CROI 2024: Tuberculosis, Mpox, and Other Infectious Complications in People With HIV

Abstract

Several novel antituberculosis agents, including long-acting injectable agents in mouse models, have shown promise in preclinical and early clinical studies. This encouraging news is offset by the failures of a tuberculosis (TB) vaccine to prevent disease recurrence and a 3-month clofazimine-based treatment regimen for drug-susceptible TB. Clinically focused insights regarding TB, mpox, and other HIV-associated infectious complications that were presented at the 2024 Conference on Retroviruses and Opportunistic Infections (CROI) are summarized in this review.

Tuberculosis

Treatment

An ongoing need remains for novel tuberculosis (TB) drugs and shorter, more effective treatment regimens. Recent successes, such as the high-dose rifapentine (RPT)/moxifloxacin (MOX) regimen¹ and the TRUNCATE-TB (Two-Month Regi mens Using Novel Combinations to Augment Treatment Effectiveness for Drug-Sensitive Tuberculosis) strategy,² which were summarized during an excellent plenary by Mave, have demonstrated that shorter effective treatment regimens are possible. Against this backdrop, 2 studies at this year's Conference on Retroviruses and Opportunistic Infections (CROI) reported on the safety and efficacy of novel short-course TB regimens.

Dawson and colleagues (Abstract 163) presented the interim results of a phase IIb/c randomized clinical trial evaluating 4 months of quabodepistat (QBS), a new anti-TB drug targeting a unique bacterial enzyme, in combination with delamanid (DLM) and bedaquiline (BDQ), compared with the standard of care (SOC) 6-month isoniazid (INH), rifampicin (RIF), pyrazinamide (PZA), and ethambutol (EMB) regimen (2HRZE/4HR). Participants with drug-susceptible TB (DS-TB) stratified by chest X-ray cavitation status were randomly assigned 1:2:2:1 to receive QBS at 10 mg (n=20), 30 mg (n=42), or 90 mg (n=39) once daily in combination with DLM and BDQ, or SOC (n=21). Of 121 participants (0% with HIV) in the modified intention-to-treat analysis, 100%, 92.9%, and 97.4% of participants in the QBS 10 mg, QBS 30 mg, and QBS 90 mg arms, respectively, met the primary outcome of sputum culture conversion (SCC) at the end of treatment, compared with 90.5% in the SOC arm. Overall, 96 of 100 participants (96%) receiving any QBS-containing regimen had SCC. Grade 3 adverse events were similar across QBS arms (~11%-12%), and 5% in the SOC arm; however, no serious adverse events were attributable to trial drugs. Furthermore, no clinically significant corrected QT-interval prolongation events or elevated liver enzyme levels were observed in the QBS arms. This interim analysis suggested that a QBS-based, 4-month regimen might serve as a viable alternative to the 6-month SOC regimen for DS-TB; however, 1-year treatment outcomes remain under assessment and will determine whether this regimen proceeds to a phase III trial.

The Clo-Fast trial (AIDS Clinical Trials Group A5362), a randomized, multicountry, open-label, phase IIc clinical trial presented by Metcalfe and colleagues (Abstract 164), evaluated a 3-month clofazimine (CFZ) and RPT regimen against the SOC among adults with DS-TB. Participants were randomly assigned 2:1:1 to the CFZ arm, receiving 8 weeks of CFZ (a 300-mg, 2-week loading dose followed by 100 mg for 6 weeks), high-dose RPT (1200 mg), INH, PZA, and ethambutol; a 6-month DS-TB SOC regimen; or a pharmacokinetic (PK) substudy arm evaluating CFZ/RPT/INH/PZA/ethambutol without a CFZ load. The dual primary endpoints were SCC at week 12 and grade 3 or higher adverse events through week 65. Overall, 89 participants (28% with HIV) were enrolled (58 in the CFZ arm and 31 in the SOC arm) before the trial was stopped early because of a lack of efficacy. Although the groups had similar SCC at 12 weeks (89% vs 90%; adjusted hazard ratio [aHR], 1.17; 90% CI, 0.79-1.73), the CFZ arm had a higher rate of poor clinical/bacteriologic outcomes (ie, absence of cure, treatment extension, loss to follow-up, or death) than the SOC arm (49% vs 34%; risk difference, −15%, 95% CI, −41 to 11). Additionally, the CFZ arm had more frequent grade 3 or higher adverse safety events (46% vs 16%; risk difference, 30%; 90% Ci, 14-45), largely because of changes in creatine clearance rate. These findings highlight the ineffectiveness and toxic effects of the 3-month CFZ-based regimen.

