A Comparative Analysis of Innate Immune Responses and the Structural Characterization of Spike from SARS-CoV-2 Gamma Variants and Subvariants

The SARS-CoV-2 P.1 variant, responsible for an outbreak in Manaus, Brazil, is distinguished by 12 amino acid differences in the S protein, potentially increasing its ACE-2 affinity and immune evasion capability. We investigated the innate immune response of this variant compared to the original B.1 strain, particularly concerning cytokine production. Blood samples from three severe COVID-19 patients were analyzed post-infection with both strains. Results showed no significant difference in cytokine production of mononuclear cells and neutrophils for either variant. While B.1 had higher cytopathogenicity, neither showed viral replication in mononuclear cells. Structural analyses of the S protein highlighted physicochemical variations, which might be linked to the differences in infectivity between the strains. Our studies point to the increased infectivity of P.1 could stem from altered immunogenicity and receptor-binding affinity.

Active surveillance for influenza virus and coronavirus infection in Antarctic birds and mammals in environmental fecal samples, South Shetland Islands

Numerous Antarctic species are recognized as reservoirs for various pathogens, and their migratory behavior allows them to reach the Brazilian coast, potentially contributing to the emergence and circulation of new infectious diseases. To address the potential zoonotic risks, we conducted surveillance of influenza A virus (IAV) and coronaviruses (CoVs) in the Antarctic Peninsula, specifically focusing on different bird and mammal species in the region. During the summer of 2021/2022, as part of the Brazilian Antarctic Expedition, we collected and examined a total of 315 fecal samples to target these respiratory viruses. Although we did not detect the viruses of interest during this particular expedition, previous research conducted by our team has shown the presence of the H11N2 subtype of influenza A virus in penguin fecal samples from the same region. Given the continuous emergence of new viral strains worldwide, it is crucial to maintain active surveillance in the area, contributing to strengthening integrated One Health surveillance efforts.

The Role of Children in Household Transmission of SARS-CoV-2 Across Four Waves of the Pandemic

BACKGROUND

It is important to understand the dynamics of SARS-CoV-2 transmission in close-contact settings such as households. We hypothesized that children would most often acquire SARS-CoV-2 from a symptomatic adult caregiver.

METHODS

This prospective cohort study was conducted from April 2020 to July 2022 in a low-resource, urban settlement in Brazil. We recruited families who brought their children to a public clinic. We collected nasopharyngeal and oral swabs from household members and tracked symptoms and vaccination.

RESULTS

In total, 1256 participants in 298 households were tested for SARS-CoV-2. A total of 4073 RT-PCR tests were run with 893 SARS-CoV-2 positive results (21.9%). SARS-CoV-2 cases were defined as isolated cases (N = 158) or well-defined transmission events (N = 175). The risk of household transmission was lower if the index case was a child (OR: 0.3 [95% CI: 0.16-0.55], P < .001) or was vaccinated (OR: 0.29 [95% CI: 0.1-0.85], P = .024), and higher if the index was symptomatic (OR: 2.53 [95% CI: 1.51-4.26], P < .001). The secondary attack rate for child index cases to child contacts was 0.29, whereas the secondary attack rate for adult index cases to child contacts was 0.47 (P = .08).

CONCLUSIONS

In this community, children were significantly less infectious to their household contacts than adolescents or adults. Most children were infected by a symptomatic adult, usually their mother. There was a double benefit of vaccination as it protected the vaccine from severe illness and prevented onward transmission to household contacts. Our findings may also be valid for similar populations throughout Latin America.

Reduced ability to neutralize the Omicron variant among adults after infection and complete vaccination with BNT162b2, ChAdOx1, or CoronaVac and heterologous boosting

COVID-19 vaccines have dramatically reduced rates of severe infection requiring hospitalization. However, SARS-CoV-2 variants have reduced vaccine effectiveness at preventing any symptomatic infection. This real-world study analyzed binding and neutralizing antibodies generated after complete vaccination and boosting across three vaccine platforms. Binding antibodies decayed most slowly in people under 60 with hybrid immunity. Neutralizing antibodies against Omicron BA.1 were reduced compared to other variants. The anamnestic anti-spike IgG response to the first boost was more pronounced than after the second boost. Monitoring of the effects of SARS-CoV-2 mutations on disease severity and the effectiveness of therapeutics is warranted.

Accuracy of saliva for SARS-CoV-2 detection in outpatients and their household contacts during the circulation of the Omicron variant of concern

BACKGROUND

While nasopharyngeal (NP) swabs are considered the gold standard for severe acute respiratory coronavirus 2 (SARS-CoV-2) real-time reverse transcriptase-polymerase chain reaction (RT-PCR) detection, several studies have shown that saliva is an alternative specimen for COVID-19 diagnosis and screening.

METHODS

To analyze the utility of saliva for the diagnosis of COVID-19 during the circulation of the Omicron variant, participants were enrolled in an ongoing cohort designed to assess the natural history of SARS-CoV-2 infection in adults and children. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and Cohen's kappa coefficient were calculated to assess diagnostic performance.

RESULTS

Overall, 818 samples were collected from 365 outpatients from January 3 to February 2, 2022. The median age was 32.8 years (range: 3-94 years). RT-PCR for SARS-CoV-2 was confirmed in 97/121 symptomatic patients (80.2%) and 62/244 (25.4%) asymptomatic patients. Substantial agreement between saliva and combined nasopharyngeal/oropharyngeal samples was observed with a Cohen's kappa value of 0.74 [95% confidence interval (CI): 0.67-0.81]. Sensitivity was 77% (95% CI: 70.9-82.2), specificity 95% (95% CI: 91.9-97), PPV 89.8% (95% CI: 83.1-94.4), NPV 87.9% (95% CI: 83.6-91.5), and accuracy 88.5% (95% CI: 85.0-91.4). Sensitivity was higher among samples collected from symptomatic children aged three years and older and adolescents [84% (95% CI: 70.5-92)] with a Cohen's kappa value of 0.63 (95% CI: 0.35-0.91).

CONCLUSIONS

Saliva is a reliable fluid for detecting SARS-CoV-2, especially in symptomatic children and adolescents during the circulation of the Omicron variant.

