A Multivariant Surrogate Virus Neutralization Test Demonstrates Distinct SARS-CoV-2-Specific Antibody Responses in People Living with HIV after a Fourth Monovalent mRNA Vaccination or an Omicron Breakthrough Infection.

While neutralizing antibodies (nAbs) induced by monovalent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccinations are primarily directed against the wildtype (WT), subsequent exposure to the Omicron variants may increase the breadth of the antibodies' cross-neutralizing activity. Here, we analyzed the impact of an Omicron breakthrough infection (BTI) or a fourth monovalent mRNA vaccination on nAb profiles in people living with human immunodeficiency virus (PLWH). Using a multivariant surrogate virus neutralization test (sVNT), we quantified nAbs in 36 three-times vaccinated PLWH, of whom 9 acquired a serologically confirmed Omicron BTI, 8 received a fourth vaccine dose, and 19 were neither infected nor additionally vaccinated. While nAbs against WT and Delta increased after the BTI and a fourth vaccination, a significant increase against BA.1, BA.2, and BA.5 was only observed after the BTI. However, there was no significant difference in nAb concentrations between the samples obtained after the BTI and fourth vaccination. In contrast, nAb levels were significantly lower in PLWH, who were neither infected nor additionally vaccinated after three vaccinations. Thus, our study demonstrates the suitability of a multivariant sVNT to assess hybrid humoral immunity after Omicron BTIs in PLWH vaccinated against SARS-CoV-2.

Heavy antiretroviral exposure and exhausted/limited antiretroviral options: predictors and clinical outcomes.

OBJECTIVES: People with HIV and extensive antiretroviral exposure may have limited/exhausted treatment options (LExTO) due to resistance, comorbidities, or antiretroviral-related toxicity. Predictors of LExTO were investigated in the RESPOND cohort. METHODS: Participants on ART for at least 5 years were defined as having LExTO when switched to at least two anchor agents and one third antiretroviral (any class), a two-drug regimen of two anchor agents (excluding rilpivirine with dolutegravir/cabotegravir), or at least three nucleoside reverse transcriptase inhibitors. Baseline was the latest of January 1, 2012, cohort enrolment or 5 years after starting antiretrovirals. Poisson regression modeled LExTO rates and clinical events (all-cause mortality, non-AIDS malignancy, cardiovascular disease [CVD], and chronic kidney disease [CKD]). RESULTS: Of 23 827 participants, 2164 progressed to LExTO (9.1%) during 130 061 person-years follow-up (PYFU); incidence 1.66/100 PYFU (95% CI 1.59-1.73). Predictors of LExTO were HIV duration more than 15 years (vs. 7.5-15; adjusted incidence rate ratio [aIRR] 1.32; 95% CI 1.19-1.46), development of CKD (1.84; 1.59-2.13), CVD (1.64; 1.38-1.94), AIDS (1.18; 1.07-1.30), and current CD4 + cell count of 350 cells/µl or less (vs. 351-500 cells/µl, 1.51; 1.32-1.74). Those followed between 2018 and 2021 had lower rates of LExTO (vs. 2015-2017; 0.52; 0.47-0.59), as did those with baseline viral load of 200 cp/ml or less (0.46; 0.40-0.53) and individuals under 40. Development of LExTO was not significantly associated with clinical events after adjustment for age and current CD4, except CKD (1.74; 1.48-2.05). CONCLUSION: Despite an aging and increasingly comorbid population, we found declining LExTO rates by 2018-2021, reflecting recent developments in contemporary ART options and clinical management. Reassuringly, LExTO was not associated with a significantly increased incidence of serious clinical events apart from CKD.

Evaluation of consensus method for the culture of Burkholderia pseudomallei in soil samples from Laos.

Background: We have previously shown that PCR following enrichment culture is the most sensitive method to detect Burkholderia pseudomallei in environmental samples. Here we report an evaluation of the published consensus method for the culture of B. pseudomallei from Lao soil in comparison with our conventional culture method and with PCR with or without prior broth enrichment. Methods: One hundred soil samples were collected from a field known to contain B. pseudomallei and processed by: (i) the conventional method, (ii-iii) the consensus method using media prepared in either Laos or Thailand, and (iv) the consensus method performed in Thailand, as well as by (v) PCR following direct extraction of DNA from soil and (vi) PCR following broth pre-enrichment. Results: The numbers of samples in which B. pseudomallei was detected were 42, 10, 7, 6, 6 and 84, respectively. However, two samples were positive by the consensus method but negative by conventional culture, and one sample was negative by PCR following enrichment although B. pseudomallei was isolated by the conventional culture method. Conclusions/Discussion: The results show that no single method will detect all environmental samples that contain B. pseudomallei. People conducting environmental surveys for this organism should be aware of the possibility of false-negative results using the consensus culture method. An approach that entails screening using PCR after enrichment, followed by the evaluation of a range of different culture methods on PCR-positive samples to determine which works best in each setting, is recommended.

The Utility of Blood Culture Fluid for the Molecular Diagnosis of Leptospira: A Prospective Evaluation.