Ethionamide (Eto), a second-line anti-TB drug used primarily for multidrug-resistant TB, is associated with poor tolerability even at standard doses (typically gastrointestinal [GI] effects). Alpibectir (AlpE; formerly known as BVL-GSK098) enhances Eto bioactivation through alternative pathways, thereby leading to similar activity with lower exposures. Du Preez and colleagues (Abstract 157) conducted a phase II trial to assess the bactericidal activity (change in the time to liquid culture positivity over days 0 to 7 [TTP-EBA0-7]), safety, and tolerability of Eto in combination with AlpE. A total of 18 adults (0% with HIV) with untreated DS-TB were randomly assigned 5:1 to receive Eto (250 mg) plus AlpE (9 mg) for 7 days (n=15) or INH (300 mg) for 7 days (n=3). The median (2.5th-97.5th percentiles) TTP-EBA0-7 values were similar between the Eto plus AlpE and INH groups (45.3 hours [28.8-78.1] vs 48.4 hours [42.0-54.9], respectively); this value was similar to the TTP-EBA0-7 previously observed for INH in people with TB. Notably, no grade 3 or higher adverse events were observed in either arm, and only 4 of 15 participants (27%) experienced potential drug-related adverse events (primarily self-limiting diarrhea or flatulence). These encouraging results suggest that in the future, AlpE might serve as an additional well-tolerated and effective anti-TB agent.

Bictegravir (BIC) is a component of first-line treatment for HIV, but its effectiveness and safety, when used in combination with rifampicin (RIF)- based TB treatment in patients with HIV and TB coinfection, had not been evaluated. Naidoo and colleagues (Abstract 211) conducted the INSIGHT (iNSTIs for the Management of HIV-Associated TB) trial (NCT04734652), an open-label, phase IIb randomized clinical trial among adults with HIV (CD4+ count ≥50 cells/μL) and active TB, with or without prior antiretroviral therapy (ART), who were receiving RIF-based TB treatment. Participants were randomly assigned 2:1 to BIC/tenofovir alafenamide/emtricitabine (BIC/TAF/FTC; “BIC arm”) or SOC with tenofovir disoproxil fumarate/lamivudine/dolutegravir (DTG), (TLD; “DTG arm”). BIC/TAF/FTC and DTG had twice-daily administration until 2 weeks after completion of TB treatment, then once-daily treatment thereafter. The primary endpoint was week 24 viral suppression (HIV RNA <50 copies/ml). In addition to frequent viral-load assessments, semi-intensive PK sampling was performed during and after TB treatment. Overall, 122 participants were enrolled (median CD4+ count, 162 cells/μL; 42% with HIV RNA ≥100,000 copies/ml), 80 in the BIC arm and 42 in the DTG arm. At week 24, individuals in both arms were highly likely to be virally suppressed (95% and 95%) (US Food and Drug Administration [FDA] snapshot analysis). Adverse events of grade 3 or higher were common in the BIC (46%) and DTG (50%) arms, but none led to discontinuation, withdrawal, or changes in drugs. Drug exposure, as measured by the area under the concentration-time curve, was lower with BIC coadministration twice daily than with RIF than once daily without RIF (30.9 mg·h/L vs 94.9 mg·h/L, respectively). However, nearly all concentrations remained above the protein-adjusted 95% effective concentration (0.162 mg/l), even for participants with poor adherence. Only 1 such participant had a viral rebound, which was later resuppressed. Overall, when DTG-based therapy is not preferred or possible with RIF in patients with HIV and TB coinfection, clinicians could consider twice-daily BIC/TAF/FTC.

The focus of TB treatment programs on a cure often inadvertently overlooks the enduring consequences of TB after treatment, including diminished health and well-being. Banholzer and colleagues (Abstract 875) assessed changes in quality of life (Qol) associated with physical and mental health (Qol-PCS and Qol-MCS, respectively), depression (PHQ-9 questionnaire), and functional capacity (6-minute walk test distance) among participants with TB before and after treatment. Among 200 patients with TB (51%) in 5 African countries, Qol and functioning were diminished before treatment, as expected; however, at the end of treatment, substantial improvements were observed in Qol-PCS (39% increase; 95% Credible Interval [CrI], 35-44) and Qol-MCS (19% increase; 95% CI, 1622), including depression (PHQ-9, 26% decrease; 95 CrI, 22-31) and functional capacity (6-minute walk test distance, 15% increase; [95% CrI, 8-22). Notably, baseline lung cavitations were associated with worsening Qol and functional capacity following treatment. These findings emphasize the importance of evaluating post-TB treatment health, including Qol.

Prevention

One of the highest priorities in the TB field is the development of an effective and safe TB vaccine for adults. The H56:IC31 protein-adjuvant TB vaccine candidate was developed to prevent TB in adults with prior TB, who, despite completion of TB treatment, are at a substantially higher risk of future disease recurrence. Borges and colleagues conducted a double-blind, randomized, placebocontrolled phase IIb trial in adults without HIV in South Africa and Tanzania, who had recently completed treatment for pulmonary DS-TB (Abstract 210). Participants were randomly assigned (1:1) to receive 2 doses of H56:IC31 (415 participants) or a placebo (416 participants). The primary endpoint was TB recurrence within 1 year. A total of 831 participants were enrolled before the trial was stopped early because of a lack of efficacy. In the vaccine group, 23 (5.8%) participants experienced recurrent TB, compared with 14 (3.4%) in the placebo group (vaccine efficacy, −73.8%; 95% CI, −246.9 to 9.8; P=.10). Twelve (52%) of TB recurrences in the vaccine group and 6 (43%) in the placebo group were attributed to relapses (rather than reinfection). The vaccine was well tolerated and immunogenic. In this first-ever trial evaluating a vaccine candidate for the prevention of TB recurrence, H56:IC31 was not efficacious and might have increased TB risk. Work is underway to determine whether this finding might have been due to the vaccine's effects leading to an elevated risk of endogenous relapse. Fortunately, several other promising TB vaccine candidates are in phase IIb or III trials,³ for which results are expected within 3 to 5 years.