SARS-CoV-2 infection of human brain microvascular endothelial cells leads to inflammatory activation through NF-κB non-canonical pathway and mitochondrial remodeling

Neurological effects of COVID-19 and long-COVID-19 as well as neuroinvasion by SARS-CoV-2 still pose several questions and are of both clinical and scientific relevance. We described the cellular and molecular effects of the human brain microvascular endothelial cells (HBMECs) in vitro infection by SARS-CoV-2 to understand the underlying mechanisms of viral transmigration through the Blood-Brain Barrier. Despite the low to non- productive viral replication, SARS-CoV-2-infected cultures displayed increased apoptotic cell death and tight junction protein expression and immunolocalization. Transcriptomic profiling of infected cultures revealed endothelial activation via NF-κB non-canonical pathway, including RELB overexpression, and mitochondrial dysfunction. Additionally, SARS-CoV-2 led to altered secretion of key angiogenic factors and to significant changes in mitochondrial dynamics, with increased mitofusin-2 expression and increased mitochondrial networks. Endothelial activation and remodeling can further contribute to neuroinflammatory processes and lead to further BBB permeability in COVID-19.

Incidence of SARS-CoV-2 over four epidemic waves in a low-resource community in Rio de Janeiro, Brazil: A prospective cohort study

Background

Incidence rates of SARS-CoV-2 infections in low-resource communities can inform vaccination strategies and non-pharmaceutical interventions (NPIs). Our objective was to estimate incidence over four epidemic waves in a slum in Rio de Janeiro, a proxy for economically deprived areas in the Global South.

Methods

Prospective cohort of children and household contacts screened for SARS-CoV-2 by PCR and serology (IgG). The incidence density of PCR positive infections estimated for each wave - the first wave, Zeta, Gamma and Delta - was compared to an index combining NPIs and vaccination coverage.

Findings

718 families and 2501 individuals were enrolled, from May 2020 to November 2021. The incidence density of SARS-CoV-2 infection due to the first wave was 2, 3 times that of the other waves. The incidence among children was lower than that of older participants, except in later waves, when vaccination of the elderly reached 90%. Household agglomeration was significantly associated with incidence only during the first wave.

Interpretation

The incidence of infection greatly exceeded rates reported in similar cohorts. The observed reduction in incidence in the elderly during the Delta variant wave, in spite of the rollback of NPIs, can be attributed to increased vaccine coverage. The high incidence in young people reinforces the importance of vaccination in this age group, a policy that has yet to receive the full support of some sectors of society.

Funding

UK Medical Research Council, Foundation for the Advancement of Science of the State of Rio de Janeiro, National Council for Scientific and Technological Development.

Implementation of a COVID-19 Genomic Surveillance Regional Network for Latin America and Caribbean region

The timely release of SARS-CoV-2 first genomic sequences allowed the identification of the etiologic agent and development of diagnostic protocols. Genomic sequencing was a crucial step in generating data for driving laboratory response and detections of SARS-CoV-2 since the start of the COVID-19 pandemic. Because of all the progression and achievements that timely release of genetic sequence data represents in the public health response, the Pan American Health Organization (PAHO) in collaboration with countries' public health laboratories, started implementation of a network for strengthening the Latin America and Caribbean (LAC) region on timely generation of SARS-CoV-2 genomic data. Here we describe the implementation of the COVID-19 Genomic Surveillance Regional Network in the Americas region during the beginning of the pandemic. The establishment of this network has strengthened laboratory response capacity at the country level, as well as facilitated timely release of SARS-CoV-2 genomic information to be used to complement the multiple response strategies for COVID-19 pandemic mitigation. As genomic epidemiology is useful for guiding public health decisions on outbreak and response, we also analysed the first SARS-CoV-2 genomic sequence data from countries of the Latin America and Caribbean Region.

The Chemokine CCL5 Inhibits the Replication of Influenza A Virus Through SAMHD1 Modulation

Influenza A virus (IAV) is the main etiological agent of acute respiratory tract infections. During IAV infection, interferon triggers the overexpression of restriction factors (RFs), the intracellular antiviral branch of the innate immune system. Conversely, severe influenza is associated with an unbalanced pro-inflammatory cytokine release. It is unclear whether other cytokines and chemokines released during IAV infection modulate RFs to control virus replication. Among the molecules enhanced in the infected respiratory tract, ligands of the CCR5 receptor play a key role, as they stimulate the migration of inflammatory cells to the alveoli. We investigated here whether ligands of the CCR5 receptor could enhance RFs to levels able to inhibit IAV replication. For this purpose, the human alveolar basal epithelial cell line (A549) was treated with endogenous (CCL3, CCL4 and CCL5) or exogenous (HIV-1 gp120) ligands prior to IAV infection. The three CC-chemokines tested reduced infectious titers between 30% to 45% upon 24 hours of infection. Eploying RT-PCR, a panel of RF mRNA levels from cells treated with CCR5 agonists was evaluated, which showed that the SAMHD1 expression was up-regulated four times over control upon exposure to CCL3, CCL4 and CCL5. We also found that IAV inhibition by CCL5 was dependent on PKC and that SAMHD1 protein levels were also increased after treatment with CCL5. In functional assays, we observed that the knockdown of SAMHD1 resulted in enhanced IAV replication in A549 cells and abolished both CCL5-mediated inhibition of IAV replication and CCL5-mediated cell death inhibition. Our data show that stimuli unrelated to interferon may trigger the upregulation of SAMHD1 and that this RF may directly interfere with IAV replication in alveolar epithelial cells.

SARS-CoV-2 Infection Dynamics in Children and Household Contacts in a Slum in Rio de Janeiro

OBJECTIVES

To investigate the dynamics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in a vulnerable population of children and their household contacts.

METHODS

SARS-CoV-2 reverse transcription polymerase chain reaction assays and coronavirus disease 2019 (COVID-19) immunoglobulin G serology tests were performed in children and their household contacts after enrollment during primary health care clinic visits. Participants were followed prospectively with subsequent specimens collected through household visits in Manguinhos, an impoverished urban slum (a favela) in Rio de Janeiro at 1, 2, and 4 weeks and quarterly post study enrollment.

RESULTS

Six hundred sixty-seven participants from 259 households were enrolled from May to September 2020. This included 323 children (0-13 years), 54 adolescents (14-19 years), and 290 adults. Forty-five (13.9%) children had positive test results for SARS-CoV-2 polymerase chain reaction. SARS-CoV-2 infection was most frequent in children aged <1 year (25%) and children aged 11 to 13 years (21%). No child had severe COVID-19 symptoms. Asymptomatic infection was more prevalent in children aged <14 years than in those aged ≥14 years (74.3% and 51.1%, respectively). All children (n = 45) diagnosed with SARS-CoV-2 infection had an adult contact with evidence of recent infection.

CONCLUSIONS

In our setting, children do not seem to be the source of SARS-CoV-2 infection and most frequently acquire the virus from adults. Our findings suggest that, in settings such as ours, schools and child care potentially may be reopened safely if adequate COVID-19 mitigation measures are in place and staff are appropriately immunized.

