Synthesis of 1-[ω-(Bromophenoxy)alkyl]-3-naphthalenylmethyl Derivatives of Uracil and Their Analogues As Probable Inhibitors of Human Cytomegalovirus Replication.

The synthesis of a new series of 1-[ω-(bromophenoxy)alkyl]-uracil derivatives containing in position 3 naphthalen-1-yl-, naphthalen-2-yl-, 1-bromonaphthalen-2-ylmethyl, benzyl, and anthracene 9-methyl fragment was carried out. The antiviral properties of the synthesized compounds were studied against human cytomegalovirus. It was found that the compound that contained a bridge of five methylene groups has a high anti-cytomegalovirus activity in vitro.

Synthesis of 1-[ω-(Bromophenoxy)alkyl]-3-Naphthalenylmethyl Uracil Derivatives and Their Analogues as Probable Inhibitors of Human Cytomegalovirus Replication.

A new series of 1-[ω-(bromophenoxy)alkyl]-uracil derivatives containing naphthalen-1-yl, naphthalen-2-yl, 1-bromonaphthalen-2-ylmethyl, benzyl, and anthracene-9-ylmethyl fragments in position 3 of uracil residue was synthesized. The antiviral properties of the synthesized compounds against human cytomegalovirus were studied. It was found that the compound containing a bridge consisting of five methylene groups exhibits a high anti-cytomegalovirus activity in vitro.

Lymphocyte-independent pathways underlie the pathogenesis of murine cytomegalovirus-associated secondary haemophagocytic lymphohistiocytosis.

Haemophagocytic lymphohistiocytosis (HLH) constitutes a spectrum of immunological disorders characterized by uncontrolled immune activation and key symptoms such as fever, splenomegaly, pancytopenia, haemophagocytosis, hyperferritinaemia and hepatitis. In genetic or primary HLH, hyperactivated CD8+ T cells are the main drivers of pathology. However, in acquired secondary HLH, the role of lymphocytes remains vague. In the present study the involvement of lymphocytes in the pathogenesis of a cytomegalovirus-induced model of secondary HLH was explored. We have previously reported CD8+ T cells to be redundant in this model, and therefore focused on CD4+ helper and regulatory T cells. CD4+ T cells were activated markedly and skewed towards a proinflammatory T helper type 1 transcription profile in mice displaying a severe and complete HLH phenotype. Counter to expectations, regulatory T cells were not reduced in numbers and were, in fact, more activated. Therapeutic strategies targeting CD25high hyperactivated T cells were ineffective to alleviate disease, indicating that T cell hyperactivation is not a pathogenic factor in cytomegalovirus-induced murine HLH. Moreover, even though T cells were essential in controlling viral proliferation, CD4+ T cells, in addition to CD8+ T cells, were dispensable in the development of the HLH-like syndrome. In fact, no T or B cells were required for induction and propagation of HLH disease, as evidenced by the occurrence of cytomegalovirus-associated HLH in severe combined immunodeficient (SCID) mice. These data suggest that lymphocyte-independent mechanisms can underlie virus-associated secondary HLH, accentuating a clear distinction with primary HLH.

Distribution and effects of amino acid changes in drug-resistant α and ß herpesviruses DNA polymerase.

Emergence of drug-resistance to all FDA-approved antiherpesvirus agents is an increasing concern in immunocompromised patients. Herpesvirus DNA polymerase (DNApol) is currently the target of nucleos(t)ide analogue-based therapy. Mutations in DNApol that confer resistance arose in immunocompromised patients infected with herpes simplex virus 1 (HSV-1) and human cytomegalovirus (HCMV), and to lesser extent in herpes simplex virus 2 (HSV-2), varicella zoster virus (VZV) and human herpesvirus 6 (HHV-6). In this review, we present distinct drug-resistant mutational profiles of herpesvirus DNApol. The impact of specific DNApol amino acid changes on drug-resistance is discussed. The pattern of genetic variability related to drug-resistance differs among the herpesviruses. Two mutational profiles appeared: one favoring amino acid changes in the Palm and Finger domains of DNApol (in α-herpesviruses HSV-1, HSV-2 and VZV), and another with mutations preferentially in the 3'-5' exonuclease domain (in ß-herpesvirus HCMV and HHV-6). The mutational profile was also related to the class of compound to which drug-resistance emerged.

[Orf nodules and immunosuppression: a case report and review of therapeutics]. / Nodules d'Orf et immunosuppression : rapport d'un cas et revue des therapeutiques.