The 3-month INH and RPT (3HP) regimen is a highly effective short-course TB preventive therapy (TPT) that is safe and effective in people with HIV who are virally suppressed on DTG-based once-daily ART. However, its concomitant use in ART-naive adults initiating a DTG-based ART regimen had not been studied. Weld and colleagues (Abstract 156) performed DOLPHIN (Dolutegravir in Pregnant HIV Mothers and Their Neonates) TOO, a phase I/II comparative trial and sequentially enrolled adults with HIV starting TLD to 6 months of INH (6H; n=25) or 3HP (n=50), to evaluate DTG PK and 12- and 24-week HIV viral suppression. The baseline characteristics were similar between groups (CD4+ count, 283 cells/µL), except that the baseline viral load was lower in the 3HP group (median HIV RNA, 21,950 copies/mL vs 63,863 copies/mL, respectively). Overall, FDA snapshot analysis indicated that the week 12 and week 24 viral suppression (HIV RNA <50 copies/mL) was 88% (n=44/50) and 78% (n=39/50), respectively, in the 3HP group, and 92% (n = 23/25) and 88% (n = 20/25), respectively, in the 6H group. Among those with complete data available, this value improved to 100% (n=44/44) and 100% (n=39/39), respectively, in the 3HP group, and to 96% (n=23/24) and 91% (n=20/22), respectively, in the 6H group. Although RPT showed a 72% induction effect on DTG clearance, all DTG trough concentrations were above the protein-adjusted inhibition concentration (64 ng/mL) in all participants in the 3HP group at all time points sampled, and above the minimum target concentration (158 ng/mL) in all but 2 individuals, who subsequently had viral suppression. These data support concomitant TPT with 3HP in adults with HIV starting on an ART regimen containing once-daily DTG, when indicated.

Although 3HP is recommended for use with once-daily DTG-containing regimens, Chaisson and colleagues previously reported the interim results from a randomized clinical trial evaluating 2 TB screening strategies in Uganda. The findings indicated that that people with HIV receiving TLD in combination 3HP had lower 6-month viral suppression than those receiving TLD alone. At CROI this year (Abstract 878), Chaisson and colleagues presented the final study results, including 1379 adults (median baseline CD4+ count, 257 cells/μL), of whom 539 started 3HP within 2 weeks of TLD initiation, and 840 initiated TLD only. A total of 509 (94.4%) participants completed the 3HP treatment, and only 2 (0.4%) experienced an adverse event. Among those who initiated 3HP, 462 (85.7%) and 222 (53.4%) had viral suppression measured at 6 and 12 months, respectively. With an HIV RNA threshold of 50 or fewer copies/mL, the 6-month (72.9% vs 73.0%; P=.97) and 12-month (77.4% vs 77.5%; P=.98) vision was low for 3HP with TLD and TLD alone but did not differ between groups. With a threshold of 200 or fewer copies, the 6-month (90.9% vs 87.9%; P=.11) and 12-month (94.4% vs 92.6%; P=.33) virai suppression was higher and remained similar between arms.

Long-acting injectable (LAI) TPT formulations have the potential to revolutionize TPT by simplifying administration, thus overcoming adherence challenges, and providing additional choices for patients. Two studies in mouse models assessed the performance of LAI formulations of TB drugs for TB prevention, thus providing very early proof-of-concept data for LAI TPT, including single-shot formulations.

In the first study, Pertinez and colleagues (Abstract 880) evaluated the bactericidal activity and PK of 1, 2, or 4 injections of RPT at 3 doses (93.75, 187.5, and 375 mg/kg) over 4 weeks in paucibacillary mouse models, compared with 3 control groups (negative control, positive control with 4 weeks of daily INH with RPT (1HP), and 4 weeks of oral RPT). RPT-LAI single-injection doses (187.5 and 375 mg/kg) showed dose-linear PK. Notably, several regimens, including 375 mg/kg administered once, showed bactericidal activity equal to that of the 1HP control regimen and also demonstrated efficacy in decreasing the lung bacterial colonyforming units (CFUs).

In the second study, Nuermberger and colleagues (Abstract 881) evaluated the PK and efficacy of 3 single-injection formulations of TBAJ-876 (62.5 mg/kg, 125 mg/kg, and 250 mg/kg), next-generation diarylquinolones that are similar to BDQ, but have greater potency and lower corrected QT-interval prolongation potential. The plasma concentrations of each of the 3 formulations were above the target concentration (≥36 ng/mL) for more than 6 weeks after dosing. All 3 LAI formulations had similar bactericidal activity exceeding that of controls receiving 1HP or oral BDQ daily for 4 weeks.