Inflammatory Cytokine Patterns Associated with Neurological Diseases in Coronavirus Disease 2019

Patients with coronavirus disease 2019 (COVID‐19) can present with distinct neurological manifestations. This study shows that inflammatory neurological diseases were associated with increased levels of interleukin (IL)‐2, IL‐4, IL‐6, IL‐10, IL‐12, chemokine (C‐X‐C motif) ligand 8 (CXCL8), and CXCL10 in the cerebrospinal fluid. Conversely, encephalopathy was associated with high serum levels of IL‐6, CXCL8, and active tumor growth factor β1. Inflammatory syndromes of the central nervous system in COVID‐19 can appear early, as a parainfectious process without significant systemic involvement, or without direct evidence of severe acute respiratory syndrome coronavirus 2 neuroinvasion. At the same time, encephalopathy is mainly influenced by peripheral events, including inflammatory cytokines. ANN NEUROL 2021;89:1041–1045

Cerebrospinal fluid findings in neurological diseases associated with COVID-19 and insights into mechanisms of disease development

OBJECTIVES

To analyze the cerebrospinal fluid (CSF) of patients with SARS-CoV-2 infection and neurological manifestations to provide evidence for the understanding of mechanisms associated with central nervous system (CNS) involvement in COVID-19.

METHODS

Patients (n = 58) were grouped according to their main neurological presentation: headache (n = 14); encephalopathy (n = 24); inflammatory neurological diseases, including meningoencephalitis (n = 4), acute myelitis (n = 3), meningitis (n = 2), acute disseminated encephalomyelitis (ADEM) (n = 2), encephalitis (n = 2), and neuromyelitis optica (n = 1); and Guillain-Barré syndrome (n = 6). Data regarding age, sex, cerebrovascular disease, and intracranial pressure were evaluated in combination with CSF profiles defined by cell counts, total protein and glucose levels, concentration of total Tau and neurofilament light chain (NfL) proteins, oligoclonal band patterns, and detection of SARS-CoV-2 RNA.

RESULTS

CSF of patients with inflammatory neurological diseases was characterized by pleocytosis and elevated total protein and NfL levels. Patients with encephalopathy were mostly older men (mean age of 61.0 ± 17.6 years) with evidence of cerebrovascular disease. SARS-CoV-2 RNA in CSF was detected in 2 of 58 cases: a patient with refractory headache, and another patient who developed ADEM four days after onset of COVID-19 symptoms. Three patients presented intrathecal IgG synthesis, and four had identical oligoclonal bands in CSF and serum, indicating systemic inflammation.

CONCLUSION

Patients with neurological manifestations associated with COVID-19 had diverse CSF profiles, even within the same clinical condition. Our findings indicate a possible contribution of viral replication on triggering CNS infiltration by immune cells and the subsequent inflammation promoting neuronal injury.

Results from the WHO external quality assessment for the respiratory syncytial virus pilot, 2016-17

Background

External quality assessments (EQAs) for the molecular detection of respiratory syncytial virus (RSV) are necessary to ensure the provision of reliable and accurate results. One of the objectives of the pilot of the World Health Organization (WHO) Global RSV Surveillance, 2016‐2017, was to evaluate and standardize RSV molecular tests used by participating countries. This paper describes the first WHO RSV EQA for the molecular detection of RSV.

Methods

The WHO implemented the pilot of Global RSV Surveillance based on the WHO Global Influenza Surveillance and Response System (GISRS) from 2016 to 2018 in 14 countries. To ensure standardization of tests, 13 participating laboratories were required to complete a 12 panel RSV EQA prepared and distributed by the Centers for Disease Control and Prevention (CDC), USA. The 14th laboratory joined the pilot late and participated in a separate EQA. Laboratories evaluated a RSV rRT‐PCR assay developed by CDC and compared where applicable, other Laboratory Developed Tests (LDTs) or commercial assays already in use at their laboratories.

Results

Laboratories performed well using the CDC RSV rRT‐PCR in comparison with LDTs and commercial assays. Using the CDC assay, 11 of 13 laboratories reported correct results. Two laboratories each reported one false‐positive finding. Of the laboratories using LDTs or commercial assays, results as assessed by Ct values were 100% correct for 1/5 (20%). With corrective actions, all laboratories achieved satisfactory outputs.

Conclusions

These findings indicate that reliable results can be expected from this pilot. Continued participation in EQAs for the molecular detection of RSV is recommended.

Patients with COVID-19 and neurological manifestations show undetectable SARS-CoV-2 RNA levels in the cerebrospinal fluid

We report that patients with COVID-19 displaying distinct neurological disorders have undetectable or extremely low levels of SARS-CoV-2 RNA in the cerebrospinal fluid, indicating that viral clearance precede the neurological involvement. This finding points to the need for the development of more sensitive molecular tests and the investigation of other neurotropic pathogens to exclude concurrent neuroinfection.

A31 Diversity change of influenza A (H3N2) strains circulating in Brazil during 2017–8: What to expect in the coming winter?

The H3N2 subtype of influenza A (H3N2) was the predominant strain during the early months of the 2017 influenza epidemic in Brazil. In Australia, it was responsible for a strong and prolonged 2017 season and reached the Northern hemisphere causing an intense 2017/8 influenza season. Several genetic and antigenic A(H3N2) variants were circulating, which made the decision about which strain to incorporate into the influenza vaccine challenging. For 2018, the WHO selected a new H3N2 strain, A/Singapore/INFIMH-16-0019/2016-like, to replace the strain A/HongKong/4801/2014-like in the Southern Hemisphere trivalent vaccine. The aim of this study was to describe the genetic diversity of influenza A (H3N2) viruses circulating in Brazil between January 2017 and January 2018, checking the match between the vaccines and worldwide circulating strains with the Brazilian influenza strains. Hemagglutinin gene sequencing of the influenza A (H3N2) was performed, followed by a phylogenetic reconstruction using additional database sequences to define genetic groups and compare with other worldwide circulating strains. We observed a large diversity of H3N2 genetic clusters, including 3C.2a, 3C.2a1, 3C.3a, and their subgroups. During the 2016–7, inter-epidemic and 2017 epidemic period the cluster most frequently detected belonged to clade 3C.2a1 (148/185; 80.0%), a distinct group related to the 2017 vaccine strain A/HongKong/4801/2014-like (3C.2a). However, the genetic profile changed during the study period and in the inter-epidemic season 2017–8 the most commonly detected genetic group was the 3C.2a cluster (43/58; 74.1%). Inside this cluster, the majority (34/43; 79.1%) of strains belonged to a single genetic 3C.2a subgroup 2 (3C.2a2), bearing antigenic substitutions T131K and R142K (site A) and R261Q (site E). The dominance of this 3C.2a2 in the 2017–8 inter-epidemic period in Brazil was similar to the 2017–8 season in Europe and Canada according their surveillance data. The new vaccine strain has five to six antigenic changes in comparison to the predominant 3C.2a2 circulating in South America since September 2017 until now. It is possible that the vaccine mismatch will not protect the population against a majority of circulating strains. Surveillance of the vaccine effectiveness supported by antigenic and serological analysis are necessary to prove this hypothesis. However, this highlights the difficulty of vaccine strain selection and highlights the need for of a universal influenza vaccine.

