Malaria infections do not compromise vaccine-induced immunity against tuberculosis in mice

The Effect of Malaria on Responses to Unrelated Vaccines in Animals and Humans: A Systematic Review and Meta-Analysis

Vaccine efficacy varies globally, often showing reduced immune responses in low- and middle-income countries, possibly due to the immunomodulatory effects of parasitic infections like malaria. This systematic review evaluates the impact of malaria on immune responses to unrelated vaccines in humans and animals. We systematically searched five databases-MEDLINE, Web of Science, Global Health, Scopus and Embase-up to 5th December 2023. Eligible studies compared immune responses to WHO-approved vaccines between malaria-infected and uninfected groups, or between antimalarial-treated and untreated groups. Meta-analysis was performed using random-effects models with standardised mean differences (SMDs) as summary statistics. The study is registered with PROSPERO (CRD42022298053). Twenty-four articles (17 human, 7 animal) met the inclusion criteria, with 13 human articles contributing data for the meta-analysis. Significant heterogeneity was observed. Vaccine responses were higher in malaria uninfected individuals (SMD 0.34, 95% CI 0.07 to 0.60, I2 = 87.15%) with weaker differences between antimalarial-treated and untreated groups (SMD 0.07, 95% CI -0.01 to 0.16, I2 = 85.01%). The overall SMD for malaria uninfected/treated vs. infected/untreated was 0.15, 95% CI 0.05-0.26, I2 = 90.91. Narrative analysis suggested malaria's adverse impact on vaccine responses in animals. Malaria infection may impair vaccines responses; with preventive treatment of malaria partially reversing these effects, highlighting the need for targeted public health interventions.

Protozoan co-infections and parasite influence on the efficacy of vaccines against bacterial and viral pathogens

A wide range of protozoan pathogens either transmitted by vectors (Plasmodium, Babesia, Leishmania and Trypanosoma), by contaminated food or water (Entamoeba and Giardia), or by sexual contact (Trichomonas) invade various organs in the body and cause prominent human diseases, such as malaria, babesiosis, leishmaniasis, trypanosomiasis, diarrhea, and trichomoniasis. Humans are frequently exposed to multiple pathogens simultaneously, or sequentially in the high-incidence regions to result in co-infections. Consequently, synergistic or antagonistic pathogenic effects could occur between microbes that also influences overall host responses and severity of diseases. The co-infecting organisms can also follow independent trajectory. In either case, co-infections change host and pathogen metabolic microenvironments, compromise the host immune status, and affect microbial pathogenicity to influence tissue colonization. Immunomodulation by protozoa often adversely affects cellular and humoral immune responses against co-infecting bacterial pathogens and promotes bacterial persistence, and result in more severe disease symptoms. Although co-infections by protozoa and viruses also occur in humans, extensive studies are not yet conducted probably because of limited animal model systems available that can be used for both groups of pathogens. Immunosuppressive effects of protozoan infections can also attenuate vaccines efficacy, weaken immunological memory development, and thus attenuate protection against co-infecting pathogens. Due to increasing occurrence of parasitic infections, roles of acute to chronic protozoan infection on immunological changes need extensive investigations to improve understanding of the mechanistic details of specific immune responses alteration. In fact, this phenomenon should be seriously considered as one cause of breakthrough infections after vaccination against both bacterial and viral pathogens, and for the emergence of drug-resistant bacterial strains. Such studies would facilitate development and implementation of effective vaccination and treatment regimens to prevent or significantly reduce breakthrough infections.

BCG-mediated protection against M. tuberculosis is sustained post-malaria infection independent of parasite virulence

Tuberculosis (TB) and malaria remain serious threats to global health. Bacillus Calmette-Guerin (BCG), the only licensed vaccine against TB protects against severe disseminated forms of TB in infants but shows poor efficacy against pulmonary TB in adults. Co-infections have been reported as one of the factors implicated in vaccine inefficacy. Given the geographical overlap of malaria and TB in areas where BCG vaccination is routinely administered, we hypothesized that virulence-dependent co-infection with Plasmodium species could alter the BCG-specific immune responses thus resulting in failure to protect against Mycobacterium tuberculosis. We compared virulent Plasmodium berghei and non-virulent Plasmodium chabaudi, their effects on B cells, effector and memory T cells, and the outcome on BCG-induced efficacy against M. tuberculosis infection. We demonstrate that malaria co-infection modulates both B- and T-cell immune responses but does not significantly alter the ability of the BCG vaccine to inhibit the growth of M. tuberculosis irrespective of parasite virulence. This malaria-driven immune regulation may have serious consequences in the early clinical trials of novel vaccines, which rely on vaccine-specific T-cell responses to screen novel vaccines for progression to the more costly vaccine efficacy trials.