In immunocompromised patient, parapoxvirus infection can be extensively necrotic and recurrent evolution. We describe a case of Orf nodule in a liver transplanted woman. We will consider the therapeutic options in case of infections by parapox in immunosuppressive patients, as described in the medical literature. In our specific case, local application of cidofovir (concentration of 1 %) together with local antiseptic solution, povidone iodine, led to complete remission of the lesion without any sign of toxicity. Finally, we will consider the therapeutic use of local cidofovir.

Activity and mechanism of action of HDVD, a novel pyrimidine nucleoside derivative with high levels of selectivity and potency against gammaherpesviruses.

A novel nucleoside analogue, 1-[(2S,4S-2-(hydroxymethyl)-1,3-dioxolan-4-yl]5-vinylpyrimidine-2,4(1H,3H)-dione, or HDVD, was evaluated against a wide variety of herpesviruses and was found to be a highly selective inhibitor of replication of the gammaherpesviruses Kaposi's sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus (EBV). HDVD had also a pronounced inhibitory activity against murine herpesvirus 68 (MHV-68) and herpes simplex virus 1 (HSV-1). In contrast, replication of herpesvirus saimiri (HVS), HSV-2, and varicella-zoster virus (VZV) was weakly inhibited by the compound, and no antiviral activity was determined against human cytomegalovirus (HCMV) and rhesus rhadinovirus (RRV). The HDVD-resistant virus phenotype contained point mutations in the viral thymidine kinase (TK) of HSV-1, MHV-68, and HVS isolates. These mutations conferred cross-resistance to other TK-dependent drugs, with the exception of an MHV-68 mutant (E358D) that exhibited resistance only to HDVD. HSV-1 and HVS TK-mutants isolated under selective pressure with bromovinyldeoxyuridine (BVDU) also showed reduced sensitivity to HDVD. Oral treatment with HDVD and BVDU was assessed in an intranasal model of MHV-68 infection in BALB/c mice. In contrast to BVDU treatment, HDVD-treated animals showed a reduction in viral DNA loads and diminished viral gene expression during acute viral replication in the lungs in comparison to levels in untreated controls. The valyl ester prodrug of HDVD (USS-02-71-44) suppressed the latent infection in the spleen to a greater extent than HDVD. In the present study, HDVD emerged as a highly potent antiviral with a unique spectrum of activity against herpesviruses, in particular, gammaherpesviruses, and may be of interest in the treatment of virus-associated diseases.

In vitro-selected drug-resistant varicella-zoster virus mutants in the thymidine kinase and DNA polymerase genes yield novel phenotype-genotype associations and highlight differences between antiherpesvirus drugs.

Varicella zoster virus (VZV) is usually associated with mild to moderate illness in immunocompetent patients. However, older age and immune deficiency are the most important risk factors linked with virus reactivation and severe complications. Treatment of VZV infections is based on nucleoside analogues, such as acyclovir (ACV) and its valyl prodrug valacyclovir, penciclovir (PCV) as its prodrug famciclovir, and bromovinyldeoxyuridine (BVDU; brivudin) in some areas. The use of the pyrophosphate analogue foscarnet (PFA) is restricted to ACV-resistant (ACV(r)) VZV infections. Since antiviral drug resistance is an emerging problem, we attempt to describe the contributions of specific mutations in the viral thymidine kinase (TK) gene identified following selection with ACV, BVDU and its derivative BVaraU (sorivudine), and the bicyclic pyrimidine nucleoside analogues (BCNAs), a new class of potent and specific anti-VZV agents. The string of 6 Cs at nucleotides 493 to 498 of the VZV TK gene appeared to function as a hot spot for nucleotide insertions or deletions. Novel amino acid substitutions (G24R and T86A) in VZV TK were also linked to drug resistance. Six mutations were identified in the "palm domain" of VZV DNA polymerase in viruses selected for resistance to PFA, PCV, and the 2-phophonylmethoxyethyl (PME) purine derivatives. The investigation of the contributions of specific mutations in VZV TK or DNA polymerase to antiviral drug resistance and their impacts on the structures of the viral proteins indicated specific patterns of cross-resistance and highlighted important differences, not only between distinct classes of antivirals, but also between ACV and PCV.

Activities of different classes of acyclic nucleoside phosphonates against BK virus in primary human renal cells.