Inhibitory effect of microalgae and cyanobacteria extracts on influenza virus replication and neuraminidase activity

Background

The influenza virus can cause seasonal infections with mild to severe symptoms, circulating worldwide, and it can affect people in any age group. Therefore, this infection is a serious public health problem that causes severe illness and death in high-risk populations. Every year, 0.5% of the world’s population is infected by this pathogen. This percentage can increase up to ten times during pandemics. Influenza vaccination is the most effective way to prevent disease. In addition, anti-influenza drugs are essential for prophylactic and therapeutic interventions. The oseltamivir (OST, a neuraminidase inhibitor) is the primary antiviral used in clinics during outbreaks. However, OST resistant viruses may emerge naturally or due to antiviral pressure, with a prevalence of 1–2% worldwide. Thus, the search for new anti-influenza drugs is extremely important. Currently, several groups have been developing studies describing the biotechnological potential of microalgae and cyanobacteria, including antiviral activity of their extracts. In Brazil, this potential is poorly known and explored.

Methods

With the aim of increasing the knowledge on this topic, 38 extracts from microalgae and cyanobacteria isolated from marine and freshwater biomes in Brazil were tested against: cellular toxicity; OST-sensitive and resistant influenza replications; and neuraminidase activity.

Results

For this purpose, Madin-Darby Canine Kidney (MDCK)-infected cells were treated with 200 μg/mL of each extract. A total of 17 extracts (45%) inhibited influenza A replication, with seven of them resulting in more than 80% inhibition. Moreover, functional assays performed with viral neuraminidase revealed two extracts (from Leptolyngbya sp. and Chlorellaceae) with IC₅₀ mean < 210 μg/mL for influenza A and B, and also OST-sensitive and resistant strains. Furthermore, MDCK cells exposed to 1 mg/mL of all the extracts showed viability higher than 80%.

Discussion

Our results suggest that extracts of microalgae and cyanobacteria have promising anti-influenza properties. Further chemical investigation should be conducted to isolate the active compounds for the development of new anti-influenza drugs. The data generated contribute to the knowledge of the biotechnological potential of Brazilian biomes that are still little explored for this purpose.

Zika virus impairs the development of blood vessels in a mouse model of congenital infection

Zika virus (ZIKV) is associated with brain development abnormalities such as primary microcephaly, a severe reduction in brain growth. Here we demonstrated in vivo the impact of congenital ZIKV infection in blood vessel development, a crucial step in organogenesis. ZIKV was injected intravenously in the pregnant type 2 interferon (IFN)-deficient mouse at embryonic day (E) 12.5. The embryos were collected at E15.5 and postnatal day (P)2. Immunohistochemistry for cortical progenitors and neuronal markers at E15.5 showed the reduction of both populations as a result of ZIKV infection. Using confocal 3D imaging, we found that ZIKV infected brain sections displayed a reduction in the vasculature density and vessel branching compared to mocks at E15.5; altogether, cortical vessels presented a comparatively immature pattern in the infected tissue. These impaired vascular patterns were also apparent in the placenta and retina. Moreover, proteomic analysis has shown that angiogenesis proteins are deregulated in the infected brains compared to controls. At P2, the cortical size and brain weight were reduced in comparison to mock-infected animals. In sum, our results indicate that ZIKV impairs angiogenesis in addition to neurogenesis during development. The vasculature defects represent a limitation for general brain growth but also could regulate neurogenesis directly.

In vitro T-cell profile induced by BCG Moreau in healthy Brazilian volunteers

Tuberculosis (TB) remains the world's leading cause of morbidity and mortality. Although Mycobacterium bovis bacillus Calmette-Guérin (BCG) is the only vaccine currently in use, its efficacy is highly variable. It has been suggested that early antigenic presentation is a pivotal event leading to a better immune response in TB vaccine models. To investigate this further, we compared in vitro cell-mediated immune responses in the context of early sensitization with TB (i.e. healthy adults vaccinated with BCG when they were young, HD; n = 25) to those in its absence (i.e., newborns with naïve immunity to TB, UV; n = 10) by challenging mononuclear cells with BCG Moreau. After 48 hours, CD4+ and CD8+ T cells were harvested from both groups and stained for PD-1/CD25/ FOXP3. In addition, supernatants were assayed for a broad range of cytokines using an array system. The HD group showed robust reactivity to Protein Purified Derivative and BCG while the naïve, UV group did not. Similarly, in terms of PD-1 expression and Treg cells (CD4+/CD25high(+)/FOXP3+), only the HD group showed higher levels in CD4 lymphocytes. Otherwise, only the UV group showed expression of CD25dim+ as an activation marker dependent on BCG infection. In terms of cytokines, the HD group showed higher levels of Th1 (IL-2/TNF-α/IFN-γ) and regulatory (IL-10) profiles, with monocytes, but not Tr1 cells, acting as the main source of IL-10. Taken together, our results highlight critical roles of early sensitization with TB in mounting cell-mediated immune responses.

Immunogenicity and sustainability of the immune response in Brazilian HIV-1-infected individuals vaccinated with inactivated triple influenza vaccine

HIV-infected individuals have a higher risk of serious illnesses following infection by infection with influenza. Although anti-influenza vaccination is recommended, immunosuppression may limit their response to active immunization. We followed-up a cohort of HIV-infected individuals vaccinated against influenza to assess the immunogenicity and sustainability of the immune response to vaccination. Individuals were vaccinated 2011 with inactivated triple influenza vaccine (TIV), and they had received in 2010 the monovalent anti-A(H1N1)pdm09 vaccine. The sustainability of the immune response to A(H1N1)pdm09 at 12 months after monovalent vaccination fell, both in individuals given two single or two double doses. For these individuals, A(H1N1)pdm09 component from TIV acted as a booster, raising around 40% the number of seroprotected individuals. Almost 70% of the HIV-infected individuals were already seroprotected to A/H3N2 at baseline. Again, TIV boosted over 90% the seroprotection to A/H3N2. Anti-A/H3N2 titers dropped by 20% at 6 months after vaccination. Pre-vaccination seroprotection rate to influenza B (victoria lineage) was the lowest among those tested, seroconversion rates were higher after vaccination. Seroconversion/protection after TIV vaccination did not differ significantly across categories of clinical and demographic variables. Anti-influenza responses in Brazilian HIV-infected individuals reflected both the previous history of virus circulation in Brazil and vaccination.