Drug-Resistant Tuberculosis

After the primary analysis of the endTB (End Tuberculosis) study was reported, a key question remained: how did the treatments perform in people with HIV (PWH)? EndTB, a phase III, open-label, randomized clinical trial among people older than 15 years, evaluated 5 all-oral, 9-month regimens for fluoroquinolone-susceptible, RIF-resistant TB, compared with local SOC of 18- to 24-month regimens that were consistent with World Health Organization (WHO) recommendations. In the overall trial population, the following 3 regimens were safe and noninferior to SOC: (1) BDQ/linezolid (LZD)/MOX/PZA [9BLMZ], (2) BDQ/CFZ/LZD/levofloxacin (LFX)/PZA [9BCLLfxZ], and (3) BDQ/DLM/LZD/LFx/pZA [9BDLLfxZ]. At this year's conference, Velásquez and colleagues (Abstract 874) presented the safety and efficacy of these regimens in PWH. PWH were enrolled regardless of their CD4+ cell count, and the primary endpoint was a favorable 73-week outcome (2 consecutive negative cultures or favorable evolution), whereas unfavorable outcomes were death, treatment failure, drug addition/replacement, and retreatment. Among the 754 participants included and randomly assigned, 104 (13.8%) were PWH (median CD4+ count, 296 cells/µL). Similarly to the overall trial results, among PWH, 9BLMZ (n = 15) and 9BCLLfxZ (n = 14) were highly effective and were associated with favorable results: 93.3% (95% CI, 68.1-99.8) and 100% (95% CI, 76.8-100), respectively, compared with 89.5% (95% CI, 76.0-91.2) in the SOC control group (n=19). The efficacy in the other 3 interventional arms was 70.6% (95% CI, 44.0-89.7) (9BDLLfxZ; n=17), 83.3% (95% CI, 58.6-96.4) (DLM/CFZ/LZD/LFX/PZA; n=18), and 73.3% (95% CI, 44.9-92.2) (DLM/CFZ/MOX/PZA; n=15). Adverse events of grade 3 or higher and those leading to drug discontinuation were common in all arms but were highest in the SOC control arm. Although the small number of PWH in each arm (n=14 or 15) was acknowledged by the researchers, 9BLMZ and 9BCLLfxZ were found to be highly effective and safe for the treatment of DR-TB.

Pretomanid (Pa) is approved for DR-TB in combination with BDQ and LZD, with or without MOX; however, testicular toxicity has been observed in rodents exposed to high-dose Pa. To understand whether Pa might be associated with testicular toxicity in humans, Howell and colleagues (Abstract 872) evaluated changes in sperm count, sperm concentration, sperm volume, and reproductive hormone levels (testosterone, inhibin B, follicle-stimulating hormone, and luteinizing hormone) among men with DR-TB who received 26 weeks of BDQ/Pa/MOX/PZA. Among 22 men who completed treatment (36% PWH), by week 26, the mean total sperm count increased from baseline by 20.0 × 10⁶ sperm/ejaculate, whereas the mean sperm concentration increased from baseline by 25.8 × 10⁶ sperm/mL; only 2 participants had a decrease in sperm count exceeding 50% and none had a decrease in sperm concentration exceeding 50%. Changes in reproductive hormones by week 26 were consistent with improved spermatogenesis. This study, although small, provides reassurance that Pa, as part of the BDQ/Pa/MOX/PZA regimen for DR-TB, is not associated with testicular toxicity or negative reproductive effects.

Pediatric Tuberculosis

Infants with HIV are at elevated risk of TB disease, but diagnosis remains challenging, because of paucibacillary disease, and the nonspecific signs and symptoms. Mvalo and colleagues (Abstract 966) evaluated the prevalence and diagnostic accuracy of the symptom-based Graham criteria (persistent cough, weight loss/failure to thrive, persistent unexplained fever or lethargy, neonatal pneumonia, or hepatosplenomegaly) for TB among infants with HIV, who were hospitalized with severe pneumonia. This study was a secondary analysis embedded in a randomized clinical trial investigating the effects of empiric treatment of cytomegalovirus and TB in infants with HIV, who were hospitalized with severe pneumonia in 6 African countries. Those with a current TB diagnosis (clinical or confirmed) or a close contact were excluded from the parent study. Participants were intensively screened for the presence of TB disease at baseline with Xpert Ultra testing of stool and nasopharyngeal aspirates, and urine lipoarabinomannan testing. Microbiologically confirmed TB was present in 23% of the 496 included infants with HIV, and 96% (109/114) met 1 or more Graham criteria. The sensitivity, specificity, positive predictive value, and negative predictive value were 96.0%, 8.1%, 32.3%, and 80.0%, respectively. The prevalence of TB was extremely high among severely ill infants with HIV with pneumonia; a simple clinical criterion was almost universally positive but was highly nonspecific, and therefore would be an ineffective triage tool in this population, because of its poor discriminatory value.

