Prevention of rectal SHIV transmission in macaques by daily or intermittent prophylaxis with emtricitabine and tenofovir

BACKGROUND

In the absence of an effective vaccine, HIV continues to spread globally, emphasizing the need for novel strategies to limit its transmission. Pre-exposure prophylaxis (PrEP) with antiretroviral drugs could prove to be an effective intervention strategy if highly efficacious and cost-effective PrEP modalities are identified. We evaluated daily and intermittent PrEP regimens of increasing antiviral activity in a macaque model that closely resembles human transmission.

METHODS AND FINDINGS

We used a repeat-exposure macaque model with 14 weekly rectal virus challenges. Three drug treatments were given once daily, each to a different group of six rhesus macaques. Group 1 was treated subcutaneously with a human-equivalent dose of emtricitabine (FTC), group 2 received orally the human-equivalent dosing of both FTC and tenofovir-disoproxil fumarate (TDF), and group 3 received subcutaneously a similar dosing of FTC and a higher dose of tenofovir. A fourth group of six rhesus macaques (group 4) received intermittently a PrEP regimen similar to group 3 only 2 h before and 24 h after each weekly virus challenge. Results were compared to 18 control macaques that did not receive any drug treatment. The risk of infection in macaques treated in groups 1 and 2 was 3.8- and 7.8-fold lower than in untreated macaques (p = 0.02 and p = 0.008, respectively). All six macaques in group 3 were protected. Breakthrough infections had blunted acute viremias; drug resistance was seen in two of six animals. All six animals in group 4 that received intermittent PrEP were protected.

CONCLUSIONS

This model suggests that single drugs for daily PrEP can be protective but a combination of antiretroviral drugs may be required to increase the level of protection. Short but potent intermittent PrEP can provide protection comparable to that of daily PrEP in this SHIV/macaque model. These findings support PrEP trials for HIV prevention in humans and identify promising PrEP modalities.

Calpain regulates actin remodeling during cell spreading

Previous studies suggest that the Ca2+-dependent proteases, calpains, participate in remodeling of the actin cytoskeleton during wound healing and are active during cell migration. To directly test the role that calpains play in cell spreading, several NIH-3T3- derived clonal cell lines were isolated that overexpress the biological inhibitor of calpains, calpastatin. These cells stably overexpress calpastatin two- to eightfold relative to controls and differ from both parental and control cell lines in morphology, spreading, cytoskeletal structure, and biochemical characteristics. Morphologic characteristics of the mutant cells include failure to extend lamellipodia, as well as abnormal filopodia, extensions, and retractions. Whereas wild-type cells extend lamellae within 30 min after plating, all of the calpastatin-overexpressing cell lines fail to spread and assemble actin-rich processes. The cells genetically altered to overexpress calpastatin display decreased calpain activity as measured in situ or in vitro. The ERM protein ezrin, but not radixin or moesin, is markedly increased due to calpain inhibition. To confirm that inhibition of calpain activity is related to the defect in spreading, pharmacological inhibitors of calpain were also analyzed. The cell permeant inhibitors calpeptin and MDL 28, 170 cause immediate inhibition of spreading. Failure of the intimately related processes of filopodia formation and lamellar extension indicate that calpain is intimately involved in actin remodeling and cell spreading.

Nationwide survey of HTLV-I-associated myelopathy in Japan: association with blood transfusion