Strengthening the influenza vaccine virus selection and development process: Report of the 3rd WHO Informal Consultation for Improving Influenza Vaccine Virus Selection held at WHO headquarters, Geneva, Switzerland, 1-3 April 2014

Despite long-recognized challenges and constraints associated with their updating and manufacture, influenza vaccines remain at the heart of public health preparedness and response efforts against both seasonal and potentially pandemic influenza viruses. Globally coordinated virological and epidemiological surveillance is the foundation of the influenza vaccine virus selection and development process. Although national influenza surveillance and reporting capabilities are being strengthened and expanded, sustaining and building upon recent gains has become a major challenge. Strengthening the vaccine virus selection process additionally requires the continuation of initiatives to improve the timeliness and representativeness of influenza viruses shared by countries for detailed analysis by the WHO Global Influenza Surveillance and Response System (GISRS). Efforts are also continuing at the national, regional, and global levels to better understand the dynamics of influenza transmission in both temperate and tropical regions. Improved understanding of the degree of influenza seasonality in tropical countries of the world should allow for the strengthening of national vaccination policies and use of the most appropriate available vaccines. There remain a number of limitations and difficulties associated with the use of HAI assays for the antigenic characterization and selection of influenza vaccine viruses by WHOCCs. Current approaches to improving the situation include the more-optimal use of HAI and other assays; improved understanding of the data produced by neutralization assays; and increased standardization of serological testing methods. A number of new technologies and associated tools have the potential to revolutionize influenza surveillance and response activities. These include the increasingly routine use of whole genome next-generation sequencing and other high-throughput approaches. Such approaches could not only become key elements in outbreak investigations but could drive a new surveillance paradigm. However, despite the advances made, significant challenges will need to be addressed before next-generation technologies become routine, particularly in low-resource settings. Emerging approaches and techniques such as synthetic genomics, systems genetics, systems biology and mathematical modelling are capable of generating potentially huge volumes of highly complex and diverse datasets. Harnessing the currently theoretical benefits of such bioinformatics ("big data") concepts for the influenza vaccine virus selection and development process will depend upon further advances in data generation, integration, analysis and dissemination. Over the last decade, growing awareness of influenza as an important global public health issue has been coupled to ever-increasing demands from the global community for more-equitable access to effective and affordable influenza vaccines. The current influenza vaccine landscape continues to be dominated by egg-based inactivated and live attenuated vaccines, with a small number of cell-based and recombinant vaccines. Successfully completing each step in the annual influenza vaccine manufacturing cycle will continue to rely upon timely and regular communication between the WHO GISRS, manufacturers and regulatory authorities. While the pipeline of influenza vaccines appears to be moving towards a variety of niche products in the near term, it is apparent that the ultimate aim remains the development of effective "universal" influenza vaccines that offer longer-lasting immunity against a broad range of influenza A subtypes.

Detection of respiratory viruses by real-time polymerase chain reaction in outpatients with acute respiratory infection

Viruses are the major contributors to the morbidity and mortality of upper and lower acute respiratory infections (ARIs) for all age groups. The aim of this study was to determine the frequencies for a large range of respiratory viruses using a sensitive molecular detection technique in specimens from outpatients of all ages with ARIs. Nasopharyngeal aspirates were obtained from 162 individuals between August 2007-August 2009. Twenty-three pathogenic respiratory agents, 18 respiratory viruses and five bacteria were investigated using multiplex real-time reverse transcriptase polymerase chain reaction (RT-PCR) and indirect immunofluorescence assay (IIF). Through IIF, 33 (20.4%) specimens with respiratory virus were recognised, with influenza virus representing over half of the positive samples. Through a multiplex real-time RT-PCR assay, 88 (54.3%) positive samples were detected; the most prevalent respiratory viral pathogens were influenza, human rhinovirus and respiratory syncytial virus (RSV). Six cases of viral co-detection were observed, mainly involving RSV. The use of multiplex real-time RT-PCR increased the viral detection by 33.9% and revealed a larger number of respiratory viruses implicated in ARI cases, including the most recently described respiratory viruses [human bocavirus, human metapneumovirus, influenza A (H1N1) pdm09 virus, human coronavirus (HCoV) NL63 and HCoV HKU1].

Improving influenza vaccine virus selection: report of a WHO informal consultation held at WHO headquarters, Geneva, Switzerland, 14-16 June 2010

