Phyllis J. Kanki

Human Immunodeficiency Virus Type 1 Subtypes Differ in Disease Progression

At least 10 different genetic human immunodeficiency virus type 1 (HIV-1) subtypes (A-J) are responsible for the AIDS pandemic. Much of the understanding of HIV-1 disease progression derives from studies in the developed world where HIV infection is almost exclusively subtype B. This has led many to question whether the properties and consequences of HIV-1 infection can be generalized across subtypes that afflict the majority of infected persons in the developing world. From 1985 to 1997, a prospective study of registered female sex workers in Senegal tracked the introduction and spread of HIV-1 subtypes A, C, D, and G. In clinical follow-up, the AIDS-free survival curves differed by HIV-1 subtype. Women infected with a non-A subtype were 8 times more likely to develop AIDS than were those infected with subtype A (hazard ratio=8.23; P=. 009), the predominant subtype in the study. These data suggest that HIV-1 subtypes may differ in rates of progression to AIDS.

SEROLOGICAL EVIDENCE FOR VIRUS RELATED TO SIMIAN T-LYMPHOTROPIC RETROVIRUS III IN RESIDENTS OF WEST AFRICA

Serological evidence is presented here suggesting that a virus closely related to simian T-lymphotropic virus type III (STLV-III) infects man in Senegal, west Africa, a region where AIDS or AIDS-related diseases have not yet been observed. 25 sera from Senegalese individuals that were positive for antibodies to HTLV-III by enzyme-linked immunosorbent assay were examined for antibodies to HTLV-III and STLV-III by western blotting. Sera from individuals originating from regions where AIDS has been reported, such as the United States and Burundi (central Africa), reacted best with antigens of HTLV-III, although antibodies that cross-reacted with STLV-III p24 were also detected. Conversely, sera originating from Senegalese people reacted better with STLV-III than with HTLV-III. This was exemplified by the absence of reactivity in sera from both monkeys and Senegalese people to p41, an antigen regularly detected by sera from antibody positive individuals originating from central Africa or from the United States. In contrast sera from central Africa or the United States did not react with p32, the putative envelope transmembrane protein of STLV-III that is regularly detected by sera from both monkeys and antibody-positive Senegalese people. These results suggest that certain healthy Senegalese people have been exposed to a virus that is more closely related to STLV-III than to HTLV-III. The existence and study of such virus variants potentially with differential pathogenicity may provide important information for the development of an AIDS virus vaccine.

Lower Human Immunodeficiency Virus (HIV) Type 2 Viral Load Reflects the Difference in Pathogenicity of HIV-1 and HIV-2

Human immunodeficiency virus type 2 (HIV-2) is less pathogenic than HIV type 1 (HIV-1), but the mechanisms underlying this difference have not been defined. We developed an internally controlled quantitative reverse transcriptase-polymerase chain reaction to measure HIV-2 viral load and determined levels of plasma virus in a cohort of registered commercial sex workers in Dakar, Senegal. The assay has a lower limit of detection of 100 copies/mL and is linear over 4 logs. HIV-2 viral RNA was detectable in 56% of all samples tested; the median load was 141 copies/mL. Levels of viral RNA in the plasma were inversely related to CD4+ cell counts. HIV-2 and HIV-1 viral loads were compared among the seroincident women in the cohort; the median viral load was 30x lower in the HIV-2-infected women (P<.001, Wilcoxon rank sum test), irrespective of the length of time infected. This suggests that plasma viremia is linked to the differences in the pathogenicity of the 2 viruses.

EVIDENCE FOR HUMAN INFECTION WITH AN HTLV III/LAV-LIKE VIRUS IN CENTRAL AFRICA, 1959

An individual serum stored since 1959 from Central Africa has been demonstrated reactive against HTLV-III by ELISA Western blotting and by immunoprecipitation against HTLV-III as well as STLV-III. This serum was from a set of 1213 plasmas from various parts of Africa 818 dating from 1959. Because of the known high false positive rates on Abbott EIA in long-term frozen sera those found to be above the cutoff using the formula (mean of 3 negative serum controls plus 10% of the mean of 2 positive serum controls) x 3 were retested by immunofluorescence microscopy and Western blot enzymatic immunoassay. 1 serum taken from Central Africa in 1959 was positive by both tests. This plasma had an OD more than 7 x the cutoff value. It reacted strongly in immunofluorescence with infected H9 cells. Reactivity was detected by Western Blot against all major HTLV-III viral proteins and polypeptide 121. By immunoprecipitation it reacted with all major gag and env encoded proteins of HTLV-III and the gag encoded proteins of STLV-III-AGM. These results suggest that HTLV-III prevalence was low in 1959 but that at least 1 individual was exposed to a similar virus over 25 years ago in Central Africa.

