Human immunodeficiency virus type 1 infection in homosexual men who remain seronegative for prolonged periods

Quantitative analysis of human immunodeficiency virus type-1 DNA in asymptomatic carriers using the polymerase chain reaction

A method for detecting human immunodeficiency virus type 1 (HIV-1) provirus DNA in lymphocytes with improved sensitivity and reproducibility was developed using the polymerase chain reaction (PCR). Amplified HIV-1 DNA was hybridized with a 32P-labeled probe and quantitated with a beta-scanner after electrophoresis. A linear relationship was obtained between the common logarithms of the counts detected and the number of HIV-1 DNA copies applied to the PCR. Detectability was from 3 copies/10(5) lymphocytes, and linearity was maintained from 10 to 10(3) copies. HIV-1 DNA was detected in all 9 asymptomatic carriers tested (18 to 2,857 copies/10(5) CD4+ T lymphocytes). The viral burden was inversely related to the CD4+ lymphocyte count, suggesting that quantitation of provirus levels may serve as a predictor of progress in early HIV infection.

Effects of primer-template mismatches on the polymerase chain reaction: human immunodeficiency virus type 1 model studies

We investigated the effects of various primer-template mismatches on DNA amplification of an HIV-1 gag region by the polymerase chain reaction (PCR). Single internal mismatches had no significant effect on PCR product yield while those at the 3'-terminal base had varied effects. A:G, G:A, and C:C mismatches reduced overall PCR product yield about 100-fold, A:A mismatches about 20-fold. All other 3'-terminal mismatches were efficiently amplified, although the G:G mismatches appeared to be more sensitive to sequence context and dNTP concentrations than other mismatches. It should be noted that mismatches of T with either G, C, or T had a minimal effect on PCR product yield. Double mismatches within the last four bases of a primer-template duplex where one of the mismatches is at the 3' terminal nucleotide, in general, reduced PCR product yield dramatically. The presence of a mismatched T at the 3'-terminus, however, allowed significant amplification even when coupled with an adjacent mismatch. Furthermore, even two mismatched Ts at the 3'-terminus allowed efficient amplification.

Immunological features of human immunodeficiency virus disease

Infection with the human immunodeficiency viruses results in a profound immunosuppression responsible for most of the clinical features of AIDS. The virus devastates the immune system because its main target is the T4 lymphocyte, which is the key component for generating and regulating the immune response. The cellular receptor for HIV, the membrane glycoprotein CD4, is found mainly on the surface of this major subpopulation of T lymphocytes and also on many other cell types such as those of the monocyte/macrophage series. HIV can destroy CD4 cells by direct virus cytotoxicity and indirectly through the host response against HIV-infected cells or gp120-targeted cells. Cells of the macrophage lineage are generally not destroyed but serve as a reservoir of virus. HIV also causes functional impairment in T cells, B cells and monocytes. The virus can exist in latent or chronic form. The mechanisms of cellular destruction, viral persistence and conversion to a productive infection are being studied vigorously. Host factors that may affect clinical outcome and immunological markers that may predict progression of HIV disease are presently delineated. Prolonged serological latency may follow infection with HIV. Protective humoral and cell-mediated immune responses to HIV are either poor or not sustained. Recent results on HIV-specific cytotoxic T lymphocytes are of great interest. These cytotoxic cells, particularly those directed to gp120 targets, probably contribute to cellular damage. A central question regarding immunity to HIV is its beneficial versus deleterious effects, particularly in regard to the eventual development of an AIDS vaccine.