To study the epidemiology of human T-cell lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) in Japan, we conducted two nationwide surveys between October 1986 and March 1989. A total of 710 patients with HAM (definite HAM, 589; probable HAM, 121) were reported. Of the 589 patients with definite HAM, 69% were residents of the areas with the highest prevalence HTLV-I in Japan. To determine the importance of blood transfusion in the pathogenesis of HAM/TSP, we performed a case-control study in the Kagoshima district in southern Japan. Significantly more patients with HAM reported a history of blood transfusion (26/129, or 20%) than did subjects in a health survey of the general population (41/1,290, or 3%; odds ratio = 7.7, p less than 0.001) or than did hospitalized neurological patients (6/119, or 5%; odds ratio = 4.8, p less than 0.001). Furthermore, the cumulative percentages of the intervals between blood transfusion and the onset of the symptoms of HAM fit a lognormal curve, suggesting that transfusion was an important common exposure. Blood transfusion probably transmitted HTLV-I to the patients with transfusion-associated HAM because there was a significant decrease in the number of patients with the transfusion-associated HAM who received blood after implementation of nationwide screening of blood donors in 1986 (p = 0.004). In the first 2 years, screening the blood supply in Japan appears to have decreased the number of reported patients with HAM by 16%.

WHO Neuropsychiatric AIDS study, cross-sectional phase II. Neuropsychological and neurological findings

BACKGROUND

The neuropsychological and neurological complications of HIV-1 infection and AIDS were explored within the cross-sectional phase of the WHO Neuropsychiatric AIDS Study. Special attention was devoted to the controversial issue of the prevalence and clinical significance of subtle cognitive deficits in asymptomatic seropositive subjects.

METHODS

A neuropsychological test battery validated for cross-cultural use, a structured interview for the diagnosis of dementia, a rating scale of functioning in daily living activities, and a neurological module were administered to representative samples of seropositive subjects and to matched seronegative controls living in the five geographic areas predominantly affected by the HIV-1 epidemic. Data are available for five centers.

RESULTS

The prevalence of global neuropsychological impairment was significantly increased in asymptomatic seropositive subjects compared with controls in only two centers. A significant effect of education on neuropsychological performance was observed among asymptomatic seropositive individuals. In the two African centers, low-education, but not high-education, asymptomatic seropositive persons had an impaired performance. The frequency of impaired functioning in daily living activities and of neurologic abnormalities was higher in symptomatic, but not in asymptomatic, seropositive subjects compared with controls in all centers.

CONCLUSIONS

These data suggest that the risk of subtle cognitive deficits may be increased in asymptomatic stages of HIV-1 infection. However, these deficits are not associated with neurologic changes and do not seem to affect subjects' social functioning.

Creutzfeldt-Jakob disease probably acquired from a cadaveric dura mater graft. Case report

A case of Creutzfeldt-Jakob disease (CJD) is reported in a 28-year-old woman who had received a cadaveric dural graft 19 months earlier after resection of a cholesteatoma. The circumstances of the case point to the graft as the most likely source of the disease. Cadaveric dura should be added to the list of materials that may transmit CJD, and it must be very carefully screened if it is used at all for grafting. Autologous tissue should be considered whenever possible.

Efficacy of postexposure prophylaxis after intravaginal exposure of pig-tailed macaques to a human-derived retrovirus (human immunodeficiency virus type 2)

Postexposure prophylaxis (PEP) after intravaginal exposure to human immunodeficiency virus (HIV) was investigated using the HIV type 2 (HIV-2)/pig-tailed macaque transmission model. PEP for 28 days with the reverse transcriptase inhibitor (R)-9-(2-phosphonylmethoxypropyl)adenine (PMPA; tenofovir) was initiated 12 to 72 h following HIV-2 exposure. Systemic infection was not evident in the 12- and 36-h groups, as defined by plasma viremia, cell-associated provirus, antibody responses, and lymph node virus. Breakthrough infection in the 72-h group was detected at week 16 post-virus exposure. These results demonstrate for the first time using a vaginal transmission model that early intervention after high-risk sexual exposures may prevent infection.

