Christopher D. Pilcher

Brief but Efficient: Acute HIV Infection and the Sexual Transmission of HIV

BACKGROUND We examined whether viral dynamics in the genital tract during the natural history of acute human immunodeficiency virus type 1 (HIV-1) infection could explain efficient heterosexual transmission of HIV. METHODS We measured HIV-1 concentration in blood and semen samples from patients with acute and long-term HIV-1 infection. We explored the effect of changes in viral dynamics in semen on the probability of transmission per coital act, using a probabilistic model published elsewhere. RESULTS Considered over time from infection, semen HIV-1 concentrations, in men with acute infection, increase and decrease in approximate parallel with changes occurring in blood. Modeling suggests that these acute dynamics alone are sufficient to increase probability of heterosexual transmission by 8-10-fold between peak (day 20 after infection, based on the model) and virologic set points (day 54 and later after infection). Depending on the frequency of coitus, men with average semen HIV-1 loads and without sexually transmitted diseases (STDs) would be expected to infect 7%-24% of susceptible female sex partners during the first 2 months of infection. The predicted infection rate would be much higher when either partner has an STD. CONCLUSIONS Empirical biological data strongly support the hypothesis that sexual transmission by acutely infected individuals has a disproportionate effect on the spread of HIV-1 infection. Acute hyperinfectiousness may, in part, explain the current pandemic in heterosexual individuals.

Amplified transmission of HIV-1: comparison of HIV-1 concentrations in semen and blood during acute and chronic infection

Objectives:This study was conducted to compare viral dynamics in blood and semen between subjects with antibody negative, acute HIV-1 infection and other subjects with later stages of infection. Design:A prospective cohort study was embedded within a cross-sectional study of HIV screening in a Lilongwe, Malawi STD clinic. Methods:Blood samples from HIV antibody negative or indeterminate volunteers were used to detect HIV RNA in plasma using a pooling strategy. Blood and seminal plasma HIV-1 RNA concentrations were measured over 16 weeks. Results:Sixteen men with acute HIV infection and 25 men with chronic HIV infection were studied. Blood viral load in subjects with acute HIV infection was highest about 17 days after infection (mean ± SE, 6.9 ± 0.5 log10 copies/ml), while semen viral load peaked about 30 days after infection (4.5 ± 0.4 log10 copies/ml). Semen viral load declined by 1.7 log10 to a nadir by week 10 of HIV infection. Semen and blood viral loads were more stable in chronically infected subjects over 16 weeks. Higher semen levels of HIV RNA were noted in subjects with low CD4 cell counts. Conclusions:These results provide a biological explanation for reported increases in HIV transmission during the very early (acute) and late stages of infection. Recognizing temporal differences in HIV shedding in the genital tract is important in the development of effective HIV prevention strategies.

Challenges in Detecting HIV Persistence during Potentially Curative Interventions: A Study of the Berlin Patient

There is intense interest in developing curative interventions for HIV. How such a cure will be quantified and defined is not known. We applied a series of measurements of HIV persistence to the study of an HIV-infected adult who has exhibited evidence of cure after allogeneic hematopoietic stem cell transplant from a homozygous CCR5Δ32 donor. Samples from blood, spinal fluid, lymph node, and gut were analyzed in multiple laboratories using different approaches. No HIV DNA or RNA was detected in peripheral blood mononuclear cells (PBMC), spinal fluid, lymph node, or terminal ileum, and no replication-competent virus could be cultured from PBMCs. However, HIV RNA was detected in plasma (2 laboratories) and HIV DNA was detected in the rectum (1 laboratory) at levels considerably lower than those expected in ART-suppressed patients. It was not possible to obtain sequence data from plasma or gut, while an X4 sequence from PBMC did not match the pre-transplant sequence. HIV antibody levels were readily detectable but declined over time; T cell responses were largely absent. The occasional, low-level PCR signals raise the possibility that some HIV nucleic acid might persist, although they could also be false positives. Since HIV levels in well-treated individuals are near the limits of detection of current assays, more sensitive assays need to be developed and validated. The absence of recrudescent HIV replication and waning HIV-specific immune responses five years after withdrawal of treatment provide proof of a clinical cure.