Clinical Complications

Although extrapulmonary TB, including pericardial involvement, is a well-known disease, limited research has systematically evaluated its frequency and the response of TB-associated cardiac abnormalities to TB treatment. Samim and colleagues (Abstract 1731) have systematically evaluated adults and adolescents (>15 years of age) with TB (clinical or microbiologically confirmed) in 2 cohorts (Zambia and South Africa) for the presence of cardiac abnormalities through transthoracic echocardiography, before and after 6 months of TB treatment. Among 240 participants (38% PWH), the most frequent abnormalities before TB treatment were pericardial effusion (48%), pericardial thickening (34%), left atrial dilation (17%), diastolic dysfunction (8%), and pericardial calcification (3%). Signs of constriction were observed in 47% of participants. Although only 50 patients had follow-up transthoracic echocardiograms available after TB treatment, most experienced resolution of their previous pericardial effusion (n=24/30; 80% resolution) and pericardial thickness (n = 11/18; 61% resolution); however, signs of constriction often persisted (n=4/12; 33% resolution). Data from this cohort study demonstrate that pericardial disease is common in patients with TB in southern Africa but often improves after TB treatment.

Mpox

In 2023, as the incidence of mpox cases notably declined, the research presented at CROI shifted toward deeper exploration of the immune response in individuals with mpox and the continual collection of observational data regarding treatment approaches.

Epidemiology

In the only oral abstract presentation focused on mpox, Torres da Silva and colleagues (Abstract 198) highlighted a second major mpox outbreak in Brazil. As in the US, mpox cases in Brazil peaked in the summer of 2022, then decreased to 0 recognized cases in July and August of 2023. However, by September, cases began increasing again, and disproportionately affected gay, bisexual, and other men who have sex with men (MSM), as well as PWH with concurrent bacterial sexually transmitted infections. However, during the second outbreak, a marked increase was observed in the time to diagnosis. Although recurrent large mpox outbreaks have been rare, Chicago experienced a slight resurgence in cases in April 2023. Molecular epidemiology data presented by Simons and colleagues (Abstract 425) demonstrate that 11 lineages were circulating during the initial 2022 Chicago outbreak. However, during the resurgence, all cases belonged to the same lineage, thus suggesting that they resulted from a single transmission cluster. Identifying the source of a resurgence may be more challenging than expected. In a study by Salvo and colleagues (Abstract 1079), 7% of cohort participants (84 with HIV) had IgG positivity for mpox but did not recall any prior symptoms, thus suggesting the possibility of asymptomatic mpox infection. Individuals unaware that they have mpox might be contributing to ongoing transmission. Evidence of second notable outbreaks in Brazil, Chicago, and other areas highlights the importance of ongoing and low-barrier testing, to prevent delays in diagnosis and disease propagation, as well as the crucial nature of ongoing vaccination efforts, even in times of low incidence. Furthermore, targeted outreach encouraging mpox testing, even if the results are negative, may effectively improve the provision of comprehensive sexual health services (Abstract 1088), including mpox vaccination.

Presentation and Treatment

A highlight of CROI 2023 was Orkin and colleagues’ presentation of a global case series highlighting the close relationship between CD4+ count and complications in people with mpox. Although the traditional guidance has been to offer investigational mpox treatment to people with CD4+ counts below 200 cells/μL, Montano and colleagues (Abstract 423), using epidemiologic data from the CNICS (Center for AIDS Research Network of Integrated Clinical Systems) cohort, found notable associations among CD4+ counts of 350 cells/μL or lower, detectable viral loads, lack of ART, and hospitalization after mpox diagnosis. These data, in agreement with those in last year's presentation, suggest that the risk of severe disease may extend beyond individuals with CD4+ counts below 200 cells/μL, and include those with CD4+ counts of 200 to 350 cells/μL.

Although data collection from randomized clinical trials for the treatment of mpox is ongoing, observational data and case series of patients treated with currently available medical countermeasures have filled some knowledge gaps. Aldred and colleagues (Abstract 419) retrospectively reviewed PWH diagnosed with mpox at 4 sites in Atlanta, to assess progression to severe disease in patients receiving early treatment (<7 days after symptom onset) with tecovirimat, compared with those receiving late or no treatment. Of 262 eligible individuals, 56 propensity-matched participants were included in each arm. PWH with mpox who received early tecovirimat were less likely to have mpox progression than matched PWH who did not receive early tecovirimat (5.4% vs 23.2%; P =.006).⁴ This research offers valuable initial insights into tecovirimat's likely effectiveness; nonetheless, randomized clinical trials are necessary to validate these conclusions.⁵

One concern regarding the widespread use of tecovirimat stems from in vitro data suggesting it has a low barrier to resistance due to needing only a single nucleotide mutation to develop resistance. Recent reports have highlighted the emergence of resistance in immunocompromised individuals receiving prolonged treatment courses. A possible cause of the emergence of resistance might be under-dosing because current dosing guidelines are based on efficacy in nonhuman primates and PK data from noninfected volunteers. Wei and colleagues (Abstract 428) examined the PKs of tecovirimat in people diagnosed with mpox in the ACTG 5418 STOMP (Study of Tecovirimat for Mpox) study. lower tecovirimat exposures were found in participants (n=12) than had been observed in the earlier trial data for noninfected adults. However, concentrations remained above the minimally effective concentration (C_min) from the studies in nonhuman primates. This aspect may be concerning for select patients whose levels may approach the C_min, given that Marcelin and colleagues (Abstract 422) described the rapid emergence of resistance-associated mutations in a patient with suboptimal tecovirimat plasma concentrations. Further studies to understand the emergence of resistance to tecovirimat will be crucial. These data highlight the importance of collecting PK data in randomized clinical trials, particularly involving drugs previously evaluated only in noninfected volunteers.