Chemoprophylaxis with tenofovir disoproxil fumarate provided partial protection against infection with simian human immunodeficiency virus in macaques given multiple virus challenges

We examined the efficacy of tenofovir disoproxil fumarate (TDF) in blocking simian human immunodeficiency virus (SHIV) infection in Chinese rhesus macaques. Once weekly for 14 weeks or until a macaque became infected, 12 male macaques were inoculated intrarectally with amounts of SHIV(SF162P3) (10 median tissue culture infective doses; 3.8 x 10(5) virus particles) that were approximately 5-fold higher than the human immunodeficiency virus type 1 RNA levels noted in human semen during an acute infection. Of the 12 macaques, 4 received oral TDF daily, 4 received oral TDF once weekly, and 4 (control animals) received no TDF. The control animals became infected after receiving a median of 1.5 virus inoculations; macaques receiving TDF daily (1 macaque remained uninfected after 14 inoculations) and those receiving TDF weekly became infected after a median duration of 6.0 and 7.0 weeks, respectively. Although infection was delayed in treated macaques, compared with control macaques, the differences were not statistically significant (P=.315); however, the study was limited by the small numbers of animals evaluated and the variability in blood levels of TDF that resulted from oral dosing. These data demonstrate that treatment with oral TDF provided partial protection against SHIV infection but ultimately did not protect all TDF treated animals against multiple virus challenges.

WHO Neuropsychiatric AIDS study, cross-sectional phase I. Study design and psychiatric findings

BACKGROUND

Most available studies on the psychiatric, neuropsychological, and neurological complications of HIV-1 infection and AIDS have been conducted in Western countries, on samples of well-educated, mostly white, homosexual men. Concerns about generalizability of the results of those investigations prompted the WHO to implement the cross-cultural venture called WHO Neuropsychiatric AIDS study.

METHODS

This project aims to assess the prevalence and natural history of HIV-1-associated psychiatric, neuropsychological, and neurological abnormalities in representative subject samples enrolled in the five geographic areas predominantly affected by the HIV-1 epidemic. Assessment is made by a data collection instrument including six modules. The intercenter and intracenter reliability in the use of each module has been formally evaluated. The study consists of a cross-sectional phase and a longitudinal follow-up.

RESULTS

The cross-sectional phase was completed in five centers. This paper reports on the results of psychiatric assessment, which revealed a significantly higher prevalence of current mental disorders in symptomatic seropositive persons compared with seronegative controls among intravenous drug users in Bangkok and homosexuals/bisexuals in São Paulo. The mean global score on the Montgomery-Asberg Depression Rating Scale was significantly higher in symptomatic seropositive individuals than in matched seronegative controls in all centers.

CONCLUSIONS

These results suggest that the significance of the psychopathological complications of symptomatic HIV-1 infection may have been underestimated by previous studies conducted on self-selected samples of well-educated, middle-class, mostly white, homosexual men.

In Situ Vaccination with a TLR9 Agonist and Local Low-Dose Radiation Induces Systemic Responses in Untreated Indolent Lymphoma

This multicenter phase I/II clinical trial evaluated intratumoral SD-101, a TLR9 agonist, and low-dose radiation in patients with untreated indolent lymphoma. Twenty-nine enrolled patients received 4 Gy of radiation followed by 5 weekly intratumoral injections of SD-101 at a single tumor site. No treatment-related grade 4 or serious adverse events occurred. Nearly all patients had tumor reduction at their treated site. More importantly, 24 patients had tumor reduction at their nontreated sites, with 5 patients achieving a partial response and one achieving a complete response. Treatment-related increases of CD8+ and CD4+ effector T cells and decreases of T follicular helper and T regulatory cells (Treg) were observed in the tumor microenvironment. Low pretreatment levels of CD4+ Tregs, proliferating CD8+ T cells, and Granzyme B+ CD8+ T cells were associated with favorable outcomes. Intratumoral SD-101 in combination with low-dose radiation is well tolerated and results in regression of both treated and untreated sites of disease.Significance: In situ vaccination with the TLR9 agonist SD-101, along with low-dose radiation, was safe and induced systemic responses in patients with indolent lymphoma. Low levels of CD4+ Tregs, proliferating CD8+ T cells, and Granzyme B+ CD8+ T cells in the tumor microenvironment predicted favorable response to treatment. Cancer Discov; 8(10); 1258-69. ©2018 AACR. This article is highlighted in the In This Issue feature, p. 1195.