BK virus (BKV), a virus belonging to the polyomavirus family, is a circular double-stranded DNA virus that causes nephropathies in immunocompromised patients after kidney or bone marrow transplantation. The occurrence of polyomavirus-associated nephropathy in kidney transplant patients may trigger graft loss, and guidelines for the management of BKV infection have not yet been clearly established. Treatment of BKV nephropathy with cidofovir (CDV) {(S)-1-[3-hydroxy-2-(phosphonomethoxy)propyl]cytosine (HPMPC)}, an acyclic phosphonate analogue of dCMP with a broad antiviral activity against DNA virus infections, has been proposed. The benefit of this small-molecule-based treatment has been evaluated only with a limited number of cases. In this study, we report the evaluation of three different classes of acyclic nucleoside phosphonates for their activities against BKV replication in two different primary renal cells: renal proximal tubular epithelial cells (RPTECs) and human renal cortical epithelial (HRCE) cells. The data indicate that besides HPMPC and its cyclic form, (S)-1-[3-hydroxy-2-(phosphonomethoxy)propyl]-5-azacytosine (HPMP-5-azaC), cyclic HPMP (cHPMP)-5-azaC, hexadecyloxyethyl (HDE)-cHPMP-5-azaC, and 9-[2-(phosphonomethoxy)ethyl]guanine (PMEG) are the most selective inhibitors of BKV replication. On the contrary, leflunomide, which has also been proposed for the management of BKV-associated diseases, is not able to inhibit BKV replication at nontoxic concentrations.

Synthesis and Antiviral Properties of 1-Substituted 3-[ω-(4-Oxoquinazolin-4(3H)-yl)alkyl]uracil Derivatives.

A series of uracil derivatives containing a 4-oxoquinazoline fragment bound to the nitrogen atom N3 of the pyrimidine ring by a short methylene bridge was synthesized to search for new antiviral agents. Some compounds in this series are shown to exhibit high inhibitory activity against human cytomegalovirus and the varicella zoster virus in a HEL cell culture.

Topical treatment of CIN 2+ by cidofovir: results of a phase II, double-blind, prospective, placebo-controlled study.

OBJECTIVE: Randomized controlled trial evaluating a topical treatment for cervical intraepithelial neoplasia 2 and 3 (CIN 2+) using cidofovir. METHODS: Fifty-three women with a biopsy-proven CIN 2+ were randomly assigned, 6 weeks before their planned conisation, either 3 applications of 3 ml 2% cidofovir in Intrasite gel in a cervical cap or a placebo (the same volume of Intrasite alone). A cervical sample for high-risk types of human papillomaviruses (HPV) (Hybrid Capture 2 or HC2) was taken before treatment and before conisation. The cone was submitted for pathological examination, and subsequently, along with the initial biopsy, to in situ hybridization (ISH) for high-risk HPV. RESULTS: Forty-eight patients were treated and followed according to the protocol, (23 cidofovir, and 25 placebo). Fourteen of the 23 cones were free of any CIN (60.8%) in the cidofovir group. Only 5 of 25 cones were free of any CIN (20%) in the placebo group (p<0.01). The difference remained significant in the ITT group (p<0.05). In the per-protocol and ITT populations, we observed more frequent viral clearance in the cidofovir group, but the difference was significant only when evaluated by ISH and not by HC2. No systemic toxicity was observed. Cervico-vaginal side effects of cidofovir were limited, and not statistically different from placebo. CONCLUSION: The medical topical treatment with cidofovir, at this point, cannot replace conisation, but it is a promising candidate for topical chemotherapy of CIN 2+ lesions; a larger prospective randomized study is needed to confirm our results.

The novel primaquine derivatives of N-alkyl, cycloalkyl or aryl urea: synthesis, cytostatic and antiviral activity evaluations.

The novel urea primaquine derivatives 3a-i were prepared by aminolysis of benzotriazolide 2 with the corresponding amine in the presence or absence of triethylamine. Compound 2 was prepared by acylation of primaquine with 1-benzotriazole carboxylic acid chloride. Among all compounds evaluated, the pyridine derivative 3h exhibited the best cytostatic activities against colon carcinoma, human T-lymphocyte and murine leukemia. However, this compound showed also rather marked cytotoxicity towards human normal fibroblasts. The highest selectivity in the inhibitory effects on human malignant tumor cell lines vs. normal fibroblasts was found for ureas 3c, 3d and 3g. Results of broad antiviral evaluation showed that pyridine and phenethyl derivatives of urea 3h and 3g exhibited some selective inhibition against cytomegalovirus.

[Novel therapeutic weapons against poxviruses]. / Nouvelles armes thérapeutiques contre les poxvirus.

