HIV-1 variants: yet another challenge to public health

Surveillance of the genetic variation in incident HIV, HCV, and HBV infections in blood and plasma donors: implications for blood safety, diagnostics, treatment, and molecular epidemiology

Surveillance for molecular variants in blood donors is vital to assuring that blood screening and supplemental assays are sensitive to circulating strains of blood-borne viruses. Blood screening and diagnostic assays licensed in the United States are largely based on prototype viral strains. Documentation of divergent viral strains in the donor pool can lead to accelerated development and licensure of robust serologic and nucleic acid amplification (NAT) assays for donor screening and diagnostic applications. In addition, surveillance for viral variants among donors has implications for assessing the prevalence of drug and vaccine escape mutants and for detecting and monitoring rare variants that may be newly introduced or increasing in the United States donor population. Combined NAT and serologic screening, supplemented by novel serologic testing strategies, can be used to identify donors with incident infections, which are of particular interest with respect to blood safety and public health implications. A systematic program is proposed for the genetic characterization of viral genomes in donors with incident HIV, HCV, or HBV infections.

Clinical disease associated with HIV-1 subtype B' and E infection among 2104 patients in Thailand

BACKGROUND

Two HIV-1 envelope subtypes have accounted for virtually all infections in Thailand: subtype B' (Thai B), found mainly in injection drug users (IDU), and subtype E, found in over 90% of sexually infected persons and an increasing proportion of IDU in recent years. It remains unclear whether there are differences in pathogenesis associated with these HIV-1 subtypes.

METHODS

From November 1993 to June 1996, demographic, risk, clinical, and laboratory data were collected by enhanced surveillance from HIV-infected inpatients (> or =14 years) at an infectious disease hospital near Bangkok. HIV-1 subtype was determined by V3-loop peptide enzyme immunoassay (EIA). Because of confounding, multivariate analyses were stratified by risk category and controlled for sex and age.

RESULTS

The infecting HIV-1 subtype was determined for 2104 (94.9%) of 2217 HIV-infected patients with complete data: 284 (13.5%) were subtype B', 1820 (86.5%) were E. Specimens from 113 (5.1%) patients were non-reactive or dually reactive on peptide EIA and were excluded. Among IDU, 199 (67.2%) had subtype B', and 97 (32.7%) had E. IDU accounted for 70.1% (199/284) of patients with subtype B' and 5.3% (97/1820) of those with E. Patients infected with HIV-1 subtypes B' or E had similar spectrums of opportunistic infections (OI), levels of immunosuppression, and in-hospital mortality rates. Of patients who did not inject drugs, more patients infected with subtype E had extrapulmonary cryptococcosis than those with subtype B' (adjusted odds ratio, 2.6; 95% confidence interval, 1.28-5.37).

CONCLUSION

HIV-1 subtypes B' and E seem to be associated with similar degrees of immunosuppression and, with one exception, with similar OI patterns. These data do not suggest an association between HIV-1 subtype and differences in pathogenicity.

Infection with HIV-1 group O

The author presents the case history of the first patient with HIV-1 group O reported in the United States. The various human retroviruses and their clinical syndromes are described and the increasing diversity of HIV-1 strains and their spread are documented. The discovery of the divergent group O and its spread from endemic areas are discussed. The clinician is alerted to the pitfalls of laboratory diagnosis and is advised to seek special studies when clinical findings and epidemiologic history suggest the possibility of HIV infection.

Human immunodeficiency virus (HIV) antibodies detected by new assays that are enhanced for HIV-1 subtype O

BACKGROUND

Human immunodeficiency virus type 1 (HIV-1) subtype O infections are not reliably detected by commonly used anti-HIV-1/2 screening assays. Therefore, anti-HIV-1/2 assays have been modified to increase their sensitivity in detecting antibodies to HIV-1 subtype O.

STUDY DESIGN AND METHODS

Two new anti-HIV-1/2 enzyme-linked immunosorbent assays (ELISAs) (Abbott Plus and Ortho Enhanced) were compared with a currently used anti-HIV-1/2 ELISA (Abbott Recombinant) in various serum panels: 91 Western blot-confirmed anti-HIV-1-positive samples, 20 samples from Western blot-confirmed HIV-1-infected patients in log3 serial dilutions, and 1463 samples from consecutive, volunteer, nonremunerated blood donors.

RESULTS

Among 91 anti-HIV-1 Western blot-positive samples, 2 (2.2%) were missed by the Abbott Recombinant ELISA, but all 91 were detected by the Abbott Plus and Ortho Enhanced ELISAs. In contrast, two discrepant samples were found to react in viral lysate-based assays. In serial dilutions, Ortho Enhanced ELISA was significantly less sensitive than the Abbott Recombinant and Abbott Plus ELISAs, with the latter two being of comparable sensitivity. The specificities of Abbott Recombinant, Abbott Plus, and Ortho Enhanced ELISAs in 1463 blood donors were 100, 99.93, and 99.86 percent, respectively. Routine testing of 29,102 donations with the enhanced Abbott Plus ELISA revealed a specificity of 99.93 percent.