• For almost 60 years, the WHO Global Influenza Surveillance and Response System (GISRS) has been the key player in monitoring the evolution and spread of influenza viruses and recommending the strains to be used in human influenza vaccines. The GISRS has also worked to continually monitor and assess the risk posed by potential pandemic viruses and to guide appropriate public health responses. • The expanded and enhanced role of the GISRS following the adoption of the International Health Regulations (2005), recognition of the continuing threat posed by avian H5N1 and the aftermath of the 2009 H1N1 pandemic provide an opportune time to critically review the process by which influenza vaccine viruses are selected. In addition to identifying potential areas for improvement, such a review will also help to promote greater appreciation by the wider influenza and policy-making community of the complexity of influenza vaccine virus selection. • The selection process is highly coordinated and involves continual year-round integration of virological data and epidemiological information by National Influenza Centres (NICs), thorough antigenic and genetic characterization of viruses by WHO Collaborating Centres (WHOCCs) as part of selecting suitable candidate vaccine viruses, and the preparation of suitable reassortants and corresponding reagents for vaccine standardization by WHO Essential Regulatory Laboratories (ERLs). • Ensuring the optimal effectiveness of vaccines has been assisted in recent years by advances in molecular diagnosis and the availability of more extensive genetic sequence data. However, there remain a number of challenging constraints including variations in the assays used, the possibility of complications resulting from non-antigenic changes, the limited availability of suitable vaccine viruses and the requirement for recommendations to be made up to a year in advance of the peak of influenza season because of production constraints. • Effective collaboration and coordination between human and animal influenza networks is increasingly recognized as an essential requirement for the improved integration of data on animal and human viruses, the identification of unusual influenza A viruses infecting human, the evaluation of pandemic risk and the selection of candidate viruses for pandemic vaccines. • Training workshops, assessments and donations have led to significant increases in trained laboratory personnel and equipment with resulting expansion in both geographical surveillance coverage and in the capacities of NICs and other laboratories. This has resulted in a significant increase in the volume of information reported to WHO on the spread, intensity and impact of influenza. In addition, initiatives such as the WHO Shipment Fund Project have facilitated the timely sharing of clinical specimens and virus isolates and contributed to a more comprehensive understanding of the global distribution and temporal circulation of different viruses. It will be important to sustain and build upon the gains made in these and other areas. • Although the haemagglutination inhibition (HAI) assay is likely to remain the assay of choice for the antigenic characterization of viruses in the foreseeable future, alternative assays - for example based upon advanced recombinant DNA and protein technologies - may be more adaptable to automation. Other technologies such as microtitre neuraminidase inhibition assays may also have significant implications for both vaccine virus selection and vaccine development. • Microneutralization assays provide an important adjunct to the HAI assay in virus antigenic characterization. Improvements in the use and potential automation of such assays should facilitate large-scale serological studies, while other advanced techniques such as epitope mapping should allow for a more accurate assessment of the quality of a protective immune response and aid the development of additional criteria for measuring immunity. • Standardized seroepidemiological surveys to assess the impact of influenza in a population could help to establish well-characterized banks of age-stratified representative sera as a national, regional and global resource, while providing direct evidence of the specific benefits of vaccination. • Advances in high-throughput genetic sequencing coupled with advanced bioinformatics tools, together with more X-ray crystallographic data, should accelerate understanding of the genetic and phenotypic changes that underlie virus evolution and more specifically help to predict the influence of amino acid changes on virus antigenicity. • Complex mathematical modelling techniques are increasingly being used to gain insights into the evolution and epidemiology of influenza viruses. However, their value in predicting the timing and nature of future antigenic and genetic changes is likely to be limited at present. The application of simpler non-mechanistic statistical algorithms, such as those already used as the basis of antigenic cartography, and phylogenetic modelling are more likely to be useful in facilitating vaccine virus selection and in aiding assessment of the pandemic potential of avian and other animal influenza viruses. • The adoption of alternative vaccine technologies - such as live-attenuated, quadrivalent or non-HA-based vaccines - has significant implications for vaccine virus selection, as well as for vaccine regulatory and manufacturing processes. Recent collaboration between the GISRS and vaccine manufacturers has resulted in the increased availability of egg isolates and high-growth reassortants for vaccine production, the development of qualified cell cultures and the investigation of alternative methods of vaccine potency testing. WHO will continue to support these and other efforts to increase the reliability and timeliness of the global influenza vaccine supply. • The WHO GISRS and its partners are continually working to identify improvements, harness new technologies and strengthen and sustain collaboration. WHO will continue in its central role of coordinating worldwide expertise to meet the increasing public health need for influenza vaccines and will support efforts to improve the vaccine virus selection process, including through the convening of periodic international consultations.

Involvement of antibody production quantitative trait loci in the susceptibility to pristane-induced arthritis in the mouse

Mice obtained by bidirectional selective breeding for high (HIII) or low (LIII) antibody (Ab) production are resistant or extremely susceptible to pristane-induced arthritis (PIA), respectively. Several quantitative trait loci regulating Ab production (Ab QTL) have been mapped in these lines, which were used to investigate the influence of these Ab QTL in PIA. Parental HIII and LIII mice and their F1 and F2 intercrosses were injected twice with pristane, and arthritis was observed for 200 days. In LIII mice PIA was more severe and incidence was 100% at day 105, while F1 and F2 mice showed intermediate values. HIII mice were totally resistant. Microsatellite polymorphisms of Ab QTL were analysed and D3Mit100 alleles cosegregated significantly with PIA incidence, severity and onset in F2 intercross mice, while the other four markers showed suggestive values. Results indicate colocalization of QTL for Ab production and PIA susceptibility. Moreover, the different cytokine and IgG isotype profiles observed in HIII and LIII lines after PIA induction are useful to candidate genes endowed with the regulation of the Ab production and arthritis phenotypes.

Mechanistic Analytical Models for Long‐Distance Seed Dispersal by Wind

We introduce an analytical model, the Wald analytical long-distance dispersal (WALD) model, for estimating dispersal kernels of wind-dispersed seeds and their escape probability from the canopy. The model is based on simplifications to well-established three-dimensional Lagrangian stochastic approaches for turbulent scalar transport resulting in a two-parameter Wald (or inverse Gaussian) distribution. Unlike commonly used phenomenological models, WALD's parameters can be estimated from the key factors affecting wind dispersal--wind statistics, seed release height, and seed terminal velocity--determined independently of dispersal data. WALD's asymptotic power-law tail has an exponent of -3/2, a limiting value verified by a meta-analysis for a wide variety of measured dispersal kernels and larger than the exponent of the bivariate Student t-test (2Dt). We tested WALD using three dispersal data sets on forest trees, heathland shrubs, and grassland forbs and compared WALD's performance with that of other analytical mechanistic models (revised versions of the tilted Gaussian Plume model and the advection-diffusion equation), revealing fairest agreement between WALD predictions and measurements. Analytical mechanistic models, such as WALD, combine the advantages of simplicity and mechanistic understanding and are valuable tools for modeling large-scale, long-term plant population dynamics.

Genetic variation of varicella-zoster virus: evidence for geographical separation of strains

Heteroduplex mobility assay was used to identify variants of varicella-zoster virus (VZV) circulating in the United Kingdom and elsewhere. Forty variable positions were identified. Sixteen substitutions were non-synonymous, resulting in an amino acid change, the majority of which were clustered within surface expressed proteins. Phylogenetic analysis distinguished at least three major clades (strains A, B, C) supported by significant bootstrap values. Apart from the United Kingdom and Brazil where all three strains were found, genotypes appeared to be closely associated with the geographical region in which they were sampled. Allelic co-segregation of widely spaced single nucleotide polymorphisms (SNPs) confirmed the genetic stability of the VZV. Recombination rates were difficult to calculate because of the low intra genotypic variation. However, one haplotype originating from Brazil is most parsimoniously explained as a recombinant between A and C strains, which co-occur in the region. Two further UK strains appeared to be recombinants between groups B and C.

The Measles Laboratory Network in the region of the Americas

The success of measles eradication depends upon a laboratory network to rapidly analyze samples obtained as part of surveillance and case investigation. The Pan American Measles Laboratory Network was established in 1995. Major activities of the 22 participating laboratories include the rapid testing of serum samples to diagnose measles, analysis and recommendation of techniques to be used in serologic testing, training in virus isolation, and procurement and distribution of laboratory materials. In addition, a comprehensive quality-control program and an electronic communication network have been developed. Testing for rubella has also been incorporated. The Network has been crucial to the great progress made toward eradicating measles from the Western Hemisphere. The priority given to the laboratories in the Network must continue in order to ensure that the eradication goal is reached and that validation of the interruption of endemic transmission of measles is documented.