Equity in the finance of health care: some international comparisons

This paper presents the results of a ten-country comparative study of health care financing systems and their progressivity characteristics. It distinguishes between the tax-financed systems of Denmark, Portugal and the U.K., the social insurance systems of France, the Netherlands and Spain, and the predominantly private systems of Switzerland and the U.S. It concludes that tax-financed systems tend to be proportional or mildly progressive, that social insurance systems are regressive and that private systems are even more regressive. Out-of-pocket payments are in most countries an especially regressive means of raising health care revenues.

Estimated risk of HIV transmission by blood transfusion in Kenya

BACKGROUND

During the past decade, developing countries have received limited support for blood safety programmes. The Kenya Ministry of Health did a collaborative multicentre assessment to establish the risk of HIV transmission by transfusion in Kenya, to promote awareness of blood safety issues in this country with a mature HIV epidemic, and to identify methods to reduce the risk of HIV transmission by blood transfusion in Kenya.

METHODS

For 12 weeks, from April to July 1994, we collected information and blood samples from all blood donors, and pretransfusion samples were collected from all recipients in six government hospitals in Kenya. Blood donations were collected and screened for HIV according to standard practice in the hospital laboratories. Test results at a reference laboratory were compared with those of the hospital laboratories and risk of transfusion-associated HIV transmission was calculated.

FINDINGS

The prevalence of HIV among blood donors was 6.4% (120 of 1877) and varied by hospital (range 2-20%). HIV test results were available for 1290 donor-recipient pairs. Of these, 26 HIV-positive donations were given to HIV-negative patients. We estimate that 2.0% of transfusions transmitted HIV. Problems in the hospitals that contributed to transfusion risk included inconsistent refrigeration, data entry errors, equipment failure, and lack of a quality-assurance programme.

INTERPRETATION

A high proportion of blood transfusions transmitted HIV in this high-prevalence area of Africa, primarily because of erroneous laboratory practices. On the basis of these results, the Kenya Ministry of Health introduced a number of practical and inexpensive interventions to improve national blood safety.

Induction of a type 1 immune response to a recombinant antigen from Mycobacterium tuberculosis expressed in Mycobacterium vaccae

A 19-kDa lipoprotein from Mycobacterium tuberculosis was expressed as a recombinant antigen in the nonpathogenic mycobacterial host strain M. vaccae. Immunization of mice with the recombinant M. vaccae resulted in induction of a strong type 1 immune response to the 19-kDa antigen, characterized by immunoglobulin G2a (IgG2a) antibodies and gamma interferon (IFN-gamma) production by splenocytes. Immunization with the same antigen in incomplete Freund's adjuvant induced a strong IgG1 response with only low levels of IFN-gamma. Subsequent intravenous and aerosol challenges of immunized mice with virulent M. tuberculosis demonstrated no evidence of protection associated with the response to the 19-kDa antigen; in fact, the presence of the recombinant 19-kDa antigen abrogated the limited protection conferred by M. vaccae (vector control). The recombinant M. vaccae system is a convenient approach to induction of type 1 responses to M. tuberculosis antigens. However, the unexpected reduction in protective efficacy of M. vaccae expressing the 19-kDa antigen highlights the complexity of testing recombinant subunit vaccines and the need for a better understanding of the immune mechanisms required for effective vaccination against tuberculosis.