Antiretroviral Therapy Initiated Within 6 Months of HIV Infection Is Associated With Lower T-Cell Activation and Smaller HIV Reservoir Size

Background. CD4(+)/CD8(+) T-cell activation levels often remain elevated in chronic human immunodeficiency virus (HIV) infection despite initiation of antiretroviral therapy (ART). T-cell activation predicts early death and blunted CD4+ T-cell recovery during ART and may affect persistent HIV reservoir size. We investigated whether very early ART initiation is associated with lower on-therapy immune activation and HIV persistence. Methods. From a cohort of patients with early HIV infection (<6 months duration since infection) we identified persons who started ART early (<6 months after infection) or later (≥2 years after infection) and maintained ≥2 years of virologic suppression; at-risk HIV-negative persons were controls. We measured CD4(+)/CD8(+) T-cell activation (percent CD38(+)/HLA-DR(+)) and HIV reservoir size (based on HIV DNA and cell-associated RNA levels). Results. In unadjusted analyses, early ART predicted lower on-therapy CD8(+) T-cell activation (n = 34; mean, 22.1%) than achieved with later ART (n = 32; mean, 28.8%; P = .009), although levels in early ART remained elevated relative to HIV-negative controls (P = .02). Early ART also predicted lower CD4+ T-cell activation than with later ART (5.3% vs 7.5%; P = .06). Early ART predicted 4.8-fold lower DNA levels than achieved with later ART (P = .005), and lower cell-associated RNA levels (difference in signal-to-cutoff ratio (S/Co), 3.2; P = .035). Conclusions. ART initiation <6 months after infection is associated with lower levels of T-cell activation and smaller HIV DNA and RNA reservoir size during long-term therapy.

HIV in body fluids during primary HIV infection: Implications for pathogenesis, treatment and public health

ObjectiveTo describe initial viral dissemination to peripheral tissues and infectious body fluids during human primary HIV infection. DesignObservational cohort study. MethodsBlood plasma, cerebrospinal fluid (CSF), seminal plasma, cervicovaginal lavage fluid and/or saliva were sampled from 17 individuals with primary HIV infection (range of time from symptoms onset to sampling, 8–70 days) and one individual with early infection (168 days). Subjects’ HIV-1 RNA levels in each fluid were compared with levels from antiretroviral-naive controls with established HIV infection. For study subjects, correlations were assessed between HIV-1 RNA levels and time from symptoms onset. Responses to antiretroviral therapy with didanosine + stavudine + nevirapine ± hydroxyurea were assessed in each compartment. ResultsHIV-1 RNA levels were highest closest to symptoms gnset in blood plasma (18 patients) and saliva (11 patients). CSF HIV-1 RNA levels (five patients) appeared lower closer to symptoms onset, although they were higher overall in primary versus established infection. Shedding into seminal plasma (eight patients) and cervicovaginal fluid (two patients) was established at levels observed in chrgnic infection within 3–5 weeks of symptoms onset. High-level seminal plasma shedding was associated with coinfection with other sexually transmitted pathogens. Virus replication was suppressed in all compartments by antiretroviral therapy. ConclusionsPeak level HIV replication is established in blood, oropharyngeal tissues and genital tract, but potentially not in CSF, by the time patients are commonly diagnosed with primary HIV infection. Antiretroviral therapy is unlikely to limit initial virus spread to most tissue compartments, but may control genital tract shedding and central nervous system expansiof in primary infection.

Acute HIV revisited: new opportunities for treatment and prevention.

Inability to recognize incident infection has traditionally limited both scientific and public health approaches to HIV disease. Recently, some laboratories have begun adding HIV nucleic acid amplification testing to HIV diagnostic testing algorithms so that acute (antibody-negative) HIV infections can be routinely detected within the first 1-3 weeks of exposure. In this review article, we will highlight critical opportunities for HIV treatment and prevention that are presented by these diagnostic strategies.

Frequent detection of acute primary HIV infection in men in Malawi.

Background: Acute (antibody-negative) HIV infection is associated with high transmission potential but is rarely recognized. Design: Cross-sectional study. Methods: We examined the prevalence and predictors of acute HIV infection among 1361 consecutive male outpatients attending sexually transmitted disease (STD; n = 929) and dermatology (n = 432) clinics in Lilongwe, Malawi. Serum specimens negative for HIV antibodies were screened by HIV RNA PCR using a highly specific pooling/resolution testing algorithm. Results: Five-hundred and fifty-three men (40.6%) were HIV antibody positive and 24 (1.8%) had acute HIV infection; 23 of 24 acutely infected men were from the STD clinic, where they represented 4.5% of all HIV antibody-negative men and 5.0% of all HIV infections. HIV RNA levels for acutely infected men were significantly higher [median (interquartile range), 6.10 (5.19–6.54) log10 HIV RNA copies/ml] than for 58 HIV antibody-positive men [4.42 (3.91–4.95) log10 copies/ml; P < 0.0001]. The factor most strongly associated with acute HIV infection was STD clinic attendance: (odds ratio, 15.2; 95% confidence interval, 2.04–113.0). In multivariate analysis considering only STD patients, factors associated with acute HIV infection included inguinal adenopathy, genital ulceration and age 24–26 years, the age stratum associated with peak incidence of HIV infection among Malawian men. Conclusions: Traditional HIV antibody tests alone are not sufficient to exclude HIV infection among men with acute STD in Malawi due to a surprising proportion of acute HIV infections in this population. Alternative screening methods are required for diagnosis of acute HIV infection; such screening could be important for research and for prevention of the sexual transmission of HIV in select populations.