Low Plasma Human Immunodeficiency Virus Type 2 Viral Load Is Independent of Proviral Load: Low Virus Production In Vivo

ABSTRACT Levels of virus in the plasma are closely related to the pathogenicity of human immunodeficiency virus type 1 (HIV-1). HIV-2 is much less pathogenic than HIV-1, and infection with HIV-2 leads to significantly lower plasma viral load. To identify the source of this difference, we measured both viral RNA and proviral DNA in matched samples from 34 HIV-2-infected individuals. Nearly half had undetectable viral RNA loads (<100 copies/ml), but levels of proviral DNA were relatively high and confirmed that quantities of provirus in HIV-1 and HIV-2 infection were similar. Overall, HIV-2 proviral DNA load did not correlate with viral RNA load, and higher viral RNA load was associated with increased production of plasma virus from the proviral template. These results suggest that low viral load in HIV-2 infection is due to decreased rates of viral production, rather than differences in target cell infectivity.

High Levels of Tumor Necrosis Factor—α and Interleukin-1β in Bacterial Vaginosis May Increase Susceptibility to Human Immunodeficiency Virus

Bacterial vaginosis (BV) was identified recently as a cofactor that promotes sexual transmission of human immunodeficiency virus (HIV). This study was done to determine if interleukin (IL)‐1b and tumor necrosis factor (TNF)‐a could be measured consistently in cervical secretions and if high levels of these cytokines were associated with BV. Secretions were obtained from 209 study subjects; most samples had detectable levels of TNF-a (84.2%) and IL-1b (79.8%). BV was detected in 53 (27.0%) of 196 women. High cytokine levels were significantly associated with BV (adjusted odds ratio [AOR], 4.17; 95% confidence interval [CI], 1.69‐10.30), oral contraceptive use (AOR, 2.78; 95% CI, 1.04‐7.48), and high leukocyte counts on vaginal smear (AOR, 1.18; 95% CI, 1.03‐1.36). Since these cytokines could up-regulate local HIV replication through activation of the long terminal repeat promoter region, the association of BV with high levels of IL-1b or TNF-a may partly explain the mechanism by which this risk factor enhances HIV transmission. Bacterial vaginosis (BV) is a common and recurrent disorder of the lower genital tract in women. It is characterized by the replacement of normal lactobacilli-predominant vaginal flora with Gardnerella vaginalis, anaerobic bacteria, and genital Mycoplasma organisms and/or is accompanied by increased vaginal pH [1, 2]. BV and abnormal vaginal flora have been found to be associated with human immunodeficiency virus (HIV) infection in various cross-sectional studies [3‐6]. More recently, in 2 separate longitudinal studies, BV and abnormal vaginal flora were associated with an increased risk of acquiring HIV [7, 8], which provides further argument for a causal relationship between disrupted vaginal flora and increased risk of HIV infection in women. However, the actual mechanism by which BV or the presence of abnormal vaginal flora could increase the susceptibility to HIV infection in women has not been defined clearly. Recently, a soluble activator of HIV transcription was found in genital secretions of women with vaginosis. The effect of this soluble factor was mediated through the activation of the NFkB enhancer in the long terminal repeat (LTR) promoter region of the virus [9‐11]. In addition, membrane components of BV

Immunologic Criteria Are Poor Predictors of Virologic Outcome: Implications for HIV Treatment Monitoring in Resource-Limited Settings

BACKGROUND Viral load (VL) quantification is considered essential for determining antiretroviral treatment (ART) success in resource-rich countries. However, it is not widely available in resource-limited settings where the burden of human immunodeficiency virus infection is greatest. In the absence of VL monitoring, switches to second-line ART are based on World Health Organization (WHO) clinical or immunologic failure criteria. METHODS We assessed the performance of CD4 cell criteria to predict virologic outcomes in a large ART program in Nigeria. Laboratory monitoring consists of CD4 cell count and VL at baseline, then every 6 months. Failure was defined as 2 consecutive VLs >1000 copies/mL after at least 6 months of ART. Virologic outcomes were compared with the 3 WHO-defined immunologic failure criteria. RESULTS A total of 9690 patients were included in the analysis (median follow-up, 33.2 months). A total of 1225 patients experienced failure by both immunologic and virologic criteria, 872 by virologic criteria only, and 1897 by immunologic criteria only. The sensitivity of CD4 cell criteria to detect viral failure was 58%, specificity was 75%, and the positive-predictive value was 39%. For patients with both virologic and immunologic failure, VL criteria identified failure significantly earlier than CD4 cell criteria (median, 10.4 vs 15.6 months; P < .0001). CONCLUSIONS Because of the low sensitivity of immunologic criteria, a substantial number of failures are missed, potentially resulting in accumulation of resistance mutations. In addition, specificity and predictive values are low, which may result in large numbers of unnecessary ART switches. Monitoring solely by immunologic criteria may result in increased costs because of excess switches to more expensive ART and development of drug-resistant virus.