Mismatched wear couple zirconium oxide and aluminum oxide in total hip arthroplasty

A patient complained about a squeaking noise in his total hip arthroplasty. Clinical evaluation revealed good function, and there were no signs of loosening on the radiograph. Physiotherapy did not alter this phenomenon, and ultimately a revision was performed 42 months after the first surgery. The analysis of the retrievals revealed that a zirconium oxide ceramic head had been paired with a monolithic alumina ceramic cup. The cup showed large deviations from an ideal sphere but minor wear signs. The head exhibited heavy local damage in the articulation zone. This damage might have been caused by the observed unsatisfactory fit between cup and ball, resulting in high stress concentrations and increased wear of the zirconium head. The characteristics of the zirconium and aluminum ceramics pairing might have worsened the process. The combination of implants used in this retrieved wear couple was never approved. To prevent such problems, components of different manufacturers should never be mixed and matched unless explicitly stated.

Lipoprotein access to MHC class I presentation during infection of murine macrophages with live mycobacteria

Following uptake by macrophages, live mycobacteria initially reside within an immature phagosome that resists acidification and retains access to recycling endosomes. Glycolipids are exported from the mycobacterial phagosome and become available for immune recognition by CD1-restricted T cells. The aim of this study was to explore the possibility that lipoproteins might similarly escape from the phagosome and act as immune targets in cells infected with live mycobacteria. We have focused on a 19-kDa lipoprotein from Mycobacterium tuberculosis that was previously shown to be recognized by CD8(+) T cells. The 19-kDa Ag was found to traffic separately from live mycobacteria within infected macrophages by a pathway that was dependent on acylation of the protein. When expressed as a recombinant protein in rapid-growing mycobacteria, the 19-kDa Ag was able to deliver peptides for recognition by MHC class I-restricted T cells by a TAP-independent mechanism. Entry into the class I pathway was rapid, dependent on acylation, and could be blocked by killing the mycobacteria by heating before infection. Although the pattern of 19-kDa trafficking was similar with different mycobacterial species, preliminary experiments suggest that class I presentation is more efficient during infection with rapid-growing mycobacteria than with the slow-growing bacillus Calmette-Guérin vaccine strain.

Contribution of Th1 and Th2 cells to protection and pathology in experimental models of granulomatous lung disease

Mice that had received adoptive transfer of DO11.10 TCR transgenic T cells polarized toward a Th1 or a Th2 phenotype were challenged with Ag-coated beads or with recombinant Mycobacterium tuberculosis expressing the OVA determinant. The resulting bead-induced pulmonary granulomas reflected the phenotype of the adoptively transferred T cells, with the Th2 cells promoting a fibrotic reaction. Mice receiving Th1 cells mounted an epitope-specific protective response to challenge with recombinant M. tuberculosis. Th2 recipients were characterized by enhanced weight loss and lung fibrosis during acute high-dose infection. The combination of TCR transgenic T cells and epitope-tagged mycobacteria provides a novel experimental model for investigation of the pathogenesis of tuberculosis.

Thermal influences on nervous system function

The various effects of temperature change are only partially predictable. Temporal measures relevant to membrane activity, action potentials, synaptic transmission, and evoked potentials are all consistently increased with cooling and decreased by warming. However, the various measures of amplitude at different levels, and even within similar preparations, are contradictory: Some laboratories report increased amplitudes with cooling and others report decreased amplitudes under similar conditions. Emphasis is given to identifying factors that may resolve the differences. These include: (a) the rate of temperature change, (b) sites of cooling, stimulation and recording, (c) stimulus characteristics, and (d) fundamental differences in temperature sensitivities of different neural tissue. Other factors that may affect the ability to predict thermal influences on neural function from existing formulations are: relative ion permeabilities, metabolic ion pumps, the resting potential at the onset of cooling, and an animal's acclimated temperature at sacrifice.

