15, respectively. In conclusion, the results indicate that rIFN-beta inhibits the rate of AZT metabolism in AIDS patients.

The use of interferon-alpha in virus infections

The interferons (IFN) act too slowly to arrest acute viral infections, but interferon-alpha (IFN alpha) preparations have proved useful in some chronic infections and will clearly be used increasingly in these in the future. In the preparations derived from human leucocytes or cultured B lymphoblastoid cells, which are in routine clinical use, mixtures of a number of distinct subtypes of human IFN alpha have been identified. There are also 3 slightly different versions of the same single subtype, IFN alpha-2, made by recombinant DNA procedures in bacteria. IFN alpha preparations are injected intramuscularly or subcutaneously. Dose-related side effects are common but usually tolerable, but prolonged treatment may cause increasing fatigue and depression. Some patients form neutralising antibodies which block the effects of the IFN; these appear to be relatively more common after recombinant IFN alpha-2 than after IFN derived from human cells. Given intranasally, IFN alpha can prevent a subsequent experimental rhinovirus infection, or the spread of natural colds within a family. Repeated administration progressively damages the nasal mucosa, so that long term prophylaxis is not possible. IFN alpha has proved useful in patients with papillomavirus warts of the larynx, ano-genital region (condyloma acuminata) and skin (common warts). Treatment regimens remain to be optimised and are likely to include surgery or other treatments. IFN alpha and zidovudine (azidothymidine) synergistically inhibit the growth of HIV in vitro, and combination are on trial in patients with early AIDS. Very large doses of IFN alpha are effective against Kaposi's sarcoma in some AIDS patients. In chronic hepatitis B, continuing virus replication may lead to cirrhosis or primary liver cancer. Earlier clinical trials with IFN alpha gave inconclusive results, but recent large studies have confirmed that 25 to 40% of patients obtain benefit; this probably results from both the antiviral and the immunomodulatory effects of IFN alpha. In patients with chronic hepatitis C, the biochemical markers usually improve rapidly during IFN alpha administration, but relapse if treatment is stopped after only a few months; to increase the chances of sustained cure, the treatment period is now being prolonged.

Inhibition of HIV-1 transmission by interferon and 3'-azido-3'-deoxythymidine during de novo infection of promonocytic cells

HIV-1 infection of promonocytic U937 cells was used to examined induction of IFN-alpha/beta gene expression and to determine the inhibitory effects of IFN-alpha 2 and/or AZT on de novo HIV-1 infection, initiated either by coculture of virus-shedding U9-IIIB cells with uninfected cells or by incubation of U937 cells with virus-containing supernatants. Usually 21-28 days were required to transmit virus to greater than 90% of the cell culture. HIV-1 infection did not stimulate constitutive production of endogenous IFN-alpha 1/alpha 2 or IFN-beta genes, although induction of IFN RNA was observed following coinfection with the paramyxovirus Sendai. Exogenous rIFN-alpha 2 treatment decreased the intracellular accumulation of viral RNA 5- to 20-fold as determined by Northern blot analysis and the extracellular levels of HIV-1 as measured by p24 ELISA antigen capture. The effect was most dramatic at a time coincident with the rapid increase in virus spread through the cell culture (Days 10-18). During the fourth week of infection, HIV-1 multiplication was able to overcome the IFN-induced block in virus spread. AZT was not effective in limiting virus spread in the cocultivation experiments. When U937 cells were infected with virus-containing supernatants from U9-IIIB cells, IFN and AZT acted in combination to limit the number of infected cells and to inhibit intracellular accumulation of viral RNA. These experiments suggest that subtle differences in the mode of virus transmission in monocytic cells may alter the efficacy of combination antiretroviral therapy.

The role of interferons in the control of HIV replication in macrophages

Interferons can suppress the replication of certain retroviruses, including oncogenic murine retroviruses. In recent studies of the Lentivirinae subfamily of Retroviridae, an endogenous, immunologically induced interferon was found to restrict the replication of visna in macrophages. Several studies have shown that the replication of a human lentivirus, the human immunodeficiency virus (HIV), is also susceptible to interferon control. Here we review the evidence that interferons can protect macrophages from HIV in vitro. Macrophages treated with interferons or bacterial lipopolysaccharide (LPS) become essentially nonpermissive for HIV replication. Using the polymerase chain reaction to amplify HIV proviral DNA, we now report that interferon and LPS act to restrict the formation of proviral DNA. Effects on any several steps in the HIV life cycle may explain this data, and single-cycle infection studies are needed to define the precise roles of these agents. Taken together, these findings may explain the restricted replication of HIV in macrophages in vivo and suggest an antiviral role for endogenously produced interferon in the maintenance of the prolonged asymptomatic period which typically follows HIV infection. Interferons are currently undergoing clinical trials to determine if they have antiviral effects in HIV-infected patients.