Immune Responses

Understanding of the immune response to mpox infection and differences among anatomic compartments is crucial to comprehension of the various presentations of mpox and may inform the development of future therapeutics. A study by Moraes-Cardoso and colleagues (Abstract 416) enrolled 33 men (14 PWH) with mpox to evaluate the time to clearance and the relationship between antibody (IgA and IgG) and T-cell responses. All patients had comparable neutralization capacity, which peaked 3 months after diagnosis, although the PWH had a smaller increase and faster decrease in mpox-specific antibodies than the other participants. The titers and the breadth of antibodies induced after infection were each associated with clinical severity and the rate of viral clearance. All patients showed a sustained T-cell response as many as 6 months after mpox diagnosis. These data suggest that mpox-specific antibodies may play a key role in initial infection control. Further studies are needed to determine the role of baseline immune responses in outcomes (responder/non-responder fallacy), whether durable cellular immunity might prevent or decrease the severity of future infections, or whether further vaccinations might be required to maintain antibody quantity and breadth.

Beyond immunoglobulins and T-cell responses, interferons (IFNs) are crucial in addressing viral infections, both directly and indirectly. D'Auria and colleagues (Abstract 418) evaluated the IFN and IFN-stimulated gene (ISG) response at various anatomic sites in 18 patients with mpox. IFN-α, IFN-A1, and the specific ISG PKR were significantly upregulated in rectal samples compared with other clinical samples, whereas levels of IFN-β and IFN-ω were elevated in skin lesions. To advance this translational work, the researchers used antiviral assays to assess the sensitivity of monkeypox virus to various types of IFNs. In their in vitro model, IFN-β had moderate antiviral activity, whereas IFN-γ strongly inhibited replication. The study highlights the differential expression of IFNs and ISGs in response to mpox infection across anatomical sites, and may have future therapeutic implications, particularly for patients with severe disease. With cases occurring daily in the US and a substantial clade I outbreak in the Democratic Republic of the Congo, mpox is likely to remain a topic of discussion at CROI. Needs remain to complete randomized clinical trials on tecovirimat, to explore the roles of other treatments (eg, cidofovir and brincidofovir), and to gain a better understanding of the immune response in people with mpox infection and vaccinated against mpox, to better understand the durability and effectiveness of immune protection.

Opportunistic Infections

Cryptococcal meningitis (CM) and tuberculous meningitis (TBM) are the most common causes of HIV-associated meningitis. Their associated mortality remains extremely high, reaching 25% to 50%. HIV viral escape reflects diminished control of HIV replication in the central nervous system and may be associated with neuroinflammation. Ellis and colleagues (Abstract 887) conducted a prospective cohort study in Uganda, among adult PWH with suspected meningitis, to evaluate whether cerebrospinal fluid (CSF) viral escape might be associated with elevated mortality in HIV-associated meningitis. Paired venous blood and CSF samples were collected for HIV viral load testing before treatment and viral escape was defined by the presence of quantifiable HIV RNA in the CSF exceeding that in the plasma. Participants were classified as having CM (first or recurrent), TBM (definite or probably), or another syndrome (compatible clinical syndrome not meeting the CM or TBM definition). Overall, 152 PWH were enrolled (median CD4+ count, 59 cells/μL. Only 42% were receiving ART at presentation, and 70% had detectable plasma viremia (median viral load, 4000 copies/mL). CSF viral escape was present in 30% of participants (n=46) and was associated with higher CSF white blood cell counts and shorter ART duration. A total of 48% (n=73) of participants had CM, 32% (n=49) had probable or confirmed TBM, and 20% (n=30) had a suspected “other” meningitis. CSF viral escape was associated with lower 18-week mortality overall (aHR, 0.46; 95% CI, 0.21-0.99), and when restricted to CM (aHR, 0.48; 95% CI, 0.13-1.71) and TBM (aHR, 0.34; 95% CI, 0.10-1.19). I mproved survival was observed in those with higher HIV viral load in the CSF than plasma, in the context of meningitis. The authors hypothesized that this finding might represent a “bystander effect,” with HIV-RNA-containing lymphocytes and monocytes being trafficked into the central nervous system as part of an effective host response.