Syphilis epidemics and human immunodeficiency virus (HIV) incidence among men who have sex with men in the United States: implications for HIV prevention

Recent outbreaks of syphilis among men who have sex with men (MSM) in major cities in the United States and reported increases in sexual risk behavior have raised concerns about potential increases in human immunodeficiency virus (HIV) transmission. The majority of MSM who have early syphilis are HIV infected; in preliminary studies, rates of recent HIV infection among them are also high. Data from San Francisco, Los Angeles, and Seattle-King County, however, suggest no temporal increases in HIV incidence among MSM seeking HIV testing at select large public sites during the syphilis outbreaks. Because most HIV incidence and behavioral data are from large metropolitan areas with large gay populations and well-established HIV epidemics, we do not know whether, nationally, incidence of HIV infection among MSM has been increasing, decreasing, or stable during syphilis outbreaks. Further studies of HIV incidence in larger and smaller cities with different maturities of HIV epidemic are warranted. Comprehensive and integrated HIV/STD prevention and control efforts are also needed to halt the spread of syphilis and reduce HIV transmission among gay and bisexual men.

Evaluation of a sensitive/less sensitive testing algorithm using the bioMérieux Vironostika-LS assay for detecting recent HIV-1 subtype B' or E infection in Thailand

The performance of the bioMérieux Vironostika-LS EIA (less sensitive enzyme immunoassay) was assessed to detect recent seroconversion among injecting drug users (IDUs) in Bangkok, Thailand who were infected with either HIV-1 subtypes B' or E (also known as circulating recombinant form CRF01_AE). To evaluate the Vironostika-LS EIA in non-B subtypes, we collected longitudinal specimens (n = 796) from 115 IDUs (subtype B' infection, n = 24; subtype E infection, n = 91). After testing HIV-positive specimens with the Vironostika-LS EIA, standardized optical densities (SODs) were calculated using median values to determine the window period, which is the time from seroconversion on a standard EIA to seroconversion on the Vironostika-LS EIA for a given SOD, for either subtype. For an SOD cutoff of 1.0, Vironostika-LS EIA results showed a mean window period of 239 days (95% confidence interval [95% CI], 208-287 days) for subtype B' and 356 days (95% CI, 318-402 days) for subtype E in Thailand. This outcome demonstrates that the Vironostika-LS EIA has significantly different performance characteristics in detecting recent seroconversion between different HIV-1 subtypes. Accurate identification of recent infection and estimation of incidence for HIV-1 strains other than North American subtype B, using the Vironostika-LS EIA, requires knowledge of specimen subtype and use of appropriate cutoffs and mean window periods.

Confirmation of an association between single nucleotide polymorphisms in the VDR gene with respiratory syncytial virus related disease in South African children

Respiratory syncytial virus is a leading cause of lower respiratory tract infection in infants. Disease severity has been linked to host immune responses and polymorphisms in genes associated with innate immunity. A large-scale genetics study of single nucleotide polymorphisms (SNPs) in children in the Netherlands identified SNPs in the vitamin D receptor (VDR) and JUN genes which have a strong association with an increased risk of developing bronchiolitis following the first respiratory syncytial virus (RSV) infection. The Toll-like receptor 4 (TLR4) gene has two SNPs which have been associated previously with RSV disease severity in various populations. The aim of this study was to determine if these SNPs may be associated with RSV disease in African children in South Africa. RSV patient (n = 296) and control (n = 113) groups were established (median ages: 3 and 3.5 months) and DNA extracted from the collected specimens. Real-time polymerase chain reaction using hydrolysis probes was used to screen for SNPs in the VDR (Thr1Meth; rs10735810), TLR4 (Asp299Gly; rs4986790 and Thr399Ile; rs4986791) and JUN (c.750G/A; rs11688) genes. Carriers of the VDR (Thr1Meth) SNP minor T allele were more prone to RSV disease than individuals in the control group. The TLR4 (Asp299Gly), TLR4 (Thr399Ile), and JUN (c.750G/A) SNPs showed no significant association with RSV disease. It is concluded that children carrying the minor T allele of the VDR (Thr1Meth) SNP may be predisposed to RSV disease, as this SNP was identified as a risk factor for severe RSV disease in South African children, confirming the findings in the Netherlands.