Viral respiratory infections in young children attending day care in urban Northeast Brazil

A cohort of children attending a day care center in Salvador (Bahia, Brazil) was studied prospectively to determine the incidence of viral respiratory infectious episodes and to identify the viruses associated with them. Two hundred seventy-one nasopharyngeal samples were collected over a 1-year period for examination, using indirect immunofluorescence with monoclonal antibodies against adenovirus, influenza A and B, parainfluenzae 1-3, and respiratory syncytial virus, and reverse transcriptase-polymerase chain reaction for picornavirus. Examination yielded positive results in 116 samples (42.8%). Rhinovirus was identified alone in 56 samples (48.3%) and was observed along with other viruses in 11 additional samples. Incidence density of viral respiratory infectious episodes was 7.66 episodes/1,000 child-days.

The molecular epidemiology of varicella-zoster virus: evidence for geographic segregation

Of 75 varicella-zoster virus (VZV) isolates obtained from patients in Africa, Asia, and the Far East, 74 (98.6%) were found to be positive for a BglI restriction site in gene 54. By contrast, <22% of strains from patients in the United Kingdom and in North and South America were positive for the BglI restriction site. Viruses positive for BglI were significantly more common in zoster occurring in patients of nonwhite origin (P<.05). Irrespective of the country in which the sample was obtained, 98% of strains positive for BglI clustered within a single phylogenetic group, which we termed "group A"; the exception was 1 strain that appeared to be recombinant genotype C/A. We used the BglI site to examine both the spread of type A viruses in the United Kingdom and the patterns of VZV infections within persons from different ethnic groups who grew up in the United Kingdom or abroad.

Resistance to melanoma metastases in mice selected for high acute inflammatory response

The role of innate immunity in natural resistance to tumor progression was investigated in two mouse lines, AIRmax and AIRmin, selected by bi-directional selective breeding on the basis of high or low acute inflammatory response. Compared with AIRmin, AIRmax mice were shown to be resistant to 7,12-dimethylbenz[a]anthracene (DMBA)/12-O:-tetradecanoylphorbol-13-acetate-induced skin cancers and here we demonstrate that AIRmax are also able to restrain the development of metastases upon transfer of MHC compatible, incompatible or xenogeneic melanomas. An acute inflammatory response to melanoma cells was observed in AIRmax mice only, although both lines were found to mount similar specific immune responses to melanoma antigens. The genetically selected lines therefore represent a model system to analyze the positive correlation between multiple resistance to tumorigenesis and host inflammatory responsiveness.

Pristane-induced arthritis in mice selected for maximal or minimal acute inflammatory reaction

The role of inflammatory and specific immune responses in pristane-induced arthritis (PIA) was investigated in mouse lines produced by bi-directional selective breedings for maximal (AIRmax) or minimal (AIRmin) acute inflammatory reaction, comparing the outcome of PIA and the humoral and cellular response to hsp65. Symptoms of arthritis were detected in 50 % AIRmax mice 120 days after pristane injection, reaching a maximal incidence of 65 %, whereas only 7 % of AIRmin mice developed arthritis within an observation period of 200 days. The production of IgG antibody against hsp65 was found to be similar on both lines, although the IgG1 isotype was predominant in AIRmax, and IgG2a in AIRmin line. In vitro T cell proliferation to hsp65 was similar in the two lines, however, ELISPOT assays carried out soon after pristane treatment, demonstrated higher numbers of IL-6-, TNF-alpha- and IL-4-secreting cells in the spleen of AIRmax than in AIRmin mice, while higher numbers of IFN-gamma-producing cells were found in AIRmin mice. These results suggest a major participation of acute inflammatory mechanisms in the susceptibility to PIA. The genetic background which determines high or low AIR favors a Th2-like response in susceptible AIRmax and Th1-like response in resistant AIRmin mice at the initial phase of arthritis induction.

[Plasma prostaglandin E2 in pregnant women undergoing labor induction with endocervical gel application]

The authors describe an assay that quantify with precision the plasmatic prostaglandin E2 (PGE2). The aim of this study was to evaluate the effect of the gel formulation PGE2 endocervical in the induction of labour. We have studied 26 pregnant women without disease at the term of the pregnancy. The blood sample was collected before and 30 minutes after the labor induction in tubes with 10 mg EDTA Na2 and 5 microg of aspirin. The PGE2 was isolated by extraction and chromatography with 70-100% recovery. The concentration was evaluated by a completion assay with RIA. The PGE2 in plasma was found before and after the induction of labor with the following results: 347 +/- 51.6 and 719 +/- 128 pg/ml. The data was compared by the Student's t test for paired values (df = 50, t = 13. 22 and p < 0.0001). We can conclude that in pregnant women the concentration of PGE2 in plasma was double after the labor induction with the sensitivity in 1.25 pg/tube and the reproducibility 4.6% intraassay and 7% interassay showing that the method is sensitive, reproducible and efficient for the PGE2.

Low antibody responsiveness is found to be associated with resistance to chemical skin tumorigenesis in several lines of Biozzi mice

High and low antibody responder lines of mice from Selections I, III and G were assayed for two-step skin tumorigenesis using a protocol consisting in initiation with 7,12-dimethylbenz[a]anthracene (DMBA) and promotion with 12-O-tetradecanoylphorbol-13-acetate (TPA). Concordant results were obtained in the three selections: low antibody responder mice were shown to be significantly more resistant to tumor induction than the high responder counterparts. The difference was observed for all parameters: kinetics and percentages of tumor incidence and tumor multiplicity. The three bidirectional selective breeding experiments differed in several respects namely, the origin of the foundation populations, the antigens and immunization protocols used during the selection, as well as the breeding unit environments. Therefore, the consistent results relative to tumorigenesis strongly suggest that some of the alleles relevant to multispecific 'low' antibody production could contribute to the resistance to cutaneous chemical tumorigenesis.

Innate resistance to infection by intracellular bacterial pathogens differs in mice selected for maximal or minimal acute inflammatory response

The intensity of nonspecific immune reaction and the host resistance to facultative intracellular pathogens are found to be associated in lines of mice selected for maximal (AIRmax) or minimal (AIRmin) acute inflammatory reactivity. AIRmax are more resistant than AIRmin mice to Salmonella typhimurium and Listeria monocytogenes infection, the differences between lines in LD50 being > 1000 and 100 times, respectively. This difference was shown to be related to the initial bacterial containment at the infectious focus, and to the control of bacterial multiplication in the spleen during the 1st week after s. c. inoculation of the bacteria. Specific immune responses were not deeply affected by the selective process: antibody production and delayed-type hypersensitivity were both of similar intensity in AIRmax and AIRmin mice. The differential susceptibility to infection seems independent of the Nramp-1 locus polymorphism; therefore, these two lines represent a powerful model for investigating the role of other genetic loci regulating the nonspecific immunity effectors in the course of infectious diseases.