Impact of Hepatitis B Virus Infection on Human Immunodeficiency Virus Response to Antiretroviral Therapy in Nigeria

BACKGROUND As highly active antiretroviral therapy (ART) is introduced into areas of the world in which hepatitis B virus (HBV) infection is highly endemic, it is important to determine the influence of HBV on persons with human immunodeficiency virus (HIV) and HBV coinfection who are receiving ART. METHODS We studied 1564 HIV-infected patients in Jos, Nigeria, who initiated ART. Participants with HIV-HBV coinfection had hepatitis B e antigen (HBeAg) and HBV DNA status determined. CD4+ T cell count and HIV load at ART initiation were compared between individuals with HIV monoinfection and those with HIV-HBV coinfection with use of univariate methods. Regression analyses were used to determine if HBeAg status or HBV DNA at ART initiation were associated with baseline HIV parameters or ART response. RESULTS The median CD4+ T cell count of the 262 participants with HIV-HBV coinfection (16.7%) was 107 cells/mL, compared with 130 cells/mL for participants with HIV monoinfection at ART initiation (P = .001). Participants with HIV-HBV coinfection also had higher HIV loads than did patients with HIV monoinfection (4.96 vs 4.75 log10 copies/mL; p = .02 ). Higher HBV DNA and detectable HBeAg levels were independently associated with lower CD4+ T cell counts at ART initiation but not with higher HIV loads. In a multivariable model, HBeAg-positive patients were less likely than HBeAg-negative patients to suppress HIV replication to <or= 400 copies/mL (odds ratio, 0.54; P = .03 ) at 24 weeks, but they had similar CD4+ T cell increases. At 48 weeks, there was no significant effect of HBeAg status on ART response. CONCLUSIONS Among HIV-infected Nigerian individuals, HBV coinfection, especially among those with high levels of HBV replication, was associated with lower CD4+ T cell counts at ART initiation, independent of HIV RNA level. Patients with HBeAg-positive status had a slower virological response to ART, compared with HBeAg-negative patients. Further work is needed to understand the effects of HBV on CD4+ T cells.

Direct Evidence of Lower Viral Replication Rates In Vivo in Human Immunodeficiency Virus Type 2 (HIV-2) Infection than in HIV-1 Infection

ABSTRACT Studies have shown that human immunodeficiency virus type 2 (HIV-2) is less pathogenic than HIV-1, with a lower rate of disease progression. Similarly, plasma viral loads are lower in HIV-2 infection, suggesting that HIV-2 replication is restricted in vivo in comparison to that of HIV-1. However, to date, in vivo studies characterizing replication intermediates in the viral life cycle of HIV-2 have been limited. In order to test the hypothesis that HIV-2 has a lower replication rate in vivo than HIV-1 does, we quantified total viral DNA, integrated proviral DNA, cell-associated viral mRNA, and plasma viral loads in peripheral blood samples from groups of therapy-naïve HIV-1-infected (n = 21) and HIV-2-infected (n = 18) individuals from Dakar, Senegal, with CD4+ T-cell counts of >200/μl. Consistent with our previous findings, total viral DNA loads were similar between HIV-1 and HIV-2 and plasma viral loads were higher among HIV-1-infected individuals. Proportions of DNA in the integrated form were also similar between these viruses. In contrast, levels of viral mRNA were lower in HIV-2 infection. Our study indicates that HIV-2 is able to establish a stable, integrated proviral infection in vivo, but that accumulation of viral mRNA is attenuated in HIV-2 infection relative to that in HIV-1 infection. The differences in viral mRNA are consistent with the differences in plasma viral loads between HIV-1 and HIV-2 and suggest that lower plasma viral loads, and possibly the attenuated pathogenesis of HIV-2, can be explained by lower rates of viral replication in vivo.

Antibodies to simian T-lymphotropic retrovirus type III in African green monkeys and recognition of STLV-III viral proteins by AIDS and related sera.

It has been theorized that the agent responsible for AIDS originated in Africa. An HTLV-I related virus found in African primates has in vitro characteristics and genetic structure similar to that of HTLV-I virus found in man and has been associated with lymphoma in 3 macaque species A retrovirus similar to HTLV-III has also been isolated from diseased macaques some of whom had immune system disease. To test the possibility that HTLV-III virus might have been transmitted to man via primates evidence was sought for an HTLV-related virus in primates from areas of Africa associated with AIDS in man. Sera were collected and studied from 3 central African primates--green monkeys chimpanzees and baboons. Human sera positive for HTLV-III were also collected from persons suffering from AIDS and AIDS Related Complex and from healthy homosexuals. Sera were prescreened for antibodies to STLV-III by membrane immunofluorescence. The 160 120 55 viral antigens of STLV- III were immunoprecipitated by both MIF-positive macaque sera and by HTLV-III positive sera from patients with AIDS and AIDS Related Complex. MIF-positive green monkey sera recognized STLV-III proteins but chimpanzee and baboon MIF-negative sera did not. 42% of healthy green monkeys had antibodies to STLV-III. None of the baboons and chimpanzees was seropositive. We suggest that STLV-III of African green monkeys may have been transmitted to man coincident with the recognition of AIDS in central Africa.