TACI Contributes to Plasmodium yoelii Host Resistance by Controlling T Follicular Helper Cell Response and Germinal Center Formation

The delay in parasite-specific B cell development leaves people in malaria endemic areas vulnerable to repeated Plasmodium infections. Here, we investigated the role of transmembrane activator and calcium-modulator and cyclophilin ligand interactor (TACI), a molecule involved in the generation of antigen-specific antibody secreting cells, in host response to non-lethal Plasmodium yoelii infection. We found that TACI deficiency not only resulted in higher peak parasitemia levels in P. yoelii challenged mice, but also led to a delay in parasite clearance and anti-P. yoelii Merozoite Surface Protein 1(C-terminal 19-kDa fragment [rMSP-1₁₉]) protein and anti-rMSP-1₁₉ and anti-P. yoelii IgG antibody development. There was also a delay in the generation of splenic high affinity antibody secreting cells that recognize rMSP-1₁₉ protein as compared to wild-type mice. Interestingly, coinciding with the delay in parasite clearance there was a delay in the resolution of T follicular helper (T_FH) cell and germinal center (GC) B cell responses in TACI -/- mice. The persistence of T_FH and GC B cells is likely a result of enhanced interaction between T_FH and GC B cells because inducible costimulator ligand (ICOSL) expression was significantly higher on TACI -/- GC B cells than wild-type cells. The difference in the kinetics of GC reaction appeared to also impact the emergence of plasma cells (PC) because there was a delay in the generation of TACI -/- mice PC. Nevertheless, following the recovery from P. yoelii infection, TACI -/- and wild-type mice were both protected from a rechallenge infection. Establishment of protective B cell response was responsible for the resolution of parasitemia because B cells purified from recovered TACI -/- or wild-type mice were equally protective when introduced to naïve wild-type mice prior to P. yoelii challenge. Thus, despite the increased susceptibility of TACI -/- mice to P. yoelii infection and a delay in the development of protective antibody levels, TACI -/- mice are able to clear the infection and resist rechallenge infection.

Draft sequencing and assembly of the genome of the world's largest fish, the whale shark: Rhincodon typus Smith 1828

BACKGROUND

The whale shark (Rhincodon typus) has by far the largest body size of any elasmobranch (shark or ray) species. Therefore, it is also the largest extant species of the paraphyletic assemblage commonly referred to as fishes. As both a phenotypic extreme and a member of the group Chondrichthyes - the sister group to the remaining gnathostomes, which includes all tetrapods and therefore also humans - its genome is of substantial comparative interest. Whale sharks are also listed as an endangered species on the International Union for Conservation of Nature's Red List of threatened species and are of growing popularity as both a target of ecotourism and as a charismatic conservation ambassador for the pelagic ecosystem. A genome map for this species would aid in defining effective conservation units and understanding global population structure.

RESULTS

We characterised the nuclear genome of the whale shark using next generation sequencing (454, Illumina) and de novo assembly and annotation methods, based on material collected from the Georgia Aquarium. The data set consisted of 878,654,233 reads, which yielded a draft assembly of 1,213,200 contigs and 997,976 scaffolds. The estimated genome size was 3.44Gb. As expected, the proteome of the whale shark was most closely related to the only other complete genome of a cartilaginous fish, the holocephalan elephant shark. The whale shark contained a novel Toll-like-receptor (TLR) protein with sequence similarity to both the TLR4 and TLR13 proteins of mammals and TLR21 of teleosts. The data are publicly available on GenBank, FigShare, and from the NCBI Short Read Archive under accession number SRP044374.

CONCLUSIONS

This represents the first shotgun elasmobranch genome and will aid studies of molecular systematics, biogeography, genetic differentiation, and conservation genetics in this and other shark species, as well as providing comparative data for studies of evolutionary biology and immunology across the jawed vertebrate lineages.

Tuberculosis arthritis of the sternoclavicular joint after uncomplicated falciparum malaria: a case report

Background

Malaria and tuberculosis are co-endemic in many developing countries. However their associations are rarely reported. Yet, it has been suggested that a pathological process may link the two diseases.