Giant osteoblastoma of temporal bone. Case report

Benign osteoblastoma is an uncommon bone tumor accounting for approximately 1% of all bone tumors. There are only 35 cases of skull osteoblastoma reported in the literature. We describe the case of a 23 year old male with a giant osteoblastoma of temporal bone submitted to a total removal of the tumor after an effective embolization of all external carotid branches. The authors discuss diagnostic and management aspects of this uncommon skull tumor.

Effect of genetic modification of acute inflammatory responsiveness on tumorigenesis in the mouse

Two distinct bidirectional selective breedings for quantitative traits were initiated from identical genetically heterogeneous mouse populations. The resulting lines are characterized by maximal or minimal acute inflammatory responsiveness (AIR): AIRmax and AIRmin lines, respectively, and by resistance or susceptibility to chemical skin tumorigenesis: Car-R and Car-S lines, respectively. The AIR response to s.c. injection of polyacrylamide microbeads, measured by cell content in the local exudate, was 10 times higher in AIRmax than in AIRmin mice. The response to selection was asymmetrical: the realized heritability was 0.26 in AIRmax and 0.008 in AIRmin, and resulted from the additive effect of 7-11 quantitative trait loci (QTL). Low responsiveness was globally dominant in F1 and 48% of F2 segregant variance was found to be due to genetic factors. These findings are the first demonstration of innate regulation of AIR by germ line genes. Susceptibility to skin tumorigenesis induced by a two-stage initiation (DMBA)-promotion (TPA) protocol was lower in AIRmax mice than in AIRmin mice, a 6-fold difference in tumor induction rate. Intense AIR was found to be associated with resistance, and low AIR with susceptibility to tumorigenesis, in F2 segregants chosen for extreme AIR phenotypes. At least some of the AIR QTLs therefore contain genes controlling tumorigenesis. Tumor phenotypes differed more in Car-R and Car-S than in AIRmax and AIRmin lines, indicating that QTLs unrelated to AIR, contribute to the host response to tumorigenesis. The extreme phenotypes/genotypes of the four selected lines and the known genetic constitution of their foundation population, offer new possibilities to discriminate the genes/mechanisms controlling two important traits: AIR and response to chemical tumorigenesis. Collaborative projects will be favorably considered. The description of tumor resistance genes in AIRmax and Car-R mice may be helpful for epidemiology and therapy of human cancer.

Polygenic control of antibody production and correlation with vaccine induced resistance to rabies virus in high and low antibody responder mice

The amplification of "high" (H) and "low" (L) multispecific antibody responses achieved respectively by H and L lines of selection GP represents a valuable tool in the genetic study of host-infection interactions. These lines were obtained by bidirectional selective breeding for high (HGP) or low (LGP) antibody production to natural complex antigens. HGP and LGP parental lines and reciprocal F1 hybrids, as well as their F2 segregants and backcrosses were submitted to immunization and challenge with rabies virus CVS strain. Acquired resistance was 1000-fold higher in HGP than LGP mice, with a dominance effect to low antibody production observed in F1 hybrids. An association between high antibody response and acquired resistance (P < 0.001) in F2 segregant mice was noticed. The genetic study was performed in these several populations, with a single dose of 104.5-fold LD50 CVS. We could demonstrate 3 independent loci regulating the anti-rabies antibody production, that are distinct, at least in part, from the 10 genes controlling the antigen selection response (sheep erythrocytes) of selection GP.

Sinus skeletonization: a treatment for dural arteriovenous malformations of the tentorial apex. Report of two cases

Two cases of dural arteriovenous malformation of the tentorial apex are presented. Both were treated surgically by means of a sinus skeletonization technique. The operative technique included a combined bioccipital and median suboccipital craniotomy in which the posterior third of the superior sagittal and the straight and bilateral transverse sinuses were skeletonized by incising the falx and the tentorium along the sinuses. Endovascular embolization was used prior to the surgical approach in one case. Clinical and angiographic cure was achieved in both patients, with a follow up of 4 years in the first case and 1 year in the second one. The surgical technique is described in detail.

Reduced humoral immunity in uremic mice genetically selected for high antibody response

Biozzi's Selection IV-A mice, genetically selected for 25 generations for high and low antibody response to sheep red blood cells (SRBC), 2-3 months old, were made uremic by subtotal nephrectomy and characterized for antibody production against the selection antigen. T cell activity was evaluated in vitro by lymphocyte proliferation and interleukin 2 (IL 2) production in response to the super antigen staphylococcal enterotoxin B (SEB). Total and IgM antibody titers (log2) were similar in uremic and non-uremic low responder mice (total antibody: 4.0 +/- 0.6 vs 3.6 +/- 0.6; IgG: 3.0 +/- 0.7 vs 2.4 +/- 0.4), while uremic high responders presented with non-uremic animals (total antibody: 10.8 +/- 1.6 vs 13.0 +/- 0.2; IgG: 10.3 +/- 1.5 vs 11.7 +/- 0.3). T cell proliferation and IL 2 production were similar in uremic and non-uremic groups after SEB stimulation. The results indicate a genetic effect on sensitivity to humoral immune response modulation by uremic status, with deficient antibody production despite a normal T cell proliferative response to mitogen stimulation in short-duration renal failure in high responder mice.

Specific and non-specific T-cell activation in high and low antibody-producing mice (selection IV-A)

The T-cell regulatory function has been evaluated in lines of mice genetically selected according to the High (H) and Low (L) antibody responsiveness to heterologous erythrocytes. The inhibition of antibody production following CD4+ subset depletion was stronger in L than in H mice. The dose of CD4-specific monoclonal antibody (MoAb) needed for a 50% inhibition of the anti-sheep erythrocyte antibody response was much lower in L mice, even when their responsiveness was improved by repeated antigen injections or by co-injection of lipopolysaccharide as an adjuvant. Lymph-node cells from L mice responded normally or even better than those from H mice to in vitro non-specific triggering via lectins, exogenous superantigens or CD3-specific MoAb. In contrast, the antigen-specific responses of the lymph-node cells from protein-primed mice were consistently lower in the Low responder mice. Altogether the results suggest that a defective stimulation of T helper lymphocytes by the antigen contributes to the weak antibody response of L mice.