Linkage of myostatin pathway genes with knee strength in humans

This study was the first to explore the potential role of the myostatin (GDF8) pathway in relation to muscle strength and estimated muscle cross-sectional area in humans using linkage analysis with a candidate gene approach. In young male sibs (n = 329) 11 polymorphic markers in or near 10 candidate genes from the myostatin pathway were genotyped. Muscle mass was estimated by anthropometric measurements, and maximal knee strength was evaluated using isokinetic dynamometers (Cybex NORM). Single-point nonparametric variance components and linear quantitative trait locus regression linkage analysis methods were used. Linkage patterns were observed between knee extension and flexion peak torque with markers D2S118 (GDF8), D6S1051 (CDKN1A), and D11S4138 (MYOD1), and a maximum LOD score of 2.63 (P = 0.0002) was observed with D2S118. The ratios of peak torque over muscle and bone area of the midthigh of the lower contraction velocity (60 degrees/s) showed more frequently significant LOD scores than the torques at high velocity (240 degrees/s). Although myostatin is physiologically more related to muscle mass through possible effects of hyperplasia and hypertrophy than it is to strength, only two estimated muscle cross-sectional areas were marginally linked (LOD 1.06 and 1.07, P = 0.01) with marker D2S118 near GDF8 (2q32.2). The present results gave suggestive evidence that the myostatin pathway might be important for strength phenotypes, and GDF8, CDKN1A, and MYOD1 are potential candidate regions for a further and denser mapping with respect to these phenotypes.

HIV incidence in the United States, 1978-1999

CONTEXT

HIV incidence measurements, which reflect recent or current transmission, are valuable for monitoring the epidemic and evaluating prevention programs.

OBJECTIVES

To summarize HIV incidence patterns and trends in U.S. population groups.

DATA SOURCES

Publications in English from 1980 through mid-2000. STUDY SELECTION AND STATISTICAL METHODS: We searched the literature for reports of HIV incidence in the United States. Locally weighted scatterplot smoothing was used to generate smooth curves to estimate trends in incidence. Spearman rank correlation was used to estimate the correlation coefficient between prevalence and incidence.

DATA SYNTHESIS

In 74 eligible reports, HIV incidence varied widely (0.002-19.8 per 100 person-years [py]) depending on risk group. Among men who have sex with men (MSM), HIV incidence peaked in the early 1980s (5-20/100 py) and then declined but remained high during the 1990s (2-4/100 py). Among injection drug users (IDUs), incidence decreased since the mid-1980s but differed by geographic area; in the 1990s, incidence remained high in the East (1-3/100 py) but was lower in the West (<0.5/100 py). Throughout the late 1980s and 1990s, incidence was low and stable in broader populations (blood donors: <0.01/100 py; military personnel: 0.01-0.07/100 py). The correlation between HIV incidence and prevalence was strong in populations with a prevalence less than 1% (r = 0.94, p<.0001), moderate in populations with a prevalence from 1% to less than 10% (r = 0.57, p<.0001), and weak in populations with a prevalence at least 10% (r = 0.23, p=.09).

CONCLUSIONS

HIV prevention in the United States should continue to focus on MSM and IDUs. HIV incidence measurements should be considered for monitoring HIV transmission in MSM, IDUs, and other populations in which seroprevalence is high.

Glutamate neurotoxicity in the developing rat cochlea: physiological and morphological approaches

The neurotoxic effects of exogenous glutamate were studied in the rat cochlea. Glutamate-treated rats (4 g/kg/day i.p., postnatal days 2-9) exhibited electrophysiologically-measured elevations in high frequency thresholds usually associated with hair cell loss in the basal region of the cochlea. While surface preparations of the organ of Corti revealed no loss of hair cells, there was a dramatic and selective reduction of neurons in the basal, high frequency-related portion of the spiral ganglion. This sensitivity of developing spiral ganglion cells to the neurotoxicity of glutamate is consistent with the hypothesis that glutamate or a structurally related substance is a neurotransmitter at afferent synapses of cochlear hair cells.