Cryptococcosis

Although daily liposomal amphotericin B (L-AmB) in conjunction with flucytosine (5FC) is a recommended first-line treatment for CM, the recommendation is based on very limited data. Boulware and colleagues (Abstract 888) evaluated the comparative early fungicidal activity (BFA) of CSF and the cryptococcal clearance rate in PWH with CM, who were enrolled in cohorts and clinical trials and who were receiving ambisome deoxycholate (AmB; 1 mg/kg) plus 5FC (100 mg/kg/d), or L-AmB (3 mg/kg/d) plus 5FC (100 mg/kg/d). In both groups, ambisome formulations were given for 7 days during induction, and therapy was subsequently consolidated to fluconazole (1200 mg/d for 2 weeks), then fluconazole (800 mg/d for 10 weeks). Among 201 participants with CSF clearance data (n=46 in the L-AmB group), no differences in CSF antifungal activity were observed between the L-AmB group (EFA, 0.50 log₁₀ CFU/mL/d; 95% CI, 0.36-0.64) and the AmB group (EFA, 0.40 log₁₀ CFU/mL/d; 95% CI, 0.36-0.44). A trend toward higher mortality in the AmB group than in the L-AmB group (30% vs 20%, respectively) was observed; however, after adjustment for baseline characteristics, the difference was not significant (aHR, 1.35; 95% CI, 0.80-2.27). Overall, these results indicated similar efficacy of L-AmB and AmB and support current Department of Health and Human Services recommendations regarding use and dosage.

Cryptococcal antigen (CrAg) titer is associated with elevated mortality in CM and may aid in clinical risk stratification. However, current methods for determining CrAg titers are often unavailable in resource-limited settings. Two studies this year demonstrated the high diagnostic accuracy and correlation with CrAg titers, and the strong prognostic value of a newer low-cost, semiquantitative, lateral-flow assay (LFA) (CrAgSQ, IMMY) on plasma samples. Implementation of this assay in resource-limited settings may help identify PWH with cryptococcemia at the highest risk of short-term mortality, who may benefit from closer clinical follow-up.

In the first study, Boyd and colleagues (Abstract 893) evaluated the CrAgSQ assay on biobanked pretreatment blood and CSF samples from PWH with their first CM episode, in the AMBITION-cm (AMBIsome Therapy Induction Optimisation) trial; participants were followed up for 10 weeks to determine their vital status. Among 796 participants across 6 African countries (median CD4+ count, 27 cells/µL), the 2-week and 10-week survival was 13% and 27%, respectively. Plasma-based CrAgSQ testing was positive in 99.9% of cases (n=744/745), whereas CSF-based CrAgSQ testing was positive in 98.7% (n=746/756). The semiquantitative scores (0-4) from plasma and CSF CrAgSQ testing were positively correlated with each other and with CSF fungal culture growth (ie, burden). A strong correlation was found between the plasma CrAgSQ score and 2-week mortality: 0%, 4.4%, 13.9%, and 34.6%, for scores of 1+, 2+, 3+, and 4+, respectively (P <.0001 for trend). Similar associations were not observed between the CSF CrAgSQ score and 2-week mortality.

In the second study, Nguyen and colleagues (Abstract 892) evaluated the CrAgSQ assay among 2 cohorts of adults in Vietnam with advanced HIV disease who were screened for cryptococcosis with a standard CrAg LFA. Follow-up of those with a positive CrAg for 12 months was conducted to assess mortality. Overall, 901 inpatients and 1576 outpatients underwent CrAg LFA screening, of whom 93 (3.8%) were positive; 85 of these 93 had samples available for subsequent testing, and 30 CrAgnegative outpatients were selected at random as controls. The sensitivity of the CrAgSQ assay was 97.6% (95% CI, 90.9-99.6; n=83/85), and the specificity was 96.9% (95% CI, 82.0-99.8; n = 30/32). CrAgSQ assay scores were strongly associated with median CrAg titer: 1+ (1:5), 2+ (1:56), 3+ (1:5042), and 4+ (1:114,104). Moreover, the 12-month mortality was higher in those with a pretreatment CrAgSQ score of 3+ or 4+ (39.0%) than 1+ or 2 + (19.2%; P=.06).

Invasive Mycoses

In people with advanced HIV disease, the WHO recommends screening for TB and CM; however, other invasive mycoses, including talaromycosis and histoplasmosis, which are endemic to Southeast Asia, are not included, partly because of a lack of available diagnostics and data regarding their regional burden. Quoc Dat and colleagues (Abstract 890) intensively investigated Vietnamese inpatients (n=900) and outpatients (n=500) with advanced HIV disease (CD4+ count <100 cells/µL or WHO stage III/IV) and performed follow-up for at least 6 months. The study aim was to determine the prevalence of, and outcomes associated with, talaromycosis and histoplasmosis, in addition to CM, TB, and infections with other nontuberculous mycobacteria (HTM), to inform local policy. Overall, invasive mycoses were present in 27.3% (talaromycosis, 19.8%; cryptococcosis, 4.3%; histoplasmosis, 2.9%) of inpatients and 9.5% (talaromycosis, 4.2%; cryptococcosis, 5.5%; histoplasmosis, 0.6%) of outpatients. TB or NTM was present in 33.0% (28.0% TB; 5.1%, NTM) of inpatients and 8.9% (7.6% TB; 1.4% NTM) of outpatients. The 6-month mortality was highest for cryptococcosis (42.9%), followed by TB (27.0%), histoplasmosis (26.9%), NTM (23.9%), and talaromycosis (12.4%). This study from Vietnam among people with advanced HIV disease indicated a high prevalence of several opportunistic infections, including talaromycosis and histoplasmosis, particularly among hospitalized patients, who had a high probability of mortality. The authors proposed adding talaromycosis and histoplasmosis to the WHO advanced HIV disease package of care for the Asia-Pacific region.