Epidemiology and clinical picture of human immunodeficiency virus type 1 infection and the acquired immune deficiency syndrome

Human Immunodeficiency Virus Type 1 (HIV-1) infection which causes the terminal Acquired Immune Deficiency Syndrome (AIDS) is one of the major new pandemics of this millenium. This infection is believed to be a zoonosis which achieved sustained transmission among humans because of recent increases in sexual promiscuity and needle-sharing drug use. Although the HIV-1 epidemic is of relatively recent onset, its modes of transmission have been clearly defined: sexual relations, blood injection, and childbirth. Other possible transmission methods such as non-sexual social interaction and insects have been explicitly excluded. Susceptibility is increased by genital ulcers and lack of male circumcision but probably not by genetic factors or female circumcision. Transmissibility is also increased by genital ulcers and, more importantly, by the stage of disease. Progression by stages to fatal diseases will probably occur in most, if not all, infected individuals, usually within a decade. While HIV-1 has a direct effect on the intestinal track and the central nervous system, its primary effect is suppression of the immune system resulting in overwhelming secondary infections and, less clearly, cancers. Human Immunodeficiency Virus Type 1 infection is incurable and is likely to remain so for the foreseeable future. Although life-prolonging treatments have been developed, a vaccine will likely not be available in the foreseeable future. Like most previous new epidemic diseases, HIV-1 infection is being and will continue to be modified by changing human behavior patterns.

The HIV-infected health care professional: employment policies and public health

In July 1990, the federal Centers for Disease Control (CDC) reported the first case of possible transmission of the Human Immunodeficiency Virus (HIV) to a patient from an HIV-infected health care worker. The transmission may have occurred during an invasive dental procedure performed on her by a dentist who had AIDS, and in January 1991, the CDC reported possible HIV transmission during dental procedures to two other patients of the same dentist. Further, the recent revelation that a respected surgeon at a major medical center performed many surgical procedures while infected with HIV created substantial public concern. These cases call into question the prudence of allowing infected workers to continue performing medical and dental procedures that involve some risk, however slight, of transmitting HIV infection to patients. Whether HIV-infected workers should be excluded from practice of their profession because of a remote risk to patients relates directly to levels of tolerable risk in health care delivery and in social policy.

Current status of clinical laboratory tests for the human immunodeficiency virus

The predictive values of positive and negative test results for human immunodeficiency virus (HIV) antibody are extremely high in laboratories that have good quality control and high performance standards and use licensed FDA-approved enzyme immunoassay (EIA) and Western blot standardized tests. With a carefully designed protocol, the false-positive rate of combined EIA and Western blot has been reported to be as low as 1 in 10(5). When results of HIV confirmatory antibody tests are indeterminate, other tests such as culture and nucleotide probe methods for HIV DNA or RNA may help resolve false-reactive screening EIA tests. Improvements are constantly in progress for HIV laboratory tests with the use of recombinant DNA-derived antigens and synthetic polypeptides. With the use of new-generation synthetic polypeptide antigens, specific assays to identify HIV-1 and HIV-2 have been developed. Recently, assays for the HIV regulatory gene products have been studied for their predictive potential. Antibodies to nef protein, a regulator of HIV-1 replication, may be an early indicator of HIV infection.

Exposure of patients to human immunodeficiency virus through the transfusion of blood components that test antibody-negative

The risk of transmission of the human immunodeficiency virus to recipients of blood transfusions exists chiefly during the period between the time a donor is infected and the time he or she has a positive blood test for HIV antibodies. Estimating the chance that blood will be donated during this period is an effective way to define the risk of HIV infection from transfusion. Using this approach, and employing data from over 17 million American Red Cross blood donations, we estimate that during 1987 the most likely number of units of blood infected with undetected HIV that were transfused was 131 (range, 67 to 227). For a patient, the odds of contracting HIV infection were 1:153,000 per unit transfused. A patient who received the average transfusion (5.4 units) had odds of 1:28,000. The risk has been decreasing by more than 30 percent a year. We estimate that donor-recruitment practices plus careful education and screening are eliminating 49 of every 50 donors likely to be HIV-positive and that testing is 92 to 97 percent effective, for a combined effectiveness of 99.9 percent. The risk of undetected infectious units can probably be further reduced by transfusing fewer units and units from fewer donors, recruiting more women and fewer men as new donors, and encouraging more frequent donations from donors who have been tested repeatedly.