CONCLUSION

Two Western blot-confirmed anti-HIV-1-positive samples were missed by the Abbott Recombinant ELISA but detected by the Abbott Plus and Ortho Enhanced ELISAs. The analytic sensitivity of the Ortho Enhanced ELISA was inferior to that of both Abbott ELISAs. The specificities of the Abbott Recombinant, Abbott Plus, and Ortho Enhanced ELISAs were comparable.

The human immunodeficiency virus

There indeed seems to be a new mood of optimism in researchers and clinicians studying HIVs and patients infected with these viruses. A new understanding of the virology, biology, and therapy of HIV-1 includes the following: (1) The level of HIV-1 viremia, as measured by the HIV-1 plasma RNA, is a critical determinant of the time to development of AIDS and death. (2) Lessons from nonprogressors or long-term survivors, who do not develop AIDS or immune impairment despite their long-term infection, show clearly that the HIV-1 replication is significantly lower (4 to 20 times) than in people with progressive disease, and there is a vigorous and specific immune response against HIV-1. (3) Reducing viremia with antiretroviral drugs can delay the onset of AIDS and prolong survival. (4) Combination drug therapies, including an RT inhibitor and a PR inhibitor, can lower viremia to undetectable levels and delay the development of drug-resistant HIV-1. (5) HIV-1 subgroups have marked geographically distinct distributions, which may specify the routes of infection in different populations at risk.

Licencing of diagnostic HIV kits-to keep a sensible standpoint in an area of permanent revolution

BACKGROUND

In vitro diagnostic medical devices or 'test kits' are important tools for diagnosing illnesses and monitoring the patients' state of health or the effects of medical treatment. It is in the public interest that commercial kits are of high quality.

OBJECTIVES

To review the current situation of kit evaluation in Europe and to establish practical and sensible criteria for kit evaluation in general, based on the Swiss experience with the licencing of kits for the detection of human immunodeficiency virus (HIV) infection. Kit evaluation should provide the user with a selection of sufficiently good products. In addition, it should be simple and not require rare patient materials. Also of importance is that all manufacturers are treated equally.

METHODS

The evaluation criteria depend on the legal situation, the intended use of the test, the state of the art and the graveness of false-negative or -positive results. In addition to diagnostic sensitivity and specificity, other important considerations include the quality control by the manufacturer, kit presentation, intra- and inter-lot reproducibility and how a test fits into a country's adopted testing system.

RESULTS

The above goals can be achieved by setting minimal performance standards, preferably in the form of a lower limit of the confidence interval for the sensitivity/specificity that has been observed in the test's field evaluation. The better the test, the fewer samples have to be studied. For tests with no false results observed during field trials, the minimum sample number necessary for demonstration of a sensitivity or specificity >/= 99% is about 400, while it is 700 for a >/= 99.5% demonstration. Further insight into sensitivity is provided by results from well described and frequently used commercial seroconversion panels. This represents a dynamic tool that readily identifies insensitive kits that have become technically obsolete. Specificity assessment should not only involve blood donors, but also appropriate clinical controls. It is clear that the test design has an important bearing with respect to sensitivity and specificity. There are inherent advantages and disadvantages of indirect binding assays, capture assays and double antigen sandwich assays. Positive or negative results with these different test formats may not carry exactly the same message.

CONCLUSION

Efficient kit evaluation does not require tens of thousands of samples but can be performed with relatively little disbursement on materials and manpower.

Sensitive detection and quantification of particle-associated reverse transcriptase in plasma of HIV-1-infected individuals by the product-enhanced reverse transcriptase (PERT) assay

Tests for the enzyme reverse transcriptase (RT) should permit the detection of all infectious retroviruses, provided that these are present as extracellular particles. The capability of a new procedure, named product-enhanced reverse transcriptase (PERT) assay, to detect HIV-1 in fresh human plasma was compared with that of the polymerase chain reaction (PCR) for viral RNA. Both procedures had identical dilution endpoints corresponding to 10(2) particles/ml. All 30 samples from HIV-1 positive patients at different stages contained RT activity whose level was significantly correlated with viral RNA and corresponded to 553-417,000 particles/ml. In HIV-1 low titer performance and seroconversion panels, the PERT assay detected more positives than PCR for viral RNA. Three of 160 blood donors exhibited elevated RT activity, indicating a prevalence of 1.9% (95% CI 0.4-5.3%). One positive donor, with laboratory parameters suggesting a mild chronic liver impairment, exhibited RT activity comparable to that of HIV positives, but was consistently negative by various tests for hepatitis viruses, cytomegalovirus, the HIVs and HTLVs. The results suggest that the PERT assay is more sensitive for detection of HIV-1 contamination of plasma than RNA PCR. However, it is not affected adversely by viral sequence variability, and may therefore, also detect HIV-1 subtype O, and additional retroviruses as yet undetectable by PCR.

The epidemiology of HIV infection and AIDS in Africa

Only 10 years after it was first recognized in Africa, HIV infection is already the leading cause of adult death in many cities of the continent and has increased childhood mortality. This article reviews critical aspects of the dynamics of this epidemic, including routes of transmission, factors influencing the rate of transmission and strategies to combat this disaster.