The unexpected movement of the HIV epidemic in the Southeastern United States: transmission among college students.

Background:Approximately 16 million people are enrolled in institutions of higher learning in the United States. However, college students have not been perceived as at high risk for HIV infection. In early 2003, acute HIV infection was diagnosed in 2 men attending college in North Carolina. We describe an epidemiologic investigation of newly diagnosed HIV infection in men attending college in North Carolina. Methods:We reviewed state surveillance records examining new HIV diagnoses in men 18-30 years old between January 1, 2000 and December 31, 2003, living in 69 North Carolina counties. Risk behavior and demographic information for HIV-infected men enrolled in college were compared with HIV-infected male nonenrollees. Results:Of the 735 records available for review, 84 (11%) were college men. Eighty-seven percent of college men were African American and 92% were men who have sex with men (MSM) or men who have sex with men and women (MSM/W). Compared with noncollege men, college men were more likely to be African American (odds ratio 3.70, 95% CI = 1.86-7.54), to report meeting sex partners at bars or dance clubs (odds ratio 3.01, 95% CI = 1.77-5.10) or on the Internet/chat lines (odds ratio 4.95, 95% CI = 2.53-9.64), or to report use of “ecstasy” or club drugs (odds ratio 4.51, 95% CI = 1.15-15.40). Newly diagnosed HIV infection was found in men in 37 colleges located in North Carolina or surrounding states and a sexual partner network investigation linked 21 colleges, 61 students, and 8 partners of students. Conclusion:We describe an epidemic of HIV infection occurring in North Carolina college students, primarily involving African American MSM and MSM/W. College students represent an at-risk, accessible population, which deserves further HIV prevention interventions.

HIV Antigens Can Induce TGF-β1-Producing Immunoregulatory CD8+ T Cells

HIV-infected individuals may progressively lose both HIV-specific and unrelated CTL responses despite the high number of circulating CD8+ T cells. In this study, we report that ∼25% of HIV+ donors produced TGF-β1 in response to stimulation with HIV proteins or peptides. The production of TGF-β1 was sufficient to significantly reduce the IFN-γ response of CD8+ cells to both HIV and vaccinia virus proteins. Ab to TGF-β reversed the suppression. We found the source of the TGF-β1 to be predominantly CD8+ cells. Different peptide pools stimulated TGF-β1 and IFN-γ in the same individual. The TGF-β1 secreting cells have distinct peptide specificity from the IFN-γ producing cells. This represents an important mechanism by which an HIV-specific response can nonspecifically suppress both HIV-specific and unrelated immune responses.

Multiple V1/V2 env variants are frequently present during primary infection with human immunodeficiency virus type 1

ABSTRACT Human immunodeficiency virus type 1 (HIV-1) exists as a complex population of multiple genotypic variants in persons with chronic infection. However, acute HIV-1 infection via sexual transmission is a low-probability event in which there is thought to be low genetic complexity in the initial inoculum. In order to assess the viral complexity present during primary HIV-1 infection, the V1/V2 and V3 variable regions of the env gene were examined by using a heteroduplex tracking assay (HTA) capable of resolving these genotypic variants. Blood plasma samples from 26 primary HIV-1-infected subjects were analyzed for their level of diversity. Half of the subjects had more than one V1/V2 viral variant during primary infection, indicating the frequent transmission of multiple variants. This observation is inconsistent with the idea of infrequent transmission based on a small transmitting inoculum of cell-free virus. In chronically infected subjects, the complexity of the viral populations was even greater in both the V1/V2 and the V3 regions than in acutely infected subjects, indicating that in spite of the presence of multiple variants in acute infection, the virus does pass through a genetic bottleneck during transmission. We also examined how well the infecting virus penetrated different anatomical compartments by using the HTA. Viral variants detected in blood plasma were compared to those detected in seminal plasma and/or cerebral spinal fluid of six individuals. The virus in each of these compartments was to a large extent identical to virus in blood plasma, a finding consistent with rapid penetration of the infecting variant(s). The low-probability transmission of multiple variants could be the result of transient periods of hyperinfectiousness or hypersusceptibility. Alternatively, the inefficient transfer of a multiply infected cell could account for both the low probability of transmission and the transfer of multiple variants.