Case presentation

A 20-year-old female patient was admitted in the internal medicine service of Aristide Le Dantec Hospital for uncomplicated malaria. She was previously treated for autoimmune hemolytic anaemia using prednisone at 5 mg per day. Clinical examination showed swelling in front of the sternoclavicular joint. She presented with fever and headache. Thick smear from blood revealed trophozoites of P. falciparum at parasite density of 52,300 parasites/μl. The Ziehl–Neelsen stained smear showed the presence of acid-fast bacilli from the fluid puncture of the swelling. Mycobacterium tuberculosis was further isolated in culture. The diagnosis of falciparum malaria co-infection with sternoclavicular tuberculosis was posed. The patient was treated successfully using antimalarial drugs subsequently followed by multidrug antitubercular therapy.

Conclusion

Interactions between malaria and tuberculosis need to be largely and prospectively investigated and appropriate treatment should be undertaken.

Tuberculosis Comorbidity with Communicable and Noncommunicable Diseases

The 18th WHO Global Tuberculosis Annual Report indicates that there were an estimated 8.6 million incident cases of tuberculosis (TB) in 2012, which included 2.9 million women and 530,000 children. TB caused 1.3 million deaths including 320,000 human immunodeficiency virus (HIV)-infected people; three-quarters of deaths occurred in Africa and Southeast Asia. With one-third of the world's population latently infected with Mycobacterium tuberculosis (Mtb), active TB disease is primarily associated with a break down in immune surveillance. This explains the strong link between active TB disease and other communicable diseases (CDs) or noncommunicable diseases (NCDs) that exert a toll on the immune system. Comorbid NCD risk factors include diabetes, smoking, malnutrition, and chronic lung disease, all of which have increased relentlessly over the past decade in developing countries. The huge overlap between killer infections such as TB, HIV, malaria, and severe viral infections with NCDs, results in a "double burden of disease" in developing countries. The current focus on vertical disease programs fails to recognize comorbidities or to encourage joint management approaches. This review highlights major disease overlaps and discusses the rationale for better integration of tuberculosis care with services for NCDs and other infectious diseases to enhance the overall efficiency of the public health responses.

Cholera toxin enhances vaccine-induced protection against Mycobacterium tuberculosis challenge in mice

Interleukin (IL)-17 is emerging as an important cytokine in vaccine-induced protection against tuberculosis disease in animal models. Here we show that compared to parenteral delivery, BCG delivered mucosally enhances cytokine production, including interferon gamma and IL-17, in the lungs. Furthermore, we find that cholera toxin, delivered mucosally along with BCG, further enhances IL-17 production by CD4(+) T cells over mucosal BCG alone both in the lungs and systemically. This boosting effect of CT is also observed using a vaccine regimen of BCG followed by the candidate vaccine MVA85A. Using a murine Mycobacterium tuberculosis (M.tb) aerosol challenge model, we demonstrate the ability of cholera toxin delivered at the time of a priming BCG vaccination to improve protection against tuberculosis disease in a manner at least partially dependent on the observed increase in IL-17. This observed increase in IL-17 in the lungs has no adverse effect on lung pathology following M.tb challenge, indicating that IL-17 can safely be boosted in murine lungs in a vaccine/M.tb challenge setting.

Co-infection of tuberculosis and parasitic diseases in humans: a systematic review

Co-infection of tuberculosis and parasitic diseases in humans is an important public problem in co-endemic areas in developing countries. However, there is a paucity of studies on co-infection and even fewer reviews. This review examines 44 appropriate papers by PRISMA from 289 papers searched in PubMed via the NCBI Entrez system (no grey literature) up to December 2012 in order to analyze the factors that influence epidemic and host’s immunity of co-infection. The limited evidence in this review indicates that most common parasite species are concurrent with Mycobacterium tuberculosis in multiple organs; socio-demographics such as gender and age, special populations with susceptibility such as renal transplant recipients, patients on maintenance haemodialysis, HIV positive patients and migrants, and living in or coming from co-endemic areas are all likely to have an impact on co-infection. Pulmonary tuberculosis and parasitic diseases were shown to be risk factors for each other. Co-infection may significantly inhibit the host’s immune system, increase antibacterial therapy intolerance and be detrimental to the prognosis of the disease; in addition, infection with parasitic diseases can alter the protective immune response to Bacillus Calmette-Guerin vaccination against Mycobacterium tuberculosis.