Poxviruses include several pathogens responsible for diseases recognized as important for human health, such as smallpox, monkeypox, orf and molluscum contagiosum. Smallpox, whose etiological agent is Variola virus, is a highly contagious disease which was eradicated last century. Today, the potential use of Variola virus in bioterrorism is real. Hence, efforts have been intensified for the selection of novel anti-poxvirus compounds. The increased understanding of the poxviral replication, the establishment of threedimensional cell cultures, as well as the validation of several animal models, have led to the discovery and the development of new and promising classes of compounds active against poxviruses. Cidofovir, an acyclic cytosine phosphonate analogue and hexadecylpropanediol-cidofovir (CMX001), one of its prodrug orally bioavailable, inhibit poxvirus replication in vitro, ex vivo and in vivo by targeting the viral DNA polymerase. Another compound, ST-246, inhibits a crucial step of the orthopoxvirus morphogenesis. Its antiviral activity has been demonstrated in several animal models, and its safety has been confirmed in healthy human volunteers following a phase I clinical trial. Recent developments made in vitro, ex vivo, in vivo and in humans, in terms of antiviral treatments available of poxvirus infections, are discussed in this review.

Treatment of intraurethral condylomata acuminata with surgery and cidofovir instillations in two immunocompromised patients and review of the literature.

Condylomata acuminata (CA) or anogenital warts are benign proliferative lesions caused by low-risk human papillomaviruses (HPV). Treating CA can be very frustrating for patients and clinicians due to the high recurrence rates. Immunosuppression is associated with larger size of CA that are more frequently resistant to treatment. Surgical approaches tend to be poorly effective in the long-term because of high recurrence rates related to the persistence of HPV-infected cells. In our search to find an agent to treat intraurethral CA with minor or no side effects, we evaluated intraurethral cidofovir in two male patients, who were under immunosuppressing therapy due to organ transplantation and suffered from extensive urethral HPV lesions. Both patients underwent biopsy of the lesions and initial transurethral resection. In our first case, intraurethral cidofovir instillations were started after 2 months due to recurrence after surgical treatment. In our second case, intraurethral cidofovir was administered after surgery because of incomplete resection of extensive lesions. Because of persistent or rapidly recurrent lesions despite intraurethral cidofovir instillations, the first patient needed two additional surgical interventions while the second patient underwent one additional surgical intervention. After surgical intervention, both patients received again adjuvant cidofovir instillations without side effects. Over a period of 56 weeks, both patients received each a total of 28 instillations with cidofovir. Following 3.5 years (patient 1) of the last cidofovir instillation, no recurrences were observed in our first patient. Following 6 months of the last cidofovir instillation (patient 2), two very small recurrent lesions in the most distal part of the urethra were observed in our second patient for which he will receive a cycle of 6 cidofovir instillations in the near future. Intraurethral cidofovir is a safe, easy-to-use, well-tolerated and an effective adjuvant to surgery for extensive intraurethral CA in immunocompromised patients.

Antiviral activity of HPMPC (cidofovir) against orf virus infected lambs.

(S)-1-[3-hydroxy-2-(phosphonomethoxy)propyl]cytosine [corrected] (HPMPC, cidofovir, CDV, Vistide) is an acyclic nucleoside analogue with a potent and selective activity against a broad spectrum of DNA viruses including the poxviruses. In this study we present the results of different treatment regimens in lambs experimentally infected with orf virus with different cidofovir formulations prepared in Beeler basis and Unguentum M. Our results show that choice of excipient, concentration of codofovir [corrected] and treatment regimen were all important to the clinical outcome of the therapy. Whilst one particular regimen appeared to exacerbate the lesion, treatment with 1% (w/v) cidofovir cream, prepared in Beeler basis, for 4 consecutive days did result in milder lesions that resolved in milder lesions that resolved [corrected] more quickly than untreated lesions. Furthermore the scabs of the treated animals contained significantly lower amounts of viable virus meaning there should be less contamination of the environment with virus than would normally occur.

Synthesis and biological evaluation of N- and O-alkylated bicyclic furanopyrimidines as non-nucleosidic inhibitors of human cytomegalovirus.

2'3'-Dideoxy furanopyrimidines were shown to display anti-HCMV activity via a non-nucleoside mechanism. Further studies into highly modified sugar derivatives led to the preparation of N-and O-alkylated C10 furanopyrimidine analogues, and this work is described herein. These compounds were tested against HCMV strains, and the first case of submicromolar activity was observed.