Kaposi Sarcoma-Associated Herpesvirus and Human Papillomavirus

Kaposi Sarcoma Herpesvirus

Visceral Kaposi sarcoma (KS) involves the GI and respiratory tracts, and is caused by Kaposi sarcoma herpesvirus (KSHV). Bronchoscopy and endoscopy, the gold standard for the diagnosis of KS, are often unavailable in resource-limited settings. Witterholt and colleagues (Abstract 749) retrospectively evaluated whether KSHV viral load measurement from saliva has useful diagnostic accuracy in detecting visceral KS, in a US-based cohort of people with suspected visceral KS. All participants with a history of KS who underwent bronchoscopy or endoscopy/colonoscopy for symptoms concerning for pulmonary or GI KS between 2005 and 2023 were included. Saliva samples were collected within 1 week of diagnostic procedures, and KSHV DNA was quantified. Of 60 patients included, 57 (95%) were PWH (77% on ART; median CD4+ count, 125 cells/μL; median HIV viral load, 87 copies). A total of 26 (43%) participants had GI (n=18) or pulmonary KS (n=8), 15 (25%) of whom had both Gi and pulmonary KS, and 19 (32%) of whom had skin KS without visceral involvement. The median KSHV saliva viral load was 1 (interquartile range, 0 to 67,566) copies/10⁶ cells, and an optimized threshold of 190 copies/10⁶ cells had an associated sensitivity, specificity, and positive likelihood ratio of 46%, 76%, and 2, respectively, for visceral KS. The median survival time from diagnosis was 9.2 years in patients with GI or pulmonary KS but was 2.6 years in patients with both GI and pulmonary KS. Saliva KSHV was not found to be useful as a standalone noninvasive measurement for detecting visceral KS; however, this study sheds light on the continued burden of visceral KS and poor survival, even among PWH with well-controlled HIV disease.

Human Papillomavirus

PWH face a significantly elevated risk of anal cancer. Notably, the proactive treatment of precancerous anal lesions (ie, high-grade intraepithelial lesions) can markedly decrease this risk.⁶ However, the success of this intervention relies on wide availability of, and access to, effective diagnostic strategies for early identification of these lesions. Two studies at this year's CROI have addressed knowledge gaps related to anal cancer screening and diagnosis.

Anal Papanicolaou (Pap) testing is often unavailable for MSM in many resource-limited settings. Charpentier and colleagues (Abstract 761) have evaluated the acceptability, feasibility, and comparative performance of anal-swab self-collection vs practitioner collection among MSM in Togo. All participants performed self-collection, which was followed by practitioner collection, and samples were assessed for the presence of 14 high-risk human papillomavirus (hrHPV) types through polymerase chain reaction. Among 188 MSM (57% PWH), 94% of self-collected samples were suitable for hrHPV testing, compared with 96% of practitioner-collected samples. One or more hrHPV types were identified in 83% (147/177) of self-collected samples, compared with 76% (136/180) of practitioner-collected samples, including 28% (49/177) and 26% (46/180), respectively, positive for HPV16. Overall, 90% agreement was observed for hrHPV detection (κ=0.66) and also for HPV16 (κ=0.75). A total of 99% of participants indicated that the selfcollection was easy, and 60% indicated that they would prefer to perform self-collection at their next visit. This study builds on other research in high-income settings showing that self-performed anal Pap testing may be an acceptable and feasible strategy to increase the proportion of MSM who undergo screening for anal cancer.

High-resolution anoscopy (HRA) with biopsy is the gold standard for anal cancer diagnosis. However, access is severely limited by a lack of trained practitioners and prolonged scheduling delays. Therefore, effective triage strategies are needed to prioritize HRA for people at the highest risk of anal cancer. Cavallari and colleagues (Abstract 760) performed a retrospective analysis in MSM with HIV who underwent HRA with biopsy to evaluate the diagnostic utility of 8 clinical algorithms, using anal cytology and hrHPV polymerase chain reaction results, alone and in combination, for high-grade squamous intraepithelial lesion (HSIL) confirmed by HRA-guided biopsy. Among 180 participants (median CD4+ count, 800 cells/µL), HSIL was detected in 77 HRA-guided biopsies (42.8% prevalence). No strategy exceeded 90% sensitivity, and the best-performing strategy was the detection of any hrHPV type, which would have resulted in 105 HRAs, and had an associated sensitivity and specificity of 84.8% and 62.7%, respectively. Using atypical squamous cells of undetermined significance (ASCUS) or low-grade squamous intraepithelial lesion (LSIL) cytology threshold would have resulted in more HRAs (125 and 107, respectively), and lower associated sensitivity (70.9% and 62.0%, respectively) and specificity (32.4% and 43.1%, respectively). A combination of ASCUS or worse and HPV16 resulted in fewer HRAs (n=43), and improved specificity (87.3%) but low sensitivity (38.0%). Although any hrHPV type had reasonable performance as a triage strategy, 15% of HSILs would have been missed, thus suggesting that further research is needed to identify highly accurate and feasible triage strategies while access to HRA remains limited in many settings.