Detection of HIV genome in HIV antibody negative men

The presence of the human immunodeficiency virus (HIV) genome was investigated by applying in situ hybridisation techniques to peripheral blood mononuclear cells (PBMCs). Twenty asymptomatic anti-HIV seronegative homosexual men were the subjects of our study. The cells were hybridised with: (1) an SP 64 plasmid containing the nine-kilobase SstI-SstI viral insert from the lambda BH 10 recombinant clone; this can recognise both viral RNA and proviral DNA, and (2) with a pA01 plasmid containing HBV DNA genome. The DNA probes were modified by inserting an antigenic sulfone group in the cytosine moieties and the visualisation was performed by a double antibody immunohistochemical reaction. In two subjects both the HIV genome and HBV DNA were detected whereas another two subjects were positive for HBV DNA and for the HIV genome respectively. Thus people who are seronegative for anti-HIV specific antibodies may be infected with HIV.

The argument for HIV-antibody testing in chemical dependence treatment programs

Controversy surrounds the issue of human immunodeficiency virus (HIV) antibody testing in chemically dependent patients. However, HIV testing can be clinically and therapeutically useful in chemical dependence treatment programs. Prerequisites for HIV testing include: staff education, high-quality pre- and posttest counseling for patients, assurance of confidentiality of results, and the use of accurate screening and confirmatory tests. Reasons to offer voluntary HIV testing in chemical dependence treatment programs include: appropriate medical evaluation and treatment, prevention of the spread of HIV infection, and support for working through the crisis of a positive diagnosis. Voluntary informed consent should be obtained prior to HIV testing; involuntary testing and mass screening are not justified. Testing decisions should be individualized, with the focus on the patient's participation based on treatment- and health-related decisions.

The argument against HIV-antibody testing in chemical dependence treatment programs

As HIV continues to spread among chemically dependent populations, chemical dependence treatment programs are beginning to address the issue of routine HIV-antibody testing. While there are many rationales given for testing, only two are deemed acceptable in chemical dependence treatment programs: to permit medical personnel to institute therapy promptly; and to assist in behavior modification (risk reduction). Early intervention is deemed premature because federal regulations disallow the use of drugs, such as AZT, until T-4 cell counts are lower than 200. In addition, many clients may not stay in treatment long enough to institute therapy and ongoing treatment. Many experimental drug trials exclude drug addicts and women. Chemically dependent individuals have neither the knowledge nor the funds to obtain experimental drugs from other countries. Moreover, current protocols of HIV test-related counseling are insufficient to assist clients in changing their high-risk behaviors. Many chemically dependent clients who receive a positive test result relapse to drug abuse or act out sexually; many who receive a negative test result deny the need to change behaviors to avoid infection. Additionally, test result validity and discrimination are presented as deterrents to testing. In long-term treatment situations, where HIV/AIDS education and counseling are done over time as part of treatment and where support systems are in place, HIV testing can be an aid in behavior change.

Duration of human immunodeficiency virus infection before detection of antibody

To estimate the duration and frequency of the period of HIV infection without detectable antibody, modelling techniques were applied to results of detection of HIV DNA by means of the polymerase chain reaction (PCR) and to data from cases in published reports. PCR was carried out with gag and env region primers on samples from 27 homosexual and 12 haemophilic men for whom stored samples were available from before and after seroconversion; serum was also tested for p24 antigen by antigen-capture enzyme immunoassay. HIV DNA was detectable before seroconversion in 4 men; in all 4 PCR was positive only in the seronegative sample taken closest to the time of seroconversion. In 3 men antigen was detected before seroconversion; in each case HIV DNA was also detected. By a Markov model, the time from infection with HIV (as assessed by detection of HIV DNA) to first detection of HIV antibody was estimated to be 2.4 (SE 2.1) months for the median individual. Modelling of cases of HIV infection with known exposure in published reports gave a median estimate of 2.1 (0.1) months from exposure to antibody detection, and 95% of cases would be expected to seroconvert within 5.8 (0.6) months. HIV infection for longer than 6 months without detectable antibody seems uncommon.