Antiviral potential of a new generation of acyclic nucleoside phosphonates, the 6-[2-(phosphonomethoxy)alkoxy]-2,4-diaminopyrimidines.

Three acyclic nucleoside phosphonates (ANPs) have been formally approved for clinical use in the treatment of 1) cytomegalovirus retinitis in AIDS patients (cidofovir, by the intravenous route), 2) chronic hepatitis B virus (HBV) infections (adefovir dipivoxil, by the oral route), and 3) human immunodeficiency virus (HIV) infections (tenofovir disoproxil fumarate, by the oral route). The activity spectrum of cidofovir {(S)- 1-[3-hydroxy-2-(phosphonomethoxy)propyl]cytosine [(S)-HPMPC)]}, like that of (S)-HPMPA [(S)-9-[3-hydroxy-2-(phosphonomethoxy)propyl]adenine) and (S)-HPMPDAP [(S)-9-[3-hydroxy-2-(phosphonomethoxy)propyl]-2, 6-diaminopurine), encompasses a broad spectrum of DNA viruses, including polyoma-, papilloma-, adeno-, herpes-, and poxviruses. Adefovir {9-[2-(phosphonomethoxy)ethyl]adenine (PMEA)} and tenofovir [(R)-9-[2-(phosphonomethoxy) propyl]adenine [(R)-PMPA)]} are particularly active against retroviruses (ie., HIV) and hepadnaviruses (ie., HBV); additionally, PMEA also shows activity against herpes- and poxviruses. We have recently identified a new class of ANPs, namely 6-[2-(phosphonomethoxy)alkoxy]-2,4-diaminopyrimidines, named, in analogy with their alkylpurine counterparts, HPMPO-DAPy, PMEO-DAPy, and (R)-PMPO-DAPy. These compounds exhibit an antiviral activity spectrum and potency that is similar to that of (S)-HPMPDAP, PMEA, and (R)-PMPA, respectively. Thus, PMEO-DAPy and (R)-PMPO-DAPy, akin to PMEA and (R)-PMPA, proved particularly active against HIV- 1, HIV-2, and the murine retrovirus Moloney sarcoma virus (MSV). PMEO-DAPy and (R)-PMPO-DAPy also showed potent activity against both wild-type and lamivudine-resistant strains of HBV. HPMPO-DAPy was found to inhibit different poxviruses (ie., vaccinia, cowpox, and orf) at a similar potency as cidofovir. HPMPO-DAPy also proved active against adenoviruses. In vivo, HPMPO-DAPy proved equipotent to cidofovir in suppressing vaccinia virus infection (tail lesion formation) in immunocompetent mice and promoting healing of disseminated vaccinia lesions in athymic-nude mice. The 6-[2-(phosphonomethoxy)alkoxy]-2,4-diaminopyrimidines offer substantial potential for the treatment of a broad range of retro-, hepadna-, herpes-, adeno-, and poxvirus infections.

The journey towards elucidating the anti-HCMV activity of alkylated bicyclic furano pyrimidines.

Bicyclic furanopyrimidines were recently discovered by us to be potent and selective inhibitors of VZV. Related studies to investigate the role of the sugar in this activity uncovered dideoxy furanopyrimidines as inhibitors of HCMV and this led to the preparation of highly modified long alkyl chain furanopyrimidines from the N- and O-alkylation of their parent bases. Herein we describe their synthesis and subsequent biological evaluation against HCMV. O-alkylated derivatives were almost invariably found to be at least equiactive with their N-alkylated counterparts. At this point, little change in activity has been found with large variation in N- and O-substituent.

[Verrucous carcinoma of the esophagus. A case report]. / Su di un caso di carcinoma verrucoso dell'esofago.