Leptospirosis is an important zoonosis worldwide, with infections occurring after exposure to contaminated water. Despite being a global problem, laboratory diagnosis remains difficult with culture results taking up to 3 months, serology being retrospective by nature, and polymerase chain reaction showing limited sensitivity. Leptospira have been shown to survive and multiply in blood culture media, and we hypothesized that extracting DNA from incubated blood culture fluid (BCF), followed by quantitative real-time polymerase chain reaction (qPCR) could improve the accuracy and speed of leptospira diagnosis. We assessed this retrospectively, using preincubated BCF of Leptospira spp. positive (N= 109) and negative (N= 63) febrile patients in Vientiane, Lao PDR. The final method showed promising sensitivities of 66% (95% confidence interval [CI]: 55-76) and 59% (95% CI: 49-68) compared with direct or direct and indirect testing combined, as the respective reference standards (specificities > 95%). Despite these promising diagnostic parameters, a subsequent prospective evaluation in a Lao hospital population (N= 352) showed that the sensitivity was very low (∼30%) compared with qPCR on venous blood samples. The disappointingly low sensitivity does suggest that venous blood samples are preferable for the clinical microbiology laboratory, although BCF might be an alternative if leptospirosis is only suspected postadmission after antibiotics have been used.

Land use and soil type determine the presence of the pathogen Burkholderia pseudomallei in tropical rivers.

Burkholderia pseudomallei is the bacterium that causes melioidosis in humans. While B. pseudomallei is known to be endemic in South East Asia (SEA), the occurrence of the disease in other parts of the tropics points towards a potentially large global distribution. We investigated the environmental factors that influence the presence (and absence) of B. pseudomallei in a tropical watershed in SEA. Our main objective was to determine whether there is a link between the presence of the organism in the hydrographic network and the upstream soil and land-use type. The presence of B. pseudomallei was determined using a specific quantitative real-time PCR assay following enrichment culture. Land use, soil, geomorphology, and environmental data were then analyzed using partial least squares discriminant analysis (PLSDA) to compare the B. pseudomallei positive and negative sites. Soil type in the surrounding catchment and turbidity had a strong positive influence on the presence (acrisols and luvisols) or absence (ferralsols) of B. pseudomallei. Given the strong apparent links between soil characteristics, water turbidity, and the presence/absence of B. pseudomallei, actions to raise public awareness about factors increasing the risk of exposure should be undertaken in order to reduce the incidence of melioidosis in regions of endemicity.

Evaluation of Molecular Methods To Improve the Detection of Burkholderia pseudomallei in Soil and Water Samples from Laos.

Burkholderia pseudomallei is the cause of melioidosis, a severe and potentially fatal disease of humans and animals. It is endemic in northern Australia and Southeast Asia and is found in soil and surface water. The environmental distribution of B. pseudomallei worldwide and within countries where it is endemic, such as the Lao People's Democratic Republic (Laos), remains unclear. However, this knowledge is important to our understanding of the ecology and epidemiology of B. pseudomallei and to facilitate public health interventions. Sensitive and specific methods to detect B. pseudomallei in environmental samples are therefore needed. The aim of this study was to compare molecular and culture-based methods for the detection of B. pseudomallei in soil and surface water in order to identify the optimal approach for future environmental studies in Laos. Molecular detection by quantitative real-time PCR (qPCR) was attempted after DNA extraction directly from soil or water samples or after an overnight enrichment step. The positivity rates obtained by qPCR were compared to those obtained by different culture techniques. The rate of detection from soil samples by qPCR following culture enrichment was significantly higher (84/100) than that by individual culture methods and all culture methods combined (44/100; P < 0.001). Similarly, qPCR following enrichment was the most sensitive method for filtered river water compared with the sensitivity of the individual methods and all individual methods combined. In conclusion, molecular detection following an enrichment step has proven to be a sensitive and reliable approach for B. pseudomallei detection in Lao environmental samples and is recommended as the preferred method for future surveys.

Long term immunity following a booster dose of the inactivated Japanese Encephalitis vaccine IXIARO®, IC51.

INTRODUCTION: IXIARO (IC51), a recently approved inactivated Japanese Encephalitis vaccine, is immunogenic and safe in a 0/28 days primary immunization schedule. Neutralizing antibody titers decline with time and booster doses are likely needed to enhance persistence of immunity. OBJECTIVES: To assess the effect of a booster dose on neutralizing JE antibody titers for up to 12 months after boostering. METHODS: In this phase III trial, 198 subjects, who had received primary immunization in a preceding randomized trial, were boosted with IXIARO 15 months after the primary immunization. Neutralizing antibody titers were assessed by plaque-reduction neutralisation test, PRNT. RESULTS: Prior to the booster dose, 69.2% (137/198) of subjects had PRNT50 titers ≥ 1:10. One month after the booster, the rate of subjects with PRNT50 ≥ 1:10 (recognized as a protective titer) was 100%. This rate remained high at 98.5% at 6 and 12 months; GMTs were 22.5 before the booster and 900, 487 and 361 at 1, 6 and 12 months after the booster, respectively. CONCLUSION: A booster dose of IXIARO at 15 months after primary immunization was highly immunogenic with GMTs >5-fold higher than those seen immediately after primary immunization, and remained at high levels for at least 12 months after the booster.