Detection of zidovudine-resistant variants of HIV-1 in genital fluids

Heterosexual spread of HIV infection

Sexual transmission is the most common route of spread of human immunodeficiency virus (HIV), with heterosexual transmission of HIV infection accounting for 90% of those infected in 1992 and over 75% of the 10–12 million of those infected to date worldwide. Yet, heterosexual transmission is poorly understood. Since HIV can be transmitted from HIV-infected people who are asymptomatic as well as from those who have the acquired immunodeficiency syndrome (AIDS), we must better define the potential for transmission of HIV from HIV-infected individuals as well as the factors which influence the susceptibility of HIV-uninfected individuals.

Quantification of antiretroviral drugs for HIV-1 in the male genital tract: current data, limitations and implications for laboratory analysis

Antiretroviral therapy has reduced the morbidity and mortality associated with HIV-1/AIDS in developed countries. Viral replication in blood plasma is suppressed by antiretroviral drugs, whereas virus in the male genital tract is genetically and phenotypically unique and may not be suppressed. This viral compartmentalization affects antiretroviral drug penetration of the male genital tract and capacity for antiretroviral therapy to reduce sexual transmission. The problem of having two distinct viral populations within any given individual is compounded by the fact that antiretroviral drugs penetrate semen to varying degrees. Incomplete suppression of genital tract virus may yield drug-resistant virus and increase the risk of sexual transmission. This review critically appraises current studies of antiretroviral drug quantification in semen and suggests recommendations to address observed limitations.

Differences in HIV-1 pol Sequences From Female Genital Tract and Blood During Antiretroviral Therapy

OBJECTIVE

To determine whether HIV-1 replicates locally in the female genital tract during therapy, and to study whether endocervix is the dominant source of virus in cervicovaginal lavage fluid.

DESIGN

Sequence analyses of HIV-1 pol were performed from cervicovaginal secretions and blood plasma of HIV-infected women failing antiretroviral therapy with detectable viral load in both compartments, as well as from drug-naive subjects.

METHODS

Viral RNA was extracted from cervicovaginal lavage fluid, endocervical secretions collected by Sno-strips, and blood plasma. Population sequencing of HIV-1 pol was performed using cycle sequencing. Drug resistance mutations were analyzed. Phylogenies were constructed based on synonymous positions in the sequences.

RESULTS

Resistant virus was detected concordantly in blood and genital tract specimens, consistent with drug selection pressure in both compartments. However, drug-selected mutations often differed in each compartment, and phylogenetic analysis showed differences in virus lineage in these compartments, consistent with local replication in female genital tract. Viruses in cervicovaginal lavage and endocervical secretions were genetically distinguishable, suggesting that endocervix is not the only source of virus found in cervicovaginal lavage.

CONCLUSION

These data support the hypothesis that HIV replication is compartmentalized within the female genital tract during antiretroviral therapy, which has implications for pathogenesis and for epidemiologic surveillance of drug-resistant virus.

Incidence and impact of resistance against approved antiretroviral drugs

More than 15 antiretroviral drugs are now available for clinical use, and have led to significant reductions in morbidity and mortality for HIV infected individuals. Nevertheless, antiviral drug resistance emerges to all these drugs, which limits their benefit. This review addresses the biological basis of antiretroviral drug resistance, and the prevalence of specific drug resistance associated mutations in patients treated with the three currently available classes of agents, namely nucleoside analogue reverse transcriptase inhibitors, non nucleoside reverse transcriptase inhibitors and protease inhibitors. In addition, data on prevalence of HIV drug resistance in untreated individuals published to date are summarised, and the implications of potential transmission of drug resistant HIV is discussed.

HIV and germinal cells: how close an association?

Whether semen from someone who is HIV-positive can be prepared so that it is safe for insemination is a critical question particularly to couples in which the male is seropositive and the female is seronegative. It is reassuring that some investigators have reported great success in using sperm washing to dramatically reduce HIV levels in the ejaculate. Such reports suggest that if free virus and leukocytes in the seminal plasma are removed, the specimen may be safe for insemination. Whether the virus ever is associated with spermatozoa themselves is not fully understood. In situ hybridization as well as electron microscopic studies have suggested the presence of viral particles but whether these are preparation artifacts or evidence of viable viral DNA is not known. Studies of whether the virus is incorporated into developing spermatozoa or is shed in the reproductive tract will aid in the elucidation of sexual transmission of HIV.

Reducing the risk of perinatal HIV-1 transmission with zidovudine: results and implications of AIDS Clinical Trials Group protocol 076

This paper reviews the rationale for the AIDS Clinical Trials Group (ACTG) protocol 076 design, the study results and the implications of these results, including discussion of the US Public Health Service Task Force recommendations on the use of zidovudine to reduce perinatal transmission and for prenatal human immunodeficiency virus (HIV) counseling and testing.

Detection of human immunodeficiency virus type 1 and type 2 in the female genital tract: implications for the understanding of virus transmission

Risk of perinatal or female to male sexual transmission of HIV is likely to be associated with whether, and at what concentration, the virus is present in the cervical and vaginal secretions of the HIV-infected woman. Examining correlates of cervical and vaginal HIV shedding is, therefore, essential for the development of strategies to interrupt HIV transmission. This article presents the rationale for using detection of HIV in the female genital tract as a marker of infectivity, and briefly describes methods for detecting HIV-1 and HIV-2 in cervical or vaginal fluids. Findings from studies incorporating the measurement of HIV in the female genital tract are reviewed, placing particular emphasis on issues relevant to epidemiological studies of HIV transmission.

Antiretroviral drug resistance: mechanisms, pathogenesis, clinical significance

The contribution of HIV drug resistance to treatment failure, the relationship of drug resistance to pathogenesis and the impact of resistance in the role of the promising new class of protease inhibitors remain areas of active investigation. A more precise understanding of these aspects of antiretroviral drug resistance will permit the more effective use of available drugs and the design of new drugs and drug regimens.

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)