Verrucous carcinoma (VC) of the esophagus is a rare variant of squamous cell carcinoma and only 20 cases have so far been reported in the international literature. The neoplasm is usually highly differentiated, presents a slow growth pattern with invasion of surrounding organs rather than blood-borne metastases. Recently, a causative role of human papillomavirus (HPV) has been hypothesized. The case of a patient affected with locally advanced VC of the esophagus and treated by means of local antiviral therapy is reported. A 41-year-old male patient was admitted to our institution for persistent atypical thoracic pain. The imaging techniques (thoracic and abdominal CT scans; upper GI endoscopy; hydrosoluble contrast swallow; endoscopic US) revealed a cauliflower-like protruding esophageal mass, active mucosal mycosis, multiple ulcerations of the distal esophagus, as well as 2 broncho-esophageal fistulas. The neoplasm extended beyond the esophageal wall, infiltrating surrounding cervical and mediastinal organs and the patient presented with secondary esophageal achalasia and right bilobar pneumonia. The histologic specimen was consistent with VC of the esophagus and the presence of HPV infection was detected by means of qualitative PCR assay. The patient was deemed not fit for surgery and a local antiviral treatment with hydroxy-phosphonyl-methoxypropyl-cytosine 5 mg/kg a week was started. After initial response to treatment, the patient presented with sudden progression leading to further broncho-esophageal fistula treated with endoscopic stent placement and ultimate death 6 months after referral to our center. In keeping with international data, our case confirms that esophageal VC has a highly unfavorable outcome, despite its high degree of differentiation and slow growth pattern. The long natural history, the lack of specific symptoms and the presence of coexisting esophageal diseases delay the diagnosis and account for the local advancement of this malignancy. Surgery is the option of choice for early stage lesions and advanced VC does not seem to benefit from current chemotherapeutic regimens. The causative role of HPV and the advancements of molecular pharmacology might allow for effective treatment in high-risk patients.

Decreased production of cytokines after cytomegalovirus infection of marrow-derived stromal cells.

Cytomegalovirus (CMV) infection is frequently associated with graft failure in bone marrow transplant patients; the pathogenesis of this myelosuppression in not clearly understood. We have previously documented that CMV-induced myelosuppression is related to an alteration of the marrow microenvironment. To further investigate the effect of CMV on stromal cell function, conditioned media (CM) from CMV-infected or uninfected stromal cells were tested for their capacity to promote the growth of granulocyte/macrophage colony-forming cells (CFU-GM) and for their concentration in colony-stimulating factors (CSFs) such as interleukin-3 (IL-3), IL-6, granulocyte-macrophage and granulocyte colony-stimulating factors (GM-CSF and G-CSF). CM from CMV-infected stromal cells failed to sustain granulocyte-macrophage colony-forming unit (CFU-GM) growth. The production of IL-6, GM-CSF, and G-CSF, measured by enzyme-linked immunosorbent assay (ELISA), was 21,150 +/- 3392, 57 +/- 15, and 2340 +/- 717 pg/mL, respectively, in CMV-infected stromal cells stimulated by lipopolysaccharide (LPS) and was significantly decreased (p < 0.01) from the control values (177,138 +/- 98,692, 113 +/- 20, and 5533 +/- 1306 pg/mL). These results suggest that the myelosuppressive effect of CMV is primarily due to a lack of CSF production. To further document this hypothesis, primitive marrow progenitor cells (blast colony-forming cells [Bl-CFC]) cultured on CMV-infected stromal layer have been grown in the presence of IL-3 (20 ng/mL), IL-6 (20 ng/mL), GM-CSF (40 ng/mL), and G-CSF (50 ng/mL). Used alone, all these CSFs partially reverse the CMV-induced inhibition of Bl-CFC growth; the combination of these CSFs completely restores normal Bl-CFC values. These data strongly suggest that CMV-induced myelosuppression is related to the lack of CSF production by the cells of the marrow microenvironment.

Prevention of CMV-induced myelosuppression by anti-CMV antibodies: an in vitro model.

Pathogenesis of cytomegalovirus (CMV)-induced myelosuppression is not clearly understood and could be related to a direct toxic effect on the marrow progenitors and/or an alteration of the marrow environment. Myeloid progenitors (granulocyte-macrophage colony-forming units, CFU-GM) were not affected by incubation with increasing titers of CMV (10-10(5) plaque-forming units [pfu]/ml) during 2-6 h. By contrast, using the blast colony-forming cell (Bl-CFC) assay, we confirmed that CMV induced myelosuppression through an alteration of the marrow-derived stromal layer. Using this experimental model, we compared the capacity of nonspecific human immunoglobulins (IgG), specific polyclonal anti-CMV IgG, and a human monoclonal anti-CMV IgG to prevent the myelosuppressive effect of 10(4) pfu/ml of CMV. Specific anti-CMV IgG (polyclonal or monoclonal) at the concentration of 10 micrograms/ml were able to prevent the CMV-induced myelosuppressive effect, whereas nonspecific human IgG was not effective in this model. Our results suggest that 1) CMV-induced myelosuppression is related to an alteration of the marrow microenvironment, 2) specific monoclonal and polyclonal anti-CMV IgG prevent this myelosuppressive effect in vitro, and 3) human monoclonal anti-CMV IgG could be useful in vivo in the immunoprophylaxis of CMV infections.